WO2024037187A1 - 一种锂离子电池 - Google Patents

一种锂离子电池 Download PDF

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Publication number
WO2024037187A1
WO2024037187A1 PCT/CN2023/102556 CN2023102556W WO2024037187A1 WO 2024037187 A1 WO2024037187 A1 WO 2024037187A1 CN 2023102556 W CN2023102556 W CN 2023102556W WO 2024037187 A1 WO2024037187 A1 WO 2024037187A1
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Prior art keywords
negative electrode
ion battery
lithium
battery according
lithium ion
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PCT/CN2023/102556
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English (en)
French (fr)
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钱韫娴
胡时光
王勇
向晓霞
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深圳新宙邦科技股份有限公司
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Publication of WO2024037187A1 publication Critical patent/WO2024037187A1/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
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the invention belongs to the technical field of energy storage devices, and specifically relates to a lithium-ion battery.
  • Lithium-ion batteries have been widely used in 3C digital products such as mobile phones and laptops as well as new energy vehicles due to their advantages such as high operating voltage, wide operating temperature range, high energy density and power density, no memory effect and long cycle life. application.
  • 3C digital products such as mobile phones and laptops
  • new energy vehicles due to their advantages such as high operating voltage, wide operating temperature range, high energy density and power density, no memory effect and long cycle life. application.
  • the battery industry has increasingly required high energy density of lithium-ion batteries.
  • the battery's liquid retention capacity will also be reduced, causing the electrolyte to remain in the low pores It is difficult to penetrate the interface of the electrode plate, which in turn increases the internal contact resistance between the electrolyte and the electrode.
  • the charge and discharge polarization becomes larger, which may cause a sudden plunge due to lithium precipitation, and high voltage
  • the lithium ion conduction channel of the real electrode piece is tortuous, making it difficult to transport lithium ions, and thus the low-temperature performance of the battery is very poor.
  • the existing technology's method of increasing energy density will make it difficult to balance the high and low temperatures of the battery, and will cause the degradation of high-temperature cycle performance.
  • the present invention provides a lithium-ion battery.
  • the invention provides a lithium ion battery, including a positive electrode, a negative electrode and a non-aqueous electrolyte.
  • the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material containing lithium cobalt oxide, and the negative electrode includes a negative electrode current collector.
  • n 0 or 1
  • A is selected from C or O
  • X is selected from R 1 and R 2 are independent Selected from H, R 1 and R 2 are not selected from H at the same time, and X, R 1 and R 2 contain at least one sulfur atom;
  • the lithium-ion battery meets the following conditions:
  • m is the mass percentage content of the compound represented by Structural Formula 1 in the non-aqueous electrolyte, and the unit is %;
  • n is the mass of the single-sided negative electrode material layer per unit area of the negative electrode, and the unit is g/cm 2 ;
  • a is the specific surface area of the negative active material, in m 2 /g.
  • the weight percentage content of the carboxylic acid ester is 10% to 55%.
  • the lithium-ion battery meets the following conditions:
  • the mass percentage content m of the compound represented by Structural Formula 1 in the non-aqueous electrolyte is 0.1% to 3%.
  • the mass n of the single-sided negative electrode material layer per unit area of the negative electrode is 0.008 to 0.015g/cm 2 .
  • the specific surface area a of the negative active material is 0.7 to 1.6 m 2 /g.
  • the compound represented by the structural formula 1 is selected from one or more of the following compounds:
  • the carboxylic acid ester includes cyclic carboxylic acid ester and/or chain carbonic acid ester.
  • the additive also includes at least one of cyclic sulfate ester compounds, sultone compounds, cyclic carbonate compounds, phosphate ester compounds, borate ester compounds and nitrile compounds;
  • the content of the additive is 0.01% to 30%.
  • the cyclic sulfate compound is selected from vinyl sulfate, propylene sulfate, vinyl methyl sulfate, at least one of;
  • the sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone;
  • the cyclic carbonate compound is selected from vinylene carbonate, ethylene ethylene carbonate, methylene vinyl carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or structural formula At least one of the compounds shown in 2,
  • R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from one of hydrogen atoms, halogen atoms, and C1-C5 groups;
  • the phosphate compound is selected from at least one of tris(trimethylsilane)phosphate, tris(trimethylsilane)phosphite or the compound represented by structural formula 3:
  • R 31 , R 32 , and R 33 are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 ) 3 , and m is 1 to is a natural number of 3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group;
  • the borate compound is selected from at least one of tris(trimethylsilane)borate and tris(triethylsilane)borate;
  • the nitrile compound is selected from succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelonitrile, and sebaconitrile. of at least one.
  • lithium cobalt oxide is used as the positive electrode active material, so that the lithium ion battery has a higher energy density and a higher working voltage.
  • the compound represented by the structural formula 1 is added as an additive to the non-aqueous electrolyte of the ester solvent.
  • the mass percentage content m of the compound represented by the structural formula 1 in the non-aqueous electrolyte is adjusted, and the mass of the single-sided negative electrode material layer on the negative electrode per unit area is adjusted.
  • n and the specific surface area a of the negative active material can enable high-voltage and high-density lithium-ion batteries to achieve a balance of low-temperature and high-temperature performance.
  • the reason is that the compound represented by structural formula 1 participates in the film formation on the surface of the negative electrode.
  • the surface of the negative electrode is the main place where the compound represented by structural formula 1 plays a role. Therefore, the size of its reaction area has a great impact on the effect of the additive, and the negative electrode reaction area It is directly related to the mass n of the single-sided negative electrode material layer per unit area of the negative electrode and the specific surface area a of the negative electrode active material. If the negative electrode reaction area is small, the additive film will be too thick in the negative electrode area.
  • the carboxylic acid can be improved
  • the ester oxidation products are reduced at the negative electrode, but this results in high basic impedance, which is not conducive to the low-temperature performance of the battery; if the negative electrode reaction area is too large, the additive film cannot completely cover the negative electrode, and the carboxylic acid ester oxidation products cannot be effectively inhibited from forming on the negative electrode. Restore, battery high temperature performance is insufficient.
  • the inventor has concluded through extensive research that when the mass percentage content m of the compound represented by Structural Formula 1 in the non-aqueous electrolyte, the mass n of the single-sided negative electrode material layer per unit area of the negative electrode, and the specific surface area a of the negative active material satisfy the relationship When formula 1.5 ⁇ m/(n*a) ⁇ 600, and 0.05 ⁇ m ⁇ 5, 0.006 ⁇ n ⁇ 0.02, 0.6 ⁇ a ⁇ 2, the lithium-ion battery has good performance under high and low temperature conditions.
  • Embodiments of the present invention provide a lithium ion battery, including a positive electrode, a negative electrode and a non-aqueous electrolyte.
  • the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material containing lithium cobalt oxide, and the negative electrode includes a negative electrode.
  • the negative electrode material layer includes a negative electrode active material.
  • the non-aqueous electrolyte includes a non-aqueous organic solvent, a lithium salt and an additive.
  • the non-aqueous organic solvent includes Carboxylic acid ester, the additive includes a compound represented by structural formula 1:
  • n 0 or 1
  • A is selected from C or O
  • X is selected from R 1 and R 2 are each independently selected from H, R 1 and R 2 are not selected from H at the same time, and X, R 1 and R 2 contain at least one sulfur atom;
  • the lithium-ion battery meets the following conditions:
  • m is the mass percentage content of the compound represented by Structural Formula 1 in the non-aqueous electrolyte, and the unit is %;
  • n is the mass of the single-sided negative electrode material layer per unit area of the negative electrode, and the unit is g/cm 2 ;
  • a is the specific surface area of the negative active material, in m 2 /g.
  • the lithium-ion battery uses lithium cobalt oxide as the cathode active material, so that the lithium-ion battery has a higher energy density and a higher operating voltage.
  • the compound represented by structural formula 1 is added as an additive to the aqueous electrolyte.
  • the mass percentage content m of the compound represented by structural formula 1 in the non-aqueous electrolyte is adjusted, the mass n of the single-sided negative electrode material layer on the negative electrode per unit area and the negative electrode activity
  • the relationship between the specific surface area a of the material can enable high-voltage and high-density lithium-ion batteries to achieve a balance of low-temperature and high-temperature performance.
  • the reason is that the compound represented by structural formula 1 participates in the film formation on the surface of the negative electrode.
  • the surface of the negative electrode is the main place where the compound represented by structural formula 1 plays a role.
  • the size of its reaction area has a great impact on the effect of the additive, and the negative electrode reaction area It is directly related to the mass n of the single-sided negative electrode material layer per unit area of the negative electrode and the specific surface area a of the negative electrode active material. If the negative electrode reaction area is small, the additive film will be too thick in the negative electrode area. Although the carboxylic acid can be improved The reduction of ester solvent oxidation products in the negative electrode will cause high basic impedance, which is not conducive to the low-temperature performance of the battery. If the negative electrode reaction area is too large, the additive film cannot completely cover the negative electrode, and the carboxylic acid ester oxidation products cannot be effectively inhibited from forming on the negative electrode.
  • the inventor has concluded through extensive research that when the mass percentage content m of the compound represented by structural formula 1 in the non-aqueous electrolyte, the mass n of the single-sided negative electrode material layer per unit area of the negative electrode, and the specific surface area a of the negative electrode active material satisfy the relationship When formula 1.5 ⁇ m/(n*a) ⁇ 600, and 0.05 ⁇ m ⁇ 5, 0.006 ⁇ n ⁇ 0.02, and 0.6 ⁇ a ⁇ 2, the lithium-ion battery has good performance under both high and low temperature conditions.
  • the compound represented by the structural formula 1 is:
  • A is selected from C or O
  • X is selected from R 1 and R 2 are each independently selected from H, R 1 and R 2 are not simultaneously selected from H, and X, R 1 and R 2 contain at least one sulfur atom.
  • the compound represented by the structural formula 1 is:
  • A is selected from C or O
  • X is selected from R 1 and R 2 are each independently selected from H, R 1 and R 2 are not simultaneously selected from H, and X, R 1 and R 2 contain at least one sulfur atom.
  • the weight percentage content of the carboxylic acid ester is 10% to 55%.
  • the weight percentage content of the carboxylic acid ester can be 10%, 11%, 13%, 15%, 18%, 20%, 23%, 27%, 30%, 33%, 37%, 40%, 43%, 47%, 50% or 55%.
  • the weight percentage content of the carboxylic acid ester is 15% to 50%.
  • Carboxylic acid esters have the characteristics of high dielectric constant and low viscosity. Adding carboxylic acid esters to the non-aqueous electrolyte is beneficial to improving the low temperature and fast charging performance of the battery.
  • carboxylic acid esters are unstable at high voltages and are prone to forming in the positive electrode. Decomposition products are produced on the side, especially when the decomposition products migrate to the negative electrode and are reduced, causing the loss of active Li and causing the battery impedance to increase, thus degrading the capacity after storage.
  • the content of the carboxylic acid ester is within the above range, the low-temperature performance of the battery can be better improved.
  • the single-sided negative electrode per unit area of the negative electrode The adjustment of the mass n of the material layer and the specific surface area a of the negative active material is conducive to the formation of a stable interface film on the surface of the negative electrode, thereby making the non-aqueous electrolyte with carboxylic acid esters still have better performance under high temperature and high voltage conditions. Good cycle performance.
  • the lithium-ion battery meets the following conditions:
  • the mass percentage content m of the compound represented by Structural Formula 1 in the non-aqueous electrolyte, the mass n of the single-sided negative electrode material layer per unit area of the negative electrode, and the specific surface area a of the negative electrode active material can be further integrated for battery performance. influence, improving the low-temperature performance and high-temperature performance of lithium-ion batteries.
  • the mass percentage content m of the compound represented by Structural Formula 1 in the non-aqueous electrolyte solution can be 0.05%, 0.08%, 0.1%, 0.2%, 0.4%, 0.5%, 0.7%, 0.9% , 1.0%, 1.1%, 1.3%, 1.5%, 1.8%, 2.0%, 2.3%, 2.7%, 3.0%, 3.3%, 3.7%, 4.0%, 4.3%, 4.7% or 5.0%
  • the mass percentage content m of the compound represented by Structural Formula 1 in the non-aqueous electrolyte is 0.1% to 3%.
  • the content of the compound shown in Structural Formula 1 is related to the thickness of the interface film formed on the surface of the negative electrode material layer.
  • the content of the compound shown in Structural Formula 1 in the non-aqueous electrolyte is within the above range, it is beneficial to form a layer on the surface of the negative electrode material layer.
  • An interface film with a suitable thickness and stability can effectively inhibit the decomposition of carboxylate esters in the non-aqueous electrolyte, while avoiding the impact of an excessively thick interface film on the low-temperature impedance of the battery.
  • the mass n of the single-sided negative electrode material layer on the negative electrode per unit area can be 0.006g/cm 2 , 0.007g/cm 2 , 0.008g/cm 2 , 0.009g/cm 2 , 0.01g/ cm 2 , 0.011g/cm 2 , 0.012g/cm 2 , 0.013g/cm 2 , 0.014g/cm 2 , 0.015g/cm 2 , 0.017g/ cm 2 , 0.018g/cm 2 or 0.02g/cm 2 .
  • the mass n of the single-sided negative electrode material layer per unit area of the negative electrode is 0.008-0.015g/cm 2 .
  • the mass n of the single-sided negative electrode material layer per unit area of the negative electrode decreases, it is beneficial to improve the diffusion efficiency of the non-aqueous electrolyte inside the pores of the negative electrode material layer; thereby improving its ion conductivity, which is beneficial to reducing the energy consumption of lithium-ion batteries. Impedance at low temperatures.
  • the reduction of the mass n of the single-sided negative electrode material layer per unit area of the negative electrode will also lead to a decrease in the energy density of the battery, affect the stability of the negative electrode material, and easily lead to the problem of negative electrode powdering; while the single-sided negative electrode per unit area of the negative electrode will The larger the mass n of the material layer is, it is beneficial to increase the energy density of the battery, but it is not conducive to the infiltration of the non-aqueous electrolyte. The kinetics of the lithium-ion battery becomes worse, which affects the high-temperature performance of the lithium-ion battery.
  • the mass n of the single-sided negative electrode material layer per unit area of the negative electrode falls within the above-mentioned preferred range, the kinetic performance of the battery can be better improved, so that the lithium-ion battery has higher energy density and ion conductivity.
  • the specific surface area a of the negative active material can be 0.6m 2 /g, 0.7m 2 /g, 0.8m 2 /g, 0.9m 2 /g, 1.0m 2 / g, 1.1m 2 /g, 1.2m 2 / g, 1.3m 2 /g, 1.4m 2 /g, 1.5m 2 /g, 1.6m 2 /g, 1.7m 2 /g, 1.8m 2 /g , 1.9m 2 / g or 2m 2 /g.
  • the specific surface area a of the negative active material is 0.7 to 1.6 m 2 /g.
  • the deintercalation reaction of lithium ions mainly occurs at the interface of the negative active material/non-aqueous electrolyte.
  • the increase in specific surface area can also easily lead to insufficient structural strength of the negative electrode material layer, causing the material to fall off. The problem also aggravates the decomposition of the non-aqueous electrolyte.
  • the specific surface area a of the negative active material also directly affects the film thickness of the compound represented by structural formula 1 per unit mass on the surface of the negative electrode material layer, which is related to non-aqueous electrolysis.
  • the contents of the compounds represented by structural formula 1 in the liquid are related to each other.
  • the compound represented by Structural Formula 1 is selected from one or more of the following compounds:
  • the lithium-ion battery is a pouch battery or a hard-shell battery.
  • the cathode further includes a cathode current collector, and the cathode material layer is formed on the surface of the cathode current collector.
  • the positive current collector is selected from metal materials that can conduct electrons.
  • the positive current collector includes at least one of Al, Ni, tin, copper, and stainless steel.
  • the positive current collector choose from aluminum foil.
  • the cathode material layer further includes a cathode binder and a cathode conductive agent.
  • the positive electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, tetrafluoroethylene- Copolymer of perfluoroalkyl vinyl ether, copolymer of ethylene-tetrafluoroethylene, copolymer of vinylidene fluoride-tetrafluoroethylene, copolymer of vinylidene fluoride-trifluoroethylene, copolymer of vinylidene fluoride-trichloroethylene Copolymers, vinylidene fluoride-fluorovinyl copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, thermoplastic polyimides, polyethylene and poly
  • the positive conductive agent includes at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene or reduced graphene oxide.
  • the negative active material includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode.
  • the carbon-based negative electrode can include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.
  • the silicon-based negative electrode can include silicon materials, silicon oxides, silicon-carbon composite materials, silicon alloy materials, etc.
  • the tin-based negative electrode can It can include tin, tin carbon, tin oxide, and tin metal compounds
  • the lithium negative electrode can include metallic lithium or lithium alloy.
  • the lithium alloy may specifically be at least one of lithium silicon alloy, lithium sodium alloy, lithium potassium alloy, lithium aluminum alloy, lithium tin alloy and lithium indium alloy.
  • the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.
  • the selectable ranges of the negative electrode binder and the negative electrode conductive agent are the same as those of the positive electrode binder and the positive electrode conductive agent respectively, and will not be described again here.
  • the negative electrode further includes a negative electrode current collector, and the negative electrode material layer is formed on the surface of the negative electrode current collector.
  • the negative electrode current collector is selected from metal materials that can conduct electrons.
  • the negative electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel.
  • the negative electrode current collector Selected from copper foil.
  • the carboxylic acid esters include cyclic carboxylic acid esters and/or chain carbonic acid esters.
  • Examples of the cyclic carboxylic acid ester include at least one kind selected from ⁇ -butyrolactone, ⁇ -valerolactone, and ⁇ -valerolactone.
  • Examples of chain carbonates include: methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate, At least one of ethyl fluoroacetate.
  • the non-aqueous organic solvent further includes at least one of ether solvents, nitrile solvents, carbonate solvents and sulfone solvents.
  • ether solvents include cyclic ethers or chain ethers and their fluorinated products, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms.
  • Cyclic ethers are specifically It can be but is not limited to 1,3-dioxopentane (DOL), 1,4-dioxane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH 3 -THF) , at least one of 2-trifluoromethyltetrahydrofuran (2-CF 3 -THF);
  • the chain ether can be, but is not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxy Methane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether.
  • chain ethers have high solvating power with lithium ions and can improve ion dissociation
  • dimethoxymethane, diethoxymethane, and ethoxymethoxy are particularly preferred because they have low viscosity and can impart high ionic conductivity.
  • Methane One type of ether compound may be used alone, or two or more types of ether compounds may be used in any combination and ratio.
  • the content of the ether compound is not particularly limited and is arbitrary within the range that does not significantly damage the effect of the high-pressure lithium ion battery of the present invention. When the non-aqueous solvent volume ratio is 100%, the volume ratio is usually 1% or more, and the volume ratio is preferred.
  • the volume ratio is 2% or more, and more preferably the volume ratio is 3% or more. In addition, the volume ratio is usually The volume ratio is 30% or less, preferably the volume ratio is 25% or less, and more preferably the volume ratio is 20% or less.
  • the total amount of the ether compounds may satisfy the above range.
  • the content of the ether compound is within the above-mentioned preferred range, it is easy to ensure the improvement effect of the ion conductivity by increasing the lithium ion dissociation degree and reducing the viscosity of the chain ether.
  • the negative electrode active material is a carbon-based material, the phenomenon of co-intercalation of chain ether and lithium ions can be suppressed, so the input-output characteristics and charge-discharge rate characteristics can be achieved within an appropriate range.
  • the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.
  • the carbonate solvent includes cyclic carbonate or chain carbonate.
  • the cyclic carbonate can be, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), and ⁇ -butyrolactone. At least one of (GBL) and butylene carbonate (BC); the chain carbonate can be, but is not limited to, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), At least one of dipropyl carbonate (DPC).
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate
  • the content of the cyclic carbonate is not particularly limited and is arbitrary within the range that does not significantly damage the effect of the lithium ion battery of the present invention.
  • the lower limit of the content is relative to the total amount of solvent in the non-aqueous electrolyte.
  • the volume ratio is usually 3% or more, and preferably the volume ratio is 5% or more.
  • the upper limit of the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less.
  • the content of the chain carbonate is not particularly limited, but is usually 15% or more by volume, preferably 20% or more by volume, and more preferably 25% or more by volume relative to the total amount of solvent in the non-aqueous electrolyte solution.
  • the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less.
  • the viscosity of the non-aqueous electrolyte solution can be easily brought into an appropriate range, thereby suppressing a decrease in ion conductivity, thereby contributing to bringing the output characteristics of the non-aqueous electrolyte battery into a favorable range.
  • the total amount of the linear carbonates may satisfy the above range.
  • chain carbonates having fluorine atoms may also be preferably used.
  • the number of fluorine atoms contained in the fluorinated linear carbonate is not particularly limited as long as it is 1 or more, but it is usually 6 or less, preferably 4 or less.
  • these fluorine atoms may be bonded to the same carbon or to different carbons.
  • the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.
  • the sulfone solvent includes cyclic sulfone and chain sulfone.
  • cyclic sulfone it usually has 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms.
  • chain sulfone In the case of sulfone, it is usually a compound having 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms.
  • the content of the sulfone solvent is not particularly limited and is arbitrary as long as it does not significantly damage the effect of the lithium-ion battery of the present invention.
  • the volume ratio relative to the total amount of solvent in the non-aqueous electrolyte is usually 0.3% or more, and preferably the volume ratio is 0.5.
  • the volume ratio is 1% or more.
  • the volume ratio is usually 40% or less, preferably 35% or less, and more preferably 30% or less.
  • the lithium salt is selected from LiPF 6 , LiBOB, LiDFOB, LiPO 2 F 2 , LiBF 4 , LiSbF 6 , LiAsF 6 , 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 , LiClO 4 , LiAlCl 4 , LiCF 3 SO 3 , Li 2 B 10 Cl 10 , LiSO 2 F, LiTOP (lithium trioxalate phosphate), At least one of LiDODFP (lithium difluorodioxalate phosphate), LiOTFP (lithium tetrafluorooxalate phosphate) and lower aliphatic carboxylic acid lithium salt.
  • LiPF 6 LiBOB, LiDFOB, LiPO 2 F 2 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiN(SO 2 CF 3 ) 2 ,
  • the concentration of the lithium salt in the non-aqueous electrolyte is 0.1 mol/L to 8 mol/L. In a preferred embodiment, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol/L to 2.5 mol/L. Specifically, in the non-aqueous electrolyte solution, the concentration of the lithium salt can be 0.5 mol/L, 1 mol/L, 1.5 mol/L, 2 mol/L, or 2.5 mol/L.
  • the additives further include cyclic sulfate compounds, sultone compounds, cyclic carbon At least one of acid ester compounds, phosphate ester compounds, borate ester compounds and nitrile compounds;
  • the content of the additive is 0.01% to 30%.
  • the cyclic sulfate compound is selected from vinyl sulfate, propylene sulfate, vinyl methyl sulfate, at least one of;
  • the sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone;
  • the cyclic carbonate compound is selected from vinylene carbonate, ethylene ethylene carbonate, methylene vinyl carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or structural formula At least one of the compounds shown in 2,
  • R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from one of hydrogen atoms, halogen atoms, and C1-C5 groups;
  • the phosphate compound is selected from at least one of tris(trimethylsilane)phosphate, tris(trimethylsilane)phosphite or the compound represented by structural formula 3:
  • R 31 , R 32 , and R 33 are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 ) 3 , and m is 1 to is a natural number of 3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group;
  • the phosphate compound represented by the structural formula 3 may be tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, or dipropargyl propyl phosphate.
  • Phosphate ester dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, Dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallylethyl phosphate, diallyl propyl phosphate, diallyl triphosphate Fluoromethylphosphate, diallyl-2,2,2-trifluoroethylphosphate, diallyl-3,3,3-trifluoropropylphosphate, diallylhexafluoroisopropyl At least one of the base phosphates;
  • the borate compound is selected from at least one of tris(trimethylsilane)borate and tris(triethylsilane)borate;
  • the nitrile compound is selected from succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelonitrile, and sebaconitrile. of at least one.
  • the additives may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, specifically flame retardant additives such as fluorinated phosphates, cyclophosphazene, or tert-amylbenzene. , tert-butylbenzene and other anti-overcharge additives.
  • the content of any optional substance in the additive in the non-aqueous electrolyte is less than 10%, preferably, the content is 0.1-5%, and more preferably, The content is 0.1% to 2%.
  • the content of any optional substance in the additive can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5% , 9%, 9.5%, 10%.
  • the content of the fluorinated ethylene carbonate is 0.05% to 30% based on the total mass of the non-aqueous electrolyte being 100%.
  • the lithium ion battery further includes a separator, and the separator is located between the positive electrode and the negative electrode.
  • the separator can be an existing conventional separator, and can be a ceramic separator, a polymer separator, a non-woven fabric, an inorganic-organic composite separator, etc.
  • the polymer separator is selected from the group consisting of polyolefins, polyamides, polysulfones, and polyesters.
  • One or more of phosphazenes, polyethersulfones, polyetheretherketones, polyetheramides and polyacrylonitriles including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene ), double-layer PP/PE, double-layer PP/PP and three-layer PP/PE/PP separators.
  • the separator includes a base separator and a surface coating.
  • the surface coating is inorganic particles or organic gels or a mixture of the two and is coated on at least one side surface of the base separator.
  • This example is used to illustrate the preparation method of the lithium-ion battery disclosed in the present invention, which includes the following steps:
  • cathode active material lithium cobalt oxide LiCoO 2 , conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF), and then disperse them in N-methyl-2-pyrrolidone (NMP) to obtain the cathode slurry.
  • NMP N-methyl-2-pyrrolidone
  • the slurry is evenly coated on both sides of the aluminum foil, dried, rolled and vacuum dried, and the aluminum lead wire is welded with an ultrasonic welder to obtain a positive plate with a thickness of 120-150 ⁇ m.
  • the slurry is coated on both sides of the copper foil, dried, rolled and vacuum dried, and a nickel lead wire is welded with an ultrasonic welder to obtain a negative plate.
  • the thickness of the plate is 120-150 ⁇ m, where the negative electrode per unit area
  • the mass of the upper single-sided negative electrode material layer and the specific surface area of the negative electrode active material are shown in Table 2.
  • the nonaqueous electrolyte prepared above was injected into the battery core, sealed in a vacuum, and left to rest for 24 hours.
  • Examples 2 to 33 are used to illustrate the lithium-ion battery and its preparation method disclosed in the present invention, including most of the operating steps in Example 1, and the differences are:
  • Comparative Examples 1 to 14 are used to comparatively illustrate the lithium-ion battery disclosed in the present invention and its preparation method, including most of the operating steps in Example 1, and the differences are:
  • Battery capacity retention rate (%) retention capacity/initial discharge capacity ⁇ 100%;.
  • the electrolyte contains a carboxylate solvent, and the compound represented by Structural Formula 1 is added as The additive satisfies the condition 1.5 ⁇ m/(n* by controlling the mass percentage content m of the compound represented by structural formula 1 in the non-aqueous electrolyte, the mass n of the single-sided negative electrode material layer per unit area of the negative electrode, and the specific surface area a of the negative electrode active material.
  • the obtained lithium ion battery has a high capacity retention rate under low temperature conditions and also has the same capacity after high temperature storage.
  • the higher capacity retention rate shows that the reaction area of the negative electrode material layer can be changed by regulating the mass n of the single-sided negative electrode material layer per unit area of the negative electrode and the specific surface area a of the negative electrode active material, thereby affecting the reaction area of the compound represented by structural formula 1.
  • the film-forming effect on the surface of the negative electrode material layer makes the negative electrode reaction area and the structural formula 1 in the non-aqueous electrolyte
  • the content of the compounds shown is matched to obtain a moderately thick and stable interfacial film, which can effectively inhibit the decomposition of carboxylic acid esters, reduce the increase in impedance of lithium-ion batteries under low temperature conditions, and at the same time improve the performance of non-aqueous electrolytes under high temperature conditions. stability to avoid the decomposition of non-aqueous electrolyte, thereby enabling lithium-ion batteries to have better performance under high and low temperature conditions.
  • n and the specific surface area a of the negative active material ensures sufficient pore channels in the negative electrode material layer, improves the infiltration effect of the non-aqueous electrolyte on the negative electrode material layer, thereby reducing impedance and improving ion conduction efficiency under low temperature conditions. , thereby improving the low-temperature capacity retention rate.
  • Comparative Examples 8 and 9 it can be seen from Comparative Examples 8 and 9 that the content of the compound represented by Structural Formula 1 is too low, and the effect on improving battery performance is not obvious, and the high-temperature capacity retention rate of the battery is low; the content of the compound represented by Structural Formula 1 is too high, It will lead to excessive film thickness, which will lead to an increase in low-temperature impedance, leading to the problem of battery low-temperature performance degradation. It can be seen from Comparative Examples 10 to 13 that the mass n of the single-sided negative electrode material layer per unit area of the negative electrode or the specific surface area a of the negative electrode active material is too low, which will cause the compound represented by Structural Formula 1 to form a film on a limited reaction area.
  • the film thickness is too large, affecting the low-temperature performance of the battery; the mass n of the single-sided negative electrode material layer per unit area of the negative electrode or the specific surface area a of the negative active material is too high, resulting in the compound film shown in structural formula 1 being unable to cover the negative active material On the surface, non-aqueous electrolyte side reactions increase, which affects the high-temperature cycle performance of the battery and also leads to insufficient low-temperature performance.
  • the above shows that the m value, n value or a value has a strong correlation in improving the high and low temperature performance of lithium-ion batteries.
  • Example 11 The test results obtained in Example 11 and Examples 22 to 26 are filled in Table 4.
  • Example 11 (4) The test results obtained in Example 11 and Examples 30 to 33 are filled in Table 6.

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Abstract

一种锂离子电池，包括正极、负极和非水电解液，所述正极包括正极材料层，所述正极材料层包括含有钴酸锂的正极活性材料，所述负极包括负极集流体以及形成于所述负极集流体上的负极材料层，所述负极材料层包括负极活性材料，所述非水电解液包括非水有机溶剂、锂盐和添加剂，所述非水有机溶剂包括羧酸酯。该锂离子电池在高温和低温条件下均具有较好的表现性能。

Description

一种锂离子电池 技术领域
本发明属于储能装置技术领域，具体涉及一种锂离子电池。
背景技术
锂离子电池因其具有工作电压高、工作温度范围广、能量密度和功率密度大、无记忆效应和循环寿命长等优点，在手机、笔记本电脑等3C数码产品领域以及新能源汽车得到了广泛的应用。近年来，随着3C数码产品轻薄化的不断发展，电池行业越来越要求锂离子电池高能量密度化。
目前提高电池能量密度的方法主要有两种，一是提高正极充电截止电压，二是对电极的活性物质层进行加压来实现高密度化。但是，提高正极充电截止电压以后，正极的活性会进一步提高，正极和电解液之间的副反应也会随之加剧，会导致正极过渡金属离子溶出，从而造成电池高温性能劣化。另外，采用高压实的电极，可提高极片的负载量，进而提升电池整体的能量密度，但由于高压实电极孔隙率低，电池的保液量也会降低，使电解液在低孔隙率极片界面渗透困难，进而使电解液与电极之间的接触内阻增大，在长期循环过程中，充放电极化变大，会造成因出现析锂而突然跳水的情况，并且高压实极片锂离子传导通道曲折，造成锂离子传输困难，从而电池的低温性能液很差。综上，现有技术提升能量密度的方式会使电池的高低温难以兼顾，以及高温循环性能的劣化。因此，如何使高电压、高压实锂离子电池兼顾高低温性能，并同时具有良好的快充性能是一项行业难题，需要从电极材料、电解液等各个层面进行改进。从电解液角度，现有技术常在溶剂上常选择介电常数高、粘度小的羧酸酯体系以改善电池的低温和快充性能，但羧酸酯在高电压下不稳定，易在正极侧产生分解产物，而分解产物迁移至负极又会被还原，造成活性Li损失，并造成电池阻抗增长，从而劣化存储后的容量发挥，难以满足需求。
发明内容
针对现有高电压、高压实锂离子电池难以兼顾高低温性能的问题，本发明提供了一种锂离子电池。
本发明解决上述技术问题所采用的技术方案如下：
本发明提供了一种锂离子电池，包括正极、负极和非水电解液，所述正极包括正极材料层，所述正极材料层包括含有钴酸锂的正极活性材料，所述负极包括负极集流体以及形成于所述负极集流体上的负极材料层，所述负极材料层包括负极活性材料，所述非水电解液包括非水有机溶剂、锂盐和添加剂，所述非水有机溶剂包括羧酸酯，所述添加剂包括结构式1所示的化合物：
其中，n为0或1，A选自C或O，X选自R1、R2各自独立 选自H、R1和R2不同时选自H，且X、R1和R2中至少含有一个硫原子；
所述锂离子电池满足以下条件：
1.5≤m/(n*a)≤600，且0.05≤m≤5，0.006≤n≤0.02，0.6≤a≤2；
其中，m为非水电解液中结构式1所示的化合物的质量百分比含量，单位为％；
n为单位面积负极上单面负极材料层的质量，单位为g/cm2；
a为负极活性材料的比表面积，单位为m2/g。
可选的，以所述非水电解液的总质量为100％计，所述羧酸酯的重量百分比含量为10％～55％。
可选的，所述锂离子电池满足以下条件：
5≤m/(n*a)≤300。
可选的，所述非水电解液中结构式1所示的化合物的质量百分比含量m为0.1％～3％。
可选的，所述单位面积负极上单面负极材料层的质量n为0.008～0.015g/cm2。
可选的，所述负极活性材料的比表面积a为0.7～1.6m2/g。
可选的，所述结构式1所示的化合物选自以下化合物中的一种或多种：


可选的，所述羧酸酯包括环状羧酸酯和/或链状碳酸酯。
可选的，所述添加剂还包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、磷酸酯类化合物、硼酸酯类化合物和腈类化合物中的至少一种；
以所述非水电解液的总质量为100％计，所述添加剂的含量为0.01％～30％。
可选的，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯、甲基硫酸乙烯酯、中的至少一种；
所述磺酸内酯类化合物选自1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯、1,3-丙烯磺酸内酯中的至少一种；
所述环状碳酸酯类化合物选自碳酸亚乙烯酯、碳酸乙烯亚乙酯、亚甲基碳酸乙烯酯、氟代碳酸乙烯酯、三氟甲基碳酸乙烯酯、双氟代碳酸乙烯酯或结构式2所示化合物中的至少一种，

所述结构式2中，R21、R22、R23、R24、R25、R26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
所述磷酸酯类化合物选自三(三甲基硅烷)磷酸酯、三(三甲基硅烷)亚磷酸酯或结构式3所示化合物中的至少一种：
所述结构式3中，R31、R32、R33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(CmH2m+1)3，m为1～3的自然数，且R31、R32、R33中至少有一个为不饱和烃基；
所述硼酸酯类化合物选自三(三甲基硅烷)硼酸酯和三(三乙基硅烷)硼酸酯中的至少一种；
所述腈类化合物选自丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的至少一种。
根据本发明提供的锂离子电池，采用了钴酸锂作为正极活性材料，使锂离子电池具有较高的能量密度和较高的工作电压，发明人通过大量研究创新性的发现，在含有羧酸酯溶剂的非水电解液中加入结构式1所示的化合物作为添加剂，同时，通过调整非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a之间的关系，可使高电压和高压实的锂离子电池达到低温及高温性能的平衡。原因在于，结构式1所示的化合物参与负极的表面成膜，负极的表面是结构式1所示的化合物发挥作用的主要场所，因此其反应面积大小对添加剂作用效果有很大影响，而负极反应面积与单位面积负极上单面负极材料层的质量n和负极活性材料的比表面积a直接相关，若负极反应面积小，则添加剂成膜在所述负极区域内成膜过厚，虽然可以改善羧酸酯氧化产物在负极的还原，但其造成基础阻抗高，不利于电池的低温性能；若负极反应面积过大，则添加剂成膜无法完全覆盖负极，则无法有效抑制羧酸酯氧化产物在负极的还原，电池高温性能不足。因此本发明人通过大量研究总结发现，当非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a满足关系式1.5≤m/(n*a)≤600，且0.05≤m≤5，0.006≤n≤0.02，0.6≤a≤2时，锂离子电池在高温和低温条件下均具有较好的表现性能。
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、负极和非水电解液，所述正极包括正极材料层，所述正极材料层包括含有钴酸锂的正极活性材料，所述负极包括负极集流体以及形成于所述负极集流体上的负极材料层，所述负极材料层包括负极活性材料，所述非水电解液包括非水有机溶剂、锂盐和添加剂，所述非水有机溶剂包括羧酸酯，所述添加剂包括结构式1所示的化合物：
其中，n为0或1，A选自C或O，X选自R1、R2各自独立选自H、R1和R2不同时选自H，且X、R1和R2中至少含有一个硫原子；
所述锂离子电池满足以下条件：
1.5≤m/(n*a)≤600，且0.05≤m≤5，0.006≤n≤0.02，0.6≤a≤2；
其中，m为非水电解液中结构式1所示的化合物的质量百分比含量，单位为％；
n为单位面积负极上单面负极材料层的质量，单位为g/cm2；
a为负极活性材料的比表面积，单位为m2/g。
所述锂离子电池采用了钴酸锂作为正极活性材料，使锂离子电池具有较高的能量密度和较高的工作电压，发明人通过大量研究创新性的发现，在含有羧酸酯溶剂的非水电解液中加入结构式1所示的化合物作为添加剂，同时，通过调整非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a之间的关系，可使高电压和高压实的锂离子电池达到低温及高温性能的平衡。原因在于，结构式1所示的化合物参与负极的表面成膜，负极的表面是结构式1所示的化合物发挥作用的主要场所，因此其反应面积大小对添加剂作用效果有很大影响，而负极反应面积与单位面积负极上单面负极材料层的质量n和负极活性材料的比表面积a直接相关，若负极反应面积小，则添加剂成膜在所述负极区域内成膜过厚，虽然可以改善羧酸酯溶剂氧化产物在负极的还原，但其造成基础阻抗高，不利于电池的低温性能；若负极反应面积过大，则添加剂成膜无法完全覆盖负极，则无法有效抑制羧酸酯氧化产物在负极的还原，电池高温性能不足。因此本发明人通过大量研究总结发现，当非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a满足关系式1.5≤m/(n*a)≤600，且0.05≤m≤5，0.006≤n≤0.02，0.6≤a≤2时，锂离子电池在高温和低温条件下均具有较好的表现性能。
在一些实施例中，当n为0时，所述结构式1所示的化合物为：
其中，A选自C或O，X选自R1、R2各自独立选自H、R1和R2不同时选自H，且X、R1和R2中至少含有一个硫原子。
在一些实施例中，当n为1时，所述结构式1所示的化合物为：
其中，A选自C或O，X选自R1、R2各自独立选自H、R1和R2不同时选自H，且X、R1和R2中至少含有一个硫原子。
在一些实施例中，以所述非水电解液的总质量为100％计，所述羧酸酯的重量百分比含量为10％～55％。
具体的，以所述非水电解液的总质量为100％计，所述羧酸酯的重量百分比含量可以为10％、11％、13％、15％、18％、20％、23％、27％、30％、33％、37％、40％、43％、47％、50％或55％。
在优选的实施例中，以所述非水电解液的总质量为100％计，所述羧酸酯的重量百分比含量为15％～50％。
羧酸酯具有介电常数高、粘度小的特点，在非水电解液中加入羧酸酯，有利于改善电池的低温和快充性能，但羧酸酯在高电压下不稳定，易在正极侧产生分解产物，特别的是分解产物迁移至负极又会被还原，造成活性Li损失，并造成电池阻抗增长，从而劣化存储后的容量发挥。当羧酸酯的含量处于上述范围中时，能够较好的提升电池的低温性能，同时通过上述对于非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a的调整，有利于在负极表面形成稳定的界面膜，进而使加入有羧酸酯的非水电解液在高温、高电压的条件下仍具有较好的循环性能。
在优选的实施例中，所述锂离子电池满足以下条件：
5≤m/(n*a)≤300。
通过上述关系式的限定，能够进一步综合非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a对于电池性能的影响，提高锂离子电池的低温性能和高温性能。
在具体的实施例中，所述非水电解液中结构式1所示的化合物的质量百分比含量m可以为0.05％、0.08％、0.1％、0.2％、0.4％、0.5％、0.7％、0.9％、1.0％、1.1％、1.3％、1.5％、1.8％、2.0％、2.3％、2.7％、3.0％、3.3％、3.7％、4.0％、4.3％、4.7％或5.0％
在优选的实施例中，所述非水电解液中结构式1所示的化合物的质量百分比含量m为0.1％～3％。
结构式1所示的化合物含量与其在负极材料层表面形成的界面膜厚度相关，当非水电解液中结构式1所示的化合物的含量处于上述范围内时，有利于在负极材料层表面形成一层厚度适合且稳定的界面膜，有效地抑制非水电解液中羧酸酯的分解，同时避免界面膜过厚对于电池低温阻抗的影响。
在具体的实施例中，所述单位面积负极上单面负极材料层的质量n可以为0.006g/cm2、0.007g/cm2、0.008g/cm2、0.009g/cm2、0.01g/cm2、0.011g/cm2、0.012g/cm2、0.013g/cm2、0.014g/cm2、0.015g/cm2、0.017g/cm2、0.018g/cm2或0.02g/cm2。
在优选的实施例中，所述单位面积负极上单面负极材料层的质量n为0.008～0.015g/cm2。
随着单位面积负极上单面负极材料层的质量n的减小，有利于提高非水电解液在负极材料层的孔隙内部的扩散效率；进而提高其离子传导能力，有利于减低锂离子电池在低温下的阻抗。同时，单位面积负极上单面负极材料层的质量n的减小也会导致电池的能量密度的下降，影响负极材料的稳定性，易导致负极粉化的问题；而单位面积负极上单面负极材料层的质量n越大，有利于提高电池能量密度，但不利于非水电解液的浸润，锂离子电池动力学变差，影响锂离子电池的高温性能。因此，单位面积负极上单面负极材料层的质量n落入上述优选范围内时，可以更好地提升电池动力学性能，使锂离子电池具备较高的能量密度和离子传导能力。
在具体的实施例中，所述负极活性材料的比表面积a可以为0.6m2/g、0.7m2/g、0.8m2/g、0.9m2/g、1.0m2/g、1.1m2/g、1.2m2/g、1.3m2/g、1.4m2/g、1.5m2/g、1.6m2/g、1.7m2/g、1.8m2/g、1.9m2/g或2m2/g。
在优选的实施例中，所述负极活性材料的比表面积a为0.7～1.6m2/g。
锂离子的脱嵌反应主要集中在负极活性材料/非水电解液界面上进行，负极活性材料的比表面积越大，在相同的表观体积和有机非水电解液能够充分润湿的前提下，电极/非水电解液界面也就越大，锂离子的脱嵌速度也就越快，负极的离子传导能力越高，但是比表面积增大也容易导致负极材料层的结构强度不足，导致材料脱落的问题，也加剧了非水电解液的分解，同时，所述负极活性材料的比表面积a也直接影响单位质量的结构式1所示的化合物对于负极材料层表面的成膜厚度，与非水电解液中结构式1所示的化合物含量相互关联。
在一些实施例中，所述结构式1所示的化合物选自以下化合物中的一种或多种：


需要说明的是，以上仅是本发明优选的化合物，并不代表对于本发明的限制。
本领域技术人员在知晓结构式1所示的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7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7。
在一些实施例中，所述锂离子电池为软包电池或硬壳电池。
在一些实施例中，所述正极还包括正极集流体，所述正极材料层形成于所述正极集流体的表面。
所述正极集流体选自可传导电子的金属材料，优选的，所述正极集流体包括Al、Ni、锡、铜、不锈钢的至少一种，在更优选的实施例中，所述正极集流体选自铝箔。
在一些实施例中，所述正极材料层还包括正极粘结剂和正极导电剂。
所述正极粘结剂包括聚偏氟乙烯、偏氟乙烯的共聚物、聚四氟乙烯、偏氟乙烯-六氟丙烯的共聚物、四氟乙烯-六氟丙烯的共聚物、四氟乙烯-全氟烷基乙烯基醚的共聚物、乙烯-四氟乙烯的共聚物、偏氟乙烯-四氟乙烯的共聚物、偏氟乙烯-三氟乙烯的共聚物、偏氟乙烯-三氯乙烯的共聚物、偏氟乙烯-氟代乙烯的共聚物、偏氟乙烯-六氟丙烯-四氟乙烯的共聚物、热塑性聚酰亚胺、聚乙烯及聚丙烯等热塑性树脂；丙烯酸类树脂；羟甲基纤维素钠；以及苯乙烯丁二烯橡胶中的至少一种。
所述正极导电剂包括导电炭黑、导电碳球、导电石墨、导电碳纤维、碳纳米管、石墨烯或还原氧化石墨烯中的至少一种。
在一些实施例中，所述负极活性材料包括碳基负极、硅基负极、锡基负极、锂负极中的至少一种。其中碳基负极可包括石墨、硬碳、软碳、石墨烯、中间相碳微球等；硅基负极可包括硅材料、硅的氧化物、硅碳复合材料以及硅合金材料等；锡基负极可包括锡、锡碳、锡氧、锡金属化合物；锂负极可包括金属锂或锂合金。锂合金具体可以是锂硅合金、锂钠合金、锂钾合金、锂铝合金、锂锡合金和锂铟合金中的至少一种。
在一些实施例中，所述负极材料层还包括有负极粘结剂和负极导电剂，所述负极活性材料、所述负极粘结剂和所述负极导电剂共混得到所述负极材料层。
所述负极粘接剂和负极导电剂的可选择范围分别与所述正极粘结剂和正极导电剂相同，在此不再赘述。
在一些实施例中，所述负极还包括负极集流体，所述负极材料层形成于所述负极集流体的表面。
所述负极集流体选自可传导电子的金属材料，优选的，所述负极集流体包括Al、Ni、锡、铜、不锈钢的至少一种，在更优选的实施例中，所述负极集流体选自铜箔。
在一些实施例中，所述羧酸酯包括环状羧酸酯和/或链状碳酸酯。
作为环状羧酸酯的例子，可以列举如：γ-丁内酯、γ-戊内酯、δ-戊内酯中的至少一种。作为链状碳酸酯的例子，可以列举如：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、氟代乙酸乙酯中的至少一种。
在一些实施例中，所述非水有机溶剂还包括醚类溶剂、腈类溶剂、碳酸酯类溶剂何砜类溶剂中的至少一种。
在一些实施例中，醚类溶剂包括环状醚或链状醚及其氟代物，优选为碳原子数3～10的链状醚及碳原子数3～6的环状醚，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-CH3-THF)，2-三氟甲基四氢呋喃(2-CF3-THF)中的至少一种；所述链状醚具体可以但不限于是二甲氧基甲烷、二乙氧基甲烷、乙氧基甲氧基甲烷、乙二醇二正丙基醚、乙二醇二正丁基醚、二乙二醇二甲基醚。由于链状醚与锂离子的溶剂化能力高、可提高离子解离性，因此特别优选粘性低、可赋予高离子电导率的二甲氧基甲烷、二乙氧基甲烷、乙氧基甲氧基甲烷。醚类化合物可以单独使用一种，也可以以任意的组合及比率组合使用两种以上。醚类化合物的含量没有特殊限制，在不显著破坏本发明高压实锂离子电池效果的范围内是任意的，在非水溶剂体积比为100％中通常体积比为1％以上、优选体积比为2％以上、更优选体积比为3％以上，另外，通常体积比 为30％以下、优选体积比为25％以下、更优选体积比为20％以下。在将两种以上醚类化合物组合使用的情况下，使醚类化合物的总量满足上述范围即可。醚类化合物的含量在上述的优选范围内时，易于确保由链状醚的锂离子离解度的提高和粘度降低所带来的离子电导率的改善效果。另外，负极活性材料为碳基材料的情况下，可抑制因链状醚与锂离子共同发生共嵌入的现象，因此能够使输入输出特性、充放电速率特性达到适当的范围。
在一些实施例中，腈类溶剂具体可以但不限于是乙腈、戊二腈、丙二腈中的至少一种。
在一些实施例中，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)中的至少一种；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)中的至少一种。环状碳酸酯的含量没有特殊限制，在不显著破坏本发明锂离子电池效果的范围内是任意的，但在单独使用一种的情况下其含量的下限相对于非水电解液的溶剂总量来说，通常体积比为3％以上、优选体积比为5％以上。通过设定该范围，可避免由于非水电解液的介电常数降低而导致电导率降低，易于使非水电解质电池的大电流放电特性、相对于负极的稳定性、循环特性达到良好的范围。另外，上限通常体积比为90％以下、优选体积比为85％以下、更优选体积比为80％以下。通过设定该范围，可提高非水电解液的氧化/还原耐性，从而有助于提高高温保存时的稳定性。链状碳酸酯的含量没有特殊限定，相对于非水电解液的溶剂总量，通常为体积比为15％以上、优选体积比为20％以上、更优选体积比为25％以上。另外，通常体积比为90％以下、优选体积比为85％以下、更优选体积比为80％以下。通过使链状碳酸酯的含量在上述范围，容易使非水电解液的粘度达到适当范围，抑制离子电导率的降低，进而有助于使非水电解质电池的输出特性达到良好的范围。在组合使用两种以上链状碳酸酯的情况下，使链状碳酸酯的总量满足上述范围即可。
在一些实施例中，还可优选使用具有氟原子的链状碳酸酯类(以下简称为“氟化链状碳酸酯”)。氟化链状碳酸酯所具有的氟原子的个数只要为1以上则没有特殊限制，但通常为6以下、优选4以下。氟化链状碳酸酯具有多个氟原子的情况下，这些氟原子相互可以键合于同一个碳上，也可以键合于不同的碳上。作为氟化链状碳酸酯，可列举，氟化碳酸二甲酯衍生物、氟化碳酸甲乙酯衍生物、氟化碳酸二乙酯衍生物等。
在一些实施例中，砜类溶剂包括环状砜和链状砜，优选地，在为环状砜的情况下，通常为碳原子数3～6、优选碳原子数3～5，在为链状砜的情况下，通常为碳原子数2～6、优选碳原子数2～5的化合物。砜类溶剂的含量没有特殊限制，在不显著破坏本发明锂离子电池效果的范围内是任意的，相对于非水电解液的溶剂总量，通常体积比为0.3％以上、优选体积比为0.5％以上、更优选体积比为1％以上，另外，通常体积比为40％以下、优选体积比为35％以下、更优选体积比为30％以下。在组合使用两种以上砜类溶剂的情况下，使砜类溶剂的总量满足上述范围即可。砜类溶剂的含量在上述范围内时，倾向于获得高温保存稳定性优异的非水电解液。
在一些实施例中，所述锂盐选自LiPF6、LiBOB、LiDFOB、LiPO2F2、LiBF4、LiSbF6、LiAsF6、LiN(SO2CF3)2、LiN(SO2C2F5)2、LiC(SO2CF3)3、LiN(SO2F)2、LiClO4、LiAlCl4、LiCF3SO3、Li2B10Cl10、LiSO2F、LiTOP(三草酸磷酸锂)、LiDODFP(二氟二草酸磷酸锂)、LiOTFP(四氟草酸磷酸锂)和低级脂肪族羧酸锂盐中的至少一种。
在一些实施例中，所述非水电解液中，所述锂盐的浓度为0.1mol/L～8mol/L。在优选实施例中，所述非水电解液中，所述锂盐的浓度为0.5mol/L～2.5mol/L。具体的，所述非水电解液中，所述锂盐的浓度可以为0.5mol/L、1mol/L、1.5mol/L、2mol/L、2.5mol/L。
在一些实施例中，所述添加剂还包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳 酸酯类化合物、磷酸酯类化合物、硼酸酯类化合物和腈类化合物中的至少一种；
优选的，以所述非水电解液的总质量为100％计，所述添加剂的含量为0.01％～30％。
在一些实施例中，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯、甲基硫酸乙烯酯、中的至少一种；
所述磺酸内酯类化合物选自1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯、1,3-丙烯磺酸内酯中的至少一种；
所述环状碳酸酯类化合物选自碳酸亚乙烯酯、碳酸乙烯亚乙酯、亚甲基碳酸乙烯酯、氟代碳酸乙烯酯、三氟甲基碳酸乙烯酯、双氟代碳酸乙烯酯或结构式2所示化合物中的至少一种，
所述结构式2中，R21、R22、R23、R24、R25、R26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
所述磷酸酯类化合物选自三(三甲基硅烷)磷酸酯、三(三甲基硅烷)亚磷酸酯或结构式3所示化合物中的至少一种：
所述结构式3中，R31、R32、R33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(CmH2m+1)3，m为1～3的自然数，且R31、R32、R33中至少有一个为不饱和烃基；
在优选的实施例中，所述结构式3所示的磷酸酯类化合物可为磷酸三炔丙酯、二炔丙基甲基磷酸酯、二炔丙基乙基磷酸酯、二炔丙基丙基磷酸酯、二炔丙基三氟甲基磷酸酯、二炔丙基-2,2,2-三氟乙基磷酸酯、二炔丙基-3,3,3-三氟丙基磷酸酯、二炔丙基六氟异丙基磷酸酯、磷酸三烯丙酯、二烯丙基甲基磷酸酯、二烯丙基乙基磷酸酯、二烯丙基丙基磷酸酯、二烯丙基三氟甲基磷酸酯、二烯丙基-2,2,2-三氟乙基磷酸酯、二烯丙基-3,3,3-三氟丙基磷酸酯、二烯丙基六氟异丙基磷酸酯中的至少一种；
所述硼酸酯类化合物选自三(三甲基硅烷)硼酸酯和三(三乙基硅烷)硼酸酯中的至少一种；
所述腈类化合物选自丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的至少一种。
在另一些实施例中，所述添加剂还可包括其它能改善电池性能的添加剂：例如，提升电池安全性能的添加剂，具体如氟代磷酸酯、环磷腈等阻燃添加剂，或叔戊基苯、叔丁基苯等防过充添加剂。
需要说明的是，除非特殊说明，一般情况下，所述添加剂中任意一种可选物质在非水电解液中的含量为10％以下，优选的，含量为0.1-5％，更优选的，含量为0.1％～2％。具体的，所述添加剂中任意一种可选物质的含量可以为0.05％、0.08％、0.1％、0.5％、0.8％、1％、1.2％、1.5％、1.8％、2％、2.2％、2.5％、2.8％、3％、3.2％、3.5％、3.8％、4％、4.5％、5％、5.5％、6％、6.5％、7％、7.5％、7.8％、8％、8.5％、9％、9.5％、10％。
在一些实施例中，当添加剂选自氟代碳酸乙烯酯时，以所述非水电解液的总质量为100％计，所述氟代碳酸乙烯酯的含量为0.05％～30％。
在一些实施例中，所述锂离子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、无机-有机复合隔膜等，所述聚合物隔膜选自聚烯烃类、聚酰胺类、聚砜类、聚磷腈类、聚醚砜类、聚醚醚酮类、聚醚酰胺类和聚丙烯腈类中的一种或几种，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。
在优选的实施例，所述隔膜包括基材隔膜和表面涂层，表面涂层为无机颗粒或有机凝胶或二者混合物且涂覆在基材隔膜至少一侧表面。
以下通过实施例对本发明进行进一步的说明。
以下实施例和对比例涉及的化合物如下表所示：
表1
表2实施例和对比例各参数设计

实施例1
本实施例用于说明本发明公开的锂离子电池的制备方法，包括以下操作步骤：
1)非水电解液的制备
将碳酸乙烯酯、碳酸二甲酯以及丙酸丙酯进行混合作为非水有机溶剂，然后加入六氟磷酸锂(LiPF6)至摩尔浓度为1mol/L，再加入化合物7(注：此处化合物7即为表1中的化合物7，以下实施例类同)，化合物7和丙酸丙酯在非水电解液中的质量百分比含量如表2所示。
2)正极板的制备
混合正极活性材料锂钴氧化物LiCoO2，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
混合负极活性材料人造石墨，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，其中，单位面积负极上单面负极材料层的质量和负极活性材料的比表面积如表2所示。
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
在露点控制在-40℃以下的手套箱中，将上述制备的非水电解液注入电芯中，经真空封装，静止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,0.2C恒流充电至3.95V，二次真空封口，然后进一步以0.2C的电流恒流充电至4.48V后，以0.2C的电流恒流放电至3.0V。
实施例2～33
实施例2～33用于说明本发明公开的锂离子电池及其制备方法，包括实施例1中大部分操作步骤，其不同之处在于：
采用表2中实施例2～33所示的添加剂及含量、羧酸酯及含量、单位面积负极上单面负极材料层的质量和负极活性材料的比表面积。
对比例1～14
对比例1～14用于对比说明本发明公开的锂离子电池及其制备方法，包括实施例1中大部分操作步骤，其不同之处在于：
采用表2中对比例1～14所示的添加剂及含量、羧酸酯及含量、单位面积负极上单面负极材料层的质量和负极活性材料的比表面积。
性能测试
对上述制备得到的锂离子电池进行如下性能测试：
低温性能测试
在25℃下，将化成后的电池用1C恒流恒压充至4.48V，然后用1C恒流放电至2.5V，记录放电容量。然后1C恒流恒压充至4.48V，置于-20℃的环境中搁置12h后，0.3C恒流放电至2.5V，记录放电容量。计算公式如下：
-20℃放电容量保持率％＝0.3C放电容量(-20℃)/1C放电容量(25℃)×100％。
高温性能测试
将化成后的电池在常温下用1C恒流充至4.48V，然后恒压充电至电流下降至0.01C，然后以1C的电流恒流放电至3.0V，测量其初始放电容量，再以1C恒流充至4.48V，然后恒压充电至电流下降至0.01C，然后在85℃储存24h后，等电池冷却至常温后以1C恒流放电至3.0V，测量电池的保持容量。计算公式如下：
电池容量保持率(％)＝保持容量/初始放电容量×100％；。
(1)实施例1～21和对比例1～13得到的测试结果填入表3。
表3

由实施例1～21和对比例1～13的测试结果可知，在采用钴酸锂作为正极活性材料的锂离子电池中，其电解液中含有羧酸酯溶剂，加入结构式1所示的化合物作为添加剂，通过控制非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a满足条件1.5≤m/(n*a)≤600，且0.05≤m≤5，0.006≤n≤0.02，0.6≤a≤2时，得到的锂离子电池在低温条件下具有较高的容量保持率，同时在高温储存后也同样具有较高的容量保持率，说明通过对于单位面积负极上单面负极材料层的质量n和负极活性材料的比表面积a的调控可以改变负极材料层的反应面积，进而影响结构式1所示的化合物在负极材料层表面的成膜效果，使负极反应面积与非水电解液中结构式1 所示化合物的含量相匹配，以得到厚度适中且稳定的界面膜，进而有效抑制羧酸酯的分解，减少锂离子电池在低温条件下阻抗的增加，同时提高非水电解液在高温条件下的稳定性，避免非水电解液的分解，进而使锂离子电池在高温和低温条件下均具有较好的表现性能。
由实施例1～21的测试结果可知，当非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a进一步满足条件5≤m/(n*a)≤300时，有利于进一步提高锂离子电池在低温条件下的容量保持率，推测是由于在此范围内，单位面积负极上单面负极材料层的质量n和负极活性材料的比表面积a的配合保证了负极材料层中充足的孔隙通道，提高了非水电解液对于负极材料层的浸润效果，进而降低了阻抗，提高在低温条件下的离子传导效率，进而提高低温容量保持率。
由对比例1～13的测试结果可知，即使非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a满足条件1.5≤m/(n*a)≤600的限定，但m值、n值或a值不满足其范围限定时，锂离子电池在高温和低温条件下仍然不具有较高的容量保持率，例如，从对比例8和对比例9可以看出，结构式1所示的化合物含量过低，对于电池性能提升效果不明显，电池高温容量保持率较低；结构式1所示的化合物含量过高，会导致成膜过厚而导致低温阻抗增加，导致电池低温性能劣化的问题。从对比例10～13可以看出，单位面积负极上单面负极材料层的质量n或负极活性材料的比表面积a过低，均会导致结构式1所示的化合物在有限的反应面积上成膜，成膜厚度过大，影响电池低温性能；单位面积负极上单面负极材料层的质量n或负极活性材料的比表面积a过高，则导致结构式1所示的化合物成膜无法覆盖负极活性材料表面，非水电解液副反应增加，影响电池高温循环性能，同时也导致低温性能的不足。以上可说明m值、n值或a值在提升锂离子电池高低温性能方面具有较强的关联系。同样的，由对比例1～7可知，当m值、n值或a值满足其范围限定时，但m/(n*a)值不满足上述预设条件时，对于电池性能的提升也并不明显。
(2)实施例11、实施例22～26得到的测试结果填入表4。
表4
由实施例11、实施例22～26的测试结果可知，对于不同的结构式1所示的化合物，非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a满足预设条件1.5≤m/(n*a)≤600时，其起到的作用相似，均对于锂离子电池的低温容量保持率和高温容量保持率具有较好的改善作用，说明本发明提供的关系式适用于不同的结构式1所示的化合物。
(3)实施例11、实施例27～29和对比例14得到的测试结果填入表5。
表5
由实施例11、实施例27～29的测试结果可知，当采用不同类型的羧酸酯作为非水有机溶剂时，且非水电解液中结构式1所示的化合物的质量百分比含量m、单位面积负极上单面负极材料层的质量n与负极活性材料的比表面积a满足预设条件1.5≤m/(n*a)≤600时，均能够得到低温性能和高温性能优异的锂离子电池，说明本发明提供的电池体系适用于不同的羧酸酯。
同时，由实施例11、实施例27～29和对比例14的测试结果可知，在非水电解液中加入羧酸酯对于本发明提供的电池体系是必要的，当非水电解液中不存在羧酸酯时，即使m/(n*a)值满足上述预设条件，也会导致锂离子电池低温性能很差，说明本申请中对于m值、n值和a值的调控，一定程度上抑制了羧酸酯的分解，而羧酸酯的稳定存在有利于电池低温性能的提升。
(4)实施例11、实施例30～33得到的测试结果填入表6。
表6
由实施例11、实施例30～33的测试结果可知，在本发明提供的电池体系中，额外加入氟代碳酸乙烯酯(FEC)、丁二腈(SN)、1,3-丙磺酸内酯(PS)或1,3,6-己烷三腈(HTCN)，能够进一步提高锂离子电池高温储存后的容量保持率，说明其它添加剂对电池性能的提升机理与结构式1所示的化合物存在一定的差异，两者在成膜上存在互补作用，进而提高了负极材料层表面的界面膜的质量，另外，可以看出的是，当加入的添加剂为1,3-丙磺酸内酯(PS)或1,3,6-己烷三腈(HTCN)对于锂离子电池的低温性能具有一定的劣化，而加入的添加剂为氟代碳酸乙烯酯(FEC)或丁二腈(SN)时，在提高锂离子电池高温性能的同时也利于提高锂离子电池的低温性能。
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 (16)

  1. 一种锂离子电池，其特征在于，包括正极、负极和非水电解液，所述正极包括正极材料层，所述正极材料层包括含有钴酸锂的正极活性材料，所述负极包括负极集流体以及形成于所述负极集流体上的负极材料层，所述负极材料层包括负极活性材料，所述非水电解液包括非水有机溶剂、锂盐和添加剂，所述非水有机溶剂包括羧酸酯，所述添加剂包括结构式1所示的化合物：
    其中，n为0或1，A选自C或O，X选自R1、R2各自独立选自H、R1和R2不同时选自H，且X、R1和R2中至少含有一个硫原子；
    所述锂离子电池满足以下条件：
    1.5≤m/(n*a)≤600，且0.05≤m≤5，0.006≤n≤0.02，0.6≤a≤2；
    其中，m为非水电解液中结构式1所示的化合物的质量百分比含量，单位为％；
    n为单位面积负极上单面负极材料层的质量，单位为g/cm2；
    a为负极活性材料的比表面积，单位为m2/g。
  2. 根据权利要求1所述的锂离子电池，其特征在于，以所述非水电解液的总质量为100％计，所述羧酸酯的重量百分比含量为10％～55％。
  3. 根据权利要求1所述的锂离子电池，其特征在于，所述锂离子电池满足以下条件：
    5≤m/(n*a)≤300。
  4. 根据权利要求1所述的锂离子电池，其特征在于，所述非水电解液中结构式1所示的化合物的质量百分比含量m为0.1％～3％。
  5. 根据权利要求1所述的锂离子电池，其特征在于，所述单位面积负极上单面负极材料层的质量n为0.008～0.015g/cm2。
  6. 根据权利要求1所述的锂离子电池，其特征在于，所述负极活性材料的比表面积a为0.7～1.6m2/g。
  7. 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所示的化合物选自以下化合物中的一种或多种：


  8. 根据权利要求1所述的锂离子电池，其特征在于，所述羧酸酯包括环状羧酸酯和/或链状碳酸酯。
  9. 根据权利要求1所述的锂离子电池，其特征在于，所述添加剂还包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、磷酸酯类化合物、硼酸酯类化合物和腈类化合物中的至少一种。
  10. 根据权利要求9所述的锂离子电池，其特征在于，以所述非水电解液的总质量为100％计，所述添加剂的含量为0.01％～30％。
  11. 根据权利要求9所述的锂离子电池，其特征在于，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯、甲基硫酸乙烯酯、中的至少一种。
  12. 根据权利要求9所述的锂离子电池，其特征在于，所述磺酸内酯类化合物选自1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯、1,3-丙烯磺酸内酯中的至少一种。
  13. 根据权利要求9所述的锂离子电池，其特征在于，所述环状碳酸酯类化合物选自碳酸亚乙烯酯、碳酸乙烯亚乙酯、亚甲基碳酸乙烯酯、氟代碳酸乙烯酯、三氟甲基碳酸乙烯酯、双氟代碳酸乙烯酯或结构式2所示化合物中的至少一种，
    所述结构式2中，R21、R22、R23、R24、R25、R26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种。
  14. 根据权利要求9所述的锂离子电池，其特征在于，所述磷酸酯类化合物选自三(三甲基硅烷)磷酸酯、三(三甲基硅烷)亚磷酸酯或结构式3所示化合物中的至少一种：
    所述结构式3中，R31、R32、R33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(CmH2m+1)3，m为1～3的自然数，且R31、R32、R33中至少有一个为不饱和烃基。
  15. 根据权利要求9所述的锂离子电池，其特征在于，所述硼酸酯类化合物选自三(三甲基硅烷)硼酸酯和三(三乙基硅烷)硼酸酯中的至少一种。
  16. 根据权利要求9所述的锂离子电池，其特征在于，所述腈类化合物选自丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的至少一种。
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