Classifications

• • 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
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• • 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
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• • 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
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • 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
  • H01M10/0569—Liquid materials characterised by the solvents
• • 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
  • H01M4/04—Processes of manufacture in general
  • H01M4/0438—Processes of manufacture in general by electrochemical processing
  • H01M4/0464—Electro organic synthesis
  • H01M4/0466—Electrochemical polymerisation
• • 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
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
  • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• • 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
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
  • H01M4/1399—Processes of manufacture of electrodes based on electro-active polymers
• • 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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • 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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/624—Electric conductive fillers
• • 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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/624—Electric conductive fillers
  • H01M4/625—Carbon or graphite
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/661—Metal or alloys, e.g. alloy coatings
• • 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
  • H01M2004/021—Physical characteristics, e.g. porosity, surface area
• • 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
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
• • 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

Definitions

• the present invention relates to a cathode composition that can be used in a lithium-ion battery, to a process for preparing this composition, to such a cathode and to a lithium-ion battery, the cell or each cell of which incorporates this cathode.
• lithium storage batteries There are two main types of lithium storage batteries: lithium metal batteries, where the negative electrode is composed of lithium metal (a material that poses safety problems in the presence of a liquid electrolyte), and lithium-ion batteries. ion, where the lithium remains in the ionic state.
• Lithium-ion batteries consist of at least two faradic conducting electrodes of different polarities, the negative or anode electrode and the positive electrode or cathode, electrodes between which is a separator which consists of an electrical insulator impregnated with an aprotic electrolyte based on Li + cations ensuring the ionic conductivity.
• the electrolytes used in these lithium-ion batteries are usually constituted by a lithium salt, for example of formula LiPF 6 , LiAsF 6 , L1CF3SO3 or L1CIO4, which is dissolved in a mixture of non-aqueous solvents such as acetonitrile, tetrahydrofuran or most often a carbonate for example of ethylene or propylene.
• a lithium-ion battery is based on the reversible exchange of the lithium ion between the anode and the cathode during charging and discharge of the battery, and it has a high energy density for a very low mass thanks to to the physical properties of lithium.
• the active material of the anode of a lithium-ion battery is designed to be the seat of a reversible insertion / deinsertion of lithium and is typically made of graphite (theoretical capacity of 370 mAh / g and redox potential of 0.05 V with respect to the Li + / Li couple) or alternatively of oxides mixed metals among which there are lithiated titanium oxides of formula Li Ti 5 Oi 2, for example.
• the active ingredient of the cathode it is usually constituted:
• NMC lithiated oxides of nickel, manganese and cobalt
• NCA alloys known as "NCA” of lithiated oxides of nickel, cobalt and aluminum
• Electrodes must also contain an electrically conductive compound, such as carbon black and, to give them sufficient mechanical cohesion, a polymeric binder.
• an electrically conductive compound such as carbon black and, to give them sufficient mechanical cohesion, a polymeric binder.
• the lithium-ion battery electrodes are most often manufactured by a liquid process comprising successively a step of dissolving or dispersing the ingredients of the electrode in a solvent, a step of spreading the solution or dispersion obtained on a metal current collector, then finally a step of evaporation of the solvent.
• a liquid process comprising successively a step of dissolving or dispersing the ingredients of the electrode in a solvent, a step of spreading the solution or dispersion obtained on a metal current collector, then finally a step of evaporation of the solvent.
• Processes using an organic solvent such as that presented in US-A1-2010 / 0112441
• These solvents are toxic or flammable.
• the processes using an aqueous solvent their major disadvantage is that the electrode must be dried very thoroughly before it can be used, the traces of water limiting the useful life of lithium batteries.
• CN 106450201 A describes a process for the liquid manufacture of a lithium-ion battery cathode, which teaches the active use of a combined NCA lithiated oxide alloy. to another lithiated cobalt oxide (LCO) alloy, and as a binder a polyvinylidene difluoride (PVDF).
• LCO lithiated cobalt oxide
• PVDF polyvinylidene difluoride
• US-A-5,749,927 discloses a method for the continuous preparation by extrusion of lithium polymer battery electrodes, which comprises mixing the electrode active material with an electrical conductor and a solid electrolyte composition comprising a polymeric binder such as a polyacrylonitrile (PAN), a PVDF or polyvinylpyrrolidone (PVP), a lithium salt and a propylene carbonate / ethylene carbonate mixture in large excess relative to this polymer.
• PAN polyacrylonitrile
• PVDF polyvinylpyrrolidone
• Li salt a propylene carbonate / ethylene carbonate mixture in large excess relative to this polymer.
• the mass fraction of active material present in the obtained anode polymer composition is less than 70%, being clearly insufficient for a lithium-ion battery.
• the document WO-A1-2013/090487 teaches in its exemplary embodiments to use a PVDF as binder in a substantially solvent-free process for preparing a cathode composition for a lithium-ion battery whose active material is a lithium oxide alloy. NMC, depositing the cathode composition on a collector by friction.
• a fluorinated polyolefin such as PVDF or a tetrafluoroethylene polymer
• unmodified polyolefins such as those prepared from ethylene, propylene or butylene.
• US-B2-6,939,383 discloses using as a binder, in a lithium-ion battery electrode composition prepared without solvent in a multi-screw extruder, an ionically conductive polyether comprising a polar polymer of a alkene oxide such as a copolymer ethylene oxide-propylene oxide-allyl glycidyl ether, optionally combined with a non-ionically conductive polymer such as a PVDF, a PAN, PVP, an ethylene-propylene-diene terpolymer (EPDM) or a styrene-butadiene copolymer ( SBR) prepared in emulsion.
• the mass fraction of active material present in the electrode composition (a lithiated oxide of vanadium) is only 64.5%, which is clearly insufficient for a lithium-ion battery. .
• US-B1-7,820,328 teaches using a thermoplastic polymer as a binder in a wet or dry lithium-ion battery electrode composition with thermal decomposition of a sacrificial polymer such as ethyl cellulose. , an acrylic resin, a polyvinyl alcohol, a polyvinyl butyral or a polyalkene carbonate.
• a sacrificial polymer such as ethyl cellulose. , an acrylic resin, a polyvinyl alcohol, a polyvinyl butyral or a polyalkene carbonate.
• This decomposition is carried out under an inert atmosphere (i.e. non-oxidizing, eg under argon) for an anode composition and under either inert or oxidizing (e.g., air) atmosphere for a cathode composition.
• anode or cathode composition with a specific active ingredient and a binder, indicating only that the conditions of decomposition of the sacrificial polymer under an inert or oxidizing atmosphere are carefully controlled. so as not to degrade the other ingredients of the composition such as the binder which is thus not modified and can be chosen from polyethylenes, polypropylenes and fluorinated polyolefins such as PVDF or PTFE.
• the active ingredient for the cathode it may include lithiated oxides of nickel and / or cobalt.
• EP-B1 -2 618 409 in the name of the Applicant teaches to prepare by melting and without evaporation of solvent a cathode composition for lithium-ion battery comprising at least 90% of active material by mass (consisting for example of a carbon-coated lithium-iron phosphate of formula C-LiFePO 4 ), a polymeric binder consisting of a crosslinked diene elastomer such as a hydrogenated nitrile rubber (HNBR), and a non-volatile organic compound which can be used in the solvent of electrolyte of the battery.
• a cathode composition for lithium-ion battery comprising at least 90% of active material by mass (consisting for example of a carbon-coated lithium-iron phosphate of formula C-LiFePO 4 ), a polymeric binder consisting of a crosslinked diene elastomer such as a hydrogenated nitrile rubber (HNBR), and a non-volatile organic compound which can
• WO-A2-2015 / 124835 also in the name of the Applicant discloses a cathode composition for lithium-ion battery prepared by melting and without evaporation of solvent, using a sacrificial polymeric phase that is mixed an active material (which may be a lithiated oxide of a metal such as cobalt or manganese, or an alloy of NMC lithiated oxides), with a selected polymeric binder compatible with this phase for obtaining a precursor mixture, and then eliminated to obtain improved plasticization and fluidity during the implementation of the molten mixture despite a mass fraction of active ingredient in the composition greater than 80%.
• an active material which may be a lithiated oxide of a metal such as cobalt or manganese, or an alloy of NMC lithiated oxides
• This document recommends to its embodiments to use a binder derived from a polar elastomer (HNBR or ethylene-ethyl acrylate copolymer) for its compatibility with the sacrificial phase, which is also polar, which is a polyalkene carbonate, to avoid macroseparation. of phases following the mixing of the ingredients and control the implementation, the integrity and the porosity of the composition, obtained by heat treatment in air oven of the precursor mixture to decompose the sacrificial phase.
• HNBR polar elastomer
• binder polymers subject to their compatibility with the chosen sacrificial phase, so that the latter is continuous in the precursor mixture in which the binder is in the dispersed or co-continuous phase
• these other polymers may be chosen from polyolefins in the broad sense and elastomers such as polyisoprenes.
• This compatibility constraint therefore imposes the use of a binder of polarity similar to that of the sacrificial phase to avoid having two separate phases in the precursor mixture.
• the measured thickness of the cathode film obtained in the exemplary embodiments of this document it is 50 ⁇ .
• An object of the present invention is therefore to provide a new cathode composition for lithium-ion battery containing an active ingredient of more than 85% by weight, which is capable of being processed by melting and without solvent while being suitable. to impart to the cathode an improved surface density of energy compared with those obtained in the aforementioned prior art, with a reversibility in the first charge-discharge cycle, a capacitance and a cyclability (ie retention of the capacitance after a multitude of cycles) or at least not penalized.
• this object is achieved in that the Applicant has surprisingly discovered that if one thermally oxidizes under controlled conditions a precursor mixture obtained by molten route and without solvent and comprising an active material specifically based on an alloy lithiated oxides of nickel, cobalt and aluminum (NCA), an electrically conductive filler, a starting polymer intended to form a binder and a sacrificial polymeric phase, then this starting polymer can advantageously be modified by CO 2 oxygen groups so that the binder thus obtained makes it possible, by a synergistic effect with the NCA alloy, to obtain a composition forming a cathode film with a thickness and thus a grammage much higher than in the prior art without penalizing the strength of the film at cycling, which gives the cathode a surface density of energy and robustness improved in operation in a lithium-ion battery.
• NCA nickel, cobalt and aluminum
• a cathode composition according to the invention can be used in a lithium-ion battery, the composition comprising an active material which comprises a lithiated oxide alloy of nickel, cobalt and aluminum, an electrically conductive filler and a polymeric binder, and this composition is such that said polymeric binder comprises at least one modified polymer which is the product of a thermal oxidation reaction of a starting polymer and which incorporates oxygen groups comprising CO groups, the composition being capable of being obtained by melting and without solvent evaporation being the product of said applied thermal oxidation reaction a precursor mixture comprising said active material, said electrically conductive filler, said starting polymer and a sacrificial polymeric phase.
• this functionalization of the binder combined with this active cathode mode comprising or consisting of an NCA-type alloy advantageously makes it possible to obtain very high thicknesses and therefore very high grammages (thicknesses that can exceed 150 ⁇ and reach 250 ⁇ , as explained below) for the cathode films deposited on the current collectors, and therefore high surface densities of energy, without penalizing the robustness of these films in operation in a lithium-ion battery.
• the present invention differs from the prior art lithium-ion battery cathodes known from the Applicant, by its use of the NCA-type active material in a melt process without evaporation of solvent, and not by the liquid route which remains the most widespread to date.
• the composition, obtained by melt and without evaporation of solvent is the product of said thermal oxidation reaction which is applied to said precursor mixture by decomposing said sacrificial polymeric phase under an atmosphere comprising oxygen at an oxygen partial pressure of greater than 10 4 Pa and at an oxidation temperature between 150 ° C and 300 ° C (preferably between 190 ° C and 280 ° C), the oxygen of said atmosphere reacting with said starting polymer to produce said at least one modified polymer.
• the composition is capable of forming a film deposited on a metal current collector forming the cathode with said film, with a thickness of said film equal to or greater than 90 ⁇ and preferably between 150 ⁇ and 250 ⁇ .
• this unusually high thickness can exceed 150 ⁇ and reach 250 ⁇ can be obtained in a single pass (ie a single sequence of mixing steps and deposit from a single precursor mixture), and it is advantageously accompanied by excellent resistance of the cathode film obtained at the appearance of cracks or cracks in cycling in the lithium-ion battery.
• said sacrificial phase may comprise any polymer preferably having a thermal decomposition temperature that is at least 20 ° C. lower than that of the binder, and even more preferably at least one polymer of an alkene carbonate.
• said sacrificial polymeric phase may comprise at least one poly (alkene carbonate) polyol having end groups of which more than 50% (or even more than 80%) in moles comprise hydroxyl functions. .
• said at least one poly (alkene carbonate) polyol may be a linear aliphatic diol chosen from poly (ethylene carbonate) diols and poly (propylene carbonate) diols having a weight average molecular weight Mw between 500 g. / mol and 5000 g / mol, preferably between 700 g / mol and 2000 g / mol.
• said sacrificial polymeric phase comprises:
• said poly (alkene carbonate) polyol having a weight average molecular weight Mw of between 500 g / mol and 5000 g / mol, preferably according to a mass fraction in said phase of less than 50% (for example between 25% and 45%), and
• this minority presence in mass, in the sacrificial phase, of the poly (alkene carbonate) polyol of Mw of between 500 and 5000 g / mol makes it possible, unexpectedly, to improve the plasticization and the fluidity of the precursor mixture when it is set. implemented in the molten state and the mechanical strength of the composition obtained, in comparison with a majority presence in mass in said phase of this poly (alkene carbonate) polyol.
• the composition may also comprise a polysiloxane or polyisocyanate reactive compound, said at least one poly (alkene carbonate) polyol then being functionalized by grafting onto said siloxane group end groups. or isocyanates which are derived from said reactive compound and which block these end groups.
• this reactive compound with the sacrificial polymeric phase comprising this poly (alkene carbonate) polyol which is thus modified by grafting said compound makes it possible to solve a technical problem inherent in the use of NCA alloys, which resides in the fact that the NCAs catalyze an undesirable degradation of this sacrificial phase within the precursor mixture (ie before thermal decomposition of this phase), when this mixture is kept at room temperature (eg between 20 and 25 ° C).
• This problem of stability of the precursor mixture which softens and looses its cohesion due to the beginning of depolymerization of the poly (alkene carbonate) polyol catalyzed by the NCA, generally occurs after a few hours of storage at room temperature, typically after about 6 hours for some NCAs.
• said reactive compound of the invention makes it possible to carry out the process of the invention without having to immediately submit (ie within a few hours of its preparation) the precursor mixture to said oxidation reaction.
• said reactive compound is chosen from organodisiloxanes and organodiisocyanates, being even more preferably an aliphatic disiloxane such as, for example, hexamethylene disiloxane (HMDS), or an aliphatic diisocyanate such as, for example, hexamethylene diisocyanate (HMDI).
• organodisiloxanes and organodiisocyanates being even more preferably an aliphatic disiloxane such as, for example, hexamethylene disiloxane (HMDS), or an aliphatic diisocyanate such as, for example, hexamethylene diisocyanate (HMDI).
• a composition according to the invention may advantageously have a volume porosity, obtained by decomposition of said sacrificial polymeric phase, greater than 30% and preferably between 35% and 60%.
• said starting polymer for said polymeric binder comprises a non-hydrogenated acrylonitrile-butadiene copolymer (NBR) and / or a hydrogenated acrylonitrile-butadiene copolymer (HNBR) which little ( each have a mass ratio of units derived from acrylonitrile equal to or greater than 40% and which is (are) crosslinked by said thermal oxidation reaction to give said at least one modified polymer.
• NBR non-hydrogenated acrylonitrile-butadiene copolymer
• HNBR hydrogenated acrylonitrile-butadiene copolymer
• said polymeric binder can advantageously consist of a NBR and / or a HNBR thus modified (s).
• said starting polymer comprises a said hydrogenated acrylonitrile-butadiene copolymer (HNBR) which has:
• a mass ratio of units derived from acrylonitrile equal to or greater than 44%, preferably equal to or greater than 48%, and / or
• an iodine value measured according to the ASTM D5902-05 standard, greater than 10%.
• said starting polymer is an apolar aliphatic polyolefin and said at least one modified polymer derived therefrom has an oxygen atom mass content of between 2% inclusive. and 10%, preferably inclusive of between 3% and 7%.
• said polymeric binder may advantageously consist of at least one said apolar aliphatic polyolefin thus modified.
• carbonyl groups preferably comprising carboxylic acid, ketone and optionally ester functional groups
• these oxygenated groups coupled to this oxygen content by mass of 2% to 10% result in the fact that the said at least one polymer modified by these groups is more polar than the apolar aliphatic polyolefin of departure, while remaining generally apolar (ie little polar) by this functionalization whose rate in the chain of the modified polyolefin is controlled so as to be sufficient (cf mass content in oxygen d at least 2%) but not too high (cf oxygen mass content of at most 10%) to obtain the targeted electrochemical properties including the reversibility at the first cycle, the capacity for example at a C / 2 regime or C / 5 and the cyclability of the electrode (ie its capacity retention).
• the Applicant has established in comparative tests that functionalization of the apolar aliphatic polyolefin is insufficient (ie with said mass content below 2% and for example zero, the apolar polyolefin is not modified in this case) or excessive (ie with said mass content greater than 10%) led to electrochemical properties at least partially unsatisfactory for a lithium-ion battery electrode, with in particular a first charge-discharge cycle efficiency and a capacity at a C regime Both are insufficient for this application.
• this particular functionalization of the apolar aliphatic polyolefin makes it possible, unexpectedly, in view of the teaching of the above-mentioned document WO-A2-2015 / 124835. to couple this apolar aliphatic polyolefin to a polar sacrificial phase (eg based on at least one alkene carbonate polymer), therefore incompatible with this apolar starting polyolefin.
• a polar sacrificial phase eg based on at least one alkene carbonate polymer
• this apolar aliphatic polyolefin modified according to the invention can be used in a lithium-ion battery with a polar electrolyte of this battery, as shown below.
• polyolefin in a manner known in the present description an aliphatic or aromatic polymer, homopolymer or copolymer (“copolymer” including by definition terpolymers), derived from at least one alkene and optionally additionally from a comonomer other than an alkene.
• aliphatic polyolefin is meant a non-aromatic hydrocarbon polyolefin, which may be linear or branched, thus excluding in particular the polymers of an alkene oxide, alkene carbonate and homopolymers and copolymers derived from a vinylaromatic monomer such as styrene.
• apolar aliphatic polyolefins that can be used according to the invention exclude polyolefins with polar functional groups such as halogenated polyolefins, for example polyvinylidene polyfluorides or polyvinylchlorides (PVDF or PVDC), polyhexafluoropropylenes and polytetrafluoroethylenes (PTFE).
• PVDF polyvinylidene polyfluorides or polyvinylchlorides
• PVDF polyhexafluoropropylenes
• PTFE polytetrafluoroethylenes
• said apolar aliphatic polyolefin may be selected from the group consisting of homopolymers of an aliphatic olefin, the copolymers of at least two aliphatic olefins and their mixtures being preferably:
• Thermoplastic for example chosen from polyethylenes (eg low or high density, respectively LDPE or HDPE), polypropylenes (PP), polybutene-1 and polymethylpentenes, or
• an elastomer for example chosen from polyisobutylenes
• Thermoplastic for example selected from ethylene-octene (eg naming ELITE® 5230 G, are not limited to), ethylene-butene, propylene-butene and ethylene-butene-hexene, or
• an elastomer for example chosen from copolymers of ethylene and of an alpha-olefin such as ethylene-propylene copolymers (EPM) and ethylene-terpolymers; propylene-diene (EPDM, for example EPDM with the name Vistalon® 8600 (Exxon Mobil) or Nordel IP 5565 (Dow)).
• EPM ethylene-propylene copolymers
• EPDM propylene-diene
• said apolar aliphatic polyolefin is advantageously not cross-linked and may have a mass ratio of units derived from ethylene of greater than 50%, being for example a copolymer of ethylene and 1-octene and / or an EPDM.
• these apolar aliphatic polyolefins such as EPDM or polyethylenes, have the advantage of being inexpensive, especially in comparison with the HNBRs and the ethylene-ethyl acrylate copolymers used in the prior art in the melted process.
• the composition may comprise:
• said active material which comprises and advantageously consists of a said alloy of lithium nickel, cobalt and aluminum oxides of the NCA type,
• said polymeric binder having a mass fraction of less than 5%, preferably of between 1% and 4%, and
• said electrically conductive filler which is chosen from the group consisting of carbon blacks, cellulose-derived carbons, expanded graphites, carbon fibers, carbon nanotubes, graphenes and their mixtures, according to a mass fraction between 1% and 10%, preferably between 6% and 9%,
• said sacrificial polymeric phase being at least partially removed by said thermal oxidation applied to said precursor mixture.
• this mass fraction of more than 85% of said active material in the cathode composition contributes to imparting high performance to the lithium-ion battery incorporating it. It will also be noted that it is possible to incorporate one or other specific additives in a cathode composition according to the invention, in particular in order to improve or optimize its manufacturing process.
• a cathode according to the invention of lithium-ion battery is characterized in that the cathode comprises a current metal collector and a film covering it formed of a composition as defined above, said film having a thickness equal to or greater than 90 ⁇ obtained in a single pass preparation of said precursor mixture melt and without solvent and being able to resist the appearance of cracks or cracks after several charge-discharge cycles of the cathode within the lithium-ion battery.
• said film may advantageously have in a single pass a thickness of between 150 ⁇ and 250 ⁇ and be able to resist the appearance of said cracks or cracks after 20 cycles and preferably 40 charge cycles - Discharge of the cathode for example at a rate of C / 2.
• the cathode may be adapted to confer on the lithium-ion battery incorporating a first charge-discharge efficiency greater than 70% when said first charge-discharge cycle is for example implemented between 4.3 V and 2.5 V at a rate of C / 5.
• the cathode may be able to confer on the lithium-ion battery incorporating it, for cycles implemented between 4.3 V and 2.5 V:
• a capacity at a C / 2 rate greater than 100 mAh / g of cathode, preferably greater than 130 mAh / g of cathode, and / or
• a lithium-ion battery according to the invention comprises at least one cell comprising an anode, a cathode and an electrolyte based on a lithium salt and a non-aqueous solvent, and it is characterized in that the cathode is such that as defined above.
• a method of preparation according to the invention of a cathode composition as defined above comprises successively:
• ingredients of the composition comprising said active material, said starting polymer, said electrically conductive filler and said sacrificial polymeric phase, for the obtaining a precursor mixture of said composition
• said thermal oxidation reaction of said film under an atmosphere comprising oxygen at an oxygen partial pressure of greater than 10 4 Pa and at an oxidation temperature of between 150 ° C. and 300 ° C. for a period of variable oxidation (may vary from a few minutes to 30 minutes or more) for the total or partial elimination of said sacrificial phase and obtaining said at least one modified polymer.
• this sacrificial phase may be absent from the composition obtained or present therein in a degraded residual form.
• steps a), b), c) can be carried out in a single pass by a single film obtained from said precursor mixture, this film then having a thickness equal to or greater than 90 ⁇ and preferably between 150 ⁇ and 250 ⁇ .
• said sacrificial phase used in this process may comprise said at least one poly (alkene carbonate) polyol with end groups of which more than 50% (or even more than 80%) in moles comprise functional groups.
• hydroxyl preferably a linear aliphatic diol selected from poly (ethylene carbonate) diols and poly (propylene carbonate) diols of molecular weight Mw between
• said sacrificial polymeric phase used in this method of the invention comprises:
• said poly (alkene carbonate) polyol with a molecular mass Mw of between 500 g / mol and 5000 g / mol (liquid at ambient temperature and at atmospheric pressure), preferably with a mass fraction in said phase of less than 50%, and
• this minority presence in mass in said poly (alkene carbonate) polyol phase of Mw between 500 and 5000 g / mol makes it possible to improve the plasticization and the fluidity of the precursor mixture and the mechanical strength of the composition which comes from it.
• said ingredients mixed in step a) may further comprise said polysiloxane or polyisocyanate reactive compound which reacts during said mixing with said at least one poly (alkene carbonate) polyol by functionalizing it by grafting on said end groups of siloxane or isocyanate groups derived from said reactive compound, which is preferably selected from organodisiloxanes, such as aliphatic disiloxanes, and organodiisocyanates, such as aliphatic diisocyanates.
• organodisiloxanes such as aliphatic disiloxanes
• organodiisocyanates such as aliphatic diisocyanates.
• the mass fraction of said reactive compound in the precursor mixture it is preferably between 0.1% and 2%.
• this reactive compound makes it possible to simplify the process by allowing preservation of the precursor mixture during an increased lifetime (eg at least two days), thanks to the blocking of the poly (alkene) chain ends. carbonate) by this compound which is opposed to the depolymerization of the poly (alkene carbonate) polyol and thus stabilizes this mixture at room temperature, waiting for the oxidative heat treatment.
• step c) can advantageously be implemented by a controlled temperature rise of a starting temperature, preferably between 40 ° C. and 60 ° C., at said oxidation temperature and then by an isotherm at this oxidation temperature during said oxidation time, for thermally decomposing said sacrificial phase and modifying said starting polymer such that said at least one modified polymer has said oxygen groups comprising said CO groups.
• a starting temperature preferably between 40 ° C. and 60 ° C.
• the said thermal oxidation reaction is thus controlled so that in the composition obtained, the said starting polymer is modified as specified above (eg with in this second embodiment , the mass content of oxygen atoms in the polymer modified with CO and OH oxygen groups which is between 2% and 10% inclusive).
• this method of the invention requires precise control of said reaction to achieve this particular operation, adapting the conditions of temperature, pressure and thermal oxidation time to the selected starting polymer.
• said starting polymer used in step a) comprises a non-hydrogenated acrylonitrile-butadiene copolymer (NBR) and / or a hydrogenated acrylonitrile-butadiene copolymer (HNBR) which has (nt) each a mass ratio of units derived from acrylonitrile equal to or greater than 40% and which is (are) crosslinked in step c) by said thermal oxidation reaction.
• NBR non-hydrogenated acrylonitrile-butadiene copolymer
• HNBR hydrogenated acrylonitrile-butadiene copolymer
• the starting polymer according to this first mode is present in the precursor mixture of step a) without macroseparation of phases between binder and sacrificial phase when the latter is in accordance with said preferential mode (ie at least one poly (alkene carbonate) polyol).
• said starting polymer used in step a) comprises an apolar aliphatic polyolefin preferably selected from the group consisting of thermoplastic and elastomeric homopolymers of an aliphatic mono-olefin, thermoplastic copolymers and elastomers of at least two aliphatic monoolefins and mixtures thereof, said apolar aliphatic polyolefin being modified in step c) to give said at least one modified polymer having an oxygen atomic mass content of between 2% and 10%, and in said precursor mixture obtained in step a).
• the starting polymer according to this second mode is present in the precursor mixture of step a) with macroseparation of phases between the binder and the sacrificial phase thus forming two separate phases, when the sacrificial phase is in accordance with said preferred embodiment.
• said second embodiment of the invention goes against the teaching of the aforementioned document WO-A2-2015 / 124835, because it uses for the binder an apolar starting polymer not compatible with the polar sacrificial phase in said preferential mode (and also incompatible with the electrolyte also polar used for the battery), starting polymer which is an apolar aliphatic polyolefin (ie excluding in the family of polyolefins aromatic polyolefins and polar polyolefins) and which is modified in a manner very particular and controlled in the composition obtained after removal of the sacrificial phase, by adding these oxygenated groups such that said at least one modified polymer satisfies the aforementioned restricted range for its mass content of oxygen.
• FIG. 1 is a graph illustrating the absorbance spectra measured by Fourier Transform Infrared Spectroscopy (FTIR for short) showing the evolution of the absorbance as a function of the wavenumber of two elastomer films consisting of a first binder control consisting of an unmodified HNBR and a first binder according to the invention formed of the same modified HNBR, and
• FTIR Fourier Transform Infrared Spectroscopy
• FIG. 2 is a graph illustrating the absorbance spectra measured by FTIR showing the evolution of the absorbance as a function of the wavenumber of two elastomeric films consisting of a second control binder formed of an unmodified EPDM and a second binder according to the invention formed from the same modified EPDM.
• sacrificial polymeric phase a blend of two polypropylene carbonates (PPCs): one Nover Converge® Polyol 212-10 denominated diol-liquid and diol, and the other QPAC® 40-denominated solid of Empower Materials, present in this phase sacrificial at respective mass fractions of about 65% - 35% or 35% - 65%;
• PPCs polypropylene carbonates
• EPDM Vistalon® 8600 Exxon Mobil having a mass content of ethylene of 58.0% and a level of ethylidene norbornene (ENB) of 8.9%;
• HMDS hexamethylenedisiloxane
• the mixtures thus obtained were calendered at room temperature using an external Scamex cylinder mixer until a thickness of 600 ⁇ was obtained, then they were further calendered at 70 ° C. to reach a thickness of 90 ⁇ . at 250 ⁇ .
• the resulting precursor mixtures were deposited on a carbon-coated aluminum collector using a 70 ° C sheet-fed calender.
• the cathode precursor films thus prepared were placed in a ventilated oven in order to extract the sacrificial phase (solid and liquid CPAP). They were subjected to a controlled ramp temperature of 50 ° C to 250 ° C and an isotherm of 30 min. at 250 ° C by subjecting them to thermal oxidation in ambient air, to decompose this sacrificial phase and functionalize the corresponding binder d1) or d2).
• control composition C1 with the precursor mixture of composition 18 subjected to the same treatment was carried out.
• the precursor mixture of 18 but not according to the invention because under an inert atmosphere (ie non-oxidizing), in a rotary kiln under nitrogen with a nitrogen flow rate of 1 L / min.
• compositions according to the invention were thus obtained 11, 12, 13, 14, 16, 17 each comprising a binder consisting of said modified HNBR, and compositions according to the invention 15 and 18 each comprising a binder consisting of said modified EPDM, with respective mass fractions of the two liquid and solid CPPs in the sacrificial phase of about 65% -35% for 11 -12 and about 35% -65% for 13-18.
• Table 1 below lists the characteristics of the precursor mixtures and compositions obtained (mass fractions).
• compositions obtained 11 -18 each had a mass fraction of active material, consisting of an alloy NCA, equal to 90%, and a mass fraction of binder modified according to the invention Id1) or Id2), respectively constituted of said HNBR or said EPDM, ranging from 1.8% (compositions I6-I8) to 3% (compositions 11-15).
• the precursor mixture from which the composition 12 comprising a stabilizing agent (HMDS) was obtained could advantageously be stored at room temperature for more than 48 hours, effectively opposing the depolymerization of the solid CPAP liquid-CPAP sacrificial phase. to the action of the active ingredient NCA.
• HMDS stabilizing agent
• the volume porosity of the compositions 11 -13, 16 was 37.7%, that of the compositions 14, 15, 17 and 18 was higher (about 50%). Characterization of modified binders according to the invention:
• the binders d1) and d2), unmodified and modified according to the invention, have been characterized during this process by the melt method, by the FTIR ("FTIR” technique for giving “Fourier transform infrared spectroscopy”) giving absorbance spectra. depending on the wave number.
• FTIR FTIR
• absorbance spectra depending on the wave number.
• a film consisting of said HNBR (Zetpol® 0020) 100 ⁇ thick was deposited on copper, and treated for 30 minutes at 240 ° C in air. This film was then studied by IRTF in "ATR" mode (for "attenuated total reflectance” in English, i.e. attenuated total reflectance).
• FIG. 1 shows the two spectra obtained S1 and S2, respectively before and after this annealing.
• the spectrum S2 after this annealing shows:
• the five Cd2 films thus deposited were then treated in a controlled manner for 30 minutes. at 250 ° C. under ambient air, so as to obtain five films Id2 modified binder according to the invention each comprising CO and OH groups modifying d2).
• the Cd2 and Id2 films were then studied by IRTF in "ATR" mode.
• the cathodes (16 mm diameter, surface 2.01 cm 2 ) were punched out and weighed.
• the mass of active material was determined by subtracting the mass of the bare current collector prepared under the same conditions (heat treatments). They were put in an oven directly connected to a glove box. They were dried at 100 ° C under vacuum for 12 hours and then transferred to the glove box (argon atmosphere: 0.1 ppm H 2 O and 0.1 ppm O 2).
• the button cells (CR1620 format) were then assembled using a lithium metal counter-electrode, a Cellgard 2500 separator and a LiPF6 EC / DMC battery grade electrolyte (50% / 50% by mass ratio). Batteries were characterized on a Biology VMP3 potentiostat, in constant current charge / discharge cycles between 4.3 V and 2.5 V. The diet was C / 5 considering the mass of active ingredient and a theoretical capacity of 170 mAh / g.
• the capacities were evaluated during the first discharge for lithium deisertion (ie initial capacity after the first charge-discharge cycle), the second discharge (first cycle performance measurement), after 20 cycles and after 40 cycles, to calculate the retention rate (in%) defined by the capacity ratio at 20 or 40 cycles on the first cycle capacity at one same scheme (C / 2).
• the capacities at C, 2C and 5C regimes for these cathodes were measured (all these capacities being expressed in mAh per g of cathode).
• Table 2 below gives the characterization results for the cathodes 11-18 in each cell thus obtained, it being specified that films of different thicknesses were obtained for each composition 14, 15, 16, 17, 18, and that the above-mentioned control test for the composition C1, resulting from the same precursor mixture as 18 but thermally degraded under a nitrogen (non-oxidizing) atmosphere, was furthermore carried out.
• Table 2 shows the obtaining of very high thicknesses, in particular for cathode compositions 16 to 18 (thicknesses greater than 150 ⁇ , or even 200 ⁇ ), which generates also high surface energy densities for these cathodes according to US Pat. 'invention. It was verified that the cathode films of these compositions 11-18 according to the invention were free of cracks or cracks during cycling.
• Table 2 also shows that these compositions 11 -18 of the invention make it possible to obtain high yields in the first cycle (greater than 70%) indicating satisfactory reversibility, and capacities at C / 5, C regimes. / 2, C, 2C and if appropriate 5C equally satisfactory.
• Table 2 also shows a very satisfactory cyclability for the cathode film 17 of the invention having a thickness of 70 ⁇ after 20 and even 40 cycles (see the rate of retention of capacity at C / 2 after 20 and 40 cycles which is greater than 95%).
• 11 and 12 show that the use of HMDS in 12 as a stabilizing agent does not really penalize the electrochemical properties of cathode 12 with respect to 11;

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