WO2022218144A1 - 一种锂离子电池 - Google Patents

一种锂离子电池 Download PDF

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WO2022218144A1
WO2022218144A1 PCT/CN2022/083553 CN2022083553W WO2022218144A1 WO 2022218144 A1 WO2022218144 A1 WO 2022218144A1 CN 2022083553 W CN2022083553 W CN 2022083553W WO 2022218144 A1 WO2022218144 A1 WO 2022218144A1
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cyclic
group
silicon
groups
structural formula
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PCT/CN2022/083553
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English (en)
French (fr)
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钱韫娴
胡时光
向晓霞
林雄贵
孙桂岩
曹朝伟
邓永红
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深圳新宙邦科技股份有限公司
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Publication of WO2022218144A1 publication Critical patent/WO2022218144A1/zh

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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
    • H01M10/052—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
    • 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
    • H01M10/056—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
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • 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
    • 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 invention belongs to the technical field of battery materials, in particular to a lithium ion battery.
  • Lithium-ion batteries are widely used in the fields of 3C digital equipment and new energy vehicles due to their high energy density, long cycle life, low self-discharge rate, and environmental protection.
  • one of the directions is to use high-energy-density anode active materials.
  • silicon-based anode materials have become an important direction for improving the energy density of lithium-ion batteries because of their high theoretical specific capacity (4200mAh/g), far exceeding the theoretical specific capacity of graphite anodes (372mAh/g).
  • the silicon-based anode has a large volume effect ( ⁇ 300%) during the cycling process, which makes the solid electrolyte interface film on the surface of the silicon-based anode continue to rupture and regenerate during the battery cycle, resulting in the consumption of electrolyte and active lithium. loss, the interface impedance increases, thereby deteriorating the cycling performance.
  • a large amount of reducing gas will be generated due to side reactions, which will cause the battery to swell and deteriorate the cycle performance sharply. Security risks.
  • the technical problem solved by the present invention is to provide a lithium ion battery with excellent cycle performance in view of the problems of gas swelling and impedance increase in the existing lithium ion battery during the cycle.
  • the present invention provides a lithium ion battery, comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, characterized in that the negative electrode comprises a negative electrode active material, the negative electrode active material contains a silicon-based material, and the silicon-based material contains a silicon-based material.
  • the mass percentage of silicon element in the negative electrode active material is 2% to 50%;
  • the non-aqueous electrolyte includes a solvent, an electrolyte salt and an additive, and the additive includes at least one of the compounds shown in structural formula 1:
  • A, B and C are each independently selected from the group consisting of cyclic carbonate group, cyclic sulfate group, cyclic sulfite group, cyclic sulfonate group, cyclic sulfone group, cyclic sulfoxide group, A cyclic carboxylate group or a cyclic acid anhydride group; D and E are each independently selected from a single bond, or a group containing a hydrocarbylene group, an ether bond, a sulfur-oxygen double bond or a carbon-oxygen double bond;
  • the total mass of the non-aqueous electrolyte is 100%, and the addition amount of the compound represented by the structural formula 1 is 0.01-5.0%.
  • A, B, and C independently contain a cyclic carbonate group, a cyclic sulfate group, a cyclic sulfite group, a cyclic sulfonate group, a cyclic sulfone group, and a cyclic sulfoxide group.
  • the number of cyclic carboxylate groups and cyclic acid anhydride groups is 1 to 5, and A, B, C cyclic carbonate groups, cyclic sulfate groups, cyclic sulfite groups, cyclic sulfonate groups
  • the total number of cyclic sulfone group, cyclic sulfone group, cyclic sulfoxide group, cyclic carboxylate group and cyclic acid anhydride group is less than or equal to 10.
  • a and C are independently selected from the groups shown in structural formula 2:
  • n is selected from an integer from 0 to 4
  • R 1 is selected from hydrogen, halogen, C1-C5 hydrocarbon group or halogenated hydrocarbon group
  • R 2 , R 3 , R 4 , R 5 , R 6 , R 7 are independently selected from each other From C1-C3 alkylene group, C1-C3 alkoxy group, oxygen atom
  • At least one of R 2 , R 3 and R 4 is selected from And at least one of R 2 , R 3 and R 4 is selected from oxygen atoms
  • at least one of R 5 , R 6 and R 7 is selected from And at least one of R 5 , R 6 and R 7 is selected from And at least one of R 5 , R 6 and R 7 is selected from oxygen atoms.
  • B is selected from the group shown in structural formula 3:
  • m is selected from an integer of 1 to 4
  • R 8 , R 9 and R 10 are each independently selected from C1-C3 hydrocarbylene, C1-C3 alkoxy, oxygen atom, At least one of R 8 , R 9 and R 10 is selected from And at least one of R 8 , R 9 and R 10 is selected from oxygen atoms.
  • D and E are each independently selected from the groups shown in structural formula 4:
  • z is selected from an integer from 0 to 4
  • R 11 and R 13 are each independently selected from a single bond or a C1-C5 hydrocarbylene group
  • R 12 is selected from a single bond
  • D and E are each independently selected from single bonds or C1-C5 alkylene groups
  • A, B, and C are each independently selected from substituted or unsubstituted cyclic carbonate groups, cyclic sulfate groups, cyclic sulfite group, cyclic sulfonate group, cyclic sulfone group, cyclic sulfoxide group, cyclic carboxylate group or cyclic acid anhydride group;
  • the substituent when A, B or C is substituted, is selected from halogen, hydrocarbyl or halogenated hydrocarbyl, more preferably, when A, B or C is substituted, the substituent is selected from halogen, alkyl or haloalkyl.
  • a and C are the same as each other, A and B are the same or different from each other, and D and E are the same as each other.
  • the compound shown in the structural formula 1 is selected from one or more of the following compounds:
  • the above substances satisfy: 2 ⁇ T ⁇ 10, and 0.01 ⁇ W ⁇ 3; or 10 ⁇ T ⁇ 50, and 0.05 ⁇ W ⁇ 5.
  • the silicon-based material is selected from at least one of silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials.
  • a silicon-based material is used as the negative electrode material, and a lithium ion battery with high energy density can be prepared.
  • the compound can not only improve the energy density, but also significantly improve the battery cycle inflation and impedance increase, reduce the generation of gas during the battery cycle, and maintain a significant increase in the cycle capacity; the inventors have found through a large number of experiments that the battery cycle performance is not
  • the increase in the content of the compound represented by the structural formula 1 shows a linear improvement.
  • the improvement of the battery performance of the compound represented by the structural formula 1 is related to the mass ratio of the silicon element to the negative electrode active material. When the mass ratio of silicon to the negative electrode active material is 2% to 50% %, when the addition amount of the compound represented by the structural formula 1 is 0.01-5.0%, the cycle performance of the battery is significantly improved.
  • the embodiment of the present invention provides a lithium ion battery, including a positive electrode, a negative electrode and a non-aqueous electrolyte, the negative electrode includes a negative electrode active material, the negative electrode active material contains a silicon-based material, and the silicon element in the silicon-based material is The mass percentage of the negative electrode active material is 2% to 50%; the non-aqueous electrolyte includes a solvent, an electrolyte salt and an additive, and the additive includes at least one of the compounds shown in structural formula 1:
  • A, B and C are each independently selected from the group consisting of cyclic carbonate group, cyclic sulfate group, cyclic sulfite group, cyclic sulfonate group, cyclic sulfone group, cyclic sulfoxide group, A cyclic carboxylate group or a cyclic acid anhydride group; D and E are each independently selected from a single bond, or a group containing a hydrocarbylene group, an ether bond, a sulfur-oxygen double bond or a carbon-oxygen double bond;
  • the total mass of the non-aqueous electrolyte is 100%, and the addition amount of the compound represented by the structural formula 1 is 0.01-5.0%.
  • the lithium ion battery provided by the present invention, on the basis of the silicon-based negative electrode material, by adding the compound represented by the structural formula 1 into the non-aqueous electrolyte, not only a lithium ion battery with high energy density can be prepared, but also a significant improvement can be achieved. Due to the problems of battery cycle inflation and increased impedance, the generation of gas during the battery cycle is reduced, and the cycle capacity is maintained significantly improved; however, it is difficult to achieve a better improvement in other battery systems. The inventor found through a large number of experiments that, The cycle performance of the battery is not linearly improved with the increase in the content of the compound represented by the structural formula 1.
  • the improvement of the battery performance by the compound represented by the structural formula 1 is related to the mass ratio of the silicon element to the negative electrode active material.
  • the silicon element accounts for the mass ratio of the negative electrode active material
  • the addition amount of the compound represented by the structural formula 1 is 0.01 to 5.0%, the battery performance is significantly improved.
  • the compound represented by the structural formula 1 when the silicon content is between 2% and 50%, the compound represented by the structural formula 1 is applied to the silicon-based negative electrode battery.
  • the additive Reductive decomposition occurs on the surface of the silicon-based negative electrode to form an interfacial film, and the organic components in the interfacial film are complexed with silicon elements in a certain proportion, which effectively inhibits the volume effect of the silicon-containing negative electrode during the charging and discharging process, and improves the cyclic inflation and cycling.
  • the capacity remains significantly improved.
  • the silicon content is more than 50%, adding the compound represented by structural formula 1 cannot effectively improve the cycle.
  • A, B, and C each independently contain a cyclic carbonate group, a cyclic sulfate group, a cyclic sulfite group, a cyclic sulfonate group, a cyclic sulfone group, a cyclic sulfite group
  • the number of sulfone groups, cyclic carboxylate groups or cyclic acid anhydride groups is 1 to 5, and A, B, and C are cyclic carbonate groups, cyclic sulfate groups, cyclic sulfite groups, and cyclic sulfonic acid groups.
  • the total number of ester groups, cyclic sulfone groups, cyclic sulfoxide groups, cyclic carboxylate groups or cyclic acid anhydride groups is less than or equal to 10.
  • a and C are each independently selected from groups represented by structural formula 2:
  • n is selected from an integer from 0 to 4
  • R 1 is selected from hydrogen, halogen, C1-C5 hydrocarbon group or halogenated hydrocarbon group
  • R 2 , R 3 , R 4 , R 5 , R 6 , R 7 are independently selected from each other From C1-C3 alkylene group, C1-C3 alkoxy group, oxygen atom
  • At least one of R 2 , R 3 and R 4 is selected from And at least one of R 2 , R 3 and R 4 is selected from oxygen atoms
  • at least one of R 5 , R 6 and R 7 is selected from And at least one of R 5 , R 6 and R 7 is selected from And at least one of R 5 , R 6 and R 7 is selected from oxygen atoms.
  • the combined group of -R 3 -R 2 -R 4 - and the combined group of -R 7 -R 5 -R 6 - are each independently selected from
  • B is selected from the group represented by Structural Formula 3:
  • m is selected from an integer of 1 to 4
  • R 8 , R 9 and R 10 are each independently selected from C1-C3 hydrocarbylene, C1-C3 alkoxy, oxygen atom, At least one of R 8 , R 9 and R 10 is selected from And at least one of R 8 , R 9 and R 10 is selected from oxygen atoms.
  • the combined groups of -R 9 -R 8 -R 10 - are each independently selected from
  • D and E are each independently selected from groups represented by structural formula 4:
  • z is selected from an integer from 0 to 4
  • R 11 and R 13 are each independently selected from a single bond or a C1-C5 hydrocarbylene group
  • R 12 is selected from a single bond
  • a and C are the same as each other, A and B are the same or different from each other, and D and E are the same as each other.
  • D and E are each independently selected from single bonds or C1-C5 hydrocarbylene groups
  • A, B, and C are each independently selected from substituted or unsubstituted cyclic carbonate groups, cyclic sulfate groups , cyclic sulfite group, cyclic sulfonate group, cyclic sulfone group, cyclic sulfoxide group, cyclic carboxylate group or cyclic acid anhydride group, when A, B or C is substituted, the substituent is selected from halogen, alkyl or haloalkyl.
  • the compound represented by structural formula 1 can be selected from one or more of the following compounds:
  • D and E are each independently selected from groups represented by structural formula 4:
  • z is selected from an integer of 1-4
  • R 11 and R 13 are each independently selected from a single bond or a C1-C5 hydrocarbylene group
  • R 12 is selected from
  • A, B and C are each independently selected from substituted or unsubstituted cyclic carbonate groups, cyclic sulfate groups, cyclic sulfite groups, cyclic sulfonate groups, cyclic sulfone groups, cyclic sulfoxide groups group, cyclic carboxylate group or cyclic acid anhydride group; preferably, when A, B or C is substituted, the substituent is selected from halogen, hydrocarbyl or halogenated hydrocarbyl, more preferably, when A, B or C is substituted , the substituents are selected from halogen, alkyl or haloalkyl.
  • the compound represented by structural formula 1 can be selected from one or more of the following compounds:
  • the compound represented by the structural formula 1 can also be selected from one or more of the following compounds:
  • Compound 1-1 can be prepared by the following methods:
  • the organic solvents such as sorbitol, dimethyl carbonate, methanol alkaline substance catalyst potassium hydroxide and DMF are placed in the reaction vessel, and after reacting for several hours under heating conditions, a certain amount of oxalic acid is added to adjust the pH to neutrality, and the solution is filtered. After recrystallization, intermediate product 1 can be obtained, and then intermediate product 1, carbonate, thionyl chloride, etc. are esterified under high temperature conditions to obtain intermediate product 2, and then intermediate product 2 is obtained by using an oxidant such as sodium periodate. Compound 1-1 can be obtained by oxidation.
  • the compound represented by the structural formula 1 is added in an amount of 0.01-5.0% based on 100% of the total mass of the non-aqueous electrolyte.
  • the addition amount of the compound represented by the structural formula 1 may be 0.01%, 0.02%, 0.05%, 0.1%, 0.5%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%.
  • the additives further include unsaturated cyclic carbonate compounds, fluorinated cyclic carbonate compounds, sultone compounds, lithium difluorophosphate, vinyl sulfate (DTD), difluoro at least one of lithium sulfonimide (LiFSI);
  • the unsaturated cyclic carbonate compounds include at least one of vinylene carbonate (VC) and vinylethylene carbonate (VEC); the fluorinated cyclic carbonate compounds include Fluorinated ethylene carbonate (FEC); the sultone compound is selected from 1,3-propane sultone (PS), 1,4-butane sultone (BS), 1,3-propane sulfonate At least one of lactones (PST).
  • VC vinylene carbonate
  • VEC vinylethylene carbonate
  • FEC Fluorinated ethylene carbonate
  • PS 1,3-propane sultone
  • BS 1,4-butane sultone
  • PST 1,3-propane sulfonate
  • the content of the unsaturated cyclic carbonate compounds is 0.1-5%; the content of the fluorinated cyclic carbonate compounds is 0.1-5%; 0.1-30%; the mass percentage of the sultone compound is 0.1-5%; the mass percentage of the lithium difluorophosphate is 0.1-2%; the vinyl sulfate (DTD)
  • the mass percentage of the lithium bis(fluorosulfonyl)imide (LiFSI) is 0.1-5%; the mass percentage of the lithium bis(fluorosulfonyl)imide (LiFSI) is 0.1-5%.
  • the solvent includes one or more of ether-based solvents, nitrile-based solvents, carbonate-based solvents, and carboxylate-based solvents.
  • the ether solvent includes cyclic ether or chain ether
  • the cyclic ether can be, but not limited to, 1,3-dioxolane (DOL), 1,4-dioxoxane (DX)
  • DOL 1,3-dioxolane
  • DX 1,4-dioxoxane
  • the ether can be specifically, but not limited to, one or more of dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), and diglyme (TEGDME).
  • DDMM dimethoxymethane
  • DME 1,2-dimethoxyethane
  • TEGDME diglyme
  • the nitrile solvent can be specifically, but not limited to, one or more of acetonitrile, glutaronitrile, and malononitrile.
  • Carbonate-based solvents include cyclic carbonates or chain carbonates. Cyclic carbonates can be, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), ⁇ -butyrolactone (GBL), butylene carbonate One or more of esters (BC); the chain carbonate can be specifically but not limited to dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC) one or more.
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate
  • the carboxylate solvent can be specifically, but not limited to, methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate. one or more.
  • the electrolyte salt includes one or more of lithium, sodium, potassium, magnesium, zinc, and aluminum salts.
  • the electrolyte salt is selected from lithium salts.
  • the lithium salt includes LiPF 6 , LiBF 4 , LiBOB, LiDFOB, LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3.
  • LiN(SO 2 F) 2 includes LiPF 6 , LiBF 4 , LiBOB, LiDFOB, LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3.
  • LiN(SO 2 F) 2 is selected from lithium salts.
  • the lithium salt includes LiPF 6 , LiBF 4 , LiBOB, LiDFOB, LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3.
  • LiN(SO 2 F) 2 includes LiPF 6 , LiBF 4 , LiBOB, LiDFOB, LiN(SO
  • the concentration of the electrolyte salt in the non-aqueous electrolyte, is 0.1 mol/L-8 mol/L. In a preferred embodiment, in the non-aqueous electrolyte, the concentration of the electrolyte salt is 0.5mol/L-4mol/L. Specifically, the concentration of the electrolyte salt may be 0.5 mol/L, 1 mol/L, 1.5 mol/L, 2 mol/L, 2.5 mol/L, 3 mol/L, 3.5 mol/L or 4 mol/L.
  • the positive electrode includes a positive electrode active material capable of reversibly intercalating/deintercalating metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.), preferably, the positive electrode
  • the active material is selected from at least one of nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, LiFePO 4 , LiCoO 2 , LiMnO 2 , LiNiMnO 2 and composites thereof.
  • the mass percentage of silicon element in the negative electrode active material is T%
  • the mass percentage of the compound represented by structural formula 1 in the non-aqueous electrolyte is W%
  • the above substances satisfy: when 2 ⁇ T ⁇ 10, preferably 0.01 ⁇ W ⁇ 3; or when 10 ⁇ T ⁇ 50, preferably 0.05 ⁇ W ⁇ 5.
  • the inventors have verified that when the mass percentage of silicon in the negative electrode active material is between 2% and 10%, adding an appropriate amount of electrolyte containing 0.01% to 3% of the compound of structural formula 1 can effectively improve the high temperature of the battery.
  • the addition amount is 3% to 5%, the resistance increases due to the interface film formed by the compound represented by the structural formula 1, and the cycle performance decreases.
  • the mass percentage of silicon in the negative electrode material increases to between 10% and 50%, the optimum content of the compound represented by the structural formula 1 required to form a complete interface film increases. Therefore, when the compound content is 0.05% to 5%, it can be Effectively improve the cycle performance of the battery.
  • the silicon-based material is selected from at least one of silicon materials, silicon oxides, silicon carbon composite materials, and silicon alloy materials.
  • the battery further includes a separator located between the positive electrode and the negative electrode.
  • the separator can be an existing conventional separator, which can be a ceramic separator, a polymer separator, a non-woven fabric, an organic-inorganic composite separator, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), Diaphragms such as double-layer PP/PE, double-layer PP/PP and triple-layer PP/PE/PP.
  • a ceramic separator polypropylene
  • PE polyethylene
  • Diaphragms such as double-layer PP/PE, double-layer PP/PP and triple-layer PP/PE/PP.
  • the mass percentage of silicon element in the negative electrode active material is 2% to 50%. Specifically, the mass percentage of silicon element in the negative electrode active material may be 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%.
  • the compound represented by structural formula 1 When the silicon content is 2% to 50%, the compound represented by structural formula 1 is applied to a silicon-based negative electrode battery. During the battery formation process, the compound represented by structural formula 1 undergoes reduction and decomposition on the surface of the silicon-based negative electrode to form an interface film. The organic components in the interface film are complexed with silicon element in a certain proportion, which effectively inhibits the volume effect of the silicon-containing anode during the charging and discharging process, improves the cyclic inflation, and maintains a significant increase in the cyclic capacity. When the silicon content is more than 50%, the addition of the compound represented by the structural formula 1 cannot effectively improve the cycle.
  • the cathode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 , the conductive carbon black Super-P and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 93:4:3, and then dispersed in N-methyl -2-pyrrolidone (NMP), the positive electrode slurry was obtained.
  • NMP N-methyl -2-pyrrolidone
  • the slurry is evenly coated on both sides of the aluminum foil, dried, calendered and vacuum-dried, and the aluminum lead wires are welded with an ultrasonic welder to obtain a positive plate, the thickness of the plate is 120-150 ⁇ m.
  • a three-layer separator with a thickness of 20 ⁇ m is placed between the positive plate and the negative plate, and then the sandwich structure composed of the positive plate, the negative plate and the separator is wound, and then the rolled body is flattened and placed in an aluminum foil packaging bag. Vacuum bake at 75°C for 48h to obtain the cell to be injected.
  • the electrolyte prepared above was injected into the cells, sealed in vacuum, and left at 45°C for 24 hours.
  • routine formation of the first charging is carried out according to the following steps: 0.05C constant current charging for 180min, 0.1C constant current charging for 180min, 0.2C constant current charging for 120min, aging at 45°C for 48h, secondary vacuum sealing, and then further charging with 0.2C Constant current charge to 4.4V and constant current discharge to 2.75V at 0.2C.
  • the prepared lithium-ion battery was placed in an oven with a constant temperature of 45 °C, charged to 4.4V (LiNi 0.5 Co 0.2 Mn 0.3 O 2 /SiO-C) at a current of 1 C and constant current, and then charged at a constant current and constant voltage until the current dropped to 0.05C, then discharge to 2.75V at a constant current of 1C, and cycle through this cycle, record the discharge capacity and impedance of the first cycle and the discharge capacity and impedance of the last cycle, and measure the initial battery volume of the battery and the volume after 800 cycles.
  • 4.4V LiNi 0.5 Co 0.2 Mn 0.3 O 2 /SiO-C
  • Capacity retention rate discharge capacity of the last lap/capacity of the first lap ⁇ 100%;
  • Impedance growth rate (impedance of the last circle - impedance of the first circle)/impedance of the first circle ⁇ 100%;
  • Swelling ratio (battery volume after cycling-initial battery volume)/initial battery volume ⁇ 100%.
  • the so-called diving refers to The non-linear decay process of the discharge capacity of lithium-ion batteries during cycling is characterized by a large capacity decay of the battery in a short period of time. It can be seen from Comparative Examples 5-12 that when the mass percentage of silicon in the negative electrode active material is greater than 50%, even if 0.01-5.0% of the compound represented by structural formula 1 is added, the battery cycle performance does not improve. At the same time, combined with the data of Examples 1-23, it is found that although the content of the compound represented by the structural formula 1 is increasing, the improvement of the battery cycle performance is not linear, indicating that the improvement of the battery performance is not only related to the content of the compound represented by the structural formula 1. It is also related to the mass percentage of silicon in the negative electrode active material. Only when the two contents are coordinated within a certain range can the battery improve significantly.
  • the mass percentage content (T%) of silicon element in the negative electrode active materials of Examples 24-29 is in the range of 2-10%, and the content of the compound shown in Structural Formula 1 is 0.01-10%. 3%, and although the silicon element mass percentage (T%) in the negative electrode active materials of Examples 30 to 35 is also in the range of 2 to 10%, the content of the compound shown in structural formula 1 is greater than 3%.
  • the test results show that , the lowest capacity retention rate of Examples 24-29 can reach 73.1%, while the highest capacity retention rate of Examples 30-35 is only 75.1%, and the lowest capacity retention rate is only 63.6%.
  • the impedance growth rate of Examples 24-29 And the inflation rate is generally lower than that of Examples 30-35.
  • the mass percentage of silicon in the negative electrode active material is between 2% and 10%
  • adding an appropriate amount of electrolyte containing 0.01% to 3% of the compound of structural formula 1 can effectively improve the high temperature cycle performance of the battery, and the addition amount is
  • the concentration is 3% to 5%
  • the resistance increases due to the interface film formed by the compound represented by the structural formula 1, and the cycle performance decreases. It shows that when the mass percentage content (T%) of silicon element in the negative electrode active material is 2-10%, and the content of the compound represented by structural formula 1 is 0.01-3%, it has a significant effect on the improvement of battery cycle performance.
  • the mass percentage content (T%) of silicon element in the negative electrode active materials of Examples 11, 12, 36-39 is in the range of 10-50%, and the content of the compound represented by structural formula 1 Both are 0.05 to 5%, and although the mass percentage content (T%) of silicon element in the negative electrode active materials in Examples 40 to 44 is also in the range of 10 to 50%, the content of the compound represented by structural formula 1 is less than 0.05 %, the test results show that the capacity retention rates of Examples 11, 12, 36-39 for 800 cycles at 45°C are all above 70%, while the capacity retention rates for Examples 40-44 for 800 cycles at 45°C are all below 70% At the same time, the impedance growth rate and inflation rate of Examples 11, 12, 36-39 are also lower than those of Examples 40-44 by about 20 percentage points.
  • the mass percentage of silicon in the negative electrode material increases to between 10% and 50%, the optimum content of the compound represented by the structural formula 1 required to form a complete interface film increases. Therefore, when the compound content is 0.05% to 5%, it can be Effectively improve the cycle performance of the battery. It shows that when the mass percentage of silicon in the negative electrode active material is 10% ⁇ T ⁇ 50%, and the content of the compound represented by structural formula 1 is 0.05-5%, the impedance, gas swelling and cycle performance of the battery are significantly improved. improve.
  • the present invention can significantly improve the battery cycle gas swelling and impedance increase by adding the compound represented by the structural formula 1 to the non-aqueous electrolyte, reduce the generation of gas during the battery cycle process, and maintain the cycle capacity significantly.
  • the inventor found through a large number of experiments that the battery performance does not linearly improve with the increase in the content of the compound represented by the structural formula 1.
  • the improvement of the battery performance by the compound represented by the structural formula 1 is related to the mass ratio of silicon to the negative electrode active material. When the mass ratio of the element to the negative electrode active material is 2% to 50%, the compound represented by the structural formula 1 can effectively improve the cycle performance of the battery.

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Abstract

为克服现有锂离子电池在循环过程中出现气胀、阻抗增长等问题，本发明提供了一种锂离子电池，包括正极、负极以及非水电解液，所述负极包括负极活性材料，所述负极活性材料中含有硅基材料，所述硅基材料中的硅元素占负极活性材料的质量百分比为2％～50％；所述非水电解液包括添加剂，所述添加剂包括如结构式1所示的化合物中的至少一种： A-D-B-E-C 结构式1 其中，A、B、C各自独立地选自含有环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基的基团；D、E各自独立地选自单键、或含有亚烃基、醚键、硫氧双键或碳氧双键的基团；所述结构式1所示化合物的添加量为0.01～5.0％。本发明能够有效解决锂离子电池循环过程中气胀、阻抗增长等问题，具有优异的循环稳定性。

Description

一种锂离子电池 技术领域
本发明属于电池材料技术领域，具体涉及一种锂离子电池。
背景技术
锂离子电池由于能量密度高、循环寿命长、自放电率小、绿色环保等优点被广泛应用于3C数码设备和新能源动力汽车领域。为了提升锂离子电池的能量密度，方向之一是采用高能量密度的负极活性材料。其中，硅基负极材料因为其具有较高的理论比容量(4200mAh/g)，远超石墨负极理论比容量(372mAh/g)，成为锂离子电池能量密度提升的一个重要方向。然而硅基负极在循环过程中存在很大的体积效应(≥300％)，使得硅基负极表面的固态电解质界面膜在电池循环过程中不断地发生破裂和重生，导致电解液的消耗和活性锂的损失，界面阻抗增加，从而恶化循环性能。同时，在锂离子电池充放电过程中由于副反应会产生大量的还原性气体，造成电池鼓胀，急剧恶化循环性能，并且当电池内部的气体积累到一定程度可能会使电池爆炸，还会带来安全隐患。
因此有必要提供一种锂离子电池，该电池以石墨和硅基复合材料为负极，所用非水电解液可有效改善锂离子电池在循环过程中的气胀和阻抗增长，从而改善电池的循环性能。
发明内容
本发明所解决的技术问题是针对现有锂离子电池在循环过程中出现气胀、阻抗增长等问题，从而提供一种循环性能优异的锂离子电池。
本发明的目的通过下述技术方案实现：
本发明提供了一种锂离子电池，包括正极、负极以及非水电解液，其特征在于，所述负极包括负极活性材料，所述负极活性材料中含有硅基材料，所述硅基材料中的硅元素占负极活性材料的质量百分比为2％～50％；所述非水电解液包括溶剂、电解质盐和添加剂，所述添加剂包括如结构式1所示的化合物中的至少一种：
A-D-B-E-C
结构式1
其中，A、B、C各自独立地选自含有环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基的基团；D、E各自独立地选自单键、或含有亚烃基、醚键、硫氧双键或碳氧双键的基团；以所述非水电解液的总质量为100％计，所述结构式1所示化合物的添加量为0.01～5.0％。
可选的，A、B、C各自独立地含有的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基和环状酸酐基的数量为1～5，且A、B、C的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基和环状酸酐基的总数量小于等于10。
可选的，A、C各自独立地选自结构式2所示的基团：
Figure PCTCN2022083553-appb-000001
其中，n选自0～4的整数，R 1选自氢、卤素、C1～C5的烃基或卤代烃基；R 2、R 3、R 4、R 5、R 6、R 7各自独立地选自C1～C3的亚烃基、C1～C3的烷氧基、氧原子、
Figure PCTCN2022083553-appb-000002
R 2、R 3、R 4中至少一个选自
Figure PCTCN2022083553-appb-000003
且R 2、R 3、R 4中至少一个选自氧原子，R 5、 R 6、R 7中至少一个选自
Figure PCTCN2022083553-appb-000004
且R 5、R 6、R 7中至少一个选自氧原子。
可选的，B选自结构式3所示的基团：
Figure PCTCN2022083553-appb-000005
其中，m选自1～4的整数，R 8、R 9、R 10各自独立地选自C1～C3的亚烃基、C1～C3的烷氧基、氧原子、
Figure PCTCN2022083553-appb-000006
R 8、R 9、R 10中至少一个选自
Figure PCTCN2022083553-appb-000007
且R 8、R 9、R 10中至少一个选自氧原子。
可选的，D、E各自独立地选自结构式4所示的基团：
Figure PCTCN2022083553-appb-000008
其中，z选自0～4的整数，R 11和R 13各自独立地选自单键或C1～C5的亚烃基，R 12选自单键、
Figure PCTCN2022083553-appb-000009
Figure PCTCN2022083553-appb-000010
可选的，D、E各自独立地选自单键或C1～C5的亚烃基，A、B、C各自独立地选自取代或未取代的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基；
优选的，A、B或C经取代时，取代基选自卤素、烃基或卤代烃基，更优选的，A、B或C经取代时，取代基选自卤素、烷基或卤代烷基。
可选的，A与C彼此相同，A与B彼此相同或不同，D与E彼此相同。
可选的，所述结构式1所示化合物选自以下化合物中的一种或多种：
Figure PCTCN2022083553-appb-000011
Figure PCTCN2022083553-appb-000012
Figure PCTCN2022083553-appb-000013
Figure PCTCN2022083553-appb-000014
Figure PCTCN2022083553-appb-000015
可选的，以所述负极活性材料中硅元素的质量百分比为T％，结构式1所示化合物在非水电解液中的质量百分比为W％，以上物质之间满足：2≤T≤10，且0.01≤W≤3；或10＜T≤50，且0.05≤W≤5。
可选的，所述硅基材料选自硅材料、硅的氧化物、硅碳复合材料以及硅合金材料中的至少一种。
根据本发明提供的锂离子电池，使用了硅基材料作为负极材料，可以制备出高能量密度的锂离子电池，而在硅基负极材料的基础上，通过往电解液中加入结构式1所示的化合物，不仅可以提高能量密度，同时还显著改善电池循环气胀以及阻抗增加等问题，减少电池循环过程中气体的产生，循环容量保持明显提升；发明人通过大量的实验发现，电池循环性能并非随结构式1所示化合物含量的增加呈线性改善，结构式1所示化合物对电池性能的提升与硅元素所占负极活性物质的质量比有关，当硅元素占负极活性材料的质量比为2％～50％，结构式1所示化合物的添加量为0.01～5.0％时，电池的循环性能提升显著。
具体实施方式
为了使本发明所解决的技术问题、技术方案及有益效果更加清楚明白，以下结合实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明实施例提供了一种锂离子电池，包括正极、负极以及非水电解液，所述负极包括负极活性材料，所述负极活性材料中含有硅基材料，所述硅基材料中的硅元素占负极活性材料的质量百分比为2％～50％；所述非水电解液包括溶剂、电解质盐和添加剂，所述添加剂包括如结构式1所示的化合物中的至少一种：
A-D-B-E-C
结构式1
其中，A、B、C各自独立地选自含有环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基的基团；D、E各自独立地选自单键、或含有亚烃基、醚键、硫氧双键或碳氧双键的基团；以所述非水电解液的总质量为100％计，所述结构式1所示化合物的添加量为0.01～5.0％。
根据本发明提供的锂离子电池，在硅基负极材料的基础上，通过往非水电解液中加入结构式1所示的化合物，不仅可以制备出高能量密度的锂离子电池，同时还可以显著改善电池循环气胀以及阻抗增加等问题，减少电池循环过程中气体的产生，循环容量保持明显提升；但是在另一些电池体系中却难以起到较好的改善作用，发明人通过大量的实验发现，电池循环性能并非随结构式1所示化合物含量的增加呈线性改善，结构式1所示化合物对电池性能的提升与硅元素所占负极活性物质的质量比有关，当硅元素占负极活性材料的质量比为2％～50％，结构式1所示化合物的添加量为0.01～5.0％时，电池性能提升显著。
关于结构式1所示化合物和负极活性材料中硅元素的相互关系，当硅含量在2％～50％时，将结构式1所示化合物应用于硅基负极电池中，在电池化成过程中，该添加剂在硅基负极表面发生还原分解形成界面膜，界面膜中的有机组分以一定比例与硅元素进行络合，有效抑制了含硅负极在充放电过程的体积效应，改善了循环气胀，循环容量保持明显提升。当硅含量大于50％时，加入结构式1所示化合物并不能有效改善循环，推测原因如下：由于硅含量过高，加入少量该添加剂在化成过程中不能形成完整络合且致密的界面膜，对硅基材料的保护不足，电池的高温循环性能基本得不到改善；而加入大量该添加剂则会导致负极界面的界面膜局部过厚，电池的阻抗严重增加且脱嵌锂不均匀，同样无法有效改善循环性能。
在一些实施例中，A、B、C各自独立地含有的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基的数量为1～5，且A、B、C的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基的总数量小于等于10。
在一些实施例中，A、C各自独立地选自结构式2所示的基团：
Figure PCTCN2022083553-appb-000016
其中，n选自0～4的整数，R 1选自氢、卤素、C1～C5的烃基或卤代烃基；R 2、R 3、R 4、R 5、R 6、R 7各自独立地选自C1～C3的亚烃基、C1～C3的烷氧基、氧原子、
Figure PCTCN2022083553-appb-000017
R 2、 R 3、R 4中至少一个选自
Figure PCTCN2022083553-appb-000018
且R 2、R 3、R 4中至少一个选自氧原子，R 5、R 6、R 7中至少一个选自
Figure PCTCN2022083553-appb-000019
且R 5、R 6、R 7中至少一个选自氧原子。
在优选的实施例中，-R 3-R 2-R 4-的组合基团和-R 7-R 5-R 6-的组合基团各自独立地选自
Figure PCTCN2022083553-appb-000020
Figure PCTCN2022083553-appb-000021
在一些实施例中，B选自结构式3所示的基团：
Figure PCTCN2022083553-appb-000022
其中，m选自1～4的整数，R 8、R 9、R 10各自独立地选自C1～C3的亚烃基、C1～C3的烷氧基、氧原子、
Figure PCTCN2022083553-appb-000023
R 8、R 9、R 10中至少一个选自
Figure PCTCN2022083553-appb-000024
且R 8、R 9、R 10中至少一个选自氧原子。
在优选的实施例中，-R 9-R 8-R 10-的组合基团各自独立地选自
Figure PCTCN2022083553-appb-000025
Figure PCTCN2022083553-appb-000026
在一些实施例中，D、E各自独立地选自结构式4所示的基团：
Figure PCTCN2022083553-appb-000027
其中，z选自0～4的整数，R 11和R 13各自独立地选自单键或C1～C5的亚烃基，R 12选自单键、
Figure PCTCN2022083553-appb-000028
Figure PCTCN2022083553-appb-000029
在一些实施例中，A与C彼此相同，A与B彼此相同或不同，D与E彼此相同。
在一些实施例中，D、E各自独立地选自单键或C1～C5的亚烃基，A、B、C各自独立地选自取代或未 取代的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基，A、B或C经取代时，取代基选自卤素、烷基或卤代烷基。
作为示例，结构式1所示化合物可选自以下化合物中的一种或多种：
Figure PCTCN2022083553-appb-000030
Figure PCTCN2022083553-appb-000031
在一些实施例中，D、E各自独立地选自结构式4所示的基团：
Figure PCTCN2022083553-appb-000032
其中，z选自1～4的整数，R 11和R 13各自独立地选自单键或C1～C5的亚烃基，R 12选自
Figure PCTCN2022083553-appb-000033
Figure PCTCN2022083553-appb-000034
A、B、C各自独立地选自取代或未取代的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸 酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基；优选的，A、B或C经取代时，取代基选自卤素、烃基或卤代烃基，更优选地，A、B或C经取代时，取代基选自卤素、烷基或卤代烷基。
作为示例，结构式1所示化合物可选自以下化合物中的一种或多种：
Figure PCTCN2022083553-appb-000035
Figure PCTCN2022083553-appb-000036
在一些实施例中，所述结构式1所示化合物还可选自以下化合物中的一种或多种：
Figure PCTCN2022083553-appb-000037
Figure PCTCN2022083553-appb-000038
需要说明的是，以上是本发明所要求保护的部分化合物，但不限于此，不应理解为对本发明的限制。
本领域技术人员在知晓结构式1所示化合物的结构式的情况下，根据化学合成领域的公知常识可以知晓上述化合物的制备方法。例如：
化合物1-1可通过以下方法制成：
将山梨醇、碳酸二甲酯、甲醇碱性物质催化剂氢氧化钾以及DMF等有机溶剂置于反应容器中，在加热条件下进行反应数小时后，加入一定量的草酸调节pH至中性，过滤、重结晶后即可得到中间产物1，接着将中间产物1、碳酸酯、二氯亚砜等在高温条件下发生酯化反应得到中间产物2，再使用高碘酸钠等氧化剂将中间产物2氧化即可得到化合物1-1。
化合物1-2可通过以下方法制成：
将双丙酮-D-甘露醇、碳酸二甲酯、甲醇、碳酸钾和二氧六环等在加热、搅拌下进行反应数小时后，加入一定量的草酸调节溶液pH到中性，过滤、浓缩后获得中间产物3；在中间产物3中加入适量的纯水、碳酸酯、酸等进行水解反应获得中间产物4；然后将中间产物4、二氯亚砜和碳酸酯溶剂在加热的条件下制备得到中间产物5；最后使用高碘酸钠等氧化剂将中间产物5氧化即可得到化合物1-2。
在一些实施例中，以所述非水电解液的总质量为100％计，所述结构式1所示化合物的添加量为0.01～5.0％。具体的，所述结构式1所示化合物的添加量可以为0.01％、0.02％、0.05％、0.1％、0.5％、1.0％、2.0％、3.0％、4.0％、5.0％。
当所述结构式1所示化合物的添加量过少时，起不到成膜保护作用，对电池性能的改善效果不明显；当所述结构式1所示化合物的添加量过多时，由于在负极界面形成的界面膜过厚，不利于锂离子穿梭，循环性能反而有所劣化，因此，添加适量的结构式1所示化合物才能改善电池的循环性能。
在一些实施例中，所述添加剂还包括不饱和环状碳酸酯类化合物、氟代环状碳酸酯类化合物、磺酸内酯类化合物、二氟磷酸锂、硫酸乙烯酯(DTD)、双氟磺酰亚胺锂(LiFSI)中的至少一种；
在一些实施例中，所述不饱和环状碳酸酯类化合物包括碳酸亚乙烯酯(VC)、碳酸乙烯亚乙酯(VEC)中的至少一种；所述氟代环状碳酸酯类化合物包括氟代碳酸乙烯酯(FEC)；所述磺酸内酯类化合物选自1,3-丙烷磺内酯(PS)、1,4-丁烷磺内酯(BS)、1,3-丙烯磺内酯(PST)中的至少一种。
在一些实施例中，以所述锂离子电池非水电解液的总质量为100％计，不饱和环状碳酸酯类化合物含量为0.1-5％；所述氟代环状碳酸酯类化合物含量为0.1-30％；所述磺酸内酯类化合物的质量百分含量为0.1-5％；所述二氟磷酸锂的质量百分含量为0.1-2％；所述硫酸乙烯酯(DTD)的质量百分含量为0.1-5％；所述双(氟磺酰)亚胺锂(LiFSI)的质量百分含量为0.1-5％。
在一些实施例中，所述溶剂包括醚类溶剂、腈类溶剂、碳酸酯类溶剂和羧酸酯类溶剂中的一种或多种。
在一些实施例中，醚类溶剂包括环状醚或链状醚，环状醚具体可以但不限于是1,3-二氧戊烷(DOL)、1,4-二氧惡烷(DX)、冠醚、四氢呋喃(THF)、2-甲基四氢呋喃(2-CH 3-THF)，2-三氟甲基四氢呋喃(2-CF 3-THF)中的一种或多种；所述链状醚具体可以但不限于是二甲氧基甲烷(DMM)、1,2-二甲氧基乙烷(DME)、二甘醇二甲醚(TEGDME)中的一种或多种。腈类溶剂具体可以但不限于是乙腈、戊二腈、丙二腈中的一种或多种。碳酸酯类溶剂包括环状碳酸酯或链状碳酸酯，环状碳酸酯具体可以但不限于是碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、γ-丁内酯(GBL)、碳酸亚丁酯(BC)中的一种或多种；链状碳酸酯具体可以但不限于是碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)中的一种或多种。羧酸酯类溶剂具体可以但不限于是乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(EP)、乙酸丁酯、丙酸丙酯(PP)、丙酸丁酯中的一种或多种。
在一些实施例中，所述电解质盐包括锂盐、钠盐、钾盐、镁盐、锌盐和铝盐中的一种或多种。
在优选实施例中，所述电解质盐选自锂盐。在更优选的实施例中，所述锂盐包括LiPF 6、LiBF 4、LiBOB、LiDFOB、LiN(SO 2CF 3) 2、LiN(SO 2C 2F 5) 2、LiC(SO 2CF 3) 3、LiN(SO 2F) 2中的一种或多种。
在一些实施例中，所述非水电解液中，所述电解质盐的浓度为0.1mol/L-8mol/L。在优选的实施例中，所述非水电解液中，所述电解质盐的浓度为0.5mol/L-4mol/L。具体的，所述电解质盐的浓度可以为0.5mol/L、1mol/L、1.5mol/L、2mol/L、2.5mol/L、3mol/L、3.5mol/L或4mol/L。
在一些实施例中，所述正极包括能够可逆地嵌入/脱嵌金属离子(锂离子、钠离子、钾离子、镁离子、锌离子、铝离子等)的正极活性材料，优选的，所述正极活性材料选自镍钴锰三元材料、镍钴铝三元材料、LiFePO 4、LiCoO 2、LiMnO 2、LiNiMnO 2及其复合物中的至少一种。
在一些实施例中，以所述负极活性材料中硅元素的质量百分比为T％，结构式1所示化合物在非水电解液中的质量百分比为W％，以上物质之间满足：当2≤T≤10，优选0.01≤W≤3；或当10＜T≤50，优选0.05≤W≤5。
经本发明人研究验证，当硅元素在负极活性材料中的质量百分比介于2％～10％之间时，加入含有0.01％～3％结构式1所述化合物的适量电解液可有效改善电池高温循环性能，而添加量为3％～5％时，由于结构式1所示化合物形成的界面膜导致阻抗增加，循环性能有所下降。当硅在负极材料中所占质量百分比增加至10％～50％之间时，形成完整界面膜所需的结构式1所示化合物最优含量增加，因此化合物含量为0.05％～5％时，可以有效提升电池的循环性能。
在一些实施例中，所述硅基材料选自硅材料、硅的氧化物、硅碳复合材料以及硅合金材料中的至少一种。
在一些实施例中，所述电池中还包括有隔膜，所述隔膜位于所述正极和所述负极之间。
所述隔膜可为现有常规隔膜，可以是陶瓷隔膜、聚合物隔膜、无纺布、有机-无机复合隔膜等，包括但不限于单层PP(聚丙烯)、单层PE(聚乙烯)、双层PP/PE、双层PP/PP和三层PP/PE/PP等隔膜。
在一些实施例中，所述负极活性材料中硅元素的质量百分比为2％～50％。具体的，所述负极活性材料中硅元素的质量百分比可以为2％、5％、10％、15％、20％、25％、30％、35％、40％、45％、50％。
当硅含量在2％～50％时，将结构式1所示化合物应用于硅基负极电池中，在电池化成过程中，该结构式1所示化合物在硅基负极表面发生还原分解形成界面膜。界面膜中的有机组分以一定比例与硅元素进行络合，有效抑制了含硅负极在充放电过程的体积效应，改善了循环气胀，循环容量保持明显提升。当硅含量大于50％时，加入结构式1所示化合物并不能有效改善循环，推测原因如下：由于硅含量过高，加入少量该结构式1所示化合物在化成过程中不能形成完整络合且致密的界面膜，对硅基材料的保护不足，电池的高温循环性能基本得不到改善；而加入大量该结构式1所示化合物则会导致负极界面的界面膜局部过厚，电池的阻抗严重增加且脱嵌锂不均匀，同样无法有效改善循环性能。
以下通过实施例对本发明进行进一步的说明。
一、实施例1～62和对比例1～17
1)电解液的制备
将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸甲乙酯(EMC)按质量比为EC:DEC:EMC＝1:1:1进行混合，然后加入六氟磷酸锂(LiPF 6)至摩尔浓度为1mol/L，然后按照各表格加入添加剂。添加剂的用量，按照占电解液的总质量的百分比计。
2)正极板的制备
按93:4:3的质量比混合正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、导电碳黑Super-P和粘结剂聚偏二氟乙烯(PVDF)，然后将它们分散在N-甲基-2-吡咯烷酮(NMP)中，得到正极浆料。将浆料均匀涂布在铝箔的两面上，经过烘干、压延和真空干燥，并用超声波焊机焊上铝制引出线后得到正极板，极板的厚度在120-150μm。
3)负极板的制备
按94:1:2.5:2.5的质量比混合负极活性材料SiO-C(石墨：硅＝9：1)、导电碳黑Super-P，粘结剂丁苯橡胶(SBR)和羧甲基纤维素(CMC)，然后将它们分散在去离子水中，得到负极浆料。将浆料涂布在铜箔的两面上，经过烘干、压延和真空干燥，并用超声波焊机焊上镍制引出线后得到负极板，极板的厚度在120-150μm。
4)电芯的制备
在正极板和负极板之间放置厚度为20μm的三层隔离膜，然后将正极板、负极板和隔膜组成的三明治结构进行卷绕，再将卷绕体压扁后放入铝箔包装袋，在75℃下真空烘烤48h，得到待注液的电芯。
5)电芯的注液和化成
在水氧含量分别20ppm、50ppm以下的手套箱中，将上述制备的电解液注入电芯中，经真空封装，45℃搁置24h。
然后按以下步骤进行首次充电的常规化成：0.05C恒流充电180min,0.1C恒流充电180min，0.2C恒流充电120min，在45℃老化48h后，二次真空封口，然后进一步以0.2C的电流恒流充电至4.4V，以0.2C的电流恒流放电至2.75V。
性能测试
1、对上述实施例1～62和对比例1～17制备得到的锂离子电池进行如下性能测试：高温循环性能测试
将制备的锂离子电池置于恒温45℃的烘箱中，以1C的电流恒流充电至4.4V(LiNi 0.5Co 0.2Mn 0.3O 2/SiO-C)，再恒流恒压充电至电流下降至0.05C，然后以1C的电流恒流放电至2.75V，如此循环，记录第1圈的放电容量及阻抗和最后一圈的放电容量及阻抗，测量电池初始电池体积及800圈循环后的体积。
按下式计算高温循环的容量保持率、阻抗增长率和气胀率：
容量保持率＝最后一圈的放电容量/第1次的圈电容量×100％；
阻抗增长率＝(最后一圈的阻抗-第1圈的阻抗)/第1圈的阻抗×100％；
气胀率＝(循环后电池体积-初始电池体积)/初始电池体积×100％。
1.1、实施例1～23和对比例1～12得到的测试结果填入表1。
表1
Figure PCTCN2022083553-appb-000039
Figure PCTCN2022083553-appb-000040
从表1的测试结果可以看出，当负极活性材料中硅元素质量百分含量在2～50％，且采用结构式1所示的化合物作为添加剂其添加量为0.01～5.0％时，电池的容量保持率较未添加结构式1所示的化合物大幅提升，同时阻抗增长率和气胀率显著降低。说明在非水电解液中加入结构式1所示的化合物能够在较大范围内对电池的循环性能起到较好的提升作用。由对比例1-4可以看出，当负极活性材料中硅元素质量百分含量在2～50％时，未添加结构式1所示的化合物的电池容量大幅衰降，出现跳水，所谓跳水是指锂离子电池在循环过程中的放电容量非线性衰降过程，特点是在短时间内电池的容量大幅衰降。由对比例5～12可以看出，当负极活性材料中硅元素质量百分含量大于50％时，即使添加0.01～5.0％的结构式1所示化合物，电池循环性能也并未提高。同时，结合实施例1-23的数据发现，虽然结构式1所示化合物的含量在提升，但是电池循环性能的提升并非呈线性关系，说明电池性能的提升除与结构式1所示化合物的含量有关外还与负极活性材料中硅元素质量百分含量有关，只有两者含量协调在一定范围内，才能对电池的提升起到显著效果。
1.2、实施例24～35和对比例1得到的测试结果填入表2。
表2
Figure PCTCN2022083553-appb-000041
从表2的测试结果可以看出，实施例24-29的负极活性材料中硅元素质量百分含量(T％)均在2～10％范围内、且结构式1所示化合物含量均为0.01～3％，而实施例30～35的负极活性材料中硅元素质量百分含量(T％)虽然也在2～10％范围内，但其结构式1所示化合物含量却大于3％，测试结果显示，实施例24～29的最低容量保持率可达73.1％，而实施例30～35的最高容量保持率只有75.1％，最低容量保持率只有63.6％，同时，实施例24-29的阻抗增长率和气胀率也普遍比实施例30～35的低。当硅元素在负极活性材料中的质量百分比介于2％～10％之间时，加入含有0.01％～3％结构式1所述化合物的适量电解液可有效改善电池高温循环性能，而添加量为3％～5％时，由于结构式1所示化合物形成的界面膜导致阻抗增加， 循环性能有所下降。说明当负极活性材料中硅元素质量百分含量(T％)为2～10％，且结构式1所示化合物的含量在0.01～3％时对电池循环性能的提升起到显著效果。
1.3、实施例11、12、36～44和对比例13得到的测试结果填入表3。
表3
Figure PCTCN2022083553-appb-000042
从表3的测试结果可以看出，实施例11、12、36～39的负极活性材料中硅元素质量百分含量(T％)均在10～50％范围内、且结构式1所示化合物含量均为0.05～5％，而实施例40～44中的负极活性材料中硅元素质量百分含量(T％)虽然也在10～50％范围内，但结构式1所示化合物的含量却小于0.05％，测试结果显示，实施例11、12、36～39的45℃循环800圈容量保持率均在70％以上，而实施例40～44的45℃循环800圈容量保持率都在70％以下；同时实施例11、12、36～39也比实施例40～44的阻抗增长率和气胀率低20个百分点左右。当硅在负极材料中所占质量百分比增加至10％～50％之间时，形成完整界面膜所需的结构式1所示化合物最优含量增加，因此化合物含量为0.05％～5％时，可以有效提升电池的循环性能。说明当负极活性材料中硅元素质量百分含量为10％＜T≤50％时，结构式1所示化合物的含量在0.05～5％时，对电池的阻抗、气胀和循环性能均有显著的改善。
1.4、实施例11、45～58和对比例1-4得到的测试结果填入表4。
表4
Figure PCTCN2022083553-appb-000043
Figure PCTCN2022083553-appb-000044
从表4的测试结果可以看出，在负极活性材料中硅元素质量百分含量为2～50％的条件下，采用不同结构式1所示的化合物加入到电解液中，电池的循环性能均有不同程度的提高。
1.5、实施例59～62和对比例14-17得到的测试结果填入表5。
表5
Figure PCTCN2022083553-appb-000045
从表5的数据可以看出，实施例59～62中，结构式1所示化合物与锂电池的常规添加剂配合使用，而对比例14-17均未添加结构式1所示化合物。测试结果显示，实施例59～62的45℃循环800圈容量保持率明显高于对比例14-17，同时阻抗增长率和气胀率低于对比例14-17，说明结构式1所示化合物与锂电池常规添加剂的配合使用，可进一步提升电池的高温循环性能。
综上所述，本发明通过在非水电解液中加入结构式1所示的化合物，能够显著改善电池循环气胀以及阻抗增加等问题，减少电池循环过程中气体的产生，循环容量保持明显提升；同时发明人通过大量的实验发现，电池性能并非随结构式1所示化合物含量的增加呈线性改善，结构式1所示化合物对电池性能的提升与硅元素所占负极活性物质的质量比有关，当硅元素所占负极活性材料的质量比为2％～50％时，结构式1所示化合物能够有效改善电池的循环性能。经进一步的研究发现，当负极活性材料中硅元素质量百分含量为2～10％，且结构式1所示化合物的含量在0.01～3％时对电池循环性能的提升起到显著效果；同样，当负极活性材料中硅元素质量百分含量为10％＜T≤50％，且结构式1所示化合物的含量在0.05～5％时对电池的气胀、阻抗及循环性能均有显著的改善。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种锂离子电池，包括正极、负极以及非水电解液，其特征在于，所述负极包括负极活性材料，所述负极活性材料中含有硅基材料，所述硅基材料中的硅元素占负极活性材料的质量百分比为2％～50％；所述非水电解液包括溶剂、电解质盐和添加剂，所述添加剂包括如结构式1所示的化合物中的至少一种：
    A-D-B-E-C
    结构式1
    其中，A、B、C各自独立地选自含有环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基的基团；D、E各自独立地选自单键、或含有亚烃基、醚键、硫氧双键或碳氧双键的基团；以所述非水电解液的总质量为100％计，所述结构式1所示化合物的添加量为0.01～5.0％。
  2. 根据权利要求1所述的锂离子电池，其特征在于，A、B、C各自独立地含有的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基和环状酸酐基的数量为1～5，且A、B、C的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基和环状酸酐基的总数量小于等于10。
  3. 根据权利要求1所述的锂离子电池，其特征在于，其特征在于，A、C各自独立地选自结构式2所示的基团：
    Figure PCTCN2022083553-appb-100001
    其中，n选自0～4的整数，R 1选自氢、卤素、C1～C5的烃基或卤代烃基；R 2、R 3、R 4、R 5、R 6、R 7各自独立地选自C1～C3的亚烃基、C1～C3的烷氧基、氧原子、
    Figure PCTCN2022083553-appb-100002
    R 2、R 3、R 4中至少一个选自
    Figure PCTCN2022083553-appb-100003
    且R 2、R 3、R 4中至少一个选自氧原子，R 5、R 6、R 7中至少一个选自
    Figure PCTCN2022083553-appb-100004
    且R 5、R 6、R 7中至少一个选自氧原子。
  4. 根据权利要求1所述的锂离子电池，其特征在于，B选自结构式3所示的基团：
    Figure PCTCN2022083553-appb-100005
    其中，m选自1～4的整数，R 8、R 9、R 10各自独立地选自C1～C3的亚烃基、C1～C3的烷氧基、氧原子、
    Figure PCTCN2022083553-appb-100006
    R 8、R 9、R 10中至少一个选自
    Figure PCTCN2022083553-appb-100007
    且R 8、R 9、R 10中至少一个选自氧原子。
  5. 根据权利要求1所述的锂离子电池，其特征在于，D、E各自独立地选自结构式4所示的基团：
    Figure PCTCN2022083553-appb-100008
    Figure PCTCN2022083553-appb-100009
    其中，z选自0～4的整数，R 11和R 13各自独立地选自单键或C1～C5的亚烃基，R 12选自单键、
    Figure PCTCN2022083553-appb-100010
    Figure PCTCN2022083553-appb-100011
  6. 根据权利要求1所述的锂离子电池，其特征在于，D、E各自独立地选自单键或C1～C5的亚烃基，A、B、C各自独立地选自取代或未取代的环状碳酸酯基、环状硫酸酯基、环状亚硫酸酯基、环状磺酸酯基、环状砜基、环状亚砜基、环状羧酸酯基或环状酸酐基；
    优选的，A、B或C经取代时，取代基选自卤素、烃基或卤代烃基，更优选的，A、B或C经取代时，取代基选自卤素、烷基或卤代烷基。
  7. 根据权利要求1-6任一项所述的锂离子电池，其特征在于，A与C彼此相同，A与B彼此相同或不同，D与E彼此相同。
  8. 根据权利要求1所述的锂离子电池，其特征在于，所述结构式1所示化合物选自以下化合物中的一种或多种：
    Figure PCTCN2022083553-appb-100012
    Figure PCTCN2022083553-appb-100013
    Figure PCTCN2022083553-appb-100014
    Figure PCTCN2022083553-appb-100015
  9. 根据权利要求1-8任一项所述的锂离子电池，其特征在于，以所述负极活性材料中硅元素的质量百分比为T％，结构式1所示化合物在非水电解液中的质量百分比为W％，以上物质之间满足：2≤T≤10，且0.01≤W≤3；或10＜T≤50，且0.05≤W≤5。
  10. 根据权利要求1所述的锂离子电池，其特征在于，所述硅基材料选自硅材料、硅的氧化物、硅碳复合材料以及硅合金材料中的至少一种。
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014119377A1 (ja) * 2013-02-04 2014-08-07 日本電気株式会社 二次電池用負極およびその製造方法、それを用いた二次電池
CN105609874A (zh) * 2015-12-21 2016-05-25 东莞新能源科技有限公司 电解液以及包括该电解液的锂离子电池
CN107293789A (zh) * 2017-07-25 2017-10-24 合肥国轩高科动力能源有限公司 一种循环效果好的锂离子电池及其电解液
WO2018003993A1 (ja) * 2016-07-01 2018-01-04 セントラル硝子株式会社 非水系電解液、及び非水系電解液二次電池

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014119377A1 (ja) * 2013-02-04 2014-08-07 日本電気株式会社 二次電池用負極およびその製造方法、それを用いた二次電池
CN105609874A (zh) * 2015-12-21 2016-05-25 东莞新能源科技有限公司 电解液以及包括该电解液的锂离子电池
WO2018003993A1 (ja) * 2016-07-01 2018-01-04 セントラル硝子株式会社 非水系電解液、及び非水系電解液二次電池
CN107293789A (zh) * 2017-07-25 2017-10-24 合肥国轩高科动力能源有限公司 一种循环效果好的锂离子电池及其电解液

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