WO2021180021A1 - 一种电解液及其制备方法和应用 - Google Patents

一种电解液及其制备方法和应用 Download PDF

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Publication number
WO2021180021A1
WO2021180021A1 PCT/CN2021/079496 CN2021079496W WO2021180021A1 WO 2021180021 A1 WO2021180021 A1 WO 2021180021A1 CN 2021079496 W CN2021079496 W CN 2021079496W WO 2021180021 A1 WO2021180021 A1 WO 2021180021A1
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compound
electrolyte
lithium
mass
phosphate
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PCT/CN2021/079496
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English (en)
French (fr)
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廖波
李素丽
王海
徐延铭
李俊义
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珠海冠宇电池股份有限公司
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Priority to EP21768518.9A priority Critical patent/EP3996180A4/en
Publication of WO2021180021A1 publication Critical patent/WO2021180021A1/zh
Priority to US17/591,198 priority patent/US20220158243A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M10/0568—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
    • H01M10/056—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
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H01M2300/004—Three solvents
    • 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 relates to an electrolyte and a preparation method and application thereof, and relates to the technical field of lithium secondary batteries.
  • lithium secondary batteries Since the commercialization of lithium secondary batteries, due to their outstanding characteristics such as high energy density and good cycle performance, they have been widely used in consumer digital products such as mobile phones, cameras, notebook computers, automobiles, and artificial intelligence. .
  • the current commercial electrolytes for lithium secondary batteries are mainly prepared by using a mixture of cyclic organic compounds and linear organic compounds as a solvent, and lithium hexafluorophosphate (LiPF 6 ) as an electrolyte.
  • LiPF 6 lithium hexafluorophosphate
  • the generated HF will not only corrode the electrode material, but also accelerate the electrolyte.
  • the decomposition of lithium hexafluorophosphate affects the shuttle of lithium ions between the positive and negative electrodes of the battery, making the cycle performance of the lithium secondary battery difficult to meet the existing requirements.
  • the invention provides an electrolyte and a preparation method and application thereof, which are mainly used to solve the problem of poor cycle performance of lithium secondary batteries caused by the electrolyte.
  • the first aspect of the present invention provides an electrolyte, including an organic solvent, an electrolyte, and an additive.
  • the additive includes the first compound represented by Formula 1, wherein R 1 is selected from a single bond, a substituted or unsubstituted alkoxy group , C1-C6 alkylene, C2-C6 alkenyl, R 2 , R 3 are independently selected from substituted or unsubstituted alkoxy, C1-C6 alkylene, C2-C6 One of alkenyl, R 4 is B or P,
  • the first compound is at least one of the compounds represented by formula 1-1, formula 1-2, formula 1-3, and formula 1-4,
  • the additive further includes a second compound, and the second compound is one or more of a nitrile compound, a sulfur-containing compound, a phosphate compound, a borate compound, a lithium salt compound, and a carbonate compound .
  • the nitrile compound is succinonitrile, glutaronitrile, adiponitrile, pimenonitrile, suberonitrile, sebaconitrile, octadecane dinitrile, glycerol trinitrile, ethylene glycol bis(propionitrile) )
  • ether, fumaric acid dinitrile, ethoxy pentafluorophosphazene, 1,3,6-hexane trinitrile One or more of ether, fumaric acid dinitrile, ethoxy pentafluorophosphazene, 1,3,6-hexane trinitrile;
  • the sulfur-containing compound is one or more of 1,3-propane sultone, 1,3-propene sultone, vinyl sulfate, and vinylene sulfate;
  • the phosphate compound is one or more of tris(trimethylsilyl) phosphate, triallyl phosphate, trimethyl phosphate, triethyl phosphate, and tripropyl phosphate;
  • the borate compound is one or more of tris(trimethylsilicate) borate and trimethyl borate;
  • the lithium salt compound is lithium difluorophosphate, lithium bistrifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium difluorobisoxalate, lithium difluorooxalate, and bisoxalic acid One or more of lithium borate;
  • the carbonate compound is one or more of ethylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate.
  • the mass of the first compound is 0.1-10% of the mass of the electrolyte.
  • the mass of the first compound is 0.2-2% of the mass of the electrolyte.
  • the mass of the second compound is 0.1-20% of the mass of the electrolyte.
  • the mass of the second compound is 1-6% of the mass of the electrolyte.
  • the second aspect of the present invention provides a method for preparing any one of the foregoing electrolyte solutions, which is obtained by mixing additives, electrolytes, and organic solvents.
  • the third aspect of the present invention provides a lithium secondary battery, which includes any one of the above-mentioned electrolytes.
  • the electrolyte contains the first compound
  • the N-containing group in the first compound can be combined with the protic acid in the electrolyte, which not only avoids the effect of the protic acid on the electrolyte Influence, make the electrolyte have better stability; it can also avoid the influence of proton acid on the electrode material, and form an excellent electrode/electrolyte interface film on the positive and negative electrodes, optimize the insertion/extraction of lithium ions on the electrode surface, and improve The cycle performance of the lithium secondary battery is improved.
  • the first compound used in the electrolyte provided by the present invention has a simple structure, and can be purchased from the market, and the preparation process is simple and convenient.
  • the first aspect of the present invention provides an electrolyte, including an organic solvent, an electrolyte, and an additive.
  • the additive includes the first compound represented by Formula 1, wherein R 1 is selected from a single bond, a substituted or unsubstituted alkoxy group , C1-C6 alkylene, C2-C6 alkenyl, R 2 , R 3 are independently selected from substituted or unsubstituted alkoxy, C1-C6 alkylene, C2-C6 One of alkenyl, R 4 is B or P,
  • the present invention provides an electrolyte by adding additives on the basis of the existing electrolyte.
  • the additives include the first compound represented by formula 1, and R 1 is selected from single bond, substituted or unsubstituted One of alkoxy, C1-C6 alkylene, C2-C6 alkenyl, R 2 and R 3 are independently selected from substituted or unsubstituted alkoxy, C1-C6 alkylene, C2 -One of C6 alkenyl groups, R 4 is B or P, wherein, when R 1 in Formula 1 is a single bond, N and R 4 are directly connected.
  • the substituent may be a phenyl group, a fluorine group, a nitrile group, or a phosphate group.
  • the alkylene group in the present invention refers to a linear or branched saturated hydrocarbon group with the general formula C n H 2n , for example, -CH 2 -, -CH 2 CH 2 -, -CH(CH 3 )-CH 2 -etc.;
  • alkoxy is the structure The oxygen atom-containing group which is -OR-, such as -O-CH 2 -, -O-CH 2 -CH 2 -and the like.
  • the electrolyte can be prepared according to the prior art, for example, mixing the existing electrolyte and organic solvent with the additives provided by the present invention.
  • the electrolyte provided by the present invention since the electrolyte contains the first compound, the N-containing group in the first compound can be combined with the protic acid in the electrolyte, which not only avoids the influence of the protic acid on the electrolyte, so that The electrolyte has good stability; it can also avoid the influence of proton acid on the electrode material, and form an excellent electrode/electrolyte interface film on the positive and negative electrodes, optimize the insertion/extraction of lithium ions on the electrode surface, and improve the lithium ion Cycle performance of the secondary battery.
  • the first compound used in the electrolyte provided by the present invention has a simple structure and can be purchased through the market, and the preparation process is simple and convenient.
  • the first compound is at least one of the compounds represented by Formula 1-1, Formula 1-2, Formula 1-3, and Formula 1-4,
  • R 1 is a single bond
  • R 2 and R 3 are both methylene groups
  • R 4 is B
  • R 1 is a single bond
  • R 2 , R 3 are all vinylidene groups
  • R 4 is B
  • R 1 is a single bond
  • R 2 and R 3 are both ethylene groups
  • R 4 is selected from B
  • R 1 is a single bond
  • R 2 and R 3 are both ethylene groups
  • R 4 is P.
  • the additive includes the first compound and the second compound shown in Formula 1.
  • the second compound is one or more of a nitrile compound, a sulfur-containing compound, a phosphate compound, a borate compound, a lithium salt compound, and a carbonate compound.
  • the present invention does not limit the ratio between the various types of compounds.
  • the nitrile compound is succinonitrile, glutaronitrile, adiponitrile, pimenonitrile, suberonitrile, sebaconitrile, octadecane dinitrile, glycerol trinitrile, ethylene glycol bis(propionitrile) )
  • ether, fumaric acid dinitrile, ethoxy pentafluorophosphazene, 1,3,6-hexane trinitrile One or more of ether, fumaric acid dinitrile, ethoxy pentafluorophosphazene, 1,3,6-hexane trinitrile;
  • the sulfur-containing compound is one or more of 1,3-propane sultone, 1,3-propene sultone, vinyl sulfate, and vinylene sulfate;
  • the phosphate compound is one or more of tris(trimethylsilyl) phosphate, triallyl phosphate, trimethyl phosphate, triethyl phosphate, and tripropyl phosphate;
  • the borate compound is one or more of tris(trimethylsilicate) borate and trimethyl borate;
  • the lithium salt compound is lithium difluorophosphate, lithium bistrifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium difluorobisoxalate, lithium difluorooxalate, and bisoxalic acid One or more of lithium borate;
  • the carbonate compound is one or more of ethylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate.
  • the present invention does not limit the ratio between the compounds.
  • the mass of the first compound is 0.1-10% of the mass of the electrolyte.
  • the mass of the second compound is 0.1-20% of the mass of the electrolyte, the synergistic effect of the second compound and the first compound is more significant.
  • the mass of the second compound is controlled to be 1-6% of the mass of the electrolyte.
  • the organic solvent and electrolyte in the electrolyte can be selected according to the prior art.
  • the organic solvent may include one or more of the organic solvents commonly used in electrolytes of lithium secondary batteries, such as cyclic organic solvents and linear organic solvents.
  • the cyclic organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, ⁇ -butyrolactone and ⁇ -valerolactone;
  • the linear organic solvent is selected from two carbonic acid Methyl methyl, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propionate, propyl propionate, 1,1,2,3-tetrafluoroethyl-2,2,3,3-tetra One or more of fluoropropyl ether, etc.
  • the present invention does not particularly limit the ratio between the compounds.
  • the mass ratio of the organic solvent to the electrolyte can also be selected according to conventional techniques in the field, and the present invention does not limit this.
  • the mass of the organic solvent is 60-88% of the mass of the electrolyte.
  • the electrolyte may include lithium salts commonly used in the electrolyte of lithium secondary batteries, such as lithium difluorophosphate (LiPF 2 O 2 ), lithium difluorobisoxalate phosphate (LiDFOP), lithium hexafluorophosphate (LiPF 6 ), and bisfluorosulfonimide
  • lithium difluorophosphate LiPF 2 O 2
  • LiDFOP lithium difluorobisoxalate phosphate
  • LiPF 6 lithium hexafluorophosphate
  • bisfluorosulfonimide LiFSI
  • LiDFOB lithium difluorooxalate borate
  • LiTFSI lithium bis(trifluoromethylsulfonyl)imide
  • LiBOB lithium bisoxalate borate
  • the present invention does not particularly limit the ratio between the compounds.
  • the mass ratio of the lithium salt to the electrolyte is also selected according to conventional techniques in the field, and the present invention does not limit this.
  • the mass of the lithium salt is 8-25% of the mass of the electrolyte.
  • the electrolyte contains the first compound
  • the N-containing group in the first compound can be combined with the protic acid in the electrolyte, which not only avoids the effect of the protic acid on the electrolysis
  • the influence of liquid makes the electrolyte have better stability; it can also avoid the influence of proton acid on the electrode material, and form an excellent electrode/electrolyte interface film on the positive and negative electrodes to optimize the insertion/extraction of lithium ions on the electrode surface , Improve the cycle performance of lithium secondary batteries.
  • the second aspect of the present invention provides a method for preparing any one of the above-mentioned electrolytes, which is obtained by mixing additives, electrolytes, and organic solvents.
  • the second aspect of the present invention provides an electrolyte preparation method, which can be prepared by using conventional electrolytes, that is, the electrolyte can be obtained by mixing the additives provided by the present invention, conventional electrolytes and organic solvents.
  • the selection and quality of the additives For example, as mentioned above, the electrolyte and organic solvent can be selected and prepared according to the prior art.
  • the electrolyte obtained by the preparation method provided by the present invention since the electrolyte contains the first compound, the N-containing group in the first compound can be combined with the protic acid in the electrolyte, which not only avoids the effect of the protic acid on the electrolyte
  • the electrolyte has better stability; it can also avoid the influence of proton acid on the electrode material, and form an excellent electrode/electrolyte interface film on the positive and negative electrodes to optimize the insertion/extraction of lithium ions on the electrode surface.
  • the cycle performance of the lithium secondary battery is improved.
  • the third aspect of the present invention provides a lithium secondary battery, which includes any one of the above-mentioned electrolytes.
  • the third aspect of the present invention provides a lithium secondary battery.
  • those skilled in the art can use conventional technical means to prepare a lithium secondary battery. For example, stack the positive electrode, the separator, and the negative electrode in order, so that the separator is placed between the positive and negative electrodes for isolation, and then wind to obtain a bare cell, and place the bare cell in an outer package and dry After that, the electrolyte provided by the present invention is injected, and the lithium secondary battery is prepared through the steps of vacuum packaging, standing, forming, and shaping.
  • the positive electrode includes a positive electrode current collector layer and a positive electrode membrane arranged on the surface of the positive electrode current collector layer, and the positive electrode membrane is formed of a positive electrode active material.
  • at least one positive electrode active material, conductive agent and binder can be dispersed in an appropriate amount of N-methylpyrrolidone (NMP) solvent, fully stirred and mixed to form a uniform positive electrode slurry, and the positive electrode slurry can be uniformly coated On the positive electrode current collector layer, after drying, rolling and slitting, the positive electrode is obtained.
  • NMP N-methylpyrrolidone
  • the positive electrode active material can be selected from one or two or more of existing metal composite oxides of lithium, cobalt, manganese, nickel, and combinations thereof.
  • composite oxides include lithium cobalt oxide, lithium nickel oxide, lithium manganate, nickel cobalt manganese ternary materials, nickel cobalt aluminum ternary materials, lithium iron phosphate (LFP), lithium nickel manganese oxide, lithium-rich manganese-based materials, etc. .
  • the material of the positive electrode current collector layer may be one or two or more of aluminum foil and nickel foil.
  • the conductive agent may be selected from one or two or more of carbon black, acetylene black, graphene, Ketjen black, and carbon fiber.
  • the binder can be selected from polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, poly One or more of vinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymer, polyvinylpyrrolidone, and polyurethane.
  • the negative electrode includes a negative electrode current collector layer and a negative electrode membrane arranged on the surface of the negative electrode current collector layer, and the negative electrode membrane is formed of a negative electrode active material.
  • the negative electrode active material, the conductive agent, and the binder can be dispersed in an appropriate amount of deionized water, fully stirred and mixed to form a uniform negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector layer, and dried , Rolling and slitting to obtain the negative electrode sheet.
  • the negative electrode active material can be selected from one or two or more of the existing carbon-containing materials, such as artificial graphite, hard carbon, and soft carbon.
  • the material of the negative electrode current collector layer may be one or two or more of copper foil, foamed nickel, and foamed copper.
  • the conductive agent may be selected from one or two or more of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and graphene.
  • the binder can be selected from carboxymethyl cellulose, styrene butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, One or more of polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyvinyl alcohol, and sodium polyacrylate.
  • the diaphragm can be selected from one of the existing diaphragm materials, such as polypropylene diaphragm (PP), polyethylene diaphragm (PE), polyvinylidene fluoride diaphragm and the like.
  • PP polypropylene diaphragm
  • PE polyethylene diaphragm
  • PVF polyvinylidene fluoride diaphragm
  • the present invention does not strictly limit the selection of materials for the above-mentioned positive electrode, negative electrode and separator, and may be materials commonly used in lithium secondary batteries at present, and is not limited to the above-mentioned materials.
  • the electrolyte contains the first compound
  • the N-containing group in the first compound can be combined with the protic acid in the electrolyte, which not only avoids the effect of the protic acid on the electrolysis
  • the influence of liquid makes the electrolyte have better stability; it can also avoid the influence of proton acid on the electrode material, and form an excellent electrode/electrolyte interface film on the positive and negative electrodes to optimize the insertion/extraction of lithium ions on the electrode surface Therefore, the lithium secondary battery has good cycle performance.
  • the first compounds used in each embodiment of the present invention were all purchased from Aladdin, and the second compounds were all purchased from Tichiai (Shanghai) Chemical Industry Development Co., Ltd.
  • the electrolyte provided in this embodiment includes 84% organic solvent, 12% LiPF 6 , 1% of the first compound represented by formula 1-1, and 3% glycerol trinitrile, and the above components are mixed to obtain the electrolyte, wherein the organic solvent It is obtained by mixing ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of 3:5:2.
  • the positive electrode, the separator, and the negative electrode are stacked in order using conventional processes, and then wound to obtain a bare cell.
  • the bare cell is placed in an outer packaging shell, and after drying, it is injected
  • the electrolyte provided in this embodiment is further subjected to the steps of vacuum packaging, standing, forming, and shaping to prepare a lithium secondary battery C1.
  • the preparation method of the positive electrode is as follows:
  • NMP N-methylpyrrolidone
  • the preparation method of the negative electrode is:
  • Disperse graphite, acetylene black conductive agent, SBR and CMC binder in an appropriate amount of deionized water stir and mix thoroughly to form a uniform negative electrode slurry; evenly coat the negative electrode slurry on the negative electrode current collector layer, and dry it. Rolling and slitting to obtain a negative electrode.
  • the diaphragm adopts polypropylene diaphragm (PP).
  • the electrolyte provided in this embodiment includes 86.5% organic solvent, 12% LiPF 6 and 1.5% of the first compound represented by formula 1-1, and the above-mentioned components are mixed to obtain the electrolyte, wherein the organic solvent has a volume ratio of 3: 5:2 is obtained by mixing ethylene carbonate, ethyl methyl carbonate and diethyl carbonate.
  • the lithium secondary battery C2 is prepared by combining the electrolyte provided in this embodiment with the preparation method of the lithium secondary battery provided in Example 1.
  • the electrolyte provided in this embodiment includes 87.9% organic solvent, 12% LiPF 6 and 0.1% of the first compound represented by Formula 1-1, and the above-mentioned components are mixed to obtain the electrolyte, wherein the organic solvent has a volume ratio of 3: 5:2 is obtained by mixing ethylene carbonate, ethyl methyl carbonate and diethyl carbonate.
  • the lithium secondary battery C3 is prepared by combining the electrolyte provided in this embodiment with the preparation method of the lithium secondary battery provided in Example 1.
  • the electrolyte provided in this embodiment includes 80% organic solvent, 12% LiPF 6 and 8% of the first compound represented by Formula 1-1, and the above components are mixed to obtain the electrolyte, wherein the organic solvent has a volume ratio of 3: 5:2 is obtained by mixing ethylene carbonate, ethyl methyl carbonate and diethyl carbonate.
  • the lithium secondary battery C4 is prepared by combining the electrolyte provided in this embodiment with the preparation method of the lithium secondary battery provided in Example 1.
  • the electrolyte provided in this embodiment includes 84% organic solvent, 12% LiPF 6 , 1% of the first compound represented by formula 1-2, and 3% glycerol trinitrile, and the above components are mixed to obtain the electrolyte, wherein the organic solvent It is obtained by mixing ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of 3:5:2.
  • the lithium secondary battery C5 is prepared by combining the electrolyte provided in this embodiment with the preparation method of the lithium secondary battery provided in Example 1.
  • the electrolyte provided in this embodiment includes 84% organic solvent, 12% LiPF 6 , 3% of the first compound represented by formula 1-3, and 1% lithium difluorobisoxalate phosphate, and the electrolyte is obtained after mixing the above components.
  • the organic solvent is obtained by mixing ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 3:5:2.
  • the lithium secondary battery C6 is prepared by combining the electrolyte provided in this embodiment with the preparation method of the lithium secondary battery provided in Example 1.
  • the electrolyte provided in this embodiment includes 84% organic solvent, 12% LiPF 6 , 0.5% of the first compound represented by formula 1-3, 0.5% of the first compound represented by formula 1-4, and 3% Silicon-based) phosphate, and the above-mentioned components are mixed to obtain an electrolyte, wherein the organic solvent is obtained by mixing ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 3:5:2.
  • the lithium secondary battery C7 is prepared by combining the electrolyte provided in this embodiment with the preparation method of the lithium secondary battery provided in Example 1.
  • the electrolyte provided by this comparative example includes 88% organic solvent and 12% LiPF 6 , and the electrolyte is obtained after mixing them.
  • the organic solvent is composed of ethylene carbonate, ethyl methyl carbonate and carbonic acid in a volume ratio of 3:5:2. Mixed diethyl esters.
  • the electrolyte provided in this comparative example was combined with the same method for preparing a lithium secondary battery in Example 1, to prepare a lithium secondary battery D1.
  • the electrolyte provided by this comparative example includes 85% organic solvent, 12% LiPF 6 and 3% glycerol trinitrile, and the above components are mixed to obtain the electrolyte.
  • the organic solvent is composed of ethylene carbonate with a volume ratio of 3:5:2. , Ethyl methyl carbonate and diethyl carbonate are mixed.
  • the electrolyte provided by this comparative example includes 77% organic solvent, 12% LiPF 6 , 8% vinylene carbonate and 3% glycerol trinitrile.
  • the electrolyte is obtained after mixing the above components, wherein the organic solvent is 3: 5:2 is obtained by mixing ethylene carbonate, ethyl methyl carbonate and diethyl carbonate.
  • the electrolyte provided in this comparative example was combined with the same method for preparing a lithium secondary battery in Example 1, to prepare a lithium secondary battery D3.
  • the present invention performs performance tests on the electrolytes and lithium secondary batteries provided in Examples 1-7 and Comparative Examples 1-3, which are specifically described as follows:
  • the electrolyte was placed in an aluminum bottle and sealed, and the aluminum bottle was vacuum-encapsulated with aluminum plastic film, and then stored in a 55-degree incubator for 6 days and then sampled to test its acidity.
  • the test results are shown in Table 1.
  • Capacity retention rate (%) Q2/Q ⁇ 100.
  • Example 1 sample acidity Capacity retention rate
  • Example 2 23.57 94.7%
  • Example 3 24.52 93.1%
  • Example 4 24.14 93.5%
  • Example 5 27.34 95.27
  • Example 6 28.42 91.23
  • Example 7 20.48 90.06 Comparative example 1 89.47 65.7% Comparative example 2 70.93 69.2% Comparative example 3 59.07 69.4%

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Abstract

本发明提供一种电解液，包括有机溶剂、电解质以及添加剂，所述添加剂包括式1所示的第一化合物，其中，R 1选自单键、取代或未取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 2、R 3独立的选自取代或未取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 4为B或P。由于本发明提供的电解液中含有第一化合物，第一化合物中的含N的基团可与电解液中的质子酸相结合，不仅避免了质子酸对电解液的影响，使得电解液具有较好的稳定性；还可以避免质子酸对电极材料的影响，并在正负极形成优异的电极/电解液界面膜，优化锂离子在电极表面的嵌入/脱出，提高了锂二次电池的循环性能。

Description

一种电解液及其制备方法和应用 技术领域
本发明涉及一种电解液及其制备方法和应用，涉及锂二次电池技术领域。
背景技术
自锂二次电池商业化以来，由于其具备能量密度高、循环性能好等突出的特点，已在手机、相机、笔记本电脑等消费类数码产品、汽车、人工智能等领域上得到了广泛的应用。
目前商业化的锂二次电池电解液主要是以环状有机化合物和线型有机化合物的混合物作为溶剂、以六氟磷酸锂(LiPF 6)作为电解质制备得到。但是，由于六氟磷酸锂热稳定性较差，易发生分解反应并生成PF 5，而PF 5又极易与电解液中的微量杂质反应生成HF，生成的HF不仅会腐蚀电极材料，还会加速电解液中六氟磷酸锂的分解，从而影响锂离子在电池正负极之间的穿梭，使锂二次电池的循环性能难以满足现有的需求。
因此，如何提高提高锂二次电池的循环性能受到了越来越多的关注。
发明内容
本发明提供一种电解液及其制备方法和应用，主要用于解决电解液导致的锂二次电池循环性能不佳的问题。
本发明第一方面提供了一种电解液，包括有机溶剂、电解质以及添加剂，所述添加剂包括式1所示的第一化合物，其中，R 1选自单键、取代或未取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 2、R 3独立的选自取代或未取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 4为B或P，
Figure PCTCN2021079496-appb-000001
进一步地，所述第一化合物为式1-1、式1-2、式1-3、式1-4所示化合物中的至少一种，
Figure PCTCN2021079496-appb-000002
进一步地，所述添加剂还包括第二化合物，所述第二化合物为腈类化合物、含硫化合物、磷酸酯化合物、硼酸酯化合物、锂盐类化合物、碳酸酯化合物中的一种或多种。
进一步地，所述腈类化合物为丁二腈、戊二腈、已二腈、庚二腈、辛二腈、葵二腈、十八烷二腈、甘油三腈、乙二醇双(丙腈)醚、富马酸二腈、乙氧基五氟磷腈、1,3,6-己烷三腈中的一种或多种；
和/或，所述含硫化合物为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；
和/或，所述磷酸酯化合物为三(三甲基硅)磷酸酯、磷酸三烯丙基酯、磷酸三甲酯、磷酸三乙酯、磷酸三丙酯中的一种或多种；
和/或，所述硼酸酯化合物为三(三甲基硅)硼酸酯、硼酸三甲酯中的一种或多种；
和/或，所述锂盐类化合物为二氟磷酸锂、双三氟甲基磺酰亚胺锂、双氟磺酰亚胺锂、二氟双草酸磷酸锂、二氟草酸硼酸锂、双草酸硼酸锂中的一种或多种；
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。
进一步地，所述第一化合物的质量为所述电解液质量的0.1-10％。
进一步地，所述第一化合物的质量为所述电解液质量的0.2-2％。
进一步地，所述第二化合物的质量为所述电解液质量的0.1-20％。
进一步地，所述第二化合物的质量为所述电解液质量的1-6％。
本发明第二方面提供了一种上述任一所述的电解液的制备方法，将添加 剂、电解质、有机溶剂混合得到所述电解液。
本发明第三方面提供了一种锂二次电池，包括上述任一所述的电解液。
本发明的实施，至少具有以下优势：
1、根据本发明提供的电解液，由于其电解液中含有第一化合物，第一化合物中的含N的基团可与电解液中的质子酸相结合，不仅避免了质子酸对电解液的影响，使得电解液具有较好的稳定性；还可以避免质子酸对电极材料的影响，并在正负极形成优异的电极/电解液界面膜，优化锂离子在电极表面的嵌入/脱出，提高了锂二次电池的循环性能。
2、本发明提供的电解液中所使用的第一化合物结构简单，并且均可通过市场购买得到，制备工艺简单便捷。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚，下面将结合本发明的实施例，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，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，都属于本发明保护的范围。
本发明第一方面提供了一种电解液，包括有机溶剂、电解质以及添加剂，所述添加剂包括式1所示的第一化合物，其中，R 1选自单键、取代或未取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 2、R 3独立的选自取代或未取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 4为B或P，
Figure PCTCN2021079496-appb-000003
本发明提供了一种电解液，通过在现有的电解液基础上，加入添加剂，具体地，所述添加剂包括式1所示的第一化合物，R 1选自单键、取代或未取 代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 2、R 3独立的选自取代或未取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 4为B或P，其中，当式1中的R 1为单键时，N和R 4直接连接。上述取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中，取代基可以为苯基、氟、腈基、磷酸酯基。
本发明的亚烷基是指通式为C nH 2n的直链或支链的饱和烃基基团，例如可以是-CH 2-、-CH 2CH 2-、-CH(CH 3)-CH 2-等；烯基是指含有双键的烯烃基团，例如可以是-CH＝CH-、-CH＝CH-CH 2-、-CH＝CH-CH＝CH-等；烷氧基是结构为-OR-的含氧原子的基团，例如-O-CH 2-、-O-CH 2-CH 2-等。
在制备时，本领域技术人员可依据现有技术进行电解液的制备，例如将现有的电解质、有机溶剂与本发明提供的添加剂混合即可。根据本发明提供的电解液，由于电解液中含有第一化合物，第一化合物中的含N的基团可与电解液中的质子酸相结合，不仅避免了质子酸对电解液的影响，使得电解液具有较好的稳定性；还可以避免质子酸对电极材料的影响，并在正负极形成优异的电极/电解液界面膜，优化锂离子在电极表面的嵌入/脱出，提高了锂二次电池的循环性能。此外，本发明提供的电解液中所使用的第一化合物结构简单，并且均可通过市场购买得到，制备工艺简单便捷。
在一种实施方式中，所述第一化合物为式1-1、式1-2、式1-3、式1-4所示化合物中至少一种，
Figure PCTCN2021079496-appb-000004
具体地，式1-1所示的化合物中，R 1为单键、R 2、R 3均为亚甲基、R 4为B；式1-2所示的化合物中，R 1为单键、R 2、R 3均为亚乙烯基、R 4为B；式1-3所示的化合物中，R 1为单键，R 2、R 3均为亚乙基、R 4选自B；式1-4所示的化合物中，R 1为单键，R 2、R 3均为亚乙基、R 4为P。
进一步地，发明人发现，在上述第一化合物的基础上，当所述添加剂还 包括第二化合物时，可以进一步提高电极/电解液界面膜的稳定性，从而进一步提高锂二次电池的循环性能，即添加剂包括式1所示的第一化合物和第二化合物。具体地，所述第二化合物为腈类化合物、含硫化合物、磷酸酯化合物、硼酸酯化合物、锂盐类化合物、碳酸酯化合物中的一种或多种。
当本发明的第二化合物选自上述多种类型的化合物中的两种及以上时，本发明不限制各类化合物之间的比例。
进一步地，所述腈类化合物为丁二腈、戊二腈、已二腈、庚二腈、辛二腈、葵二腈、十八烷二腈、甘油三腈、乙二醇双(丙腈)醚、富马酸二腈、乙氧基五氟磷腈、1,3,6-己烷三腈中的一种或多种；
和/或，所述含硫化合物为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；
和/或，所述磷酸酯化合物为三(三甲基硅)磷酸酯、磷酸三烯丙基酯、磷酸三甲酯、磷酸三乙酯、磷酸三丙酯中的一种或多种；
和/或，所述硼酸酯化合物为三(三甲基硅)硼酸酯、硼酸三甲酯中的一种或多种；
和/或，所述锂盐类化合物为二氟磷酸锂、双三氟甲基磺酰亚胺锂、双氟磺酰亚胺锂、二氟双草酸磷酸锂、二氟草酸硼酸锂、双草酸硼酸锂中的一种或多种；
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。
当本发明的第二化合物选自上述某一类化合物中的两种及以上时，本发明不限制各化合物之间的比例。
在本发明具体实施过程中，通过合理控制电解液中第一化合物的加入量，有利于进一步提高锂二次电池的循环性能。具体地，所述第一化合物的质量为所述电解液质量的0.1-10％。
发明人进一步研究发现，随着第一化合物的用量在一定范围内增加，锂二次电池的循环性能都先呈递增、后基本保持不变，最后出现轻微下降的趋势，因此出于经济以及性能优异最大化的考虑，将电解液中第一化合物的质量含量控制在0.2-2％。
此外，当所述第二化合物的质量为所述电解液质量的0.1-20％时，第二化 合物与第一化合物的协同作用更加显著。
进一步地，同样出于经济以及性能优异最大化的考虑，控制所述第二化合物的质量为所述电解液质量的1-6％。
在本发明提供的上述添加剂的基础上，电解液中的有机溶剂和电解质均可依据现有技术进行选择。
其中，有机溶剂可以包括目前锂二次电池电解液中常用的有机溶剂中的一种或多种，例如环状有机溶剂和线型有机溶剂。其中，环状有机溶剂选自碳酸乙烯酯、碳酸丙烯酯、氟代碳酸乙烯酯、γ-丁内酯和γ-戊内酯等中的一种或多种；线型有机溶剂选自碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、碳酸甲丙酯、丙酸乙酯、丙酸丙酯、1,1,2,3-四氟乙基-2,2,3,3-四氟丙基醚等中的一种或多种。
当电解液中的有机溶剂包括上述化合物中的两种或两种以上时，本发明不特别限定各化合物之间的比例。
有机溶剂占电解液的质量比也可依据本领域常规技术进行选择，本发明对此不做限制，例如，有机溶剂的质量为电解液质量的60-88％。
电解质可以包括目前锂二次电池电解液中常用的锂盐，例如二氟磷酸锂(LiPF 2O 2)、二氟双草酸磷酸锂(LiDFOP)、六氟磷酸锂(LiPF 6)、双氟磺酰亚胺锂(LiFSI)、二氟草酸硼酸锂(LiDFOB)、双(三氟甲基磺酰)亚胺锂(LiTFSI)和双草酸硼酸锂(LiBOB)中的一种或多种。
当电解液中的锂盐包括上述化合物中的两种或两种以上时，本发明不特别限定各化合物之间的比例。
锂盐占电解液的质量比同样依据本领域常规技术进行选择，本发明对此不做限制，例如，锂盐的质量为电解液质量的8-25％。
综上所述，根据本发明提供的电解液，由于电解液中含有第一化合物，第一化合物中的含N的基团可与电解液中的质子酸相结合，不仅避免了质子酸对电解液的影响，使得电解液具有较好的稳定性；还可以避免质子酸对电极材料的影响，并在正负极形成优异的电极/电解液界面膜，优化锂离子在电极表面的嵌入/脱出，提高了锂二次电池的循环性能。
本发明第二方面提供了一种上述任一所述的电解液的制备方法，将添加剂、电解质、有机溶剂混合得到所述电解液。
本发明第二方面提供了一种电解液的制备方法，可采用常规电解液制备得到，即将本发明提供的添加剂、常规电解质和有机溶剂混合即可得到该电解液，其中，添加剂的选择和质量比如前所述，电解质和有机溶剂可依据现有技术选择制备。根据本发明提供的制备方法得到的电解液，由于电解液中含有第一化合物，第一化合物中的含N的基团可与电解液中的质子酸相结合，不仅避免了质子酸对电解液的影响，使得电解液具有较好的稳定性；还可以避免质子酸对电极材料的影响，并在正负极形成优异的电极/电解液界面膜，优化锂离子在电极表面的嵌入/脱出，提高了锂二次电池的循环性能。
本发明第三方面提供了一种锂二次电池，包括上述任一所述的电解液。
本发明第三方面提供了一种锂二次电池，在本发明提供的电解液基础上，本领域技术人员可采用常规技术手段制备得到锂二次电池。例如，将正极、隔膜和负极按顺序叠好，使隔膜处于正负极之间以起到隔离的作用，然后进行卷绕得到裸电芯，并将裸电芯置于外包装壳中，干燥后，注入本发明提供的电解液，经过真空封装、静置、化成、整形等工序，制备得到锂二次电池。
其中，正极包括正极集流体层和设置在正极集流体层表面的正极膜片，正极膜片由正极活性物质形成。具体地，可以将至少一种正极活性物质与导电剂和粘结剂散在适量的N-甲基吡咯烷酮(NMP)溶剂中，充分搅拌混合形成均匀的正极浆料，并将正极浆料均匀涂覆在正极集流体层上，经过烘干、辊压和分切，得到正极。
正极活性物质可以选自现有的锂与钴、锰、镍及其组合的金属复合氧化物中的一种或两种以上。例如，复合氧化物包括钴酸锂、镍酸锂、锰酸锂、镍钴锰三元材料、镍钴铝三元材料、磷酸铁锂(LFP)、镍锰酸锂、富锂锰基材料等。
正极集流体层的材料可以为铝箔、镍箔中的一种或两种以上。
导电剂可以选自炭黑、乙炔黑、石墨烯、科琴黑、碳纤维中的一种或两种以上。
粘结剂可以选自聚四氟乙烯、聚偏二氟乙烯、聚氟乙烯、聚乙烯、聚丙烯、聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化聚氯乙烯、含环氧乙烷的聚合物、聚乙烯吡咯烷酮、聚氨酯中的一种或两种以上。
负极包括负极集流体层和设置在负极集流体层表面的负极膜片，负极膜片由负极活性物质形成。具体地，可以将负极活性物质与导电剂、粘结剂分散在适量的去离子水中，充分搅拌混合形成均匀的负极浆料；将负极浆料均匀涂覆在负极集流体层上，经过烘干、辊压和分切，得到负极片。
负极活性物质可选自现有含碳的材料中的一种或两种以上，例如人造石墨、硬炭、软炭等。
负极集流体层的材料可以为铜箔、泡沫镍、泡沫铜中的一种或两种以上。
导电剂可以选自天然石墨、人造石墨、炭黑、乙炔黑、科琴黑、碳纤维、石墨烯中的一种或两种以上。
粘结剂可以选自羧甲基纤维素、丁苯橡胶、聚氯乙烯、羧化聚氯乙烯、聚氟乙烯、含环氧乙烷的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏二氟乙烯、聚乙烯、聚丙烯、聚酰胺酰亚胺、聚乙烯醇、聚丙烯酸钠、中的一种或两种以上。
隔膜可选自现有的隔膜材料中的一种，例如聚丙烯隔膜(PP)、聚乙烯隔膜(PE)、聚偏二氟乙烯隔膜等。
本发明并不严格限定上述正极、负极以及隔膜的材料选择，可以是目前锂二次电池中常用的材料，并不限于上述材料。
综上，根据本发明提供的锂二次电池，由于电解液中含有第一化合物，第一化合物中的含N的基团可与电解液中的质子酸相结合，不仅避免了质子酸对电解液的影响，使得电解液具有较好的稳定性；还可以避免质子酸对电极材料的影响，并在正负极形成优异的电极/电解液界面膜，优化锂离子在电极表面的嵌入/脱出，因此该锂二次电池具备良好的循环性能。
以下，通过具体实施例对本发明的电解液和锂二次电池进行详细的介绍。本发明各实施例中所使用的第一化合物均购自阿拉丁，第二化合物均购自梯希爱(上海)化成工业发展有限公司。
实施例1
本实施例提供的电解液包括84％有机溶剂、12％LiPF 6、1％式1-1所示的第一化合物以及3％甘油三腈，并将上述成分混合后得到电解液，其中有机溶 剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
在本实施例提供的电解液基础上，采用常规工艺将正极、隔膜和负极按顺序叠好，然后进行卷绕得到裸电芯，并将裸电芯置于外包装壳中，干燥后，注入本实施例提供的电解液，再经过真空封装、静置、化成、整形等工序，制备得到锂二次电池C1。
其中正极的制备方法为：
将钴酸锂、乙炔黑导电剂以及PVDF粘结剂分散在适量的N-甲基吡咯烷酮(NMP)溶剂中，充分搅拌混合形成均匀的正极浆料；将正极浆料均匀涂覆在正极集流体层上，经过烘干、辊压和分切，得到正极。
负极的制备方法为：
将石墨、乙炔黑导电剂以及SBR和CMC粘结剂分散在适量的去离子水中，充分搅拌混合形成均匀的负极浆料；将负极浆料均匀涂覆在负极集流体层上，经过烘干、辊压和分切，得到负极。
隔膜采用聚丙烯隔膜(PP)。
实施例2
本实施例提供的电解液包括86.5％有机溶剂、12％LiPF 6以及1.5％式1-1所示的第一化合物，并将上述成分混合后得到电解液，其中有机溶剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
将本实施例提供的电解液结合实施例1提供的锂二次电池的制备方法制备得到锂二次电池C2。
实施例3
本实施例提供的电解液包括87.9％有机溶剂、12％LiPF 6以及0.1％式1-1所示的第一化合物，并将上述成分混合后得到电解液，其中有机溶剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
将本实施例提供的电解液结合实施例1提供的锂二次电池的制备方法制备得到锂二次电池C3。
实施例4
本实施例提供的电解液包括80％有机溶剂、12％LiPF 6以及8％式1-1所示的第一化合物，并将上述成分混合后得到电解液，其中有机溶剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
将本实施例提供的电解液结合实施例1提供的锂二次电池的制备方法制备得到锂二次电池C4。
实施例5
本实施例提供的电解液包括84％有机溶剂、12％LiPF 6、1％式1-2所示的第一化合物以及3％甘油三腈，并将上述成分混合后得到电解液，其中有机溶剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
将本实施例提供的电解液结合实施例1提供的锂二次电池的制备方法制备得到锂二次电池C5。
实施例6
本实施例提供的电解液包括84％有机溶剂、12％LiPF 6、3％式1-3所示的第一化合物以及1％二氟双草酸磷酸锂，并将上述成分混合后得到电解液，其中有机溶剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
将本实施例提供的电解液结合实施例1提供的锂二次电池的制备方法制备得到锂二次电池C6。
实施例7
本实施例提供的电解液包括84％有机溶剂、12％LiPF 6、0.5％式1-3所示的第一化合物、0.5％式1-4所示的第一化合物以及3％三(三甲基硅)磷酸酯，并将上述成分混合后得到电解液，其中有机溶剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
将本实施例提供的电解液结合实施例1提供的锂二次电池的制备方法制备得到锂二次电池C7。
对比例1
本对比例提供的电解液包括88％有机溶剂、12％LiPF 6，并将其混合后得到电解液，其中有机溶剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
将本对比例提供的电解液结合实施例1相同的锂二次电池制备方法，制备得到锂二次电池D1。
对比例2
本对比例提供的电解液包括85％有机溶剂、12％LiPF 6以及3％甘油三腈，并将上述成分混合后得到电解液，其中有机溶剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
将本对比例提供的电解液结合实施例1相同的锂二次电池制备方法，制备得到锂二次电池D2。
对比例3
本对比例提供的电解液包括77％有机溶剂、12％LiPF 6、8％碳酸亚乙烯酯以及3％甘油三腈，并将上述成分混合后得到电解液，其中有机溶剂由体积比为3:5:2的碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯混合得到。
将本对比例提供的电解液结合实施例1相同的锂二次电池制备方法，制备得到锂二次电池D3。
本发明对实施例1-7、对比例1-3提供的电解液以及锂二次电池进行性能测试，具体阐述如下：
1、电解液存储测试
将电解液放置在铝瓶中密封，铝瓶用铝塑膜真空封装，随后置于55度恒温箱中储存6天后取样测试其酸度，测试结果见表1。
2、锂二次电池高温循环测试
把锂二次电池搁置在45℃条件下，在2.8-4.4V的充放电压区间下使用1C电流进行充放电循环，记录初始容量为Q，循环400周后的容量为Q2，由如下公式计算其高温循环的容量保持率，测试结果见表1。
容量保持率(％)＝Q2/Q×100。
表1实施例1-7、对比例1-3提供的电解液以及锂二次电池的性能测试结果
样品 酸度 容量保持率
实施例1 21.67 96.5％
实施例2 23.57 94.7％
实施例3 24.52 93.1％
实施例4 24.14 93.5％
实施例5 27.34 95.27
实施例6 28.42 91.23
实施例7 20.48 90.06
对比例1 89.47 65.7％
对比例2 70.93 69.2％
对比例3 59.07 69.4％
由表1可知：实施例1-7提供的电解液的酸度明显低于对比例1-3中的酸度，并且使用该电解液制备得到的锂二次电池C1-C7的容量保持率也得到了显著的提升，因此，本发明提供的电解液具有良好的稳定性，并且使用该电解液可显著地提高锂二次电池的循环性能。
最后应说明的是：以上各实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述各实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的范围。

Claims (10)

  1. 一种电解液，包括有机溶剂和电解质，其特征在于，所述电解液还包括添加剂，所述添加剂包括式1所示的第一化合物，其中，R 1选自单键、取代或未取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 2、R 3独立的选自取代或未取代的烷氧基、C1-C6的亚烷基、C2-C6的烯基中的一种，R 4为B或P，
    Figure PCTCN2021079496-appb-100001
  2. 根据权利要求1所述的电解液，其特征在于，所述第一化合物为式1-1、式1-2、式1-3、式1-4所示化合物中的至少一种，
    Figure PCTCN2021079496-appb-100002
  3. 根据权利要求1所述的电解液，其特征在于，所述添加剂还包括第二化合物，所述第二化合物为腈类化合物、含硫化合物、磷酸酯化合物、硼酸酯化合物、锂盐类化合物、碳酸酯化合物中的一种或多种。
  4. 根据权利要求3所述的电解液，其特征在于，所述腈类化合物为丁二腈、戊二腈、已二腈、庚二腈、辛二腈、葵二腈、十八烷二腈、甘油三腈、乙二醇双(丙腈)醚、富马酸二腈、乙氧基五氟磷腈、1,3,6-己烷三腈中的一种或多种；
    和/或，所述含硫化合物为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；
    和/或，所述磷酸酯化合物为三(三甲基硅)磷酸酯、磷酸三烯丙基酯、磷酸三甲酯、磷酸三乙酯、磷酸三丙酯中的一种或多种；
    和/或，所述硼酸酯化合物为三(三甲基硅)硼酸酯、硼酸三甲酯中的一 种或多种；
    和/或，所述锂盐类化合物为二氟磷酸锂、双三氟甲基磺酰亚胺锂、双氟磺酰亚胺锂、二氟双草酸磷酸锂、二氟草酸硼酸锂、双草酸硼酸锂中的一种或多种；
    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。
  5. 根据权利要求1所述的电解液，其特征在于，所述第一化合物的质量为所述电解液质量的0.1-10％。
  6. 根据权利要求1所述的电解液，其特征在于，所述第一化合物的质量为所述电解液质量的0.2-2％。
  7. 根据权利要求3所述的电解液，其特征在于，所述第二化合物的质量为所述电解液质量的0.1-20％。
  8. 根据权利要求3所述的电解液，其特征在于，所述第二化合物的质量为所述电解液质量的1-6％。
  9. 一种根据权利要求1-8任一项所述的电解液的制备方法，其特征在于，将添加剂、电解质、有机溶剂混合得到所述电解液。
  10. 一种锂二次电池，其特征在于，包括权利要求1-8任一项所述的电解液。
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