WO2022121294A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

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Publication number
WO2022121294A1
WO2022121294A1 PCT/CN2021/104025 CN2021104025W WO2022121294A1 WO 2022121294 A1 WO2022121294 A1 WO 2022121294A1 CN 2021104025 W CN2021104025 W CN 2021104025W WO 2022121294 A1 WO2022121294 A1 WO 2022121294A1
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negative electrode
electrochemical device
electrolyte
silicon
mass
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English (en)
French (fr)
Inventor
张水蓉
张丽兰
袁晓
唐超
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to EP21902006.2A priority Critical patent/EP4250424A4/en
Publication of WO2022121294A1 publication Critical patent/WO2022121294A1/zh
Priority to US18/331,320 priority patent/US20230318038A1/en
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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
    • 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
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • 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
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0034—Fluorinated 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • 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
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • 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
    • 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 application relates to the field of electrochemical technology, and in particular, to an electrochemical device and an electronic device.
  • Electrochemical devices such as lithium-ion batteries
  • electronic products such as mobile phones and notebook computers in recent years.
  • the requirements for the energy density of electrochemical devices are getting higher and higher.
  • silicon materials have received more and more attention.
  • the theoretical capacity of silicon materials as a negative electrode material is much higher than that of existing carbon materials, but the volume change of silicon materials during the process of lithium deintercalation is relatively high. It is easy to cause the rupture of the SEI (solid electrolyte interphase) film at the negative electrode interface, especially during the cycle process, the silicon material continuously deintercalates lithium, resulting in the continuous rupture of the SEI film and exposing a new interface. The interface will react with the electrolyte, consuming the electrolyte and active lithium, resulting in cycle decay, and the conductivity of silicon materials is poor.
  • the use of silicon materials will lead to an increase in the DC resistance of electrochemical devices.
  • the electrical conductivity of chemical devices is an issue that needs to be addressed.
  • the present application proposes an electrochemical device, including a positive electrode, a negative electrode and an electrolyte; the electrolyte includes: fluoroethylene carbonate and non-fluorinated cyclic carbonate, and the percentage of fluoroethylene carbonate in the mass of the electrolyte is: a%, the percentage of non-fluorinated cyclic carbonate in the mass of the electrolyte is b%, and 0.05 ⁇ a/b ⁇ 2.5.
  • the ratio between the fluoroethylene carbonate and the non-fluoro cyclic carbonate it can be ensured that the fluoroethylene carbonate will not be too much compared to the non-fluoro cyclic carbonate and cause electrochemical damage.
  • the DC resistance of the device is increased, and at the same time, it is ensured that the cycle performance of the electrochemical device is not reduced due to too little, so that the electrochemical device has better cycle performance and lower DC resistance at the same time.
  • the negative electrode material may undergo volume expansion due to de-intercalation of lithium during the cycle process, causing the SEI film of the negative electrode material to rupture, while fluoroethylene carbonate can continuously reduce the SEI of the negative electrode material during the cycle process of the electrochemical device.
  • the membrane is repaired to improve the cycle performance of the electrochemical device, but the viscosity of fluoroethylene carbonate itself is relatively large. If the amount of fluoroethylene carbonate added is too large, the conductivity of the electrolyte may decrease. Therefore, by limiting Its content thus improves the cycle performance while preventing a decrease in the conductivity.
  • the negative electrode includes: a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, the negative electrode active material layer includes a negative electrode material, the negative electrode material includes a silicon-containing material, and the amount of silicon per unit coating area on the negative electrode current collector is
  • the mass of the element is X mg/cm 2 , and 0.1 ⁇ X ⁇ 1.3, in some embodiments, 0.2 ⁇ X ⁇ 1.3.
  • the negative electrode material of the electrochemical device includes a silicon-containing material, which can improve the specific capacity of the negative electrode material of the electrochemical device. Since the volume expansion of the silicon material during the cycle is relatively obvious, by limiting the amount of silicon per unit coating area on the negative electrode current collector The mass of the element thus limits the expansion of the anode material due to cycling.
  • a/b Z, and 0.76 ⁇ Z/X ⁇ 2.5, the silicon content, the fluoroethylene carbonate and the non-fluorinated cyclic carbonate content are matched, so as to improve the stability of the SEI film. At the same time, degradation of cycle performance and increase in DC resistance are prevented.
  • the electrolyte further includes: non-fluorinated chain ester, the percentage of non-fluorinated chain ester in the electrolyte is c%, and 0.1 ⁇ b/c ⁇ 1, in some embodiments, 0.25 ⁇ b/c ⁇ 0.81, the non-fluorinated cyclic carbonate includes: at least one of ethylene carbonate or propylene carbonate.
  • the viscosity of non-fluorinated chain esters is low. Adding non-fluorinated chain esters to the electrolyte is beneficial to reduce the overall viscosity of the electrolyte.
  • the relative permittivity of non-fluorinated chain esters is low, and adding too much The non-fluorinated chain ester will reduce the relative permittivity of the electrolyte as a whole.
  • the viscosity of the electrolyte can be reduced while ensuring that the electrolyte has a sufficiently high permittivity.
  • the negative electrode further includes: a conductive layer located between the negative electrode current collector and the negative electrode active material layer; the thickness d of the conductive layer satisfies: 0.3 ⁇ m ⁇ d ⁇ 1.5 ⁇ m.
  • the silicon-containing material has a large volume expansion during the charge and discharge process, and the negative electrode active material layer may be detached from the negative electrode current collector due to the expansion. Therefore, a conductive layer is arranged between the negative electrode active material layer and the negative electrode current collector.
  • the mass ratio of ethylene carbonate and non-fluorinated cyclic carbonate meets the appropriate conditions, it matches the thickness d of the conductive layer, which can buffer the deformation caused by the expansion of the negative electrode active material layer and prevent the detachment from the negative electrode current collector.
  • d is less than 0.3 ⁇ m It may be that the effect of buffering expansion and deformation is poor because the conductive layer is too thin, and when d is greater than 1.5 ⁇ m, the volume energy density of the electrochemical device may decrease.
  • the silicon-containing material includes: at least one of SiO x , silicon carbide or silicon element, wherein 0.5 ⁇ x ⁇ 1.5; the surface of the silicon-containing material has a protective layer, and the protective layer contains a metal element; the metal
  • the elements include: at least one of Al, Ti, Mn, V, Cr, Co or Zr.
  • the volume expansion of the silicon-containing material can be limited by the protective layer, and the metal elements contained therein can improve the electrical conductivity of the protective layer.
  • the mass ratio of the metal element to the negative electrode active material layer is r1, and 0.5ppm ⁇ r1 ⁇ 15000ppm. In some embodiments, 180ppm ⁇ r1 ⁇ 4520ppm, at this time, the electrochemical device has better cycle performance and lower DC resistance.
  • the mass ratio of the silicon-containing material to the negative electrode active material layer is r2, and 0.5% ⁇ r2 ⁇ 85%.
  • r2 is less than 0.5%, the effect of silicon-containing materials on the improvement of specific capacity is not obvious.
  • r2 is greater than 85%, due to excessive silicon-containing materials, the volume expansion of the negative electrode active material layer during charge and discharge is too large, which may lead to Electrochemical devices have poor stability, resulting in increased DC resistance.
  • the porosity of the negative active material layer is 20% to 30%.
  • the porosity is less than 20%, the contact between the electrolyte and the negative electrode material may be reduced, resulting in insufficient infiltration of the negative electrode material by the electrolyte, and when the silicon-containing material expands, the internal stress of the negative electrode active material layer increases due to the low porosity.
  • the porosity is greater than 30%, the overall conductivity of the negative electrode active material layer may decrease due to the excessively large gaps between the particles of the negative electrode material, thereby increasing the DC resistance.
  • the present application also proposes an electronic device, including the electrochemical device according to any one of the above.
  • An electrochemical device provided in an embodiment of the present application includes a positive electrode, a negative electrode, and an electrolyte; the electrolyte includes: fluoroethylene carbonate and non-fluorinated cyclic carbonate, and the percentage of fluoroethylene carbonate in the electrolyte mass is a%, the percentage of non-fluorinated cyclic carbonate in the electrolyte mass is b%, and 0.05 ⁇ a/b ⁇ 2.5.
  • the electrochemical devices (especially those containing silicon materials) proposed in the examples of the present application have improved cycle performance and reduced DC resistance.
  • an electrochemical device including a positive electrode, a negative electrode, and an electrolyte; the electrolyte includes: fluorinated ethylene carbonate and non-fluorinated cyclic carbonate, fluorinated ethylene carbonate
  • the percentage of ethylene carbonate in the mass of the electrolyte is a%
  • the percentage of non-fluorinated cyclic carbonate in the mass of the electrolyte is b%, and 0.05 ⁇ a/b ⁇ 2.5.
  • the non-fluorinated cyclic carbonate includes at least one of ethylene carbonate or propylene carbonate.
  • fluoroethylene carbonate can repair the SEI film of the negative electrode material and improve the cycle performance of the electrochemical device, but its viscosity is high, and adding a large amount of fluoroethylene carbonate will cause the conductivity of the electrolyte to decrease , the non-fluorinated cyclic carbonate has good electrical conductivity, and considering the high dielectric constant of fluoroethylene carbonate, the non-fluorinated cyclic carbonate can be reduced, so that the fluorinated ethylene carbonate and the non-fluorinated cyclic carbonate The content of cyclic carbonate needs to be balanced.
  • the negative electrode material especially the negative electrode material containing silicon material, may undergo volume expansion due to lithium deintercalation during the cycle, causing the SEI film of the negative electrode material to rupture, while fluoroethylene carbonate can
  • the SEI film of the negative electrode material is continuously repaired, thereby improving the cycle performance of the electrochemical device. Therefore, in some embodiments, a certain amount of fluoroethylene carbonate is added to the electrolyte; Vinyl ester itself has a relatively high viscosity. If the amount of fluoroethylene carbonate added is too large, the conductivity of the electrolyte may decrease. Therefore, 10.5 ⁇ a ⁇ 25 is defined in some embodiments of the present application.
  • the negative electrode comprises: a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector, the negative electrode active material layer comprises a negative electrode material, the negative electrode material comprises a silicon-containing material, and the negative electrode current collector is coated per unit area
  • the mass of the middle silicon element is X mg/cm 2 , and 0.1 ⁇ X ⁇ 1.3, preferably, 0.2 ⁇ X ⁇ 1.3.
  • the negative electrode active material layer can be arranged on one or both sides of the negative electrode current collector. If the negative electrode active material layer is provided on both sides of the negative electrode current collector, the mass of silicon per unit coating area on the negative electrode current collector refers to the negative electrode current collector.
  • the negative electrode material of the electrochemical device includes a silicon-containing material, so the specific capacity of the negative electrode material of the electrochemical device can be improved; since the volume expansion of the silicon material during the cycle is relatively obvious, by limiting the negative electrode current collector
  • the mass X mg/cm 2 of silicon element per unit coating area satisfies 0.1 ⁇ X ⁇ 1.3 to limit the amount of silicon-containing material, thereby limiting the expansion of the negative electrode material due to cycling.
  • a/b Z, and 0.76 ⁇ Z/X ⁇ 2.5.
  • the extent of the rupture of the SEI film caused by the expansion of the negative electrode material is related to the amount of the silicon-containing material, that is, the larger X is, the greater the amount of fluoroethylene carbonate needed to repair the SEI film, so 0.9 ⁇ Z/X thus Ensure that the amount of fluoroethylene carbonate is sufficient to repair the SEI film of the negative electrode material, and at the same time limit Z/X ⁇ 2.5 to prevent the excessive amount of fluoroethylene carbonate from reducing the cycle performance and increasing the DC resistance of the electrochemical device.
  • the electrolyte further includes: a non-fluorinated chain ester, the percentage of the non-fluorinated chain ester in the mass of the electrolyte is c%, and 0.1 ⁇ b/c ⁇ 1, preferably, 0.25 ⁇ b/c ⁇ 0.81.
  • the viscosity of non-fluorinated chain esters is low. Adding non-fluorinated chain esters to the electrolyte is beneficial to reduce the overall viscosity of the electrolyte. However, the relative permittivity of non-fluorinated chain esters is low, and adding too much Non-fluorinated chain esters will reduce the overall relative permittivity of the electrolyte.
  • the electrolyte In order to ensure the dissolution and ion conduction of lithium salts in the electrolyte, the electrolyte must have a sufficiently large polarity, and only the relative permittivity is high enough. Only the electrolyte can reduce the strong electrostatic attraction of ions between the positive and negative electrodes, so that the ions can be dissociated into free ions. Therefore, in this application, 0.1 ⁇ b/c ⁇ 1, preferably 0.25 ⁇ b/c ⁇ 0.81, is controlled in this application. While maintaining the viscosity of the liquid, ensure that the electrolyte has a sufficiently high dielectric constant.
  • the non-fluorinated chain esters include: dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethyl propyl carbonate, methyl formate, Methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, propyl propionate, isopropyl propionate ester, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, or ethyl valerate.
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • ethyl propyl carbonate methyl
  • the negative electrode further includes: a conductive layer located between the negative electrode current collector and the negative electrode active material layer; the thickness d of the conductive layer satisfies: 0.3 ⁇ m ⁇ d ⁇ 1.5 ⁇ m.
  • the silicon-containing material has a large volume expansion during the charging and discharging process, which may cause the negative electrode active material layer to be detached from the negative electrode current collector due to the expansion. Therefore, a conductive layer is arranged between the negative electrode active material layer and the negative electrode current collector, and the conductive layer can buffer the negative electrode activity. The deformation caused by the expansion of the material layer prevents separation from the negative electrode current collector.
  • d When d is less than 0.3 ⁇ m, the effect of buffering expansion and deformation may be poor because the conductive layer is too thin. When d is greater than 1.5 ⁇ m, it may lead to the volume energy density of the electrochemical device. reduce. Therefore, 0.3 ⁇ m ⁇ d ⁇ 1.5 ⁇ m is defined in this application.
  • the conductive material of the conductive layer may include any conductive material as long as it does not cause chemical changes.
  • conductive materials include carbon-based materials (eg, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotubes, graphene, etc.), metal-based materials (eg, metal powders, metal fibers, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (eg, polyphenylene derivatives), and mixtures thereof.
  • the silicon-containing material includes: at least one of SiOx, silicon carbon compound or silicon element, wherein 0.5 ⁇ x ⁇ 1.5.
  • the surface of the silicon-containing material has a protective layer, and the protective layer contains metal elements; the metal elements include: at least one of Al, Ti, Mn, V, Cr, Co or Zr.
  • the mass ratio of the metal element to the negative electrode active material layer is r1, and 0.5ppm ⁇ r1 ⁇ 15000ppm. In some embodiments of the present application, when 0.5ppm ⁇ r1 ⁇ 15000ppm, the electrochemical device has better cycle performance and lower DC resistance. Preferably, 180ppm ⁇ r1 ⁇ 4520ppm.
  • the mass ratio of the silicon-containing material to the negative electrode active material layer is r2, 0.5% ⁇ r2 ⁇ 85%.
  • r2 0.5%
  • the effect of silicon-containing materials on the improvement of specific capacity is not obvious.
  • r2 is greater than 85%, due to excessive silicon-containing materials, the volume expansion of the negative electrode active material layer during charge and discharge is too large, which may lead to Electrochemical devices have poor stability and cause increased DC resistance.
  • the porosity of the anode active material layer is 20% to 30%.
  • the porosity is less than 20%, the contact between the electrolyte and the negative electrode material may be reduced, resulting in insufficient infiltration of the negative electrode material by the electrolyte, and when the silicon-containing material expands, the internal stress of the negative electrode active material layer increases due to the low porosity.
  • the porosity is greater than 30%, the overall conductivity of the negative electrode active material layer may decrease due to the excessively large gaps between the particles of the negative electrode material, thereby increasing the DC resistance.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode material.
  • the positive electrode material can be, for example, lithium cobalt oxide, lithium nickel cobalt manganate, lithium iron phosphate, or the like.
  • a conductive agent or a binder may be added to the positive electrode of the above-mentioned electrochemical device.
  • the conductive agent includes a carbon material, and the carbon material may include conductive carbon black, graphite, graphite At least one of olefins, carbon nanotubes, carbon fibers or carbon black.
  • the binder may include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyamide At least one of acrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyethylene pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene .
  • the electrolyte further includes: 1,3-propane sultone (PS), 1,4 butane sultone, vinylene carbonate (VC) or vinyl sulfate (DTD) ) at least one of them.
  • PS 1,3-propane sultone
  • VC vinylene carbonate
  • DTD vinyl sulfate
  • the electrolyte includes a lithium salt.
  • Lithium salts include: inorganic lithium salts, such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiSbF 6 , LiSO 3 F, LiN(FSO 2 ) 2 , etc.; fluorine-containing organic lithium salts, such as LiCF 3 SO 3 , LiN ( FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic lithium 1,3-hexafluoropropanedisulfonimide, cyclic 1, Lithium 2-tetrafluoroethanedisulfonimide, LiN(CF 3 SO 2 )(C 4 F 9 SO 2 ), LiC(CF 3 SO 2 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 4 (C 2 F 5 ) 2 , LiPF 4 (CF 3 ) 3 , Li
  • a separator is provided between the positive electrode and the negative electrode.
  • the separator includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • the polyethylene includes at least one selected from high density polyethylene, low density polyethylene or ultra-high molecular weight polyethylene.
  • polyethylene and polypropylene they have a good effect on preventing short circuits and can improve the stability of the battery through the shutdown effect.
  • an inorganic or organic coating is applied to the surface of the separator to enhance the hardness of the cell or to improve the adhesion between the separator and the interface of the positive and negative electrodes.
  • the surface of the isolation membrane may further include a porous layer, the porous layer is disposed on at least one surface of the isolation membrane, the porous layer includes inorganic particles and a binder, and the inorganic particles are selected from aluminum oxide (Al 2 O 3 ), oxide Silicon (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), hafnium dioxide (HfO 2 ), tin oxide (SnO 2 ), ceria (CeO 2 ), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate at least one of them.
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyethylene At least one of alkanone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the present application also provides an electronic device, including the electrochemical device according to any one of the above.
  • the electronic device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-type computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, video recorders , LCD TV, Portable Cleaner, Portable CD Player, Mini CD, Transceiver, Electronic Notepad, Calculator, Memory Card, Portable Recorder, Radio, Backup Power, Motor, Automobile, Motorcycle, Power-assisted Bicycle, Bicycle, Lighting Appliances, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, etc.
  • electronic devices include cell phones that contain lithium-ion batteries.
  • the positive electrode material lithium cobalt oxide (LiCoO 2 ), Super P, and polyvinylidene fluoride were mixed according to the weight ratio of 97:1.4:1.6, N-methylpyrrolidone (NMP) was added, and the system was stirred under the action of a vacuum mixer until the system was uniform.
  • a positive electrode slurry was obtained, wherein the solid content of the positive electrode slurry was 72 wt %; the positive electrode slurry was uniformly coated on the positive electrode current collector aluminum foil; the aluminum foil was dried at 85° C., and then subjected to cold pressing, cutting and slitting. , and dried under vacuum at 85 °C for 4 h to obtain the positive electrode.
  • the negative electrode material artificial graphite and the metal oxide-coated silicon-oxygen negative electrode active material SiOx (0.5 ⁇ x ⁇ 1.5), Super P, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are in a weight ratio of 96.2 :1.5:0.5:1.8 to mix, add deionized water, and obtain negative electrode slurry under the action of a vacuum mixer, wherein the solid content of the negative electrode slurry is 54wt%; the negative electrode slurry is uniformly coated on the negative electrode current collector copper foil; The copper foil was dried at 85°C, then cold-pressed, cut into pieces, and slit, and then dried under vacuum at 120°C for 12 hours to obtain a negative electrode.
  • a conductive layer is included, and a conductive layer with a thickness of 0.3 ⁇ m to 1.5 ⁇ m is firstly coated on the negative electrode current collector, and then a negative electrode active material layer is coated on it after drying.
  • the mass of silicon element in the area of the coated negative electrode material is controlled to be 0.01 mg/cm 2 to 3 mg/cm 2 .
  • ethylene carbonate (EC), propylene carbonate (PC), and chain ester were mixed according to a certain mass ratio, and fluoroethylene carbonate (FEC) was added.
  • FEC fluoroethylene carbonate
  • a non-fluorinated chain ester will also be added; the lithium salt LiPF 6 is added after sufficient stirring, and the electrolyte is obtained after mixing uniformly.
  • the concentration of LiPF 6 was 1.1 mol/L.
  • the content of each component in the electrolyte is the mass percentage calculated based on the total mass of the electrolyte. (The electrolyte contents used in each embodiment and comparative example are shown in Table 1 to Table 5)
  • Polyethylene (PE) with a thickness of 8 ⁇ m is used as the separator.
  • the positive electrode, the separator and the negative electrode in order, so that the separator is placed between the positive electrode and the negative electrode for isolation, and then coil to obtain a bare cell; after welding the tabs, place the bare cell in the outer packaging foil aluminum-plastic
  • the above-prepared electrolyte is injected into the dried bare cell, and after vacuum packaging, standing, and formation (charged to 3.5V with a 0.02C constant current, and then charged to 3.9V with a 0.1C constant current), Through the procedures of shaping and capacity testing, a soft-pack lithium-ion battery (thickness 3.3mm, width 39mm, length 96mm) was obtained.
  • the negative electrode material with a certain coating area Take the negative electrode material with a certain coating area, scrape off the material except the base material, weigh it, add a certain amount of concentrated nitric acid for microwave digestion to obtain a solution, and wash the obtained solution and filter residue for many times and set the volume.
  • the plasma intensity of the silicon element in it is tested by ICP-OES, and the silicon content in the solution is calculated according to the standard curve of the measured element, so as to calculate the amount of silicon element contained in the material; the amount of silicon element Divide by the area of the negative electrode material to obtain the mass of silicon element in the area of the negative electrode material.
  • the negative electrode material with a certain coating area Take the negative electrode material with a certain coating area, scrape off the material except the base material, weigh it, add a certain amount of concentrated nitric acid for microwave digestion to obtain a solution, and wash the obtained solution and filter residue for many times and set the volume.
  • the plasma intensity of the metal elements in it is tested by ICP-OES, and the metal content in the solution is calculated according to the standard curve of the measured elements, so as to calculate the amount of metal elements contained in the material.
  • the formed lithium-ion battery is charged to 4.2V with 1.0C constant current at 35°C, then charged to 4.35V with 0.7C constant current, and then charged to 4.45V with 0.5C constant current, and then charged with constant voltage until the current is 0.05C, after standing for 5min, discharge at 0.5C to 3.0V, so the charge and discharge cycle is 500 times; the first discharge capacity is recorded as D 0 , and the 500th cycle discharge capacity is recorded as D 1 ;
  • Cycle capacity retention (%) D 1 /D 0 ⁇ 100%.
  • Example 1 19% 15% 34% 3% 0.09 54.5% 62
  • Example 2 15% 15% 30% 5% 0.17 57.3% 53
  • Example 3 15% 14% 29% 7% 0.24 64.8% 57
  • Example 4 14% 14% 28% 10% 0.36 76.7% 55
  • Example 5 14% 14% 28% 10.5% 0.38 78.9% 55
  • Example 6 11% 14% 25% 12% 0.48 81.3% 54
  • Example 7 7% 17% twenty four% 14% 0.58 83.5%
  • Example 8 6% 13% 19% 15% 0.79 84.2%
  • Example 9 4% 13% 17% 17% 1.00 87.3% 48
  • Example 10 4% 13% 17% 18% 1.06 87.8%
  • Example 11 6% 12% 18% 20% 1.11 88.1%
  • Example 12 4% 12% 16% twenty two% 1.38 88.4% 57
  • Example 13 0% 11% 11% 25% 2.27 81.5% 54 Comparative Example 1 15% 26% 41%
  • the proportion r2 of SiOx in Examples 1 to 13 and Comparative Examples 1 to 2 is all 15%.
  • the cycle capacity retention rates of Examples 1 to 13 are higher than those of Comparative Examples 1 to 2, and the DC impedances of Examples 1 to 13 are all lower than those of Comparative Examples 1 to 2. From this, it can be seen that when the ratio Z of FEC/(EC+PC) is in the range of 0.05 to 2.5 as shown in Example 1 to Example 13, the cycle performance of the lithium ion battery is better and the DC resistance is lower, while the The Z values of Example 1 and Comparative Example 2 are too small and too large, both of which lead to poor cycle performance and DC resistance of the lithium-ion battery.
  • the Si distribution in Table 2 is the mass of Si per unit coating area on the negative electrode current collector.
  • Example 7 From the data of Example 7, Example 14 to Example 24 and Comparative Example 3 and Comparative Example 4, it can be seen that the cycle capacity of Example 7, Example 14 to Example 24 is maintained compared to Comparative Example 3 and Comparative Example 4 It can be seen that when the mass ratio Z of fluorinated ethylene carbonate and non-fluorinated cyclic carbonate to the mass X of silicon per unit coating area on the negative electrode is in From 0.9 to 2.5, the cycle performance of the lithium-ion battery is higher and the DC resistance is lower. When the value of Z/X is too large (Comparative Example 4) or too small (Comparative Example 3), it is not conducive to the cycle performance and DC resistance of the lithium-ion battery.
  • Example 7 By comparing Example 7, Example 25 to Example 32 in Table 3 with Comparative Example 1, it can be seen (in Table 3, the proportion of SiOx content r2 is all 15%), Example 7, Example 25 to Example Compared with Comparative Example 1, the cycle capacity retention rate of 32 is higher and the DC resistance is lower. It can be seen that when the ratio b/c of the non-fluorinated cyclic ester content b to the chain ester content c is in the range of 0.1 to 1 It is beneficial to improve the cycle performance of lithium-ion batteries and reduce the DC resistance. However, when b/c is greater than 1 (Comparative Example 1), the cycle performance may be degraded and the DC resistance may be increased.
  • Example 7 Al 180 83.5% 56
  • Example 34 Al 1443 85.7% 53
  • Example 35 Al 2942 86.2% 51
  • Example 36 Al 4520 86.4% 52
  • Example 37 Ti 180 83.8% 55
  • Example 38 AI+Ti 180 84.9% 52 Comparative Example 5 / / 72.4% 70
  • Example 7 Example 33 to Example 38 have higher cycle capacity retention rate and lower DC resistance
  • the surface of the silicon-containing material is provided with a protective layer, and the protective layer has a certain amount of metal elements, which can suppress the volume expansion of the silicon-containing material during the cycle and increase the electrical conductivity. Therefore, in some embodiments of the present application, the surface of the silicon-containing material contains a protective layer, and the protective layer has a metal element, the mass ratio of the metal element to the negative electrode active material layer is r1, 0.5ppm ⁇ r1 ⁇ 15000ppm.
  • Examples 39 to 41 have higher cycle capacity retention and lower DC resistance, because the porosity of the negative electrode active material layer in Comparative Example 6 is too high, which affects the negative electrode activity.
  • the electrical conductivity between the particles in the material layer, and the conductivity of the silicon-containing material itself is low, thus further affecting the performance of the lithium ion battery. Insufficient infiltration affects the performance of lithium-ion batteries. Therefore, the porosity of the negative electrode active material layer is defined to be 20% to 30% in some embodiments.

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Abstract

一种电化学装置和电子装置，其中电化学装置包括正极、负极和电解液；电解液，包括：氟代碳酸乙烯酯和非氟代环状碳酸酯，氟代碳酸乙烯酯占所述电解液质量的百分比为a％，非氟代环状碳酸酯占电解液质量的百分比为b％，且0.05≤a/b≤2.5。所述电化学装置具有改善的循环性能并降低直流阻抗。

Description

电化学装置和电子装置
相关申请的交叉引用
本申请基于申请号为：202011448018.X、申请日为：2020年12月09日，名称为“电化学装置和电子装置”的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本申请涉及电化学技术领域，尤其涉及一种电化学装置和电子装置。
背景技术
电化学装置(例如锂离子电池)近年来被广泛应用于手机、笔记本电脑等电子产品中。随着市场对于电子产品轻薄化的追求，对电化学装置的能量密度的要求越来越高。
为了提高电化学装置的能量密度，硅材料受到越来越多的关注，硅材料的作为负极材料的理论容量远高于现有的碳材料，但是硅材料在脱嵌锂的过程中体积变化较大，容易造成负极界面的SEI(solid electrolyte interphase，固体电解质界相)膜破裂，特别是在循环过程中，硅材料不断的进行脱嵌锂，从而造成SEI膜不断的破裂而露出新界面，新界面又会与电解液发生反应，消耗电解液和活性锂，造成循环衰减，并且硅材料的导电性较差，使用硅材料会导致电化学装置的直流阻抗增加，因此如何提高硅材料体系的电化学装置的导电性是需要解决的问题。
发明内容
本申请提出一种电化学装置，包括正极、负极和电解液；所述电解液，包括：氟代碳酸乙烯酯和非氟代环状碳酸酯，氟代碳酸乙烯酯占电解液质量的百分比为a％，非氟代环状碳酸酯占所述电解液质量的百分比为b％，且0.05≤a/b≤2.5。一些实施例中，通过限定氟代碳酸乙烯酯和非氟代环状碳酸酯之间的比例，能够确保氟代碳酸乙烯酯相比于非氟代环状碳酸酯不会过多而 导致电化学装置的直流阻抗增加，同时确保不会过少而导致电化学装置的循环性能降低，使得电化学装置同时具有较好的循环性能和较低的直流阻抗。
在一些实施例中，3≤a≤25，在一些实施例中，11≤b≤34，在一些实施例中，0.09≤a/b≤2.27。一些实施例中，负极材料在循环过程中可能因为脱嵌锂而发生体积膨胀，造成负极材料的SEI膜破裂，而氟代碳酸乙烯酯可以在电化学装置的循环过程中不断对负极材料的SEI膜进行修复，从而改善电化学装置的循环性能，但是氟代碳酸乙烯酯本身的黏度较大，如果加入的氟代碳酸乙烯酯的量过多，可能导致电解液的电导率下降，因此通过限定其含量从而改善循环性能的同时防止电导率下降。
在一些实施例中，负极包括：负极集流体和位于负极集流体的负极活性物质层，负极活性物质层中包括负极材料，负极材料包括含硅材料，负极集流体上每单位涂布面积中硅元素的质量为X mg/cm 2，且0.1≤X≤1.3，在一些实施例中，0.2≤X≤1.3。电化学装置的负极材料中包括含硅材料，可以提高电化学装置负极材料的比容量；由于硅材料在循环过程中的体积膨胀较为明显，所以通过限定负极集流体上每单位涂布面积中硅元素的质量从而限制因为循环导致的负极材料的膨胀。
在一些实施例中，a/b＝Z，且0.76≤Z/X≤2.5，硅含量、氟代碳酸乙烯酯和非氟代环状碳酸酯含量相匹配，从而能够在改善SEI膜稳定性的同时，防止循环性能下降和直流阻抗增加。
在一些实施例中，电解液还包括：非氟代链状酯，非氟代链状酯占电解液质量的百分比为c％，且0.1≤b/c≤1，在一些实施例中，0.25≤b/c≤0.81，非氟代环状碳酸酯包括：碳酸乙烯酯或碳酸丙烯酯中的至少一种。非氟代链状酯的黏度较低，在电解液中加入非氟代链状酯有利于降低电解液整体的黏度，但是非氟代链状酯的相对介电常数较低，加入过多的非氟代链状酯会导致电解液整体的相对介电常数降低，通过限定b/c，在降低电解液的黏度的同时，保证电解液具有足够高的介电常数。
在一些实施例中，负极还包括：位于负极集流体和负极活性物质层之间的导电层；导电层的厚度d满足：0.3μm≤d≤1.5μm。含硅材料在充放电过程中体积膨胀较大，可能因为膨胀导致负极活性物质层从负极集流体上脱离，因此在负极活性物质层与负极集流体之间设置导电层，当电解液中氟代碳酸 乙烯酯和非氟代环状碳酸酯质量比满足合适条件时与导电层的厚度d相匹配，能够缓冲负极活性物质层膨胀引起的变形，防止与负极集流体脱离，当d小于0.3μm时可能因为导电层过薄导致缓冲膨胀变形的效果较差，当d大于1.5μm时可能导致电化学装置的体积能量密度降低。
在一些实施例中，含硅材料包括：SiO x、硅碳化合物或硅单质中的至少一种，其中0.5≤x≤1.5；含硅材料的表面具有保护层，保护层中含有金属元素；金属元素包括：Al、Ti、Mn、V、Cr、Co或Zr中的至少一种。通过保护层可以限制含硅材料的体积膨胀，其中含有的金属元素能够提高保护层的电导率。
在一些实施例中，金属元素与负极活性物质层的质量比为r1，0.5ppm≤r1≤15000ppm。在一些实施例中，180ppm≤r1≤4520ppm，此时电化学装置的循环性能较好且直流阻抗较小。
在一些实施例中，其中，含硅材料与负极活性物质层的质量比为r2，0.5％≤r2≤85％。当r2小于0.5％时，含硅材料对于比容量的提升的效果不明显，当r2大于85％时，由于含硅材料过多负极活性物质层在充放电过程中的体积膨胀过大，可能导致电化学装置稳定性差，造成直流阻抗增加。
在一些实施例中，其中，负极活性物质层的孔隙率为20％至30％。当孔隙率小于20％时，可能减少电解液与负极材料之间的接触导致电解液对负极材料的浸润不足，并且当含硅材料膨胀时因为孔隙率过低造成负极活性物质层的内应力增加，而当孔隙率大于30％时，可能因为负极材料的颗粒之间的间隙过大造成负极活性物质层整体的导电性降低，从而造成直流阻抗增加。
本申请还提出一种电子装置，包括上述任一项的电化学装置。
本申请实施例提供的一种电化学装置，包括正极、负极和电解液；电解液，包括：氟代碳酸乙烯酯和非氟代环状碳酸酯，氟代碳酸乙烯酯占电解液质量的百分比为a％，非氟代环状碳酸酯占电解液质量的百分比为b％，且0.05≤a/b≤2.5。本申请实施例中提出的电化学装置(特别是含硅材料的电化学装置)具有改善的循环性能并降低直流阻抗。
具体实施方式
下面将更详细地描述本申请的实施例。虽然显示了本申请的某些实施例，然而应当理解的是，本申请可以通过各种形式来实现，而且不应该被解释为限于这里阐述的实施例，相反提供这些实施例是为了更加透彻和完整地理解本申请。应当理解的是，本申请的实施例仅用于示例性作用，并非用于限制本申请的保护范围。
为了至少部分解决上述问题，本申请的一些实施例中提出一种电化学装置，包括正极、负极和电解液；电解液，包括：氟代碳酸乙烯酯和非氟代环状碳酸酯，氟代碳酸乙烯酯占电解液质量的百分比为a％，非氟代环状碳酸酯占电解液质量的百分比为b％，且0.05≤a/b≤2.5。一些实施例中非氟代环状碳酸酯包括：碳酸乙烯酯或碳酸丙烯酯中的至少一种。在本申请一些实施例中，氟代碳酸乙烯酯能够修复负极材料的SEI膜改善电化学装置的循环性能，但其黏度较大，加入大量的氟代碳酸乙烯酯会导致电解液的导电率下降，而非氟代环状碳酸酯具有良好的导电性，且考虑到氟代碳酸乙烯酯的介电常数高，可降低非氟代环状碳酸酯，从而氟代碳酸乙烯酯与非氟代环状碳酸酯的含量需要进行平衡，因此，为了在保护负极材料的SEI膜的同时防止电解液的导电率下降，需要限定氟代碳酸乙烯酯和非氟代环状碳酸酯之间的比例，确保氟代碳酸乙烯酯相比于非氟代环状碳酸酯不会过多而导致电化学装置的直流阻抗增加，同时确保氟代碳酸乙烯酯相比于非氟代环状碳酸酯不会过少而导致电化学装置的循环性能降低。一些实施例中，0.05≤a/b≤2.5时，电化学装置同时具有较好的循环性能和较低的直流阻抗。
在本申请的一些实施例中，3≤a≤25，优选的，10.5≤a≤25，11≤b≤34，且0.09≤a/b≤2.27。在本申请的一些实施例中，负极材料，特别是含硅材料的负极材料，在循环过程中可能因为脱嵌锂而发生体积膨胀，造成负极材料的SEI膜破裂，而氟代碳酸乙烯酯可以在电化学装置的循环过程中不断对负极材料的SEI膜进行修复，从而改善电化学装置的循环性能，因此一些实施例中在电解液中加入一定量的氟代碳酸乙烯酯；但是氟代碳酸乙烯酯本身的黏度较大，如果加入的氟代碳酸乙烯酯的量过多，可能导致电解液的电导率下降，因此，在本申请一些实施例中限定10.5≤a≤25。
在本申请的一些实施例中，负极包括：负极集流体和位于负极集流体的负极活性物质层，负极活性物质层包括负极材料，负极材料包括含硅材料， 负极集流体上每单位涂布面积中硅元素的质量为X mg/cm 2，且0.1≤X≤1.3，优选的，0.2≤X≤1.3。本申请中负极活性物质层可以设置在负极集流体的一面或两面上，如果负极集流体两面上都设置有负极活性物质层，则负极集流体上单位涂布面积中硅元素的质量是指负极集流体的一个表面上单位涂布面积中的硅元素的质量。本申请的实施例中，电化学装置的负极材料中包括含硅材料，因此可以提高电化学装置负极材料的比容量；由于硅材料在循环过程中的体积膨胀较为明显，所以通过限定负极集流体上每单位涂布面积中硅元素的质量X mg/cm 2满足0.1≤X≤1.3以限定含硅材料的量，从而限制因为循环导致的负极材料的膨胀。
在本申请的一些实施例中，a/b＝Z，且0.76≤Z/X≤2.5。一些实施例中，负极材料膨胀导致的SEI膜破裂的程度与含硅材料的量相关，即X越大修复SEI膜所需要的氟代碳酸乙烯酯的量越多，因此0.9≤Z/X从而保证氟代碳酸乙烯酯的量足够修复负极材料的SEI膜，同时限定Z/X≤2.5从而防止氟代碳酸乙烯酯的量过多导致电化学装置的循环性能下降和直流阻抗增加。
在本申请的一些实施例中，电解液还包括：非氟代链状酯，非氟代链状酯占电解液质量的百分比为c％，且0.1≤b/c≤1，优选的，0.25≤b/c≤0.81。非氟代链状酯的黏度较低，在电解液中加入非氟代链状酯有利于降低电解液整体的黏度，但是非氟代链状酯的相对介电常数较低，加入过多的非氟代链状酯会导致电解液整体的相对介电常数降低，而为了保证电解液中锂盐的溶解和离子传导，电解液必须具有足够大的极性，只有相对介电常数足够高的电解液才能降低正负极之间离子强烈的静电吸引力，使离子能离解为自由离子，因此本申请中控制0.1≤b/c≤1，优选的0.25≤b/c≤0.81，在降低电解液的黏度的同时，保证电解液具有足够高的介电常数。
在本申请的一些实施例中，非氟代链状酯包括：碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸丙乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸异丙酯、乙酸丁酯、乙酸仲丁酯、乙酸异丁酯、乙酸叔丁酯、丙酸甲酯、丙酸丙酯、丙酸异丙酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、异丁酸甲酯、异丁酸乙酯、戊酸甲酯或戊酸乙酯中的至少一种。
在本申请的一些实施例中，负极还包括：位于负极集流体和负极活性物质层之间的导电层；导电层的厚度d满足：0.3μm≤d≤1.5μm。含硅材料在充 放电过程中体积膨胀较大，可能因为膨胀导致负极活性物质层从负极集流体上脱离，因此在负极活性物质层与负极集流体之间设置导电层，导电层能够缓冲负极活性物质层膨胀引起的变形，防止与负极集流体脱离，当d小于0.3μm时可能因为导电层过薄导致缓冲膨胀变形的效果较差，当d大于1.5μm时可能导致电化学装置的体积能量密度降低。因此本申请中限定了0.3μm≤d≤1.5μm。
在本申请的一些实施例中，导电层的导电材料可以包括任何导电材料，只要它不引起化学变化。导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维、碳纳米管、石墨烯等)、基于金属的材料(例如，金属粉、金属纤维等，例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
在本申请的一些实施例中，含硅材料包括：SiOx、硅碳化合物或硅单质中的至少一种，其中0.5≤x≤1.5。含硅材料的表面具有保护层，保护层中含有金属元素；金属元素包括：Al、Ti、Mn、V、Cr、Co或Zr中的至少一种。通过在含硅材料表面设置保护层，能够抑制含硅材料在充放电过程中的体积膨胀，并且保护层中的金属离子能够提高含硅材料的导电性，从而降低直流阻抗。
在本申请的一些实施例中，金属元素与负极活性物质层的质量比为r1，0.5ppm≤r1≤15000ppm。本申请的一些实施例中，当0.5ppm≤r1≤15000ppm时，电化学装置的循环性能较好，且直流阻抗较小。优选的，180ppm≤r1≤4520ppm。
一些实施例中，含硅材料与负极活性材料层的质量比为r2，0.5％≤r2≤85％。当r2小于0.5％时，含硅材料对于比容量的提升的效果不明显，当r2大于85％时，由于含硅材料过多负极活性物质层在充放电过程中的体积膨胀过大，可能导致电化学装置稳定性差并造成直流阻抗增加。
在本申请的一些实施例中，负极活性物质层的孔隙率为20％至30％。当孔隙率小于20％时，可能减少电解液与负极材料之间的接触导致电解液对负极材料的浸润不足，并且当含硅材料膨胀时因为孔隙率过低造成负极活性物质层的内应力增加，而当孔隙率大于30％时，可能因为负极材料的颗粒之间的间隙过大造成负极活性物质层整体的导电性降低，从而造成直流阻抗增加。
在本申请的一些实施例中，正极包括正极集流体和正极活性物质层，正极活性物质层中包括正极材料。正极材料例如可以是钴酸锂、镍钴锰酸锂、磷酸铁锂等。
在本申请的一些示例中，上述电化学装置的正极中可以加有导电剂或粘结剂，在本申请的一些示例中，导电剂包括碳材料，碳材料可以包括导电炭黑、石墨、石墨烯、碳纳米管、碳纤维或炭黑中的至少一种。粘结剂可以包括聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、苯乙烯-丙烯酸酯共聚物、苯乙烯-丁二烯共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素纳、聚醋酸乙烯酯、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。
在本申请的一些实施例中，电解液中还包括：1,3-丙烷磺酸内酯(PS)、1,4丁烷磺内酯、碳酸亚乙烯酯(VC)或硫酸乙烯酯(DTD)中的至少一种。
在本申请的一些实施例中，电解液包括锂盐。锂盐包括：无机锂盐，例如LiClO 4、LiAsF 6、LiPF 6、LiBF 4、LiSbF 6、LiSO 3F、LiN(FSO 2) 2等；含氟有机锂盐，例如LiCF 3SO 3、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,3-六氟丙烷二磺酰亚胺锂、环状1,2-四氟乙烷二磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)、LiC(CF 3SO 2) 3、LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 2(CF 3) 2、LiBF 2(C 2F 5) 2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2；含二羧酸配合物锂盐，例如双(草酸根合)硼酸锂(LiBOB)、二氟草酸根合硼酸锂(LiDFOB)等。另外，上述锂盐可以单独使用一种，也可以同时使用两种或两种以上。锂盐的浓度可以在0.8mol/L至3mol/L的范围内。
在一些示例中，正极和负极之间设置有隔离膜。隔离膜包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。在一些可选的示例中，在隔离膜表面涂覆无机或有机涂层以增强电芯的硬度或提升隔离膜与正负极界面的粘附性。
在一些示例中，隔离膜表面还可包括多孔层，多孔层设置在隔离膜的至少一个表面上，多孔层包括无机颗粒和粘结剂，无机颗粒选自氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、 氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素纳、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。
本申请还提出一种电子装置，包括上述中任一项的电化学装置。本申请的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些示例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池等。例如，电子装置包括含有锂离子电池的手机。
为使本申请的目的、技术方案和优点更加清楚，下面将结合本申请实施例和对比例，对本申请的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请提供的技术方案及所给出的实施例，本领域技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。在以下实施例和对比例中电化学装置为锂离子电池。
(1)正极制备
将正极材料钴酸锂(LiCoO 2)、Super P、聚偏二氟乙烯按照重量比97:1.4:1.6进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌至体系均匀，获得正极浆料，其中正极浆料的固含量为72wt％；将正极浆料均匀涂覆于正极集流体铝箔上；将铝箔在85℃下烘干，然后经过冷压、裁片、分切后，在85℃的真空条件下干燥4h，得到正极。
(2)负极制备
将负极材料人造石墨和包覆有金属氧化物的硅氧负极活性材料SiOx(0.5≤x≤1.5)、Super P、羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按照重量比96.2:1.5:0.5:1.8进行混合，加入去离子水，在真空搅拌机作用下 获得负极浆料，其中负极浆料的固含量为54wt％；将负极浆料均匀涂覆在负极集流体铜箔上；将铜箔在85℃下烘干，然后经过冷压、裁片、分切后，在120℃的真空条件下干燥12h，得到负极。部分实施例中，含有导电层，先在负极集流体上涂布0.3μm至1.5μm厚度的导电层，待其干后在其上面涂布负极活性物质层。控制单位涂布负极材料面积中硅元素的质量为0.01mg/cm 2至3mg/cm 2。
(3)电解液制备
在干燥的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯脂(PC)、链状酯按照一定质量比进行混合，并加入氟代碳酸乙烯酯(FEC)，部分实施例中还会加入非氟代链状酯；充分搅拌后加入锂盐LiPF 6，混合均匀后获得电解液。其中，LiPF 6的浓度为1.1mol/L。在各个表中，电解液中各个成分的含量为基于电解液的总质量计算得到的质量百分数。(各个实施例和对比例采用的电解液含量如表1至表5所示)
(4)隔离膜的制备
选用8μm厚的聚乙烯(PE)作为隔离膜。
(5)锂离子电池的制备
将正极、隔离膜、负极按顺序叠好，使隔离膜处于正极、负极之间起到隔离的作用，然后卷绕得到裸电芯；焊接极耳后将裸电芯置于外包装箔铝塑膜中，将上述制备好的电解液注入到干燥后的裸电芯中，经过真空封装、静置、化成(0.02C恒流充电到3.5V，再以0.1C恒流充电到3.9V)、整形、容量测试等工序，获得软包锂离子电池(厚度3.3mm、宽度39mm、长度96mm)。
(6)每单位涂布面积中负极材料硅元素的质量测定：
取含有一定涂布面积的负极材料，刮下除基材外的材料，称重，加入一定量的浓硝酸进行微波消解后得溶液，并将所得到的溶液和滤渣进行多次洗涤并定容到一定的体积，通过ICP-OES测试其中的硅元素的等离子体强度，根据所测元素的标准曲线计算出溶液中硅含量，从而计算出材料中所含的硅元素的量；硅元素的量除以负极材料的面积得到负极材料面积中硅元素的质量。
(7)含硅材料保护层中金属元素的测定：
取含有一定涂布面积的负极材料，刮下除基材外的材料，称重，加入一定量的浓硝酸进行微波消解后得溶液，并将所得到的溶液和滤渣进行多次洗涤并定容到一定的体积，通过ICP-OES测试其中的金属元素的等离子体强度，根据所测元素的标准曲线计算出溶液中金属含量，从而计算出材料中所含金属元素的量。
(8)循环测试：
将化成后的锂离子电池，在35℃下以1.0C恒流充电4.2V，再以0.7C恒流充电至4.35V，再以0.5C恒流充电至4.45V，然后恒压充电至电流为0.05C，静置5min后，以0.5C放电至3.0V，如此充放电循环500次；第一次放电容量记为D 0，第500次循环放电容量记为D 1；
循环容量保持率(％)＝D 1/D 0×100％。
(9)直流阻抗测试(DCR)：
以0.5C将锂离子电池恒流充电至3.95V，再恒压充电至0.05C；静置30min；以0.1C放电10s(0.1s取点一次，记录对应电压值U 1)，以1C放电360s(0.1s取点一次，记录对应电压值U 2)。重复充放电步骤5次。其中，“1C”是在1小时内将电池容量完全放完的电流值。
按如下公式计算得出DCR：DCR＝(U 2-U 1)/(1C-0.1C)。
表1.实施例1至实施例13以及对比例1至对比例2的电解液以及测试结果
项目 EC PC EC+PC FEC FEC/(EC+PC)比例a/b 循环容量保持率 DCR(mΩ)
实施例1 19％ 15％ 34％ 3％ 0.09 54.5％ 62
实施例2 15％ 15％ 30％ 5％ 0.17 57.3％ 53
实施例3 15％ 14％ 29％ 7％ 0.24 64.8％ 57
实施例4 14％ 14％ 28％ 10％ 0.36 76.7％ 55
实施例5 14％ 14％ 28％ 10.5％ 0.38 78.9％ 55
实施例6 11％ 14％ 25％ 12％ 0.48 81.3％ 54
实施例7 7％ 17％ 24％ 14％ 0.58 83.5％ 56
实施例8 6％ 13％ 19％ 15％ 0.79 84.2％ 49
实施例9 4％ 13％ 17％ 17％ 1.00 87.3％ 48
实施例10 4％ 13％ 17％ 18％ 1.06 87.8％ 56
实施例11 6％ 12％ 18％ 20％ 1.11 88.1％ 56
实施例12 4％ 12％ 16％ 22％ 1.38 88.4％ 57
实施例13 0％ 11％ 11％ 25％ 2.27 81.5％ 54
对比例1 15％ 26％ 41％ 1％ 0.02 32.1％ 85
对比例2 7％ 7％ 14％ 40％ 2.86 52.3％ 93
如表1所示，其中，实施例1至实施例13，以及对比例1至对比例2中SiOx占比含量r2均为15％。实施例1至实施例13的循环容量保持率均高于对比例1至对比例2，且实施例1至实施例13的直流阻抗均低于对比例1至对比例2。由此可知，在FEC/(EC+PC)的比值Z在实施例1至实施例13中所示的0.05至2.5范围内时，锂离子电池的循环性能较好且直流阻抗较小，而对比例1和对比例2的Z值过小和过大，均导致锂离子电池的循环性能和直流阻抗较差。
表2.实施例7、实施例14至实施例24以及对比例3至对比例4的电解液以及测试结果
Figure PCTCN2021104025-appb-000001
注：表2中Si分布量为负极集流体上每单位涂布面积中硅元素的质量。
从实施例7、实施例14至实施例24与对比例3和对比例4的数据可以看出，实施例7、实施例14至实施例24相比于对比例3和对比例4循环容量保持率较高，且直流阻抗较低，由此可见，当氟代碳酸乙烯酯与非氟代环状碳酸酯的质量比Z，与硅元素在负极上单位涂布面积中的质量X的比值在0.9至2.5时，锂离子电池的循环性能较高且直流阻抗较小。当Z/X的数值过大(对比例4)或过小(对比例3)时，都不利于锂离子电池的循环性能和直流阻抗。
表3.实施例7、实施例25至实施例32以及对比例1的电解液以及测试结果
Figure PCTCN2021104025-appb-000002
通过表3的实施例7、实施例25至实施例32与对比例1对比，可以看出(表3中，SiOx占比含量r2均为15％)，实施例7、实施例25至实施例32相比于对比例1的循环容量保持率较高，且直流阻抗较低，由此可见，当非氟代环状酯含量b与链状酯含量c的比值b/c在0.1至1范围内 时，有利于改善锂离子电池的循环性能并减低直流阻抗。而当b/c大于1时(对比例1)则可能导致循环性能下降并增大直流阻抗。
表4.实施例7、实施例33至实施例38以及对比例5的电解液以及测试结果。
项目 保护层中金属元素 保护层中金属元素含量(ppm) 循环容量保持率 DCR(mΩ)
实施例7 Al 180 83.5％ 56
实施例33 Al 720 84.6％ 54
实施例34 Al 1443 85.7％ 53
实施例35 Al 2942 86.2％ 51
实施例36 Al 4520 86.4％ 52
实施例37 Ti 180 83.8％ 55
实施例38 AI+Ti 180 84.9％ 52
对比例5 / / 72.4％ 70
其中，实施例33至实施例38以及对比例5中的FEC、EC和PC的质量百分比与表1实施例7中的FEC、EC和PC的质量的百分比相等。
如表4所示(表4中，SiOx占比含量r2均为15％)，实施例7、实施例33至实施例38相比于对比例5循环容量保持率较高且直流阻抗较小，这是因为实施例7、实施例33至实施例38中含硅材料表面设置有保护层，且保护层中具有一定量的金属元素，能够抑制含硅材料在循环过程中的体积膨胀并增加导电性，因此本申请一些实施例中设置含硅材料的表面含有保护层，且保护层中具有的金属元素，金属元素与负极活性物质层的质量比为r1，0.5ppm≤r1≤15000ppm。
表5 实施例39至实施例41以及对比例6、对比例7的电解液以及测试结果
Figure PCTCN2021104025-appb-000003
如表5所示(表5中，SiOx占比含量r2均为15％)，在实施例39至实施例41，以及对比例6和对比例7中，EC、PC、非氟代链状酯和FEC占其电解液质量的百分比相等，其中，EC占电解液质量的百分比为7％，PC占电解液质量的百分比为17％，非氟代链状酯占电解液质量的百分比为43％， FEC占电解液质量的百分比为14％。实施例39至实施例41相比于对比例6和对比例7，循环容量保持率较高且直流阻抗较小，这是因为对比例6中负极活性物质层的孔隙率过高，影响负极活性物质层中颗粒之间的电传导，且含硅材料本身的电导率较低，因此进一步影响锂离子电池性能，对比例7中负极活性物质层的孔隙率太小，导致电解液对负极材料的浸润不足，影响锂离子电池性能。因此在一些实施例中限定负极活性物质层的孔隙率为20％至30％。
以上描述仅为本申请的较佳实施例以及对所运用技术原理的说明。本领域技术人员应当理解，本申请中所涉及的公开范围，并不限于上述技术特征的特定组合而成的技术方案，同时也应涵盖在不脱离上述公开构思的情况下，由上述技术特征或其等同特征进行任意组合而形成的其它技术方案。例如上述特征与本申请中公开的(但不限于)具有类似功能的技术特征进行互相替换而形成的技术方案。

Claims (17)

  1. 一种电化学装置，包括正极、负极和电解液；
    所述电解液，包括：氟代碳酸乙烯酯和非氟代环状碳酸酯，所述氟代碳酸乙烯酯占所述电解液质量的百分比为a％，所述非氟代环状碳酸酯占所述电解液质量的百分比为b％，且0.05≤a/b≤2.5。
  2. 根据权利要求1所述的电化学装置，其特征在于，3≤a≤25。
  3. 根据权利要求1所述的电化学装置，其特征在于，11≤b≤34。
  4. 根据权利要求1所述的电化学装置，其特征在于，0.09≤a/b≤2.27。
  5. 根据权利要求1所述的电化学装置，其特征在于，所述电解液还包括：非氟代链状酯，所述非氟代链状酯占所述电解液质量的百分比为c％，且0.1≤b/c≤1。
  6. 根据权利要求5所述的电化学装置，其特征在于，0.25≤b/c≤0.81。
  7. 根据权利要求1所述的电化学装置，其特征在于，所述非氟代环状碳酸酯包括碳酸乙烯酯或碳酸丙烯酯中的至少一种。
  8. 根据权利要求1所述的电化学装置，其特征在于，所述负极还包括：位于所述负极集流体和所述负极活性物质层之间的导电层；所述导电层的厚度d满足：0.3μm≤d≤1.5μm。
  9. 根据权利要求1所述的电化学装置，其特征在于，所述负极包括：负极集流体和位于所述负极集流体的负极活性物质层，所述负极活性物质层包括负极材料，所述负极材料包括含硅材料，所述负极集流体上每单位面积中硅元素的质量为X mg/cm 2，且0.1≤X≤1.3。
  10. 根据权利要求9所述的电化学装置，其特征在于，0.2≤X≤1.3。
  11. 根据权利要求9所述的电化学装置，其特征在于，a/b＝Z，且0.76≤Z/X≤2.5。
  12. 根据权利要求9所述的电化学装置，其特征在于，所述含硅材料与所述负极活性物质层的质量比为r2，0.5％≤r2≤85％。
  13. 根据权利要求9所述的电化学装置，其特征在于，所述负极活性物质层的孔隙率为20％至30％。
  14. 根据权利要求9所述的电化学装置，其特征在于，所述含硅材料包括：SiO x、硅碳化合物或硅单质中的至少一种，其中0.5≤x≤1.5；所述含硅材料的表面具有保护层，所述保护层中含有金属元素；所述金属元素包括：Al、Ti、Mn、V、Cr、Co或Zr中的至少一种。
  15. 根据权利要求14所述的电化学装置，其特征在于，所述金属元素与所述负极活性物质层的质量比为r1，0.5ppm≤r1≤15000ppm。
  16. 根据权利要求14所述的电化学装置，其特征在于，所述金属元素与所述负极活性物质层的质量比为r1，180ppm≤r1≤4520ppm。
  17. 一种电子装置，其特征在于，包括权利要求1至16任一项所述的电化学装置。
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