WO2016178957A1 - Electrochemical hydrogen storage electrodes and cells - Google Patents

Electrochemical hydrogen storage electrodes and cells Download PDF

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Publication number
WO2016178957A1
WO2016178957A1 PCT/US2016/029980 US2016029980W WO2016178957A1 WO 2016178957 A1 WO2016178957 A1 WO 2016178957A1 US 2016029980 W US2016029980 W US 2016029980W WO 2016178957 A1 WO2016178957 A1 WO 2016178957A1
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acid
methylimidazolium
ethyl
bis
butyl
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French (fr)
Inventor
Kwo Young
Tiejun MENG
Michael A. Fetcenko
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BASF Corp
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BASF Corp
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Priority to EP16789811.3A priority Critical patent/EP3292578B1/en
Priority to CN201680025955.XA priority patent/CN107710462B/en
Priority to JP2017557401A priority patent/JP7097700B2/en
Priority to KR1020177031695A priority patent/KR102602374B1/en
Publication of WO2016178957A1 publication Critical patent/WO2016178957A1/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/383—Hydrogen absorbing alloys
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen; Reversible storage of hydrogen
    • C01B3/0005—Reversible storage of hydrogen, e.g. by hydrogen getters or electrodes
    • C01B3/001—Reversible storage of hydrogen, e.g. by hydrogen getters or electrodes characterised by the uptaking media; Treatment thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen; Reversible storage of hydrogen
    • C01B3/0005—Reversible storage of hydrogen, e.g. by hydrogen getters or electrodes
    • C01B3/001—Reversible storage of hydrogen, e.g. by hydrogen getters or electrodes characterised by the uptaking media; Treatment thereof
    • C01B3/0018—Inorganic elements or compounds, e.g. oxides, nitrides, borohydrides or zeolites; Solutions thereof
    • C01B3/0021—Elemental carbon, e.g. active carbon, carbon nanotubes or fullerenes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen; Reversible storage of hydrogen
    • C01B3/0005—Reversible storage of hydrogen, e.g. by hydrogen getters or electrodes
    • C01B3/001—Reversible storage of hydrogen, e.g. by hydrogen getters or electrodes characterised by the uptaking media; Treatment thereof
    • C01B3/0018—Inorganic elements or compounds, e.g. oxides, nitrides, borohydrides or zeolites; Solutions thereof
    • C01B3/0031—Intermetallic compounds; Metal alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/34—Gastight accumulators
    • H01M10/345—Gastight metal hydride accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/24—Electrodes for alkaline accumulators
    • H01M4/242—Hydrogen storage electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0002—Aqueous electrolytes
    • H01M2300/0005—Acid electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0045—Room temperature molten salts comprising at least one organic ion
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/32—Hydrogen storage

Definitions

  • Electrochemical Hydrogen Storage Electrodes and Cells The invention relates to electrochemical hydrogen storage electrodes, electrochemicai hydrogen storage materials and electrochemical cells.
  • Rechargeable metal hydride (MH) electrochemical cells are employed in numerous applications such as portable computers, phones, industrial applications, aerospace applications and electric vehicles.
  • the negative electrode (anode) of a metal hydride electrochemical ceil may comprise an AB5, AB 2 , A 2 B 7 -type, Ti-Ni-based, Mg-Ni-based, BCC or Zr-Ni-based metal hydride alloy.
  • the metal alloys are hydrogen storage alloys.
  • Conventional AB5 and A2B7 alloys have capacities of from about 320 to about 360 mAh/g and are of relatively high weight. Desired are rechargeable electrochemical ceils having lighter weight, higher capacity and higher gravimetric energy density.
  • a negative electrode comprising a hydrogen storage material based on one or more group IV elements is highly effective as a hydrogen charge/discharge component in an electrochemical cell.
  • the hydrogen storage material is for example based on silicon and/or carbon.
  • a stable group IV element-based, e.g. stable silicon-based hydrogen storage negative eiectrode for electrochemical uses may for instance be in contact with a non-aqueous electrolyte composition and/or comprises a solid electrolyte interface (SEI) capable of allowing proton transport.
  • SEI solid electrolyte interface
  • the SEI provides corrosion resistance for the electrode and may also serve as an electrochemical catalyst. The durability and functionality of the SEI layer are very important for the operation of a rechargeable
  • electrochemical ceil battery
  • the typical SEI on the anode made from conventional hydrogen storage alloy contains oxide, hydroxide, metallic inclusion, amorphous oxide/metal buffer, voids and channels.
  • An electrochemical cell comprising a stable group IV element-based, e.g. stable silicon-based hydrogen storage negative electrode and an aqueous or non-aqueous electrolyte composition in contact with the electrode, for example the electrolyte composition is neutral or acidic, where the electrolyte composition has a pH of about 7 or less.
  • An electrochemical cell comprising a hydrogen storage negative electrode, a positive electrode and an electrolyte composition in contact with the electrodes, where the reversible half cell charge/discharge electrochemical reaction at the negative electrode is
  • /V and Si are a stable group IV element-based and a stable silicon-based hydrogen storage material, respectively.
  • a hydrogen storage negative electrode for electrochemical uses, where the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 charge/discharge cycles.
  • An electrochemical cell comprising a hydrogen storage negative electrode, a positive electrode and an electrolyte composition in contact with the electrodes, where the cell exhibits a gravimetric energy density of > 100 Wh/kg and/or a volumetric energy density of > 250 Wh/L.
  • Modifying elements and/or compounds may be employed to alter the physical (density, porosity, melting temperature, etc.), chemical (alloy heat of formation, hydride heat of formation, electron coherent energy, hydrogen bond strength, nature of hydrogen bond, etc) and electrochemical properties (capacity, rate capability, charge-retention, cycle stability, corrosion resistance, etc.) of the anode, in the case of group IV element-based hydrogen storage anode materials
  • suitable modifying elements include 1.
  • H-bond strength modifiers elements to adjust the voltage of the ceil, such as alkaline earth metals, transition metals, rare earth metals, and other metals from groups 111 and V of the periodic table; and 3.
  • SE! modifiers elements to prolong the cycle stability and reduce the temperature sensitivity of the SEI layer, including non- metal elements such as O, F, P, CI, etc.
  • the hydrogen storage electrodes are useful in electrochemical cells.
  • the cells comprise an electrolyte composition that is for example nonaqueous or is aqueous with a pH of about 7 or less. In present electrochemical cells, it is believed that the reversible half cell electrochemical reaction at the negative electrode is
  • IV is a hydrogen storage material based on one or more group IV elements
  • Si is a silicon-based hydrogen storage material
  • the negative electrode in a charged state, the negative electrode is reduced and contains stored hydrogen while the positive electrode is oxidized.
  • protons exit the negative electrode (anode) and migrate through the electrolyte composition to the positive electrode (cathode) while their associated electrons exit the anode via external circuitry.
  • the present cells are rechargeable and during charge/discharge cycles the negative electrode reversibly charges and discharges hydrogen as does a nickel metal hydride anode in a metal hydride ceil, although possibly not via an identical mechanism, A present
  • electrochemical ceil may be considered a "hydride battery” or a “non-metal hydride battery” or a “rechargeable proton battery”.
  • the hydrogen storage negative electrode comprises a hydrogen storage material based on one or more group IV elements, for example based on silicon.
  • the hydrogen storage material is capable of reversibly charging and discharging hydrogen during cycling of an electrochemical cell.
  • the mechanism of charging hydrogen may be intercalation of protons.
  • hydrogen storage means capable of reversibly charging and discharging hydrogen during cycling of an electrochemical cell.
  • the term “based on” or “-based” means that the hydrogen storage material comprises greater than 27 wt% of one or more group IV elements, based on the total weight of the hydrogen storage material. "Silicon-based” means that the hydrogen storage material contains > 27 wt% of Si, based on the total weight of the hydrogen storage material.
  • Group IV elements include silicon, carbon, germanium and tin.
  • Group IV is also known as the carbon group or group 14 of the periodic table.
  • the hydrogen storage material contains > 28 wt%, > 29 wt%, > 30 wt%, > 33 wt%, > 35 wt%, > 40 wt%, > 45 wt%, > 50 wt%, > 55 wt%, > 60 wt%, > 65 wt%, > 70 wt%, > 75 wt%, > 80 wt%, > 85 wt%, > 90 wt%, > 95 wt%, > 96 wt%, > 97 wt%, > 98 wt% or > 99 wt% of one or more elements selected from the group consisting of group IV elements, for example Si and/or carbon, based on the hydrogen storage material.
  • group IV elements for example Si and/or carbon
  • stable means that the anode exhibits ⁇ 10% capacity degradation over 100 charge/discharge cycles of an electrochemical cell. For instance, the anode may exhibit ⁇ 9%, ⁇ 8%, ⁇ 7%, ⁇ 6%, ⁇ 5% or ⁇ 4% capacity degradation over 100 charge/discharge cycles.
  • Percent capacity degradation at certain charge/discharge rates over 100 cycles is defined as [(capH - cap L )/cap H ] ⁇ 100 where cap H is the highest value of discharge capacity and cap L is the lowest value of discharge capacity.
  • a typical half-cell cycling schema is with a C/5 charge rate for 1 10% state-of-charge (5.5 h) and discharge at C/5 rate to a cut-off voltage of 0.9 V vs. a standard Ni(OH) 2 /NiOOH or -0.5 V vs. a Hg/HgO refrence electrode.
  • the anode may consist of or consist essentially of the hydrogen storage material or, alternatively, the anode may comprise the hydrogen storage material and a substrate.
  • the hydrogen storage material may be adsorbed on a substrate such as a metal, glass, plastic or inorganic substrate.
  • Inorganic substrate includes graphite.
  • the hydrogen storage material may comprise silicon. Silicon may be any suitable material.
  • Amorphous silicon may be deposited as a thin film onto a substrate via chemical vapor deposition (CVD) techniques, for example via plasma enhanced chemical vapor deposition techniques (PECVD).
  • CVD chemical vapor deposition
  • PECVD plasma enhanced chemical vapor deposition techniques
  • Silicon may be hydrogenated to prepare hydrogenated silicon prior to or after preparation of the anode.
  • amorphous silicon may be hydrogenated to prepare a-Si: H prior to or after preparation of the anode.
  • the anode may be hydrogenated prior to preparation of an electrochemical device.
  • hydrogenated amorphous Si (a-Si:H) thin films may be prepared by chemical vapor deposition.
  • An a-Si:H thin film may be prepared via rf-sputtering deposition of a-Si followed by hydrogenation.
  • the hydrogen storage material may comprise doped silicon or doped hydrogenated silicon, for example P-type silicon or hydrogenated P-fype silicon.
  • P-type silicon is for example silicon doped with Al. Suitable also for instance is silicon or hydrogenated silicon doped with phosphine or boron.
  • the hydrogen storage material is doped hydrogenated amorphous silicon (doped a-Si:H).
  • Suitable a-Si film thickness is for instance > 20 nm, > 50 nm, > 90 nm, > 120 nm or > 180 nm.
  • a suitable a-Si film thickness is from about 90 nm to about 10 ⁇ , from about 100 nm to about 5 ⁇ , from about 150 nm to about 3 ⁇ , from about 150 nm to about 2 pm or from about 150 nm to about 1 ⁇ .
  • Silicon may be microcrystalline silicon or nanocrystalline silicon, which generally are forms of amorphous silicon containing small silicon crystals. Silicon may also be mono-crystalline silicon, poiycrystalline or protocrystailine. Silicon may be porous silicon (p-Si). Types of porous silicon include microporous, mesoporous and macroporous, with average pore sizes of less than aboui 2 nm, from about 2 nm to about 50 nm and greater than about 50 nm, respectively.
  • the hydrogen storage material may contain one or more different forms of silicon.
  • the hydrogen storage materials include alloys of silicon, for example alloys of silicon with one or more of carbon, germanium and tin.
  • alloys of silicon for instance alloys of silicon with one or more of carbon, germanium and tin.
  • amorphous alloys of silicon and carbon amorphous silicon carbide
  • Amorphous alloys of silicon and carbon can also be hydrogenated to prepare a-Sii -x C x :H where x is for example from about 0.01 to about 0.99, from about 0.05 to about 0.95 or from about 0.1 to about 0.9.
  • hydrogen storage materials of the invention may also be hydrogenated prior to preparation of an electrochemical device.
  • Hydrogenation is performed for instance under hydrogen gas at a pressure greater than atmospheric. Hydrogen pressure is for instance from about 2 atm to about 20 aim. Hydrogenation may be performed at increased temperature, for instance from about 25°C to about 500°C. Hydrogenation may be performed e!ectrochemically.
  • Hydrogen storage materials inciude carbon and graphitic materials such as natural graphite, artificial graphite, expanded graphite, graphene, carbon fiber, soft carbon, hard carbon, non-graphitizable carbon, carbon black, carbon nanotube, fulierene, activated carbon, crystalline carbon and amorphous carbon.
  • the hydrogen storage materials may include one or more further elements, for instance one or more further elements selected from the group consisting of structural modifiers
  • Structural modifiers include for example B.
  • Hyrogen bond modifiers inciude for example alkaline earth metals, transition metals, rare earth metals and other metals of groups 111 and V of the periodic table.
  • SEi modifiers inciude non-metals such as O, F, P, Ci and the like.
  • the anode may further inciude binders and/or conductive materials and/or other additives.
  • the anode assemblies may include these mixtures in adherence to a current collector such as a metal foil substrate.
  • Binders include poiy(tetrafluoroethylene) (PTFE), a copolymer of acrylonitrile and butadiene (NBR), polyvinylidene fluoride (PvDF), polyvinyl alcohol, carboxy methyl cellulose (CMC), starch, hydroxy propyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene- propylene-diene polymer (EPDM), sulfonated-EPD , styrene-butadiene rubber (SBR), fluorine rubber, copolymers thereof and mixtures thereof. Binders may be employed from about 1 to about 50 weight %, based on the total weight of electrode assembly.
  • Conductive materials may be from about 1 to about 20 weight %, based on the total weight of the electrode assembly.
  • Conductive materials include graphitic materials such as natural graphite, artificial graphite, a carbon black such as acetylene black, Ketjen black, channel black, furnace black or lamp black, conductive fibers such as carbon fiber or metal fiber, metal powders such as carbon fluoride, aluminum or nickel powder, conductive metal oxides such as zinc oxide, potassium titanate or titan oxide and other conductive materials such as
  • a filler may be employed as a component for controlling expansion of the anode.
  • Fillers include oiefin-based polymers such as polyethylene or polypropylene and fibrous material such as glass fiber or carbon fiber.
  • the negative electrode may advantageously comprise > 30% by weight of the one or more group IV elements; for example > 35%, > 40%, > 45%, > 50%, > 55%, > 60%, > 65%, > 70%, > 75% > 80%, > 85% or > 90% by weight of the one or more group IV elements, based on the total weight of the negative electrode (total weight of the electrode assembly).
  • the total weight of the negative electrode includes the hydrogen storage material and optional components such as substrate, binders, conductive materials and additives.
  • a separator is typically interposed between the cathode and the anode which is for instance an insulating thin film ensuring high ion (proton) transmission.
  • the separator generally has a pore size of about 0.01 to about 10 microns and a thickness of about 5 to about 300 microns.
  • Separator materials include sheets or non-woven fabrics comprising materials including glass fiber, cotton, nylon, polyester, polyethylene, polypropylene, polyvinyl chloride,
  • the active materials of the positive electrode participate in the charge/discharge reactions.
  • Suitable active materials include nickel hydroxide active materials, i.e. nickel hydroxide or modified nickel hydroxide.
  • the cathode materials may comprise a multi-phase disordered nickel hydroxide material having at least one modifier.
  • the at least one modifier is for instance a metal, a metallic oxide, a metallic oxide alloy, a metal hydride and/or a metal hydride alloy.
  • the modifier is one or more components selected from the group consisting of Al, Ba, Ca, F, K, Li, Mg, Na, Sr, Bi, Co, Cr, Cu, Fe, in, LaH 3 , Mn, Ru, Sb, Sn, TiH 2 , TiO, and Zn.
  • Such materials are taught in U.S. Pat. No. 5,348,822.
  • Suitable cathode materials may comprise a disordered multi-phase nickel hydroxide matrix including at least one modifier, for example 3 modifiers, chosen from F, Li, Na, K, Mg, Ba, Ln, Se, Nd, Pr, Y, Co, Zn, Ai, Cr, Mn, Fe, Cu, Zn, Sc, Sn, Sb, Te, Bi, Ru and Pb.
  • Suitable cathode materials are taught for example in U.S. Pat. No. 5,637,423.
  • Cathode materials may comprise nickel hydroxide modified with one or more group ⁇ elements and Co in a solid solution state. Such materials are taught in U.S. Pat. No. 5,366,831.
  • the cathode active materials may comprise nickel hydroxide and one or more components selected from the group consisting of cobalt, cobalt hydroxide and cobalt oxide and a carbon powder.
  • the cathode materials may further comprise a compound of Ca, Sr, Ba, Cu, Ag or Y, for example Ca(OH) 2 , CaO, CaF 2 , CaS, CaS0 4 , CaSi 2 0 5 , CaC 2 0 4 , CaW0 4 , SrC0 3l Sr(OH) 2 , BaO, Cu 2 0, Ag 2 Q, Y 2 (C0 3 )3 or Y 2 G 3 .
  • Suitable cathode materials are taught for instance in U.S. Pat. No. 5,451 ,475.
  • Cathode active materials may comprise a metal oxide and one or more of Co, Ca, Ag, Mn, Zn, V, Sb, Cd, Y, Sr, Ba and oxides of Ca, Sr, Ba, Sb, Y or Zn.
  • the metal oxide is for example nickel oxide and or manganese oxide.
  • the cathode materials may contain nickel hydroxide and a further component selected from the group consisting of Y, In, Sb, Ba and Be and Co and/or Ca. Such materials are disclosed in U.S. Pat. No. 5,466,543.
  • Cathode materials may be prepared by reacting nickel sulfate and ammonium hydroxide to form a nickel ammonium complex; the complex is then reacted with sodium hydroxide to form nickel hydroxide.
  • the method may provide nickel hydroxide comprising one or more of Co, Zn and Cd.
  • Cathode active materials may comprise nickel hydroxide and cobalt oxyhydroxide as taught in U.S. Pat. No. 5,489,314.
  • Cathode materials may comprise nickel hydroxide, cobalt monoxide and elemental zinc as taught in U.S. Pat. No. 5,506,070.
  • the cathode materials may comprise nickel hydroxide, nickel powder, a second powder and at least one of cobalt, cobalt hydroxide and cobalt oxide.
  • the second powder contains one or more of Ca, Sr, Ba, Cu, Ag and Y. Such materials are taught in U.S. Pat. No. 5,571 ,636.
  • the cathode active materials may comprise particles of nickel hydroxide or manganese hydroxide having at least partially embedded therein a conductive material.
  • the conductive material may be for instance nickel, nickel alloys, copper, copper alloys; metal oxides, nitrides, carbides, siiicides or borides; or carbon (graphite). These materials are disclosed in U.S. Pat. No. 6,177,213.
  • the cathode materials may comprise nickel hydroxide particles containing at least three modifiers selected from the group consisting of Ai, Bi, Ca, Co, Cr, Cu, Fe, In, La, rare earths, g, Mn, Ru, Sb, Sn, Ti, Ba, Si, Sr and Zn.
  • nickel hydroxide particles may contain at least four modifiers, for instance, Ca, Co, Mg and Zn. Such materials are disclosed in U.S. Pat. No. 6,228,535.
  • the active cathode material for instance comprises nickel hydroxide and a carbon material such as graphite.
  • the cathode may also comprise a polymeric binder.
  • the polymeric binder is for example a thermoplastic organic polymer, for instance selected from the group consisting of polyvinyl alcohol (PVA), polyethylene oxide, polypropylene oxide, polybutyiene oxide, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose,
  • hydroxypropylmethyi cellulose polyethylene, polypropylene, polyisobutyiene, polyvinyl chloride, polyvinyliden chloride, polyvinyliden fluoride, polytetrafluoroethyiene (PTFE), fluorinated ethylene propylene (FEP), perfluroalkoxy (PFA), polyvinylacetate, polyvinyl isobutylether, polyacrylonitrile, polymethacrylonitrile, polymethylmethacrylate, po!ymethylacry!ate,
  • poiyethy!methacry!ate ally! acetate, polystyrene, polybutadiene, polyisoprene,
  • the polymeric binder may also be an elastomer or rubber such as styrene-butadiene copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethyiene-styrene- butadiene block copolymer, styrene-ethylene-butadiene-styrene block copolymer or styrene- acrylonitrile-butadiene-methyl acrylate copolymer.
  • Suitable active materials are taught for instance in U.S. Pat. No. 6,617,072,
  • the cathode active material may contain nickel hydroxide and nickel oxyhydroxide as taught in U.S. Pat. No. 7,396,379.
  • cathode active material particles are formed in a sintered or pasted electrode.
  • the pasted electrode may be made by mixing the material with various additives and/or binders and applying the paste to a conductive support.
  • one or more cobalt additives are added to the pasted electrode.
  • the cobalt additives may include Co and/or CoO to enhance conductivity, improve utilization and reduce electrical resistance of the positive electrode.
  • Modified nickel hydroxide may contain one or more modifiers such as Co, Cd, Ag, V, Sb, Ca, Mg, AI, Bi, Cr, Cu, Fe, In, rare earths, Mn, Ru, Sn, Ti, Ba, Si, Sr or Zn,
  • a suitable modified nickel hydroxide is (Ni,Co,Zn)(OH) 2 , for instance in the form of a spherical powder.
  • nickel In modified nickel hydroxides, nickel generally is present at a level of > 80 atomic percent, for instance > 90 atomic percent, based on the metals.
  • further cathode active materials are possible. Further cathode active materials include transition metals and their oxides, hydroxides,
  • cathode active materials include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt and Au and their oxides, hydroxides, oxide/hydroxides and fluorides.
  • cathode active materials are selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au;
  • nickel may be present at a level of ⁇ 5, ⁇ 10, ⁇ 15, ⁇ 20, ⁇ 25, ⁇ 30, ⁇ 35, ⁇ 40, ⁇ 45, ⁇ 50, ⁇ 55, ⁇ 60, ⁇ 65, ⁇ 70, ⁇ 75, ⁇ 80 or ⁇ 85 atomic percent, for instance ⁇ 90 atomic percent, based on the total metals of the metal oxides, metal hydroxides and metal oxide/hydroxides.
  • the electrolyte composition may be neutral or acidic, having a pH of about 7 or less.
  • Suitable electrolyte compositions are for example taught in copending U.S. patent applications 14/540,445, filed November 13, 2014 and 14/669,588, filed March 26, 2015.
  • the electrolyte composition allows for transport of protons.
  • the electrolyte compositions have a pH of from about 1 , from about 2, from about 3, from about 4, from about 5 or from about 6 to about 7.
  • Suitable electrolyte compositions contain one or more ionic compounds.
  • the ionic compounds may be protic compounds selected from the group consisting of Bransted acids (protic acids) and protic ammonium compounds or oxonium compounds. Bransted acids for instance have a pKa of less than or equal to about 5.
  • the ionic compounds may be aprotic compounds selected from the group consisting of ammonium compounds, oxonium compounds, phosphonium compounds and alkali or alkali earth metal compounds.
  • the ionic compounds contain a cation and an anion.
  • Alkali metal or alkali earth metal cations include Li + , Na + , K + , Rb+, Cs+, Be ++ , Mg ++ , Ca ++ , Sr* + and Ba ++ .
  • Ammonium ions are cations of formula " "NR1 R2R3R4 where Ri , R2, R 3 and R are selected from hydrogen and hydrocarby! or two of R 1 -R4 together are hydrocarbylene or three of R 1 -R4 together are hydrocarbylene. When one or more of R 1 -R4 is hydrogen, the ammonium ion is protic. When all four of R 1 -R4 are hydrocarbyl or hydrocarbylene the ammonium ion is aprotic.
  • Ammonium ions also include hydrazinium cations of formula Ri R2N- + NR3R 4 R5, where Ri , R2, R 3 , R4 and R 5 are selected from hydrogen and hydrocarbyl or Ri and R 2 together and/or two of R3-R5 together are hydrocarbylene.
  • Ammonium ions a!so include hydroxylammonium cations of formula HO- + Ri R 2 R3 where Ri , R 2 and R 3 are selected from hydrogen and hydrocarby! or two of R 1 -R3 together are
  • Oxonium ions are positively charged groups of formula OR1 R2R3 where Ri , R 2 and R 3 are selected from hydrogen and hydrocarby! or two of R 1 -R3 together are hydrocarbylene. When one or more of R 1 -R3 is hydrogen, the oxonium is protic. When ail three of R 1 -R3 are hydrocarbyl or hydrocarbylene, the oxonium is aprotic.
  • Phosphonium ions are positively charged groups of formula + PRi R 2 R 3 R 4 where Ri , R 2 , R 3 and R 4 are hydrocarby! or two of R 1 -R4 together are hydrocarbylene.
  • Hydrocarbyl is any hydrocarbon based group, bound to the cationic nitrogen, oxygen or phosphorus with a carbon atom.
  • Hydrocarbylene is a ring-forming version of hydrocarbyl.
  • Hydrocarbyl is for instance alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl or aralkyl, which may be substituted by one or more groups selected from the group consisting of halogen, hydroxy, CrC 4 alkoxy, thio, Ci-C 4 a!ky!thio, amino, Ci-C4alkylamino, di-CrC 4 a!ky!amino, nitro, cyano, - COOH and -COO " . Hydrocarby! may also be interrupted by one or more groups selected from the group consisting of -G-, -S-, -NH- and -N(Ci-C 4 alkyl)-.
  • Hydrocarbyl may be both substituted by one or more of said groups and interrupted by one or more of said groups.
  • alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl or aralkyl may be substituted by one to three groups selected from the group consisting of chloro, hydroxy, methoxy, ethoxy, propoxy, butoxy, thio, methylthio, methylamino, ethylamino, propylamino, butylamino, dimethylamino, diethylamino, dipropylamino, dibutylamino, -COOH, -COO " , cyano and nitro and/or may be interrupted by one to three groups selected from the group consisting of -O-, -S-, -NH- and -N(Ci-C 4 alkyl)-.
  • Hydrocarbyl also includes polyethylene glycols and polypropylene glycols such as
  • R'(OC 2 H4 or R'(OC3H 6 )i where R' is hydrogen or alky! and n is an integer from 1 to 50, for instance from 1 to 40, 1 to 30 or 1 to 20, for instance from 1 to 10,
  • R1-R5 When two or three of R1-R5 together are hydrocarbylene, this means together with the N, O or P atom they form a heterocyclic ring.
  • the ring is for example 5- or 8-membered.
  • the heterocyclic ring may contain a further heteroatom and may be saturated or unsaturated.
  • the further heteroatom is for example N, O or S.
  • ammonium ion rings are piperidinium, pyrrolinium, 2,4-dimethyipyrazoiium, pyrrolininium, pyrrolidinium, pyridinium, morpholinium and methylpyridinium.
  • Pyridinium is an example of where three of R1-R4 together form a ring.
  • the hydrocarbylene ring may also be annulated to form for instance quinolinium or isoquinolinium.
  • Aikyl is for instance from 1 to 25 carbon atoms, is branched or unbranched and includes methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-ethylbutyl, n-pentyl, isopentyi, 1-methyipentyi, 1 ,3-dimethylbutyl, n-hexyl, 1-methylhexyl, n-heptyi, isoheptyl, 1 ,1 ,3,3- tetramethyibutyl, 1-methylheptyl, 3-methylheptyl, n-octyi, 2-ethyihexyi, 1 ,1 ,3-trimethylhexyl, 1 , 1 ,3,3-tetramethyipentyi, nonyl, decyi, undecyl, 1-methylund
  • Partly or fully fiuorinated means replacement of one, more than one or all of the hydrogens of the alkyl with fiuoro.
  • Perfluoroalkyl means all hydrogens of an alkyl are replaced with fluoro (fully fiuorinated).
  • Alkenyl is an unsaturated version of alkyl, for instance allyl.
  • Cycloalkyi includes cyclopentyl, methylcyclopentyl, dimethylcyclopentyl, cyciohexyi, methylcyclohexyl, dimethyicydohexyl, trimethylcyclohexyl, tert-butylcyclohexyl, cycioheptyl or cyciooctyl.
  • Cycloalkenyl is an unsaturated version of cycloalkyi.
  • Aryi includes phenyl, 0-, m- or p-methylphenyi, 2,3-dimethyiphenyi, 2,4-dimethylphenyl, 2,5- dimethylphenyl, 2,6-dimethylphenyl, 3,4-dimethylphenyl, 3,5-dimethylphenyl, 2-methyi-6- ethylphenyl, 4-tert-butyi phenyl, 2-ethylphenyl or 2,6-diethyiphenyi.
  • Aralkyl includes benzyl, a-methylbenzyl, ⁇ , ⁇ -dimethylbenzyl and 2-phenylethyl.
  • ammonium ions examples include protic ions such as NH 4 + (ammonium),
  • quinolinium isoquinolinium, pyrrolinium, pyrrolininium and pyrrolidinium.
  • ammonium ions also include aproiic ions such as 1-butyl-1- methylpyrrolidinium, ieiramethylammonium, tetraethylammonium, tetra-n-butylammonium, n- butyl-tri-ethylammonium, benzyl-tri-meihyiammonium, tri-n-butylmethylammonium, benzyl ⁇ tri- ethylammonium, 1-meihylpyridinium, 1-buiyl-3,5-dimeihylpyridinium, 1 ,2,4-trimethylpyrazolium, trimethylhydroxyethylammonium (choline), tri-(hydroxyethyi)methylammonium, dimethyl- di(polyoxyeihyiene)ammonium, 1 ,2,3-trimethylimidazolium, 1-butyl-3-methylimidazolium, 1- ethyl-2,3-d
  • Pyrrolinium is the ammonium of pyrrole
  • pyrrolininium is the ammonium of pyrroline
  • pyrrolidinium is the ammonium of pyrrolidine.
  • Pyrroline may be 1-, 2- or 3-pyrroline, thus the ammonium cation of 1-, 2- or 3-pyrroline is included.
  • hydrazinium ion is hydrazinium (H 2 NNH 3 + ).
  • hydroxyiammonium ion is hydroxyiammonium (HO-NH 3 + ).
  • protic oxonium ions examples include H 3 0 + (hydronium), ⁇ ( ⁇ ) 2 , ⁇ 2 ⁇ + , H 2 MeO + , HO(Me)2, proionated THF and protonated 2-methyl ⁇ THF.
  • aprotic oxonium ions examples include O(Me)3, ⁇ ( ⁇ ) 3 and methylated or ethyiated THF or 2-methyl-THF.
  • Me is methyl
  • Et is ethyl
  • nBu is n-butyi
  • tBu is tert-butyl
  • THF is
  • butyl means n-butyi.
  • Examples of phosphonium ions include methyitriphenylphosphonium,
  • Suitable anions are hydroxide, nitrate, perchlorate, bifiuoride, aikoxides, haiides, phosphates, phosphinates, phosphonates, borates, carboxylates, sulfites, sulfates, sulfonates, carbonates, imides, aluminates, cyanates, methides, arsenates, silicates and antimonates.
  • Anions, cations and ionic compounds may be those disclosed for instance in U.S. Pat. No. 6,254,797 and U.S. Pub. No. 201 1/0045359.
  • Bifiuoride is HF 2 ⁇
  • Aikoxides are RO where R is hydrocarbyl, for example methoxide, ethoxide, n-propoxide, i-propoxide, n-butoxide, t-butoxide or phenoxide.
  • Alkoxides also include where R is perfluoroalkyi. Haiide is chloride, bromide, iodide or fluoride.
  • Phosphates include dihydrogen phosphate, hydrogen phosphate, alkyi phosphate, dialkyl phosphate, phosphate, PFs " (hexafluorophosphate), HPO3F " (fluorohydrogen phosphate), trisoxalatophosphate (TOP), tetrafluorooxalatophosphate (TFOP) and
  • fluoro(perfluoroalkyl)phosphates such as F 2 P(C 2 F5)4 ⁇ F3P(C 2 F 5 )3 "
  • Phosphinates are for instance hydrogen aikyl phosphinate, dialkyl phosphinate, hydrogen aryi phosphinate or diaryl phosphinate. For instance bis(2,4,4-frimethyiphenyi)phosphinafe. Phosphonates are for instance
  • alkylphosphonate such as methylphosphonate or hydrogenphosphonate (phosphonate).
  • Borates include orthoborate, tetrahydroxyborate, tetraborate, tetraphenyl borate, [B(3,5 ⁇ (CF3) 2 C S H3) ] ⁇ (BARF), B(C 2 0 4 ) 2 ⁇ (bis(oxaiato)borate) (BOB), difluoro(oxalato)borate (dFOB), di(frifluoroacetato)oxalatoborafe (D(Ac)OB), B(CsF 5 )4 ⁇ and BF 4 ⁇ (tetrafiuoroborate).
  • Carboxyiate anions are of formula RCOO- where R is hydrogen or hydrocarby!
  • ethylenediaminetetraacetic acid a carboxyiate of diethylenetriaminepentaacetic acid and haioaikylcarboxyiates such as fluoroacetate, difiuoroacetafe, trifiuoroacetafe, chioroacetate, dichioroacetate and trichloroacetate.
  • Sulfites include sulfite and hydrogensuifite.
  • Sulfates include hydrogensulfate, sulfate, thiosulfate and alkyisulfates such as methyisu!fate and ethylsuifate.
  • Sulfonates include aikyl, arylsulfonates and perfluoroaikylsuifonates, for instance trifiuoromethanesuifonate (triflate), p ⁇ toiuenesuifonate (tosylate) or methanesulfonate
  • Carbonate anions are for instance carbonate, hydrogencarbonate or an aikylcarbonate such as methylcarbonate, ethylcarbonate or butyicarbonafe.
  • imide anions include dicyanamide, N(S0 2 F) 2 " ((bisfiuorosulfonyi)imide), bis(perfiuoroalkylsulfonyl)imides such as [N(S0 2 CF 3 ) 2 ] ⁇ (bistriflimide), bis(pentafluoroethyisulfonyi)imide and
  • A!uminates include AI(OC(CF3 3 4 ⁇ di(trifluoroacetato)oxalatoaluminate (d(Ac)OAI),
  • Cyanates include thiocyanate and cyanate, ethides include
  • tris(perfluoroalkylsulfonyl)methides such as tris(trifiuoromethylsulfonyl)methide, C(CF3S0 2 ) 3 " .
  • Arsenates include arsenate, hydrogen arsenate, dihydrogen arsenate and AsF s ⁇ Silicates include SiFs ⁇ 2 .
  • Antimonates include SbFe " and Sb(OH)s ⁇ .
  • the protic ionic compound is H 3 P0 4 , NH4SO3CF3, NH4BF4, NH4OH, NH4CI, NH 4 Br, NH4I, NH 4 F, NH4H2PO4, ( ⁇ 4 ) 2 ⁇ 0 , methylammonium phosphonate, pyridinium tosylate, pyridinium chloride, anilinium chloride, hydroxylammonium chloride, (NH4)2S04, hydrazinium sulfate (N 2 H 6 S04), (NH 4 )HS0 4 , NaHSQ 4 , NH4BF4, H2SO4, KH2PO4, K2HPO4, NaH 2 P0 4 , Na 2 HP04, HBF 4 , H(OEt 2 )BF 4 , HPF S , HAsFg, HCI0 4 , HSO3CF3, H[N(S0 2 CF 3 ) 2 ] or
  • the protic ionic compound may also be an oxonium ion of a highly non-coordinating ion such as Brookhart's acid (BARF acid), [H(GEt 2 )2][B[3,5- CF3)2C 6 H3]4j.
  • a highly non-coordinating ion such as Brookhart's acid (BARF acid), [H(GEt 2 )2][B[3,5- CF3)2C 6 H3]4j.
  • Other examples include [H(OEt2) 2 ][B(CsF 5 )4] (oxonium acid) and [H(OEt 2 ) 2 ][AI(OC(CF3) 3 )4].
  • the cation is protonated diethyl ether (diethyl ether oxonium).
  • the cation may be other protonated ethers, for instance protonated tetrahydrofuran (THF).
  • the protic ionic compound may be a protic ionic liquid such as ethylammonium nitrate, diethylmethylammonium trifluoromethanesulfonate (DEMA TfO), triethylammonium
  • methanesulfonate 2-methylpyridinium trifluoromethanesulfonate, ammonium fluoride, methylammonium nitrate, hydroxyethyiammonium nitrate, ethylammonium nitrate,
  • dimethylammonium nitrate 1-methylimidazoiium nitrate, 1-ethylimidazolium nitrate, t- buty!ammonium tetrafiuoroborate, hydroxyethyiammonium tetrafiuoroborafe,
  • methoxyethylammonium mesylate dimethylammonium mesylate, dibutylammonium mesylate, triethylammonium mesylate, dimethylethylammonium mesylate, hydronium hydrogensulfate, ammonium hydrogensulfate, methylammonium hydrogensulfate, ethylammonium
  • propylammonium dihydrogen phosphate n-butylammonum dihydrogen phosphate, methoxyethylammonium dihydrogen phosphate, dimethylammonium dihydrogen phosphate, dibutylammonium dihydrogen phosphate, methylbutylamrnonium dihydrogen phosphate, ammonium bifiuoride, methylammonium bifluoride, ethylammonium bifiuoride or
  • Carboxyiic acids are protic acids/protic compounds. Carboxylic acids are of formula RCOOH where R is hydrogen or hydrocarbyi. Carboxylic acids contain carboxylate anions. Carboxylic acids include formic acid, acetic acid, acrylic acid, fluoroacetic acid, difiuoroacetic acid, trifluoroacetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methyibutanoic acid, valeric acid, hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- o 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, glycolic acid, gluconic acid, malic acid, mandelic acid, nitrilotriacetic acid, N- (2-hydroxyethyl)-ethylenediaminetriacetic
  • the aprotic ionic compound is N e 4 + S0 3 CF 3 ' , NMe 4 OH, Et ⁇ BF*-, NMe, + CI-, NEt4 + Br, NnBu 4 + l " , NnBu 4 + F " , NEt 4 + f-1 2 PCv, ( ⁇ 4) 2 ⁇ 4, methyltriphenyl phosphonium iodide, tetrakis(hydroxymethyl)phosphonium chloride, tetraphenylphosphonium bromide, 1- methylpyridinium chloride, benzalkonium chloride, e 3 OBF 4 , Et 3 OBF 4 , NEt 4 PF s , N e 4 AsF 6 , NMe 4 CI0 4 , NEt 4 S0 3 CF 3 , NMe 4 [N(S0 2 CF 3 ) 2 ] or NEt4[N(S0 2 CF 2 CF 3 ) 2
  • the aprotic ionic compound may also include a highly non-coordinating anion such as BARF, for instance sodium BARF, Na + B[3,5 ⁇ (CF 3 ) 2 C 6 H 3 ]4] " .
  • BARF highly non-coordinating anion
  • Other examples include
  • the aprotic ionic compound may be an aprotic ionic liquid such as tri-n- butylmethylammonium methylsuifate, 1-ethyl-2,3-dimethylimidazolium ethylsulfate, 1-butyl-3- methylimidazoiium thiocyanate, 1-bufyl-3-methyiimidazolium tetrachloroaluminate, 1-butyl-3- methylimidazolium methylsuifate, 1-butyl-3-methylimidazolium methanesulfonate, 1 -butyl-3- methyiimidazolium hydrogencarbonate, 1-butyl-3-methylimidazolium hydrogensulfate, 1-butyl-3- methylimidazolium chloride, 1 ,2,3-trimethylimidazolium methylsuifate, tris- (hydroxyethyl)methyiammonium methylsuifate,
  • tributylmethylphosphonium dibutylphosphate triethylmethylphosphonium dibutylphosphate, tetrabutylphosphonium tetrafiuoroborate, tetrabutylphosphonium p-toluenesulfonate, tributylmethylphosphonium methyicarbonate, 1-ethyl-3-methylimidazolium hydrogencarbonate, tnbutylmethylammonium methyicarbonate, tnbutylmethylammonium dibutylphosphate, 1 -ethyl-3- methylimidazolium dibutylphosphate, 1-butyl-3-methylimidazolium dibutylphosphate, 1- (cyanomethyl)-3-methylimidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-methylimidazoiium bis(trifluoromethylsulfony
  • trihexyltetradecylphosphonium dicyanamide 3-(triphenylphosphonio)propane-1-suifonate or 3- (triphenylphosphonio)propane-l-sulfonic acid tosyiate.
  • carboxyiate compounds are tetramethylammonium benzoate,
  • tetraethylammonium oxalate tetrabutylammonium tartrate, sodium tartrate, potassium formate, tetramethylammonium acetate, 1-methylpyridinium chloride, trimethylammonium citrate tri-basic, tetramethylammonium 2-, 3- or 4-nifrobenzoate, ammonium benzoate, ammonium salicylate, ammonium oxalate, ammonium tartrate, methyltriphenyl phosphonium acetate, tetrakis(hydroxymethyl)phosphonium benz shareholders, tetrakis(hydroxymethyl)phosphonium formate, mono- or di-potassium tartrate, ammonium citrate mono-, di ⁇ or tri-basic; ammonium 2- nitrobenzoate, ammonium 3-nitrobenzoate, ammonium 4-nitrobenzoate, potassium
  • ammonium and/or alkali metal and/or alkali earth metal ions may replace one or any number of the acidic hydrogens to form a present carboxylate compound.
  • ionic liquids are ionic compounds that exhibit a melting point of ⁇ 100°C.
  • the ionic compound is "a salt" with a melting point > 100°C.
  • ionic liquids generally are ammonium or phosphonium compounds, that is containing ammonium or phosphonium cations.
  • Salts include halide salts such as alkali or alkali earth metal halide salts such as NaCi, KCi or KBr as well as other ionic compounds with melting points above 100°C, Alkali and alkali earth metal salts include for instance anions selected from the group consisting of nitrate, perchlorate, bifluoride, halides, phosphates, phosphinates, phosphonates, borates,
  • carboxylates sulfites, sulfates, sulfonates, carbonates, imides, aiuminates, cyanates, metbides, arsenates, silicates and antimonates.
  • the present ionic compounds may contain the cation and anion together in the same molecule.
  • zwitterionic compounds inner salts
  • betaines betaines
  • zwitterions containing ammonium or phosphonium ions and sulfonate or sulfate ions. Included are hydroxysultaines, 4-(triphenylphosphonio)butane-1-sulfonate, methyl N- (triethylammoniosulfonyl)carbamate (Burgess reagent) and phosphonium sulfate zwitterions as taught for instance in U.S. Pat. No. 3,471 ,544. Included is sulfamic acid.
  • two or more different ionic compounds are employed in the electrolyte composition.
  • the two different ionic compounds may be a protic ionic compound and an aprotic ionic compound or may be an ionic liquid and a salt.
  • present electrolyte compositions may comprise at least two different ionic liquids.
  • the electrolyte composition may comprise one or more ionic liquids and one or more salts, for example a protic or aprotic ammonium salt or an alkali metal salt such as an alkai metal halide.
  • the electrolyte composition may contain a mixture of a carboxylate compound and a carboxylic acid.
  • the electrolyte composition may contain a mixture of a carboxyiate-containing ionic liquid and a carboxylic acid.
  • the electrolyte composition may contain two different carboxylic acids.
  • the electrolyte composition may contain a protic acid, protic ammonium compound or a protic oxonium compound and an ionic liquid.
  • the weight:weight ratio of the two different ionic compounds is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
  • the cations or the anions may be identical.
  • the electrolyte compositions advantageously contain an ionic liquid.
  • Cations of ionic liquids include ammonium and phosphonium ions discussed above.
  • Ionic liquids may contain a cation selected from the group consisting of formulae (a)-(h)
  • each R is independently H, CrCi 6 aikyl or hydroxyCi-Ci 6 alkyl, for instance methyl, ethyl, hydroxyethyl or propyl and
  • X is CH2, O, S or NR where R is H or Ci-Cisalkyl, for instance H, methyl, ethyl or propyl.
  • suitable cations of ionic liquids include 1-ethyl-3-methylimidazoliurrs, 1-hexyl-3- methyiimidazoiium, 1-butyl-l-methyipyrroiidinium and trihexyl(tetradecyl)phosphonium.
  • Anions of ionic liquids include carboxylates, imides, methides, nitrate, bifiuoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aiuminates.
  • the ionic liquids may contain an anion selected from the group consisting of
  • y is an integer of 1 to 6
  • n is an integer of 1 to 8, for instance 1 to 4,
  • z is an integer of 1 to 4,
  • X is B or Al
  • Rw, Rx, R y and R z are independently halogen, CrC 2 oalkyl, CrC 2 oalkyl which is partly or fuliy fiuorinated, Ci-C 2 oalkoxy, CrC 2 oaikoxy which is partly or fuliy fiuorinated, Ci-C 2 oaikyl-COO or CrC 2 oalkyl-COO which is partly or fully fiuorinated and
  • O ⁇ O is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxyiic acid or from a 1 ,2- or 1 ,3-hydroxycarboxylic acid and
  • the anions of ionic liquids may include F 2 P(C2F 5 ) " , FsP ⁇ Fs , F ⁇ CaFs ' , F 2 P(C 3 F 7 ) ' , F 3 P(C 3 F 7 )3 " , F 4 P(C 3 F 7 )2 " , F 2 P(C 4 F9) ' , F 3 P(C 4 F 9 ) 3 -, F 4 P(C 4 F 9 ) 2 -, perfluoroalkylcarboxylate, perfluoroaikylsulfonaie, bis(perfluoroalkylsulfonyl)imide,
  • tris(trifluoromethylsulfonyl)methide, tetrafiuoroborate, spiro-oxo borates and spiro-oxo phosphates for example bisoxaiatoborate (BOB), difiuorooxalatoborate (dFOB),
  • the electrolyte composition may be "non-aqueous", containing essentially no inadvertent water, for instance ⁇ 1000 ppm, ⁇ 100 ppm or ⁇ 10 ppm by weight water, based on the total weight of the electrolyte composition.
  • the electrolyte compositions may advantageously be "anhydrous", that is, containing little or no water.
  • the electrolyte compositions may contain ⁇ 10 ppm water, for instance ⁇ 9, ⁇ 8, ⁇ 7, ⁇ 6, ⁇ 5 or ⁇ 4 ppm wafer by weight, based on the total weight of the electrolyte composition.
  • the electrolyte composition may advantageously contain a solvent.
  • the electrolyte composition may contain no solvent.
  • solvents are not required when one or more ionic liquids are employed in the electrolyte composition. "No solvent” means no organic solvent is present and essentially no inadvertent water is present.
  • the weightweight ratio of ionic compounds in total to solvent may be from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 80:40 to about 40:80.
  • the present electrolyte compositions may not be limited by the hydrogen and oxygen evolution potential of water.
  • the electrochemical cells disclosed may exhibit a nominal open-circuit voltage of > 1.2 V (volts).
  • the present cells may supply a nominal open-circuit voltage up to about 8 V.
  • present cells may exhibit a nominal open-circuit voltage of from about 1.2 to about 8.0 V, from about 1.3 to about 6.0 V, from about 1.4 to about 6.0 V or from about 1.5 to about 6.0 V.
  • present ceils may exhibit a nominal open-circuit voltage of about 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1 , 3.2, 3.3, 3,4, 3,5, 3.8, 3.7, 3.8, 3.9, 4.0, 4,1 , 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1 , 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9 or about 6.0 V.
  • Solvents are wafer and organic solvents.
  • the solvent may consist essentially of water or may consist essentially of organic solvent.
  • the solvent may contain varying ratios of water: organic solvent.
  • the solvent consists essentially of organic solvent
  • water may only be present at very low levels, for example ⁇ 1000 ppm, ⁇ 100 ppm or ⁇ 10 ppm by weight water, based on the total weight of the electrolyte composition.
  • organic solvents may only be present at the same low levels.
  • the solvent may be a water/organic solvent mixture where the weight:weight ratio of waier io organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 80:40 to about 40:80.
  • the weight:weight ratio of waier io organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 80:40 to about 40:80.
  • the electrolyte composition may contain organic solvent and no water.
  • the electrolyte composition may contain water and no organic solvent.
  • Suitable organic solvents are for instance selected from the group consisting of organic carbonates, ethers, glymes, ortho esters, polyalkylene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents, nitrile solvents and combinations thereof.
  • Organic carbonates are cyclic or acyclic and include ethylene carbonate (EC), propylene carbonate (PC), trimethylene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), vinyiene carbonate,
  • Ethers and glymes include dimethoxymethane (DM ), dieihoxymethane, 1 ,2- dimethoxyethane (DME or ethyleneglycol dimethylether or glyme), diglyme, triglyme, tetrag!yme, efhyleneglycol diethylether (DEE), ethyleneglycol dibutylether, diethyleneglycoi diethylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1 ,3-dioxane, 1 ,3-dioxolane (DIOX), 4-methyl-1 ,3-dioxolane (4-MeDIOX), 2-methyl-1 ,3-dioxolane (2-MeDIOX), 1 ,4-dioxane, dimethylether, ethylmethylether, diethylether, di-n-butylether, di
  • Weight average molecular weights (Mw) of polyalkylene glycols are for example from about 200 to about 1200 g/mol, from about 200 to about 1000 g/mol, from about 200 to about 900 g/mol, from about 200 to about 700 g/mol or from about 200 to about 500 g/moL Included are oligomers of 4 monomers and more, for instance tetraethylene glycol, fiuorinated tetraethylene glycol and tefrapropylene glycol. For instance PEG 200, PEG 300, PEG 400, PEG 500, PEG 600, PEG 700, PEG 800, PEG 900 or PEG 1000.
  • Esters and lactones include ⁇ -butyroiactone (GBL), ⁇ -valeroiactone, ⁇ -valerolactone, ethyl acetate (EA), 2-methoxyefhyl acetate, 2-ethoxyethyi acetate, 2-butoxyethyl acetate, 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EG DA), 3-ethoxy ethyl propionate (EEP), methyl butyrate (MB), n-amyi acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate, dimethyl malonate and dibasic ester mixture (DBE).
  • GBL ⁇ -butyroiactone
  • EA ethyl acetate
  • Dibasic ester mixture includes for instance methyl esters of adipic, giutaric and succinic acids.
  • Sulfones and sulfoxides include methylsulfonylmethane (MSM or dimethylsulfone), ethylmethylsulfone, sulfolane and dimethylsulfoxide (DMSO).
  • MSM methylsulfonylmethane
  • ethylmethylsulfone ethylmethylsulfone
  • sulfolane sulfolane
  • DMSO dimethylsulfoxide
  • Amides include dimethylformamide (DMF), dimethylacetamide (DMA), N-methylpyrrolidone (NMP), 2-pyrrolidone, 1 ,3-dimethyl-2-imidazolidinone (DMI), hexamethylphosphoramide (HMPA) and N,N'-dimethyl-N,N'-trimethyleneurea (1 ,3-dimethyl-3,4,5,6-tetrahydro-2(1 H)- pyrimidinone (D PU)).
  • Alcohols include for example benzylaicohol (BA), ethanol, trifluoroethanol (2,2,2- trifluoroethanoi), methanol, isopropanol, t-butanol and n-butanol.
  • BA benzylaicohol
  • ethanol trifluoroethanol (2,2,2- trifluoroethanoi)
  • methanol isopropanol
  • t-butanol t-butanol
  • n-butanol n-butanol.
  • Ketones include for example methylethylketone (MEK) and methyl-isoamylketone (MIAK).
  • Nitro solvents include nitrobenzene, nitromethane and nitroethane.
  • a mixture of solvents is employed, for instance a mixture of organic carbonates or a mixture of one or more organic carbonates and one or more ether or glyme.
  • organic solvents may be employed, for instance common non-polar organic solvents including toluene, hexane, heptane and the like.
  • the electrolyte composition may advantageously comprise an ionic liquid and a protic acid and/or an organic solvent.
  • electrolyte compositions are for instance liquid at room temperature (25°C).
  • Liquid includes syrupy high viscosity liquids.
  • the electrolyte compositions have a viscosity of from about 0.2 cP to about 100 cP at 25°C.
  • Viscosity may be measured for instance with a rotational rheometer or with a
  • microviscometer employing a roiling steel bail in a glass capillary timed and calibrated against control liquids. Viscosity may also be measured with a DVI or DVil Brookfieid viscometer, a plate viscometer or an oscillating type viscometer.
  • the electrolyte composition may contain one or more additives selected from the group consisting of
  • fiuorinated oil sodium sfannate, sodium citrate or poiyacryiic acids
  • HF or KF oxides or hydroxides of rare earths such as Y, metal porphines, for example Ni or Fe porphine, vinyiene carbonate, vinyiethylene carbonate, methylene ethylene carbonate or fiuoro- ethylene carbonate;
  • the electrolyte composition for example at a level of from about 0.1 % to about 15% by weight, based on the total weight of the electrolyte composition.
  • Present anodes may exibit a discharge capacity of > 800 mAh/g over 20 cycles or more (over at least 20 cycles), for example > 810, > 820, > 825, > 830, > 835, > 840, > 845, > 850, > 855, > 860, > 865, > 870, > 875, > 880 or > 895 mAh/g over 20 cycles or more; based on the weight of the hydrogen storage material.
  • an ionic liquid means one ionic liquid or more than one ionic liquid.
  • a stable group IV element-based hydrogen storage negative electrode for electrochemical uses for example a stable silicon-based or carbon-based hydrogen storage negative electrode for electrochemical uses; for example where the electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn, based on the total weight of the hydrogen storage material.
  • An electrode according to embodiment 1 comprising a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn; for example comprising > 27 wt% silicon or > 27 wt% carbon, based on the total weight of the hydrogen storage material.
  • hydrogen storage material comprises carbon; for example carbon in the form of natural graphite, artificial graphite, expanded graphite, graphene, carbon fiber, hard carbon, soft carbon, non-graphitizable carbon, carbon black, carbon nanotube, fuilerene, activated carbon, crystalline carbon or amorphous carbon.
  • the hydrogen storage material comprises one or more further elements, for example one or more elements selected from the group consisting B, Al, Ga, In, As, Sb, Te and transition metals.
  • group IV elements for example Si and/or C
  • An electrode according to any of the preceding embodiments comprising a solid electrolyte interface capable of allowing transport of protons.
  • the hydrogen storage material includes one or more further elements selected from the group consisting of structural modifiers (elements to promote the amorphous phase of a material), hydrogen bond strength modifiers and solid electrolyte interface (SEI) modifiers; for example one or more further elements selected from the group consisting of B, alkaline earth metals, transition metals, rare earth metals, other metals of groups III or V of the periodic table, O, F, P, CI and the like.
  • structural modifiers elements to promote the amorphous phase of a material
  • SEI solid electrolyte interface
  • an electrode according to embodiments 16 or 17 where the electrolyte composition comprises an ionic compound containing a cation selected from the group consisting of NhV " (ammonium), mefhylammonium, ethylammonium, dimeihylammonium, diethylammonium, trimethylammonium (NMe 3 H + ), triethylammonium, tributylammonium, diethylmethylammonium, hydroxyethyiammonium, methoxymethylammonsum, dibutyiammonium, methylbutylammonium, anilinium, pyridinium, 2-methylpyridinium, imidazolium, 1-methyiimidazolium, 1 ,2- dimethylimidazolium, imidazolinium, 1-ethylimidazolium, 1-(4-sulfobutyl)-3-methylimidazolium, l-allylimidazolium, quinolini
  • the cation is 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-butyl-1- methylpyrrolidinium or trihexyl(tetradecyl)phosphonium.
  • y is an integer of 1 to 6
  • Rw, Rx, R y and R z are independently halogen, CrC 20 alkyl, CrC 20 alkyl which is partly or fuliy fluorinated, Ci-C 20 alkoxy, CrC 2 oalkoxy which is partly or fuliy fiuorinated, Ci-C 20 aikyl-COO or CrC 20 alkyl-COO which is partly or fully fluorinated and
  • O ⁇ O is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxyiic acid or from a 1 ,2- or 1 ,3-hydroxycarboxylic acid and
  • An electrode according to any of embodiments 18-21 where the electrolyte composition comprises an ionic compound containing a carboxylate anion of formula RCOO " where R is hydrogen or hydrocarbyi; such as formate, acetate (ethanoate), acrylate, propanoate, n- butanoate, i-butanoate, n-pentanoate, i-pentanoate, octan argue, decanoate, benzoate, salicylate, ihiosalicylate, 2 ⁇ , 3- or 4-nitrobenzoate; citrate, oxalate, tartrate, glycoiate, gluconate, rna!ate, mandelate, a carboxyiate of nitrilotriacetic acid, a carboxylate of N-(2-hydroxyethyi)- ethylenedsamsnetriacetic acid, a carboxyiate of ethyienediaminetetraacetic acid, a
  • an imide anion such as dicyanamide, N(S0 2 F) 2 ⁇ ((bisfluorosuifonyl)irr!ide), a
  • a methide such as a tris(perfluoroalkyisulfonyl)methide, for example
  • a borate such as orthoborate, tetra hydroxy borate, tetraborate, tetraphenylborate, [B(3,5- (CF 3 ) 2 C 6 H3)4]- (BARF), B(C 2 0 4 ) 2 ⁇ (bis(oxalato)borate) (BOB), difiuoro(oxalato)borate (dFOB), di(trifluoroacetato)oxalatoborate (D(Ac)OB), B(C 6 F 5 )4 " or BF 4 "' (tetrafluoroborate); or
  • a phosphate such as dihydrogen phosphate, hydrogen phosphate, alkyi phosphate, dialkyi phosphate, phosphate, PF 6 " (hexafluorophosphate), HP0 3 F- (fluorohydrogen phosphate), trisoxalatophosphate (TOP), tetrafluorooxalatophosphate (TFOP) or a
  • fluoro(perfluoroalkyl)phosphate such as F 2 P(C 2 F 5 )4 " , F3P(C 2 F 5 )3 "
  • a sulfonate such as an alkyisulfonate, arylsuifonate or perfluoroalkylsulfonate, for instance trifluoromethanesulfonate (triflate), p-toluenesulfonate (tosylate) or meihanesulfonaie
  • a carbonate anion such as carbonate, hydrogencarbonate or an alkyicarbonate such as methylcarbonate, ethylcarbonate or butylcarbonate; or
  • an aluminate such as AI(OC(CF 3 )3) 4 ⁇ , di(trifluoroacetato)oxalatoaluminate (d(Ac)OAI), tetrachioroaluminate, tetrafluoroaluminate, tetraiodoaluminate or tetrabromoaiuminate.
  • d(Ac)OAI di(trifluoroacetato)oxalatoaluminate
  • tetrachioroaluminate tetrafluoroaluminate
  • tetraiodoaluminate tetrabromoaiuminate.
  • E25 An electrode according to any of embodiments 18-24 where the electrolyte composition comprises an ionic liquid selected from the group consisting of diethylmethylammonium trifiuoromethanesuifonate (DE A TfO), ethyiammonium nitrate, triethylammonium
  • DE A TfO diethylmethylammonium trifiuoromethanesuifonate
  • ethyiammonium nitrate triethylammonium
  • methanesuifonate 2-methylpyridinium trifiuoromethanesuifonate, ammonium fluoride, methylammonium nitrate, hydroxyethylammonium nitrate, ethyiammonium nitrate,
  • dimethylammonium nitrate 1-methylimidazolium nitrate, 1-ethylimidazolium nitrate, t- butylammonium tetrafluoroborate, hydroxyethylammonium tetrafiuoroborate,
  • meihoxyeihyiammonium mesylate dimethylammonium mesylate, dibutyiammonium mesylate, triethylammonium mesylate, dimethylethyiammonium mesylate, hydronium hydrogensulfate, ammonium hydrogensulfate, methylammonium hydrogensulfate, ethyiammonium
  • meihoxyeihyiammonium dihydrogen phosphate dimethylammonium dihydrogen phosphate, dibutyiammonium dihydrogen phosphate, methylbutyiammonium dihydrogen phosphate, ammonium bifluoride, methylammonium bifiuoride, ethyiammonium bifluoride and
  • E26 An electrode according to any of embodiments 16-25 where the electrolyte composition comprises an ionic liquid selected from the group consisting of 1-ethyl-3-methylimidazolium trifiuoromethanesuifonate (EMIM TfO), 1-ethyi-3-methylimidazolium tetrafluoroborate (EMIM BF4), 1-ethyl-3-methylimidazolium bis(trifiuoromethylsulfonyl)imide (EMIM TFSI), 1-ethyi-3- methylimidazolium acetate (EMI Ac), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIM TfO), 1-butyl ⁇ 3-methylimidazolium acetate (BMIM Ac), 1-butyl ⁇ 3 ⁇ methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), tri-n-butylmethylammonium methylsul
  • tributylmethylphosphonium dibutylphosphate triethylmethylphosphonium dibutylphosphate, teirabutylphosphonium ieirafiuoroboraie, teirabutylphosphonium p-toluenesulfonate, tributylmethylphosphonium meihyicarbonate, 1-ethyi-3-meihylimidazolium hydrogencarbonate, tributylmethylammonium meihyicarbonate, tributylmethylammonium dibutylphosphate, 1 -ethyl-3- methyiimidazoiium dibutylphosphate, 1-butyl-3-methylimidazolium dibutylphosphate, 1- (cyanomeihyl)-3-meihylimidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-meihyiimi
  • hydrochloric acid nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid or periodic acid; or
  • a bisulfate such as sodium bisulfate, potassium bisulfate or ammonium bisulfate; or
  • HAsFs HBF 4 , H(OEt 2 )BF 4 , HPF 6 , ,H[N(S0 2 CF 3 ) 2 ] or H[N(S0 2 CF 2 CF 3 )2].
  • an electrode according to any of embodiments 16-27 where the electrolyte composition comprises an organic protic acid such as a carboxylic acid of formula RCOOH where R is hydrogen or hydrocarbyi, for example formic acid, acetic acid, acrylic acid, fiuoroacefic acid, difluoroacetic acid, trifluoroacetic acid, chioroacetic acid, dichioroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methylbutanoic acid, valeric acid, hexanoic acid, hepfanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- or 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, giycolic acid, gluconic acid, malic acid, mandelic acid, nitriiotriacefic acid, N-(2-hydroxyethyl)-ethylenediaminetriacetic acid,
  • E29 An electrode according to any of embodiments 16-28 where the electrolyte composition comprises a protic sulfonic acid of formula RSO3H where R is alkyi or aryi or aikyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsuifonic acid, methanesuifonic acid or trifiuoromethanesuifonic acid.
  • BARF acid Brookhart's acid
  • H(OEt2)2][B[3,5-(CF3)2CeH 3 ]4 [H(OEt 2 ) 2 l[B(CsF 5 ) 4 ] (oxonium acid) or [H(OEt 2 ) 2 ][AI(OC(CF 3 ) 3 ) 4 ].
  • E31 An electrode according to any of embodiments 16-30 where the electrolyte composition comprises at least two different ionic compounds; for example, where the electrolyte
  • a salt and an ionic liquid for example a protic or aprotic ammonium salt or an alkali metal salt such as an alkai metal halide;
  • E32 An electrode according to any of embodiments 18-31 where the electrolyte composition comprises two different ionic compounds which contain an identical cation or an identical anion.
  • E33 An electrode according to any of embodiments 16-32 where electrolyte composition comprises two different ionic compounds with a weight:weight ratio of from about 99.9:0.1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
  • E36 An electrode according to any of embodiments 18-33 where the electrolyte composition comprises a solvent consisting essentially of water.
  • An electrode according to embodiment 38 where the weigb weight ratio of water to organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
  • organic solvent comprises one or more solvents selected from the group consisting of organic carbonates, ethers, glymes, ortho esters, poiyaikiene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents and nitrile solvents.
  • an organic carbonate for example a cyclic or acyclic organic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), trimethylene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyimethyi carbonate (EMC), vinylene carbonate, difluoroethylene carbonate or monofluoroethylene carbonate; or an ether or giyme such as dimethoxymethane (DMM), diethoxymethane, 1 ,2-dimethoxyefhane (DME or ethyleneglycol dimethyiether or glyme), diglyme, trigiyme, tetragiyme, ethyleneglycol diethylether (DEE), ethyleneglycol dsbutylether, dsethyieneglycol diethylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2
  • an ortho ester such as trimethoxymethane, triethoxymethane, 1 ,4-dimethyl-3,5,8- trioxabicyclo[2.2.2]octane or 4-ethyl-1-methyl-3,5,8-trioxabicyclo[2.2.2]octane; or
  • an ester or lactone such as ⁇ -butyrolactone (GBL), ⁇ -valerolactone, ⁇ -valerolactone, ethyl acetate (EA), 2-methoxyethyl acetate, 2-ethoxyethyi acetate, 2-butoxyethyl acetate, 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EGDA), 3-ethoxy ethyl propionate (EEP), methyl bufyrate (MB), n-amyi acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate or dimethyl malonate; or
  • GBL ⁇ -butyrolactone
  • EA ethyl acetate
  • 2-methoxyethyl acetate 2-ethoxyethyi
  • a dibasic ester mixture such as methyl esters of adipic, glutaric or succinic acids; or a glycol such as ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2- propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol (ethylene glycol butyl ether, EB), 2- phenoxyethanol, 2-benzyioxyethanoi, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol (diethylene glycol butyl ether, DB), propylene glycol butyl ether (PB), propylene glycol methyl ether (PM), triethylene glycol (TEG), dipropylene glycol methyl ether (DPM), diethylene glycol methyl ether, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, perfluoro-1
  • a formate such as methyl formate, ethyl formate, isobutyl formate or tert-butyl formate; or a sulfone or sulfoxide such as methylsulfonylmethane ( SM or dimethy!su!fone),
  • an amide such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methyipyrroiidone (NMP), 2-pyrrolidone, 1 ,3-dimethyl-2-imidazolidinone (DMI), hexamethylphosphoramide (H PA) or N.N'-dimethyl-N.N'-trimethyleneurea (1 ,3 ⁇ dimethyl-3,4,5,6 etrahydro-2(1 H)- pyrimidinone (DMPU)); or
  • an alcohol such as benzylalcohoi (BA), ethanol, trifluoroethanol (2,2,2-trifluoroethanol), methanol, isopropanol, t-butanol or n-butanol; or
  • a ketone such as methylethylketone (MEK) or methyl-isoamylketone (MIAK); or
  • a nitrile solvent such as acetonitriie, propionitrile, butyronitrile or adiponitrile.
  • E42 An electrode according to any of embodiments 16-33 and 35-41 where the electrolyte composition comprises a solvent and where the weigh weight ratio of ionic compounds in total to solvent is from about 99.9:0, 1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 80:40 to about
  • electrolyte composition further comprises one or more additives selected from the group consisting of corrosion inhibitors, solid electrolyte interface (SE!) improvers, proton evolution improvers, self-discharge inhibitors, anti-gassing agents, viscosity adjusting agents, cathode protection agents, salt stabilizers, conductivity improvers and solvating agents,
  • fluorinated oil sodium stannate, sodium citrate or polyacrylic acids
  • HF or KF oxides or hydroxides of rare earths such as Y, metal porphines, for example Ni or Fe porphine, vinylene carbonate, vinylethylene carbonate, methylene ethylene carbonate or fiuoro- ethylene carbonate;
  • polyglycols polyglycol alkyl ethers, polyglycol alkyl phosphate esters or polysorbates such as polyethylene glycol (PEG), polypropylene glycol, polysorbate 20, polysorbate 40 or polysorbate 80 or a mixture of PEG 600 and polysorbate 20 or a mixture of PEG 600 and ZnO;
  • PEG polyethylene glycol
  • polysorbate 20 polysorbate 40 or polysorbate 80 or a mixture of PEG 600 and polysorbate 20 or a mixture of PEG 600 and ZnO;
  • phosphate ester-based surfactants propane sultone or fiuoropropane sultone
  • the electrolyte composition for example at a level of from about 0.1 % to about 15% by weight, based on the total weight of the electrolyte composition.
  • volumetric energy density of the cell is > 250 Wh/L, for instance, > 260 Wh/kg, > 265, ⁇ 270, ⁇ 275, ⁇ 280, ⁇ 285, ⁇ 290, > 295, ⁇ 300, > 305, > 310, > 315, > 320, > 325, > 330, > 335,
  • a rechargeable electrochemical cell comprising a negative electrode according to any of embodiments 1-15, a positive electrode, a casing having said electrodes positioned therein and an electrolyte composition according to any of embodiments 16-44 in contact with the electrodes, where the reversible half cell charge/discharge electrochemical reaction at the negative electrode is or
  • /V is a group IV element-based hydrogen storage material
  • Si is a silicon-based hydrogen storage material.
  • the positive electrode comprising one or more cathode active materials selected from the group consisting of transition metals, transition metal oxides, transition metal hydroxides, transition metal oxide/hydroxides and transition metal fluorides; for example one or more materials selected from the group consisting of
  • An electrochemical cell comprising a stable group IV element-based hydrogen storage negative electrode; for example a stable silicon-based or carbon-based hydrogen storage negative electrode; for example where the negative electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn, based on the total weight of the hydrogen storage material;
  • the ceil also comprising an aqueous or non-aqueous electrolyte composition in contact with the electrode.
  • the negative electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn; for example comprising > 27 wt% silicon or > 27 wt% carbon, based on the total weight of the hydrogen storage material.
  • a ceil according to embodiments 1 or 2 where the hydrogen storage material comprises amorphous silicon, microcrystaliine silicon, nanocrystaliine silicon, monocrystailine silicon, polycrystalline silicon, protocrystal!ine silicon or porous silicon.
  • the hydrogen storage material comprises an alloy of silicon and one or more of carbon, germanium and tin, for example amorphous silicon carbide or an alloy of silicon and germanium or an alloy of silicon and tin.
  • the hydrogen storage material is hydrogenated prior to assembly of the cell (a pre-hydrogenated negative electrode); for example where the hydrogen storage material is hydrogenated amorphous silicon (a-Si:H) or hydrogenaied amorphous silicon carbide (a-Sii. x C x :H, where x is for example from about 0.01 to about 0.99, from about 0.05 to about 0.95 or from about 0.1 to about 0.9).
  • the hydrogen storage material for example amorphous silicon
  • a film for example a film with a thickness > 20 nm, > 50 nm, > 90 nm, > 120 nm or > 180 nm or from about 90 nm to about 10 ⁇ , from about 100 nm to about 5 ⁇ , from about 150 nm to about 3 ⁇ , from about 150 nm to about 2 ⁇ or from about 150 nm to about 1 ⁇ .
  • a cell according to any of the preceding embodiments where the hydrogen storage material is comprised in a film in adherence to a substrate for example a substrate selected from metal, glass, inorganics and plastic.
  • the hydrogen storage material comprises one or more further elements, for example one or more elements selected from the group consisting B, Ai, Ga, in, As, Sb, Te and transition metals.
  • the hydrogen storage material contains > 28 wt%, ⁇ 29 wt%, > 30 wt%, ⁇ 35 wt%, ⁇ 40 wt%, > 45 wt%, ⁇ 50 wt%, ⁇ 55 wt%, > 60 wt%, > 65 wt%, ⁇ 70 wt%, > 75 wt%, ⁇ 80 wt%, ⁇ 85 wt%, ⁇ 90 wt%, ⁇ 95 wt%, ⁇ 96 wt%, > 97 wt%, > 98 wt% or > 99 wt% of one or more elements selected from the group consisting of group IV elements, for example Si and/or C, based on the total weight of the hydrogen storage material.
  • group IV elements for example Si and/or C
  • the negative electrode comprises ⁇ 30% by weight of the one or more group IV elements; for example ⁇ 35%, ⁇ 40%, > 45%, > 50%, > 55%, > 60%, > 65%, > 70%, > 75% > 80%, > 85% or > 90% by weight of the one or more group IV elements, for example Si and/or C, based on the total weight of the negative electrode.
  • the negative electrode further comprises one or more components selected from the group consisting of binders, conductive materials and other additives.
  • the hydrogen storage material includes one or more further elements selected from the group consisting of structural modifiers (elements to promote the amorphous phase of a material), hydrogen bond strength modifiers and solid electrolyte interface (SEI) modifiers; for example one or more further elements selected from the group consisting of B, alkaline earth metals, transition metals, rare earth metals, other metals of groups III or V of the periodic table, O, F, P, CI and the like.
  • structural modifiers elements to promote the amorphous phase of a material
  • SEI solid electrolyte interface
  • E16 A ceil according to any of the preceding embodiments where the electrolyte composition which is neutral or acidic, for example having a pH of about 7 or lower; for example from about 1 , from about 2, from about 3, from about 4, from about 5 or from about 6 to about 7.
  • electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, protic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotsc oxonium compounds, aprotic phosphonsum compounds and alkali or alkali earth metal salts.
  • the electrolyte composition comprises an ionic compound containing a cation selected from the group consisting of NH 4 + (ammonium), methylammonium, ethylammonium, dsmethylammonium, diethylammonium, trimethylammonium (NMe 3 H + ), triethylammonium, tributylammonium, diethylmethylammonium, hydroxyethyiammonium, methoxymethylammonium, dibutyiammonium, methyibutylammonium, anslinium, pyridinium, 2-rrsethy!pyridsnium, imidazolium, 1-methylimidazoiium, 1 ,2- dimethylimsdazolium, imidazolinium, 1-ethylimidazolium, 1-(4-suifobutyl)-3-methylimidazoiium, 1-allylimid
  • the cation is 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-butyl-1- methylpyrrolidinium or trihexyl(tetradecyl)phosphonium.
  • electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of carboxylates, imides, methides, nitrate, bifluoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aluminates.
  • E20 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of
  • y is an integer of 1 to 6
  • z is an integer of 1 to 4,
  • X is B or Al and R w , Rx, R y and R z are independently halogen, Ci-C 20 alkyi, CrC 2 oalkyi which Is partly or fully fluorinated, CrC 2 oaikoxy, CrC 2 oalkoxy which is partly or fully fiuorinated, Ci-C 2 oalkyl-COO or CrC 2 oalkyl-COO which is partly or fully fluorinated and
  • ⁇ is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxyiic acid or from a 1 ,2- or 1 ,3-hydroxycarboxylic acid and
  • any one CF 2 group may be replaced by O, S(0) 2 , NR or CH 2 .
  • the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of F 2 P(C 2 F 5 ) 4 -, F 3 P(C 2 F 5 )3-, F 4 P(C 2 F 5 ) 2 -, F 2 P(C 3 F 7 ) 4 -, F 3 P(C3F 7 )3 ' , F 4 P(C 3 F 7 ) 2 -, F 2 P(C 4 Fg)4-,
  • the electrolyte composition comprises an ionic compound containing a carboxylate anion of formula RCQO where R is hydrogen or hydrocarbyl; such as formate, acetate (ethanoate), acrylate, propanoate, n- butanoate, i ⁇ butanoate, n ⁇ pentanoate, i ⁇ pentanoate, octanoate, decanoate, benzoate, salicylate, thiosalicylate, 2-, 3- or 4-nitrobenzoate; citrate, oxalate, tartrate, giycolate, gluconate, ma!ate, mandeiate, a carboxylate of nitrilotriacetic acid, a carboxylate of N-(2-hydroxyethyi)- ethylenediaminetriacetic acid, a carboxylate of ethylenediaminetetraacetic acid, a carboxylaie of diethylenetri
  • an imide anion such as dicyanamide, N(S0 2 F) 2 " ((bisfluorosulfonyl)imide), a
  • bis(perfluoroaikylsulfonyl)imide such as [N(SG 2 CF 3 ) 2 j ⁇ (bistriflimide),
  • a methide such as a tris(perfluoroalkylsulfonyl)methide, for example
  • borate such as orthoborate, tetrahydroxyborate, tetraborate, tetraphenylborate, [B(3,5- (CF 3 ) 2 C S H 3 ) 4 ]- (BARF), B(C 2 0 4 ) 2 ⁇ (bis(oxa!ato)borate) (BOB), difiuoro(oxa!ato)borate (dFOB), di(trifluoroacetato)oxalatoborate (D(Ac)OB), or BF 4 ⁇ (tetrafluoroborate); or
  • fluoro(perfluoroalkyl)phosphate such as F2P(C2Fs)4 ⁇ , F 3 P(C2Fs) 3 ⁇
  • a sulfonate such as an a!kylsulfonate, arylsulfonate or perfluoroalkylsulfonate, for instance trif!uoromethanesu!fonate (triflate), p ⁇ toluenesulfonate (tosylate) or methanesuifonate
  • a sulfate such as hydrogensuifate, sulfate, thiosulfate or an aikylsuifate such as methylsuifate or ethylsulfate; or
  • a carbonate anion such as carbonate, hydrogencarbonate or an alkylcarbonate such as methyicarbonate, ethylcarbonate or butylcarbonate; or
  • an aluminate such as AI(OC(CF 3 ) 3 ) 4 ⁇ di(trifluoroacetato)oxa!atoaluminate (d(Ac)OAI), tetrachloroaluminate, tetrafluoroaluminate, tetraiodoaluminate or tetrabromoaiuminate.
  • E24 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid.
  • E25 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of diethylmethyiammonium trifluoromethanesulfonate (DEMA TfO), ethylammonium nitrate, triethylammonium
  • DEMA TfO diethylmethyiammonium trifluoromethanesulfonate
  • ethylammonium nitrate triethylammonium
  • methanesuifonate 2-methylpyridinium trifluoromethanesulfonate, ammonium fluoride, methylammonium nitrate, hydroxyethylammonium nitrate, ethylammonium nitrate,
  • dimethylammonium nitrate 1-methyiimidazoiium nitrate, 1-ethylimidazolium nitrate, t- butylammonium tetrafluoroborate, hydroxyethylammonium tetrafluoroborate,
  • methoxyethyiammonium mesylate dimethylammonium mesylate, dibutylammonium mesylate, triethylammonium mesylate, dimethylethylammonium mesylate, hydronium hydrogensuifate, ammonium hydrogensulfate, methy!ammonium hydrogensulfate, ethylammonium hydrogensulfate, propylammonium hydrogensulfate, n ⁇ butylammonium hydrogensulfate, t ⁇ buiylammonium hydrogensulfate, dimethylammonium hydrogensulfate, diethylammonium hydrogensulfate, di-n-butylammonium hydrogensulfate, methylbuiylammonium hydrogensulfate, ethylbutyiammonium hydrogensulfate, trimethyiammonium hydrogensuifate, triethylammonium hydrogensuifate, tribut
  • methoxyefhylammonium dihydrogen phosphate dimethylammonium dihydrogen phosphate, dibutylammonium dihydrogen phosphate, methylbuiylammonium dihydrogen phosphate, ammonium bifluoride, methyiammonium bifiuoride, ethylammonium bifluoride and
  • the electrolyte composition comprises an ionic liquid selected from the group consisting of 1-ethyl-3-methylimidazoiium trifiuoromethanesuifonate (EMIM TfO), 1-ethyi-3-methylimidazolium fetrafluoroborate (EMI BF 4 ), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI), 1 -ethyl-3- methylimidazolium acetate (EMIM Ac), 1-butyl-3-methylimidazolium trifiuoromethanesuifonate (BMIM TfO), 1-butyi ⁇ 3-methylimidazolium acetate (BMIM Ac), 1-bufyl ⁇ 3 ⁇ methyiimidazoiium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), tri-n-buty
  • tributylmethylphosphonium dibutyiphosphate triethylmethylphosphonium dibutyiphosphate, tetrabutylphosphonium teirafluoroboraie, tetrabutylphosphonium p-toluenesulfonate, tributylmethylphosphonium meihylcarbonate, 1-ethyi-3-methylimidazolium hydrogencarbonate, iributyimethyiammonium methyicarbonate, iributyimethyiammonium dibutyiphosphate, 1 -ethyl-3- methylimidazoiium dibutyiphosphate, 1-butyl-3-methylimidazolium dibutyiphosphate, 1- (cyanomethyl)-3-methylimidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-methylimidazolium bis(irifi
  • ihe electrolyte composition comprises a proiic acid; for example a protic acid such as
  • hydrochloric acid nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid or periodic acid; or
  • a bisulfaie such as sodium bisulfaie, potassium bisulfate or ammonium bisulfate;
  • HAsFs HBF 4 , H(OEt 2 )BF 4 , HPF 6 , ,H[N(S0 2 CF 3 )2] or H[N(S0 2 CF 2 CF 3 )2].
  • E28 A cell according to any of the preceding embodiments where the electrolyte composition comprises an organic proiic acid such as a carboxylic acid of formula RCOOH where R is hydrogen or hydrocarbyl, for example formic acid, acetic acid, acrylic acid, fluoroacetic acid, difiuoroacetic acid, trifluoroacetic acid, chloroacetic acid, dichioroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methylbutanoic acid, valeric acid, hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- or 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, giycolic acid, gluconic acid, malic acid, mandelic acid, nitrilotriacetic acid, N-(2-hydroxyethyl)-efhylenediamine
  • E29 A cell according to any of the preceding embodiments where the electrolyte composition comprises a protic sulfonic acid of formula RSO3H where R is alkyi or aryi or alkyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsulfonic acid, methanesuifonic acid or trifiuoromethanesuifonic acid.
  • RSO3H where R is alkyi or aryi or alkyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsulfonic acid, methanesuifonic acid or trifiuoromethanesuifonic acid.
  • the electrolyte composition comprises a protic acid which is an oxonium ion associated with a highly non-coordinating ion such as Brookhart's acid (BARF acid), [H(OEt 2 )2][B[3,5-(CF3)2C 6 H 3 ] 4 ], [H(OEt2)2][B(C 6 F s )4]
  • BARF acid Brookhart's acid
  • E31 A cell according to any of the preceding embodiments where the electrolyte composition comprises at least two different ionic compounds; for example, where the electrolyte
  • composition comprises
  • a salt and an ionic liquid for example a protic or aprotic ammonium salt or an alkali metal salt such as an aikai metal halide;
  • a protic acid, protic ammonium compound or a protic oxonium compound and an ionic liquid for example a carboxylic acid and an ionic liquid.
  • E32 A cell according to any of the preceding embodiments where the electrolyte composition comprises two different ionic compounds which contain an identical cation or an identical anion.
  • E33 A ceil according to any of the preceding embodiments where electrolyte composition comprises two different ionic compounds with a weighfcweight ratio of from about 99.9:0.1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
  • E34 A weighfcweight ratio of from about 99.9:0.1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about
  • E38 A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of water.
  • E37 A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of organic solvent.
  • a ceil according to embodiment 38 where the weight:weight ratio of wafer to organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
  • organic solvent comprises one or more solvents selected from the group consisting of organic carbonates, ethers, giymes, ortho esters, polyalklene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents and nitrile solvents.
  • an organic carbonate for example a cyclic or acyclic organic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), trimethyiene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), vinylene carbonate, difluoroethyiene carbonate or monofiuoroethyiene carbonate; or
  • EC ethylene carbonate
  • PC propylene carbonate
  • trimethyiene carbonate 1 ,2-butylene carbonate
  • BC dimethyl carbonate
  • DMC diethyl carbonate
  • EMC ethylmethyl carbonate
  • vinylene carbonate difluoroethyiene carbonate or monofiuoroethyiene carbonate
  • an ether or glyme such as dimethoxymethane (DMM), diethoxymethane, 1 ,2-dimetboxyethane (DME or ethyieneglycoi dimethyiether or glyme), diglyme, triglyme, tetragiyme, ethyienegiycoi diethylether (DEE), ethyieneglycoi dibufylether, diethyieneglycol diefhylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1 ,3-dioxane, 1 ,3-dioxolane (DIOX), 4-methyl-1 ,3- dioxolane (4-MeDIOX), 2-metbyi-1 ,3-dioxoiane (2- eDIOX), 1 ,4-dioxane, dimethyiether, e
  • a polyalkylene glycol that is a homo- or cooiigomer or homo- or copolymer of Crdalkylene glycols, such as polyethylene glycol (PEG) or monomethyl, dimethyl or diethyl (end-capped) polyethylene glycol with weight average molecular weights (Mw) for example from about 200 to about 1200 g/mol, from about 200 to about 1000 g/mol, from about 200 to about 900 g/mol, from about 200 to about 700 g/mol or from about 200 to about 500 g/mol, for example oligomers of 4 monomers or more, for instance tetraethyiene glycol, fiuorinated tetraethylene glycol or tetrapropylene glycol, for instance PEG 200, PEG 300, PEG 400, PEG 500, PEG 600, PEG 700, PEG 800, PEG 900 or PEG 1000; or
  • an ester or lactone such as ⁇ -butyrolactone (GBL), ⁇ -valerolactone, ⁇ -valerolactone, ethyl acetate (EA), 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethy!
  • acetate 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EGDA), 3-ethoxy ethyl propionate (EEP), methyl butyrate ( B), n-amyl acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate or dimethyl malonate; or
  • a dibasic ester mixture such as methyl esters of adipic, glutaric or succinic acids; or
  • a glycol such as ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2- propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol (ethylene glycol butyl ether, EB), 2- phenoxyethanol, 2-benzyloxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol (diethylene glycol butyl ether, DB), propylene glycol butyl ether (PB), propylene glycol methyl ether (PM), Methylene glycol (TEG), dipropylene glycol methyl ether (DPM), diethylene glycol methyl ether, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, perfiuoro-1 ,4-butanediol, perfluoro-1 ,5-butanediol, fiu
  • a formate such as methyl formate, ethyl formate, isobutyi formate or tert-butyl formate; or a sulfone or sulfoxide such as methylsulfonyl methane (MSM or dimethylsuifone),
  • an amide such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methylpyrrolidone (NMP), 2-pyrrolidone, 1 ,3 ⁇ dimethyl-2-imidazo!idinone (DMl), hexamethyiphosphoramide (HMPA) or N,N'-dimethyl-N,N'-trimethyleneurea (1 ,3-dimethyl-3,4,5,6-tetrahydro-2(1 H)- pyrimidinone (DMPU)); or
  • an alcohol such as benzylalcohol (BA), ethanol, trifluoroethanol (2,2,2-trifluoroethanol), methanol, isopropanoi, t-butanol or n-butanol; or a ketone such as methylethylketone (MEK) or methyl-isoamylketone (MIAK); or a nitro solvent such as nitrobenzene, nitromethane or nitroethane; or
  • BA benzylalcohol
  • MEK methylethylketone
  • MIAK methyl-isoamylketone
  • a nitrile solvent such as acetonitrile, propionitrile, butyronitrile or adiponitrile.
  • E42 A cell according to any of embodiments 1-33 and 35-41 where the electroiyte composition comprises a solvent and where the weigh weight ratio of ionic compounds in total to solvent is from about 99.9:0,1 to about 0, 1 :99.9, from about 99.5:0.5 to about 0,5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
  • electrolyte composition further comprises one or more additives selected from the group consisting of corrosion inhibitors, solid electrolyte interface (SEI) improvers, proton evolution improvers, self-discharge inhibitors, anti- gassing agents, viscosity adjusting agents, cathode protection agents, salt stabilizers, conductivity improvers and solvating agents.
  • SEI solid electrolyte interface
  • E44 A cell according to any of embodiments 1-43 where the electrolyte composition contains one or more additives selected from the group consisting of
  • fluorinated oil sodium stannate, sodium citrate or poiyacrylic acids
  • HF or KF oxides or hydroxides of rare earths such as Y, metal porphsnes, for example Ni or Fe porphine, vinyiene carbonate, vinyiethylene carbonate, methylene ethylene carbonate or fluoro- ethylene carbonate;
  • poiyglycois, poiygiycoi alky! ethers, polyglycol alky! phosphate esters or polysorbates such as polyethylene glycol (PEG), polypropylene glycol, poiysorbate 20, polysorbate 40 or polysorbate 80 or a mixture of PEG 600 and poiysorbate 20 or a mixture of PEG 600 and ZnO;
  • phosphate ester-based surfactants propane sultone or fluoropropane sultone
  • the electrolyte composition for example at a level of from about 0.1 % to about 15% by weight, based on the total weight of the electrolyte composition.
  • a rechargeable electrochemical ceil according to any of the preceding embodiments comprising a positive electrode, a casing having the electrodes positioned therein and the electrolyte composition in contact with the electrodes, where the gravimetric energy density of the ceil is > 100 Wh/kg, > 1 10 Wh/kg, > 1 15, > 120, > 125, > 130, > 135, > 140, > 145, > 150, > 155, > 160, > 165, > 170, > 175, > 180, > 185, > 190, > 195 or > 200 Wh/kg and/or
  • volumetric energy density of the cell is > 250 Wh/L, for instance, ⁇ 260 Wh/kg, ⁇ 265,
  • the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 cycles or more (over at least 20 cycles), for example > 810, > 820, > 825, > 830, > 835, > 840, > 845, > 850, > 855, > 860, > 865, > 870, > 875, > 880 or > 895 mAh/g over 20 cycles or more.
  • a rechargeable electrochemical cell according to any of the preceding embodiments comprising a positive electrode, a casing having the electrodes positioned therein and the electrolyte composition in contact with the electrodes, where the reversible half cell
  • /V is a group IV element-based hydrogen storage material
  • Si is a silicon-based hydrogen storage material
  • a cell according to any of the preceding embodiments comprising a positive electrode, the positive electrode comprising one or more cathode active materials selected from the group consisting of transition metals, transition metal oxides, transition metal hydroxides, transition metal oxide/hydroxides and transition metal fluorides; for example one or more materials selected from the group consisting of
  • a rechargeable electrochemical cell comprising a stable group IV element-based hydrogen storage negative electrode; for example a stable silicon-based or carbon-based hydrogen storage negative electrode; for example where the negative electrode comprises a hydrogen storage material comprising > 27 wt% or one or more elements selected from the group consisting of C, Si, Ge and Sn, based on the total weight of the hydrogen storage material; the cell also comprising a positive electrode, a casing having the electrodes positioned therein and an electrolyte composition in contact with the electrodes, where the reversible half cell charge/discharge electrochemical reaction at the negative electrode is
  • IV is a group IV element-based hydrogen storage material
  • Si is a silicon-based hydrogen storage material.
  • a cell according to embodiments 1 or 2 where the hydrogen storage material comprises amorphous silicon, microcrystalline silicon, nanocrystalline silicon, monocrysfaliine silicon, polycrystalline silicon, protocrystailine silicon or porous silicon.
  • the hydrogen storage material comprises carbon; for example carbon in the form of natural graphite, artificial graphite, expanded graphite, graphene, carbon fiber, hard carbon, soft carbon, non-graphitizabie carbon, carbon black, carbon nanoiube, fullerene, activated carbon, crystalline carbon or amorphous carbon.
  • the hydrogen storage material comprises an alloy of silicon and one or more of carbon, germanium and fin, for example amorphous silicon carbide or an alloy of silicon and germanium or an alloy of silicon and tin.
  • the hydrogen storage material is hydrogenated prior to assembly of the cell (a pre-hydrogenated negative electrode); for example where the hydrogen storage material is hydrogenated amorphous silicon (a-Si:H) or hydrogenated amorphous silicon carbide (a-Sii.. x C x :H, where x is for example from about 0.01 to about 0.99, from about 0.05 to about 0.95 or from about 0.1 to about 0.9).
  • the hydrogen storage material for example amorphous silicon
  • E9 A cell according to any of the preceding embodiments where the hydrogen storage material is comprised in a film in adherence to a substrate, for example a substrate selected from metal, glass, inorganics and plastic.
  • the hydrogen storage material comprises one or more further elements, for example one or more elements selected from the group consisting B, Al, Ga, In, As, Sb, Te and transition metals.
  • the hydrogen storage material contains > 28 wt%, ⁇ 29 wt%, > 30 wt%, ⁇ 35 wt%, ⁇ 40 wt%, > 45 wt%, ⁇ 50 wt%, ⁇ 55 wt%, > 60 wt%, > 65 wt%, > 70 wt%, > 75 wt%, > SO wt%, > 85 wt%, > 90 wt%, > 95 wt%, > 96 wt%, > 97 wt%, > 98 wt% or > 99 wt% of one or more elements selected from the group consisting of group IV elements, for example Si and/or C, based on the total weight of the hydrogen storage material.
  • group IV elements for example Si and/or C
  • the negative electrode comprises > 30% by weight of the one or more group IV elements; for example > 35%, > 40%, > 45%, > 50%, > 55%, > 60%, ⁇ 65%, ⁇ 70%, ⁇ 75% > 80%, ⁇ 85% or > 90% by weight of the one or more group IV elements, for example Si and/or C, based on the total weight of the negative electrode.
  • the hydrogen storage material includes one or more further elements selected from the group consisting of structural modifiers (elements to promote the amorphous phase of a material), hydrogen bond strength modifiers and solid electrolyte interface (SEI) modifiers; for example one or more further elements selected from the group consisting of B, alkaline earth metals, transition metals, rare earth metals, other metals of groups HI or V of the periodic table, O, F, P, CI and the like.
  • structural modifiers elements to promote the amorphous phase of a material
  • SEI solid electrolyte interface
  • E16 A ceil according to any of the preceding embodiments where the electrolyte composition which is neutral or acidic, for example having a pH of about 7 or lower; for example from about 1 , from about 2, from about 3, from about 4, from about 5 or from about 6 to about 7.
  • E17 A cell according to any of the preceding embodiments where the electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, protic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotic oxonium compounds, aprotic phosphonium compounds and alkali or alkali earth metal salts.
  • the electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, protic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotic oxonium compounds, aprotic phosphonium compounds and alkali or alkali earth metal salts.
  • the electrolyte composition comprises an ionic compound containing a cation selected from the group consisting of NH 4 + (ammonium), methylammonium, ethylammonium, dimethylammonium, diethylammonium, trimethylammonium ( ⁇ 3 ⁇ + ), triethylammonium, tributylammonium, diethylmethylammoniurrs, hydroxyethylammonium, meihoxymeihylammonium, dibuiylammonium, methylbutylammonium, anilinium, pyridinium, 2-methylpyridinium, imidazoiium, 1-methylimidazolium, 1 ,2- dimethylimidazolium, imidazolinium, 1-ethylimidazolium, 1-(4-sulfobutyl)-3-methylimidazolium, 1-allylimidazolium, quinolinium, NH 4 + (ammonium), methylammoni
  • tributylmethylphosphonium triethylmethylphosphonium, trihexyltetradecylphosphonium, triphenylpropylphosphonium or tetrakis(hydroxymethyl)phosphonium;
  • the cation is 1-ethyl-3-methylimidazoiium, 1-hexyl-3-methylimidazolium, 1-butyl-1- methylpyrrolidinium or trihexyl(tetradecyl)phosphonium.
  • electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of carboxylates, imides, methides, nitrate, bifluoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aluminates.
  • E20 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of
  • y is an integer of 1 to 6
  • n is an integer of 1 to 8, for instance 1 to 4,
  • z is an integer of 1 to 4,
  • X is B or Al
  • Rw, Rx, R y and R z are independently halogen, CrC 2 oaikyi, CrC 2 oalkyi which is partly or fully fluorinated, CrC 2 oalkoxy, CrC 20 alkoxy which is partly or fully fluorinated, Ci ⁇ C 20 alkyl ⁇ COO or CrC 2 oalkyl-COO which is partly or fully fluorinated and
  • 0 "" 0 is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxylic acid or from a 1 ,2- or 1 ,3-hydroxycarboxylic acid and
  • any one CF 2 group may be replaced by O, S(0) 2 , NR or CH 2 .
  • E21 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of F 2 P(C 2 Fs)4-,
  • BOB bisoxalatoborate
  • dFOB difluoro
  • E22 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing a carboxylate anion of formula RCOO " where R is hydrogen or hydrocarbyl; such as formate, acetate (ethanoate), acrylate, propanoate, n- butanoate, i ⁇ butanoate, n ⁇ pentanoate, i ⁇ pentanoate, octanoate, decanoate, benzoate, salicylate, thiosalicylate, 2-, 3- or 4-nitrobenzoate; citrate, oxalate, tartrate, giycolate, gluconate, ma!ate, mandelate, a carboxylate of nitrilotriacetic acid, a carboxylate of N-(2-hydroxyethyl)- ethylenediaminetriacetic acid, a carboxylate of ethylenediaminetetraacetic acid, a carboxylate of diethylenetriaminepenta
  • E23 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing
  • an imide anion such as dicyanamide, N(SQ 2 F) 2 "" ((bisfluorosulfonyl)irnide), a
  • bis(perfiuoroaikylsulfonyi)imide such as [N(S0 2 CF 3 ) 2 ]- (bistriflimide),
  • a methide such as a tris(perfluoroalkylsulfonyl)methide, for example
  • a borate such as orthoborate, tetrahydroxyborafe, tetraborate, tetraphenylborate, [B(3,5- (CF 3 )2CeH 3 )4]- (BARF), B(C 2 0 4 ) 2 - (bis(oxalato)borate) (BOB), difluoro(oxalato)borate (dFOB), di(trifluoroacetato)oxalatoborate (D(Ac)OB), B(C 6 F S )4 ⁇ or BF 4 ⁇ (fetrafluoroborate); or
  • a phosphate such as dihydrogen phosphate, hydrogen phosphate, alkyi phosphate, dialkyi phosphate, phosphate, PF 6 " (hexafiuorophosphate), HP0 3 F ⁇ (fiuorohydrogen phosphate), trisoxalatophosphate (TOP), tetrafluorooxalatophosphate (TFOP) or a
  • fiuoro(perfluoroalkyi)phosphate such as F 2 P(C 2 F S )4 " , F 3 P(C 2 Fs) 3 "
  • a sulfonate such as an alkylsulfonate, arylsulfonate or perfluoroalkylsulfonate, for instance trifiuoromethanesuifonate (triflate), p-toiuenesuifonate (tosylate) or mefhanesulfonafe
  • a sulfate such as hydrogensulfate, sulfate, thiosuifate or an alkyisulfate such as mefhylsuifate or ethyl sulfate; or
  • a carbonate anion such as carbonate, hydrogencarbonate or an alkylcarbonate such as methylcarbonate, ethyicarbonate or butylcarbonate; or
  • an aluminate such as AI(OC(CF 3 ) 3 ) 4 ⁇ di(trifluoroacetato)oxalatoaluminate (d(Ac)OAI), tetrach!oroaluminate, tetraf!uoroa!uminate, tetraiodoaluminate or tetrabromoaluminate.
  • E25 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of diethylmethylammonium trifiuoromethanesuifonate (DE A TfO), ethylammonium nitrate, triethylammonium
  • DE A TfO diethylmethylammonium trifiuoromethanesuifonate
  • ethylammonium nitrate triethylammonium
  • methanesulfonate 2-methylpyridinium trifiuoromethanesuifonate, ammonium fluoride, methylammonium nitrate, hydroxyethylammonium nitrate, ethylammonium nitrate,
  • dimethylammonium nitrate 1-meihylimidazoiium nitrate, 1-ethylimidazolium nitrate, i- butylammonium tetrafiuoroborate, hydroxyethylammonium tetrafluoroborate,
  • meihoxyeihyiammonium mesylate dimethylammonium mesylate, dibutyiammonium mesylate, triethylammonium mesylate, dimethylethyiammonium mesylate, hydronium hydrogensulfate, ammonium hydrogensulfate, methylammonium hydrogensulfate, ethylammonium
  • meihoxyeihyiammonium dihydrogen phosphate dimethylammonium dihydrogen phosphate, dibutyiammonium dihydrogen phosphate, methylbutyiammonium dihydrogen phosphate, ammonium bifluoride, methylammonium bifiuoride, ethylammonium bifluoride and
  • E26 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of 1-ethyl-3-methylimidazolium trifiuoromethanesuifonate (EMIM TfO), 1-ethyi-3-methylimidazolium tetrafluoroborate (EMIM BF4), 1-ethyl-3-methylimidazolium bis(trifiuoromethylsulfonyl)imide (EMIM TFSI), 1-ethyi-3- methylimidazolium acetate (EMI Ac), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIM TfO), 1-butyl ⁇ 3-methylimidazolium acetate (BMIM Ac), 1-butyl ⁇ 3 ⁇ methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), tri-n-butylmethylammonium methyls
  • tributylmethylphosphonium dibutylphosphate triethylmethylphosphonium dibutylphosphate, teirabutylphosphonium ieirafiuoroboraie, teirabutylphosphonium p-toluenesulfonate, tributylmethylphosphonium meihyicarbonate, 1-ethyi-3-meihylimidazolium hydrogencarbonate, tributylmethylammonium meihyicarbonate, tributylmethylammonium dibutylphosphate, 1 -ethyl-3- methyiimidazoiium dibutylphosphate, 1-butyl-3-methylimidazolium dibutylphosphate, 1- (cyanomeihyl)-3-meihylimidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-meihyiimi
  • E27 A cell according to any of the preceding embodiments where the electrolyte composition comprises a protic acid; for example a protic acid such as
  • hydrochloric acid nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid or periodic acid; or
  • a bisulfate such as sodium bisulfate, potassium bisulfate or ammonium bisulfate; or
  • HAsFs HBF 4 , H(OEt 2 )BF 4 , HPF 6 , ,H[N(S0 2 CF 3 ) 2 ] or H[N(S0 2 CF 2 CF 3 )2].
  • E28 A cell according to any of the preceding embodiments where the electrolyte composition comprises an organic protic acid such as a carboxylic acid of formula RCOOH where R is hydrogen or hydrocarbyi, for example formic acid, acetic acid, acrylic acid, fiuoroacefic acid, difluoroacetic acid, trifluoroacetic acid, chioroacetic acid, dichioroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methylbutanoic acid, valeric acid, hexanoic acid, hepfanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- or 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, giycolic acid, gluconic acid, malic acid, mandelic acid, nitriiotriacefic acid, N-(2 ⁇ hydroxyethyl) ⁇ ethylenediaminetriacetic acid,
  • the electrolyte composition comprises a protic sulfonic acid of formula RSO3H where R is alkyi or aryi or aikyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsuifonic acid, methanesuifonic acid or trifiuoromethanesuifonic acid.
  • the electrolyte composition comprises a protic acid which is an oxonium ion associated with a highly non-coordinating ion such as Brookhart's acid (BARF acid), [H(OEt2)2][B[3,5-(CF3)2CeH 3 ]4], [H(OEt 2 ) 2 l[B(CsF 5 ) 4 ] (oxonium acid) or [H(OEt 2 ) 2 ][AI(OC(CF 3 ) 3 ) 4 ].
  • BARF acid Brookhart's acid
  • H(OEt2)2][B[3,5-(CF3)2CeH 3 ]4 [H(OEt 2 ) 2 l[B(CsF 5 ) 4 ] (oxonium acid) or [H(OEt 2 ) 2 ][AI(OC(CF 3 ) 3 ) 4 ].
  • composition comprises a protic ionic compound and an aprotic ionic compound
  • a salt and an ionic liquid for example a protic or aprotic ammonium salt or an alkali metal salt such as an aikai metal halide;
  • a protic acid, protic ammonium compound or a protic oxonium compound and an ionic liquid for example a carboxyiic acid and an ionic liquid.
  • E32 A cell according to any of the preceding embodiments where the electrolyte composition comprises two different ionic compounds which contain an identical cation or an identical anion, E33.
  • E34 A ceil according to any of the preceding embodiments where the electrolyte composition contains no organic solvent and ⁇ 1000 ppm, ⁇ 100 ppm or ⁇ 10 ppm water by weight, based on the total weight of the electrolyte composition; or where the electrolyte composition contains ⁇ 9, ⁇ 8, ⁇ 7, ⁇ 6, ⁇ 5 or ⁇ 4 ppm water by weight, based on the total weight of the electrolyte composition.
  • E36 A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of water.
  • E37 A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of organic solvent.
  • a ceil according to embodiment 38 where the weight:weight ratio of water to organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about E40.
  • organic solvent comprises one or more solvents selected from the group consisting of organic carbonates, ethers, giymes, ortho esters, polyalklene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents and nitrile solvents.
  • a cell according to embodiment 40 where the electrolyte composition comprises an organic solvent such as
  • an organic carbonate for example a cyclic or acyclic organic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), trimetbylene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyimethyi carbonate (EMC), vinylene carbonate, difluoroethylene carbonate or monofluoroethylene carbonate; or
  • an ether or giyme such as dimethoxymethane (DMM), diethoxymethane, 1 ,2-dimethoxyefhane (DME or ethyleneglycol dimethyiether or glyme), diglyme, trigiyme, tetragiyme, ethyleneglycol diethylether (DEE), ethyleneglycol dsbutylether, dsethyieneglycol diethylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1 ,3-dioxane, 1 ,3-dioxolane (DIOX), 4-methyl-1 ,3- dioxolane (4-MeDIOX), 2-methyl-1 ,3-dioxoiane (2-MeDIOX), 1 ,4-dioxane, dimethyiether, ethylmethylether, diethyl
  • an ortho ester such as trimethoxymethane, trsethoxymethane, 1 ,4-dimethyl-3,5,8- trioxabicyclo[2.2.2]octane or 4-ethyl-1-methyl-3,5,8-trioxabicyclo[2.2.2]octane; or
  • a polyalkyiene glycol that is a homo- or cooligomer or homo- or copolymer of CrC 4 aikyiene glycols, such as polyethylene glycol (PEG) or monomethy!, dimethyl or diethyl (end-capped) polyethylene glycol with weight average molecular weights (Mw) for example from about 200 to about 1200 g/mol, from about 200 to about 1000 g/mol, from about 200 to about 900 g/mol, from about 200 to about 700 g/mol or from about 200 to about 500 g/mol, for example oligomers of 4 monomers or more, for instance tetraethylene glycol, fluorinated tetraethylene glycol or tetrapropylene glycol, for instance PEG 200, PEG 300, PEG 400, PEG 500, PEG 600, PEG 700, PEG 800, PEG 900 or PEG 1000; or
  • an ester or lactone such as ⁇ -butyrolactone (GBL), ⁇ -valerolactone, ⁇ -valerolactone, ethyl acetate (EA), 2-methoxyethyl acetate, 2-ethoxyethyi acetate, 2-butoxyethyl acetate, 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EGDA), 3-ethoxy ethyl propionate (EEP), methyl bufyrate (MB), n-amy! acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate or dimethyl malonate; or
  • GBL ⁇ -butyrolactone
  • EA ethyl acetate
  • 2-methoxyethyl acetate 2-ethoxyethyi
  • a dibasic ester mixture such as methyl esters of adipic, glutaric or succinic acids; or a glycol such as ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2- propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol (ethylene glycol butyl ether, EB), 2- phenoxyethanol, 2-benzyloxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol (diethylene glycol butyl ether, DB), propylene glycol butyl ether (PB), propylene glycol methyl ether (PM), triethylene glycol (TEG), dipropylene glycol methyl ether (DPM), diethylene glycol methyl ether, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, perfluoro-1 ,4
  • a formate such as methyl formate, ethyl formate, isobutyl formate or tert-butyl formate; or a sulfone or sulfoxide such as methylsulfonylmethane ( SM or dimethy!su!fone),
  • an amide such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methyipyrroiidone (NMP), 2-pyrrolidone, 1 ,3-dimethyl-2-imidazolidinone (DMI), hexamethylphosphoramide (H PA) or N.N'-dimethyl-N.N'-trimethyleneurea (1 ,3 ⁇ dimethyl-3,4,5,6 etrahydro-2(1 H)- pyrimidinone (DMPU)); or
  • an alcohol such as benzylalcohoi (BA), ethanol, trifluoroethanol (2,2,2-trifluoroethanol), methanol, isopropanol, t-butanol or n-butanol; or
  • a ketone such as methylethylketone (MEK) or methyl-isoamylketone (MIAK); or
  • a nitro solvent such as nitrobenzene, nitromethane or nitroethane; or
  • a nitrile solvent such as acetonitriie, propionitrile, butyronitrile or adiponitrile.
  • E42 A ceil according to any of embodiments 1-33 and 35-41 where the electrolyte composition comprises a solvent and where the weightweight ratio of ionic compounds in total to solvent is from about 99.9:0,1 to about 0, 1 :99.9, from about 99.5:0.5 to about 0,5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
  • electrolyte composition further comprises one or more additives selected from the group consisting of corrosion inhibitors, solid electrolyte interface (SEI) improvers, proton evolution improvers, self-discharge inhibitors, anti- gassing agents, viscosity adjusting agents, cathode protection agents, salt stabilizers, conductivity improvers and solvating agents.
  • SEI solid electrolyte interface
  • E44 A cell according to any of embodiments 1-43 where the electrolyte composition contains one or more additives selected from the group consisting of
  • fluorinated oil sodium stannate, sodium citrate or poiyacryiic acids
  • HF or KF oxides or hydroxides of rare earths such as Y, metal porphines, for example Ni or Fe porphine, vinylene carbonate, vinylethylene carbonate, methylene ethylene carbonate or fluoro- ethylene carbonate;
  • polyglycols poiygiycoi alkyl ethers, polyglycol aiky! phosphate esters or polysorbates such as polyethylene glycol (PEG), polypropylene glycol, poiysorbate 20, polysorbate 40 or polysorbaie 80 or a mixture of PEG 600 and poiysorbate 20 or a mixture of PEG 600 and ZnO;
  • PEG polyethylene glycol
  • polypropylene glycol poiysorbate 20
  • polysorbate 40 or polysorbaie 80 or a mixture of PEG 600 and poiysorbate 20 or a mixture of PEG 600 and ZnO
  • phosphate ester-based surfactants propane sultone o fluoropropane sultone
  • the electrolyte composition for example at a level of from about 0.1 % to about 15% by weight, based on the total weight of the electrolyte composition.
  • a rechargeable electrochemical ceil according to any of the preceding embodiments comprising a positive electrode, a casing having the electrodes positioned therein and the electrolyte composition in contact with the electrodes, where the gravimetric energy density of the ceil is > l OO Wh/kg, > 1 10 Wh/kg, > 1 15, > 120, > 125, > 130, > 135, > 140, > 145, > 150, > 155, > 160, > 165, > 170, > 175, > 180, > 185, > 190, > 195 or > 200 Wh/kg and/or
  • volumetric energy density of the ceil is > 250 Wh/L, for instance, > 260 Wh/kg, > 265,
  • the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 cycles or more (over at least 20 cycles), for example > 810, > 820, > 825, > 830, > 835, > 840, > 845, > 850, > 855, > 860, > 865, > 870, > 875, > 880 or > 895 mAh/g over 20 cycles or more.
  • a ceil according to any of the preceding embodiments comprising a positive electrode, the positive electrode comprising one or more cathode active materials selected from the group consisting of transition metals, transition metal oxides, transition metal hydroxides, transition metal oxide/hydroxides and transition metal fluorides; for example one or more materials selected from the group consisting of
  • a rechargeable electrochemical cell comprising a stable group IV element-based hydrogen storage negative electrode; for example a stable silicon-based or carbon-based hydrogen storage negative electrode; for example where the electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn, based on the total weight of the hydrogen storage material;
  • the cell also comprising a positive electrode, a casing having the electrodes positioned therein and an electrolyte composition in contact with the electrodes,
  • the gravimetric energy density of the cell is > 100 Wh/kg, > 1 10 Wh/kg, > 115, > 120, > 125, > 130, > 135, > 140, > 145, > 150, > 155, > 160, > 165, > 170, > 175, > 180, > 185, > 190, > 195 or > 200 Wh/kg and/or
  • volumetric energy density of the ceil is > 250 Wh/L, for instance, > 260 Wh/kg, > 265,
  • the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 cycles or more (over at least 20 cycles), for example > 810, > 820, > 825, > 830, > 835, > 840, > 845, > 850, > 855, > 860, > 865, > 870, > 875, > 880 or > 895 mAh/g over 20 cycles or more.
  • a ceil according to embodiments 1 or 2 where the hydrogen storage material comprises amorphous silicon, microcrystaliine silicon, nanocrystaliine silicon, monocrystailine silicon, polycrystalline silicon, protocrystaliine silicon or porous silicon.
  • the hydrogen storage material comprises carbon; for example carbon in the form of natural graphite, artificial graphite, expanded graphite, graphene, carbon fiber, hard carbon, soft carbon, non-graphitizable carbon, carbon black, carbon nanotube, fullerene, activated carbon, crystalline carbon or amorphous carbon.
  • the hydrogen storage material comprises an alloy of silicon and one or more of carbon, germanium and tin, for example amorphous silicon carbide or an alloy of silicon and germanium or an alloy of silicon and tin.
  • the hydrogen storage material for example amorphous silicon
  • a film for example a film with a thickness > 20 nm, > 50 nm, > 90 nm, > 120 nm or > 180 nm or from about 90 nm to about 10 ⁇ , from about 100 nm to about 5 ⁇ , from about 150 nm to about 3 ⁇ , from about 150 nm to about 2 ⁇ or from about 150 nm to about 1 ⁇ .
  • the hydrogen storage material comprises one or more further elements, for example one or more elements selected from the group consisting B, Al, Ga, In, As, Sb, Te and transition metals.
  • the hydrogen storage material contains > 28 wt%, > 29 wt%, > 30 wt%, > 35 wt%, > 40 wt%, > 45 wt%, > 50 wt%, > 55 wt%, > 60 wt%, > 65 wt%, > 70 wt%, > 75 wt%, > 80 wt%, > 85 wt%, > 90 wt%, > 95 wt%, > 96 wt%, > 97 wt%, > 98 wt% or > 99 wt% of one or more elements selected from the group consisting of group IV elements, for example Si and/or C, based on the total weight of the hydrogen storage material.
  • group IV elements for example Si and/or C
  • the negative electrode comprises ⁇ 30% by weight of the one or more group IV elements; for example ⁇ 35%, ⁇ 40%, > 45%, > 50%, > 55%, > 60%, > 65%, > 70%, > 75% > 80%, > 85% or > 90% by weight of the one or more group IV elements, for example Si and/or C, based on the total weight of the negative electrode.
  • E14 A cell according to any of the preceding embodiments where the negative electrode comprises a solid electrolyte interface capable of allowing transport of protons.
  • E15 An cell according to any of the preceding embodiments where the hydrogen storage material includes one or more further elements selected from the group consisting of structural modifiers (elements to promote the amorphous phase of a material), hydrogen bond strength modifiers and solid electrolyte interface (SEI) modifiers; for example one or more further elements selected from the group consisting of B, alkaline earth metals, transition metals, rare earth metals, other metals of groups III or V of the periodic table, O, F, P, CI and the like,
  • E16 A ceil according to any of the preceding embodiments where the electrolyte composition is neutral or acidic, for example having a pH of about 7 or lower; for example from about 1 , from about 2, from about 3, from about 4, from about 5 or from about 6 to about 7.
  • E17 A cell according to any of the preceding embodiments where the electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, protic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotsc oxonium compounds, aprotic phosphonsum compounds and alkali or alkali earth metal salts.
  • the electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, protic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotsc oxonium compounds, aprotic phosphonsum compounds and alkali or alkali earth metal salts.
  • the electrolyte composition comprises an ionic compound containing a cation selected from the group consisting of NH 4 + (ammonium), methylammonium, ethylammonium, dsmethylammonium, diethylammonium, trimethylammonium (N e 3 H + ), triethylammonium, tributylammonium, diethylmethylammonium, hydroxyethylammonium, methoxymethylammonium, dibutyiammonium, methylbutylammonium, anilinium, pyridinium, 2-methyipyridinium, imidazoiium, 1-methyiimidazoiium, 1 ,2- dimethylimidazolium, imidazolinium, 1-ethylimidazolium, 1-(4-sulfobutyl)-3-methylimidazolium, 1-aliyiimidazoiium,
  • tributyimethylphosphonium triethylmethylphosphonium, trihexyitetradecylphosphonium, triphenylpropylphosphonium or tetrakis(hydroxymethyi)phosphonium; for instance, the cation is 1 ⁇ ethyl-3-methylimidazQlium, l-hexyl-3-methylimidazolium, 1-butyl-1- methylpyrrolidinium or trihexyl(fetradecyi)phosphonium,
  • electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of carboxylates, imides, methides, nitrate, bifluoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aluminates.
  • E20 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of
  • y is an integer of 1 to 6
  • n is an integer of 1 to 8, for instance 1 to 4,
  • z is an integer of 1 to 4,
  • X is B or Al
  • R w , Rx, R y and R z are independently halogen, CrC 2 oaikyi, CrC 20 alkyi which is partly or fully fluorinated, C r C 20 alkoxy, CrC 20 aikoxy which is partly or fully fluorinated, Ci-C 2 oaikyl-COG or CrC 20 alkyi-COO which is partly or fully fluorinated and
  • 0 "" 0 is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxyiic acid or from a 1 ,2- or 1 ,3 ⁇ hydroxycarboxylic acid and
  • any one CF 2 group may be replaced by O, S(0) 2 , NR or CH 2 .
  • E21. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of F 2 P(C 2 F5)4-, F3P(C 2 Fs)3-, F 4 P(C 2 Fs) 2 - I F 2 P(C3F 7 )4-, FsPiCsFyJs " ,
  • BOB bisoxalatoborate
  • the electrolyte composition comprises an ionic compound containing a carboxylate anion of formula RCOO where R is hydrogen or hydrocarbyi; such as formate, acetate (ethanoate), acrylate, propanoate, n- butanoate, i-butanoate, n-pentanoate, i-pentanoate, octanoate, decanoate, benzoate, salicylate, thiosalicylate, 2-, 3- or 4-nitrobenzoate; citrate, oxalate, tartrate, giycolate, gluconate, rna!aie, mandeiate, a carboxyiate of nitrilotriacetic acid, a carboxylate of N-(2-hydroxyethyi)- ethylenediaminefriacetic acid, a carboxylate of ethylenediaminetetraacetic acid, a carboxy
  • an imide anion such as dicyanamide, N(S02F)2 ⁇ ((bisfluorosulfonyl)imide), a
  • bis(perfluoroalkylsulfonyl)imide such as [N(S02CF 3 )2] '" (bistriflimide),
  • a methide such as a tris(perfluoroalkyisuifonyl)methide, for example
  • a borate such as orthoborafe, tetra hydroxy borate, tetraborate, tetraphenylborate, [B(3,5- (CF 3 ) 2 CeH 3 )4]- (BARF), B(C 2 04) 2 - (bis(oxaiafo)borate) (BOB), difiuoro(oxalato)borate (dFOB), di(trifluoroacetato)oxalatoborate (D(Ac)OB), B(C 6 F 5 )4 " or BF 4 "' (ietrafluoroborate); or
  • a phosphate such as dihydrogen phosphate, hydrogen phosphate, alkyl phosphate, dialkyl phosphate, phosphate, PF 6 " (hexafiuorophosphate), HP0 3 F " (fluorohydrogen phosphate), trisoxalaiophosphaie (TOP), ietrafluorooxalatophosphate (TFOP) or a fluoro(perfluoroalkyl)phosphate such as F 2 P(C 2 F 5 )4 '"' , F 3 P(C 2 F 5 ) 3 ""
  • F4P(C 3 F 7 )2 " F 2 P(C4Fg)4 ⁇ F 3 P(C 4 F 9 ) 3 - or F 4 P(C4F 9 ) 2 -; or
  • a sulfonate such as an alkylsulfonate, arylsulfonate or perfluoroalkylsulfonate, for instance trifluoromethanesulfonate (triflate), p-toiuenesuifonate (tosylate) or methanesulfonate
  • a sulfate such as hydrogensulfate, sulfate, thiosulfate or an alkylsulfate such as methyisulfate or ethylsulfate; or
  • a carbonate anion such as carbonate, hydrogencarbonate or an alkylcarbonate such as methylcarbonate, ethylcarbonate or butylcarbonate; or
  • an aluminate such as AI(OC(CF 3 ) 3 ) 4 ⁇ di(trifluoroacetato)oxalatoaluminate (d(Ac)OAI), tetrachloroaluminate, tetrafluoroaluminate, tetraiodoaluminate or tetrabromoaluminate.
  • E25 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of diethylmethyiammonium trifluoromethanesulfonate (DE A TfO), ethy!ammonium nitrate, triethylammonium
  • DE A TfO diethylmethyiammonium trifluoromethanesulfonate
  • ethy!ammonium nitrate triethylammonium
  • methanesulfonate 2-methylpyridinium trifluoromethanesulfonate, ammonium fluoride, methyiammonium nitrate, hydroxyethyia rnonium nitrate, ethylammonium nitrate,
  • dimethylammonium nitrate 1-methyiimidazoiium nitrate, 1-ethylimidazolium nitrate, t- butylammonium tetrafluoroborate, hydroxyethyiammonium tetrafiuoroborate,
  • methoxyethylammonium mesylate dimethylammonium mesylate, dibutylammonium mesylate, triethylammonium mesylate, dimethylethyiammonium mesylate, hydronium hydrogensulfate, ammonium hydrogensulfate, methyiammonium hydrogensulfate, ethylammonium
  • methoxyethylammonium dihydrogen phosphate dimethylammonium dihydrogen phosphate, dibutylammonium dihydrogen phosphate, methyibutylammonium dihydrogen phosphate, ammonium bifluoride, methylammonium bifluoride, ethylammonium bifluoride and
  • E28 A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of 1-ethyl-3-methylimidazolium trifiuoromethanesuifonate (E IM TfO), 1-ethyi-3-methylimidazolium tetrafluoroborate (EMIM BF 4 ), 1-ethyl-3-methylimidazolium bis(trifluoromethyisulfonyi)imide (EMIM TFSI), 1 -ethyl-3- methyiimidazolium acetate (EMIM Ac), 1-butyi-3-methylimidazolium trifiuoromethanesuifonate (BMIM TfO), 1-butyl-3-methylimidazolium acetate (BMIM Ac), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), tri-n-butylmethyl
  • electrolyte composition comprises a protic acid; for example a protic acid such as
  • hydrochloric acid nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid or periodic acid; or
  • a bisulfate such as sodium bisulfate, potassium bisulfate or ammonium bisuifate; or
  • HAsFs HBF 4 , H(OEt 2 )BF 4 , HPF 6 , ,H[N(S0 2 CF 3 ) 2 ] or H[N(S0 2 CF 2 CF 3 ) 2 ].
  • E28 A cell according to any of the preceding embodiments where the electrolyte composition comprises an organic protic acid such as a carboxylic acid of formula RCOOH where R is hydrogen or hydrocarbyi, for example formic acid, acetic acid, acrylic acid, fiuoroacetic acid, difluoroacetic acid, trifluoroacetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methylbutanoic acid, valeric acid, hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- or 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, giycolic acid, gluconic acid, malic acid, mandelic acid, nitriiotriacetic acid, N-(2-hydroxyethyl)-ethylenediaminetriacetic acid, ethylenedi
  • E29 A cell according to any of the preceding embodiments where the electrolyte composition comprises a protic sulfonic acid of formula RSO3H where R is alky! or aryl or alkyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsuifonic acid, methanesulfonic acid or trifluoromethanesulfonic acid.
  • RSO3H protic sulfonic acid of formula RSO3H where R is alky! or aryl or alkyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsuifonic acid, methanesulfonic acid or trifluoromethanesulfonic acid.
  • E30 A cell according to any of the preceding embodiments where the electrolyte composition comprises a proiic acid which is an oxonium ion associated with a highly non-coordinating ion such as Brookhart's acid (BARF acid), [HiOEkMBp.S-iCFakCeHaM, [H(OEt2)2][B(C s F5)4] (oxonium acid) or [H(OEt 2 )2][Ai(OC(CF 3 )3)4].
  • BARF acid Brookhart's acid
  • H(OEt2)2][B(C s F5)4] oxonium acid
  • H(OEt 2 )2][Ai(OC(CF 3 )3)4 a highly non-coordinating ion
  • E31 A cell according to any of the preceding embodiments where the electrolyte composition comprises at least two different ionic compounds; for example, where the electrolyte
  • composition comprises
  • a salt and an ionic liquid for example a protic or aprotic ammonium salt or an alkali metal salt such as an aikai metal halide;
  • a protic acid, protic ammonium compound or a protic oxonium compound and an ionic liquid for example a carboxyiic acid and an ionic liquid.
  • E32 A ceil according to any of the preceding embodiments where the electrolyte composition comprises two different ionic compounds which contain an identical cation or an identical anion.
  • E33 A ceil according to any of the preceding embodiments where electrolyte composition comprises two different ionic compounds with a weighfcweight ratio of from about 99.9:0.1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
  • E34 A ceil according to any of the preceding embodiments where the electrolyte composition contains no organic solvent and ⁇ 1000 ppm, ⁇ 100 ppm or ⁇ 10 ppm water by weight, based on the total weight of the electrolyte composition; or where the electrolyte composition contains ⁇ 9, ⁇ 8, ⁇ 7, ⁇ 6, ⁇ 5 or ⁇ 4 ppm water by weight, based on the total weight of the electrolyte composition.
  • E35 A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent,
  • E36 A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of water.
  • E37 A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of organic solvent.
  • electrolyte composition comprises a solvent comprising water and an organic solvent.
  • a ceil according to embodiment 38 where the weight:weight ratio of water to organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99,5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
  • organic solvent comprises one or more solvents selected from the group consisting of organic carbonates, ethers, giymes, ortho esters, polyalklene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents and nitrile solvents.
  • an organic carbonate for example a cyclic or acyclic organic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), trimethylene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyimethyi carbonate (EMC), vinylene carbonate, difluoroethylene carbonate or monofluoroethylene carbonate; or
  • a cyclic or acyclic organic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), trimethylene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyimethyi carbonate (EMC), vinylene carbonate, difluoroethylene carbonate or monofluoroethylene carbonate; or
  • an ether or giyme such as dimethoxymethane (DMM), diethoxymethane, 1 ,2-dimethoxyefhane (DME or ethylenegiycol dimethyiether or glyme), diglyme, trigiyme, tetragiyme, ethylenegiycol diethylether (DEE), ethylenegiycol dsbutylether, dsethyleneglycol diethylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1 ,3-dioxane, 1 ,3-dioxolane (DIOX), 4-methyl-1 ,3- dioxolane (4-MeDIOX), 2-rnethy!-1 ,3-dioxo!ane (2-MeDIOX), 1 ,4-dioxane, dimethyiether, ethylmethylether,
  • an ortho ester such as trimethoxymethane, triethoxymethane, 1 ,4-dimethyl-3,5,8- trioxabicyclo[2.2.2]octane or 4-ethyl-1-methyl-3,5,8-trioxabicyclo[2.2.2]octane; or
  • a polyalkyiene glycol that is a homo- or cooligomer or homo- or copolymer of CrC 4 aikyiene glycols, such as polyethylene glycol (PEG) or monomethyl, dimethyl or diethyl (end-capped) polyethylene glycol with weight average molecular weights (Mw) for example from about 200 to about 1200 g/mol, from about 200 to about 1000 g/mol, from about 200 to about 900 g/mol, from about 200 to about 700 g/mol or from about 200 to about 500 g/mol, for example oligomers of 4 monomers or more, for instance tetraethyiene glycol, fluorinated tetraethylene glycol or tetrapropyiene glycol, for instance PEG 200, PEG 300, PEG 400, PEG 500, PEG 600, PEG 700, PEG 800, PEG 900 or PEG 1000; or
  • an ester or lactone such as ⁇ -butyrolactone (GBL), ⁇ -valerolactone, ⁇ -valerolactone, ethyl acetate (EA), 2-methoxyethyl acetate, 2-ethoxyetbyl acetate, 2-butoxyetbyl acetate, 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EGDA), 3-ethoxy ethyl propionate (EEP), methyl butyrate (MB), n-amyl acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate or dimethyl malonate; or
  • GBL ⁇ -butyrolactone
  • EA ethyl acetate
  • 2-methoxyethyl acetate 2-ethoxyetbyl
  • a dibasic ester mixture such as methyl esters of adipic, giutaric or succinic acids; or
  • a glycol such as ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2- propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol (ethylene glycol butyl ether, EB), 2- phenoxyethanoi, 2-benzyloxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol (diethylene glycol butyl ether, DB), propylene glycol butyl ether (PB), propylene glycol methyl ether (PM), Methylene glycol (TEG), dipropylene glycol methyl ether (DPM), diethylene glycol methyl ether, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, perfluoro-1 ,4-butanediol, perfluoro-1 ,5-butanediol, flu
  • a formate such as methyl formate, ethyl formate, isobutyl formate or tert-butyl formate; or a sulfone or sulfoxide such as methylsulfonylmethane (SM or dimethylsuifone),
  • an amide such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methyipyrroiidone (NMP), 2-pyrrolidone, 1 ,3-dimethyl-2-imidazolidinone (DMI), hexameihy!phosphoramide (H PA) or N.N'-dimethyl-N.N'-trimethyleneurea (1 ,3-dimethyl-3,4,5,6 etrahydro-2(1 H)- pyrimidinone (DMPU)); or
  • an alcohol such as benzylalcohoi (BA), ethanol, trifluoroethanol (2,2,2-trifluoroethanol), methanol, isopropanol, t-butanol or n-butanol; or
  • a ketone such as methylethylketone (MEK) or methyi-isoamylketone ( IAK); or
  • a nitro solvent such as nitrobenzene, nitromethane or nitroethane; or
  • a nitrile solvent such as acetonitriie, propionitrile, butyronitrile or adiponitrile.
  • E42 A ceil according to any of embodiments 1-33 and 35-41 where the electrolyte composition comprises a solvent and where the weightweight ratio of ionic compounds in total to solvent is ffrroomm aabboouutt 9999..99::00,, 11 ttoo aabboouutt 00,, 11 ::9999..99,, ffrroomm aabboouutt 9999..55::00,,55 ttoo aabboouutt 00,,55::9999..55,, ffrroomm aabboouutt 9999::11 ttoo aabboouutt 11 ::9999,, ffrroomm aabboouutt 9955::55 ttoo aabboouutt 55::9955,, ffrroomm aabboouutt 9900::1100 ttoo aabboouutt 1100
  • IV is a group IV element-based hydrogen storage material
  • Si is a silicon-based hydrogen storage material
  • a cell according to any of the preceding embodiments comprising a positive electrode, the positive electrode comprising one or more cathode active materials selected from the group consisting of transition metals, transition metal oxides, transition metal hydroxides, transition metal oxide/hydroxides and transition metal fluorides; for example one or more materials selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, ir, Pt or Au;
  • a present anode is employed in a SWAGELOK ceil assembly. A smaller anode is employed and therefore limits the capacity.
  • An anode is prepared via chemical vapor deposition of amorphous silicon on a nickel subsirate.
  • the anode is 0.94 cm 2 with an amorphous silicon film thickness of about 250 nm and a film mass of 51.7 ⁇ g. Thickness is measured with a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • the cathode is sintered nickel hydroxide on a nickel mesh substrate.
  • composition is 2 molar acetic acid in 1-ethyl-3-methylimidazolium acetate.
  • the cell is cycled at a charge/discharge current density of 387 mA/g.
  • the cell exhibits stable charge/discharge characteristics after 25 cycles as demonstrated in Fig. 1.
  • the anode exhibits a charge plateau at ca. 1.4 V and a discharge plateau at ca. 1.2 V and a specific capacity of ca, 889 mAh/g at the 20 ,h cycle.
  • a 100 g anode alloy containing 1 weight percent (wt%) hydrogen (1 g or 1 mol) will have a capacity of 96500 A « sec (Faraday's constant) or 26.8 A « hour or 268 mAh/g of alloy.
  • Example 1 is repeated, with the ceil charged at a rate of 408 mA/g for 10 hours and discharged at 510, 1020, 2041 and 4082 mA/g to provide discharge capacities of 2604, 1681 , 1080 and 647 mAh/g respectively.
  • Example 3 Hydrogenated amorphous silicon (a-Si:H) thin films are deposited on nickel foil substrates in an AMAT P500Q plasma enhanced chemical vapor deposition (PECVD) system.
  • PECVD plasma enhanced chemical vapor deposition
  • n-type doped a-Si:H thin films are obtained in-situ by the addition of phosphine in the working gas.
  • the gas flow for PECVD is 60 seem siiane, 460 seem helium and 40 seem 5% phosphine in helium.
  • the substrate temperature is 100°C
  • radio frequency (rf) power is SOW
  • working pressure is 3 Torr during deposition.
  • the deposition time is 125 s and the average thickness of the as-deposited a-Si:H thin films is 247 nm.
  • amorphous silicon samples are also prepared by an rf-sputtering technique, a kind of physical vapor deposition (PVD).
  • PVD physical vapor deposition
  • Non-hydrogenated a-Si films are deposited on nickel substrates by rf-sputtering, followed by a subsequent ex-situ hydrogenation treatment.
  • the sputter deposition source is an 800 diameter planar silicon target constructed of segments of monocrystalline silicon wafers (0.001 ⁇ cm, boron-doped) bonded to the sputtering cathode backing plate.
  • Typical sputter deposition parameters include a gas flow of 3 seem argon, 8 mTorr glow discharge pressure, an rf (13.56 MHz) power of 486 W (1.5 W cm -2 ) and a target- substrate distance of 74 mm, with substrates held close to room temperature. Substrates are located in fixed positions underneath the target, and maximum deposition rates of approximately 125 A min _i are obtained in the racetrack region under these conditions. Post-deposition ex-situ hydrogenation treatments are conducted in a steel reactor vessel used in the pressure- concentration-temperature measurement. Variables of peak pressure (1 MPa and 6 MPa), peak temperature (30Q°C and 500°C), and anneal time (2 h and 20 min) are employed.
  • the non-aqueous electrolyte is 2M glacial acetic acid (CH3COOH, >99.7%, Alfa Aesar) in [EMIM] [Ac] (>95%, loLiTec GmbH) (1-ethyl-3-methyiimidazolium acetate).
  • [E IM] [Ac] is baked at 1 15°C in a vacuum oven for 48 h to remove residual water.
  • the water content of the ionic liquid is determined to be ⁇ 1000 ppm using a coulometric Karl Fischer titrator.
  • glacial acetic acid is mixed with [EMIM] [Ac] with a volume ratio of 1.14: 10.
  • the ionic conductivity at 6 mS cm -1 is measured by a conductivity meter (YSI model 3200).
  • a conductivity meter YSI model 3200.
  • the thickness of a-Si:H films varies between 247 nm and 3.0 mm and the active material mass varies between 70 mg and 840 mg.
  • the electrochemical performance of the a-Si:H thin films are tested using a half-ceil configuration with P/N ratio (positive capacity/negative capacity) > 100.
  • the positive electrode is a piece of sintered Ni(OH) 2 that is fabricated in-house and used as standard positive electrodes for our Ni/MH battery research. Both electrodes are baked at 115°C in a vacuum oven for 12 h before cell assembly.
  • a 1.25 cm (dia.) Swageiok-fype ceil is assembled in an Ar-fvetted glove box using an a-Si:H thin film anode and a sintered Ni(OH)2 cathode, separated by a standard nonwoven separator and clamped with two 1.25 cm (dia.) nickel rod current collectors. Then 1 mL of electrolyte is injected into the cell before the ceil is sealed for testing.
  • the electrochemical charge/discharge tests are performed using an Arbin BT-2143 battery test station at constant currents and a discharge cut-off voltage at 0.6 V.
  • the current densities are varied between 510 and 4082 mA g _ .
  • Cyclic voltammetry (CV) measurements are performed using Gamry's interface 1000 potentiostat galvanostat in a three- electrode Swagelok cell.
  • the working electrode is an a-Si:H thin film on Ni foil and the counter electrode is a sintered Ni(OH) 2 disc.
  • a leak-free reference electrode (Warner Instruments) is inserted through the top port of the Swagelok ceil as reference, which has a standard potential of 0.24 V vs. standard hydrogen electrode in a 3.4 M KCI solution.
  • Surface morphology and film thickness is measured using JEOL ⁇ JSIV16320F SE .
  • the Raman shift is measured using an E- Z Raman spectroscopy system with a 532 nm excitation source. The instrument is calibrated with a signal from a silicon standard at 520 cm "1 .
  • Fourier transform infrared (FTIR) spectra are measured using Perkin Elmer Spotlight 400 FTIR Imaging System.
  • the a-Si:H anode prepared via CVD is charged to 1935 mAh g _1 at a rate of 2041 mA g- 1 ( ⁇ 1C rate) and discharged at the same rate ( ⁇ 1 C) until a cutoff voltage at 0.6 V vs. the Ni(OH)? counter electrode.
  • the initial discharge capacity is 888 mAh g "1 and gradually increases to 1418 mAh g- 1 at the 38th cycle, which is more than four times higher than conventional the AB 5 alloy used in Ni/MH batteries. Converting to the number of hydrogen per Si atom, it corresponds to SiHi.48.
  • the capacity increase during initial cycling may be attributed to the activation of the a ⁇ Si:H anode.
  • the a-Si:H anode exhibits a long cycle life - 707 mAh g _1 at the end of 500 cycles and a discharge voltage plateau at around 0.9 V.
  • the increased charge and discharge overpotentials upon cycling may result from the increased internal resistance due to the growth of solid electrolyte interface (SE!) between the electrolyte and electrodes, electrolyte degradation and/or the increased contact resistance arising from the lose contact of a-Si:H thin film from the nickel substrate.
  • SE solid electrolyte interface
  • the rate capability of the a-Si:H anode is tested.
  • the anode is charged to 4082 mAh g -1 at a rate of 2041 mA g _1 and discharged at four different rates: 510, 1020, 2041 and 4082 mA g _1 .
  • the discharge capacity decreases dramatically with the increase of current density, and the obtained discharge capacities are 2604, 1681 , 1080 and 647 mAh g _1 , corresponding to SiH 2 7 2 , SiHi .76 , SiHi .i 3 and SiHo es, respectively.
  • the discharge capacity and coulombic efficiency at a constant discharge rate of 510 mA g- 1 as a function of charge capacity are measured.
  • the highest discharge capacity obtained is 3635 mAh g _1 when the a-Si:H anode is charged to 5752 mAh g 1 , which is equivalent to about 3,8 hydrogen atoms stored in each silicon atom. This capacity is comparable with the highest capacity reported for a-Si thin film anode in LIB.
  • the coulombic efficiency is 87% when the anode is charged to 1000 mAh g _1 , which declines to 63% for a charge capacity of 5752 mAh g _1 .
  • Such a coulombic efficiency is relatively low compared to LIB and the mechanism of capacity loss needs further investigation.
  • the anodic peak is observed at near -0.2 V vs. reference electrode, which results from the oxidation and desorption of absorbed hydrogen atom at the anode-electrolyte interface. With the increase of scan rate, the anodic peak current increases and the peak potential slightly shifts in the positive direction. Unlike typical metal hydride electrode in alkaline solutions, a full cathodic peak is observed at near -0.9 V vs. reference electrode, which benefits from the enlargement in electrochemical window of non-aqueous IL based electrolyte.
  • Raman spectroscopy are conducted. Raman spectroscopy is sensitive to Si-Si bond structure while FTIR spectroscopy is effective to reveal the Si-H bond configuration.
  • Raman spectra of an a- Si:H thin film before and after 500 cycles is performed.
  • a typical Raman spectrum of a-Si:H thin film comprises of four Gaussian peaks, corresponding to transverse optic (TO), longitudinal optic (LO), longitudinal acoustic (LA) and transverse acoustic (TA) modes. The transition of amorphous to micro-crystaliine/crystaliine Si is differentiated from the peak wavenumber shift.
  • a broad peak at 460-490 crrr 1 results from the TO vibrational mode of amorphous silicon and a sharp peak at 512-520 crrr 1 represents the TO mode of crystal grains of different sizes.
  • a third peak near 500 cm -1 is from the bond dilation at the grain boundaries. Only one broad peak present is in the range of 460-520 cm -1 before and after 500 cycles. The broad peak centers at 480 cm -1 , which means that the film is purely amorphous. No noticeable Raman shift is observed before and after cycling, indicating that the a-Si:H thin films remain amorphous during cycling.
  • FTIR spectra of a-Si:H thin films before and after 500 cycles is performed. The FTIR spectrometer has a limited range starting from 650 cm "1 , which is at the edge of the major absorption band centered near 630 crrr 1 due to the wagging vibrational mode of Si
  • Si-H mono-hydride
  • Si-H 2 bending vibrational and stretching modes of Si dihydride
  • Si-H 2 poly-hydride complexes
  • the absorption band near 2000cm "1 resulting from the stretching mode of Si-H is not observed.
  • the most intensive Si-H peak near 630 cm "1 is often used to estimate the hydrogen content in a- Si:H thin films.
  • Non- hydrogenated a-Si films exhibit very low discharge specific capacities of less than 200 mAb g _ , and the capacity increases significantly after hydrogenation treatment, which may be attributed to enhanced hydrogen diffusion after hydrogenation.
  • a thicker sample NT (nickel tab) -92, ⁇ 3.G microns, hydrogenated with 6 MPa hydrogen pressure at 30Q°C for 2 h shows a discharge capacity in excess of 2224 mAh g _1 after 3 cycles. However, capacity faded quickly afterwards.
  • a thinner sample NT-93, -1.2 microns, hydrogenated at 500°C and 1 MPa for 2 h exhibits a discharge capacity of 2377 mAh g 1 after 13 cycles and no sign of capacity fading after 14 cycles
  • a 1 mm-thick Si thin film anode in LIB exhibits a capacity of 3000 mAh g _1 for 12 cycles followed by a quick decline.
  • a-Si:H thin films are prepared and used as anodes in a proton conducting Ni/MH battery with non-aqueous ionic liquid based electrolyte, which exhibit high specific capacities and excellent cycle stabilities.
  • CVD grown thin films a specific discharge capacity of 1418 mAh g _i is obtained at a discharge rate of 2041 mA g _1 for the 38th cycle and the capacity retained 707 mAh g- after 500 cycles; and a maximum capacity of 3635 mAh g 1 is obtained at a lower discharge rate.
  • a 1.2 micron thick rf-spuftered a-Si:H thin film anode hydrogenaied at 500°C demonstrates a capacity of 2377 mAh g ⁇ ⁇ while another 3.0 micron thick a-Si:H thin film exhibits a capacity of 2224 mAh g _1 at the 3rd cycle.

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Abstract

Hydrogen storage negative electrodes based on group IV elements, for example hydrogen storage negative electrodes based on silicon and/or carbon, are highly effective towards reversibly charging/discharging hydrogen in an hydride electrochemical cell.

Description

Electrochemical Hydrogen Storage Electrodes and Cells The invention relates to electrochemical hydrogen storage electrodes, electrochemicai hydrogen storage materials and electrochemical cells.
Government Support Statement
This invention was made with government support under DE-AR0000386 awarded by
Advanced Research Projects Agency-Energy. The government has certain rights in the invention.
Background of the Invention
Rechargeable metal hydride (MH) electrochemical cells are employed in numerous applications such as portable computers, phones, industrial applications, aerospace applications and electric vehicles.
The negative electrode (anode) of a metal hydride electrochemical ceil may comprise an AB5, AB2, A2B7-type, Ti-Ni-based, Mg-Ni-based, BCC or Zr-Ni-based metal hydride alloy. The metal alloys are hydrogen storage alloys. Conventional AB5 and A2B7 alloys have capacities of from about 320 to about 360 mAh/g and are of relatively high weight. Desired are rechargeable electrochemical ceils having lighter weight, higher capacity and higher gravimetric energy density.
it has been found that a negative electrode comprising a hydrogen storage material based on one or more group IV elements is highly effective as a hydrogen charge/discharge component in an electrochemical cell. The hydrogen storage material is for example based on silicon and/or carbon.
Summary of the Invention
Some non-limiting aspects of the invention include the following,
a, A stable group IV element-based, e.g. stable silicon-based hydrogen storage negative eiectrode for electrochemical uses. The hydrogen storage electrode may for instance be in contact with a non-aqueous electrolyte composition and/or comprises a solid electrolyte interface (SEI) capable of allowing proton transport. The SEI provides corrosion resistance for the electrode and may also serve as an electrochemical catalyst. The durability and functionality of the SEI layer are very important for the operation of a rechargeable
electrochemical ceil (battery). The typical SEI on the anode made from conventional hydrogen storage alloy contains oxide, hydroxide, metallic inclusion, amorphous oxide/metal buffer, voids and channels. b. An electrochemical cell comprising a stable group IV element-based, e.g. stable silicon-based hydrogen storage negative electrode and an aqueous or non-aqueous electrolyte composition in contact with the electrode, for example the electrolyte composition is neutral or acidic, where the electrolyte composition has a pH of about 7 or less.
c. An electrochemical cell comprising a hydrogen storage negative electrode, a positive electrode and an electrolyte composition in contact with the electrodes, where the reversible half cell charge/discharge electrochemical reaction at the negative electrode is
■■■■■■■HI for example
bl + H + 6 ItfMMMMMtf 5/H
where /V and Si are a stable group IV element-based and a stable silicon-based hydrogen storage material, respectively.
d. A hydrogen storage negative electrode for electrochemical uses, where the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 charge/discharge cycles. e. An electrochemical cell comprising a hydrogen storage negative electrode, a positive electrode and an electrolyte composition in contact with the electrodes, where the cell exhibits a gravimetric energy density of > 100 Wh/kg and/or a volumetric energy density of > 250 Wh/L. f. Modifying elements and/or compounds may be employed to alter the physical (density, porosity, melting temperature, etc.), chemical (alloy heat of formation, hydride heat of formation, electron coherent energy, hydrogen bond strength, nature of hydrogen bond, etc) and electrochemical properties (capacity, rate capability, charge-retention, cycle stability, corrosion resistance, etc.) of the anode, in the case of group IV element-based hydrogen storage anode materials, suitable modifying elements include 1. Structural modifiers: elements to promote the amorphous phase of the material, such as B; 2. H-bond strength modifiers: elements to adjust the voltage of the ceil, such as alkaline earth metals, transition metals, rare earth metals, and other metals from groups 111 and V of the periodic table; and 3. SE! modifiers: elements to prolong the cycle stability and reduce the temperature sensitivity of the SEI layer, including non- metal elements such as O, F, P, CI, etc.
Detailed Disclosure
Disclosed are negative hydrogen storage electrodes based on one or more group IV elements, for instance based on Si and/or carbon. The hydrogen storage electrodes are useful in electrochemical cells. The cells comprise an electrolyte composition that is for example nonaqueous or is aqueous with a pH of about 7 or less. In present electrochemical cells, it is believed that the reversible half cell electrochemical reaction at the negative electrode is
Figure imgf000005_0001
where IV is a hydrogen storage material based on one or more group IV elements,
in the case of a silicon-based hydrogen storage negative electrode, it is believed that the reversible half cell electrochemical reaction at the negative electrode is
Figure imgf000005_0002
where Si is a silicon-based hydrogen storage material.
in a charged state, the negative electrode is reduced and contains stored hydrogen while the positive electrode is oxidized. During discharge, protons exit the negative electrode (anode) and migrate through the electrolyte composition to the positive electrode (cathode) while their associated electrons exit the anode via external circuitry.
The present cells are rechargeable and during charge/discharge cycles the negative electrode reversibly charges and discharges hydrogen as does a nickel metal hydride anode in a metal hydride ceil, although possibly not via an identical mechanism, A present
electrochemical ceil may be considered a "hydride battery" or a "non-metal hydride battery" or a "rechargeable proton battery".
The hydrogen storage negative electrode comprises a hydrogen storage material based on one or more group IV elements, for example based on silicon. The hydrogen storage material is capable of reversibly charging and discharging hydrogen during cycling of an electrochemical cell. For example, the mechanism of charging hydrogen may be intercalation of protons.
Likewise, the term "hydrogen storage" means capable of reversibly charging and discharging hydrogen during cycling of an electrochemical cell.
The term "based on" or "-based" means that the hydrogen storage material comprises greater than 27 wt% of one or more group IV elements, based on the total weight of the hydrogen storage material. "Silicon-based" means that the hydrogen storage material contains > 27 wt% of Si, based on the total weight of the hydrogen storage material.
Group IV elements include silicon, carbon, germanium and tin. Group IV is also known as the carbon group or group 14 of the periodic table.
For example, the hydrogen storage material contains > 28 wt%, > 29 wt%, > 30 wt%, > 33 wt%, > 35 wt%, > 40 wt%, > 45 wt%, > 50 wt%, > 55 wt%, > 60 wt%, > 65 wt%, > 70 wt%, > 75 wt%, > 80 wt%, > 85 wt%, > 90 wt%, > 95 wt%, > 96 wt%, > 97 wt%, > 98 wt% or > 99 wt% of one or more elements selected from the group consisting of group IV elements, for example Si and/or carbon, based on the hydrogen storage material. The term "stable" means that the anode exhibits < 10% capacity degradation over 100 charge/discharge cycles of an electrochemical cell. For instance, the anode may exhibit < 9%, < 8%, < 7%, < 6%, < 5% or < 4% capacity degradation over 100 charge/discharge cycles.
Percent capacity degradation at certain charge/discharge rates over 100 cycles is defined as [(capH - capL)/capH] · 100 where capH is the highest value of discharge capacity and capL is the lowest value of discharge capacity. A typical half-cell cycling schema is with a C/5 charge rate for 1 10% state-of-charge (5.5 h) and discharge at C/5 rate to a cut-off voltage of 0.9 V vs. a standard Ni(OH)2/NiOOH or -0.5 V vs. a Hg/HgO refrence electrode.
The anode may consist of or consist essentially of the hydrogen storage material or, alternatively, the anode may comprise the hydrogen storage material and a substrate. For instance, the hydrogen storage material may be adsorbed on a substrate such as a metal, glass, plastic or inorganic substrate. Inorganic substrate includes graphite.
For example, the hydrogen storage material may comprise silicon. Silicon may
advantageously be amorphous (a-Si). Amorphous silicon may be deposited as a thin film onto a substrate via chemical vapor deposition (CVD) techniques, for example via plasma enhanced chemical vapor deposition techniques (PECVD).
Silicon may be hydrogenated to prepare hydrogenated silicon prior to or after preparation of the anode. For example, amorphous silicon may be hydrogenated to prepare a-Si: H prior to or after preparation of the anode. Thus, the anode may be hydrogenated prior to preparation of an electrochemical device. For instance, hydrogenated amorphous Si (a-Si:H) thin films may be prepared by chemical vapor deposition. An a-Si:H thin film may be prepared via rf-sputtering deposition of a-Si followed by hydrogenation.
The hydrogen storage material may comprise doped silicon or doped hydrogenated silicon, for example P-type silicon or hydrogenated P-fype silicon. P-type silicon is for example silicon doped with Al. Suitable also for instance is silicon or hydrogenated silicon doped with phosphine or boron. For example, the hydrogen storage material is doped hydrogenated amorphous silicon (doped a-Si:H).
Suitable a-Si film thickness is for instance > 20 nm, > 50 nm, > 90 nm, > 120 nm or > 180 nm. For instance, a suitable a-Si film thickness is from about 90 nm to about 10 μπτι, from about 100 nm to about 5 μηι, from about 150 nm to about 3 μηη, from about 150 nm to about 2 pm or from about 150 nm to about 1 μηη.
Silicon may be microcrystalline silicon or nanocrystalline silicon, which generally are forms of amorphous silicon containing small silicon crystals. Silicon may also be mono-crystalline silicon, poiycrystalline or protocrystailine. Silicon may be porous silicon (p-Si). Types of porous silicon include microporous, mesoporous and macroporous, with average pore sizes of less than aboui 2 nm, from about 2 nm to about 50 nm and greater than about 50 nm, respectively.
The hydrogen storage material may contain one or more different forms of silicon.
The hydrogen storage materials include alloys of silicon, for example alloys of silicon with one or more of carbon, germanium and tin. For instance amorphous alloys of silicon and carbon (amorphous silicon carbide) or alloys of silicon and germanium or alloys of silicon and tin. Amorphous alloys of silicon and carbon can also be hydrogenated to prepare a-Sii-xCx:H where x is for example from about 0.01 to about 0.99, from about 0.05 to about 0.95 or from about 0.1 to about 0.9.
Other hydrogen storage materials of the invention may also be hydrogenated prior to preparation of an electrochemical device.
Hydrogenation (hydrogenating) is performed for instance under hydrogen gas at a pressure greater than atmospheric. Hydrogen pressure is for instance from about 2 atm to about 20 aim. Hydrogenation may be performed at increased temperature, for instance from about 25°C to about 500°C. Hydrogenation may be performed e!ectrochemically.
Hydrogen storage materials inciude carbon and graphitic materials such as natural graphite, artificial graphite, expanded graphite, graphene, carbon fiber, soft carbon, hard carbon, non-graphitizable carbon, carbon black, carbon nanotube, fulierene, activated carbon, crystalline carbon and amorphous carbon.
The hydrogen storage materials may include one or more further elements, for instance one or more further elements selected from the group consisting of structural modifiers
(elements to promote the amorphous phase of a material), hydrogen bond strength modifiers and solid electrolyte interface (SE!) modifiers.
Structural modifiers include for example B.
Hyrogen bond modifiers inciude for example alkaline earth metals, transition metals, rare earth metals and other metals of groups 111 and V of the periodic table.
SEi modifiers inciude non-metals such as O, F, P, Ci and the like.
In addition to the hydrogen storage materials, the anode may further inciude binders and/or conductive materials and/or other additives. The anode assemblies may include these mixtures in adherence to a current collector such as a metal foil substrate.
The binder assists in coupling the hydrogen storage material and the conductive material and the mixture to the current collector. Binders include poiy(tetrafluoroethylene) (PTFE), a copolymer of acrylonitrile and butadiene (NBR), polyvinylidene fluoride (PvDF), polyvinyl alcohol, carboxy methyl cellulose (CMC), starch, hydroxy propyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene- propylene-diene polymer (EPDM), sulfonated-EPD , styrene-butadiene rubber (SBR), fluorine rubber, copolymers thereof and mixtures thereof. Binders may be employed from about 1 to about 50 weight %, based on the total weight of electrode assembly.
Conductive materials may be from about 1 to about 20 weight %, based on the total weight of the electrode assembly. Conductive materials include graphitic materials such as natural graphite, artificial graphite, a carbon black such as acetylene black, Ketjen black, channel black, furnace black or lamp black, conductive fibers such as carbon fiber or metal fiber, metal powders such as carbon fluoride, aluminum or nickel powder, conductive metal oxides such as zinc oxide, potassium titanate or titan oxide and other conductive materials such as
poiyphenyiene derivatives.
A filler may be employed as a component for controlling expansion of the anode. Fillers include oiefin-based polymers such as polyethylene or polypropylene and fibrous material such as glass fiber or carbon fiber.
The negative electrode may advantageously comprise > 30% by weight of the one or more group IV elements; for example > 35%, > 40%, > 45%, > 50%, > 55%, > 60%, > 65%, > 70%, > 75% > 80%, > 85% or > 90% by weight of the one or more group IV elements, based on the total weight of the negative electrode (total weight of the electrode assembly). The total weight of the negative electrode includes the hydrogen storage material and optional components such as substrate, binders, conductive materials and additives.
A separator is typically interposed between the cathode and the anode which is for instance an insulating thin film ensuring high ion (proton) transmission. The separator generally has a pore size of about 0.01 to about 10 microns and a thickness of about 5 to about 300 microns. Separator materials include sheets or non-woven fabrics comprising materials including glass fiber, cotton, nylon, polyester, polyethylene, polypropylene, polyvinyl chloride,
poiyfetrafluoroethylene and kraff paper.
The active materials of the positive electrode (cathode active materials) participate in the charge/discharge reactions. Suitable active materials include nickel hydroxide active materials, i.e. nickel hydroxide or modified nickel hydroxide.
The cathode materials may comprise a multi-phase disordered nickel hydroxide material having at least one modifier. The at least one modifier is for instance a metal, a metallic oxide, a metallic oxide alloy, a metal hydride and/or a metal hydride alloy. For example, the modifier is one or more components selected from the group consisting of Al, Ba, Ca, F, K, Li, Mg, Na, Sr, Bi, Co, Cr, Cu, Fe, in, LaH3, Mn, Ru, Sb, Sn, TiH2, TiO, and Zn. Such materials are taught in U.S. Pat. No. 5,348,822. Suitable cathode materials may comprise a disordered multi-phase nickel hydroxide matrix including at least one modifier, for example 3 modifiers, chosen from F, Li, Na, K, Mg, Ba, Ln, Se, Nd, Pr, Y, Co, Zn, Ai, Cr, Mn, Fe, Cu, Zn, Sc, Sn, Sb, Te, Bi, Ru and Pb. Suitable cathode materials are taught for example in U.S. Pat. No. 5,637,423.
Cathode materials may comprise nickel hydroxide modified with one or more group Π elements and Co in a solid solution state. Such materials are taught in U.S. Pat. No. 5,366,831.
The cathode active materials may comprise nickel hydroxide and one or more components selected from the group consisting of cobalt, cobalt hydroxide and cobalt oxide and a carbon powder. The cathode materials may further comprise a compound of Ca, Sr, Ba, Cu, Ag or Y, for example Ca(OH)2, CaO, CaF2, CaS, CaS04, CaSi205, CaC204, CaW04, SrC03l Sr(OH)2, BaO, Cu20, Ag2Q, Y2(C03)3 or Y2G3. Suitable cathode materials are taught for instance in U.S. Pat. No. 5,451 ,475.
Cathode active materials may comprise a metal oxide and one or more of Co, Ca, Ag, Mn, Zn, V, Sb, Cd, Y, Sr, Ba and oxides of Ca, Sr, Ba, Sb, Y or Zn. The metal oxide is for example nickel oxide and or manganese oxide. Such active materials are taught in U.S. Pat. No.
5,455,125.
The cathode materials may contain nickel hydroxide and a further component selected from the group consisting of Y, In, Sb, Ba and Be and Co and/or Ca. Such materials are disclosed in U.S. Pat. No. 5,466,543.
Cathode materials may be prepared by reacting nickel sulfate and ammonium hydroxide to form a nickel ammonium complex; the complex is then reacted with sodium hydroxide to form nickel hydroxide. The method may provide nickel hydroxide comprising one or more of Co, Zn and Cd. These materials are taught in U.S. Pat, No. 5,498,403.
Cathode active materials may comprise nickel hydroxide and cobalt oxyhydroxide as taught in U.S. Pat. No. 5,489,314.
Cathode materials may comprise nickel hydroxide, cobalt monoxide and elemental zinc as taught in U.S. Pat. No. 5,506,070.
The cathode materials may comprise nickel hydroxide, nickel powder, a second powder and at least one of cobalt, cobalt hydroxide and cobalt oxide. The second powder contains one or more of Ca, Sr, Ba, Cu, Ag and Y. Such materials are taught in U.S. Pat. No. 5,571 ,636.
The cathode active materials may comprise particles of nickel hydroxide or manganese hydroxide having at least partially embedded therein a conductive material. The conductive material may be for instance nickel, nickel alloys, copper, copper alloys; metal oxides, nitrides, carbides, siiicides or borides; or carbon (graphite). These materials are disclosed in U.S. Pat. No. 6,177,213. The cathode materials may comprise nickel hydroxide particles containing at least three modifiers selected from the group consisting of Ai, Bi, Ca, Co, Cr, Cu, Fe, In, La, rare earths, g, Mn, Ru, Sb, Sn, Ti, Ba, Si, Sr and Zn. For example, nickel hydroxide particles may contain at least four modifiers, for instance, Ca, Co, Mg and Zn. Such materials are disclosed in U.S. Pat. No. 6,228,535.
The active cathode material for instance comprises nickel hydroxide and a carbon material such as graphite. The cathode may also comprise a polymeric binder. The polymeric binder is for example a thermoplastic organic polymer, for instance selected from the group consisting of polyvinyl alcohol (PVA), polyethylene oxide, polypropylene oxide, polybutyiene oxide, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose,
hydroxypropylmethyi cellulose, polyethylene, polypropylene, polyisobutyiene, polyvinyl chloride, polyvinyliden chloride, polyvinyliden fluoride, polytetrafluoroethyiene (PTFE), fluorinated ethylene propylene (FEP), perfluroalkoxy (PFA), polyvinylacetate, polyvinyl isobutylether, polyacrylonitrile, polymethacrylonitrile, polymethylmethacrylate, po!ymethylacry!ate,
poiyethy!methacry!ate, ally! acetate, polystyrene, polybutadiene, polyisoprene,
poiyoxymethylene, polyoxyethyiene, polycydsc thioether, polydimethylsiloxane, polyesters such as polyethylene terephthalate, polycarbonate and poiyamide. Blends and copolymers of the above are also suitable. The polymeric binder may also be an elastomer or rubber such as styrene-butadiene copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethyiene-styrene- butadiene block copolymer, styrene-ethylene-butadiene-styrene block copolymer or styrene- acrylonitrile-butadiene-methyl acrylate copolymer. Suitable active materials are taught for instance in U.S. Pat. No. 6,617,072,
The cathode active material may contain nickel hydroxide and nickel oxyhydroxide as taught in U.S. Pat. No. 7,396,379.
Generally, cathode active material particles are formed in a sintered or pasted electrode. The pasted electrode may be made by mixing the material with various additives and/or binders and applying the paste to a conductive support. Preferably, one or more cobalt additives are added to the pasted electrode. The cobalt additives may include Co and/or CoO to enhance conductivity, improve utilization and reduce electrical resistance of the positive electrode.
Modified nickel hydroxide may contain one or more modifiers such as Co, Cd, Ag, V, Sb, Ca, Mg, AI, Bi, Cr, Cu, Fe, In, rare earths, Mn, Ru, Sn, Ti, Ba, Si, Sr or Zn, A suitable modified nickel hydroxide is (Ni,Co,Zn)(OH)2, for instance in the form of a spherical powder. In modified nickel hydroxides, nickel generally is present at a level of > 80 atomic percent, for instance > 90 atomic percent, based on the metals. According to the present invention, further cathode active materials are possible. Further cathode active materials include transition metals and their oxides, hydroxides,
oxide/hydroxides and fluorides. For example, further cathode active materials include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt and Au and their oxides, hydroxides, oxide/hydroxides and fluorides.
For example, further cathode active materials are selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au;
oxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au;
hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au;
oxide/hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au and
fluorides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au.
in further cathode active materials selected from the group consisting of metal oxides, metal hydroxides and metal oxide/hydroxides, nickel may be present at a level of < 5, < 10, < 15, < 20, < 25, < 30, < 35, < 40, < 45, < 50, < 55, < 60, < 65, < 70, < 75, < 80 or < 85 atomic percent, for instance < 90 atomic percent, based on the total metals of the metal oxides, metal hydroxides and metal oxide/hydroxides.
The electrolyte composition may be neutral or acidic, having a pH of about 7 or less.
Suitable electrolyte compositions are for example taught in copending U.S. patent applications 14/540,445, filed November 13, 2014 and 14/669,588, filed March 26, 2015. The electrolyte composition allows for transport of protons.
For instance, the electrolyte compositions have a pH of from about 1 , from about 2, from about 3, from about 4, from about 5 or from about 6 to about 7.
Suitable electrolyte compositions contain one or more ionic compounds. The ionic compounds may be protic compounds selected from the group consisting of Bransted acids (protic acids) and protic ammonium compounds or oxonium compounds. Bransted acids for instance have a pKa of less than or equal to about 5.
The ionic compounds may be aprotic compounds selected from the group consisting of ammonium compounds, oxonium compounds, phosphonium compounds and alkali or alkali earth metal compounds.
The ionic compounds contain a cation and an anion. Alkali metal or alkali earth metal cations include Li+, Na+, K+, Rb+, Cs+, Be++, Mg++, Ca++, Sr*+ and Ba++.
Ammonium ions are cations of formula ""NR1 R2R3R4 where Ri , R2, R3 and R are selected from hydrogen and hydrocarby! or two of R1-R4 together are hydrocarbylene or three of R1-R4 together are hydrocarbylene. When one or more of R1-R4 is hydrogen, the ammonium ion is protic. When all four of R1-R4 are hydrocarbyl or hydrocarbylene the ammonium ion is aprotic. Ammonium ions also include hydrazinium cations of formula Ri R2N-+NR3R4R5, where Ri , R2, R3, R4 and R5 are selected from hydrogen and hydrocarbyl or Ri and R2 together and/or two of R3-R5 together are hydrocarbylene.
Ammonium ions a!so include hydroxylammonium cations of formula HO- +Ri R2R3 where Ri , R2 and R3 are selected from hydrogen and hydrocarby! or two of R1-R3 together are
hydrocarbylene.
Oxonium ions are positively charged groups of formula OR1 R2R3 where Ri , R2 and R3 are selected from hydrogen and hydrocarby! or two of R1-R3 together are hydrocarbylene. When one or more of R1-R3 is hydrogen, the oxonium is protic. When ail three of R1-R3 are hydrocarbyl or hydrocarbylene, the oxonium is aprotic.
Phosphonium ions are positively charged groups of formula +PRi R2R3R4 where Ri , R2, R3 and R4 are hydrocarby! or two of R1-R4 together are hydrocarbylene.
Hydrocarbyl is any hydrocarbon based group, bound to the cationic nitrogen, oxygen or phosphorus with a carbon atom. Hydrocarbylene is a ring-forming version of hydrocarbyl.
Hydrocarbyl is for instance alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl or aralkyl, which may be substituted by one or more groups selected from the group consisting of halogen, hydroxy, CrC4alkoxy, thio, Ci-C4a!ky!thio, amino, Ci-C4alkylamino, di-CrC4a!ky!amino, nitro, cyano, - COOH and -COO". Hydrocarby! may also be interrupted by one or more groups selected from the group consisting of -G-, -S-, -NH- and -N(Ci-C4alkyl)-. Hydrocarbyl may be both substituted by one or more of said groups and interrupted by one or more of said groups. For instance alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl or aralkyl may be substituted by one to three groups selected from the group consisting of chloro, hydroxy, methoxy, ethoxy, propoxy, butoxy, thio, methylthio, methylamino, ethylamino, propylamino, butylamino, dimethylamino, diethylamino, dipropylamino, dibutylamino, -COOH, -COO", cyano and nitro and/or may be interrupted by one to three groups selected from the group consisting of -O-, -S-, -NH- and -N(Ci-C4alkyl)-.
Hydrocarbyl also includes polyethylene glycols and polypropylene glycols such as
R'(OC2H4 or R'(OC3H6)i where R' is hydrogen or alky! and n is an integer from 1 to 50, for instance from 1 to 40, 1 to 30 or 1 to 20, for instance from 1 to 10, When two or three of R1-R5 together are hydrocarbylene, this means together with the N, O or P atom they form a heterocyclic ring. The ring is for example 5- or 8-membered. The heterocyclic ring may contain a further heteroatom and may be saturated or unsaturated.
Hydrocarbylene is for instance -(CH2)4-, -(CH2)5-, -{CH3)N-CH=C{CH3)-CH™ =CH-CH=CH- CH=CH-, =C(CH3)-C=CH-CH=CH-, =C-C(CH3)=CH-CH=CH-, =C-CH=C(CH3)-CH=CH-, -CH=CH-CH=CH-, -CH2=CH~CH2-CH2-, -CH=CH-N=CH~, -CH2CH2NHCH2CH2-, ~CH2~CH2- N=CH-, -CH2-CH2-0-CH2-CH2- or =CH-(CH2)3-. The further heteroatom is for example N, O or S.
Examples of ammonium ion rings are piperidinium, pyrrolinium, 2,4-dimethyipyrazoiium, pyrrolininium, pyrrolidinium, pyridinium, morpholinium and methylpyridinium. Pyridinium is an example of where three of R1-R4 together form a ring. The hydrocarbylene ring may also be annulated to form for instance quinolinium or isoquinolinium.
Aikyl is for instance from 1 to 25 carbon atoms, is branched or unbranched and includes methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-ethylbutyl, n-pentyl, isopentyi, 1-methyipentyi, 1 ,3-dimethylbutyl, n-hexyl, 1-methylhexyl, n-heptyi, isoheptyl, 1 ,1 ,3,3- tetramethyibutyl, 1-methylheptyl, 3-methylheptyl, n-octyi, 2-ethyihexyi, 1 ,1 ,3-trimethylhexyl, 1 , 1 ,3,3-tetramethyipentyi, nonyl, decyi, undecyl, 1-methylundecyi, dodecyl, 1 , 1 ,3,3,5,5- hexamethyihexyi, tridecyl, tetradecyi, pentadecyl, hexadecyi, heptadecyl, octadecyl, icosyi and docosyl.
Partly or fully fiuorinated means replacement of one, more than one or all of the hydrogens of the alkyl with fiuoro. Perfluoroalkyl means all hydrogens of an alkyl are replaced with fluoro (fully fiuorinated).
Alkenyl is an unsaturated version of alkyl, for instance allyl.
Cycloalkyi includes cyclopentyl, methylcyclopentyl, dimethylcyclopentyl, cyciohexyi, methylcyclohexyl, dimethyicydohexyl, trimethylcyclohexyl, tert-butylcyclohexyl, cycioheptyl or cyciooctyl.
Cycloalkenyl is an unsaturated version of cycloalkyi.
Aryi includes phenyl, 0-, m- or p-methylphenyi, 2,3-dimethyiphenyi, 2,4-dimethylphenyl, 2,5- dimethylphenyl, 2,6-dimethylphenyl, 3,4-dimethylphenyl, 3,5-dimethylphenyl, 2-methyi-6- ethylphenyl, 4-tert-butyi phenyl, 2-ethylphenyl or 2,6-diethyiphenyi.
Aralkyl includes benzyl, a-methylbenzyl, α,α-dimethylbenzyl and 2-phenylethyl.
Examples of ammonium ions include protic ions such as NH4 + (ammonium),
methylammonium, ethylammonium, dimethylammonium, diethyiammonium, trimethylammonium (NMe3H+), triethylammonium, tributylammonium, diethylmethylammonium,
hydroxyethylammonium, methoxymethyiammonium, dibutyiammonium, methylbutylammonium, anilinium, pyridinium, 2-methylpyridinium, imidazolium, 1-methylimidazolium, 1 ,2- dimethylimidazolium, irnidazolinium, 1-ethylimidazoiium, 1-(4-sulfobutyl)-3-methylimidazolium, 1-allylimidazolium. quinolinium, isoquinolinium, pyrrolinium, pyrrolininium and pyrrolidinium.
Examples of ammonium ions also include aproiic ions such as 1-butyl-1- methylpyrrolidinium, ieiramethylammonium, tetraethylammonium, tetra-n-butylammonium, n- butyl-tri-ethylammonium, benzyl-tri-meihyiammonium, tri-n-butylmethylammonium, benzyl~tri- ethylammonium, 1-meihylpyridinium, 1-buiyl-3,5-dimeihylpyridinium, 1 ,2,4-trimethylpyrazolium, trimethylhydroxyethylammonium (choline), tri-(hydroxyethyi)methylammonium, dimethyl- di(polyoxyeihyiene)ammonium, 1 ,2,3-trimethylimidazolium, 1-butyl-3-methylimidazolium, 1- ethyl-2,3-dimethylimidazolium, 1-allyl-3-methylimidazolium, 1-hydroxyethyl-3- methylimidazolium, 1 ,3-dimethylimidazolium, 1-ethyl-1-methylpiperidinium, 4-ethyl~4~ meihylmorpholinium, 1-(cyanomethyl)-3-methylimidazolium, 1-(3-cyanopropyl)pyridinium, 1 ,3- bis(cyanomeihyi)imidazolium, 1-hexyl-3-methylimidazolium and 1-ethyl-3-meihylimidazolium.
Pyrrolinium is the ammonium of pyrrole, pyrrolininium is the ammonium of pyrroline and pyrrolidinium is the ammonium of pyrrolidine. Pyrroline may be 1-, 2- or 3-pyrroline, thus the ammonium cation of 1-, 2- or 3-pyrroline is included.
An example of a hydrazinium ion is hydrazinium (H2NNH3 +).
An example of a hydroxyiammonium ion is hydroxyiammonium (HO-NH3 +).
Examples of protic oxonium ions include H30+ (hydronium), ΗΌ(Εί)2, Η2ΕίΟ+, H2MeO+, HO(Me)2, proionated THF and protonated 2-methyl~THF.
Examples of aprotic oxonium ions include O(Me)3, Ό(Εί)3 and methylated or ethyiated THF or 2-methyl-THF.
Me is methyl, Et is ethyl, nBu is n-butyi, tBu (or t-butyl) is tert-butyl and THF is
tetrahydrofuran. Without designation, butyl means n-butyi.
Examples of phosphonium ions include methyitriphenylphosphonium,
teirapheny!phosphonium, fetrabutyiphosphonium, tributylmethylphosphonium,
triethylmethylphosphonium, irihexyltetradecylphosphonium, triphenylpropylphosphonium and tetrakis(hydroxymethyl)phosphonium.
Examples of suitable anions are hydroxide, nitrate, perchlorate, bifiuoride, aikoxides, haiides, phosphates, phosphinates, phosphonates, borates, carboxylates, sulfites, sulfates, sulfonates, carbonates, imides, aluminates, cyanates, methides, arsenates, silicates and antimonates.
Anions, cations and ionic compounds may be those disclosed for instance in U.S. Pat. No. 6,254,797 and U.S. Pub. No. 201 1/0045359. Bifiuoride is HF2 ~ Aikoxides are RO where R is hydrocarbyl, for example methoxide, ethoxide, n-propoxide, i-propoxide, n-butoxide, t-butoxide or phenoxide. Alkoxides also include where R is perfluoroalkyi. Haiide is chloride, bromide, iodide or fluoride. Phosphates include dihydrogen phosphate, hydrogen phosphate, alkyi phosphate, dialkyl phosphate, phosphate, PFs" (hexafluorophosphate), HPO3F" (fluorohydrogen phosphate), trisoxalatophosphate (TOP), tetrafluorooxalatophosphate (TFOP) and
fluoro(perfluoroalkyl)phosphates such as F2P(C2F5)4~ F3P(C2F5)3"
(tris(pentafluoroethyl)trifluorophosphate or FAP), F P(C2FS)2 ~ F2P C3F F3P(C3F7)3~
F4P(C3F7j2 ~ F2P(C Fg 4~ F3P(C4F9)3~ and F4P C4Fg)2 ~. Phosphinates are for instance hydrogen aikyl phosphinate, dialkyl phosphinate, hydrogen aryi phosphinate or diaryl phosphinate. For instance bis(2,4,4-frimethyiphenyi)phosphinafe. Phosphonates are for instance
alkylphosphonate such as methylphosphonate or hydrogenphosphonate (phosphonate).
Borates include orthoborate, tetrahydroxyborate, tetraborate, tetraphenyl borate, [B(3,5~ (CF3)2CSH3) ]~ (BARF), B(C204)2 ~ (bis(oxaiato)borate) (BOB), difluoro(oxalato)borate (dFOB), di(frifluoroacetato)oxalatoborafe (D(Ac)OB), B(CsF5)4~ and BF4 ~ (tetrafiuoroborate). Carboxyiate anions are of formula RCOO- where R is hydrogen or hydrocarby! and include formate, acetate (ethanoate), propanoate, n-butanoate, i-butanoate, n-pentanoate, i~pentanoate, octanoafe, decanoate, benzoate, salicylate, thiosaiicylate, 2-, 3- or 4-nitrobenzoate; citrate, oxalate, tartrate, glycoiate, gluconate, malate, mandelate, a carboxyiate of nitrilotriacetic acid, a carboxyiate of N-(2-hydroxyethyl)-ethylenediaminetriacetic acid, a carboxyiate of
ethylenediaminetetraacetic acid, a carboxyiate of diethylenetriaminepentaacetic acid and haioaikylcarboxyiates such as fluoroacetate, difiuoroacetafe, trifiuoroacetafe, chioroacetate, dichioroacetate and trichloroacetate. Sulfites include sulfite and hydrogensuifite. Sulfates include hydrogensulfate, sulfate, thiosulfate and alkyisulfates such as methyisu!fate and ethylsuifate. Sulfonates include aikyl, arylsulfonates and perfluoroaikylsuifonates, for instance trifiuoromethanesuifonate (triflate), p~toiuenesuifonate (tosylate) or methanesulfonate
(mesylate). Carbonate anions are for instance carbonate, hydrogencarbonate or an aikylcarbonate such as methylcarbonate, ethylcarbonate or butyicarbonafe. imide anions include dicyanamide, N(S02F)2 " ((bisfiuorosulfonyi)imide), bis(perfiuoroalkylsulfonyl)imides such as [N(S02CF3)2]~ (bistriflimide), bis(pentafluoroethyisulfonyi)imide and
N(CF3S02)(CF3(CF2)3S02)" and (perfluoroaikylsuifonyl)(perfluoroalkylcarboxyl)imides.
A!uminates include AI(OC(CF3 3 4~ di(trifluoroacetato)oxalatoaluminate (d(Ac)OAI),
tetrachloroaluminate, tetrafluoroaluminate, tetraiodoaluminate and tetrabromoaluminate.
Cyanates include thiocyanate and cyanate, ethides include
tris(perfluoroalkylsulfonyl)methides such as tris(trifiuoromethylsulfonyl)methide, C(CF3S02)3 ". Arsenates include arsenate, hydrogen arsenate, dihydrogen arsenate and AsFs ~ Silicates include SiFs~2. Antimonates include SbFe" and Sb(OH)s~. For example, the protic ionic compound is H3P04, NH4SO3CF3, NH4BF4, NH4OH, NH4CI, NH4Br, NH4I, NH4F, NH4H2PO4, (ΝΗ4)2ΗΡ0 , methylammonium phosphonate, pyridinium tosylate, pyridinium chloride, anilinium chloride, hydroxylammonium chloride, (NH4)2S04, hydrazinium sulfate (N2H6S04), (NH4)HS04, NaHSQ4, NH4BF4, H2SO4, KH2PO4, K2HPO4, NaH2P04, Na2HP04, HBF4, H(OEt2)BF4, HPFS, HAsFg, HCI04, HSO3CF3, H[N(S02CF3)2] or
Figure imgf000016_0001
The protic ionic compound may also be an oxonium ion of a highly non-coordinating ion such as Brookhart's acid (BARF acid), [H(GEt2)2][B[3,5- CF3)2C6H3]4j. Other examples include [H(OEt2)2][B(CsF5)4] (oxonium acid) and [H(OEt2)2][AI(OC(CF3)3)4]. In these cases the cation is protonated diethyl ether (diethyl ether oxonium). Alternatively, the cation may be other protonated ethers, for instance protonated tetrahydrofuran (THF).
The protic ionic compound may be a protic ionic liquid such as ethylammonium nitrate, diethylmethylammonium trifluoromethanesulfonate (DEMA TfO), triethylammonium
methanesulfonate, 2-methylpyridinium trifluoromethanesulfonate, ammonium fluoride, methylammonium nitrate, hydroxyethyiammonium nitrate, ethylammonium nitrate,
dimethylammonium nitrate, 1-methylimidazoiium nitrate, 1-ethylimidazolium nitrate, t- buty!ammonium tetrafiuoroborate, hydroxyethyiammonium tetrafiuoroborafe,
methylbutyiammonium tetrafiuoroborate, triethylammonium tetrafiuoroborate, imidazolium tetrafiuoroborate, 1-methylimidazolium tetrafiuoroborate, 1 ,2-dimethylimidazolium
tetrafiuoroborate, t-butylammonium triflate, 2-fluoropyridinium inflate, hydroxyethyiammonium trifiate, 1 ,2-dimethylimidazolium triflate, imidazolium triflate, 1-methylimidazolium
hydrogensulfate, 1-methy!imidazo!ium chloride, 1-methylimidazolium triflate, hydronium triflate, methylammonium mesylate, ethylammonium mesylate, butylammonium mesylate,
methoxyethylammonium mesylate, dimethylammonium mesylate, dibutylammonium mesylate, triethylammonium mesylate, dimethylethylammonium mesylate, hydronium hydrogensulfate, ammonium hydrogensulfate, methylammonium hydrogensulfate, ethylammonium
hydrogensulfate, propylammonium hydrogensulfate, n-buty!ammonium hydrogensulfate, t- butylammonium hydrogensulfate, dimethylammonium hydrogensulfate, diethyiammonium hydrogensulfate, di-n-buiylammonium hydrogensulfate, methylbutyiammonium hydrogensulfate, ethylbutylammonium hydrogensulfate, trimethylammonium hydrogensulfate, triethylammonium hydrogensulfate, tributylammonium hydrogensulfate, dimethylethylammonium hydrogensulfate, dibutylammonium fluorohydrogen phosphate, triethylammonium fluorohydrogen phosphate, tributylammonium fluorohydrogen phosphate, hydronium dihydrogen phosphate,
methylammonium dihydrogen phosphate, ethylammonium dihydrogen phosphate,
propylammonium dihydrogen phosphate, n-butylammonum dihydrogen phosphate, methoxyethylammonium dihydrogen phosphate, dimethylammonium dihydrogen phosphate, dibutylammonium dihydrogen phosphate, methylbutylamrnonium dihydrogen phosphate, ammonium bifiuoride, methylammonium bifluoride, ethylammonium bifiuoride or
dimethylammonium bifiuoride.
Carboxyiic acids are protic acids/protic compounds. Carboxylic acids are of formula RCOOH where R is hydrogen or hydrocarbyi. Carboxylic acids contain carboxylate anions. Carboxylic acids include formic acid, acetic acid, acrylic acid, fluoroacetic acid, difiuoroacetic acid, trifluoroacetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methyibutanoic acid, valeric acid, hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- o 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, glycolic acid, gluconic acid, malic acid, mandelic acid, nitrilotriacetic acid, N- (2-hydroxyethyl)-ethylenediaminetriacetic acid, ethylenediaminetetraacetic acid and
diethyleneaminepentaacetic acid.
For example, the aprotic ionic compound is N e4 +S03CF3 ', NMe4OH, Et^BF*-, NMe,+CI-, NEt4+Br, NnBu4 +l", NnBu4 +F", NEt4 +f-12PCv, ( Μβ4)2ΗΡθ4, methyltriphenyl phosphonium iodide, tetrakis(hydroxymethyl)phosphonium chloride, tetraphenylphosphonium bromide, 1- methylpyridinium chloride, benzalkonium chloride, e3OBF4, Et3OBF4, NEt4PFs, N e4AsF6, NMe4CI04, NEt4S03CF3, NMe4[N(S02CF3)2] or NEt4[N(S02CF2CF3)2].
The aprotic ionic compound may also include a highly non-coordinating anion such as BARF, for instance sodium BARF, Na+B[3,5~(CF3)2C6H3]4]". Other examples include
K+B(C6F5)4- and K+Al(OC(CF3)3)4-.
The aprotic ionic compound may be an aprotic ionic liquid such as tri-n- butylmethylammonium methylsuifate, 1-ethyl-2,3-dimethylimidazolium ethylsulfate, 1-butyl-3- methylimidazoiium thiocyanate, 1-bufyl-3-methyiimidazolium tetrachloroaluminate, 1-butyl-3- methylimidazolium methylsuifate, 1-butyl-3-methylimidazolium methanesulfonate, 1 -butyl-3- methyiimidazolium hydrogencarbonate, 1-butyl-3-methylimidazolium hydrogensulfate, 1-butyl-3- methylimidazolium chloride, 1 ,2,3-trimethylimidazolium methylsuifate, tris- (hydroxyethyl)methyiammonium methylsuifate, 1 ,2,4-trimethylpyrazolium methylsuifate, 1 ,3- dimethylimdiazolium hydrogencarbonate, 1-ethyl-3-methylimidazoiium hydrogencarbonate, 1- ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium tetrachloroaluminate, 1 -ethyl-3- methyiimidazolium thiocyanate, 1-ethyl-3-methylimidazolium methanesulfonate, 1 -ethyl-3- methylimidazolium hydrogensulfate, 1-ethyl-3-methylimidazolium ethylsulfate, 1 -ethyl-3- methylimidazoiium nitraie, 1-butylpyridinium chloride, 1-ethyl-3-methylimidazolium dicyanamsde, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium
hexafluorophosphate, 1-butyl-3,5-dimethylpyridinium bromide, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, l-ethyl-S-methylirnidazolium bis(pentafluoroethylsulfonyl)imide, 1~eihyl-2,3-dirnethylimidazolium methyicarbonate, carboxymethyl-tributylphosphonium bis(trifluoromethylsulfonyl)imide, N-carboxyethyl-methylpyrrolidinium
bis(trifluoromethyisulfonyi)irriide, N-carboxymethyl-trimethylammonium
bis(trifiuoromethyisulfonyi)imide, N-carboxymethyl-methylpyridinium
bis(tnTiuoromethyisulfonyi)irnide, hexyltrimethylammonium bis(trifluromethylsulfonyl)imide, tetrabutylphosphonium methanesulfonaie, triethylmethylammonium methyicarbonate, 1-ethyl-1- meihylpiperidinium methyicarbonate, 4-ethyl-4-methylmorpholinium methyicarbonate, 1-butyl-1- methylpyrrolidinium methyicarbonate, triethylmethylammonium dibutylphosphate,
tributylmethylphosphonium dibutylphosphate, triethylmethylphosphonium dibutylphosphate, tetrabutylphosphonium tetrafiuoroborate, tetrabutylphosphonium p-toluenesulfonate, tributylmethylphosphonium methyicarbonate, 1-ethyl-3-methylimidazolium hydrogencarbonate, tnbutylmethylammonium methyicarbonate, tnbutylmethylammonium dibutylphosphate, 1 -ethyl-3- methylimidazolium dibutylphosphate, 1-butyl-3-methylimidazolium dibutylphosphate, 1- (cyanomethyl)-3-methylimidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-methylimidazoiium bis(trifluoromethylsulfonyl)imide, 1 -(3-cyanopropyl)-3- methylimidazolium dicyanamide, 1-(3-cyanopropyl)pyridinium chloride, 1-(3- cyanopropyi)pyridinium bis(trifiuoromethylsuifonyl)imide, 1 ,3-bis(cyanomethyi)imidazoiium chloride, 1 ,3-bis(cyanomethyl)imidazolium bis(trifluoromethylsulfonyl)imide, 1 ,3- bis(cyanopropyi)imidazoiium chloride, 1 ,3-bis(3~cyanopropyl)imidazoiium
bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1 -butyl-3- methylimidazolium tetrafiuoroborate, 1-ethyl-3-methylimidazolium tetrafiuoroborate, 1-ethyl-3- methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, l-hexyl-3-methyiimidazoiium chloride, tributylmethylphosphonium methyisulfate, triethylmethylphosphonium dibutylphosphate, trihexyltetradecylphosphonium
bis(trifiuromethyisuifonyl)imide, trihexyltetradecylphosphonium bis(2,4,4- trimethylphenyl)phosphinate, trihexyltetradecylphosphonium bromide,
trihexyltetradecylphosphonium chloride, trihexyltetradecylphosphonium decanoate,
trihexyltetradecylphosphonium dicyanamide, 3-(triphenylphosphonio)propane-1-suifonate or 3- (triphenylphosphonio)propane-l-sulfonic acid tosyiate.
Examples of carboxyiate compounds are tetramethylammonium benzoate,
tetraethylammonium oxalate, tetrabutylammonium tartrate, sodium tartrate, potassium formate, tetramethylammonium acetate, 1-methylpyridinium chloride, trimethylammonium citrate tri-basic, tetramethylammonium 2-, 3- or 4-nifrobenzoate, ammonium benzoate, ammonium salicylate, ammonium oxalate, ammonium tartrate, methyltriphenyl phosphonium acetate, tetrakis(hydroxymethyl)phosphonium benzoaie, tetrakis(hydroxymethyl)phosphonium formate, mono- or di-potassium tartrate, ammonium citrate mono-, di~ or tri-basic; ammonium 2- nitrobenzoate, ammonium 3-nitrobenzoate, ammonium 4-nitrobenzoate, potassium
trifluoroacetate and potassium chloroacetate.
In polybasic carboxylic acids, ammonium and/or alkali metal and/or alkali earth metal ions may replace one or any number of the acidic hydrogens to form a present carboxylate compound. For instance included are the mono-, di- and tri-basic ammonium citrates and mono-, di- and tri-basic sodium citrates.
ionic liquids are ionic compounds that exhibit a melting point of < 100°C.
Otherwise, the ionic compound is "a salt" with a melting point > 100°C.
ionic liquids generally are ammonium or phosphonium compounds, that is containing ammonium or phosphonium cations.
Salts include halide salts such as alkali or alkali earth metal halide salts such as NaCi, KCi or KBr as well as other ionic compounds with melting points above 100°C, Alkali and alkali earth metal salts include for instance anions selected from the group consisting of nitrate, perchlorate, bifluoride, halides, phosphates, phosphinates, phosphonates, borates,
carboxylates, sulfites, sulfates, sulfonates, carbonates, imides, aiuminates, cyanates, metbides, arsenates, silicates and antimonates.
The present ionic compounds may contain the cation and anion together in the same molecule. Thus, also included are zwitterionic compounds (inner salts) such as betaines.
included are zwitterions containing ammonium or phosphonium ions and sulfonate or sulfate ions. Included are hydroxysultaines, 4-(triphenylphosphonio)butane-1-sulfonate, methyl N- (triethylammoniosulfonyl)carbamate (Burgess reagent) and phosphonium sulfate zwitterions as taught for instance in U.S. Pat. No. 3,471 ,544. Included is sulfamic acid.
Advantageously, two or more different ionic compounds are employed in the electrolyte composition. For instance, the two different ionic compounds may be a protic ionic compound and an aprotic ionic compound or may be an ionic liquid and a salt.
For instance, present electrolyte compositions may comprise at least two different ionic liquids. The electrolyte composition may comprise one or more ionic liquids and one or more salts, for example a protic or aprotic ammonium salt or an alkali metal salt such as an alkai metal halide.
The electrolyte composition may contain a mixture of a carboxylate compound and a carboxylic acid. The electrolyte composition may contain a mixture of a carboxyiate-containing ionic liquid and a carboxylic acid. The electrolyte composition may contain two different carboxylic acids. The electrolyte composition may contain a protic acid, protic ammonium compound or a protic oxonium compound and an ionic liquid.
Where at least two different ionic compounds are present, the weight:weight ratio of the two different ionic compounds is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
In the two different ionic compounds, the cations or the anions may be identical.
The electrolyte compositions advantageously contain an ionic liquid. Cations of ionic liquids include ammonium and phosphonium ions discussed above. Ionic liquids may contain a cation selected from the group consisting of formulae (a)-(h)
+N(R)4 (a) +P(R)4 (b)
Figure imgf000020_0001
Figure imgf000020_0002
where each R is independently H, CrCi6aikyl or hydroxyCi-Ci6alkyl, for instance methyl, ethyl, hydroxyethyl or propyl and
X is CH2, O, S or NR where R is H or Ci-Cisalkyl, for instance H, methyl, ethyl or propyl.
For instance, suitable cations of ionic liquids include 1-ethyl-3-methylimidazoliurrs, 1-hexyl-3- methyiimidazoiium, 1-butyl-l-methyipyrroiidinium and trihexyl(tetradecyl)phosphonium.
Anions of ionic liquids include carboxylates, imides, methides, nitrate, bifiuoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aiuminates.
The ionic liquids may contain an anion selected from the group consisting of
[FzB(CiriF2rn+l)4-z]',
Figure imgf000021_0001
[0-C(0)-Cr!iF2m+l]' ,
[0-S(0)2-Cn,F2n1+i]-1 [N(C(0)-Cn,F2n,+i)2]-, [N(S(0)2-CmF2n»i)2]-, [N(C(0)-CmF2m+,)(S(0)rCmF2m+i)]-, [N(C(0)-Cn,F2m,i)(C(0)F)]-, [N(S(0)2-CmF2m+i)(S(0)2F)]-, [N(S{0)2F)2]-, [C(C(0)-CmF2m+i)3]-, [C(S(0)2-CmF2m,1)3]-I
Figure imgf000021_0002
1 where
y is an integer of 1 to 6,
m is an integer of 1 to 8, for instance 1 to 4,
z is an integer of 1 to 4,
X is B or Al and
Rw, Rx, Ry and Rzare independently halogen, CrC2oalkyl, CrC2oalkyl which is partly or fuliy fiuorinated, Ci-C2oalkoxy, CrC2oaikoxy which is partly or fuliy fiuorinated, Ci-C2oaikyl-COO or CrC2oalkyl-COO which is partly or fully fiuorinated and
O ^O is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxyiic acid or from a 1 ,2- or 1 ,3-hydroxycarboxylic acid and
where any one CF2 group may be replaced by O, S(0)2, NR or CH2. The anions of ionic liquids may include F2P(C2F5) ", FsP^Fs , F^CaFs ', F2P(C3F7) ', F3P(C3F7)3", F4P(C3F7)2", F2P(C4F9) ', F3P(C4F9)3-, F4P(C4F9)2-, perfluoroalkylcarboxylate, perfluoroaikylsulfonaie, bis(perfluoroalkylsulfonyl)imide,
(perfluoroalkyisulfonyi)(perfluoroaikylcarboxyl)imide, iris(perfiuoroalkylsulfonyl)meihide, trifiuoroacetate, trifiuoromethanesuifonate (inflate), bis(trifluoromethylsulfonyl)imide,
tris(trifluoromethylsulfonyl)methide, tetrafiuoroborate, spiro-oxo borates and spiro-oxo phosphates, for example bisoxaiatoborate (BOB), difiuorooxalatoborate (dFOB),
di(trifluoroacetato)oxalatoborate (d(Ac)OB), trisoxalatophosphate, tetrafluorooxaiatophosphate and di(trifiuoroacetato)oxaiatoaluminate.
The electrolyte composition may be "non-aqueous", containing essentially no inadvertent water, for instance < 1000 ppm, < 100 ppm or < 10 ppm by weight water, based on the total weight of the electrolyte composition.
The electrolyte compositions may advantageously be "anhydrous", that is, containing little or no water. The electrolyte compositions may contain < 10 ppm water, for instance < 9, < 8, < 7, < 6, < 5 or < 4 ppm wafer by weight, based on the total weight of the electrolyte composition.
The electrolyte composition may advantageously contain a solvent. Alternatively, the electrolyte composition may contain no solvent. For instance, solvents are not required when one or more ionic liquids are employed in the electrolyte composition. "No solvent" means no organic solvent is present and essentially no inadvertent water is present.
Where a solvent is present in the electrolyte composition, the weightweight ratio of ionic compounds in total to solvent may be from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 80:40 to about 40:80.
The present electrolyte compositions may not be limited by the hydrogen and oxygen evolution potential of water. Thus, the electrochemical cells disclosed may exhibit a nominal open-circuit voltage of > 1.2 V (volts). The present cells may supply a nominal open-circuit voltage up to about 8 V. For instance, present cells may exhibit a nominal open-circuit voltage of from about 1.2 to about 8.0 V, from about 1.3 to about 6.0 V, from about 1.4 to about 6.0 V or from about 1.5 to about 6.0 V. For instance, present ceils may exhibit a nominal open-circuit voltage of about 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1 , 3.2, 3.3, 3,4, 3,5, 3.8, 3.7, 3.8, 3.9, 4.0, 4,1 , 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1 , 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9 or about 6.0 V.
Solvents are wafer and organic solvents. The solvent may consist essentially of water or may consist essentially of organic solvent. The solvent may contain varying ratios of water: organic solvent.
When the solvent consists essentially of organic solvent, water may only be present at very low levels, for example < 1000 ppm,≤ 100 ppm or < 10 ppm by weight water, based on the total weight of the electrolyte composition. When the solvent consists essentially of water, organic solvents may only be present at the same low levels.
For example the solvent may be a water/organic solvent mixture where the weight:weight ratio of waier io organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 80:40 to about 40:80.
The electrolyte composition may contain organic solvent and no water. The electrolyte composition may contain water and no organic solvent.
Suitable organic solvents are for instance selected from the group consisting of organic carbonates, ethers, glymes, ortho esters, polyalkylene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents, nitrile solvents and combinations thereof.
Organic carbonates are cyclic or acyclic and include ethylene carbonate (EC), propylene carbonate (PC), trimethylene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), vinyiene carbonate,
difluoroethylene carbonate and monofluoroethylene carbonate.
Ethers and glymes include dimethoxymethane (DM ), dieihoxymethane, 1 ,2- dimethoxyethane (DME or ethyleneglycol dimethylether or glyme), diglyme, triglyme, tetrag!yme, efhyleneglycol diethylether (DEE), ethyleneglycol dibutylether, diethyleneglycoi diethylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1 ,3-dioxane, 1 ,3-dioxolane (DIOX), 4-methyl-1 ,3-dioxolane (4-MeDIOX), 2-methyl-1 ,3-dioxolane (2-MeDIOX), 1 ,4-dioxane, dimethylether, ethylmethylether, diethylether, di-n-butylether, di-t-butylether, di-isopropylether, methyi-t-butyiether, ethyl~t-butylether and t-amyi-methylether.
Ortho esters include trimetboxymethane, triethoxymethane, 1 ,4-dimethyl-3,5,8- trioxabicyclo[2.2.2]octane and 4-ethyl-1-methyl-3,5,8-trioxabicyclo[2.2.2Joctane.
Polyalkylene glycols are homo- or cooligomers or homo- or copolymers of d-C^alkylene glycols. For instance, polyethylene glycol (PEG) or monomethyl, dimethyl or diethyl (end- capped) polyethylene glycol. Weight average molecular weights (Mw) of polyalkylene glycols are for example from about 200 to about 1200 g/mol, from about 200 to about 1000 g/mol, from about 200 to about 900 g/mol, from about 200 to about 700 g/mol or from about 200 to about 500 g/moL Included are oligomers of 4 monomers and more, for instance tetraethylene glycol, fiuorinated tetraethylene glycol and tefrapropylene glycol. For instance PEG 200, PEG 300, PEG 400, PEG 500, PEG 600, PEG 700, PEG 800, PEG 900 or PEG 1000.
Esters and lactones include γ-butyroiactone (GBL), γ-valeroiactone, δ-valerolactone, ethyl acetate (EA), 2-methoxyefhyl acetate, 2-ethoxyethyi acetate, 2-butoxyethyl acetate, 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EG DA), 3-ethoxy ethyl propionate (EEP), methyl butyrate (MB), n-amyi acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate, dimethyl malonate and dibasic ester mixture (DBE).
Dibasic ester mixture includes for instance methyl esters of adipic, giutaric and succinic acids.
Glycols include ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2- propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol (ethylene glycol butyl ether, EB), 2- phenoxyethanoi, 2-benzyioxyethanoi, 2-(2-methoxyethoxy)ethanol, 2-(2~ethoxyethoxy)ethanoi, 2-(2-butoxyethoxy)ethanol (diethylene glycol butyl ether, DB), propylene glycol butyl ether (PB), propylene glycol methyl ether (PM), triethylene glycol (TEG), dipropylene glycol methyl ether (DPM), diethylene glycol methyl ether, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, perfluoro-1 ,4-butanediol, perfluoro-1 ,5-butanediol, fiuorinated diethylene glycol methyl ether, fiuorinated triethylene glycol, fiuorinated triethylene glycol methyl ether and fiuorinated diethylene glycol butyl ether.
Formates include methyl formate, ethyl formate, isobutyi formate and tert-butyl formate.
Sulfones and sulfoxides include methylsulfonylmethane (MSM or dimethylsulfone), ethylmethylsulfone, sulfolane and dimethylsulfoxide (DMSO).
Amides include dimethylformamide (DMF), dimethylacetamide (DMA), N-methylpyrrolidone (NMP), 2-pyrrolidone, 1 ,3-dimethyl-2-imidazolidinone (DMI), hexamethylphosphoramide (HMPA) and N,N'-dimethyl-N,N'-trimethyleneurea (1 ,3-dimethyl-3,4,5,6-tetrahydro-2(1 H)- pyrimidinone (D PU)).
Alcohols include for example benzylaicohol (BA), ethanol, trifluoroethanol (2,2,2- trifluoroethanoi), methanol, isopropanol, t-butanol and n-butanol.
Ketones include for example methylethylketone (MEK) and methyl-isoamylketone (MIAK).
Nitro solvents include nitrobenzene, nitromethane and nitroethane.
Nitrile solvents include acetonitrile, propionitrile, butyronitrile and adiponitrile.
Advantageously, a mixture of solvents is employed, for instance a mixture of organic carbonates or a mixture of one or more organic carbonates and one or more ether or glyme. Other organic solvents may be employed, for instance common non-polar organic solvents including toluene, hexane, heptane and the like.
The electrolyte composition may advantageously comprise an ionic liquid and a protic acid and/or an organic solvent.
Present electrolyte compositions are for instance liquid at room temperature (25°C). Liquid includes syrupy high viscosity liquids. For example, the electrolyte compositions have a viscosity of from about 0.2 cP to about 100 cP at 25°C. For example the electrolyte
compositions have a viscosity of < 100 cP, < 90 cP, < 80 cP, < 70 cP, < 50 cP, < 40 cP, < 30 cP, < 20 cP, < 10 cP or < 5 cP at 25°C.
Viscosity may be measured for instance with a rotational rheometer or with a
microviscometer employing a roiling steel bail in a glass capillary timed and calibrated against control liquids. Viscosity may also be measured with a DVI or DVil Brookfieid viscometer, a plate viscometer or an oscillating type viscometer.
The electrolyte composition may further comprise one or more additives selected from the group consisting of corrosion inhibitors, solid electrolyte interface (SEi) improvers, proton evolution improvers, self-discharge inhibitors, anti-gassing agents, viscosity adjusting agents, cathode protection agents, salt stabilizers, conductivity improvers and solvating agents.
For instance, the electrolyte composition may contain one or more additives selected from the group consisting of
fiuorinated oil, sodium sfannate, sodium citrate or poiyacryiic acids;
HF or KF, oxides or hydroxides of rare earths such as Y, metal porphines, for example Ni or Fe porphine, vinyiene carbonate, vinyiethylene carbonate, methylene ethylene carbonate or fiuoro- ethylene carbonate;
poiygiycois, poiygiycoi alkyi ethers, polyglycol alkyl phosphate esters or polysorbates such as polyethylene glycol (PEG), polypropylene glycol, polysorbate 20, poiysorbate 40 or polysorbate 80 or a mixture of PEG 600 and polysorbate 20 or a mixture of PEG 600 and ZnO;
phosphate ester-based surfactants, propane sultone o fluoropropane sultone; and
D SO;
for example at a level of from about 0.1 % to about 15% by weight, based on the total weight of the electrolyte composition.
Group IV elements, for example silicon with a molecular weight of 28 g/moi, are much lighter than conventional metal hydride alloys. Typical AB2 and AB5 alloys have a molecular weight of about 70 g/mol. The present electrochemical cells have a higher gravimetric energy density and/or higher volumetric energy density than conventional metal hydride batteries. Present rechargeable cells may exhibit a gravimetric energy density of > 100 Wh/kg, For instance, the gravimetric energy density is > 1 10 Wh/kg, > 115, > 120, > 125, > 130, > 135, > 140,≥ 145,≥ 150,≥ 155, > 160,≥ 165,≥ 170,≥ 175,≥ 180,≥ 185,≥ 190,≥ 195 or > 200 Wh/kg.
Present rechargeable ceils may exhibit a volumetric energy density of > 250 Wh/L, for instance, the volumetric energy density is > 260 Wh/kg, > 265, > 270, > 275, > 280, > 285, > 290,≥ 295,≥ 300,≥ 305,≥ 310,≥ 315,≥ 320,≥ 325,≥ 330,≥ 335,≥ 340,≥ 345 or≥ 350 Wh/kg.
Present anodes may exibit a discharge capacity of > 800 mAh/g over 20 cycles or more (over at least 20 cycles), for example > 810, > 820, > 825, > 830, > 835, > 840, > 845, > 850, > 855, > 860, > 865, > 870, > 875, > 880 or > 895 mAh/g over 20 cycles or more; based on the weight of the hydrogen storage material.
"Negative electrode for electrochemical uses", "electrochemical cells" and "electrochemical devices" means as an electrode for solid hydrogen storage media devices, batteries, fuel cells, air battery systems and the like.
U.S. Patents, U.S. published patent applications and U.S. patent applications discussed herein are each hereby incorporated by reference.
The articles "a" and "an" are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an ionic liquid" means one ionic liquid or more than one ionic liquid.
Any ranges cited herein are inclusive.
The terms "substantially" and "about" used throughout this specification are used to describe and account for small fluctuations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, less than or equal to ±1 %, less than or equal to ±0.5%, less than or equal to ±0.2%, less than or equal to ±0.1 % or less than or equal to ±0.05%. All numeric values herein are modified by the term "about," whether or not explicitly indicated. A value modified by the term "about" of course includes the specific value. For instance, "about 5.0" must include 5.0.
Ail measurements herein are performed at ambient conditions, 25°C and 1 atm of pressure, unless otherwise indicated.
Brief Description of the Drawings
Fig. 1 shows electrochemical performance of the cell of Example 1 after 25 formation cycles. The anode contains a 250 nm a-Si film on a nickel substrate. The cathode is sintered nickel hydroxide on a nickel mesh substrate. The electrolyte composition is 2 molar acetic acid in 1-ethyl-3-methylimidazo!ium acetate. The cell is cycled at a charge/discharge current density of 387 mA/g.
Following are some embodiments of the invention.
E1. A stable group IV element-based hydrogen storage negative electrode for electrochemical uses; for example a stable silicon-based or carbon-based hydrogen storage negative electrode for electrochemical uses; for example where the electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn, based on the total weight of the hydrogen storage material.
E2. An electrode according to embodiment 1 comprising a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn; for example comprising > 27 wt% silicon or > 27 wt% carbon, based on the total weight of the hydrogen storage material.
E3, An electrode according to embodiments 1 or 2 where the hydrogen storage material comprises amorphous silicon, microcrystalline silicon, nanocrystalline silicon, monocrystalline silicon, polycrystalline silicon, protocrysfalline silicon or porous silicon.
E4, An electrode according to any of the preceding embodiments where the hydrogen storage material comprises amorphous silicon.
E5, An electrode according to any of the preceding embodiments where the hydrogen storage material comprises carbon; for example carbon in the form of natural graphite, artificial graphite, expanded graphite, graphene, carbon fiber, hard carbon, soft carbon, non-graphitizable carbon, carbon black, carbon nanotube, fuilerene, activated carbon, crystalline carbon or amorphous carbon.
E6, An electrode according to any of the preceding embodiments where the hydrogen storage material comprises an alloy of silicon and one or more of carbon, germanium and tin, for example amorphous silicon carbide or an alloy of silicon and germanium or an alloy of silicon and tin.
E7. An electrode according to any of the preceding embodiments comprising a hydrogen storage material which is hydrogenated prior to or after assembly of the electrode (a pre- hydrogenated negative electrode); for example where the hydrogen storage material is hydrogenated amorphous silicon (a-Si:H) or hydrogenated amorphous silicon carbide (a-Sii- xCx:H, where x is for example from about 0.01 to about 0.99, from about 0.05 to about 0.95 or from about 0.1 to about 0.9).
ES. An electrode according to any of the preceding embodiments where the hydrogen storage material, for example amorphous silicon, is comprised in a film, for example a film with a thickness > 20 nm, > 50 nm,≥ 90 nm, > 120 nm or≥ 180 nm or from about 90 nm to about 10 μηι, from about 100 nm to about 5 μιη, from about 150 nm to about 3 μητι, from about 150 nm to about 2 μίπ or from about 150 nm to about 1 μητι.
E9, An electrode according to any of the preceding embodiments where the hydrogen storage material is comprised in a film in adherence to a substrate, for example a substrate selected from metal, glass, inorganics and plastic.
E10. An electrode according to any of the preceding embodiments where the hydrogen storage material comprises one or more further elements, for example one or more elements selected from the group consisting B, Al, Ga, In, As, Sb, Te and transition metals.
E11. An electrode according to any of the preceding embodiments where the hydrogen storage materia! contains > 28 wt%,≥ 29 wt%, > 30 wt%,≥ 35 wt%,≥ 40 wt%, > 45 wt%,≥ 50 wt%,≥ 55 wt%, > 60 wt%, > 65 wt%, > 70 wt%, > 75 wt%, > SO wt%, > 85 wt%, > 90 wt%, > 95 wt%, > 96 wt%, > 97 wt%, > 98 wt% or > 99 wt% of one or more elements selected from the group consisting of group IV elements, for example Si and/or C, based on the total weight of the hydrogen storage material.
E12. An electrode according to any of the preceding embodiments comprising > 30% by weight of the one or more group IV elements; for example > 35%, > 40%,≥ 45%, > 50%, > 55%, > 60%, > 65%, > 70%, > 75% > 80%, > 85% or > 90% by weight of the one or more group IV elements, for example Si and/or C, based on the total weight of the negative electrode.
E13. An electrode according to any of the preceding embodiments further comprising one or more components selected from the group consisting of binders, conductive materials and other additives.
E14. An electrode according to any of the preceding embodiments comprising a solid electrolyte interface capable of allowing transport of protons.
E15. An electrode according to any of the preceding embodiments where the hydrogen storage material includes one or more further elements selected from the group consisting of structural modifiers (elements to promote the amorphous phase of a material), hydrogen bond strength modifiers and solid electrolyte interface (SEI) modifiers; for example one or more further elements selected from the group consisting of B, alkaline earth metals, transition metals, rare earth metals, other metals of groups III or V of the periodic table, O, F, P, CI and the like.
E16. An electrode according to any of the preceding embodiments in contact with an electrolyte composition which is neutral or acidic, for example having a pH of about 7 or lower; for example from about 1 , from about 2, from about 3, from about 4, from about 5 or from about 6 to about 7, E17. An electrode according to embodiment 18 where the electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, profic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotic oxonium compounds, aprotic phosphonium compounds and alkali or alkali earth metal salts. E18. An electrode according to embodiments 16 or 17 where the electrolyte composition comprises an ionic compound containing a cation selected from the group consisting of NhV" (ammonium), mefhylammonium, ethylammonium, dimeihylammonium, diethylammonium, trimethylammonium (NMe3H+), triethylammonium, tributylammonium, diethylmethylammonium, hydroxyethyiammonium, methoxymethylammonsum, dibutyiammonium, methylbutylammonium, anilinium, pyridinium, 2-methylpyridinium, imidazolium, 1-methyiimidazolium, 1 ,2- dimethylimidazolium, imidazolinium, 1-ethylimidazolium, 1-(4-sulfobutyl)-3-methylimidazolium, l-allylimidazolium, quinolinium, isoquinolinium, pyrrolinium, pyrrolininium or pyrrolidinium;
1-butyl-1-methylpyrrolidinium, tetramethylammonium, tetraethylammonium, tetra-n- butylammonium, n-butyl-tri-ethylammonium, benzyl-tri-methylammonium, tri-n- butylmethylammonium, benzyl-tri-ethylammonium, 1-methylpyridinium, 1-butyl-3,5- dimethylpyridinium, 1 ,2,4-trimethylpyrazolium, trimethylhydroxyethylammonium (choline), tri- (hydroxyethyl)methyiammonium, dimethyl-di(polyoxyethylene)ammonium, 1 ,2,3- trimethylimidazolium, 1-buiyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazoiium, 1-allyl-3- methylimidazolium, 1-hydroxyethyl-3-methylimidazolium, 1 ,3-dimethylimidazolium, 1 -ethyl- 1- methylpiperidinium, 4-ethyl-4-methylmorpholinium, 1-(cyanomethyl)-3-methylimidazolium, 1-(3- cyanopropyl)pyridinium, 1 ,3-bis(cyanomethyl)imidazolium, 1-hexyl-3-methylimidazolium or 1- ethyl-S-methylimidazoiium; and
methyltriphenylphosphonium, tetraphenylphosphonium, tetrabutylphosphonium,
tributylmethylphosphonium, triethylmethylphosphonium, trihexyiietradecylphosphonium, triphenylpropylphosphonium or tetrakis(hydroxymethyl)phosphonium;
for instance, the cation is 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-butyl-1- methylpyrrolidinium or trihexyl(tetradecyl)phosphonium.
E19. An electrode according to any of embodiments 16-18 where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of carboxylates, imides, methides, nitrate, bifluoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aluminates.
E20. An electrode according to any of embodiments 16-19 where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of
[FzB(CmF2m+i)4-z]-, [FyP(CmF2nHi)e-y]-, [(CrpF2!,1+i)2P(0)0]-, [CmF2rp+i P(0)02] 2-, [0-C(0)-CmF2m+i]-,
[0-S(0)2-CmF2m+l]", [N(C(0)-C mF2m+i)2]", [N(S(0)2-CmF2[n+l)2]", [N(C(0)-CmF2m+l)(S(0^2-CmF2m+1^]",
[N(C(0)-CmF2m+1)(C(0)F)l-, [N(S(0)2-Cn,F2m+i)(S(0)2F)]-, [N(S(0)2F)2]-, [C(C(0)-CmF2m+i)3]-, [C(S(0)2-CmF2m+i)3]-,
Figure imgf000030_0001
Figure imgf000030_0002
where
y is an integer of 1 to 6,
m is an integer of 1 to 8, for instance 1 to 4,
z is an integer of 1 to 4,
X is B or Al and
Rw, Rx, Ry and Rzare independently halogen, CrC20alkyl, CrC20alkyl which is partly or fuliy fluorinated, Ci-C20alkoxy, CrC2oalkoxy which is partly or fuliy fiuorinated, Ci-C20aikyl-COO or CrC20alkyl-COO which is partly or fully fluorinated and
O ^O is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxyiic acid or from a 1 ,2- or 1 ,3-hydroxycarboxylic acid and
where any one CF2 group may be replaced by O, S(0)2, NR or CH2.
E21. An electrode according to any of embodiments 16-20 where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of F2P(C2F5)4\ F3P(C2F5)3-, F4P(C2F5)2-, F2P(C3F7)4-, F3P(C3F7)3-, F4P(C3F7)2-, F2P(C4Fe)4-,
F3P(C4F9)3 ", F P(C4F9)2\ perfluoroalkylcarboxylate, perf!uoroalkylsulfonate,
bis(perfiuoroaikylsulfonyi)imide, (perfluoroaikylsuifonyl)(perfiuoroaikylcarboxyi)imide, tris(perfluoroalkylsulfonyl)methide, trifluoroacetate, trifluoromethanesulfonate (inflate), bis(trifiuoromethyisulfonyi)imide, tris(trifluoromethylsulfonyl)methide, tetrafluoroborate or a spiro- oxo borate or spiro-oxo phosphate, for example bisoxalatoborate (BOB), difiuorooxalatoborate (dFOB), di(trifiuoroacetato)oxalatoborate (d(Ac)OB), trisoxaiatophosphate,
tetrafluorooxaiatophosphate and di(trifluoroacetato)oxalatoaluminate,
E22. An electrode according to any of embodiments 18-21 where the electrolyte composition comprises an ionic compound containing a carboxylate anion of formula RCOO" where R is hydrogen or hydrocarbyi; such as formate, acetate (ethanoate), acrylate, propanoate, n- butanoate, i-butanoate, n-pentanoate, i-pentanoate, octanoaie, decanoate, benzoate, salicylate, ihiosalicylate, 2~, 3- or 4-nitrobenzoate; citrate, oxalate, tartrate, glycoiate, gluconate, rna!ate, mandelate, a carboxyiate of nitrilotriacetic acid, a carboxylate of N-(2-hydroxyethyi)- ethylenedsamsnetriacetic acid, a carboxyiate of ethyienediaminetetraacetic acid, a carboxylate of diethylenetriaminepentaacetic acid or a haloalkyicarboxylate such as fluoroacetate,
difluoroacetate, trifluoroacetate, chioroacetate, dichloroacetate or frichioroacetate.
E23. An electrode according to any of embodiments 16-22 where the electrolyte composition comprises an ionic compound containing
an imide anion such as dicyanamide, N(S02F)2 ~ ((bisfluorosuifonyl)irr!ide), a
bis(perfluoroalkylsulfonyl)imide such as [Ν(802ΟΡ3)2]'"' (bistriflimide),
bis(pentafluoroethylsulfonyi)imide or (CF3S02)(CF3(CF2)?,SQ2)~ or a
(perfluoroalkylsulfonyl)(perfluoroalkylcarboxyl)imide; or
a methide such as a tris(perfluoroalkyisulfonyl)methide, for example
tris(trifluoromethylsulfonyl)methide, C(CF3S02)3~; or
bifluoride (HF2 ~); or
chloride, bromide, iodide or fluoride; or
a borate such as orthoborate, tetra hydroxy borate, tetraborate, tetraphenylborate, [B(3,5- (CF3)2C6H3)4]- (BARF), B(C204)2 ~ (bis(oxalato)borate) (BOB), difiuoro(oxalato)borate (dFOB), di(trifluoroacetato)oxalatoborate (D(Ac)OB), B(C6F5)4" or BF4 "' (tetrafluoroborate); or
a phosphate such as dihydrogen phosphate, hydrogen phosphate, alkyi phosphate, dialkyi phosphate, phosphate, PF6 " (hexafluorophosphate), HP03F- (fluorohydrogen phosphate), trisoxalatophosphate (TOP), tetrafluorooxalatophosphate (TFOP) or a
fluoro(perfluoroalkyl)phosphate such as F2P(C2F5)4", F3P(C2F5)3"
(tris(pentafluoroethyl)trifluorophosphate or FAP), F4P(C2FS)2~ F2P(C3F F3P(C3F7)3~
F4P(C3F7)2- F2P(C4F9)4- F3P(C4F9)3- or F4P(C4F9)2-; or
a sulfonate such as an alkyisulfonate, arylsuifonate or perfluoroalkylsulfonate, for instance trifluoromethanesulfonate (triflate), p-toluenesulfonate (tosylate) or meihanesulfonaie
(mesylate); or
a sulfate such as hydrogensuifate, sulfate, thiosulfate or an alkylsulfate such as methylsuifate or ethylsuifate; or
a carbonate anion such as carbonate, hydrogencarbonate or an alkyicarbonate such as methylcarbonate, ethylcarbonate or butylcarbonate; or
an aluminate such as AI(OC(CF3)3)4 ~, di(trifluoroacetato)oxalatoaluminate (d(Ac)OAI), tetrachioroaluminate, tetrafluoroaluminate, tetraiodoaluminate or tetrabromoaiuminate. E24. An electrode according to any of embodiments 16-23 where the electrolyte composition comprises an ionic liquid.
E25. An electrode according to any of embodiments 18-24 where the electrolyte composition comprises an ionic liquid selected from the group consisting of diethylmethylammonium trifiuoromethanesuifonate (DE A TfO), ethyiammonium nitrate, triethylammonium
methanesuifonate, 2-methylpyridinium trifiuoromethanesuifonate, ammonium fluoride, methylammonium nitrate, hydroxyethylammonium nitrate, ethyiammonium nitrate,
dimethylammonium nitrate, 1-methylimidazolium nitrate, 1-ethylimidazolium nitrate, t- butylammonium tetrafluoroborate, hydroxyethylammonium tetrafiuoroborate,
methylbutyiammonium tetrafluoroborate, triethylammonium tetrafiuoroborate, imidazolium tetrafluoroborate, 1-methylimidazolium tetrafiuoroborate, 1 ,2-dimethylimidazolium
tetrafiuoroborate, t-butylammonium inflate, 2-fluoropyridinium trifiate, hydroxyethylammonium trifiate, 1 ,2-dimethylimidazolium trifiate, imidazolium trifiate, 1-methylimidazolium
hydrogensulfate, 1-methylimidazolium chloride, 1-methylimidazolium trifiate, hydronium trifiate, methylammonium mesylate, ethyiammonium mesylate, buty!ammonium mesylate,
meihoxyeihyiammonium mesylate, dimethylammonium mesylate, dibutyiammonium mesylate, triethylammonium mesylate, dimethylethyiammonium mesylate, hydronium hydrogensulfate, ammonium hydrogensulfate, methylammonium hydrogensulfate, ethyiammonium
hydrogensulfate, propylammonium hydrogensulfate, n-buty!ammonium hydrogensulfate, t- butylammonium hydrogensulfate, dimethylammonium hydrogensulfate, diethyiammonium hydrogensulfate, di-n-buiylammonium hydrogensulfaie, methylbutyiammonium hydrogensulfate, ethylbutylammonium hydrogensulfate, trimethylammonium hydrogensulfate, triethylammonium hydrogensulfate, tributylammonium hydrogensulfate, dimethylethyiammonium hydrogensulfate, dibutyiammonium fluorohydrogen phosphate, triethylammonium fiuorohydrogen phosphate, tributylammonium fluorohydrogen phosphate, hydronium dihydrogen phosphate,
methylammonium dihydrogen phosphate, ethyiammonium dihydrogen phosphate,
propylammonium dihydrogen phosphate, n-butylammonum dihydrogen phosphate,
meihoxyeihyiammonium dihydrogen phosphate, dimethylammonium dihydrogen phosphate, dibutyiammonium dihydrogen phosphate, methylbutyiammonium dihydrogen phosphate, ammonium bifluoride, methylammonium bifiuoride, ethyiammonium bifluoride and
dimethylammonium bifluoride.
E26. An electrode according to any of embodiments 16-25 where the electrolyte composition comprises an ionic liquid selected from the group consisting of 1-ethyl-3-methylimidazolium trifiuoromethanesuifonate (EMIM TfO), 1-ethyi-3-methylimidazolium tetrafluoroborate (EMIM BF4), 1-ethyl-3-methylimidazolium bis(trifiuoromethylsulfonyl)imide (EMIM TFSI), 1-ethyi-3- methylimidazolium acetate (EMI Ac), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIM TfO), 1-butyl~3-methylimidazolium acetate (BMIM Ac), 1-butyl~3~methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), tri-n-butylmethylammonium methylsulfate, 1- ethyl-2,3-dimethylimidazolium ethylsuifate, 1-butyl-3-methylimidazolium thiocyanate, 1-butyl-3- methylimidazolium tetrachloroaluminate, 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3- methylimidazolium meihanesulfonaie, 1-butyl-3-methylimidazolium hydrogencarbonate, 1-butyl- 3-meihylimidazoiium hydrogensulfate, 1-butyl-3-methylimidazolium chloride, 1 ,2,3- trimethylimidazolium methylsulfate, tris-(hydroxyethyl)methylammonium methylsulfate, 1 ,2,4- trimethylpyrazolium methylsulfate, 1 ,3-dimethylimdiazolium hydrogencarbonate, 1 -ethyl-3- methylimidazolium hydrogencarbonate, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3- methylimidazolium tetrachloroaluminate, l-eihyl-S-methylimidazoiium thiocyanate, 1-ethyl-3- methylimidazoiium meihanesulfonaie, 1-ethyl-3-methylimidazolium hydrogensulfate, 1 -ethyl-3- methyiimidazoiium ethylsuifate, 1-ethyi-3-methylimidazolium nitrate, 1-butyipyridinium chloride, 1-ethyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methyiimidazolium hexafluorophosphaie, 1- buiyl-3,5-dimethylpyridinium bromide, 1-ethyi-3-meihylimidazolium
bis(pentafluoroethylsulfonyl)imide, 1-ethyl-2,3-dimeihylimidazoiium meihyicarbonate, carboxymethyl-tributylphosphonium bis(trifluoromethylsulfonyl)imide, N-carboxyeihyl- methyipyrroiidinium bis(trifluoromethylsulfonyl)imide, N-carboxymethyl-trimethylammonium bis(trifluoromethylsulfonyl)imide, N-carboxymethyl-methylpyridinium
bis(trifluoromethylsulfonyl)imide, hexyltrimethylammonium bis(trifluromethylsulfonyl)imide, teirabutylphosphonium meihanesulfonaie, triethylmeihylammonium meihyicarbonate, 1-ethyl-1- methylpiperidinium meihyicarbonate, 4-ethyl-4-meihylmorpho!inium meihyicarbonate, 1-butyl-1- methylpyrrolidinium meihyicarbonate, triethylmeihylammonium dibutylphosphate,
tributylmethylphosphonium dibutylphosphate, triethylmethylphosphonium dibutylphosphate, teirabutylphosphonium ieirafiuoroboraie, teirabutylphosphonium p-toluenesulfonate, tributylmethylphosphonium meihyicarbonate, 1-ethyi-3-meihylimidazolium hydrogencarbonate, tributylmethylammonium meihyicarbonate, tributylmethylammonium dibutylphosphate, 1 -ethyl-3- methyiimidazoiium dibutylphosphate, 1-butyl-3-methylimidazolium dibutylphosphate, 1- (cyanomeihyl)-3-meihylimidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-meihyiimidazoiium bis(trifluoromethylsulfonyl)imide, 1 -(3-cyanopropyi)-3- meihyiimidazoiium dicyanamide, 1-(3-cyanopropyl)pyridinium chloride, 1-(3- cyanopropyl)pyridinium bis(trifluoromethylsulfonyl)imide, 1 ,3-bis(cyanomethyl)imidazolium chloride, 1 ,3-bis(cyanomethyl)imidazolium bis(trifluoromethylsulfonyl)imide, 1 ,3- bis(cyanopropyl)imidazolium chloride, 1 ,3-bis(3-cyanopropyl)imidazoiium
bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphaie, 1 -butyl-3- methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3- methylimidazolium chloride, 1~ethyl-3-rnethyiimidazoiium bromide, 1-butyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium chloride, tributyimethylphosphonium methylsulfate, triethylmethylphosphonium dibutyiphosphate, trihexyltetradecylphosphonium
bis(triiluromethylsulfonyl)imide, trihexyltetradecylphosphonium bis(2,4,4- trimethylphenyl)phosphinate, trihexyltetradecylphosphonium bromide,
trihexyltetradecylphosphonium chloride, trihexyltetradecylphosphonium decanoate,
trihexyltetradecylphosphonium dicyanamide, 3-(triphenylphosphonio)propane-1 -sulfonate and 3- (triphenylphosphonio)propane-l-sulfonic acid tosyiate.
E27. An electrode according to any of embodiments 18-26 where the electrolyte composition comprises a protic acid; for example a protic acid such as
hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid or periodic acid; or
a bisulfate such as sodium bisulfate, potassium bisulfate or ammonium bisulfate; or
HAsFs, HBF4, H(OEt2)BF4, HPF6, ,H[N(S02CF3)2] or H[N(S02CF2CF3)2].
E28. An electrode according to any of embodiments 16-27 where the electrolyte composition comprises an organic protic acid such as a carboxylic acid of formula RCOOH where R is hydrogen or hydrocarbyi, for example formic acid, acetic acid, acrylic acid, fiuoroacefic acid, difluoroacetic acid, trifluoroacetic acid, chioroacetic acid, dichioroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methylbutanoic acid, valeric acid, hexanoic acid, hepfanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- or 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, giycolic acid, gluconic acid, malic acid, mandelic acid, nitriiotriacefic acid, N-(2-hydroxyethyl)-ethylenediaminetriacetic acid, ethylenediaminetetraacetic acid or diethyleneaminepentaacetic acid.
E29. An electrode according to any of embodiments 16-28 where the electrolyte composition comprises a protic sulfonic acid of formula RSO3H where R is alkyi or aryi or aikyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsuifonic acid, methanesuifonic acid or trifiuoromethanesuifonic acid.
ESQ. An electrode according to any of embodiments 18-29 where the electrolyte composition comprises a protic acid which is an oxonium ion associated with a highly non-coordinating ion such as Brookhart's acid (BARF acid), [H(OEt2)2][B[3,5-(CF3)2CeH3]4], [H(OEt2)2l[B(CsF5)4] (oxonium acid) or [H(OEt2)2][AI(OC(CF3)3)4].
E31. An electrode according to any of embodiments 16-30 where the electrolyte composition comprises at least two different ionic compounds; for example, where the electrolyte
composition comprises a protic ionic compound and an aprotic ionic compound;
two different protic ionic compounds;
two different aprotic ionic compounds;
two different salts;
two different ionic liquids;
a salt and an ionic liquid, for example a protic or aprotic ammonium salt or an alkali metal salt such as an alkai metal halide;
a protic acid, protic ammonium compound or a protic oxonium compound and an ionic liquid, for example a carboxyiic acid and an ionic liquid.
E32. An electrode according to any of embodiments 18-31 where the electrolyte composition comprises two different ionic compounds which contain an identical cation or an identical anion. E33. An electrode according to any of embodiments 16-32 where electrolyte composition comprises two different ionic compounds with a weight:weight ratio of from about 99.9:0.1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
E34. An electrode according to any of embodiments 16-33 where the electrolyte composition contains no organic solvent and < 1000 ppm, < 100 ppm or < 10 ppm water by weight, based on the total weight of the electrolyte composition; or where the electrolyte composition contains < 9, < 8, < 7, < 6, < 5 or < 4 ppm water by weight, based on the total weight of the electrolyte composition.
ESS. An electrode according to any of embodiments 16-33 where the electrolyte composition comprises a solvent.
E36. An electrode according to any of embodiments 18-33 where the electrolyte composition comprises a solvent consisting essentially of water.
E37. An electrode according to any of embodiments 16-33 where the electrolyte composition comprises a solvent consisting essentially of organic solvent.
ESS. An electrode according to any of embodiments 18-33 where the electrolyte composition comprises a solvent comprising water and an organic solvent.
E39. An electrode according to embodiment 38 where the weigb weight ratio of water to organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60. E40. An electrode according to any of embodiments 37-39 where the organic solvent comprises one or more solvents selected from the group consisting of organic carbonates, ethers, glymes, ortho esters, poiyaikiene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents and nitrile solvents.
E41. An electrode according to embodiment 40 where the electrolyte composition comprises an organic solvent such as
an organic carbonate, for example a cyclic or acyclic organic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), trimethylene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyimethyi carbonate (EMC), vinylene carbonate, difluoroethylene carbonate or monofluoroethylene carbonate; or an ether or giyme such as dimethoxymethane (DMM), diethoxymethane, 1 ,2-dimethoxyefhane (DME or ethyleneglycol dimethyiether or glyme), diglyme, trigiyme, tetragiyme, ethyleneglycol diethylether (DEE), ethyleneglycol dsbutylether, dsethyieneglycol diethylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1 ,3-dioxane, 1 ,3-dioxolane (DIOX), 4-methyl-1 ,3- dioxolane (4-MeDIOX), 2-methyl-1 ,3-dioxoiane (2-MeDIOX), 1 ,4-dioxane, dimethyiether, ethylmethylether, diethylether, di-n-butylether, di-t-butylether, di-isopropyiether, methyl-t- butylether, ethyl-t-butylether or t-amyl-methylether; or
an ortho ester such as trimethoxymethane, triethoxymethane, 1 ,4-dimethyl-3,5,8- trioxabicyclo[2.2.2]octane or 4-ethyl-1-methyl-3,5,8-trioxabicyclo[2.2.2]octane; or
a polyalkyiene glycol, that is a homo- or cooligomer or homo- or copolymer of CrC4aikyiene glycols, such as polyethylene glycol (PEG) or monomethy!, dimethyl or diethyl (end-capped) polyethylene glycol with weight average molecular weights (Mw) for example from about 200 to about 1200 g/mol, from about 200 to about 1000 g/mol, from about 200 to about 900 g/mol, from about 200 to about 700 g/mol or from about 200 to about 500 g/mol, for example oligomers of 4 monomers or more, for instance tetraethylene glycol, fluorinated tetraethylene glycol or tetrapropylene glycol, for instance PEG 200, PEG 300, PEG 400, PEG 500, PEG 600, PEG 700, PEG 800, PEG 900 or PEG 1000; or
an ester or lactone such as γ-butyrolactone (GBL), γ-valerolactone, δ-valerolactone, ethyl acetate (EA), 2-methoxyethyl acetate, 2-ethoxyethyi acetate, 2-butoxyethyl acetate, 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EGDA), 3-ethoxy ethyl propionate (EEP), methyl bufyrate (MB), n-amyi acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate or dimethyl malonate; or
a dibasic ester mixture such as methyl esters of adipic, glutaric or succinic acids; or a glycol such as ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2- propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol (ethylene glycol butyl ether, EB), 2- phenoxyethanol, 2-benzyioxyethanoi, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol (diethylene glycol butyl ether, DB), propylene glycol butyl ether (PB), propylene glycol methyl ether (PM), triethylene glycol (TEG), dipropylene glycol methyl ether (DPM), diethylene glycol methyl ether, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, perfluoro-1 ,4-butanediol, perfluoro-1 ,5-butanediol, fluorinated diethylene glycol methyl ether, fluorinated triethylene glycol, fluorinated triethylene glycol methyl ether or fluorinated diethylene glycol butyl ether; or
a formate such as methyl formate, ethyl formate, isobutyl formate or tert-butyl formate; or a sulfone or sulfoxide such as methylsulfonylmethane ( SM or dimethy!su!fone),
ethylmethylsulfone, sulfolane or dimethylsulfoxide (D SO); or
an amide such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methyipyrroiidone (NMP), 2-pyrrolidone, 1 ,3-dimethyl-2-imidazolidinone (DMI), hexamethylphosphoramide (H PA) or N.N'-dimethyl-N.N'-trimethyleneurea (1 ,3~dimethyl-3,4,5,6 etrahydro-2(1 H)- pyrimidinone (DMPU)); or
an alcohol such as benzylalcohoi (BA), ethanol, trifluoroethanol (2,2,2-trifluoroethanol), methanol, isopropanol, t-butanol or n-butanol; or
a ketone such as methylethylketone (MEK) or methyl-isoamylketone (MIAK); or
a nitro solvent such as nitrobenzene, nitromethane or nitroethane; or
a nitrile solvent such as acetonitriie, propionitrile, butyronitrile or adiponitrile.
E42. An electrode according to any of embodiments 16-33 and 35-41 where the electrolyte composition comprises a solvent and where the weigh weight ratio of ionic compounds in total to solvent is from about 99.9:0, 1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 80:40 to about
40:60.
E43. An electrode according to any of embodiments 18-42 where the electrolyte composition further comprises one or more additives selected from the group consisting of corrosion inhibitors, solid electrolyte interface (SE!) improvers, proton evolution improvers, self-discharge inhibitors, anti-gassing agents, viscosity adjusting agents, cathode protection agents, salt stabilizers, conductivity improvers and solvating agents,
E44. An electrode according to any of embodiments 16-43 where the electrolyte composition contains one or more additives selected from the group consisting of
fluorinated oil, sodium stannate, sodium citrate or polyacrylic acids; HF or KF, oxides or hydroxides of rare earths such as Y, metal porphines, for example Ni or Fe porphine, vinylene carbonate, vinylethylene carbonate, methylene ethylene carbonate or fiuoro- ethylene carbonate;
polyglycols, polyglycol alkyl ethers, polyglycol alkyl phosphate esters or polysorbates such as polyethylene glycol (PEG), polypropylene glycol, polysorbate 20, polysorbate 40 or polysorbate 80 or a mixture of PEG 600 and polysorbate 20 or a mixture of PEG 600 and ZnO;
phosphate ester-based surfactants, propane sultone or fiuoropropane sultone; and
D SO;
for example at a level of from about 0.1 % to about 15% by weight, based on the total weight of the electrolyte composition.
E45. A rechargeable electrochemical ceil comprising a negative electrode according to any of embodiments 1-15, a positive electrode, a casing having said electrodes positioned therein and an electrolyte composition according to any of embodiments 16-44 in contact with the electrodes, where the gravimetric energy density of the cell is > 100 Wh/kg, > 1 10 Wh/kg,≥ 1 15,
> 120, > 125, > 130, > 135, > 140, > 145, > 150, > 155, > 160, > 165, > 170, > 175, > 180, > 185,
> 190, > 195 or > 200 Wh/kg and/or
where the volumetric energy density of the cell is > 250 Wh/L, for instance, > 260 Wh/kg, > 265, ≥ 270,≥ 275,≥ 280,≥ 285,≥ 290, > 295,≥ 300, > 305, > 310, > 315, > 320, > 325, > 330, > 335,
> 340, > 345 or > 350 Wh/kg and/or
where the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 cycles or more (over at least 20 cycles), for example > 810, > 820, > 825, > 830, > 835, > 840, > 845, > 850, > 855, > 860, > 865, > 870, > 875, > 880 or > 895 mAh/g over 20 cycles or more.
E48. A rechargeable electrochemical cell comprising a negative electrode according to any of embodiments 1-15, a positive electrode, a casing having said electrodes positioned therein and an electrolyte composition according to any of embodiments 16-44 in contact with the electrodes, where the reversible half cell charge/discharge electrochemical reaction at the negative electrode is or
mmmmmmm where
/V is a group IV element-based hydrogen storage material and
Si is a silicon-based hydrogen storage material.
E47. A rechargeable electrochemical ceil comprising a negative electrode according to any of embodiments 1-15, a positive electrode, a casing having said electrodes positioned therein and an electroiyie composition according to any of embodiments 18-44 in contact with the electrodes,
the positive electrode comprising one or more cathode active materials selected from the group consisting of transition metals, transition metal oxides, transition metal hydroxides, transition metal oxide/hydroxides and transition metal fluorides; for example one or more materials selected from the group consisting of
Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au;
oxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, ir, Pt or Au;
hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au;
oxide/hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au; and
fluorides Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au.
Following are more embodiments of the invention.
E1. An electrochemical cell comprising a stable group IV element-based hydrogen storage negative electrode; for example a stable silicon-based or carbon-based hydrogen storage negative electrode; for example where the negative electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn, based on the total weight of the hydrogen storage material;
the ceil also comprising an aqueous or non-aqueous electrolyte composition in contact with the electrode.
E2, A ceil according to embodiment 1 where the negative electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn; for example comprising > 27 wt% silicon or > 27 wt% carbon, based on the total weight of the hydrogen storage material.
E3. A ceil according to embodiments 1 or 2 where the hydrogen storage material comprises amorphous silicon, microcrystaliine silicon, nanocrystaliine silicon, monocrystailine silicon, polycrystalline silicon, protocrystal!ine silicon or porous silicon.
E4. A ceil according to any of the preceding embodiments where the hydrogen storage material comprises amorphous silicon. E5. A cell according to any of the preceding embodiments where the hydrogen storage material comprises carbon; for example carbon in the form of natural graphite, artificial graphite, expanded graphite, graphene, carbon fiber, hard carbon, soft carbon, non-graphitizable carbon, carbon black, carbon nanotube, fullerene, activated carbon, crystalline carbon or amorphous carbon.
E8. A cell according to any of the preceding embodiments where the hydrogen storage material comprises an alloy of silicon and one or more of carbon, germanium and tin, for example amorphous silicon carbide or an alloy of silicon and germanium or an alloy of silicon and tin. E7. A ceil according to any of the preceding embodiments where the hydrogen storage material is hydrogenated prior to assembly of the cell (a pre-hydrogenated negative electrode); for example where the hydrogen storage material is hydrogenated amorphous silicon (a-Si:H) or hydrogenaied amorphous silicon carbide (a-Sii.xCx:H, where x is for example from about 0.01 to about 0.99, from about 0.05 to about 0.95 or from about 0.1 to about 0.9).
E8. A ceil according to any of the preceding embodiments where the hydrogen storage material, for example amorphous silicon, is comprised in a film, for example a film with a thickness > 20 nm, > 50 nm, > 90 nm, > 120 nm or > 180 nm or from about 90 nm to about 10 μιτι, from about 100 nm to about 5 μπτι, from about 150 nm to about 3 μηη, from about 150 nm to about 2 μπι or from about 150 nm to about 1 μπη.
E9. A cell according to any of the preceding embodiments where the hydrogen storage material is comprised in a film in adherence to a substrate, for example a substrate selected from metal, glass, inorganics and plastic.
E10. A ceil according to any of the preceding embodiments where the hydrogen storage material comprises one or more further elements, for example one or more elements selected from the group consisting B, Ai, Ga, in, As, Sb, Te and transition metals.
E11. A ceil according to any of the preceding embodiments where the hydrogen storage material contains > 28 wt%,≥ 29 wt%, > 30 wt%,≥ 35 wt%,≥ 40 wt%, > 45 wt%,≥ 50 wt%,≥ 55 wt%, > 60 wt%, > 65 wt%,≥ 70 wt%, > 75 wt%,≥ 80 wt%,≥ 85 wt%,≥ 90 wt%,≥ 95 wt%,≥ 96 wt%, > 97 wt%, > 98 wt% or > 99 wt% of one or more elements selected from the group consisting of group IV elements, for example Si and/or C, based on the total weight of the hydrogen storage material.
E12. A ceil according to any of the preceding embodiments where the negative electrode comprises≥ 30% by weight of the one or more group IV elements; for example≥ 35%,≥ 40%, > 45%, > 50%, > 55%, > 60%, > 65%, > 70%, > 75% > 80%, > 85% or > 90% by weight of the one or more group IV elements, for example Si and/or C, based on the total weight of the negative electrode. E13. A cell according to any of the preceding embodiments where the negative electrode further comprises one or more components selected from the group consisting of binders, conductive materials and other additives.
E14. A ceil according to any of the preceding embodiments where the negative electrode comprises a solid electrolyte interface capable of allowing transport of protons.
E15. An cell according to any of the preceding embodiments where the hydrogen storage material includes one or more further elements selected from the group consisting of structural modifiers (elements to promote the amorphous phase of a material), hydrogen bond strength modifiers and solid electrolyte interface (SEI) modifiers; for example one or more further elements selected from the group consisting of B, alkaline earth metals, transition metals, rare earth metals, other metals of groups III or V of the periodic table, O, F, P, CI and the like.
E16. A ceil according to any of the preceding embodiments where the electrolyte composition which is neutral or acidic, for example having a pH of about 7 or lower; for example from about 1 , from about 2, from about 3, from about 4, from about 5 or from about 6 to about 7.
E17. A ceil according to any of the preceding embodiments where the electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, protic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotsc oxonium compounds, aprotic phosphonsum compounds and alkali or alkali earth metal salts.
E18. A ceil according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing a cation selected from the group consisting of NH4 + (ammonium), methylammonium, ethylammonium, dsmethylammonium, diethylammonium, trimethylammonium (NMe3H+), triethylammonium, tributylammonium, diethylmethylammonium, hydroxyethyiammonium, methoxymethylammonium, dibutyiammonium, methyibutylammonium, anslinium, pyridinium, 2-rrsethy!pyridsnium, imidazolium, 1-methylimidazoiium, 1 ,2- dimethylimsdazolium, imidazolinium, 1-ethylimidazolium, 1-(4-suifobutyl)-3-methylimidazoiium, 1-allylimidazolium, quinolinium, isoquinolinium, pyrrolinium, pyrrolininium or pyrrolidinium; 1-butyl-1-methylpyrrolidinium, fetramefhylammonium, tetraethylammonium, tetra-n- butylammonium, n-butyl-tri-ethylammonium, benzyl-tri-methylammonium, tri-n- buty! methylammonium, benzyl-tri-ethylammonium, 1-methylpyridinium, 1-butyl-3,5- dimethylpyridinium, 1 ,2,4-trimethyipyrazoiium, trimethylhydroxyethyiammonsum (choline), tri- (hydroxyethyl)methyiammonium, dimethyl-di(polyoxyethylene)ammonium, 1 ,2,3- trimethyiimidazolium, l-butyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-allyl-3- methyiimidazoiium, 1-hydroxyethyl-3-methyiimidazoiium, 1 ,3-dimethylimidazolium, 1 -ethyl- 1- methylpiperidinium, 4-ethyl-4-methylmorpholinium, 1-(cyanomethyl)-3-methylimidazolium, 1-(3- cyanopropyl)pyridinium, 1 ,3-bis(cyanomethyl)imidazolium, 1-hexyl-3-methylimidazolium or 1- ethyl-S-methyiimidazoiium; and
methyltriphenylphosphonium, tetraphenylphosphonium, tetrabutylphosphonium,
tributylmethylphosphonium, triethylmethylphosphonium, trihexyltetradecylphosphonium, tripheny!propyiphosphonium or ieirakis(hydroxymeihy!)phosphoniLfm;
for instance, the cation is 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-butyl-1- methylpyrrolidinium or trihexyl(tetradecyl)phosphonium.
E19. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of carboxylates, imides, methides, nitrate, bifluoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aluminates.
E20. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of
[FzB(CmF2m+i)4-z]-, [FyP(CmF2nHi)e-y]-, [(CrpF2!,1+i)2P(0)0]-, [CmF2rp+iP(0)02] 2-, [0-C(0)-CmF2m+i]-,
[0-S(0)2-CmF2[mi]-, [N(C(0)-CmF2m+i)2]-, [N(S(0)2-CmF2m+i)2]-, [N(C(0)-CmF2m+i)(S(0)rCmF2m+i)]-.
[N(C(0)-CmF2m+i)(C(0)F)]-, [N(S(0)2-CmF2m+i)(S(0)2F)]-, [N{S(0)2F)2]-, [C(C{0)-CFilF2m+ !)3]-,
Figure imgf000042_0001
Figure imgf000042_0002
where
y is an integer of 1 to 6,
m is an integer of 1 to 8, for instance 1 to 4,
z is an integer of 1 to 4,
X is B or Al and Rw, Rx, Ry and Rzare independently halogen, Ci-C20alkyi, CrC2oalkyi which Is partly or fully fluorinated, CrC2oaikoxy, CrC2oalkoxy which is partly or fully fiuorinated, Ci-C2oalkyl-COO or CrC2oalkyl-COO which is partly or fully fluorinated and
0 "~Ό is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxyiic acid or from a 1 ,2- or 1 ,3-hydroxycarboxylic acid and
where any one CF2 group may be replaced by O, S(0)2, NR or CH2.
E21. A ceil according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of F2P(C2F5)4-, F3P(C2F5)3-, F4P(C2F5)2-, F2P(C3F7)4-, F3P(C3F7)3', F4P(C3F7)2-, F2P(C4Fg)4-,
F3P(C4F9)3-, F P(C4F9)2 ' , perfluoroalkylcarboxylate, perfluoroalkylsulfonate,
bis(perfiuoroaikylsulfonyi)imide, (perfluoroalkylsulfonyl)(perfluoroalkylcarboxyl)imide, tris(perfluoroalkylsulfonyl)methide, trifluoroacetate, trifluoromethanesulfonate (triflate), bis(trifiuoromethylsulfonyl)imide, tris(trifluoromethyisLfifonyi)methide, tetrafluoroborate or a spiro- oxo borate or spiro-oxo phosphate, for example bisoxalatoborate (BOB), difluorooxalatoborate (dFOB), di(frifiuoroacetato)oxalatoborate (d(Ac)OB), trisoxaiatophosphate,
tetrafluorooxaiatophosphate and di(trifluoroacetato)oxalatoaluminate.
E22. A ceil according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing a carboxylate anion of formula RCQO where R is hydrogen or hydrocarbyl; such as formate, acetate (ethanoate), acrylate, propanoate, n- butanoate, i~butanoate, n~pentanoate, i~pentanoate, octanoate, decanoate, benzoate, salicylate, thiosalicylate, 2-, 3- or 4-nitrobenzoate; citrate, oxalate, tartrate, giycolate, gluconate, ma!ate, mandeiate, a carboxylate of nitrilotriacetic acid, a carboxylate of N-(2-hydroxyethyi)- ethylenediaminetriacetic acid, a carboxylate of ethylenediaminetetraacetic acid, a carboxylaie of diethylenetriaminepentaacefic acid or a haloalkyicarboxylate such as fluoroacetate,
difluoroacetate, trifluoroacetate, chioroacetate, dichloroacetate or trichioroacetate.
E23. A ceil according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing
an imide anion such as dicyanamide, N(S02F)2 " ((bisfluorosulfonyl)imide), a
bis(perfluoroaikylsulfonyl)imide such as [N(SG2CF3)2j~ (bistriflimide),
bis(pentafluoroethylsulfonyl)imide or N{GF3S02)(GF3(CF2)3S02)- or a
(perfluoroalkylsulfonyi)(perfiuoroaikylcarboxyi)imide; or
a methide such as a tris(perfluoroalkylsulfonyl)methide, for example
tris(trifluoromethylsulfonyl)methide, C(CF3S02)3 " ; or
bifluoride (HF2 ~); or
chloride, bromide, iodide or fluoride; or a borate such as orthoborate, tetrahydroxyborate, tetraborate, tetraphenylborate, [B(3,5- (CF3)2CSH3)4]- (BARF), B(C204)2 ~ (bis(oxa!ato)borate) (BOB), difiuoro(oxa!ato)borate (dFOB), di(trifluoroacetato)oxalatoborate (D(Ac)OB),
Figure imgf000044_0001
or BF4 ~ (tetrafluoroborate); or
a phosphate such as dihydrogen phosphate, hydrogen phosphate, alkyl phosphate, dialkyl phosphate, phosphate, PF6 " (hexafluorophosphate), HPO3F" (fiuorohydrogen phosphate), trisoxalatophosphate (TOP), tetrafluorooxalatophosphate (TFOP) or a
fluoro(perfluoroalkyl)phosphate such as F2P(C2Fs)4~, F3P(C2Fs)3~
(tris(pentafluoroethyl)trifluorophosphate or FAP), F4P(C2Fs)2", F2P C3F7)4~ F3P(C3F7)3~
F4P(C3F7)2", F2P(C4F9)4", F3P(C4F9)3- or F4P(C4Fg)2-; or
a sulfonate such as an a!kylsulfonate, arylsulfonate or perfluoroalkylsulfonate, for instance trif!uoromethanesu!fonate (triflate), p~toluenesulfonate (tosylate) or methanesuifonate
(mesylate); or
a sulfate such as hydrogensuifate, sulfate, thiosulfate or an aikylsuifate such as methylsuifate or ethylsulfate; or
a carbonate anion such as carbonate, hydrogencarbonate or an alkylcarbonate such as methyicarbonate, ethylcarbonate or butylcarbonate; or
an aluminate such as AI(OC(CF3)3)4 ~ di(trifluoroacetato)oxa!atoaluminate (d(Ac)OAI), tetrachloroaluminate, tetrafluoroaluminate, tetraiodoaluminate or tetrabromoaiuminate.
E24. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid.
E25. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of diethylmethyiammonium trifluoromethanesulfonate (DEMA TfO), ethylammonium nitrate, triethylammonium
methanesuifonate, 2-methylpyridinium trifluoromethanesulfonate, ammonium fluoride, methylammonium nitrate, hydroxyethylammonium nitrate, ethylammonium nitrate,
dimethylammonium nitrate, 1-methyiimidazoiium nitrate, 1-ethylimidazolium nitrate, t- butylammonium tetrafluoroborate, hydroxyethylammonium tetrafluoroborate,
methylbutylammonium tetrafluoroborate, triethylammonium tetrafluoroborate, imidazoiium tetrafluoroborate, 1-methylimidazolium tetrafluoroborate, 1 ,2-dimethylimidazolium
tetrafluoroborate, t-bufylammonium triflate, 2-fiuoropyridinium triflate, hydroxyethylammonium triflate, 1 ,2-dimethylimidazolium triflate, imidazoiium triflate, 1-methylimidazolium
hydrogensuifate, 1-methylimidazolium chloride, 1-methylimidazolium triflate, hydronium triflate, methylammonium mesylate, ethylammonium mesylate, butylammonium mesylate,
methoxyethyiammonium mesylate, dimethylammonium mesylate, dibutylammonium mesylate, triethylammonium mesylate, dimethylethylammonium mesylate, hydronium hydrogensuifate, ammonium hydrogensulfate, methy!ammonium hydrogensulfate, ethylammonium hydrogensulfate, propylammonium hydrogensulfate, n~butylammonium hydrogensulfate, t~ buiylammonium hydrogensulfate, dimethylammonium hydrogensulfate, diethylammonium hydrogensulfate, di-n-butylammonium hydrogensulfate, methylbuiylammonium hydrogensulfate, ethylbutyiammonium hydrogensulfate, trimethyiammonium hydrogensuifate, triethylammonium hydrogensuifate, tributylammonium hydrogensulfate, dimethylethyiammonium hydrogensulfate, dibutylammonium fiuorohydrogen phosphate, triethylammonium fluorohydrogen phosphate, tributylammonium fiuorohydrogen phosphate, hydronium dihydrogen phosphate,
methyiammonium dihydrogen phosphate, ethylammonium dihydrogen phosphate,
propylammonium dihydrogen phosphate, n-butylammonum dihydrogen phosphate,
methoxyefhylammonium dihydrogen phosphate, dimethylammonium dihydrogen phosphate, dibutylammonium dihydrogen phosphate, methylbuiylammonium dihydrogen phosphate, ammonium bifluoride, methyiammonium bifiuoride, ethylammonium bifluoride and
dimethylammonium bifluoride.
E26. A ceil according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of 1-ethyl-3-methylimidazoiium trifiuoromethanesuifonate (EMIM TfO), 1-ethyi-3-methylimidazolium fetrafluoroborate (EMI BF4), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI), 1 -ethyl-3- methylimidazolium acetate (EMIM Ac), 1-butyl-3-methylimidazolium trifiuoromethanesuifonate (BMIM TfO), 1-butyi~3-methylimidazolium acetate (BMIM Ac), 1-bufyl~3~methyiimidazoiium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), tri-n-butylmethylammonium methylsulfate, 1- ethyl-2,3-dimethylimidazolium ethylsuifate, 1-butyi-3-meihylimidazolium thiocyanate, 1-butyl-3- methylimidazolium tetrachloroaluminate, 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3- methyiimidazoiium meihanesuifonaie, 1-butyl-3-methylimidazolium hydrogencarbonate, 1-butyl- 3-meihylimidazoiium hydrogensuifaie, 1-butyl-3-methylimidazolium chloride, 1 ,2,3- trimethyiimidazoiium methylsulfate, tris-(hydroxyethyi)meihylammonium methylsulfate, 1 ,2,4- trimethylpyrazolium methylsulfate, 1 ,3-dimethylimdiazolium hydrogencarbonate, 1 -ethyl-3- methyiimidazoiium hydrogencarbonate, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3- methylimidazolium tetrachloroaluminate, 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3- methyiimidazoiium meihanesuifonaie, 1-ethyl-3-methylimidazolium hydrogensulfate, 1 -ethyl-3- methyiimidazoiium ethylsuifate, 1-ethyi-3-methylimidazolium nitrate, 1-butyipyridinium chloride, 1-ethyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium hexafluorophosphaie, 1- butyl-3,5-dimethylpyridinium bromide, 1-ethyl-3-methylimidazolium
bis(pentafluoroethylsulfonyi)imide, 1-ethyl-2,3-dimethylimidazoiium methylcarbonate, carboxymethyl-tributylphosphonium bis(irifluoromethylsulfonyl)imide, N-carboxyeihyl- methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, N-carboxymethyl-trimethylammonium bis(trifluoromethylsulfonyl)imide, N-carboxymethyl-methylpyridinium
bis(trifluoromethylsulfonyl)imide, hexyltrimethylammonium bis(trifluromethylsulfonyl)imide, tetrabutylphosphonium methanesulfonaie, triethylmethylammonium meihylcarbonate, 1-ethyl-1- meihylpiperidinium meihylcarbonate, 4-ethyl-4-methylmorpholinium meihylcarbonate, 1-butyl-1- methylpyrrolidinium meihylcarbonate, triethylmethylammonium dibutyiphosphate,
tributylmethylphosphonium dibutyiphosphate, triethylmethylphosphonium dibutyiphosphate, tetrabutylphosphonium teirafluoroboraie, tetrabutylphosphonium p-toluenesulfonate, tributylmethylphosphonium meihylcarbonate, 1-ethyi-3-methylimidazolium hydrogencarbonate, iributyimethyiammonium methyicarbonate, iributyimethyiammonium dibutyiphosphate, 1 -ethyl-3- methylimidazoiium dibutyiphosphate, 1-butyl-3-methylimidazolium dibutyiphosphate, 1- (cyanomethyl)-3-methylimidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-methylimidazolium bis(irifiuoromethylsulfonyl)imide, 1 -(3-cyanopropyl)-3- methylimidazolium dicyanamide, 1-(3-cyanopropyl)pyridinium chloride, 1-(3- cyanopropyl)pyridinium bis(trifluoromethylsulfonyl)imide, 1 ,3-bis(cyanomethyl)imidazoiium chloride, 1 ,3-bis(cyanomethyl)imidazolium bis(trifluoromethylsulfonyl)imide, 1 ,3- bis(cyanopropyl)imidazolium chloride, 1 ,3-bis(3-cyanopropyl)imidazolium
bis(triiiuoromeihylsulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3- methylimidazolium teirafluoroboraie, 1-eihyl-3-meihylimidazolium teirafluoroboraie, 1-ethyl-3- methyiimidazolium chloride, 1~eihyl-3-methyiimidazoiium bromide, 1-butyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium chloride, tributylmethylphosphonium methyisulfate, triethylmethylphosphonium dibutyiphosphate, trihexyltetradecylphosphonium
bis(irifluromeihylsulfonyl)imide, trihexyltetradecylphosphonium bis(2,4,4- trimethylphenyl)phosphinate, trihexyltetradecylphosphonium bromide,
trihexyltetradecylphosphonium chloride, trihexyltetradecylphosphonium decanoate,
trihexyltetradecylphosphonium dicyanamide, 3-(triphenylphosphonio)propane-1 -sulfonate and 3- (iriphenylphosphonio)propane-l-sulfonic acid tosylate.
E27. A cell according to any of the preceding embodiments where ihe electrolyte composition comprises a proiic acid; for example a protic acid such as
hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid or periodic acid; or
a bisulfaie such as sodium bisulfaie, potassium bisulfate or ammonium bisulfate; or
HAsFs, HBF4, H(OEt2)BF4, HPF6, ,H[N(S02CF3)2] or H[N(S02CF2CF3)2].
E28. A cell according to any of the preceding embodiments where the electrolyte composition comprises an organic proiic acid such as a carboxylic acid of formula RCOOH where R is hydrogen or hydrocarbyl, for example formic acid, acetic acid, acrylic acid, fluoroacetic acid, difiuoroacetic acid, trifluoroacetic acid, chloroacetic acid, dichioroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methylbutanoic acid, valeric acid, hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- or 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, giycolic acid, gluconic acid, malic acid, mandelic acid, nitrilotriacetic acid, N-(2-hydroxyethyl)-efhylenediaminetriacetic acid, ethyienediaminetefraacetic acid or diethyleneaminepentaacetic acid.
E29. A cell according to any of the preceding embodiments where the electrolyte composition comprises a protic sulfonic acid of formula RSO3H where R is alkyi or aryi or alkyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsulfonic acid, methanesuifonic acid or trifiuoromethanesuifonic acid.
E30. A ceil according to any of the preceding embodiments where the electrolyte composition comprises a protic acid which is an oxonium ion associated with a highly non-coordinating ion such as Brookhart's acid (BARF acid), [H(OEt2)2][B[3,5-(CF3)2C6H3]4], [H(OEt2)2][B(C6Fs)4]
(oxonium acid) or [H(OEt2)2][A!(OC(CF3)3)4].
E31. A cell according to any of the preceding embodiments where the electrolyte composition comprises at least two different ionic compounds; for example, where the electrolyte
composition comprises
a protic ionic compound and an aprotic ionic compound;
two different protic ionic compounds;
two different aprotic ionic compounds;
two different salts;
two different ionic liquids;
a salt and an ionic liquid, for example a protic or aprotic ammonium salt or an alkali metal salt such as an aikai metal halide;
a protic acid, protic ammonium compound or a protic oxonium compound and an ionic liquid, for example a carboxylic acid and an ionic liquid.
E32. A cell according to any of the preceding embodiments where the electrolyte composition comprises two different ionic compounds which contain an identical cation or an identical anion. E33. A ceil according to any of the preceding embodiments where electrolyte composition comprises two different ionic compounds with a weighfcweight ratio of from about 99.9:0.1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60. E34. A cell according to any of the preceding embodiments where the electrolyte composition contains no organic solvent and < 1000 ppm, < 100 ppm or < 10 pprn water by weight, based on the total weight of the electrolyte composition; or where the electrolyte composition contains < 9, < 8, < 7, < 6, < 5 or < 4 ppm water by weight, based on the total weight of the electrolyte composition.
ESS. A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent.
E38. A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of water.
E37. A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of organic solvent.
E38. A ceil according to any of embodiments 1-33 where the electrolyte composition comprises a solvent comprising water and an organic solvent.
E39. A ceil according to embodiment 38 where the weight:weight ratio of wafer to organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
E40. A cell according to any of embodiments 37-39 where the organic solvent comprises one or more solvents selected from the group consisting of organic carbonates, ethers, giymes, ortho esters, polyalklene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents and nitrile solvents.
E41. A ceil according to embodiment 40 where the electrolyte composition comprises an organic solvent such as
an organic carbonate, for example a cyclic or acyclic organic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), trimethyiene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), vinylene carbonate, difluoroethyiene carbonate or monofiuoroethyiene carbonate; or
an ether or glyme such as dimethoxymethane (DMM), diethoxymethane, 1 ,2-dimetboxyethane (DME or ethyieneglycoi dimethyiether or glyme), diglyme, triglyme, tetragiyme, ethyienegiycoi diethylether (DEE), ethyieneglycoi dibufylether, diethyieneglycol diefhylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1 ,3-dioxane, 1 ,3-dioxolane (DIOX), 4-methyl-1 ,3- dioxolane (4-MeDIOX), 2-metbyi-1 ,3-dioxoiane (2- eDIOX), 1 ,4-dioxane, dimethyiether, efhylmethylether, diethylether, di-n-butylether, di-t-butyiefher, di-isopropyiether, methyl-t- butylether, ethyl-t-butyiether or t-amyi-methylether; or an ortho ester such as trimethoxymethane, triethoxymethane, 1 ,4-dimethyl-3,5,8- trioxabicyclo[2.2.2]octane or 4~ethyl-1-methyi-3,5,8~trioxabicy o[2.2,2]octane; or
a polyalkylene glycol, that is a homo- or cooiigomer or homo- or copolymer of Crdalkylene glycols, such as polyethylene glycol (PEG) or monomethyl, dimethyl or diethyl (end-capped) polyethylene glycol with weight average molecular weights (Mw) for example from about 200 to about 1200 g/mol, from about 200 to about 1000 g/mol, from about 200 to about 900 g/mol, from about 200 to about 700 g/mol or from about 200 to about 500 g/mol, for example oligomers of 4 monomers or more, for instance tetraethyiene glycol, fiuorinated tetraethylene glycol or tetrapropylene glycol, for instance PEG 200, PEG 300, PEG 400, PEG 500, PEG 600, PEG 700, PEG 800, PEG 900 or PEG 1000; or
an ester or lactone such as γ-butyrolactone (GBL), γ-valerolactone, δ-valerolactone, ethyl acetate (EA), 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethy! acetate, 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EGDA), 3-ethoxy ethyl propionate (EEP), methyl butyrate ( B), n-amyl acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate or dimethyl malonate; or
a dibasic ester mixture such as methyl esters of adipic, glutaric or succinic acids; or
a glycol such as ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2- propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol (ethylene glycol butyl ether, EB), 2- phenoxyethanol, 2-benzyloxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol (diethylene glycol butyl ether, DB), propylene glycol butyl ether (PB), propylene glycol methyl ether (PM), Methylene glycol (TEG), dipropylene glycol methyl ether (DPM), diethylene glycol methyl ether, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, perfiuoro-1 ,4-butanediol, perfluoro-1 ,5-butanediol, fiuorinated diethylene glycol methyl ether, fiuorinated triethyiene glycol, fiuorinated triethylene glycol methyl ether or fiuorinated diethylene glycol butyl ether; or
a formate such as methyl formate, ethyl formate, isobutyi formate or tert-butyl formate; or a sulfone or sulfoxide such as methylsulfonyl methane (MSM or dimethylsuifone),
ethylmethylsulfone, suifolane or dimethyisuifoxide (DMSO); or
an amide such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methylpyrrolidone (NMP), 2-pyrrolidone, 1 ,3~dimethyl-2-imidazo!idinone (DMl), hexamethyiphosphoramide (HMPA) or N,N'-dimethyl-N,N'-trimethyleneurea (1 ,3-dimethyl-3,4,5,6-tetrahydro-2(1 H)- pyrimidinone (DMPU)); or
an alcohol such as benzylalcohol (BA), ethanol, trifluoroethanol (2,2,2-trifluoroethanol), methanol, isopropanoi, t-butanol or n-butanol; or a ketone such as methylethylketone (MEK) or methyl-isoamylketone (MIAK); or a nitro solvent such as nitrobenzene, nitromethane or nitroethane; or
a nitrile solvent such as acetonitrile, propionitrile, butyronitrile or adiponitrile.
E42. A cell according to any of embodiments 1-33 and 35-41 where the electroiyte composition comprises a solvent and where the weigh weight ratio of ionic compounds in total to solvent is from about 99.9:0,1 to about 0, 1 :99.9, from about 99.5:0.5 to about 0,5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
E43. A ceil according to any of embodiments 1-42 where the electrolyte composition further comprises one or more additives selected from the group consisting of corrosion inhibitors, solid electrolyte interface (SEI) improvers, proton evolution improvers, self-discharge inhibitors, anti- gassing agents, viscosity adjusting agents, cathode protection agents, salt stabilizers, conductivity improvers and solvating agents.
E44. A cell according to any of embodiments 1-43 where the electrolyte composition contains one or more additives selected from the group consisting of
fluorinated oil, sodium stannate, sodium citrate or poiyacrylic acids;
HF or KF, oxides or hydroxides of rare earths such as Y, metal porphsnes, for example Ni or Fe porphine, vinyiene carbonate, vinyiethylene carbonate, methylene ethylene carbonate or fluoro- ethylene carbonate;
poiyglycois, poiygiycoi alky! ethers, polyglycol alky! phosphate esters or polysorbates such as polyethylene glycol (PEG), polypropylene glycol, poiysorbate 20, polysorbate 40 or polysorbate 80 or a mixture of PEG 600 and poiysorbate 20 or a mixture of PEG 600 and ZnO;
phosphate ester-based surfactants, propane sultone or fluoropropane sultone; and
DMSO;
for example at a level of from about 0.1 % to about 15% by weight, based on the total weight of the electrolyte composition.
E45. A rechargeable electrochemical ceil according to any of the preceding embodiments comprising a positive electrode, a casing having the electrodes positioned therein and the electrolyte composition in contact with the electrodes, where the gravimetric energy density of the ceil is > 100 Wh/kg, > 1 10 Wh/kg, > 1 15, > 120, > 125, > 130, > 135, > 140, > 145, > 150, > 155, > 160, > 165, > 170, > 175, > 180, > 185, > 190, > 195 or > 200 Wh/kg and/or
where the volumetric energy density of the cell is > 250 Wh/L, for instance,≥ 260 Wh/kg,≥ 265,
> 270, > 275, > 280, > 285, > 290, > 295, > 300, > 305, > 310, > 315, > 320, > 325, > 330, > 335,
> 340, > 345 or > 350 Wh/kg and/or where the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 cycles or more (over at least 20 cycles), for example > 810, > 820, > 825, > 830, > 835, > 840, > 845, > 850, > 855, > 860, > 865, > 870, > 875, > 880 or > 895 mAh/g over 20 cycles or more.
E46. A rechargeable electrochemical cell according to any of the preceding embodiments comprising a positive electrode, a casing having the electrodes positioned therein and the electrolyte composition in contact with the electrodes, where the reversible half cell
charge/discharge electrochemical reaction at the negative electrode is
■■■■■■■HI or
bl + H + 6 ItfMMMMMtf 5/H
where
/V is a group IV element-based hydrogen storage material and
Si is a silicon-based hydrogen storage material,
E47. A cell according to any of the preceding embodiments comprising a positive electrode, the positive electrode comprising one or more cathode active materials selected from the group consisting of transition metals, transition metal oxides, transition metal hydroxides, transition metal oxide/hydroxides and transition metal fluorides; for example one or more materials selected from the group consisting of
Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au;
oxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, ir, Pt or Au;
hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt o Au;
oxide/hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, ir, Pt or Au; and
fluorides Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au.
Following are some more embodiments of the invention.
E1, A rechargeable electrochemical cell comprising a stable group IV element-based hydrogen storage negative electrode; for example a stable silicon-based or carbon-based hydrogen storage negative electrode; for example where the negative electrode comprises a hydrogen storage material comprising > 27 wt% or one or more elements selected from the group consisting of C, Si, Ge and Sn, based on the total weight of the hydrogen storage material; the cell also comprising a positive electrode, a casing having the electrodes positioned therein and an electrolyte composition in contact with the electrodes, where the reversible half cell charge/discharge electrochemical reaction at the negative electrode is
/V* "^" IH^ c?~ ^^^^^^^^^^^^^^^
or
Si + H+ + e- (ESSSSSSB S/'H
where
IV is a group IV element-based hydrogen storage material and
Si is a silicon-based hydrogen storage material.
E2. A ceil according to embodiment 1 where the negative electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn; for example comprising > 27 wt% silicon or > 27 wt% carbon, based on the total weight of the hydrogen storage material.
E3, A cell according to embodiments 1 or 2 where the hydrogen storage material comprises amorphous silicon, microcrystalline silicon, nanocrystalline silicon, monocrysfaliine silicon, polycrystalline silicon, protocrystailine silicon or porous silicon.
E4, A ceil according to any of the preceding embodiments where the hydrogen storage material comprises amorphous silicon.
E5, A ceil according to any of the preceding embodiments where the hydrogen storage material comprises carbon; for example carbon in the form of natural graphite, artificial graphite, expanded graphite, graphene, carbon fiber, hard carbon, soft carbon, non-graphitizabie carbon, carbon black, carbon nanoiube, fullerene, activated carbon, crystalline carbon or amorphous carbon.
E8. A cell according to any of the preceding embodiments where the hydrogen storage material comprises an alloy of silicon and one or more of carbon, germanium and fin, for example amorphous silicon carbide or an alloy of silicon and germanium or an alloy of silicon and tin. E7, A ceil according to any of the preceding embodiments where the hydrogen storage material is hydrogenated prior to assembly of the cell (a pre-hydrogenated negative electrode); for example where the hydrogen storage material is hydrogenated amorphous silicon (a-Si:H) or hydrogenated amorphous silicon carbide (a-Sii..xCx:H, where x is for example from about 0.01 to about 0.99, from about 0.05 to about 0.95 or from about 0.1 to about 0.9).
E8. A cell according to any of the preceding embodiments where the hydrogen storage material, for example amorphous silicon, is comprised in a film, for example a film with a thickness > 20 nm, > 50 nm, > 90 nm, > 120 nm or > 180 nm or from about 90 nm to about 10 μηι, from about 100 nm to about 5 μιη, from about 150 nm to about 3 μητι, from about 150 nm to about 2 μίπ or from about 150 nm to about 1 μητι.
E9, A cell according to any of the preceding embodiments where the hydrogen storage material is comprised in a film in adherence to a substrate, for example a substrate selected from metal, glass, inorganics and plastic.
E10. A cell according to any of the preceding embodiments where the hydrogen storage material comprises one or more further elements, for example one or more elements selected from the group consisting B, Al, Ga, In, As, Sb, Te and transition metals.
E11. A ceil according to any of the preceding embodiments where the hydrogen storage material contains > 28 wt%,≥ 29 wt%, > 30 wt%,≥ 35 wt%,≥ 40 wt%, > 45 wt%,≥ 50 wt%,≥ 55 wt%, > 60 wt%, > 65 wt%, > 70 wt%, > 75 wt%, > SO wt%, > 85 wt%, > 90 wt%, > 95 wt%, > 96 wt%, > 97 wt%, > 98 wt% or > 99 wt% of one or more elements selected from the group consisting of group IV elements, for example Si and/or C, based on the total weight of the hydrogen storage material.
E12. A ceil according to any of the preceding embodiments where the negative electrode comprises > 30% by weight of the one or more group IV elements; for example > 35%, > 40%, > 45%, > 50%, > 55%, > 60%,≥ 65%,≥ 70%,≥ 75% > 80%,≥ 85% or > 90% by weight of the one or more group IV elements, for example Si and/or C, based on the total weight of the negative electrode.
E13. A ceil according to any of the preceding embodiments where the negative electrode further comprises one or more components selected from the group consisting of binders, conductive materials and other additives.
E14. A ceil according to any of the preceding embodiments where the negative electrode comprises a solid electrolyte interface capable of allowing transport of protons.
E15. An cell according to any of the preceding embodiments where the hydrogen storage material includes one or more further elements selected from the group consisting of structural modifiers (elements to promote the amorphous phase of a material), hydrogen bond strength modifiers and solid electrolyte interface (SEI) modifiers; for example one or more further elements selected from the group consisting of B, alkaline earth metals, transition metals, rare earth metals, other metals of groups HI or V of the periodic table, O, F, P, CI and the like.
E16. A ceil according to any of the preceding embodiments where the electrolyte composition which is neutral or acidic, for example having a pH of about 7 or lower; for example from about 1 , from about 2, from about 3, from about 4, from about 5 or from about 6 to about 7.
E17. A cell according to any of the preceding embodiments where the electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, protic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotic oxonium compounds, aprotic phosphonium compounds and alkali or alkali earth metal salts.
E18. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing a cation selected from the group consisting of NH4 + (ammonium), methylammonium, ethylammonium, dimethylammonium, diethylammonium, trimethylammonium (ΝΜβ3Η+), triethylammonium, tributylammonium, diethylmethylammoniurrs, hydroxyethylammonium, meihoxymeihylammonium, dibuiylammonium, methylbutylammonium, anilinium, pyridinium, 2-methylpyridinium, imidazoiium, 1-methylimidazolium, 1 ,2- dimethylimidazolium, imidazolinium, 1-ethylimidazolium, 1-(4-sulfobutyl)-3-methylimidazolium, 1-allylimidazolium, quinolinium, isoquinoiinium, pyrroiinium, pyrrolininium or pyrrolidinium;
1-butyl-1-methylpyrrolidinium, tetramethylammonium, tetraethyiammonium, tetra-n- butylammonium, n-butyl-tri-ethylammonium, benzyl-tri-methylammonium, tri-n- butylmethylammonium, benzyl-tri-ethylammonium, 1-methylpyridinium, 1-butyl-3,5- dimethylpyridinium, 1 ,2,4-trimethylpyrazolium, trimethylhydroxyethylarnmonium (choline), tri- (hydroxyethyl)methylammonium, dimethyl-di(polyoxyethylene)arnmonium, 1 ,2,3- trimethylimidazolium, 1-butyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-allyl-3- methyiimidazolium, 1-hydroxyethyl-3-methyiimidazolium, 1 ,3-dimethylimidazolium, 1 -ethyl- 1- methylpiperidinium, 4-ethyl-4-methylmorpholinium, 1-(cyanomethyl)-3-methylimidazolium, 1-(3- cyanopropyl)pyridinium, 1 ,3-bis(cyanomethyl)imidazolium, l-hexyl-3-methyiimidazoiium or 1- ethyl-3-methylimidazolium; and
methyltriphenylphosphonium, tetraphenylphosphonium, tetrabutylphosphonium,
tributylmethylphosphonium, triethylmethylphosphonium, trihexyltetradecylphosphonium, triphenylpropylphosphonium or tetrakis(hydroxymethyl)phosphonium;
for instance, the cation is 1-ethyl-3-methylimidazoiium, 1-hexyl-3-methylimidazolium, 1-butyl-1- methylpyrrolidinium or trihexyl(tetradecyl)phosphonium.
E19. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of carboxylates, imides, methides, nitrate, bifluoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aluminates.
E20. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of
[FzB(CmF2m+l)4-z]-, iFyP(CmF2m÷l)6-y]-, [(CmF2nHl)2P(0)0]-| [CmF2nH 1 P(0)02] 2", [0-C(0)-CmF2nl+l]-,
[0-S(0)2-CmF2nHi]-, [N(C(0)-CmF2m+i)2]-, [N(S(0)2-CmF2mt1)2]-, [N(C(0)-CmF2m+1)(S(0)2-CmF2m+i)]-, [N(C(0)-CmF2m+i)(C(0)F)]-, [N(S(0)2-CmF2n,+i)(S(0)2F)]-, [N(S(0)2F)2]-, [C(C(0)-CmF2m+i)3]-, ;c(S(0)2-crpF2!,1+i)3]
Figure imgf000055_0001
where
y is an integer of 1 to 6,
m is an integer of 1 to 8, for instance 1 to 4,
z is an integer of 1 to 4,
X is B or Al and
Rw, Rx, Ry and Rzare independently halogen, CrC2oaikyi, CrC2oalkyi which is partly or fully fluorinated, CrC2oalkoxy, CrC20alkoxy which is partly or fully fluorinated, Ci~C20alkyl~COO or CrC2oalkyl-COO which is partly or fully fluorinated and
0 ""0 is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxylic acid or from a 1 ,2- or 1 ,3-hydroxycarboxylic acid and
where any one CF2 group may be replaced by O, S(0)2, NR or CH2.
E21. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of F2P(C2Fs)4-,
Figure imgf000055_0002
F3P(C4F9)3 ", F4P(C4F9)2 ", perfluoroalkylcarboxylate, perfiuoroalkylsulfonate,
bis(perfluoroalkylsulfonyl)imide, (perfluoroalkylsulfonyl)(perfluoroalkylcarboxyl)imide, tris(perfluoroalkylsulfonyl)methide, frifluoroacetate, frifluoromethanesulfonate (trifiate), bis(trifluoromethylsulfonyl)imide, tris(trifluoromethylsulfonyl)methide, ietrafluoroborate or a spiro- oxo borate or spiro-oxo phosphate, for example bisoxalatoborate (BOB), difluorooxaiatoborate (dFOB), di(trifluoroacetato)oxalatoborate (d(Ac)OB), trisoxalatophosphate,
tetrafluorooxaiatophosphate and d!(trifluoroacetato)oxalatoaluminate.
E22. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing a carboxylate anion of formula RCOO" where R is hydrogen or hydrocarbyl; such as formate, acetate (ethanoate), acrylate, propanoate, n- butanoate, i~butanoate, n~pentanoate, i~pentanoate, octanoate, decanoate, benzoate, salicylate, thiosalicylate, 2-, 3- or 4-nitrobenzoate; citrate, oxalate, tartrate, giycolate, gluconate, ma!ate, mandelate, a carboxylate of nitrilotriacetic acid, a carboxylate of N-(2-hydroxyethyl)- ethylenediaminetriacetic acid, a carboxylate of ethylenediaminetetraacetic acid, a carboxylate of diethylenetriaminepentaacefic acid or a haloalkylcarboxylate such as fluoroacetate,
difiuoroacetate, trifiuoroacetate, chloroacetate, dichloroacetate or trichioroacetate.
E23. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing
an imide anion such as dicyanamide, N(SQ2F)2 "" ((bisfluorosulfonyl)irnide), a
bis(perfiuoroaikylsulfonyi)imide such as [N(S02CF3)2]- (bistriflimide),
bis(pentafluoroethylsulfonyl)imide or N(CF3S02)(CF3(CF2)3S02r or a
(perfluoroalkyisulfonyi)(perfiuoroaikylcarboxyi)imide; or
a methide such as a tris(perfluoroalkylsulfonyl)methide, for example
tris(trifluoromethylsulfonyl)methide, C(CF3S02)3~; or
bifluoride (HF2 _); or
chloride, bromide, iodide or fluoride; or
a borate such as orthoborate, tetrahydroxyborafe, tetraborate, tetraphenylborate, [B(3,5- (CF3)2CeH3)4]- (BARF), B(C204)2- (bis(oxalato)borate) (BOB), difluoro(oxalato)borate (dFOB), di(trifluoroacetato)oxalatoborate (D(Ac)OB), B(C6FS)4~ or BF4 ~ (fetrafluoroborate); or
a phosphate such as dihydrogen phosphate, hydrogen phosphate, alkyi phosphate, dialkyi phosphate, phosphate, PF6 " (hexafiuorophosphate), HP03F~ (fiuorohydrogen phosphate), trisoxalatophosphate (TOP), tetrafluorooxalatophosphate (TFOP) or a
fiuoro(perfluoroalkyi)phosphate such as F2P(C2FS)4", F3P(C2Fs)3 "
(tris(pentafiuoroethyl)trifluorophosphate or FAP), F4P(C2F5)2 ~, F2P(C3F7)4~, F3P(C3F7)3 ~
F4P(C3F7)2- F2P(C4Fg)4- F3P(C4Fe)3- or F4P(C4F9)2-; or
a sulfonate such as an alkylsulfonate, arylsulfonate or perfluoroalkylsulfonate, for instance trifiuoromethanesuifonate (triflate), p-toiuenesuifonate (tosylate) or mefhanesulfonafe
(mesylate); or
a sulfate such as hydrogensulfate, sulfate, thiosuifate or an alkyisulfate such as mefhylsuifate or ethyl sulfate; or
a carbonate anion such as carbonate, hydrogencarbonate or an alkylcarbonate such as methylcarbonate, ethyicarbonate or butylcarbonate; or
an aluminate such as AI(OC(CF3)3)4 ~ di(trifluoroacetato)oxalatoaluminate (d(Ac)OAI), tetrach!oroaluminate, tetraf!uoroa!uminate, tetraiodoaluminate or tetrabromoaluminate. E24. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid.
E25. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of diethylmethylammonium trifiuoromethanesuifonate (DE A TfO), ethylammonium nitrate, triethylammonium
methanesulfonate, 2-methylpyridinium trifiuoromethanesuifonate, ammonium fluoride, methylammonium nitrate, hydroxyethylammonium nitrate, ethylammonium nitrate,
dimethylammonium nitrate, 1-meihylimidazoiium nitrate, 1-ethylimidazolium nitrate, i- butylammonium tetrafiuoroborate, hydroxyethylammonium tetrafluoroborate,
methylbutyiammonium tetrafluoroborate, triethylammonium tetrafluoroborate, imidazolium tetrafluoroborate, 1-methylimidazoiium tetrafluoroborate, 1 ,2-dimethylimidazolium
tetrafluoroborate, t-butylammonium inflate, 2-fluoropyridinium trifiate, hydroxyethylammonium trifiate, 1 ,2-dimethylimidazolium trifiate, imidazolium trifiate, 1-methylimidazolium
hydrogensulfate, 1-methylimidazolium chloride, 1-methylimidazolium trifiate, hydronium trifiate, methylammonium mesylate, ethylammonium mesylate, buty!ammonium mesylate,
meihoxyeihyiammonium mesylate, dimethylammonium mesylate, dibutyiammonium mesylate, triethylammonium mesylate, dimethylethyiammonium mesylate, hydronium hydrogensulfate, ammonium hydrogensulfate, methylammonium hydrogensulfate, ethylammonium
hydrogensulfate, propylammonium hydrogensulfate, n-butylammonium hydrogensulfate, t- butylammonium hydrogensulfate, dimethylammonium hydrogensulfate, diethyiammonium hydrogensulfate, di-n-buiylammonium hydrogensulfaie, methylbutyiammonium hydrogensulfate, ethylbutylammonium hydrogensulfate, trimethylammonium hydrogensulfate, triethylammonium hydrogensulfate, tributylammonium hydrogensulfate, dimethylethyiammonium hydrogensulfate, dibutyiammonium fiuorohydrogen phosphate, triethylammonium fiuorohydrogen phosphate, tributylammonium fiuorohydrogen phosphate, hydronium dihydrogen phosphate,
methylammonium dihydrogen phosphate, ethylammonium dihydrogen phosphate,
propylammonium dihydrogen phosphate, n-butylammonum dihydrogen phosphate,
meihoxyeihyiammonium dihydrogen phosphate, dimethylammonium dihydrogen phosphate, dibutyiammonium dihydrogen phosphate, methylbutyiammonium dihydrogen phosphate, ammonium bifluoride, methylammonium bifiuoride, ethylammonium bifluoride and
dimethylammonium bifluoride.
E26. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of 1-ethyl-3-methylimidazolium trifiuoromethanesuifonate (EMIM TfO), 1-ethyi-3-methylimidazolium tetrafluoroborate (EMIM BF4), 1-ethyl-3-methylimidazolium bis(trifiuoromethylsulfonyl)imide (EMIM TFSI), 1-ethyi-3- methylimidazolium acetate (EMI Ac), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIM TfO), 1-butyl~3-methylimidazolium acetate (BMIM Ac), 1-butyl~3~methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), tri-n-butylmethylammonium methylsulfate, 1- ethyl-2,3-dimethylimidazolium ethylsuifate, 1-butyl-3-methylimidazolium thiocyanate, 1-butyl-3- methylimidazolium tetrachloroaluminate, 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3- methylimidazolium meihanesulfonaie, 1-butyl-3-methylimidazolium hydrogencarbonate, 1-butyl- 3-meihylimidazoiium hydrogensulfate, 1-butyl-3-methylimidazolium chloride, 1 ,2,3- trimethylimidazolium methylsulfate, tris-(hydroxyethyl)methylammonium methylsulfate, 1 ,2,4- trimethylpyrazolium methylsulfate, 1 ,3-dimethylimdiazolium hydrogencarbonate, 1 -ethyl-3- methylimidazolium hydrogencarbonate, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3- methylimidazolium tetrachloroaluminate, l-eihyl-S-methylimidazoiium thiocyanate, 1-ethyl-3- methylimidazoiium meihanesulfonaie, 1-ethyl-3-methylimidazolium hydrogensulfate, 1 -ethyl-3- methyiimidazoiium ethylsuifate, 1-ethyi-3-methylimidazolium nitrate, 1-butyipyridinium chloride, 1-ethyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methyiimidazolium hexafluorophosphaie, 1- buiyl-3,5-dimethylpyridinium bromide, 1-ethyi-3-meihylimidazolium
bis(pentafluoroethylsulfonyl)imide, 1-ethyl-2,3-dimeihylimidazoiium meihyicarbonate, carboxymethyl-tributylphosphonium bis(trifluoromethylsulfonyl)imide, N-carboxyeihyl- methyipyrroiidinium bis(trifluoromethylsulfonyl)imide, N-carboxymethyl-trimethylammonium bis(trifluoromethylsulfonyl)imide, N-carboxymethyl-methylpyridinium
bis(trifluoromethylsulfonyl)imide, hexyltrimethylammonium bis(trifluromethylsulfonyl)imide, teirabutylphosphonium meihanesulfonaie, triethylmeihylammonium meihyicarbonate, 1-ethyl-1- methylpiperidinium meihyicarbonate, 4-ethyl-4-meihylmorpho!inium meihyicarbonate, 1-butyl-1- methylpyrrolidinium meihyicarbonate, triethylmeihylammonium dibutylphosphate,
tributylmethylphosphonium dibutylphosphate, triethylmethylphosphonium dibutylphosphate, teirabutylphosphonium ieirafiuoroboraie, teirabutylphosphonium p-toluenesulfonate, tributylmethylphosphonium meihyicarbonate, 1-ethyi-3-meihylimidazolium hydrogencarbonate, tributylmethylammonium meihyicarbonate, tributylmethylammonium dibutylphosphate, 1 -ethyl-3- methyiimidazoiium dibutylphosphate, 1-butyl-3-methylimidazolium dibutylphosphate, 1- (cyanomeihyl)-3-meihylimidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-meihyiimidazoiium bis(trifluoromethylsulfonyl)imide, 1 -(3-cyanopropyi)-3- meihyiimidazoiium dicyanamide, 1-(3-cyanopropyl)pyridinium chloride, 1-(3- cyanopropyl)pyridinium bis(trifluoromethylsulfonyl)imide, 1 ,3-bis(cyanomethyl)imidazolium chloride, 1 ,3-bis(cyanomethyl)imidazolium bis(trifluoromethylsulfonyl)imide, 1 ,3- bis(cyanopropyl)imidazolium chloride, 1 ,3-bis(3-cyanopropyl)imidazoiium
bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphaie, 1 -butyl-3- methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3- methylimidazolium chloride, 1~ethyl-3-rnethyiimidazoiium bromide, 1-butyl-3-methylimidazolium bromide, 1-hexyl-3-methyiimidazolium chloride, tributyimethylphosphonium methyisulfate, triethylmethylphosphonium dibutyiphosphate, trihexyltetradecyiphosphonium
bis(triiiuromethylsulfonyl)imide, trihexyltetradecyiphosphonium bis(2,4,4- trimethylphenyl)phosphinate, trihexyltetradecyiphosphonium bromide,
trihexyltetradecyiphosphonium chloride, trihexyltetradecyiphosphonium decanoate,
trihexyltetradecyiphosphonium dicyanamide, 3-(triphenylphosphonio)propane-1 -sulfonate and 3- (triphenylphosphonio)propane-l-sulfonic acid tosyiate.
E27. A cell according to any of the preceding embodiments where the electrolyte composition comprises a protic acid; for example a protic acid such as
hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid or periodic acid; or
a bisulfate such as sodium bisulfate, potassium bisulfate or ammonium bisulfate; or
HAsFs, HBF4, H(OEt2)BF4, HPF6, ,H[N(S02CF3)2] or H[N(S02CF2CF3)2].
E28. A cell according to any of the preceding embodiments where the electrolyte composition comprises an organic protic acid such as a carboxylic acid of formula RCOOH where R is hydrogen or hydrocarbyi, for example formic acid, acetic acid, acrylic acid, fiuoroacefic acid, difluoroacetic acid, trifluoroacetic acid, chioroacetic acid, dichioroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methylbutanoic acid, valeric acid, hexanoic acid, hepfanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- or 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, giycolic acid, gluconic acid, malic acid, mandelic acid, nitriiotriacefic acid, N-(2~hydroxyethyl)~ethylenediaminetriacetic acid, ethylenediaminetetraacetic acid or diethyleneaminepentaacetic acid.
E29. A ceil according to any of the preceding embodiments where the electrolyte composition comprises a protic sulfonic acid of formula RSO3H where R is alkyi or aryi or aikyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsuifonic acid, methanesuifonic acid or trifiuoromethanesuifonic acid.
ESQ. A ceil according to any of the preceding embodiments where the electrolyte composition comprises a protic acid which is an oxonium ion associated with a highly non-coordinating ion such as Brookhart's acid (BARF acid), [H(OEt2)2][B[3,5-(CF3)2CeH3]4], [H(OEt2)2l[B(CsF5)4] (oxonium acid) or [H(OEt2)2][AI(OC(CF3)3)4].
E31. A ceil according to any of the preceding embodiments where the electrolyte composition comprises at least two different ionic compounds; for example, where the electrolyte
composition comprises a protic ionic compound and an aprotic ionic compound;
two different protic ionic compounds;
two different aprotic ionic compounds;
two different salts;
two different ionic liquids;
a salt and an ionic liquid, for example a protic or aprotic ammonium salt or an alkali metal salt such as an aikai metal halide;
a protic acid, protic ammonium compound or a protic oxonium compound and an ionic liquid, for example a carboxyiic acid and an ionic liquid.
E32. A cell according to any of the preceding embodiments where the electrolyte composition comprises two different ionic compounds which contain an identical cation or an identical anion, E33. A ceil according to any of the preceding embodiments where electrolyte composition comprises two different ionic compounds with a weight:weight ratio of from about 99.9:0.1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
E34. A ceil according to any of the preceding embodiments where the electrolyte composition contains no organic solvent and < 1000 ppm, < 100 ppm or < 10 ppm water by weight, based on the total weight of the electrolyte composition; or where the electrolyte composition contains < 9, < 8, < 7, < 6, < 5 or < 4 ppm water by weight, based on the total weight of the electrolyte composition.
ESS. A ceil according to any of embodiments 1-33 where the electrolyte composition comprises a solvent,
E36. A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of water.
E37. A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of organic solvent.
ESS. A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent comprising water and an organic solvent.
E39. A ceil according to embodiment 38 where the weight:weight ratio of water to organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about E40. A cell according to any of embodiments 37-39 where the organic solvent comprises one or more solvents selected from the group consisting of organic carbonates, ethers, giymes, ortho esters, polyalklene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents and nitrile solvents.
E41. A cell according to embodiment 40 where the electrolyte composition comprises an organic solvent such as
an organic carbonate, for example a cyclic or acyclic organic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), trimetbylene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyimethyi carbonate (EMC), vinylene carbonate, difluoroethylene carbonate or monofluoroethylene carbonate; or
an ether or giyme such as dimethoxymethane (DMM), diethoxymethane, 1 ,2-dimethoxyefhane (DME or ethyleneglycol dimethyiether or glyme), diglyme, trigiyme, tetragiyme, ethyleneglycol diethylether (DEE), ethyleneglycol dsbutylether, dsethyieneglycol diethylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1 ,3-dioxane, 1 ,3-dioxolane (DIOX), 4-methyl-1 ,3- dioxolane (4-MeDIOX), 2-methyl-1 ,3-dioxoiane (2-MeDIOX), 1 ,4-dioxane, dimethyiether, ethylmethylether, diethylether, di-n-butylether, di-t-butylether, di-isopropyiether, methyl-t- butylether, ethyl-t-butylether or t-amyl-methylether; or
an ortho ester such as trimethoxymethane, trsethoxymethane, 1 ,4-dimethyl-3,5,8- trioxabicyclo[2.2.2]octane or 4-ethyl-1-methyl-3,5,8-trioxabicyclo[2.2.2]octane; or
a polyalkyiene glycol, that is a homo- or cooligomer or homo- or copolymer of CrC4aikyiene glycols, such as polyethylene glycol (PEG) or monomethy!, dimethyl or diethyl (end-capped) polyethylene glycol with weight average molecular weights (Mw) for example from about 200 to about 1200 g/mol, from about 200 to about 1000 g/mol, from about 200 to about 900 g/mol, from about 200 to about 700 g/mol or from about 200 to about 500 g/mol, for example oligomers of 4 monomers or more, for instance tetraethylene glycol, fluorinated tetraethylene glycol or tetrapropylene glycol, for instance PEG 200, PEG 300, PEG 400, PEG 500, PEG 600, PEG 700, PEG 800, PEG 900 or PEG 1000; or
an ester or lactone such as γ-butyrolactone (GBL), γ-valerolactone, δ-valerolactone, ethyl acetate (EA), 2-methoxyethyl acetate, 2-ethoxyethyi acetate, 2-butoxyethyl acetate, 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EGDA), 3-ethoxy ethyl propionate (EEP), methyl bufyrate (MB), n-amy! acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate or dimethyl malonate; or
a dibasic ester mixture such as methyl esters of adipic, glutaric or succinic acids; or a glycol such as ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2- propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol (ethylene glycol butyl ether, EB), 2- phenoxyethanol, 2-benzyloxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol (diethylene glycol butyl ether, DB), propylene glycol butyl ether (PB), propylene glycol methyl ether (PM), triethylene glycol (TEG), dipropylene glycol methyl ether (DPM), diethylene glycol methyl ether, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, perfluoro-1 ,4-butanediol, perfluoro-1 ,5-butanediol, fluorinated diethylene glycol methyl ether, fluorinated triethylene glycol, fluorinated triethylene glycol methyl ether or fluorinated diethylene glycol butyl ether; or
a formate such as methyl formate, ethyl formate, isobutyl formate or tert-butyl formate; or a sulfone or sulfoxide such as methylsulfonylmethane ( SM or dimethy!su!fone),
ethylmethylsulfone, sulfolane or dimethylsulfoxide (D SO); or
an amide such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methyipyrroiidone (NMP), 2-pyrrolidone, 1 ,3-dimethyl-2-imidazolidinone (DMI), hexamethylphosphoramide (H PA) or N.N'-dimethyl-N.N'-trimethyleneurea (1 ,3~dimethyl-3,4,5,6 etrahydro-2(1 H)- pyrimidinone (DMPU)); or
an alcohol such as benzylalcohoi (BA), ethanol, trifluoroethanol (2,2,2-trifluoroethanol), methanol, isopropanol, t-butanol or n-butanol; or
a ketone such as methylethylketone (MEK) or methyl-isoamylketone (MIAK); or
a nitro solvent such as nitrobenzene, nitromethane or nitroethane; or
a nitrile solvent such as acetonitriie, propionitrile, butyronitrile or adiponitrile.
E42. A ceil according to any of embodiments 1-33 and 35-41 where the electrolyte composition comprises a solvent and where the weightweight ratio of ionic compounds in total to solvent is from about 99.9:0,1 to about 0, 1 :99.9, from about 99.5:0.5 to about 0,5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90: 10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
E43. A ceil according to any of embodiments 1-42 where the electrolyte composition further comprises one or more additives selected from the group consisting of corrosion inhibitors, solid electrolyte interface (SEI) improvers, proton evolution improvers, self-discharge inhibitors, anti- gassing agents, viscosity adjusting agents, cathode protection agents, salt stabilizers, conductivity improvers and solvating agents.
E44. A cell according to any of embodiments 1-43 where the electrolyte composition contains one or more additives selected from the group consisting of
fluorinated oil, sodium stannate, sodium citrate or poiyacryiic acids; HF or KF, oxides or hydroxides of rare earths such as Y, metal porphines, for example Ni or Fe porphine, vinylene carbonate, vinylethylene carbonate, methylene ethylene carbonate or fluoro- ethylene carbonate;
polyglycols, poiygiycoi alkyl ethers, polyglycol aiky! phosphate esters or polysorbates such as polyethylene glycol (PEG), polypropylene glycol, poiysorbate 20, polysorbate 40 or polysorbaie 80 or a mixture of PEG 600 and poiysorbate 20 or a mixture of PEG 600 and ZnO;
phosphate ester-based surfactants, propane sultone o fluoropropane sultone; and
D SO;
for example at a level of from about 0.1 % to about 15% by weight, based on the total weight of the electrolyte composition.
E45. A rechargeable electrochemical ceil according to any of the preceding embodiments comprising a positive electrode, a casing having the electrodes positioned therein and the electrolyte composition in contact with the electrodes, where the gravimetric energy density of the ceil is > l OO Wh/kg, > 1 10 Wh/kg, > 1 15, > 120, > 125, > 130, > 135, > 140, > 145, > 150, > 155, > 160, > 165, > 170, > 175, > 180, > 185, > 190, > 195 or > 200 Wh/kg and/or
where the volumetric energy density of the ceil is > 250 Wh/L, for instance, > 260 Wh/kg, > 265,
> 270, > 275, > 280, > 285, > 290, > 295, > 300, > 305, > 310, > 315, > 320, > 325, > 330, > 335,
> 340, > 345 or > 350 Wh/kg and/or
where the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 cycles or more (over at least 20 cycles), for example > 810, > 820, > 825, > 830, > 835, > 840, > 845, > 850, > 855, > 860, > 865, > 870, > 875, > 880 or > 895 mAh/g over 20 cycles or more.
E46. A ceil according to any of the preceding embodiments comprising a positive electrode, the positive electrode comprising one or more cathode active materials selected from the group consisting of transition metals, transition metal oxides, transition metal hydroxides, transition metal oxide/hydroxides and transition metal fluorides; for example one or more materials selected from the group consisting of
Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au;
oxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, ir, Pt or Au;
hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au;
oxide/hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, ir, Pt or Au; and fluorides Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au.
Below are more embodiments of the invention.
E1. A rechargeable electrochemical cell comprising a stable group IV element-based hydrogen storage negative electrode; for example a stable silicon-based or carbon-based hydrogen storage negative electrode; for example where the electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn, based on the total weight of the hydrogen storage material;
the cell also comprising a positive electrode, a casing having the electrodes positioned therein and an electrolyte composition in contact with the electrodes,
where the gravimetric energy density of the cell is > 100 Wh/kg, > 1 10 Wh/kg, > 115, > 120, > 125, > 130, > 135, > 140, > 145, > 150, > 155, > 160, > 165, > 170, > 175, > 180, > 185, > 190, > 195 or > 200 Wh/kg and/or
where the volumetric energy density of the ceil is > 250 Wh/L, for instance, > 260 Wh/kg, > 265,
> 270, > 275, > 280, > 285, > 290, > 295, > 300, > 305, > 310, > 315, > 320, > 325, > 330, > 335,
> 340, > 345 or > 350 Wh/kg and/or
where the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 cycles or more (over at least 20 cycles), for example > 810, > 820, > 825, > 830, > 835, > 840, > 845, > 850, > 855, > 860, > 865, > 870, > 875, > 880 or > 895 mAh/g over 20 cycles or more.
E2, A cell according to embodiment 1 where the negative electrode comprises a hydrogen storage material comprising > 27 wt% of one or more elements selected from the group consisting of C, Si, Ge and Sn; for example comprising > 27 wt% silicon or > 27 wt% carbon, based on the total weight of the hydrogen storage material.
E3. A ceil according to embodiments 1 or 2 where the hydrogen storage material comprises amorphous silicon, microcrystaliine silicon, nanocrystaliine silicon, monocrystailine silicon, polycrystalline silicon, protocrystaliine silicon or porous silicon.
E4. A ceil according to any of the preceding embodiments where the hydrogen storage material comprises amorphous silicon.
E5. A ceil according to any of the preceding embodiments where the hydrogen storage material comprises carbon; for example carbon in the form of natural graphite, artificial graphite, expanded graphite, graphene, carbon fiber, hard carbon, soft carbon, non-graphitizable carbon, carbon black, carbon nanotube, fullerene, activated carbon, crystalline carbon or amorphous carbon. E6. A cell according to any of the preceding embodiments where the hydrogen storage material comprises an alloy of silicon and one or more of carbon, germanium and tin, for example amorphous silicon carbide or an alloy of silicon and germanium or an alloy of silicon and tin. E7. A ceil according to any of the preceding embodiments where the hydrogen storage material is hydrogenated prior to assembly of the ceil (a pre-hydrogenated negative electrode); for example where the hydrogen storage material is hydrogenated amorphous silicon (a-Si:H) or hydrogenated amorphous silicon carbide (a-Sii-xCx:H, where x is for example from about 0.01 to about 0.99, from about 0.05 to about 0.95 or from about 0.1 to about 0.9).
E8. A ceil according to any of the preceding embodiments where the hydrogen storage material, for example amorphous silicon, is comprised in a film, for example a film with a thickness > 20 nm, > 50 nm, > 90 nm, > 120 nm or > 180 nm or from about 90 nm to about 10 μηι, from about 100 nm to about 5 μπη, from about 150 nm to about 3 μητι, from about 150 nm to about 2 μπΊ or from about 150 nm to about 1 μπη.
E9. A ceil according to any of the preceding embodiments where the hydrogen storage material is comprised in a film in adherence to a substrate, for example a substrate selected from metal, glass, inorganics and plastic.
E10. A ceil according to any of the preceding embodiments where the hydrogen storage material comprises one or more further elements, for example one or more elements selected from the group consisting B, Al, Ga, In, As, Sb, Te and transition metals.
E11. A ceil according to any of the preceding embodiments where the hydrogen storage material contains > 28 wt%, > 29 wt%, > 30 wt%, > 35 wt%, > 40 wt%, > 45 wt%, > 50 wt%, > 55 wt%, > 60 wt%, > 65 wt%, > 70 wt%, > 75 wt%, > 80 wt%, > 85 wt%, > 90 wt%, > 95 wt%, > 96 wt%, > 97 wt%, > 98 wt% or > 99 wt% of one or more elements selected from the group consisting of group IV elements, for example Si and/or C, based on the total weight of the hydrogen storage material.
E12. A ceil according to any of the preceding embodiments where the negative electrode comprises≥ 30% by weight of the one or more group IV elements; for example≥ 35%,≥ 40%, > 45%, > 50%, > 55%, > 60%, > 65%, > 70%, > 75% > 80%, > 85% or > 90% by weight of the one or more group IV elements, for example Si and/or C, based on the total weight of the negative electrode.
E13. A ceil according to any of the preceding embodiments where the negative electrode further comprises one or more components selected from the group consisting of binders, conductive materials and other additives.
E14. A cell according to any of the preceding embodiments where the negative electrode comprises a solid electrolyte interface capable of allowing transport of protons. E15. An cell according to any of the preceding embodiments where the hydrogen storage material includes one or more further elements selected from the group consisting of structural modifiers (elements to promote the amorphous phase of a material), hydrogen bond strength modifiers and solid electrolyte interface (SEI) modifiers; for example one or more further elements selected from the group consisting of B, alkaline earth metals, transition metals, rare earth metals, other metals of groups III or V of the periodic table, O, F, P, CI and the like,
E16. A ceil according to any of the preceding embodiments where the electrolyte composition is neutral or acidic, for example having a pH of about 7 or lower; for example from about 1 , from about 2, from about 3, from about 4, from about 5 or from about 6 to about 7.
E17. A cell according to any of the preceding embodiments where the electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, protic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotsc oxonium compounds, aprotic phosphonsum compounds and alkali or alkali earth metal salts.
E18. A ceil according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing a cation selected from the group consisting of NH4 + (ammonium), methylammonium, ethylammonium, dsmethylammonium, diethylammonium, trimethylammonium (N e3H+), triethylammonium, tributylammonium, diethylmethylammonium, hydroxyethylammonium, methoxymethylammonium, dibutyiammonium, methylbutylammonium, anilinium, pyridinium, 2-methyipyridinium, imidazoiium, 1-methyiimidazoiium, 1 ,2- dimethylimidazolium, imidazolinium, 1-ethylimidazolium, 1-(4-sulfobutyl)-3-methylimidazolium, 1-aliyiimidazoiium, quinolinium, isoquinolinium, pyrrolinsum, pyrrolsninium or pyrrolidinium;
1-butyl-1-methylpyrrolidinium, tetramethylammonium, tetraethylammonium, tetra-n- bufylammonium, n-butyl-tri-ethylammonium, benzyl-tri-rnethylammonium, tri-n- butylmethylammonium, benzyi-tri-ethylammonium, 1-methylpyridinium, 1-butyl-3,5- dimethylpyridinium, 1 ,2,4-trimethyipyrazoiium, trimethylhydroxyethyiammonsum (choline), tri- (hydroxyethyl)methylammonium, dimethyl-di(polyoxyethylene)ammonium, 1 ,2,3- trimethylimidazolium, 1-butyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-ailyl~3~ methylimidazolium, 1-hydroxyethyl-3-methylimidazolium, 1 ,3-dimethylimidazolium, 1 -ethyl- 1- methylpiperidinium, 4-ethyl-4-meihyimorpholinium, 1-(cyanomethyl)-3-methylimidazoiium, 1-(3- cyanopropyi)pyrsdinium, 1 ,3-bis(cyanomethyl)imidazolsum, 1-hexyl-3-methylimidazolium or 1- ethyl-3-methylimidazolium; and
methyitriphenyiphosphonium, tetraphenylphosphonium, tetrabutylphosphonium,
tributyimethylphosphonium, triethylmethylphosphonium, trihexyitetradecylphosphonium, triphenylpropylphosphonium or tetrakis(hydroxymethyi)phosphonium; for instance, the cation is 1~ethyl-3-methylimidazQlium, l-hexyl-3-methylimidazolium, 1-butyl-1- methylpyrrolidinium or trihexyl(fetradecyi)phosphonium,
E19. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of carboxylates, imides, methides, nitrate, bifluoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aluminates.
E20. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of
[FzB(CmF2m+i)4-J-, [FyP(CmF2m÷ i)6-y]-, [iCmF2m+i)2P(0)0]-, [CmF2m+i P(0)02l 2-, [0-C(0)-CmF2m+ i]-,
[0-S(0)2-Cn,F2nHl]-, [N(C(0)-CmF2m+l)2]-, [N(S(0)2-CmF2m+l)2]-, [N(C(0)-CmF2rp+i)(S(0)2-CmF2rrl+1)]",
[N(C(0)-Cn,F2m+i)(C(0)F)]-1 [N(S(0)2-CmF2m- )(S(0)2F)]-, [N(S(0)2F)2]-, [C(C(0)-Cfi!F2m+1)3]-,
[C(S(0)2-CmF2nHl)3]-,
Figure imgf000067_0001
where
y is an integer of 1 to 6,
m is an integer of 1 to 8, for instance 1 to 4,
z is an integer of 1 to 4,
X is B or Al and
Rw, Rx, Ry and Rzare independently halogen, CrC2oaikyi, CrC20alkyi which is partly or fully fluorinated, CrC20alkoxy, CrC20aikoxy which is partly or fully fluorinated, Ci-C2oaikyl-COG or CrC20alkyi-COO which is partly or fully fluorinated and
0 ""0 is independently a bidentate group derived from the -OH groups of a 1 ,2- or 1 ,3-diol, a 1 ,2- or 1 ,3-dicarboxyiic acid or from a 1 ,2- or 1 ,3~hydroxycarboxylic acid and
where any one CF2 group may be replaced by O, S(0)2, NR or CH2. E21. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of F2P(C2F5)4-, F3P(C2Fs)3-, F4P(C2Fs)2-I F2P(C3F7)4-, FsPiCsFyJs",
Figure imgf000068_0001
F3P(C4Fg)3", F4P(C4Fg)2", perfluoroalkyicarboxylate, perfluoroaikylsuifonate,
bis(perfiuoroaikylsulfonyi)imide, (perfluoroalkylsulfonyl)(perfluoroalkylcarboxyl)imide, tris(perfluoroalkylsulfonyl)methide, frifluoroacetate, trifluoromethanesulfonate (inflate), bis(trifluoromethyisulfonyi)imide, tris(trifluoromethylsulfonyl)methide, ietrafluoroborate or a spiro- oxo borate or spiro-oxo phosphate, for example bisoxalatoborate (BOB), difluorooxalatoborate (dFOB), di(frifiuoroacetato)oxalafoborate (d(Ac)OB), trisoxaiafophosphate,
ietrafluorooxalatophosphate and di(trifluoroacetato)oxalatoaluminate.
E22. A ceil according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing a carboxylate anion of formula RCOO where R is hydrogen or hydrocarbyi; such as formate, acetate (ethanoate), acrylate, propanoate, n- butanoate, i-butanoate, n-pentanoate, i-pentanoate, octanoate, decanoate, benzoate, salicylate, thiosalicylate, 2-, 3- or 4-nitrobenzoate; citrate, oxalate, tartrate, giycolate, gluconate, rna!aie, mandeiate, a carboxyiate of nitrilotriacetic acid, a carboxylate of N-(2-hydroxyethyi)- ethylenediaminefriacetic acid, a carboxylate of ethylenediaminetetraacetic acid, a carboxylate of diethylenetriaminepentaacetic acid or a haloalkyicarboxylate such as fluoroacetate,
difluoroacetate, trifluoroacetate, chloroacetate, dichloroacetate or trichloroacetate.
E23. A ceil according to any of the preceding embodiments where the electrolyte composition comprises an ionic compound containing
an imide anion such as dicyanamide, N(S02F)2~ ((bisfluorosulfonyl)imide), a
bis(perfluoroalkylsulfonyl)imide such as [N(S02CF3)2]'" (bistriflimide),
bis(pentafluoroethylsulfonyi)imide or (CF3S02)(CF3(CF2)3S02)~ or a
(perfluoroalkylsulfonyl)(perfluoroalkylcarboxyl)imide; or
a methide such as a tris(perfluoroalkyisuifonyl)methide, for example
tris(trifluoromethylsulfonyl)methide, C(CF3S02)3 ~; or
bifluoride (HF2 ~); or
chloride, bromide, iodide or fluoride; or
a borate such as orthoborafe, tetra hydroxy borate, tetraborate, tetraphenylborate, [B(3,5- (CF3)2CeH3)4]- (BARF), B(C204)2- (bis(oxaiafo)borate) (BOB), difiuoro(oxalato)borate (dFOB), di(trifluoroacetato)oxalatoborate (D(Ac)OB), B(C6F5)4" or BF4 "' (ietrafluoroborate); or
a phosphate such as dihydrogen phosphate, hydrogen phosphate, alkyl phosphate, dialkyl phosphate, phosphate, PF6 " (hexafiuorophosphate), HP03F" (fluorohydrogen phosphate), trisoxalaiophosphaie (TOP), ietrafluorooxalatophosphate (TFOP) or a fluoro(perfluoroalkyl)phosphate such as F2P(C2F5)4'"', F3P(C2F5)3 ""
(tris(pentafluoroethyl)irifluorophosphaie or FAP), F4P(C2F5)2 ~ F2P(C3F7)4~ F3P(C3F7)3~
F4P(C3F7)2" F2P(C4Fg)4~ F3P(C4F9)3- or F4P(C4F9)2-; or
a sulfonate such as an alkylsulfonate, arylsulfonate or perfluoroalkylsulfonate, for instance trifluoromethanesulfonate (triflate), p-toiuenesuifonate (tosylate) or methanesulfonate
(mesylate); or
a sulfate such as hydrogensulfate, sulfate, thiosulfate or an alkylsulfate such as methyisulfate or ethylsulfate; or
a carbonate anion such as carbonate, hydrogencarbonate or an alkylcarbonate such as methylcarbonate, ethylcarbonate or butylcarbonate; or
an aluminate such as AI(OC(CF3)3)4 ~ di(trifluoroacetato)oxalatoaluminate (d(Ac)OAI), tetrachloroaluminate, tetrafluoroaluminate, tetraiodoaluminate or tetrabromoaluminate.
E24. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid,
E25. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of diethylmethyiammonium trifluoromethanesulfonate (DE A TfO), ethy!ammonium nitrate, triethylammonium
methanesulfonate, 2-methylpyridinium trifluoromethanesulfonate, ammonium fluoride, methyiammonium nitrate, hydroxyethyia rnonium nitrate, ethylammonium nitrate,
dimethylammonium nitrate, 1-methyiimidazoiium nitrate, 1-ethylimidazolium nitrate, t- butylammonium tetrafluoroborate, hydroxyethyiammonium tetrafiuoroborate,
methylbutylammonium tetrafluoroborate, triethylammonium tetrafiuoroborate, imidazoiium tetrafluoroborate, 1-methylimidazoiium tetrafluoroborate, 1 ,2-dimethylimidazolium
tetrafiuoroborate, t~butylammonium triflate, 2-fiuoropyridinium triflate, hydroxyethyiammonium triflate, 1 ,2-dimethylimidazoiium triflate, imidazoiium triflate, 1-methylimidazolium
hydrogensulfate, 1-methyiimidazolium chloride, 1-methylimidazolium inflate, hydronium triflate, methyiammonium mesylate, ethylammonium mesylate, butylammonium mesylate,
methoxyethylammonium mesylate, dimethylammonium mesylate, dibutylammonium mesylate, triethylammonium mesylate, dimethylethyiammonium mesylate, hydronium hydrogensulfate, ammonium hydrogensulfate, methyiammonium hydrogensulfate, ethylammonium
hydrogensulfate, propyiammonium hydrogensulfate, n-buty!ammonium hydrogensulfate, t- butylammonium hydrogensulfate, dimethylammonium hydrogensulfate, diethyiammonium hydrogensulfate, di-n-butylammonium hydrogensulfate, methylbutylammonium hydrogensulfate, efhylbutyiammonium hydrogensulfate, trimethyiammonium hydrogensulfate, triethylammonium hydrogensulfate, tributylammonium hydrogensulfate, dimethylethyiammonium hydrogensulfate, dibutylammonium fluorohydrogen phosphate, triethylammonium f!uorohydrogen phosphate, tributylammonium fluorohydrogen phosphate, hydronium dihydrogen phosphate,
methylammonium dihydrogen phosphate, ethylammonium dihydrogen phosphate,
propyiammonium dihydrogen phosphate, n-butylammonum dihydrogen phosphate,
methoxyethylammonium dihydrogen phosphate, dimethylammonium dihydrogen phosphate, dibutylammonium dihydrogen phosphate, methyibutylammonium dihydrogen phosphate, ammonium bifluoride, methylammonium bifluoride, ethylammonium bifluoride and
dimethylammonium bifluoride.
E28. A cell according to any of the preceding embodiments where the electrolyte composition comprises an ionic liquid selected from the group consisting of 1-ethyl-3-methylimidazolium trifiuoromethanesuifonate (E IM TfO), 1-ethyi-3-methylimidazolium tetrafluoroborate (EMIM BF4), 1-ethyl-3-methylimidazolium bis(trifluoromethyisulfonyi)imide (EMIM TFSI), 1 -ethyl-3- methyiimidazolium acetate (EMIM Ac), 1-butyi-3-methylimidazolium trifiuoromethanesuifonate (BMIM TfO), 1-butyl-3-methylimidazolium acetate (BMIM Ac), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM TFSI), tri-n-butylmethylarnmonium methyisuifate, 1- ethyl-2,3-dimethylimidazoiium ethylsuifate, 1-butyl-3-methylimidazolium thiocyanate, 1-butyl-3- methyiimidazoiium tetrachloroaluminate, 1-butyl-3-methylimidazolium methyisuifate, 1-butyl-3- methyiimidazoiium mefhanesulfonafe, 1-buty!-3-meihylimsdazolium hydrogencarbonate, 1-butyl- 3-methylimidazolium hydrogensulfate, 1-butyl-3-methylimidazolium chloride, 1 ,2,3- trimethylimidazolium methyisuifate, tris-(hydroxyethyi)methylammonium methyisuifate, 1 ,2,4- trimethylpyrazolium methyisuifate, 1 ,3-dimethylimdiazolium hydrogencarbonate, 1 -ethy!-3- methyiimidazoiium hydrogencarbonate, 1-efhyl-3-methyiimidazoiium chloride, 1-ethyl-3- methylimidazolium tetrachloroaluminate, 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3- methyiimidazoiium mefhanesulfonafe, 1-ethyl-3-methylimidazolium hydrogensulfate, 1 -ethyl-3- methylimidazoiium ethylsuifate, 1-eihyl-3-methylimidazolium nitrate, 1-butyipyridinium chloride, 1-ethyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1- butyl-3,5-dimethylpyridinium bromide, 1-ethyl-3-methylimidazolium
bis(pentafluoroethylsulfonyl)imide, 1-ethyl-2,3-dimethylimidazolium meihylcarbonate, carboxymethyl-tributylphosphonium bis(trifluoromethylsuifonyl)imide, N-carboxyethyl- methyipyrroiidinium bis(trifluoromethylsulfonyi)imide, N-carboxymethyl-trimethylammonium bis(trifiuoromethyisulfonyi)imide, N-carboxymethyl-methylpyridinium
bis(trifluoromethylsulfonyl)imide, hexyltrimethylammonium bis(trifluromethyisulfonyl)imide, tetrabutylphosphonium methanesuifonate, triethylmethylammonium meihylcarbonate, 1-ethyl-1- methyipiperidinium meihylcarbonate, 4-ethyl-4-methylmorpholinium meihylcarbonate, 1-butyl-1- methylpyrrolidinium meihylcarbonate, triethylmethylammonium dibuiylphosphaie, tributylmethylphosphonium dibutylphosphate, triethylmethylphosphonium dibutylphosphate, tetrabutyiphosphonium teirafluoroborate, teirabuiylphosphonium p-toluenesulfonate, tributylmethylphosphonium methylcarbonate, 1-ethyl-3-methylimidazolsum hydrogencarbonate, tributylmethylammonium methylcarbonate, tributylmethylammonium dibutylphosphate, 1 -ethyl-3- methylimidazolium dibutylphosphate, 1-butyl-3-methylimidazolium dibutylphosphate, 1- (cyanomethyl)-3-methylimidazolium chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1 -(3-cyanopropyi)-3- methylimidazolium dicyanamide, 1-(3-cyanopropyl)pyridinium chloride, 1-(3- cyanopropyl)pyridinium bis(trifiuoromethyisuifonyl)imide, 1 ,3-bis(cyanomethyl)imidazolium chloride, 1 ,3-bis(cyanomethyl)imidazolium bis(trifluoromethylsulfonyl)imide, 1 ,3- bis(cyanopropyl)imidazolium chloride, 1 ,3-bis(3-cyanopropyl)imidazolium
bis(trifluoromethyisulfonyi)imide, 1-butyl-3-methylimidazolium hexafiuorophosphate, 1 -butyl-3- methyiimidazoiium tetrafiuoroborate, 1-ethyl-3-methyiimidazoiium tetrafiuoroborate, 1-ethyl-3- methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-hexyl~3~methyiimidazoiium chloride, tributylmethylphosphonium methyisulfate, triethylmethylphosphonium dibutylphosphate, trihexyltetradecylphosphonium
bis(trifiuromethyisuifonyl)imide, trihexyltetradecylphosphonium bis(2,4,4- trimethyiphenyi)phosphinate, trihexyltetradecylphosphonium bromide,
trihexyltetradecylphosphonium chloride, trihexyltetradecylphosphonium decanoate,
trihexyltetradecylphosphonium dicyanamide, 3-(triphenylphosphonio)propane-1 -sulfonate and 3- (triphenylphosphonio)propane-l-sulfonic acid tosyiate.
E27. A ceil according to any of the preceding embodiments where the electrolyte composition comprises a protic acid; for example a protic acid such as
hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid or periodic acid; or
a bisulfate such as sodium bisulfate, potassium bisulfate or ammonium bisuifate; or
HAsFs, HBF4, H(OEt2)BF4, HPF6, ,H[N(S02CF3)2] or H[N(S02CF2CF3)2].
E28. A cell according to any of the preceding embodiments where the electrolyte composition comprises an organic protic acid such as a carboxylic acid of formula RCOOH where R is hydrogen or hydrocarbyi, for example formic acid, acetic acid, acrylic acid, fiuoroacetic acid, difluoroacetic acid, trifluoroacetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methylbutanoic acid, valeric acid, hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- or 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, giycolic acid, gluconic acid, malic acid, mandelic acid, nitriiotriacetic acid, N-(2-hydroxyethyl)-ethylenediaminetriacetic acid, ethylenediarninetetraacetic acid or diethylenearninepentaacetic acid.
E29. A cell according to any of the preceding embodiments where the electrolyte composition comprises a protic sulfonic acid of formula RSO3H where R is alky! or aryl or alkyl or aryl substituted by one to three halogens, such as p-toluenesulfonic acid, phenylsuifonic acid, methanesulfonic acid or trifluoromethanesulfonic acid.
E30. A cell according to any of the preceding embodiments where the electrolyte composition comprises a proiic acid which is an oxonium ion associated with a highly non-coordinating ion such as Brookhart's acid (BARF acid), [HiOEkMBp.S-iCFakCeHaM, [H(OEt2)2][B(CsF5)4] (oxonium acid) or [H(OEt2)2][Ai(OC(CF3)3)4].
E31. A cell according to any of the preceding embodiments where the electrolyte composition comprises at least two different ionic compounds; for example, where the electrolyte
composition comprises
a protic ionic compound and an aprotic ionic compound;
two different protic ionic compounds;
two different aprotic ionic compounds;
two different salts;
two different ionic liquids;
a salt and an ionic liquid, for example a protic or aprotic ammonium salt or an alkali metal salt such as an aikai metal halide;
a protic acid, protic ammonium compound or a protic oxonium compound and an ionic liquid, for example a carboxyiic acid and an ionic liquid.
E32. A ceil according to any of the preceding embodiments where the electrolyte composition comprises two different ionic compounds which contain an identical cation or an identical anion. E33. A ceil according to any of the preceding embodiments where electrolyte composition comprises two different ionic compounds with a weighfcweight ratio of from about 99.9:0.1 to about 0,1 :99.9, from about 99.5:0.5 to about 0.5:99.5, from about 99: 1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
E34. A ceil according to any of the preceding embodiments where the electrolyte composition contains no organic solvent and < 1000 ppm, < 100 ppm or < 10 ppm water by weight, based on the total weight of the electrolyte composition; or where the electrolyte composition contains < 9, < 8, < 7, < 6, < 5 or < 4 ppm water by weight, based on the total weight of the electrolyte composition. E35. A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent,
E36. A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of water.
E37. A cell according to any of embodiments 1-33 where the electrolyte composition comprises a solvent consisting essentially of organic solvent.
ESS. A ceil according to any of embodiments 1-33 where the electrolyte composition comprises a solvent comprising water and an organic solvent.
E39. A ceil according to embodiment 38 where the weight:weight ratio of water to organic solvent is from about 99.9:0.1 to about 0.1 :99.9, from about 99,5:0.5 to about 0.5:99.5, from about 99:1 to about 1 :99, from about 95:5 to about 5:95, from about 90:10 to about 10:90, from about 80:20 to about 20:80, from about 70:30 to about 30:70 or from about 60:40 to about 40:60.
E40. A ceil according to any of embodiments 37-39 where the organic solvent comprises one or more solvents selected from the group consisting of organic carbonates, ethers, giymes, ortho esters, polyalklene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents and nitrile solvents.
E41. A ceil according to embodiment 40 where the electrolyte composition comprises an organic solvent such as
an organic carbonate, for example a cyclic or acyclic organic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), trimethylene carbonate, 1 ,2-butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyimethyi carbonate (EMC), vinylene carbonate, difluoroethylene carbonate or monofluoroethylene carbonate; or
an ether or giyme such as dimethoxymethane (DMM), diethoxymethane, 1 ,2-dimethoxyefhane (DME or ethylenegiycol dimethyiether or glyme), diglyme, trigiyme, tetragiyme, ethylenegiycol diethylether (DEE), ethylenegiycol dsbutylether, dsethyleneglycol diethylether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1 ,3-dioxane, 1 ,3-dioxolane (DIOX), 4-methyl-1 ,3- dioxolane (4-MeDIOX), 2-rnethy!-1 ,3-dioxo!ane (2-MeDIOX), 1 ,4-dioxane, dimethyiether, ethylmethylether, diethylether, di-n-butylether, di-t-butylether, di-isopropyiether, methyl-t- butylether, ethyl-t-butylether or t-amyl-methylether; or
an ortho ester such as trimethoxymethane, triethoxymethane, 1 ,4-dimethyl-3,5,8- trioxabicyclo[2.2.2]octane or 4-ethyl-1-methyl-3,5,8-trioxabicyclo[2.2.2]octane; or
a polyalkyiene glycol, that is a homo- or cooligomer or homo- or copolymer of CrC4aikyiene glycols, such as polyethylene glycol (PEG) or monomethyl, dimethyl or diethyl (end-capped) polyethylene glycol with weight average molecular weights (Mw) for example from about 200 to about 1200 g/mol, from about 200 to about 1000 g/mol, from about 200 to about 900 g/mol, from about 200 to about 700 g/mol or from about 200 to about 500 g/mol, for example oligomers of 4 monomers or more, for instance tetraethyiene glycol, fluorinated tetraethylene glycol or tetrapropyiene glycol, for instance PEG 200, PEG 300, PEG 400, PEG 500, PEG 600, PEG 700, PEG 800, PEG 900 or PEG 1000; or
an ester or lactone such as γ-butyrolactone (GBL), γ-valerolactone, δ-valerolactone, ethyl acetate (EA), 2-methoxyethyl acetate, 2-ethoxyetbyl acetate, 2-butoxyetbyl acetate, 2-(2- butoxyethoxy)ethyl acetate (diethylene glycol butyl ether acetate, DBA), ethylene glycol diacetate (EGDA), 3-ethoxy ethyl propionate (EEP), methyl butyrate (MB), n-amyl acetate (NAAC), propylene glycol methyl ether acetate (PMA), ethyl butryate (EB), diethyl malonate or dimethyl malonate; or
a dibasic ester mixture such as methyl esters of adipic, giutaric or succinic acids; or
a glycol such as ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol, 2- propoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol (ethylene glycol butyl ether, EB), 2- phenoxyethanoi, 2-benzyloxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(2-butoxyethoxy)ethanol (diethylene glycol butyl ether, DB), propylene glycol butyl ether (PB), propylene glycol methyl ether (PM), Methylene glycol (TEG), dipropylene glycol methyl ether (DPM), diethylene glycol methyl ether, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, perfluoro-1 ,4-butanediol, perfluoro-1 ,5-butanediol, fluorinated diethylene glycol methyl ether, fluorinated triethylene glycol, fluorinated triethylene glycol methyl ether or fluorinated diethylene glycol butyl ether; or
a formate such as methyl formate, ethyl formate, isobutyl formate or tert-butyl formate; or a sulfone or sulfoxide such as methylsulfonylmethane ( SM or dimethylsuifone),
ethylmethylsulfone, sulfolane or dimethylsulfoxide (D SO); or
an amide such as dimethylformamide (DMF), dimethylacetamide (DMA), N-methyipyrroiidone (NMP), 2-pyrrolidone, 1 ,3-dimethyl-2-imidazolidinone (DMI), hexameihy!phosphoramide (H PA) or N.N'-dimethyl-N.N'-trimethyleneurea (1 ,3-dimethyl-3,4,5,6 etrahydro-2(1 H)- pyrimidinone (DMPU)); or
an alcohol such as benzylalcohoi (BA), ethanol, trifluoroethanol (2,2,2-trifluoroethanol), methanol, isopropanol, t-butanol or n-butanol; or
a ketone such as methylethylketone (MEK) or methyi-isoamylketone ( IAK); or
a nitro solvent such as nitrobenzene, nitromethane or nitroethane; or
a nitrile solvent such as acetonitriie, propionitrile, butyronitrile or adiponitrile.
E42. A ceil according to any of embodiments 1-33 and 35-41 where the electrolyte composition comprises a solvent and where the weightweight ratio of ionic compounds in total to solvent is ffrroomm aabboouutt 9999..99::00,, 11 ttoo aabboouutt 00,, 11 ::9999..99,, ffrroomm aabboouutt 9999..55::00,,55 ttoo aabboouutt 00,,55::9999..55,, ffrroomm aabboouutt 9999::11 ttoo aabboouutt 11 ::9999,, ffrroomm aabboouutt 9955::55 ttoo aabboouutt 55::9955,, ffrroomm aabboouutt 9900::1100 ttoo aabboouutt 1100::9900,, ffrroomm aabboouutt 8800::2200 ttoo aabboouutt 2200::8800,, ffrroomm aabboouutt 7700::3300 ttoo aabboouutt 3300::7700 oorr ffrroomm aabboouutt 6600::4400 ttoo aabboouutt 4400::6600..
EE4433.. AA cceellll aaccccoorrddiinngg ttoo aannyy ooff eemmbbooddiimmeennttss 11--4422 wwhheerree tthhee eelleeccttrroollyyttee ccoommppoossiittiioonn ffuurrtthheerr ccoommpprriisseess oonnee oorr mmoorree aaddddiittiivveess sseelleecctteedd ffrroomm tthhee ggrroouupp ccoonnssiissttiinngg ooff ccoorrrroossiioonn iinnhhiibbiittoorrss,, ssoolliidd eelleeccttrroollyyttee iinntteerrffaaccee ((SSEEII)) iimmpprroovveerrss,, pprroottoonn eevvoolluuttiioonn iimmpprroovveerrss,, sseellff--ddiisscchhaarrggee iinnhhiibbiittoorrss,, aannttii-- ggaassssiinngg aaggeennttss,, vviissccoossiittyy aaddjjuussttiinngg aaggeennttss,, ccaatthhooddee pprrootteeccttiioonn aaggeennttss,, ssaalltt ssttaabbiilliizzeerrss,, ccoonndduuccttiivviittyy iimmpprroovveerrss aanndd ssoollvvaattiinngg aaggeennttss..
EE4444.. AA cceellll aaccccoorrddiinngg ttoo aannyy ooff eemmbbooddiimmeennttss 11--4433 wwhheerree tthhee eelleeccttrroollyyttee ccoommppoossiittiioonn ccoonnttaaiinnss oonnee oorr mmoorree aaddddiittiivveess sseelleecctteedd ffrroomm tthhee ggrroouupp ccoonnssiissttiinngg ooff
fflluuoorriinnaatteedd ooiill,, ssooddiiuumm ssttaannnnaattee,, ssooddiiuumm cciittrraattee oorr ppoollyyaaccrryylliicc aacciiddss;;
HHFF oorr KKFF,, ooxxiiddeess oorr hhyyddrrooxxiiddeess ooff rraarree eeaarriihhss ssuucchh aass YY,, mmeettaall ppoorrpphhiinneess,, ffoorr eexxaammppllee NNii oorr FFee ppoorrpphhiinnee,, vviinnyylleennee ccaarrbboonnaattee,, vviinnyylleetthhyylleennee ccaarrbboonnaattee,, mmeetthhyylleennee eetthhyylleennee ccaarrbboonnaattee oorr ffiiuuoorroo-- eetthhyylleennee ccaarrbboonnaattee;;
ppoollyyggllyyccoollss,, ppooiiyyggllyyccooii aaiikkyyll eeiihheerrss,, ppooiiyyggllyyccooii aallkkyyii pphhoosspphhaattee eesstteerrss oorr ppoollyyssoorrbbaatteess ssuucchh aass ppoollyyeetthhyylleennee ggllyyccooll ((PPEEGG)),, ppoollyypprrooppyylleennee ggllyyccooll,, ppooiiyyssoorrbbaattee 2200,, ppoollyyssoorrbbaattee 4400 oorr ppoollyyssoorrbbaattee 8800 oorr aa mmiixxttuurree ooff PPEEGG 660000 aanndd ppooiiyyssoorrbbaattee 2200 oorr aa mmiixxttuurree ooff PPEEGG 660000 aanndd ZZnnOO;;
pphhoosspphhaattee eesstteerr--bbaasseedd ssuurrffaaccttaannttss,, pprrooppaannee ssuullttoonnee oorr ffiiuuoorroopprrooppaannee ssuullttoonnee;; aanndd
DD SSOO;;
ffoorr eexxaammppllee aatt aa lleevveell ooff ffrroomm aabboouutt 00..11 %% ttoo aabboouutt 1155%% bbyy wweeiigghhtt,, bbaasseedd oonn tthhee ttoottaall wweeiigghhtt ooff tthhee eelleeccttrroollyyttee ccoommppoossiittiioonn..
EE4455.. AA cceellll aaccccoorrddiinngg ttoo aannyy ooff tthhee pprreecceeddiinngg eemmbbooddiimmeennttss wwhheerree tthhee rreevveerrssiibbllee hhaallff cceeiill cchhaarrggee//ddiisscchhaarrggee eelleeccttrroocchheemmiiccaall rreeaaccttiioonn aatt tthhee nneeggaattiivvee eelleeccttrrooddee iiss
iIVV ++ ++ ++ e
Figure imgf000075_0001
iiVV
or
Figure imgf000075_0002
where
IV is a group IV element-based hydrogen storage material and
Si is a silicon-based hydrogen storage material,
E46. A cell according to any of the preceding embodiments comprising a positive electrode, the positive electrode comprising one or more cathode active materials selected from the group consisting of transition metals, transition metal oxides, transition metal hydroxides, transition metal oxide/hydroxides and transition metal fluorides; for example one or more materials selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, ir, Pt or Au;
oxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, ir, Pi or Au;
hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, !r, Pt or Au;
oxide/hydroxides of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt or Au; and
fluorides Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, I , Pt or Au.
Example 1
A present anode is employed in a SWAGELOK ceil assembly. A smaller anode is employed and therefore limits the capacity.
An anode is prepared via chemical vapor deposition of amorphous silicon on a nickel subsirate. The anode is 0.94 cm2 with an amorphous silicon film thickness of about 250 nm and a film mass of 51.7 μg. Thickness is measured with a scanning electron microscope (SEM). The cathode is sintered nickel hydroxide on a nickel mesh substrate. The electrolyte
composition is 2 molar acetic acid in 1-ethyl-3-methylimidazolium acetate.
The cell is cycled at a charge/discharge current density of 387 mA/g. The cell exhibits stable charge/discharge characteristics after 25 cycles as demonstrated in Fig. 1. The anode exhibits a charge plateau at ca. 1.4 V and a discharge plateau at ca. 1.2 V and a specific capacity of ca, 889 mAh/g at the 20,h cycle.
A 100 g anode alloy containing 1 weight percent (wt%) hydrogen (1 g or 1 mol) will have a capacity of 96500 A«sec (Faraday's constant) or 26.8 A«hour or 268 mAh/g of alloy. As present film exhibits a capacity of 889 mAh/g, the film charges 889/268 = 3.3 wt% hydrogen. This equates to greater than 0.9 H atoms charged per Si atom: 1 g/mol (H) / 28 g/mol (Si) = 3.57 wt%; 3.3/3.57 = 0.92 H per Si atom.
Example 2
Example 1 is repeated, with the ceil charged at a rate of 408 mA/g for 10 hours and discharged at 510, 1020, 2041 and 4082 mA/g to provide discharge capacities of 2604, 1681 , 1080 and 647 mAh/g respectively.
Example 3 Hydrogenated amorphous silicon (a-Si:H) thin films are deposited on nickel foil substrates in an AMAT P500Q plasma enhanced chemical vapor deposition (PECVD) system. To enhance the conductivity of the films, n-type doped a-Si:H thin films are obtained in-situ by the addition of phosphine in the working gas. The gas flow for PECVD is 60 seem siiane, 460 seem helium and 40 seem 5% phosphine in helium. The substrate temperature is 100°C, radio frequency (rf) power is SOW and working pressure is 3 Torr during deposition. The deposition time is 125 s and the average thickness of the as-deposited a-Si:H thin films is 247 nm. In addition to the CVD process, amorphous silicon samples are also prepared by an rf-sputtering technique, a kind of physical vapor deposition (PVD). Non-hydrogenated a-Si films are deposited on nickel substrates by rf-sputtering, followed by a subsequent ex-situ hydrogenation treatment. The sputter deposition source is an 800 diameter planar silicon target constructed of segments of monocrystalline silicon wafers (0.001 Ω cm, boron-doped) bonded to the sputtering cathode backing plate. Typical sputter deposition parameters include a gas flow of 3 seem argon, 8 mTorr glow discharge pressure, an rf (13.56 MHz) power of 486 W (1.5 W cm-2) and a target- substrate distance of 74 mm, with substrates held close to room temperature. Substrates are located in fixed positions underneath the target, and maximum deposition rates of approximately 125 A min_i are obtained in the racetrack region under these conditions. Post-deposition ex-situ hydrogenation treatments are conducted in a steel reactor vessel used in the pressure- concentration-temperature measurement. Variables of peak pressure (1 MPa and 6 MPa), peak temperature (30Q°C and 500°C), and anneal time (2 h and 20 min) are employed.
The non-aqueous electrolyte is 2M glacial acetic acid (CH3COOH, >99.7%, Alfa Aesar) in [EMIM] [Ac] (>95%, loLiTec GmbH) (1-ethyl-3-methyiimidazolium acetate). [E IM] [Ac] is baked at 1 15°C in a vacuum oven for 48 h to remove residual water. The water content of the ionic liquid is determined to be < 1000 ppm using a coulometric Karl Fischer titrator. Then glacial acetic acid is mixed with [EMIM] [Ac] with a volume ratio of 1.14: 10. The ionic conductivity at 6 mS cm-1 is measured by a conductivity meter (YSI model 3200). After the deposition of a-Si:H thin films on Ni substrates (1 ,25 cm x 1.25 cm), samples are cut into circular discs (diameter = 1.25 cm). The thickness of a-Si:H films varies between 247 nm and 3.0 mm and the active material mass varies between 70 mg and 840 mg. The electrochemical performance of the a-Si:H thin films are tested using a half-ceil configuration with P/N ratio (positive capacity/negative capacity) > 100. The positive electrode is a piece of sintered Ni(OH)2 that is fabricated in-house and used as standard positive electrodes for our Ni/MH battery research. Both electrodes are baked at 115°C in a vacuum oven for 12 h before cell assembly. A 1.25 cm (dia.) Swageiok-fype ceil is assembled in an Ar-fiiled glove box using an a-Si:H thin film anode and a sintered Ni(OH)2 cathode, separated by a standard nonwoven separator and clamped with two 1.25 cm (dia.) nickel rod current collectors. Then 1 mL of electrolyte is injected into the cell before the ceil is sealed for testing. The electrochemical charge/discharge tests are performed using an Arbin BT-2143 battery test station at constant currents and a discharge cut-off voltage at 0.6 V. To study the rate capability of a-Si:H anode, the current densities are varied between 510 and 4082 mA g_ . Cyclic voltammetry (CV) measurements are performed using Gamry's interface 1000 potentiostat galvanostat in a three- electrode Swagelok cell. The working electrode is an a-Si:H thin film on Ni foil and the counter electrode is a sintered Ni(OH)2 disc. A leak-free reference electrode (Warner Instruments) is inserted through the top port of the Swagelok ceil as reference, which has a standard potential of 0.24 V vs. standard hydrogen electrode in a 3.4 M KCI solution. Surface morphology and film thickness is measured using JEOL~JSIV16320F SE . The Raman shift is measured using an E- Z Raman spectroscopy system with a 532 nm excitation source. The instrument is calibrated with a signal from a silicon standard at 520 cm"1. Fourier transform infrared (FTIR) spectra are measured using Perkin Elmer Spotlight 400 FTIR Imaging System.
The a-Si:H anode prepared via CVD is charged to 1935 mAh g_1 at a rate of 2041 mA g-1 (~1C rate) and discharged at the same rate (~1 C) until a cutoff voltage at 0.6 V vs. the Ni(OH)? counter electrode. The initial discharge capacity is 888 mAh g"1 and gradually increases to 1418 mAh g-1 at the 38th cycle, which is more than four times higher than conventional the AB5 alloy used in Ni/MH batteries. Converting to the number of hydrogen per Si atom, it corresponds to SiHi.48. The capacity increase during initial cycling may be attributed to the activation of the a~ Si:H anode. For Si thin film anode in LIB (lithium ion battery), a similar phenomenon is reported and it is suggested that the capacity increase is due to the transition of crystalline Si to amorphous Si. As the a-Si:H thin films are already amorphous in this experiment, the cause is different from the crystalline Si case, in another report for amorphous Si thin film anode in LIB, it is proposed that the capacity increase is due to the enhanced lithium diffusion resulting from increased density of micro-crackings/grain boundaries during the initial cycles. Likewise, the capacity increase in this study may also be attributed to the enhanced hydrogen diffusion as a result of increased micro-crackings/grain boundaries developed during the first few cycles. The open circuit voltage after charging is 1.3 V. For the 1 st cycle test, charge and discharge voltage plateaus are found at 1.37 V and 1.24 V (middle point) respectively, and the charge/discharge overpotentiai did not show dramatic increase until the specific capacity reached maximum at the 38th cycle. Then the charge/discharge overpotentiai increased and capacity faded gradually. At the 100th cycle, the specific capacity decreases to 917 mAh g_1 and charge voltage plateau increased to a value above 1.7 V. In the discharge curve two plateaus are present at decreased voltages -1.0 V and 0,85 V, which are suspected to be correlated to the phase or Si- H bond structure changes in the films during cycling and needs to be explicated. The a-Si:H anode exhibits a long cycle life - 707 mAh g_1 at the end of 500 cycles and a discharge voltage plateau at around 0.9 V. As commonly found in non-aqueous LIB, the increased charge and discharge overpotentials upon cycling may result from the increased internal resistance due to the growth of solid electrolyte interface (SE!) between the electrolyte and electrodes, electrolyte degradation and/or the increased contact resistance arising from the lose contact of a-Si:H thin film from the nickel substrate. After 500 cycles, the cell is dismantled and visual inspection of the anode showed that the a-Si:H thin films remained intact.
The rate capability of the a-Si:H anode is tested. The anode is charged to 4082 mAh g-1 at a rate of 2041 mA g_1 and discharged at four different rates: 510, 1020, 2041 and 4082 mA g_1. The discharge capacity decreases dramatically with the increase of current density, and the obtained discharge capacities are 2604, 1681 , 1080 and 647 mAh g_1 , corresponding to SiH2 72 , SiHi .76 , SiHi .i 3 and SiHo es, respectively. The discharge capacity and coulombic efficiency at a constant discharge rate of 510 mA g-1 as a function of charge capacity are measured.
With the increase of charge capacity, discharge capacity increases whereas the coulombic efficiency decreases. The highest discharge capacity obtained is 3635 mAh g_1 when the a-Si:H anode is charged to 5752 mAh g 1, which is equivalent to about 3,8 hydrogen atoms stored in each silicon atom. This capacity is comparable with the highest capacity reported for a-Si thin film anode in LIB. The coulombic efficiency is 87% when the anode is charged to 1000 mAh g_1 , which declines to 63% for a charge capacity of 5752 mAh g_1. Such a coulombic efficiency is relatively low compared to LIB and the mechanism of capacity loss needs further investigation.
It I believed that during the charge process for an a-Si:H electrode, the weakly bonded protons in the non-aqueous electrolyte are reduced and adsorbed at the surface of the electrode, followed by a hydrogen absorption and diffusion in the bulk a-Si:H. During discharge, hydrogen diffuses toward the anode/electrolyte interface, is oxidized and is desorbed.
The anodic peak is observed at near -0.2 V vs. reference electrode, which results from the oxidation and desorption of absorbed hydrogen atom at the anode-electrolyte interface. With the increase of scan rate, the anodic peak current increases and the peak potential slightly shifts in the positive direction. Unlike typical metal hydride electrode in alkaline solutions, a full cathodic peak is observed at near -0.9 V vs. reference electrode, which benefits from the enlargement in electrochemical window of non-aqueous IL based electrolyte. There is about 0,3 V voltage gap between the hydrogen adsorption peak and the edge of the reduction of electrolyte, whereas for metal hydride electrode in an aqueous 30% KOH electrolyte the hydrogen adsorption peak is so close to the hydrogen evolution threshold that it overlaps with hydrogen evolution peak and cannot be differentiated. A plateau instead of a peak is often observed for metal hydride electrode in 30% KOH electrolyte and self-discharge cannot be ignored. Owing to their widened electrochemical window, nonaqueous IL (ionic liquid) electrolytes enable the use of redox couples with higher standard potential and thus further increase in energy density of proton conducting Ni/MH batteries are promising.
SEM micrographs are taken for an a-Si:H thin film before electrochemical cycling experiment and after 500 cycles. The as-deposited a-Si:H thin film exhibits a smooth surface and an average film thickness of 247 nm. After 500 cycles, the film surface becomes rougher and crackings are observed. However, the films remained attached to the Ni substrate and did not peel off. The average film thickness increases to 281 nm after 500 cycles, about 13% increase than the as-deposited films. As reported for LIB, volumetric expansion occurs anisotropically during the lithiation process, with the preferred expansion perpendicular to the film surface. While contraction occurs both in-plane with and perpendicular to the film surface during delithiation process, film crackings develop as a result. The findings for Si thin film anode in LIB can also explain the crackings and increased thickness after cycling found for a- Si:H thin films in this study. Initially micro-crackings formed, which led to enhanced hydrogen diffusion and initial capacity increase. With repetitive volume expansion and contraction, crackings grow and some active material loses contact with current collectors resulting in a gradual capacity fading.
To determine the bond structure change in a~Si:H thin films, Raman and FTIR
spectroscopy are conducted. Raman spectroscopy is sensitive to Si-Si bond structure while FTIR spectroscopy is effective to reveal the Si-H bond configuration. Raman spectra of an a- Si:H thin film before and after 500 cycles is performed. A typical Raman spectrum of a-Si:H thin film comprises of four Gaussian peaks, corresponding to transverse optic (TO), longitudinal optic (LO), longitudinal acoustic (LA) and transverse acoustic (TA) modes. The transition of amorphous to micro-crystaliine/crystaliine Si is differentiated from the peak wavenumber shift. A broad peak at 460-490 crrr1 results from the TO vibrational mode of amorphous silicon and a sharp peak at 512-520 crrr1 represents the TO mode of crystal grains of different sizes. A third peak near 500 cm-1 is from the bond dilation at the grain boundaries. Only one broad peak present is in the range of 460-520 cm-1 before and after 500 cycles. The broad peak centers at 480 cm-1 , which means that the film is purely amorphous. No noticeable Raman shift is observed before and after cycling, indicating that the a-Si:H thin films remain amorphous during cycling. FTIR spectra of a-Si:H thin films before and after 500 cycles is performed. The FTIR spectrometer has a limited range starting from 650 cm"1 , which is at the edge of the major absorption band centered near 630 crrr1 due to the wagging vibrational mode of Si
mono-hydride (Si-H). Less intensive absorption bands at 800-1000 cnr and near 2100 cm-1 are observed, which are assigned to the bending vibrational and stretching modes of Si dihydride (Si-H2) and poly-hydride complexes (Si-H2)n respectively. The absorption band near 2000cm"1 resulting from the stretching mode of Si-H is not observed. The absorption peaks due to S1-H2 and (Si-H shift toward lower wavenumbers and intensity increases slightly after 500 cycles. The most intensive Si-H peak near 630 cm"1 is often used to estimate the hydrogen content in a- Si:H thin films.
The electrochemical performance of rf-sputtering deposited Si thin films is performed. Non- hydrogenated a-Si films exhibit very low discharge specific capacities of less than 200 mAb g_ , and the capacity increases significantly after hydrogenation treatment, which may be attributed to enhanced hydrogen diffusion after hydrogenation. Specifically, a thicker sample NT (nickel tab) -92, ~3.G microns, hydrogenated with 6 MPa hydrogen pressure at 30Q°C for 2 h, shows a discharge capacity in excess of 2224 mAh g_1 after 3 cycles. However, capacity faded quickly afterwards. In contrast, a thinner sample NT-93, -1.2 microns, hydrogenated at 500°C and 1 MPa for 2 h exhibits a discharge capacity of 2377 mAh g 1 after 13 cycles and no sign of capacity fading after 14 cycles, A 1 mm-thick Si thin film anode in LIB exhibits a capacity of 3000 mAh g_1 for 12 cycles followed by a quick decline. Compared to the large volume change for a Si thin film anode during iithiation/deiithiation, it may have much smaller volume change during hydrogenation/dehydrogenation as hydrogen is much smaller than lithium. And thus the high capacity can be retained with longer lifetime for thicker (>1 mm) a-Si thin films. Several reference ex-situ hydrogenated a-Si:H thin films (1 MPa 300°C/2 h) performed poorly in cycling tests, yielding low capacities on the order of the non-hydrogenated a-Si films (< 200 mAh g-1). It appears hydrogen incorporation info the silicon network requires thermal activation, whether that process involves permanent microstructural changes of the silicon film or simply a relaxation-induced diffusion enhancement for the hydrogen species at high temperature. It is well known in thin film silicon technology that microcrystalline regrowth of amorphous films occurs at around 600°C.
To summarize, using both in-situ hydrogenated CVD and rf-sputtering followed by ex-situ hydrogenation, a-Si:H thin films are prepared and used as anodes in a proton conducting Ni/MH battery with non-aqueous ionic liquid based electrolyte, which exhibit high specific capacities and excellent cycle stabilities. In CVD grown thin films, a specific discharge capacity of 1418 mAh g_i is obtained at a discharge rate of 2041 mA g_1 for the 38th cycle and the capacity retained 707 mAh g- after 500 cycles; and a maximum capacity of 3635 mAh g 1 is obtained at a lower discharge rate. A 1.2 micron thick rf-spuftered a-Si:H thin film anode hydrogenaied at 500°C demonstrates a capacity of 2377 mAh g~\ while another 3.0 micron thick a-Si:H thin film exhibits a capacity of 2224 mAh g_1 at the 3rd cycle.

Claims

1. A stable silicon-based hydrogen storage negative electrode for electrochemical uses; the electrode comprising a hydrogen storage material comprising > 27 wt% silicon.
2. An electrode according to claim 1 where the hydrogen storage material comprises amorphous silicon,
3. An electrode according to claim 1 where the hydrogen storage material is hydrogenated.
4. An electrode according to claim 1 where the hydrogen storage material is comprised in a film in adherence to a substrate selected from metal, glass, inorganics and plastic.
5. An electrode according to claim 1 where the hydrogen storage material contains > 50 wt% Si based on the total weight of the hydrogen storage material.
6. An electrode according to claim 1 comprising > 50% by weight Si, based on the total weight of the negative electrode.
7. An electrode according to any of claims 1 to 8 in contact with an electrolyte composition which is pH neutral or acidic and allows for transport of protons.
8. An electrode according to claim 7 where the electrolyte composition comprises one or more ionic compounds selected from the group consisting of protic acids, protic ammonium compounds, protic oxonium compounds, aprotic ammonium compounds, aprotic oxonium compounds, aprotic phosphonium compounds and alkali or alkali earth metal salts.
9. An electrode according to claim 7 where the electrolyte composition comprises an ionic compound containing a cation selected from the group consisting of NH4, methylammonium, ethylammonium, dimethylammonium, diethylammonium, trimethylammonium,
triethyiammonium, tributyiammonium, diethylmethylammonium, hydroxyethylammonium, methoxymethyiammonium, dibutyiammonium, methylbutylammonium, anilinium, pyridinium, 2- methylpyridinium, imidazolium, 1-methylimidazolium, 1 ,2-dimethylimidazolium, imidazolinium, 1- ethylimidazolium, 1-(4-sulfobutyl)-3-methylimidazolium, 1-aliylimidazoiium, quinolinium, isoquinolinium, pyrroiinium, pyrrolininium or pyrrolidinium; 1 -butyl-l -methylpyrrolidinium, tetramethy!ammonium, tetraethylammonium, tetra-n- butylammonium, n-butyl-tri-ethylammonium, benzyl-tri-methylammonium, tri-n- butylmethylammonium, benzyl-tri-ethylammonium, 1-methylpyridinium, 1 -butyl-3,5- dimethylpyridinium, 1 ,2,4-trimethylpyrazolium, trimethylhydroxyethylammonium, tri- (hydroxyethyl)methylammonium, dimethyl-di(polyoxyethylene)ammonium, 1 ,2,3- trimethylimidazo!ium, 1 -butyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-allyl-3- methylimidazolium, 1-hydroxyethyl-3-methylimidazolium, 1 ,3-dimethylimidazolium, 1 -ethyl- 1 - methylpiperidinium, 4-ethyl-4-methylmorpholinium, 1 -(cyanomethyl)-3-methylimidazolium, 1-(3- cyanopropyl)pyridinium, 1 ,3-bis(cyanomethyl)imidazolium, 1-hexyl-3-methylimidazolium or 1 - ethyl-3-methylimidazolium; and
methyltriphenylphosphonium, tetraphenylphosphonium, tetrabutylphosphoniurn,
tributylmethylphosphonium, triethylmethylphosphonium, trihexyltetradecylphosphonium, tripheny!propyiphosphonium or tetrakis(hydroxymethy!)phosphoniLfm; and containing an anion selected from the group consisting of carboxylates, irnides, rnethides, nitrate, bifluoride, halides, borates, phosphates, phosphinates, phosphonates, sulfonates, sulfates, carbonates and aluminates,
10. An electrode according to claim 7 where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of F2P(C2F5) ", F3P(C2F5)3", F4P(C2F5)2-, F2P(C3F7)4-, FSPCCSFT ,
Figure imgf000084_0001
F2P(C4F9)4-, F3P(C4F9)3-, F4P(C4Fg)2-, perfiuoroalkylcarboxyiate, perfluoroalkylsulfonate, bis(perfluoroalkylsulfonyl)imide,
(perfluoroalkylsulfonyl)(perfluoroalkylcarboxyl)imide, tris(perfluoroalkylsulfonyl)methide, trifiuoroacefate, trifiuoromethanesuifonate, bis(trifluoromethylsulfonyl)imide,
tris(trifluoromethylsuifonyl)methide, tetrafluoroborate, bisoxaiatoborate, difluorooxalatoborate, di(trifluoroacetato)oxalatoborate, trisoxalatophosphate, tetrafiuorooxalatophosphate and di(trifluoroacetato)oxa!atoaluminate,
11. An electrode according to claim 7 where the electrolyte composition comprises an ionic compound containing a carboxylate anion of formula RCOO where R is hydrogen or hydrocarbyl,
12. An electrode according to claim 7 where the electrolyte composition comprises an ionic compound containing an anion selected from the group consisting of dicyanamide, N(S02F)2" [N(S02CF3)2]", bis(pentafluoroethylsulfonyl)imide,
(CF3S02)(CF3(CF2)3S02)~ or a (perfiuoroalkylsulfonyl)(perfluoroalkyicarboxyl)imide;
C(CF3S02)3~; HF2~; chloride, bromide, iodide or fluoride;
orthoborate, ieirahydroxyborate, tetraborate, tetraphenylborate, [B(3,5-(CF3)2C6H3)4]~, B(C2C>4)2~ (bis(oxalato)borate), difluoro(oxaiato)borate, di(trifluoroacetato)oxalatoborate, Β(06Ρ5)4~ or BF4 ~; dihydrogen phosphate, hydrogen phosphate, alkyl phosphate, dialkyl phosphate, phosphate, PFs", HP03F~, trisoxalatophosphate, tetrafluorooxalatophosphate, F2P(C2Fs)4~ F3P(C2Fs)3~, F4P(C2Fs)2- F2P(C3F7)4- F3P(C3F7)3-, F4P(C3F7)2-, F2P(C4F9)4- F3P(C4F9)3- or F4P(C4F9)2-; trifluoromethanesulfonate, p-toluenesuifonate or methanesulfonate;
hydrogensuifate, sulfate, thiosulfate, methylsulfate or ethylsulfate;
carbonate, hydrogencarbonate, methyicarbonate, ethylcarbonate or butylcarbonate; and AI(OC(CF3)3)4 " di(trifluoroacetato)oxalatoaluminate, tetrachloroa!uminate, tetraf!uoroaluminate, tetraiodoaluminate or tetrabromoaluminate.
13. An electrode according to claim 7 where the electrolyte composition comprises an ionic liquid.
14. An electrode according to claim 7 where the electrolyte composition comprises an ionic liquid selected from the group consisting of diethy!methylammonium trifluoromethanesulfonate, ethylammonium nitrate, triethylammonium methanesulfonate, 2-methy!pyridiniurn
trifluoromethanesulfonate, ammonium fluoride, methylarrsmoniurrs nitrate,
hydroxyethylammonium nitrate, ethylammonium nitrate, dimethylammonium nitrate, 1- methylimidazo!ium nitrate, 1-ethylimidazolium nitrate, t-butylammonium tetrafluoroborate, hydroxyethylammonium tetrafluoroborate, methylbutylammonium tetrafluoroborate,
triethylammonium tetrafluoroborate, imidazolium tetrafluoroborate, 1-methylimidazolium tetrafluoroborate, 1 ,2-dimethylimidazolium tetrafluoroborate, t-butylammonium triflate, 2- fluoropyridinium inflate, hydroxyethylammonium triflate, 1 ,2-dimethylimidazolium triflate, imidazolium triflate, 1-methylimidazolium hydrogensuifate, 1-methylimidazolium chloride, 1- methylimidazolium triflate, hydronium triflate, methylammonium mesylate, ethylammonium mesylate, butylammonium mesylate, methoxyethylammonsum mesylate, dimethylammonium mesylate, dibuty!ammonium mesylate, triethylammonium mesylate, dimethylethylammonium mesylate, hydronium hydrogensuifate, ammonium hydrogensuifate, methylammonium hydrogensuifate, ethylammonium hydrogensuifate, propylammonium hydrogensuifate, n- butylammonium hydrogensuifate, t-butylammonium hydrogensuifate, dimethylammonium hydrogensuifate, diethyiammonium hydrogensuifate, di-n-butylammonium hydrogensuifate, methylbutylammonium hydrogensulfate, ethylbutylammonium hydrogensulfate, trirnethylammonium hydrogensulfate, triethylammonium hydrogensulfate, tributylammonium hydrogensulfate, dimethylethylammonium hydrogensulfate, dibutylammonium fluorohydrogen phosphate, triethylammonium fluorohydrogen phosphate, tributylammonium fluorohydrogen phosphate, hydronium dihydrogen phosphate, methylammonium dihydrogen phosphate, efhy!ammonium dihydrogen phosphate, propylammonium dihydrogen phosphate, n- butylammonum dihydrogen phosphate, methoxyethylammonium dihydrogen phosphate, dimethylammonium dihydrogen phosphate, dibutylammonium dihydrogen phosphate, methylbutylammonium dihydrogen phosphate, ammonium bifiuoride, methylammonium bifluoride, ethylammonium bifiuoride and dimethylammonium bifiuoride,
15. An electrode according to claim 7 where the electrolyte composition comprises an ionic liquid selected from the group consisting of l-ethyi-S-methylimidazolium
trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3- methylimidazoiium bis(trifiuoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium acetate, 1- butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazoiium acetate (BMIM Ac), 1-bufyl-3-mefhylimidazoiium bis(trifluoromethylsulfonyl)imide, tri-n- butylmethylammonium methyl sulfate, 1-ethyl-2,3-dimethylimidazolium ethyisulfate, 1-butyl-3- methylimidazolium thiocyanate, 1-butyl-3-methylimidazolium tetrachloroaluminate, 1-butyl-3- methyiimidazoiium methylsuifafe, 1-butyl-3-methylimidazolium meihanesuifonate, 1 -butyl-3- methylimidazolium hydrogencarbonate, 1-butyl-3-methylimidazolium hydrogensulfate, 1-butyl-3- methyiimidazoiium chloride, 1 ,2,3-trimethylimidazolium methylsuifafe, tris- (hydroxyethyl)methylammonium methylsuifafe, 1 ,2,4-trimethylpyrazolium methylsuifafe, 1 ,3- dimefhylimdiazolium hydrogencarbonate, 1-ethyl-3-methylimidazolium hydrogencarbonate, 1- ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium tetrachloroaluminate, 1 -ethyl-3- methyiimidazoiium thiocyanate, 1-efhyl-3-methyiimidazolium methanesuifonate, 1 -ethyl-3- methylimidazolium hydrogensulfate, 1-ethyl-3-methylimidazolium ethyisulfate, 1 -ethyl-3- methylimidazoiium nitrate, 1~butylpyridinium chloride, 1-ethyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazoiium hexafluorophosphate, 1-butyl-3,5-dimethylpyridinium bromide, 1- ethyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide, 1-ethyl-2,3-dimethylimidazolium methyicarbonate, carboxymethyl-fributylphosphonium bis(trifluoromethylsulfonyl)imide, N- carboxyethyl-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, N-carboxymethyl- trimethylammonium bis(trifluoromethylsulfonyl)imide, N-carboxymethyl-methylpyridinium bis(trifiuoromethyisulfonyi)imide, hexyltrimethylammonium bis(trifiuromethyisulfonyl)imide, tetrabutylphosphonium methanesuifonate, tnethyimethyiammonium methyicarbonate, 1-ethyl-1- methylpiperidinium methyicarbonate, 4-ethyl-4-methy!morpho!inium methyicarbonate, 1-butyl-1- methylpyrrolidinium methyicarbonate, triethyimethylammonium dibuty!phosphate,
tributylmethylphosphonium dibutylphosphate, triethylmethylphosphonium dibutylphosphate, tetrabutylphosphonium tetrafluoroborate, tetrabutylphosphonium p-toluenesulfonate, tributylmethylphosphonium methyicarbonate, 1-ethyi-3-methylimidazolium hydrogencarbonate, tributylmethylammonium methyicarbonate, tributylmethylammonium dibutylphosphate, 1 -ethyl-3- methylimidazoiium dibutylphosphate, 1-butyl-3-methylimidazolium dibutylphosphate, 1- (cyanomethyl)-3-methylimidazoliurrs chloride, 1-(3-cyanopropyl)-3-methylimidazolium chloride, 1 -(3-cyanopropyl)-3-methyiimidazolium bis(trifluoromethyisulfonyl)imide, 1 -(3-cyanopropyi)-3- methylimidazolium dicyanamide, 1-(3-cyanopropyl)pyridinium chloride, 1-(3- cyanopropyl)pyridinium bis(trifluoromethylsulfonyl)imide, 1 ,3-bis(cyanomethyl)imidazolium chloride, 1 ,3-bis(cyanomethyl)imidazolium bis(trifluoromethylsulfonyl)imide, 1 ,3- bis(cyanopropyl)imidazoliurr) chloride, 1 ,3-bis(3-cyanopropyl)imidazolium
bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1 -butyl-3- methylimidazoiium tetrafluoroborate, 1-ethy!~3~methyiirnidazo!ium tetrafluoroborate, 1-ethyl~3~ methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, 1-hexyl-3-methylimidazolium chloride, tributylmethylphosphonium methyisulfate, triethylmethylphosphonium dibutylphosphate, trihexyltetradecyiphosphonium
bis(trifluromethylsulfonyl)imide, trihexyltetradecyiphosphonium bis(2,4,4- trimethylphenyl)phosphinate, trihexyltetradecyiphosphonium bromide,
trihexyltetradecyiphosphonium chloride, trihexyltetradecyiphosphonium decanoate,
trihexyltetradecyiphosphonium dicyanamide, 3-(triphenylphosphonio)propane-1 -sulfonate and 3- (triphenylphosphonio)propane-l-sulfonic acid tosylate,
16. An electrode according to claim 7 where the electrolyte composition comprises an ionic compound selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid, periodic acid, sodium bisuifate, potassium bisulfate, ammonium bisulfate, HAsFs, HBF4, H(OEt2)BF4, HPF6, ,H[N(S02CF3)2] and H[N(S02CF2CF3)2].
17. An electrode according to claim 7 where the electrolyte composition comprises a carboxyiic acid of formula RCOOH where R is hydrogen or hydrocarbyl or a sulfonic acid of formula RS03H where R is aikyl or aryl or alkyi or aryi substituted by one to three halogens.
18. An electrode according to claim 7 where the electrolyte composition comprises formic acid, acetic acid, acrylic acid, fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, propanoic acid, butyric acid, 3-methylbutanoic acid, valeric acid, hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, benzoic acid, salicylic acid, 2-, 3- or 4-nitrobenzoic acid; citric acid, oxalic acid, tartaric acid, glycolic acid, gluconic acid, malic acid, mandelic acid, nitrilotriacetic acid, N~(2~hydroxyethyl)~
ethylenediaminetriacetic acid, ethylenediaminetetraacetic acid, diethyleneaminepentaacetic acid, p-toluenesulfonic acid, phenyisulfonic acid, methanesLflfonic acid, trifluoromethanesulfonic acid, [H(OEt2)2][B[3,5-(CF3)2CeH3]4], [H(OEt2)2][B(C6F5)4] or [H(OEt2)2][AI(OC(CF3)3)4].
19. An electrode according to claim 7 where the electrolyte composition comprises one or more organic solvents selected from the group consisting of organic carbonates, ethers, g!ymes, ortho esters, polyalklene glycols, esters, lactones, glycols, formates, sulfones, sulfoxides, amides, alcohols, ketones, nitro solvents and nitrile solvents,
20. A rechargeable electrochemical cell comprising a negative electrode according to any of claims 1 to 6, a positive electrode, a casing having said electrodes positioned therein and an electrolyte composition in contact with the electrodes, where
the gravimetric energy density of the cell is > 100 Wh/kg and/or
the volumetric energy density of the cell is > 250 Wh/L and/or
the discharge capacity of the hydrogen storage material is > 800 mAh/g over 20 cycles or more.
21. A rechargeable electrochemical cell comprising a negative electrode according to any of claims 1 to 6, a positive electrode, a casing having said electrodes positioned therein and an electrolyte composition in contact with the electrodes, where the reversible half cell
charge/discharge electrochemical reaction at the negative electrode is
5 + + e- ["gjjjjjjjjjjjjjjjjjgg s |_| where Si is a silicon-based hydrogen storage material.
22. A rechargeable electrochemical cell comprising a negative electrode according to any of claims 1 to 6, a positive electrode, a casing having said electrodes positioned therein and an electrolyte composition in contact with the electrodes, the positive electrode comprising one or more cathode active materials selected from the group consisting of transition metals, transition metal oxides, transition metal hydroxides, transition metal oxide/hydroxides and transition metal fluorides.
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