WO2024041206A1 - 电池电解液及电池 - Google Patents

电池电解液及电池 Download PDF

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WO2024041206A1
WO2024041206A1 PCT/CN2023/104851 CN2023104851W WO2024041206A1 WO 2024041206 A1 WO2024041206 A1 WO 2024041206A1 CN 2023104851 W CN2023104851 W CN 2023104851W WO 2024041206 A1 WO2024041206 A1 WO 2024041206A1
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electrolyte
battery
mass
lithium
total mass
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PCT/CN2023/104851
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English (en)
French (fr)
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母英迪
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珠海冠宇电池股份有限公司
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Publication of WO2024041206A1 publication Critical patent/WO2024041206A1/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
    • H01M10/056—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
    • 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
    • H01M10/0567—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • 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 technical field of lithium-ion batteries, and in particular to a battery electrolyte and a battery.
  • the positive active material in lithium-ion batteries is structurally unstable at high temperatures, and metal ions can easily dissolve and deposit on the surface of the negative electrode sheet, which destroys the Solid Electrolyte Interface (SEI) film structure on the surface of the negative electrode sheet, causing the negative electrode to break down.
  • SEI Solid Electrolyte Interface
  • the impedance continues to increase, which in turn causes the battery temperature to continue to rise. When heat continues to accumulate and cannot be released, it will cause safety accidents.
  • flame retardants are usually added to the electrolyte to improve the safety performance of the battery at high temperatures, but adding flame retardants can lead to the degradation of other battery properties besides safety performance. Therefore, how to improve battery safety performance while avoiding other battery performance degradation has become an urgent problem to be solved.
  • Embodiments of the present application provide a battery electrolyte, a method for configuring the battery electrolyte, and a battery, which solve the problem of how to improve the safety performance of the battery while avoiding the degradation of other performance of the battery.
  • a battery electrolyte including an organic solvent, additives and electrolyte salt
  • the organic solvent includes an ethyl group solvent
  • the additive includes fluorinated ethylene carbonate
  • the electrolyte salt includes a lithium salt
  • the electrolyte is in contact with the negative electrode sheet
  • the ethyl group solvent, the fluoroethylene carbonate and the lithium salt are configured as a percentage of the total mass of the electrolyte for: 0.4-N 3 ⁇ A+B 2 +C 2 ⁇ 5.2-N 3 ;
  • N is the peel strength value of the negative electrode sheet in gf/mm
  • A is the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte
  • B is the fluoroethylene carbonate.
  • the mass of the ester accounts for the percentage of the total mass of the electrolyte
  • C is the mass of the lithium salt as a percentage of the total mass of the electrolyte.
  • the peel strength N of the negative electrode sheet ranges from 0.1gf/mm to 2gf/mm.
  • the mass of the ethyl group solvent is 40 wt% to 40 wt% of the total mass of the electrolyte. 85wt%.
  • the mass of the fluorinated ethylene carbonate is 5 wt% to 18 wt% of the total mass of the electrolyte.
  • the mass of the lithium salt is 12 wt% to 18 wt% of the total mass of the electrolyte.
  • the lithium salt includes at least one of lithium bistrifluoromethylsulfonimide, lithium bisfluorosulfonimide and lithium hexafluorophosphate.
  • the electrolyte further includes a thiophene compound, and the structural formula of the thiophene compound is:
  • R 1 is any one of hydrogen, halogen and alkyl carbon chain
  • R 2 is any one of hydrogen, halogen and the alkyl carbon chain
  • R 3 is hydrogen, halogen and the alkyl carbon chain. Any one of the chains, R 4 is hydrogen, halogen, or any one of the alkyl carbon chain, and the number of carbon atoms of the alkyl carbon chain is 1 to 10.
  • the halogen is any one of fluorine, chlorine and bromine.
  • At least one carbon or hydrogen in the alkyl carbon chain is replaced by oxygen or halogen.
  • the structural formula of the thiophene compound is any of the following:
  • the mass of the thiophene compound is 0.1 wt% to 2 wt% of the total mass of the electrolyte.
  • embodiments of the present application provide a method for preparing a battery electrolyte, which is used to prepare the battery electrolyte as described in the first aspect, wherein the ethyl group solvent, the fluorine in the battery electrolyte
  • the percentages of ethylene carbonate and the lithium salt respectively accounting for the total mass of the electrolyte are determined based on the expected peel strength of the negative electrode sheet after being infiltrated into the electrolyte, so that the ethyl group solvent,
  • the percentage content of the fluoroethylene carbonate and the lithium salt in the total mass of the electrolyte satisfies: 0.4-N 3 ⁇ A+B 2 +C 2 ⁇ 5.2-N 3 ;
  • N is the peel strength value of the negative electrode sheet in gf/mm
  • A is the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte
  • B is the mass of the fluoroethylene carbonate.
  • the mass is the percentage of the total mass of the electrolyte
  • C is the mass of the lithium salt as a percentage of the total mass of the electrolyte.
  • embodiments of the present application provide a battery, including a positive electrode sheet, a negative electrode sheet and the battery electrolyte as described in the first aspect, where both the positive electrode sheet and the negative electrode sheet are immersed in the battery electrolyte;
  • the battery satisfies the following expression: 0.4-N 3 ⁇ A+B 2 +C 2 ⁇ 5.2-N 3 ;
  • N is the peel strength of the negative electrode sheet in gf/mm
  • A is the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte
  • B is the fluoroethylene carbonate.
  • the mass of C is the percentage of the total mass of the electrolyte
  • C is the mass of the lithium salt as a percentage of the total mass of the electrolyte.
  • the battery electrolyte includes an organic solvent, additives and electrolyte salt.
  • the organic solvent includes an ethyl group solvent
  • the additive includes fluorinated ethylene carbonate
  • the electrolyte salt includes a lithium salt, an ethyl group solvent, and fluorine.
  • the percentages of ethylene carbonate and lithium salt in the total mass of the electrolyte are configured to be 0.4-N 3 ⁇ A+B 2 +C 2 ⁇ 5.2-N 3 .
  • N is the peel strength value of the negative electrode sheet, in gf/mm
  • A is the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte
  • B is the mass of fluoroethylene carbonate as a percentage of the total mass of the electrolyte
  • C is the mass of the lithium salt as a percentage of the total mass of the electrolyte.
  • SEI Solid Electrolyte Interface
  • the electrolyte include a lithium salt that satisfies the above expression, it can provide a sufficient lithium source for the battery, increase the lithium ion migration rate and increase the conductivity, and provide guarantee for the low-temperature performance and long cycle performance of the battery. That is to say, the battery electrolyte provided by the embodiments of the present application solves the problem of how to improve the safety performance of the battery while avoiding the degradation of other performance of the battery.
  • Figure 1 is a schematic structural diagram of a battery provided by an embodiment of the present application.
  • Embodiments of the present application provide a battery electrolyte, including an organic solvent, additives, and an electrolyte salt.
  • the organic solvent includes an ethyl group solvent
  • the additive includes fluoroethylene carbonate
  • the electrolyte salt includes a lithium salt
  • the electrolyte and the negative electrode sheet Contact the percentages of ethyl group solvent, fluoroethylene carbonate and lithium salt in the total mass of the electrolyte are configured as: 0.4-N 3 ⁇ A+B 2 +C 2 ⁇ 5.2-N 3 ;
  • N is the peel strength value of the negative electrode sheet in gf/mm
  • A is the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte
  • B is the mass of fluoroethylene carbonate as a percentage of the total mass of the electrolyte
  • the percentage content of C is the mass of lithium salt as a percentage of the total mass of the electrolyte.
  • N is the peel strength value of the negative electrode sheet, and the unit is gf/mm.
  • the peel strength value of N can be set according to the actual situation.
  • N can be 0.5gf/mm, 0.8gf/mm, 1.8gf/mm, 0.2gf/mm, 0.3gf/mm, 0.4gf/mm, 1.6gf/mm, 0.9gf/mm and the range composed of any two points.
  • the peeling force strength test method includes: cutting the negative electrode pieces into 24mm ⁇ 15cm strips, covering them with glass slides, using a roller to roll the electrode pieces back and forth, and using a stretching machine to test at a speed of 200mm/min. , the test results obtained the peeling force P (unit gf).
  • the peel strength value is calculated using its numerical part, and its unit part is not involved in the calculation.
  • the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte A is 50% (0.5)
  • fluoroethylene carbonate The mass of ester as a percentage of the total mass of the electrolyte B is 10% (0.1)
  • the mass of lithium salt as a percentage of the total mass of the electrolyte C is 14% (0.14)
  • the peel strength value is 0.8gf/mm.
  • the value of N 3 +A+B 2 +C 2 can be 0.45, 0.5, 0.6, 0.7, 0.8, 1.0, 1.5, 2.2, 3.0, 3.5, 4.0, 4.5, 4.78, 5.0, 5.2, etc.
  • the value range of A+B 2 +C 2 +N 3 is 0.45-5.2 (inclusive)
  • the negative electrode sheet and battery electrolyte have a good synergistic effect.
  • the electrolyte include a lithium salt that satisfies the above expression, it can provide a sufficient lithium source for the battery, increase the lithium ion migration rate and increase the conductivity, and provide guarantee for the long cycle performance of the battery.
  • the battery electrolyte includes an organic solvent, additives and electrolyte salt.
  • the organic solvent includes an ethyl group solvent
  • the additive includes fluorinated ethylene carbonate
  • the electrolyte salt includes a lithium salt, an ethyl group solvent, and fluorine.
  • the percentages of ethylene carbonate and lithium salt in the total mass of the electrolyte are configured to be 0.4-N 3 ⁇ A+B 2 +C 2 ⁇ 5.2-N 3 .
  • N is the peel strength value of the negative electrode sheet
  • A is the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte
  • B is the mass of fluoroethylene carbonate as a percentage of the total mass of the electrolyte
  • C is lithium
  • SEI Solid Electrolyte Interface
  • the electrolyte include a lithium salt that satisfies the above expression, it can provide a sufficient lithium source for the battery, increase the lithium ion migration rate and increase the conductivity, and provide guarantee for the low-temperature performance and long cycle performance of the battery. That is to say, the battery electrolyte provided by the embodiments of the present application solves the problem of how to improve battery safety performance while to avoid other performance degradation issues of the battery.
  • the peel strength N of the negative electrode sheet ranges from 0.1 gf/mm to 2 gf/mm.
  • the mass of the ethyl group solvent is 40 wt% to 85 wt% of the total mass of the electrolyte.
  • the mass of fluoroethylene carbonate is 5 wt% to 18 wt% of the total mass of the electrolyte.
  • the mass of the lithium salt is 12 wt% to 18 wt% of the total mass of the electrolyte.
  • the peel strength N of the negative electrode sheet can be 0.1gf/mm, 0.2gf/mm, 0.3gf/mm, 0.4gf/mm, 0.5gf/mm, 0.6gf/mm, 0.7gf/mm, 0.8gf/ mm, 0.9gf/mm, 1.0gf/mm, 1.1gf/mm, 1.2gf/mm, 1.3gf/mm, 1.4gf/mm, 1.5gf/mm, 1.6gf/mm, 2.0gf/mm, etc.
  • the peel strength N of the negative electrode sheet ranges from 0.1gf/mm to 2gf/mm
  • the negative electrode sheet and the electrolyte can have a better synergistic effect, thereby further improving the safety performance of the battery while avoiding other problems with the battery. Performance degradation.
  • the mass of the ethyl group solvent can be 40wt%, 50wt%, 54wt%, 60wt%, 68wt%, 70wt%, 71wt%, 80wt%, 85wt%, etc. of the total mass of the electrolyte.
  • the mass of the ethyl group solvent is 40wt% to 85wt% of the total mass of the electrolyte, the negative electrode sheet and the electrolyte can have better synergy, thereby further improving the safety performance of the battery while avoiding other performance problems of the battery. Deterioration.
  • the mass of fluorinated ethylene carbonate can be 5wt%, 7wt%, 9wt%, 10wt%, 12wt%, 13wt%, 14wt%, 16wt%, 18wt%, etc. of the total mass of the electrolyte.
  • the mass of fluorinated ethylene carbonate When it is 5wt% to 18wt% of the total mass of the electrolyte, the negative electrode sheet and the electrolyte can have a better synergistic effect, thereby further improving the safety performance of the battery and avoiding the degradation of other performance of the battery.
  • the mass of the lithium salt can be 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, etc. of the total mass of the electrolyte.
  • the mass of the lithium salt is 12wt% to 18wt% of the total mass of the electrolyte , which can make the negative electrode sheet and the electrolyte have a better synergistic effect, thereby further improving the safety performance of the battery while avoiding the degradation of other battery performance.
  • the peel strength of the negative electrode sheet, the quality of the ethyl group solvent, the quality of fluoroethylene carbonate and the lithium salt simultaneously meet the above value ranges, compared with the peel strength of the negative electrode sheet, the quality of the ethyl group solvent
  • the negative electrode sheet and the electrolyte can have better synergy.
  • the lithium salt includes lithium bistrifluoromethylsulfonimide, lithium bisfluorosulfonimide, lithium hexafluorophosphate, lithium difluorophosphate, lithium bisoxaloborate, lithium difluoroxaloborate, and difluoroxalophosphate. At least one of lithium, lithium tetrafluoroborate, and lithium tetrafluoroxalate phosphate.
  • the lithium salt includes at least one of lithium bistrifluoromethylsulfonimide, lithium bisfluorosulfonimide, and lithium hexafluorophosphate.
  • the lithium salt can be lithium bistrifluoromethylsulfonimide, or a mixture of lithium bisfluorosulfonimide and lithium hexafluorophosphate.
  • the electrolyte also includes a thiophene compound, and the structural formula of the thiophene compound is:
  • R 1 is any one of hydrogen, halogen and alkyl carbon chain
  • R 2 is any one of hydrogen, halogen and the alkyl carbon chain
  • R 3 is hydrogen, halogen and the alkyl carbon chain. Any one of the chains, R 4 is hydrogen, halogen, or any one of the alkyl carbon chain, and the number of carbon atoms of the alkyl carbon chain is 1 to 10.
  • R 1 , R 2 , R 3 and R 4 may be completely identical, partially identical, or completely different.
  • the number of carbon atoms in the alkyl carbon chain can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.
  • Thiophene compounds can be used as additives in electrolytes.
  • the thiophene compound can undergo a polymerization reaction on the surfaces of the positive and negative electrode sheets, thereby forming a network-like passivation film.
  • the passivation film formed has a small resistance and can cover the surface of the positive electrode active material, which can effectively Prevent the positive electrode active material from releasing oxygen and causing side reactions on the surface of the positive electrode sheet.
  • the network-like passivation film can also cover the surface of the negative electrode active material to inhibit side reactions of the negative electrode active material on the surface of the negative electrode sheet.
  • the halogen is any one of fluorine, chlorine and bromine.
  • R 1 is fluorine
  • R 2 is bromine
  • R 3 is hydrogen
  • R 4 is an alkyl carbon chain.
  • At least one carbon or hydrogen in the alkyl carbon chain is replaced by oxygen or halogen.
  • At least one carbon in the alkyl carbon chain may be substituted by oxygen or halogen, or at least one hydrogen in the alkyl carbon chain may be substituted by oxygen or halogen, or at least one carbon in the alkyl carbon chain and at least one Hydrogen can be replaced by oxygen or halogen.
  • the structural formula of the thiophene compound is any of the following:
  • the thiophene compound When the thiophene compound has any of the above structural formulas, the thiophene compound can form a denser network passivation film with smaller impedance on the surface of the positive and negative electrode sheets, thereby further improving the cycle performance of the battery and making the negative electrode sheet and electrolysis
  • the liquid has better synergy, further improving the low-temperature performance, high-temperature performance and safety performance of the battery.
  • the mass of the thiophene compound is 0.1 wt% to 2 wt% of the total mass of the electrolyte.
  • the mass of the thiophene compound is 0.1wt%, 0.5wt%, 0.6wt%, 0.9wt%, 1.1wt%, 1.6wt%, 1.7wt%, 1.8wt%, 2wt%, etc. of the total mass of the electrolyte.
  • the mass of the thiophene compound is 0.1wt% to 2wt% of the total mass of the electrolyte, the negative electrode sheet and the electrolyte can have a better synergistic effect, thereby further improving the safety performance of the battery while avoiding the degradation of other battery performance.
  • the additives may also include other additives besides fluoroethylene carbonate.
  • the additive includes one or more of nitrile compounds, sulfur-containing compounds and carbonate compounds.
  • the nitrile compound is selected from the group consisting of succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, glyceryltrinitrile, ethoxypentafluorophosphazene, and 1,3,6-hexane trinitrile.
  • succinonitrile glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, glyceryltrinitrile, ethoxypentafluorophosphazene, and 1,3,6-hexane trinitrile.
  • glutaronitrile glutaronitrile
  • adiponitrile pimelonitrile
  • suberonitrile suberonitrile
  • glyceryltrinitrile glyceryltrinitrile
  • ethoxypentafluorophosphazene 1,3,6-hexane trinitrile.
  • the sulfur-containing compound is selected from one or more of 1,3-propane sultone, 1,3-propene sultone, vinyl sulfate, and vinylene sulfate.
  • the carbonate compound is one or more of ethylene carbonate and ethylene ethylene carbonate.
  • the total mass of other additives accounts for 0 wt% to 10 wt% of the total mass of the non-aqueous electrolyte solution.
  • the organic solvent further includes at least one of carbonate, carboxylic acid ester and fluorinated ether.
  • the carbonate includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methylpropyl carbonate.
  • Carboxylic acid esters include at least one of ethyl propionate and propyl propionate.
  • the fluorinated ether may be 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.
  • the embodiments of the present application also provide a method for configuring the battery electrolyte provided in the embodiments of the present application.
  • the ethyl group solvent, fluoroethylene carbonate and lithium salt of the battery electrolyte respectively occupy the electrolyte.
  • the percentage of the total mass is determined based on the expected peel strength of the negative electrode sheet after being infiltrated into the electrolyte, so that the percentage of the ethyl group solvent, fluoroethylene carbonate and lithium salt in the total mass of the electrolyte satisfies: 0.4-N 3 ⁇ A+B 2 +C 2 ⁇ 5.2-N 3 ;
  • N is the peel strength value of the negative electrode sheet in gf/mm
  • A is the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte
  • B is the mass of fluoroethylene carbonate as a percentage of the total mass of the electrolyte
  • the percentage content of C is the mass of lithium salt as a percentage of the total mass of the electrolyte.
  • the ethyl group solvent, fluoroethylene carbonate and lithium salt of the battery electrolyte respectively account for the percentage of the total mass of the electrolyte according to the expected peeling of the negative electrode sheet after being infiltrated into the electrolyte.
  • the intensity is determined so that the percentages of the ethyl group solvent, fluoroethylene carbonate and lithium salt in the total mass of the electrolyte satisfy: 0.4-N 3 ⁇ A+B 2 +C 2 ⁇ 5.2-N 3 .
  • N is the peel strength value of the negative electrode sheet
  • A is the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte
  • B is the mass of fluoroethylene carbonate as a percentage of the total mass of the electrolyte
  • C is lithium
  • the mass of salt accounts for the percentage of the total mass of electrolyte. It can improve the wettability of the negative electrode sheet while forming a relatively SEI film on the surface of the negative electrode sheet. The SEI film covering the surface of the negative electrode sheet will inhibit the side reaction between the negative electrode active material and the electrolyte, thereby reducing the accumulation of side reaction products. This can Improve the peeling strength of the negative electrode sheet, thereby reducing the negative electrode impedance (also reducing the electrical internal resistance of the battery), thereby reducing the risk of self-generated heat and spontaneous combustion of the battery, and improving the safety performance of the battery.
  • the electrolyte include a lithium salt that satisfies the above expression, it can provide a sufficient lithium source for the battery, increase the lithium ion migration rate and increase the conductivity, and provide guarantee for the low-temperature performance and long cycle performance of the battery. That is to say, the battery electrolyte provided by the embodiments of the present application solves the problem of how to improve the safety performance of the battery while avoiding the degradation of other performance of the battery.
  • an embodiment of the present application also provides a battery 10, which includes a positive electrode sheet 12, a negative electrode sheet 11 and an electrolyte 14 provided in an embodiment of the present application.
  • the positive electrode sheet 12 and the negative electrode sheet 11 are both immersed in the electrolyte 14; battery 10 satisfies the following expression: 0.4-N 3 ⁇ A+B 2 +C 2 ⁇ 5.2-N 3 ;
  • N is the peeling strength of the negative electrode sheet 11 obtained by disassembling the battery 10
  • A is the mass of the ethyl group solvent as a percentage of the total mass of the electrolyte 14
  • B is the mass of fluoroethylene carbonate as a percentage of the electrolyte.
  • the percentage of the total mass of 14, C is the mass of the lithium salt as a percentage of the total mass of the electrolyte 14.
  • the desired peel strength value after the negative electrode sheet 11 is infiltrated into the electrolyte 14 and the peel strength after the negative electrode sheet 11 is infiltrated into the electrolyte 14 is generally are equal.
  • the battery 10 can be a rolled battery or a stacked battery.
  • the battery 10 also includes a separator 10 disposed between the positive electrode sheet 12 and the negative electrode sheet 11 , the negative electrode sheet 11 , the separator 10 and the positive electrode sheet 12 They are stacked in sequence, and the positive electrode sheet 12 , the negative electrode sheet 11 and the separator 10 are all immersed in the electrolyte 14 .
  • the structure of the battery is as shown in FIG. 1 .
  • the positive electrode sheet 12 includes a positive electrode current collector, and a positive electrode active material layer is coated on one or both sides of the positive electrode current collector.
  • the positive active material layer includes a positive active material, a conductive agent and a binder.
  • the positive active material is selected from lithium cobalt oxide or lithium cobalt oxide that has been doped and coated with two or more elements among Al, Mg, Mn, Cr, Ti, and Zr.
  • the chemical formula of lithium cobalt oxide that has been doped and coated with two or more elements among Al, Mg, Mn, Cr, Ti, and Zr is Li x Go 1-y1-y2-y3-y4 E y1 F y2 G y3 D y4 O 2 ; 0.95 ⁇ x ⁇ 1.05, 0.01 ⁇ y1 ⁇ 0.1, 0.01 ⁇ y2 ⁇ 0.1, 0 ⁇ y3 ⁇ 0.1, 0 ⁇ y4 ⁇ 0.1, E, F, G, D are selected from Al, Mg, Mn, Cr Two or more elements among , Ti and Zr.
  • the negative electrode sheet 11 includes a negative electrode current collector, and a negative electrode active material layer is coated on one or both sides of the negative electrode current collector.
  • the negative active material layer includes a negative active material, a conductive agent and a binder.
  • the negative active material is graphite.
  • the negative active material includes graphite, and the negative active material further includes at least one of SiOx and Si, where 0 ⁇ x ⁇ 2.
  • the charging cut-off voltage of the battery provided by the embodiment of the present application is 4.48V and above.
  • the battery provided by the embodiments of the present application includes the electrolyte provided by the embodiments of the present application
  • the battery provided by the embodiments of the present application has all the beneficial effects of the electrolyte provided by the embodiments of the present application.
  • the relationship between the negative electrode sheet and the electrolyte there is good synergy between them. Specifically, while improving the wettability of the negative electrode sheet, a relatively strong SEI film can be formed on the surface of the negative electrode sheet.
  • the SEI film will reduce the side reactions between the negative electrode active material and the electrolyte, reduce the accumulation of side reaction products, thereby improving
  • the peeling strength of the negative electrode sheet further reduces the internal resistance of the battery, reduces the risk of self-generated heat and spontaneous combustion of the battery, improves the safety performance of the battery, and also improves other performance of the battery.
  • the electrolyte include a lithium salt that satisfies the above expression, the lithium ion migration rate can be increased and the conductivity can be improved, thereby ensuring the low-temperature performance and long cycle performance of the battery.
  • the lithium ion batteries of Comparative Examples 1-5 and Examples 1-9 were all prepared according to the following preparation method. The only difference lies in the peeling strength of the negative electrode sheet and the electrolyte, as shown in Table 1.
  • cathode active material LiCoO 2 specific surface area as shown in Table 1
  • binder polyvinylidene fluoride (PVDF) binder polyvinylidene fluoride
  • conductive agent acetylene black at a weight ratio of 98.2:1.1:0.7
  • NMP N-methylpyrrolidone
  • aqueous electrolyte 40-85 wt.% of the ethyl group-containing solvent (the specific dosage is shown in Table 1), and the total mass of the non-aqueous electrolyte is 12-18 wt.% LiPF6 (the specific dosage is shown in Table 1) and additives (the specific dosage and type of additives are shown in Table 1), stir evenly to obtain a non-aqueous electrolyte.
  • the required lithium-ion batteries are obtained through vacuum packaging, standing, formation, shaping, sorting and other processes.
  • Peeling force strength test Cut the negative electrode sheets in Examples 1-5 and Examples 1-9 into 24 mm ⁇ 15 cm strips, cover them with glass slides, use a roller to roll the electrode sheets back and forth, and use a stretching machine. The test was carried out at a speed of 200mm/min, and the test results obtained the peeling force P (unit gf).
  • Capacity retention rate (%) Q3/Q2 ⁇ 100%

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Abstract

本申请提供一种电池电解液及电池，其中，电池电解液包括有机溶剂、添加剂和电解质盐，电解液与负极片接触；有机溶剂包括乙基基团溶剂、添加剂包括氟代碳酸乙烯酯，电解质盐包括锂盐，乙基基团溶剂、氟代碳酸乙烯酯和锂盐占电解液总质量的百分含量被配置为：0.4-N3≤A+B2+C2≤5.2-N3。其中，N为负极片的剥离强度值，单位为gf/mm，A为乙基基团溶剂的质量占电解液总质量的百分含量，B为氟代碳酸乙烯酯的质量占电解液总质量的百分含量，C为锂盐的质量占电解液总质量的百分含量。本申请实施例提供的电池电解液解决了如何在提高电池安全性能的同时，避免电池的其他性能劣化的问题。

Description

电池电解液及电池 技术领域
本申请涉及锂离子电池技术领域，尤其涉及一种电池电解液及电池。
背景技术
锂离子电池中的正极活性材料在高温下结构不稳定，金属离子极易溶出并沉积在负极片表面，这破坏了负极片表面的固体电解质界面(Solid Electrolyte Interface，SEI)膜结构，会导致负极阻抗不断增大，进而引起电池温度持续上升，当热量不断积蓄无法释放时便引起安全事故。
目前，通常向电解液中添加阻燃剂，以提高电池在高温下的安全性能，但是添加阻燃剂会导致电池除安全性能之外的其他性能劣化。因此，如何在提高电池安全性能的同时，避免电池的其他性能劣化成为亟待解决的问题。
发明内容
本申请实施例提供一种电池电解液、电池电解液的配置方法及电池，解决了如何在提高电池安全性能的同时，避免电池的其他性能劣化的问题。
为达到上述目的，第一方面，本申请实施例提供一种电池电解液，包括有机溶剂、添加剂和电解质盐，所述有机溶剂包括乙基基团溶剂、所述添加剂包括氟代碳酸乙烯酯，所述电解质盐包括锂盐；所述电解液与负极片接触；所述乙基基团溶剂、所述氟代碳酸乙烯酯和所述锂盐占所述电解液总质量的百分含量被配置为：
0.4-N3≤A+B2+C2≤5.2-N3；
其中，N为所述负极片的剥离强度值，单位为gf/mm，A为所述乙基基团溶剂的质量占所述电解液总质量的百分含量，B为所述氟代碳酸乙烯酯的质量占所述电解液总质量的百分含量，C为所述锂盐的质量占所述电解液总质量的百分含量。
可选地，所述负极片的剥离强度N的取值范围为0.1gf/mm至2gf/mm。
可选地，所述乙基基团溶剂的质量为所述电解液总质量的40wt％至 85wt％。
可选地，所述氟代碳酸乙烯酯的质量为所述电解液总质量的5wt％至18wt％。
可选地，所述锂盐的质量为所述电解液总质量的12wt％至18wt％。
可选地，所述锂盐包括双三氟甲基磺酰亚胺锂、双氟磺酰亚胺锂和六氟磷酸锂中的至少一项。
可选地，所述电解液还包括噻吩化合物，所述噻吩化合物的结构式为：
其中，R1为氢、卤素、烷基碳链中的任一种，R2为氢、卤素、所述烷基碳链中的任一种，R3为氢、卤素、所述烷基碳链中的任一种，R4为氢、卤素、所述烷基碳链中的任一种，所述烷基碳链的碳原子数为1～10。
可选地，所述卤素为氟、氯和溴中任一种。
可选地，所述烷基碳链中的至少一个碳或氢被氧或卤素取代。
可选地，所述噻吩化合物的结构式为以下任一种：
可选地，所述噻吩化合物的质量为所述电解液总质量的0.1wt％至2wt％。
第二方面，本申请实施例提供一种电池电解液的配置方法，用于配置如第一方面所述的电池电解液，所述电池电解液中的所述乙基基团溶剂、所述氟代碳酸乙烯酯和所述锂盐分别占所述电解液总质量的百分含量根据负极片在浸润至所述电解液之后所期望达到的剥离强度确定，以使所述乙基基团溶剂、所述氟代碳酸乙烯酯和所述锂盐占所述电解液总质量的百分含量满足：
0.4-N3≤A+B2+C2≤5.2-N3；
其中，N为负极片的剥离强度值，单位为gf/mm，A为所述乙基基团溶剂的质量占所述电解液总质量的百分含量，B为所述氟代碳酸乙烯酯的质量占所述电解液总质量的百分含量，C为所述锂盐的质量占所述电解液总质量的百分含量。
第三方面，本申请实施例提供一种电池，包括正极片、负极片和如第一方面所述的电池电解液，所述正极片和所述负极片均浸润于所述电池电解液中；所述电池满足以下表达式：
0.4-N3≤A+B2+C2≤5.2-N3；
其中，N为所述负极片的剥离强度，单位为gf/mm，A为所述乙基基团溶剂的质量占所述电解液总质量的百分含量，B为所述氟代碳酸乙烯酯的质量占所述电解液总质量的百分含量，C为所述锂盐的质量占所述电解液总质量的百分含量。
本申请实施例中，通过使电池电解液包括有机溶剂、添加剂和电解质盐，有机溶剂包括乙基基团溶剂、添加剂包括氟代碳酸乙烯酯，电解质盐包括锂盐，乙基基团溶剂、氟代碳酸乙烯酯和锂盐占电解液总质量的百分含量被配置为0.4-N3≤A+B2+C2≤5.2-N3。N为负极片的剥离强度值，单位为gf/mm，A为乙基基团溶剂的质量占电解液总质量的百分含量，B为氟代碳酸乙烯酯的质量占电解液总质量的百分含量，C为锂盐的质量占电解液总质量的百分含量。可以在提升负极片浸润性的同时在负极片表面形成较为坚固的固体电解质界面膜(Solid Electrolyte Interface，SEI)膜，覆盖在负极片表面的SEI膜会抑制负极活性物质与电解液之间的副反应，从而减少副反应产物在负极活性物质和集流体间，以及在负极片表面的堆积，这样可以提升负极片的剥离强度，从而降低负极阻抗(也降低了电池内阻)，进而降低了电池自产热及自燃的风险，提高了电池的安全性能。
此外，通过使电解液包括满足上述表达式的锂盐，可以为电池提供充足锂源，提升锂离子迁移速率提升电导率，为电池低温性能长循环性能提供保障。即是说，本申请实施例提供的电池电解液解决了如何在提高电池安全性能的同时，避免电池的其他性能劣化的问题。
附图说明
为了更清楚的说明本申请实施例中的技术方案，现对说明书附图作如下说明，显而易见地，下述附图仅是本申请的实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据所列附图获得其他附图。
图1是本申请实施例提供的电池的结构示意图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅是本申请一部分实施例，而不是全部的实施例。在本申请中的实施例的基础上，本领域普通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。
本申请实施例提供一种电池电解液，包括有机溶剂、添加剂和电解质盐，有机溶剂包括乙基基团溶剂、添加剂包括氟代碳酸乙烯酯，电解质盐包括锂盐；所述电解液与负极片接触；乙基基团溶剂、氟代碳酸乙烯酯和锂盐占电解液总质量的百分含量被配置为：
0.4-N3≤A+B2+C2≤5.2-N3；
其中，N为负极片的剥离强度值，单位为gf/mm，A为乙基基团溶剂的质量占电解液总质量的百分含量，B为氟代碳酸乙烯酯的质量占电解液总质量的百分含量，C为锂盐的质量占电解液总质量的百分含量。
应理解，N为负极片的剥离强度值，单位为gf/mm。N的剥离强度值可以根据实际情况设置，比如N可为0.5gf/mm、0.8gf/mm、1.8gf/mm、0.2gf/mm、0.3gf/mm、0.4gf/mm、1.6gf/mm、0.9gf/mm以及任意两点组成的范围。其中，剥离力强度测试的方法包括：将负极极片分别裁为24mm×15cm的样条，用载玻片覆盖，使用滚轮来回滚压极片，采用拉伸机以200mm/min的速度进行测试，测试结果得到剥离力P(单位gf)。计算公式如下：剥离强度N(gf/mm)＝P/24mm(宽度)。
在本公开的关系式中，剥离强度值采用其数值部分进行运算，其单位部分不参与运算。以上述关系式为例，例如在本公开实施例1中，所述乙基基团溶剂的质量占电解液总质量的百分含量A为50％(0.5)，氟代碳酸乙烯 酯的质量占电解液总质量的百分含量B为10％(0.1)，锂盐的质量占电解液总质量的百分含量C为14％(0.14)，剥离强度值为0.8gf/mm，则N3+A+B2+C2＝0.83+0.5+0.12+0.142＝1.0416(四舍五入取两位小数可以记为1.04)。
具体实现时，N3+A+B2+C2的取值可以为0.45、0.5、0.6、0.7、0.8、1.0、1.5、2.2、3.0、3.5、4.0、4.5、4.78、5.0、5.2等。当A+B2+C2+N3的取值范围为0.45-5.2(含端点)时，负极片和电池电解液具有较好的协同作用，具体而言，当A+B2+C2+N3的取值范围为0.45-5.2时，可以降低电解液表面张力并抑制锂枝晶生长，降低电解液与负极片的接触角，提高电解液的浸润性，提高锂离子传输速率，提高电池低温放电性能，提高电池界面相容性，抑制负极片和电解液之间的副反应，从而减少堆积在负极活性物质和集流体之间，以及在负极片表面的副反应产物，进而增大负极片的剥离强度，且降低了电池内阻。这样，可以避免电池温度持续上升，导致安全事故，并使得电池的电芯低温性能得到全面提升。
此外，通过使电解液包括满足上述表达式的锂盐，可以为电池提供充足锂源，提升锂离子迁移速率提升电导率，为电池长循环性能提供保障。
本申请实施例中，通过使电池电解液包括有机溶剂、添加剂和电解质盐，有机溶剂包括乙基基团溶剂、添加剂包括氟代碳酸乙烯酯，电解质盐包括锂盐，乙基基团溶剂、氟代碳酸乙烯酯和锂盐占电解液总质量的百分含量被配置为0.4-N3≤A+B2+C2≤5.2-N3。N为负极片的剥离强度值，A为乙基基团溶剂的质量占电解液总质量的百分含量，B为氟代碳酸乙烯酯的质量占电解液总质量的百分含量，C为锂盐的质量占电解液总质量的百分含量。可以在提升负极片浸润性的同时在负极片表面形成较为坚固的固体电解质界面膜(Solid Electrolyte Interface，SEI)膜，覆盖在负极片表面的SEI膜会抑制负极活性物质与电解液之间的副反应，从而减少副反应产物的堆积，这样可以提升负极片的剥离强度，从而降低负极阻抗(也降低了电池内阻)，进而降低了电池自产热及自燃的风险，提高了电池的安全性能。
此外，通过使电解液包括满足上述表达式的锂盐，可以为电池提供充足锂源，提升锂离子迁移速率提升电导率，为电池低温性能长循环性能提供保障。即是说，本申请实施例提供的电池电解液解决了如何在提高电池安全性能的同 时，避免电池的其他性能劣化的问题。
可选地，负极片的剥离强度N的取值范围为0.1gf/mm至2gf/mm。
可选地，乙基基团溶剂的质量为电解液总质量的40wt％至85wt％。
可选地，氟代碳酸乙烯酯的质量为电解液总质量的5wt％至18wt％。
可选地，锂盐的质量为电解液总质量的12wt％至18wt％。
具体实现时，负极片的剥离强度N可以为0.1gf/mm、0.2gf/mm、0.3gf/mm、0.4gf/mm、0.5gf/mm、0.6gf/mm、0.7gf/mm、0.8gf/mm、0.9gf/mm、1.0gf/mm、1.1gf/mm、1.2gf/mm、1.3gf/mm、1.4gf/mm、1.5gf/mm、1.6gf/mm、2.0gf/mm等。当负极片的剥离强度N的取值范围为0.1gf/mm至2gf/mm时，可以使负极片和电解液具有更好的协同作用，从而进一步在提高电池安全性能的同时，避免电池的其他性能劣化。
乙基基团溶剂的质量可以为电解液总质量的40wt％、50wt％、54wt％、60wt％、68wt％、70wt％、71wt％、80wt％、85wt％等。当乙基基团溶剂的质量为电解液总质量的40wt％至85wt％时，可以使负极片和电解液具有更好的协同作用，从而进一步在提高电池安全性能的同时，避免电池的其他性能劣化。
氟代碳酸乙烯酯的质量可以为电解液总质量的5wt％、7wt％、9wt％、10wt％、12wt％、13wt％、14wt％、16wt％、18wt％等，当氟代碳酸乙烯酯的质量为电解液总质量的5wt％至18wt％时，可以使负极片和电解液具有更好的协同作用，从而进一步在提高电池安全性能的同时，避免电池的其他性能劣化。
锂盐的质量可以为电解液总质量的12wt％、13wt％、14wt％、15wt％、16wt％、17wt％、18wt％等，当锂盐的质量为电解液总质量的12wt％至18wt％时，可以使负极片和电解液具有更好的协同作用，从而进一步在提高电池安全性能的同时，避免电池的其他性能劣化。
在负极片的剥离强度、乙基基团溶剂的质量、氟代碳酸乙烯酯的质量和锂盐的质量同时满足上述取值范围时，相较于负极片的剥离强度、乙基基团溶剂的质量、氟代碳酸乙烯酯的质量和锂盐的质量中的一项/二项/三项满足上述取值范围时，可以使负极片和电解液具有更好的协同作用。
可选地，所述锂盐包括双三氟甲基磺酰亚胺锂、双氟磺酰亚胺锂、六氟磷酸锂、二氟磷酸锂、双草酸硼酸锂、二氟草酸硼酸锂、二氟草酸磷酸锂、四氟硼酸锂和四氟草酸磷酸锂中的至少一项。
可选地，锂盐包括双三氟甲基磺酰亚胺锂、双氟磺酰亚胺锂和六氟磷酸锂中的至少一项。比如，锂盐可以为双三氟甲基磺酰亚胺锂，或者双氟磺酰亚胺锂和六氟磷酸锂的混合物。
可选地，电解液还包括噻吩化合物，噻吩化合物的结构式为：
其中，R1为氢、卤素、烷基碳链中的任一种，R2为氢、卤素、所述烷基碳链中的任一种，R3为氢、卤素、所述烷基碳链中的任一种，R4为氢、卤素、所述烷基碳链中的任一种，所述烷基碳链的碳原子数为1～10。
具体实现时，R1、R2、R3和R4可以完全相同、可以部分相同，也可以完全不相同。烷基碳链的碳原子数可以为1、2、3、4、5、6、7、8、9、10。噻吩化合物可以作为电解液中的添加剂。
通过使电解液包括噻吩化合物，可以使噻吩化合物在正、负极片表面发生聚合反应，从而形成网络状钝化膜，其形成的钝化膜阻抗较小，可覆盖在正极活性物质表面，能有效阻止正极活性物质释氧在正极片表面发生副反应。与此同时，网络状钝化膜还可以覆盖在负极活性物质表面，抑制负极活性物质在负极片表面发生副反应。因发生副反应会产生增加阻抗的副反应产物，所以阻止正极活性物质发生副反应能够减少循环过程中电池阻抗的增加，从而改善了电池的循环性能，使得负极片和电解液具有更好的协同作用，进一步提高了电池的低温性能、高温性能和安全性能。
可选地，卤素为氟、氯和溴中的任一种。比如R1为氟，R2为溴，R3为氢，R4为烷基碳链。
可选地，烷基碳链中的至少一个碳或氢被氧或卤素取代。
具体实现时，烷基碳链中的至少一个碳可被氧或卤素取代，或者烷基碳链中的至少一个氢可被氧或卤素取代，或者烷基碳链中的至少一个碳和至少一个氢可被氧或卤素取代。
可选地，噻吩化合物的结构式为以下任一种：
在噻吩化合物的结构式为以上任一种时，噻吩化合物可在正、负极片表面形成更为致密的且阻抗更小的网络状钝化膜，从而进一步改善电池的循环性能，使得负极片和电解液具有更好的协同作用，进一步提高了电池的低温性能、高温性能和安全性能。
可选地，噻吩化合物的质量为电解液总质量的0.1wt％至2wt％。具体实现时，噻吩化合物的质量为电解液总质量的0.1wt％、0.5wt％、0.6wt％、0.9wt％、1.1wt％、1.6wt％、1.7wt％、1.8wt％、2wt％等，当噻吩化合物的质量为电解液总质量的0.1wt％至2wt％时，可以使负极片和电解液具有更好的协同作用，从而进一步在提高电池安全性能的同时，避免电池的其他性能劣化。
可选地，添加剂还可以包括除氟代碳酸乙烯酯之外的其他添加剂，其他添 加剂包括腈类化合物、含硫化合物和碳酸酯化合物中的一种或多种。
可选地，腈类化合物选自丁二腈、戊二腈、己二腈、庚二腈、辛二腈、甘油三腈、乙氧基五氟磷腈、1,3,6-己烷三腈中的一种或多种。
可选地，含硫化合物选自1,3-丙烷磺酸内酯、1,3-丙烯磺酸内酯、硫酸乙烯酯、硫酸亚乙烯酯中的一种或多种。
可选地，碳酸酯化合物为碳酸亚乙酯、碳酸乙烯亚乙酯中的一种或多种。
可选地，其他添加剂的总质量占非水电解液总质量的0wt％至10wt％。
可选地，有机溶剂还包括碳酸酯、羧酸酯和氟代醚中的至少一种。其中，碳酸酯包括碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、碳酸甲丙酯中的至少一种。羧酸酯包括丙酸乙酯、丙酸丙酯中的至少一种。氟代醚可以为1,1,2,3-四氟乙基-2,2,3,3-四氟丙基醚。
本申请实施例还提供一种电池电解液的配置方法，用于配置本申请实施例提供的电池电解液，电池电解液的乙基基团溶剂、氟代碳酸乙烯酯和锂盐分别占电解液总质量的百分含量根据负极片在浸润至电解液之后所期望达到的剥离强度确定，以使乙基基团溶剂、氟代碳酸乙烯酯和锂盐占电解液总质量的百分含量满足：
0.4-N3≤A+B2+C2≤5.2-N3；
其中，N为负极片的剥离强度值，单位为gf/mm，A为乙基基团溶剂的质量占电解液总质量的百分含量，B为氟代碳酸乙烯酯的质量占电解液总质量的百分含量，C为锂盐的质量占电解液总质量的百分含量。
本申请实施例中，通过使电池电解液的乙基基团溶剂、氟代碳酸乙烯酯和锂盐分别占电解液总质量的百分含量根据负极片在浸润至电解液之后所期望达到的剥离强度确定，以使乙基基团溶剂、氟代碳酸乙烯酯和锂盐占电解液总质量的百分含量满足：0.4-N3≤A+B2+C2≤5.2-N3。N为负极片的剥离强度值，A为乙基基团溶剂的质量占电解液总质量的百分含量，B为氟代碳酸乙烯酯的质量占电解液总质量的百分含量，C为锂盐的质量占电解液总质量的百分含量。可以在提升负极片浸润性的同时在负极片表面形成较为SEI膜，覆盖在负极片表面的SEI膜会抑制负极活性物质与电解液之间的副反应，从而减少副反应产物的堆积，这样可以提升负极片的剥离强度，从而降低负极阻抗(也降低了电 池内阻)，进而降低了电池自产热及自燃的风险，提高了电池的安全性能。
此外，通过使电解液包括满足上述表达式的锂盐，可以为电池提供充足锂源，提升锂离子迁移速率提升电导率，为电池低温性能长循环性能提供保障。即是说，本申请实施例提供的电池电解液解决了如何在提高电池安全性能的同时，避免电池的其他性能劣化的问题。
参见图1，本申请实施例还提供一种电池10，包括正极片12、负极片11和本申请实施例提供的电解液14，正极片12和负极片11均浸润于电解液14中；电池10满足以下表达式：
0.4-N3≤A+B2+C2≤5.2-N3；
其中，N为拆解电池10所获得的负极片11的剥离强度，A为乙基基团溶剂的质量占电解液14总质量的百分含量，B为氟代碳酸乙烯酯的质量占电解液14总质量的百分含量，C为锂盐的质量占电解液14总质量的百分含量。
应理解，负极片11浸润至电解液14之后所期望达到的剥离强度值，和负极片11浸润至电解液14之后的剥离强度(即拆解电池10所获得的负极片11的剥离强度)通常而言是相等的。
具体实现时，电池10可以为卷绕式电池，也可以为叠片式电池，电池10还包括设置在正极片12和负极片11之间的隔膜10，负极片11、隔膜10和正极片12依次层叠设置，正极片12、负极片11和隔膜10均浸润在电解液14中。在电池10为叠片式电池时，电池的结构如图1所示。
正极片12包括正极集流体，在正极集流体的单面或双面涂覆有正极活性物质层。正极活性物质层中包括正极活性物质、导电剂和粘结剂。
正极活性物质选自钴酸锂或经过Al、Mg、Mn、Cr、Ti、Zr中两种或多种元素掺杂包覆处理的钴酸锂。经过Al、Mg、Mn、Cr、Ti、Zr中两种或多种元素掺杂包覆处理的钴酸锂的化学式为LixGo1-y1-y2-y3-y4Ey1Fy2Gy3Dy4O2；0.95≤x≤1.05，0.01≤y1≤0.1，0.01≤y2≤0.1，0≤y3≤0.1，0≤y4≤0.1，E、F、G、D选自Al、Mg、Mn、Cr、Ti、Zr中两种或多种元素。
负极片11包括负极集流体，在负极集流体的单面或双面涂覆有负极活性物质层。负极活性物质层中包括负极活性物质、导电剂和粘结剂。
可选地，负极活性物质为石墨。
可选地，负极活性物质包括石墨，且负极活性物质还包括SiOx和Si中的至少一项，其中0<x<2。
本申请实施例提供的电池的充电截止电压在4.48V及以上。
本申请实施例提供的电解液的结构和工作原理可以参考上述实施例，在此不再赘述。由于本申请实施例提供的电池包括本申请实施例提供的电解液，因此本申请实施例提供的电池具有本申请实施例提供的电解液的全部有益效果。
本申请实施例提供的电池中，电解液中含乙基基团溶剂的总量、氟代碳酸乙烯酯和锂盐的含量和负极片的剥离强度符合上述表达式时，负极片和电解液之间具有较好的协同作用。具体而言，可以在提升负极片浸润性的同时，在负极片表面形成较为坚固的SEI膜，SEI膜会降低负极活性物质与电解液之间的副反应，减少副反应产物的堆积，从而提升负极片的剥离强度，进而降低电池内阻，降低电池自产热及自燃的风险，提高了电池安全性能，且使得电池的其他性能也得到提升。此外，通过使电解液包括满足上述表达式的锂盐，可以提升锂离子迁移速率提升电导率，为电池低温性能长循环性能提供保障。
下面结合具体实验，对本申请实施例提供的电池进行说明。
对比例1-5和实施例1-9的锂离子电池均按照下述制备方法进行制备，区别仅在于负极片的剥离强度和电解液不同，具体如表1所示。
(1)正极片制备
将正极活性物质LiCoO2(比表面积如表1所示)、粘结剂聚偏氟乙烯(PVDF)、导电剂乙炔黑按照重量比98.2:1.1:0.7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，直至混合体系成均一流动性的正极浆料；将正极浆料均匀涂覆于厚度为12μm的铝箔上；将上述涂覆好的铝箔在5段不同温度梯度的烘箱烘烤后，再将其在120℃的烘箱干燥8h，然后经过辊压、分切得到所需的不同的正极片。
(2)负极片制备
将质量占比为96.5％的负极活性物质人造石墨，质量占比为0.2％的单壁碳纳米管(SWCNT)导电剂、质量占比为0.8％的导电炭黑(SP)导电剂、质量占比为1.2％的羧甲基纤维素钠(CMC)粘结剂及质量占比为1.3％的丁苯橡胶(SBR)粘结剂以湿法工艺制成浆料，涂覆于负极集流体铜箔的表面，经烘干(温 度：85℃，时间：5h)、辊压和模切得到所需的不同剥离强度的负极片(具体剥离强度如表1所示)。
(3)电解液制备
在充满氩气的手套箱(水分<10ppm，氧分<1ppm)中，将碳酸乙烯酯(EC)和碳酸丙烯酯(PC)以2:1质量比混合均匀，在混合溶液中缓慢加入基于非水电解液总质量40～85wt.％的含乙基基团溶剂(具体用量如表1所示)、基于非水电解液总质量12～18wt.％的LiPF6(具体用量如表1所示)和添加剂(添加剂的具体用量和类型如表1所示)，搅拌均匀得到非水电解液。
(4)隔膜的制备
选用7～9μm厚的聚乙烯隔膜。
(5)锂离子电池的制备
将上述准备的正极片、隔膜、负极片通过卷绕，得到未注液的裸电芯；将裸电芯置于外包装箔中，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、整形、分选等工序，获得所需的锂离子电池。
表1
噻吩化合物的结构式为以下任一种：
对上述对比例1-5和实施例1-9中的电池进行电化学性能测试，相关说明如下：
剥离力强度测试：将对比例1-5和实施例1-9中的负极极片分别裁为24mm×15cm的样条，用载玻片覆盖，使用滚轮来回滚压极片，采用拉伸机以200mm/min的速度进行测试，测试结果得到剥离力P(单位gf)。
其中用到的计算公式如下：剥离强度N(gf/mm)＝P/24mm(宽度)
(1)10℃循环实验：将上述对比例1-5和实施例1-9中的电池置于(10±2)℃环境中，静置2-3个小时，待电池本体达到(10±2)℃时，电池按照0.7C恒流充电截止电流为0.05C，电池充满电后搁置5min，再以0.5C恒流放电至截止电压3.0V，记录前3次循环的最高放电容量为初始容量Q，当循环达到300次数时，记录电池的最后一次的放电容量Q1，记录结果如表2。
其中用到的计算公式如下：容量保持率(％)＝Q1/Q×100％。
(2)70℃高温存储48小时实验：将上述实施例和对比例所得电池置于室温下以0.5C的充放电倍率进行3次充放电循环测试，然后0.5C倍率充到满电状态，记录前3次0.5C循环的最高放电容量Q2。将满电状态的电池在70℃下存储48小时，记录48小时后的电池0.5C放电容量Q3，计算得到电池高温存储的容量保持率和是否产气等实验数据，记录结果如表2。
其中用到的计算公式如下：
容量保持率(％)＝Q3/Q2×100％；
(3)针刺实验：将上述实施例1-9和对比例1-5中的电池用直径ф5～8mm的耐高温钢针(针尖的圆锥角度为45℃-60℃，针的表面光洁无锈蚀、氧化层及油污)，以(25±5)mm/s的速度，从垂直于电池极板的方向贯穿，穿刺位置宜靠近所刺面的几何中心(钢针停留在电池中)。观察当1h或电池表面最高温 度下降至峰值温度10℃及以下时，停止试验。
(4)低温放电实验：将上述对比例1-5和实施例1-9中的电池在环境温度25±3℃，先以0.2C放电至3.0V，搁置5min；以0.7C充电，当电芯端电压达到充电限制电压时，改为恒压充电，直到充电电流≤截止电流，停止充电，搁置5分钟后，以0.2C放电至3.0V，记录此次放电容量为常温容量Q4。然后电芯以0.7C充电，当电芯端电压达到充电限制电压时，改为恒压充电，直到充电电流小于或等于截止电流，停止充电；将充满电的电池在-20±2℃条件下搁置4小时后，以0.2C电流放电至截止电压3.0V，记录放电容量Q5，计算可得低温放电容量保持率，记录结果如表2。
其中用到的计算公式如下：低温放电容量保持率(％)＝Q5/Q4×100％。
(5)130℃热冲击实验：将上述对比例1-5和实施例1-9中的电池用对流方式或循环热空气箱以起始温度(25±3)℃进行加热，温变率(5±2)℃/min，升温至(130±2)℃，保持60min后结束试验，记录电池状态结果如表2。
表2
通过表2中对比例1-5和实施例1-9的电池实验测试结果可知，锂离子电 池通过负极片和电解液的协同作用，当N3+A+B2+C2的值在0.4～5.2范围之间时，能够抑制负极活性物质与电解液之间的副反应，从而减少副反应产物的堆积，进而增大负极片的剥离强度，提高电池界面相容性，使得电池的低温性能、高温性能和安全性能得到有效提升。
上面结合附图对本申请的实施例进行了描述，但是本申请并不局限于上述的具体实施方式，上述的具体实施方式仅仅是示意性的，而不是限制性的，本领域的普通技术人员在本申请的启示下，在不脱离本申请宗旨和权利要求所保护的范围情况下，还可做出很多形式，均属于本申请的保护之内。

Claims (15)

  1. 一种电池电解液，其特征在于，包括有机溶剂、添加剂和电解质盐，所述有机溶剂包括乙基基团溶剂、所述添加剂包括氟代碳酸乙烯酯，所述电解质盐包括锂盐；所述电解液与负极片接触；
    所述乙基基团溶剂、所述氟代碳酸乙烯酯和所述锂盐占所述电解液总质量的百分含量被配置为：
    0.4-N3≤A+B2+C2≤5.2-N3；
    其中，N为所述负极片的剥离强度值，单位为gf/mm，A为所述乙基基团溶剂的质量占所述电解液总质量的百分含量，B为所述氟代碳酸乙烯酯的质量占所述电解液总质量的百分含量，C为所述锂盐的质量占所述电解液总质量的百分含量。
  2. 根据权利要求1所述的电池电解液，其特征在于，所述负极片的剥离强度N的取值范围为0.1gf/mm至2gf/mm；
    和/或，所述乙基基团溶剂的质量为所述电解液总质量的40wt％至85wt％；
    和/或，所述氟代碳酸乙烯酯的质量为所述电解液总质量的5wt％至18wt％；
    和/或，所述锂盐的质量为所述电解液总质量的12wt％至18wt％。
  3. 根据权利要求1或2所述的电池电解液，其特征在于，所述锂盐包括双三氟甲基磺酰亚胺锂、双氟磺酰亚胺锂、六氟磷酸锂、二氟磷酸锂、双草酸硼酸锂、二氟草酸硼酸锂、二氟草酸磷酸锂、四氟硼酸锂和四氟草酸磷酸锂中的至少一项。
  4. 根据权利要求3所述的电池电解液，其特征在于，所述锂盐包括双三氟甲基磺酰亚胺锂、双氟磺酰亚胺锂和六氟磷酸锂中的至少一项。
  5. 根据权利要求1-4任一项所述的电池电解液，其特征在于，所述电解液还包括噻吩化合物，所述噻吩化合物的结构式为：
    其中，R1为氢、卤素、烷基碳链中的任一种，R2为氢、卤素、所述烷基碳链中的任一种，R3为氢、卤素、所述烷基碳链中的任一种，R4为氢、卤素、所述烷基碳链中的任一种，所述烷基碳链的碳原子数为1～10。
  6. 根据权利要求5所述的电池电解液，其特征在于，所述卤素为氟、氯和溴中任一种。
  7. 根据权利要求5或6所述的电池电解液，其特征在于，所述烷基碳链中的至少一个碳或氢，被氧或卤素取代。
  8. 根据权利要求5-7任一项所述的电池电解液，其特征在于，所述噻吩化合物的结构式为以下任一种：

  9. 根据权利要求4所述的电池电解液，其特征在于，所述噻吩化合物的质量为所述电解液总质量的0.1wt％至2wt％。
  10. 根据权利要求1-9任一项所述的电池电解液，其特征在于，所述添加剂还包括腈类化合物、含硫化合物和碳酸酯化合物中的一种或多种。
  11. 根据权利要求10所述的电池电解液，其特征在于，所述腈类化合物、含硫化合物和碳酸酯化合物的总质量占非水电解液总质量的0wt％至10wt％。
  12. 根据权利要求10或11所述的电池电解液，其特征在于，所述腈类化合物选自丁二腈、戊二腈、己二腈、庚二腈、辛二腈、甘油三腈、乙氧基五氟磷腈、1,3,6-己烷三腈中的一种或多种；
    和/或，所述含硫化合物选自1,3-丙烯磺酸内酯、硫酸乙烯酯、硫酸亚乙烯酯中的一种或多种；
    和/或，所述碳酸酯化合物为碳酸亚乙酯、氟代碳酸乙烯酯、碳酸乙烯亚乙酯中的一种或多种。
  13. 根据权利要求1-12任一项所述的电池电解液，其特征在于，所述有机溶剂还包括碳酸酯、羧酸酯和氟代醚中的至少一种。
  14. 根据权利要求13所述的电池电解液，其特征在于，所述碳酸酯包括碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、碳酸甲丙酯中的至少一种；
    和/或，所述羧酸酯包括丙酸乙酯、丙酸丙酯中的至少一种；
    和/或，所述氟代醚包括1,1,2,3-四氟乙基-2,2,3,3-四氟丙基醚。
  15. 一种电池，其特征在于，包括正极片、负极片和如权利要求1-14中任一项所述的电池电解液，所述正极片和所述负极片均浸润于所述电池电解液中；所述电池满足以下表达式：
    0.4-N3≤A+B2+C2≤5.2-N3；
    其中，N为所述负极片的剥离强度，单位为gf/mm，A为所述乙基基团溶剂的质量占所述电解液总质量的百分含量，B为所述氟代碳酸乙烯酯的质量占所述电解液总质量的百分含量，C为所述锂盐的质量占所述电解液总质量的百分含量。
PCT/CN2023/104851 2022-08-25 2023-06-30 电池电解液及电池 WO2024041206A1 (zh)

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