WO2022134254A1 - 一种电解液及其制备方法和锂离子电池 - Google Patents

一种电解液及其制备方法和锂离子电池 Download PDF

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WO2022134254A1
WO2022134254A1 PCT/CN2021/073200 CN2021073200W WO2022134254A1 WO 2022134254 A1 WO2022134254 A1 WO 2022134254A1 CN 2021073200 W CN2021073200 W CN 2021073200W WO 2022134254 A1 WO2022134254 A1 WO 2022134254A1
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electrolyte
additive
optionally
carbonate
lithium
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PCT/CN2021/073200
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English (en)
French (fr)
Inventor
邹志群
曾汉民
何巍
袁中直
刘建华
刘金成
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惠州亿纬锂能股份有限公司
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Publication of WO2022134254A1 publication Critical patent/WO2022134254A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells

Definitions

  • the application belongs to the technical field of batteries, and relates to an electrolyte, a preparation method thereof, and a lithium ion battery.
  • the purpose of this application is to provide an electrolyte, a preparation method thereof, and a lithium ion battery.
  • the electrolyte provided by the application solves the problem that the battery electrolyte cycle performance, high temperature performance, and normal temperature and low temperature power performance are difficult to balance.
  • the present application provides an electrolyte solution, the electrolyte solution includes an additive, the additive includes an unsaturated carbonate additive, a lithium salt additive, an additive A and an additive B, and the additive B includes an isocyanuric acid derivative .
  • the unsaturated carbonate additive has the function of forming a film on the negative electrode;
  • the lithium salt additive has the function of forming a film on the positive and negative electrodes, and can make the generated SEI film relatively dense, which can inhibit the positive electrode
  • the dissolution of metal ions reduces the damage of metal ions to the negative electrode SEI film and improves the thermal stability of the film;
  • Additive A in the electrolyte system can play the role of assisting film formation on the negative electrode, and at the same time, the film forming resistance is low and thermally stable good performance;
  • additive B can stabilize the electrolyte in the electrolyte system and form a film on the positive electrode, and the formed SEI film can stabilize the boron-containing coating layer of the positive electrode.
  • the present application effectively improves the instability of the positive electrode/negative electrode surface film and the high temperature storage of the battery by using the synergistic effect between the additives by adding unsaturated carbonate additive, lithium salt additive, additive A and additive B at the same time. Severe flatulence and poor high temperature cycle performance;
  • the above-mentioned additives can also be added to the fast-charging electrolyte, which can not only maintain the above performance, but also maintain the fast-charging electrolyte itself.
  • the performance and power performance will not reduce the performance of the fast charge cycle of the fast charge electrolyte as the traditional additives are added.
  • the general structural formula of the isocyanuric acid derivative is where X includes methyl, ethyl, n-propyl, allyl, chlorine or fluorine;
  • the above-mentioned isocyanuric acid derivatives include trimethyl isocyanurate, triethyl isocyanurate, tripropyl isocyanurate, triallyl isocyanurate, trichloroisocyanurate Any one or the combination of at least two in acid and trifluoroisocyanuric acid, the specific structural formula is as follows:
  • the unsaturated carbonate additive includes any one or a combination of at least two of vinylene carbonate VC, fluoroethylene carbonate FEC or vinyl ethylene carbonate VEC.
  • the lithium salt additive includes lithium bisfluorosulfonimide LiFSI, lithium difluorophosphate LiPO 2 F 2 , lithium bis-oxalate borate LiBOB, lithium bis-fluorooxalate borate LiODFB, lithium difluorobis-oxalate phosphate LiODFP or tetrakis Any one or a combination of at least two of Lithium Fluoxalate Phosphate LiTFOP.
  • the additive A is a sulfopropionic anhydride derivative.
  • additive A is wherein R 1 , R 2 , R 3 , R 4 are hydrogen, methyl or form a benzene ring with sulfonic anhydride;
  • the sulfopropionic anhydride derivatives include 2-sulfopropionic anhydride, 3,4-dimethyl-2-sulfopropionic anhydride, 4,4-dimethyl-2-sulfopropionic anhydride or 2-sulfonic anhydride Any one or a combination of at least two of the benzoic anhydrides.
  • the mass fraction of the unsaturated carbonate additive is 0.2-1.0%, such as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0% %Wait.
  • the amount of the unsaturated carbonate additive is too small, a dense SEI film cannot be formed; if the amount of the unsaturated carbonate additive is too large, the impedance will be too large and high temperature gas generation will be caused.
  • the mass fraction of the lithium salt additive is 0.5-2.0%, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0% etc.
  • the lithium salt additive is too small, a dense SEI film cannot be formed, and good power performance cannot be guaranteed; if the lithium salt additive is too much, gas generation will occur.
  • the mass fraction of additive A is 0.2-1.0%, for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0%.
  • the additive A is too small, a dense SEI film cannot be formed on the negative electrode; if the additive A is too much, it will lead to excessive film formation, and the fast charge cycle and power performance will decrease.
  • the mass fraction of additive B is 0.1-1.0%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0% %Wait.
  • the additive B is too small, an effective SEI film cannot be formed on the positive electrode, and the high temperature improvement is not obvious; if the additive B is too much, the impedance will increase, and the fast charge cycle and power performance will decrease.
  • the electrolyte further includes an organic solvent and an electrolyte salt.
  • the electrolyte salt is different from the lithium salt additive.
  • the electrolyte is an electrolyte of a high nickel battery.
  • the electrolyte provided in this application is especially suitable for high nickel batteries.
  • the organic solvent includes cyclic carbonate and chain carbonate.
  • the cyclic carbonate includes ethylene carbonate and/or propylene carbonate.
  • the chain carbonate includes any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or propyl methyl carbonate.
  • dimethyl carbonate can be added; if the requirements for the fast charging system are not high or there is no requirement, other chain carbonates other than dimethyl carbonate can be added.
  • the organic solvent may also include a chain carboxylate, and the combination of the chain carboxylate and the above-mentioned organic solvent makes the electrical conductivity of the electrolyte higher and the viscosity lower, improves the rate performance of the electrolyte, and also improves the rate performance of the electrolyte. Helps to improve fast charging performance.
  • the chain carboxylate includes methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyric propionate ester, methyl butyrate, ethyl butyrate, or butyl butyrate, or a combination of at least two.
  • the volume fraction of the cyclic carbonate is 20-40%, such as 20%, 25%, 30%, 35% or 40%, etc.
  • the volume of the dimethyl carbonate Fraction is 0-20%, such as 0%, 10%, 12%, 14%, 16%, 18% or 20%, etc., other chain carbonates other than dimethyl carbonate in the chain carbonate
  • the volume fraction of carboxylate is 40-70%, such as 40%, 45%, 50%, 55%, 60%, 65% or 70%, etc.
  • the volume fraction of chain carboxylate is 0-20%, such as 0%, 5%, 10%, 15%, 18% or 20% etc.
  • the organic solvent is composed of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and chain carboxylate.
  • the volume fraction of ethylene carbonate is 20-40%, such as 20%, 25%, 30%, 35% or 40%, etc.
  • the volume fraction of dimethyl carbonate is 10-20% %, such as 10%, 12%, 14%, 16%, 18% or 20%, etc.
  • the volume fraction of ethyl methyl carbonate is 40-70%, such as 40%, 45%, 50%, 55%, 60% , 65% or 70%, etc.
  • the volume fraction of chain carboxylate is 10-20%, such as 10%, 12%, 14%, 15%, 16%, 18% or 20%, etc.
  • the organic solvent may account for 80-85% of the mass fraction of the entire electrolyte system.
  • the electrolyte salt includes lithium hexafluorophosphate LiPF 6 , lithium hexafluoroarsenate LiAsF 6 , lithium perchlorate LiClO 4 , lithium bisfluorosulfonimide LiFSI, lithium tetrafluoroborate LiBF4 and bistri At least one of lithium fluoromethanesulfonimide LiTFSI.
  • the concentration of the electrolyte salt is 1.0-1.5mol/L, such as 1.0mol/L, 1.1mol/L, 1.2mol/L, 1.3mol/L, 1.4mol/L or 1.5mol /L, etc.
  • the present application provides a method for preparing an electrolyte solution as described in the first aspect, the method comprising the following steps:
  • the additive in the formula amount and other raw materials are mixed to obtain the electrolyte, and the additive includes an unsaturated carbonate additive, a lithium salt additive, an additive A and an additive B.
  • the preparation method provided by the present application is simple in operation and short in process, and can meet the needs of industrialized large-scale production.
  • the other raw materials include organic solvents and electrolyte salts in formula amounts.
  • the order of adding the mixed raw materials is adding additives to the organic solvent, and then adding the electrolyte salt.
  • the mixing is stirring mixing.
  • the temperature of the mixing is 5-20°C, such as 5°C, 6°C, 7°C, 8°C, 9°C or 10°C, and the like.
  • the purpose of using a lower mixing temperature is to prevent the thermal decomposition of lithium salts and additives, resulting in an increase in the free acid of the electrolyte.
  • the protective atmosphere includes a nitrogen atmosphere and/or an argon atmosphere.
  • the preparation method comprises the following steps:
  • the formula amounts of unsaturated carbonate additive, lithium salt additive, additive A and additive B are added to the organic solvent, followed by adding electrolyte salt, stirring and mixing to obtain the electrolyte solution.
  • the present application provides a lithium ion battery, the lithium ion battery comprising the electrolyte according to the first aspect.
  • the lithium ion battery further includes a positive electrode, a negative electrode and a separator.
  • the active material of the positive electrode is a high nickel ternary material.
  • the high-nickel ternary material refers to that in the ternary material, in addition to lithium, in the other three metal elements, the molar content of nickel element is more than 50%.
  • the active material of the positive electrode includes a nickel-cobalt-manganese ternary material and/or a nickel-cobalt-aluminum ternary material.
  • the active material of the negative electrode includes graphite.
  • the unsaturated carbonate additive is used as the negative electrode film-forming additive, and the function that can be played in the electrolyte system is to form a dense SEI film on the surface of the graphite negative electrode and improve the structure of the negative electrode material. stability, reduce battery cycle resistance, and improve battery cycle performance; the role of lithium salt additives in the electrolyte system is to enhance the stability of the positive and negative surface films at high temperatures, improve high-temperature storage performance, and inhibit the production of batteries in the battery.
  • Additive A forms a dense and good lithium-conducting SEI film on the negative electrode, which is beneficial to improve high-temperature performance and power characteristics;
  • Additive B has an amide structure, which can not only stabilize the electrolyte salt in the electrolyte system, but also Moreover, the positive electrode film of the cyclic amide after the positive electrode is oxidized to form a film has a complexation effect with some coating layers of the positive electrode (such as a boron-containing coating layer), which effectively improves the stability of the positive electrode coating layer and is conducive to improving the electrolyte solution.
  • the high-temperature performance of the battery can reduce the gas production in the high-temperature storage of the battery.
  • This embodiment provides an electrolyte, which consists of an organic solvent, an electrolyte salt and an additive.
  • the additives are unsaturated carbonate additives, lithium salt additives, additive A and additive B.
  • the unsaturated carbonate additive is vinylene carbonate, the mass fraction in the electrolyte is 0.8%;
  • the lithium salt additive is lithium bisfluorosulfonimide, and the mass fraction in the electrolyte is 2%;
  • Additive A is 2-sulfobenzoic anhydride (compound 10), the mass fraction in the electrolyte is 0.6%;
  • Additive B is trimethyl isocyanurate (compound 1), and the mass fraction in the electrolyte is 0.6%.
  • the lithium salt is lithium hexafluorophosphate, and its concentration in the electrolyte is 1.0 mol/L.
  • the organic solvent is composed of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and chain carboxylate (ethyl propionate). Taking the total volume of the organic solvent as 100%, the volume fraction of ethylene carbonate is 30%, the volume fraction of dimethyl carbonate is 15%, the volume fraction of ethyl methyl carbonate is 40%, and the volume fraction of chain carboxylate is 15%; if the mass percentage of the electrolyte is 100%, the organic solvent accounts for The mass percentage of the electrolyte is 83.5%.
  • the present embodiment also provides a preparation method of the above-mentioned electrolyte, and its specific method is:
  • This embodiment provides an electrolyte, which consists of an organic solvent, an electrolyte salt and an additive.
  • the additives are unsaturated carbonate additives, lithium salt additives, additive A and additive B.
  • the unsaturated carbonate additive is fluoroethylene carbonate, the mass fraction in the electrolyte is 0.6%;
  • the lithium salt additive is lithium difluorophosphate, and the mass fraction in the electrolyte is 1.0%;
  • Additive A is 2-sulfopropionic anhydride (compound 7), the mass fraction in the electrolyte is 0.8%;
  • Additive B is triethyl isocyanurate (compound 2), and the mass fraction in the electrolyte is 0.4%.
  • the lithium salt is lithium hexafluorophosphate, and its concentration in the electrolyte is 1.2 mol/L.
  • the organic solvent is composed of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and chain carboxylate (methyl propionate), and the volume fraction of ethylene carbonate is 100% based on the total volume of the organic solvent. 20%, the volume fraction of dimethyl carbonate is 10%, the volume fraction of ethyl methyl carbonate is 60%, and the volume fraction of chain carboxylate is 10%. ; Taking the mass percentage of the electrolyte as 100%, the mass percentage of the organic solvent in the electrolyte is 82.2%.
  • the present embodiment also provides a preparation method of the above-mentioned electrolyte, and its specific method is:
  • This embodiment provides an electrolyte, which consists of an organic solvent, an electrolyte salt and an additive.
  • the additives are unsaturated carbonate additives, lithium salt additives, additive A and additive B.
  • the unsaturated carbonate additive is a mixture of vinylene carbonate and fluoroethylene carbonate (the mass ratio of vinylene carbonate and fluoroethylene carbonate is 1:1), and the mass fraction in the electrolyte is 1.0%;
  • the lithium salt additive is lithium bis-oxalate borate, and the mass fraction in the electrolyte is 0.5%;
  • Additive A is 4,4-dimethyl-2-sulfopropionic anhydride (compound 8), the mass fraction in the electrolyte is 1.0%;
  • Additive B is trichloroisocyanuric acid (compound 5), and the mass fraction in the electrolyte is 1.0%.
  • the lithium salt is lithium hexafluorophosphate, and its concentration in the electrolyte is 1.2 mol/L.
  • the organic solvent is composed of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and chain carboxylate (propyl acetate), and the total volume of the organic solvent is 100%, and the volume fraction of ethylene carbonate is 30%. %, the volume fraction of dimethyl carbonate is 10%, the volume fraction of ethyl methyl carbonate is 50%, and the volume fraction of chain carboxylate is 10%. Taking the mass percentage of the electrolyte as 100%, the mass percentage of the organic solvent in the electrolyte is 81.5%.
  • the present embodiment also provides a preparation method of the above-mentioned electrolyte, and its specific method is:
  • This embodiment provides an electrolyte, which consists of an organic solvent, an electrolyte salt and an additive.
  • the additives are unsaturated carbonate additives, lithium salt additives, additive A and additive B.
  • the unsaturated carbonate additive is a mixture of vinylene carbonate and fluoroethylene carbonate (the mass ratio of vinylene carbonate and fluoroethylene carbonate is 1:3), and the mass fraction in the electrolyte is 1.0%;
  • the lithium salt additive is lithium difluorobisoxalate phosphate, and the mass fraction in the electrolyte is 1.0%;
  • Additive A is 3,4-dimethylsulfopropionic anhydride (compound 9), the mass fraction in the electrolyte is 0.2%;
  • the lithium salt is lithium hexafluorophosphate, and its concentration in the electrolyte is 1.2 mol/L.
  • the organic solvent is composed of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and chain carboxylate (methyl butyrate). Taking the total volume of the organic solvent as 100%, the volume fraction of ethylene carbonate is 20%, the volume fraction of dimethyl carbonate is 20%, the volume fraction of ethyl methyl carbonate is 40%, and the volume fraction of chain carboxylate is 20%. Taking the mass percentage of the electrolyte as 100%, the mass percentage of the organic solvent in the electrolyte is 82.7%.
  • This embodiment provides an electrolyte, which consists of an organic solvent, an electrolyte salt and an additive.
  • the additives are unsaturated carbonate additives, lithium salt additives, additive A and additive B.
  • the unsaturated carbonate additive is vinylene carbonate, the mass fraction in the electrolyte is 0.8%;
  • the lithium salt additive is lithium bisfluorosulfonimide, and the mass fraction in the electrolyte is 2%;
  • Additive A is 2-sulfobenzoic anhydride (compound 10), the mass fraction in the electrolyte is 0.6%;
  • Additive B is trimethyl isocyanurate (compound 1), and the mass fraction in the electrolyte is 0.6%.
  • the lithium salt is lithium hexafluorophosphate, and its concentration in the electrolyte is 1.0 mol/L.
  • the organic solvent is composed of ethylene carbonate and ethyl methyl carbonate, and based on the total volume of the organic solvent as 100%, the volume fraction of ethylene carbonate is 30%, and the volume fraction of ethyl methyl carbonate is 70%; The mass percentage is 100%, and the mass percentage of the organic solvent in the electrolyte is 83.5%.
  • the present embodiment also provides a preparation method of the above-mentioned electrolyte, and its specific method is:
  • the electrolyte provided by this comparative example is the same as the electrolyte of Example 1 in other aspects except that the additive does not contain unsaturated carbonate additives.
  • electrolyte solution provided by this comparative example does not contain lithium salt additive, other aspects are the same as the electrolyte solution of Example 1.
  • the electrolyte provided by this comparative example is the same as the electrolyte of Example 1 in other aspects except that the additive does not contain additive A.
  • the electrolyte provided in this comparative example is the same as the electrolyte in Example 1 in other aspects except that the additive does not contain additive B.
  • the electrolyte provided by this comparative example is the same as the electrolyte of Example 5 in other aspects except that the additive does not contain additive A.
  • the electrolyte provided by this comparative example is the same as the electrolyte of Example 5 in other aspects except that the additive does not contain additive B.
  • the electrolyte solutions provided in the various examples and comparative examples were applied to lithium ion batteries, and the performance tests were carried out with the lithium ion batteries.
  • the specific preparation method of the lithium-ion battery used for the test includes: preparing the negative electrode material graphite, the conductive agent acetylene black and the binder SBR in a mass percentage of 94:1:5 into a slurry, coating it on the copper foil current collector, and vacuum drying. , to prepare the negative pole piece; the positive pole material NCM811, the conductive agent acetylene black and the binder PVDF are prepared into a slurry in a mass ratio of 94:3:3, coated on the aluminum foil current collector, vacuum dried to obtain the positive pole piece .
  • the positive pole piece, the negative pole piece, the Celgard2400 diaphragm and the electrolyte prepared in the example or the comparative example were assembled into a soft pack battery, and the electrochemical test was carried out by using the Xinwei charging and discharging test cabinet.
  • the lithium-ion battery At 25°C/45°C, charge the lithium-ion battery with a constant current of 1.5C (nominal capacity) to a voltage of 4.2V, and then charge it with a constant voltage of 4.2V until the current is less than or equal to 0.05C. Discharge to the cut-off voltage of 2.8V, the above is a charge-discharge cycle.
  • the lithium-ion battery was subjected to 1500 charge-discharge cycles at 25°C and 1,000 charge-discharge cycles at 45°C according to the above conditions.
  • the capacity retention rate (%) of the lithium ion battery after N cycles (the discharge capacity of the Nth cycle/the first discharge capacity) ⁇ 100%, and N is the number of cycles of the lithium ion battery.
  • the lithium-ion battery was charged at a constant current of 1C to a voltage of 4.2V, then charged at a constant voltage of 4.2V to a current of 0.05C, and then discharged at a constant current of 1C for 30min, that is, the state of charge of the lithium-ion battery for 50% SOC.
  • the cells were discharged at 25°C for 30s at 2C, and at -20°C for 10s at 0.33C, respectively, to measure the DC resistance (DCR) to characterize the normal temperature power performance and low temperature power performance of the lithium-ion battery.
  • DCR DC resistance
  • DCR (voltage before discharge-voltage at the end of pulse discharge)/(discharge current).
  • the lithium-ion battery At 25°C, charge the lithium-ion battery with a constant current of 1C to a voltage of 4.2V, and then charge it with a constant voltage of 4.2V to a current of 0.05C.
  • the volume of the test lithium-ion battery is V0; then put the lithium-ion battery into 60 °C in an incubator, respectively, for 30 days and 60 days, and the volume of the test lithium-ion battery was taken out and recorded as Vn.
  • Volume expansion rate (%) (Vn-V0)/V0 ⁇ 100% of the lithium-ion battery after being stored at 60°C for n days.
  • unsaturated carbonate additives are added to the electrolytes provided by the examples as negative electrode film-forming additives, and a dense SEI film is formed on the surface of the graphite negative electrode, which improves the structural stability of the negative electrode material and reduces the battery cycle impedance.
  • additive B improves the battery cycle performance; by adding lithium salt additives in the electrolyte, by strengthening the stability of the positive and negative surface film at high temperature, improve the high temperature storage performance, suppress the gas production in the battery; by adding in the electrolyte Additive A forms a dense SEI film with good lithium conductivity at the negative electrode, which is beneficial to improve high temperature and power characteristics; by adding additive B to the electrolyte, due to its amide structure, it can not only stabilize the electrolyte salt, but also oxidize the cyclic amide at the positive electrode.
  • the positive electrode film after film formation has a complexation effect with some coating layers of the positive electrode (such as boron-containing coating layer), which effectively improves the stability of the positive electrode coating layer, which is beneficial to improve the high temperature performance of the electrolyte and reduce the high temperature of the battery. Store gas.
  • some coating layers of the positive electrode such as boron-containing coating layer
  • Comparative Examples 3 and 5 do not contain additive A, the high-temperature cycle performance and high-temperature storage performance are deteriorated.
  • Comparative Examples 4 and 6 do not contain additive B, the high-temperature cycle and high-temperature storage performance are significantly deteriorated.
  • Example 5 shows that in the non-fast charging solvent system, the addition of additives A and B can also improve the high temperature performance of the battery on the basis of maintaining the original cycle performance and power performance. .
  • the present application illustrates the detailed method of the present application through the above-mentioned embodiments, but the present application is not limited to the above-mentioned detailed method, which does not mean that the present application must rely on the above-mentioned detailed method for implementation.

Abstract

本申请提供了一种电解液及其制备方法和锂离子电池。所述电解液包括添加剂，所述添加剂包括不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B，所述添加剂B包括异氰脲酸衍生物。其制备方法包括：在保护性气氛下，将配方量的添加剂和其他原料混合，得到所述电解液。

Description

一种电解液及其制备方法和锂离子电池 技术领域
本申请属于电池技术领域，涉及一种电解液及其制备方法和锂离子电池。
背景技术
近年来高镍材料被应用到电动汽车电池中，但是Ni含量的提升让原本就不太安全的三元材料热稳定性变得更加不可控。将NCM与LMFP复合能有效提升电池安全性，但是LMFP本身存在电子电导率、离子扩散低以及受Jahn-Taller影响的问题，材料本身循环性能较差，尤其是高温情况下，Mn溶出加剧了材料衰减。高镍三元本身也会因为Ni元素含量的增高容易发生阳离子混排，同时，高镍三元在高温情况下更容易与水和CO 2反应，造成电池产气影响循环。而动力电池组在实际使用中，即便是有电池管理系统(BMS)的管控，模组温升也往往达到40℃以上，因此如何提升电池在高温情况下的循环寿命和高温储存成为非常重要的问题，同时还能够兼具功率等性能。
发明内容
本申请的目的在于提供一种电解液及其制备方法和锂离子电池，本申请提供的电解液解决了电池电解液循环性能、高温性能、常温和低温功率性能难以兼顾的问题。
为达此目的，本申请采用以下技术方案：
第一方面，本申请提供一种电解液，所述电解液包括添加剂，所述添加剂包括不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B，所述添加剂B包括异氰脲酸衍生物。
本申请提供的电解液中，相互配合的各种添加剂解决了电解液循环性能、 高温性能、功率性能难以兼顾的问题。
具体来讲，在本申请提供的电解液体系中，不饱和碳酸酯添加剂具有在负极成膜；锂盐添加剂具有正负极成膜的作用，且能够使得生成的SEI膜较为致密，可抑制正极金属离子溶出，减弱金属离子对负极SEI膜的破坏，提高成膜的热稳定性；添加剂A在电解液体系中能够起到在负极辅助成膜的作用，同时成膜阻抗较低，且热稳定性好；添加剂B在电解液体系中能够起到稳定电解液、同时在正极成膜的作用，且形成的SEI膜具有能够稳定正极含硼包覆层的作用。
综合来说，本申请通过同时添加不饱和碳酸酯添加剂、锂盐添加剂、添加剂A、添加剂B的方式，利用添加剂之间的协同作用有效地改善了正极/负极表面膜的不稳定、电池高温存储胀气严重及高温循环性能差的问题；
同时，除了向普通的电解液中加入上述添加剂，也可以向快充型电解液中加入上述添加剂，不仅能够保持上述的性能，还能够保持快充型电解液本身具备的较好的快充循环性能、功率性能，并不会如传统的添加剂加入后会降低快充型电解液的快充循环等性能。
可选地，本申请提供的电解液中，所述异氰脲酸衍生物的结构通式为
Figure PCTCN2021073200-appb-000001
其中X包括甲基、乙基、正丙基、烯丙基、氯或氟；
可选地，上述异氰脲酸衍生物包括异氰脲酸三甲酯、异氰脲酸三乙酯、异氰脲酸三丙酯、异氰脲酸三烯丙酯、三氯异氰脲酸、三氟异氰脲酸中的任意一种或至少两种的组合，具体结构式如下：
Figure PCTCN2021073200-appb-000002
以下作为本申请可选的技术方案，但不作为对本申请提供的技术方案的限制，通过以下可选的技术方案，可以更好的达到和实现本申请的技术目的和有益效果。
作为本申请可选的技术方案，所述不饱和碳酸酯添加剂包括碳酸亚乙烯酯VC、氟代碳酸乙烯酯FEC或乙烯基碳酸乙烯酯VEC中的任意一种或至少两种的组合。
可选地，所述锂盐添加剂包括双氟磺酰亚胺锂LiFSI、二氟磷酸锂LiPO 2F 2、双草酸硼酸锂LiBOB、双氟草酸硼酸锂LiODFB、二氟双草酸磷酸锂LiODFP或四氟草酸磷酸锂LiTFOP中的任意一种或至少两种的组合。
可选地，所述添加剂A为磺丙酸酐衍生物。
可选地，添加剂A的结构通式为
Figure PCTCN2021073200-appb-000003
其中R 1、R 2、R 3、R 4为氢、甲基或与磺酸酐并成苯环；
可选地，所述磺丙酸酐衍生物包括2-磺丙酸酐、3,4-二甲基-2-磺丙酸酐、4,4-二甲基-2-磺丙酸酐或2-磺基苯甲酸酐中的任意一种或至少两种的组合。
具体的结构式如下：
Figure PCTCN2021073200-appb-000004
可选地，所述电解液中，不饱和碳酸酯添加剂的质量分数为0.2-1.0％，例如0.2％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％或1.0％等。本申请中，如果不饱和碳酸酯添加剂的量过少，不能形成致密的SEI膜；如果不饱和碳酸酯添加量过多，会导致阻抗偏大且导致高温产气。
可选地，所述电解液中，锂盐添加剂的质量分数为0.5-2.0％，例如0.5％、0.6％、0.7％、0.8％、0.9％、1.0％、1.1％、1.2％、1.3％、1.4％、1.5％、1.6％、1.7％、1.8％、1.9％或2.0％等。本申请中，如果锂盐添加剂过少，不能形成致密的SEI膜，不能保证良好的功率性能；如果锂盐添加剂过多，会带来产气。
可选地，所述电解液中，添加剂A的质量分数为0.2-1.0％，例如0.2％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％或1.0％等。本申请中，如果添加剂A过少，会导致不能在负极形成致密的SEI膜；如果添加剂A过多，会导致过度成膜，快充循环和功率性能下降。
可选地，所述电解液中，添加剂B的质量分数为0.1-1.0％，例如0.1％，0.2％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％或1.0％等。本申请中，如果添加剂B过少，会导致不能在正极形成有效的SEI膜，高温改善不明显；如果添加剂B过多，会导致阻抗增大，快充循环和功率性能下降。
作为本申请可选的技术方案，所述电解液还包括有机溶剂和电解质盐。本申请中，所述电解质盐与锂盐添加剂不同。
可选地，所述电解液为高镍电池的电解液。本申请提供的电解液特别适用于高镍电池。
作为本申请可选的技术方案，所述有机溶剂包括环状碳酸酯和链状碳酸酯。
可选地，所述环状碳酸酯包括碳酸乙烯酯和/或碳酸丙烯酯。
可选地，所述链状碳酸酯包括碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯或碳酸甲丙酯中的任意一种或至少两种的组合。
如果是对快充和功率要求高，可加入碳酸二甲酯；如果对快充体系要求不高或者无要求可以添加除碳酸二甲酯之外的其他链状碳酸酯。
可选地，所述有机溶剂还可包括链状羧酸酯，链状羧酸酯与上述有机溶剂的配合使得电解液的电导率较高、粘度较低，提高电解液的倍率性能，同时也有利于提高快充性能。
可选地，所述链状羧酸酯包括甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸丁酯、丁酸甲酯、丁酸乙酯或丁酸丁酯中的任意一种或至少两种的组合。
可选地，所述有机溶剂中，所述环状碳酸酯的体积分数为20-40％，例如20％、25％、30％、35％或40％等，所述碳酸二甲酯的体积分数为0-20％，例如0％、10％、12％、14％、16％、18％或20％等，在所述链状碳酸酯中除碳酸二甲酯外的其他链状碳酸酯的体积分数为40-70％，例如40％、45％、50％、55％、60％、65％或70％等，链状羧酸酯的体积分数为0-20％，例如0％、5％、10％、15％、18％或20％等。
可选地，所述有机溶剂由碳酸乙烯酯、碳酸二甲酯、碳酸甲乙酯和链状羧酸酯组成。
可选地，所述有机溶剂中，碳酸乙烯酯的体积分数为20-40％，例如20％、25％、30％、35％或40％等，碳酸二甲酯的体积分数为10-20％，例如10％、12％、14％、16％、18％或20％等，碳酸甲乙酯的体积分数为40-70％，例如40％、45％、50％、55％、60％、65％或70％等，链状羧酸酯的体积分数为10-20％，例如10％、12％、14％、15％、16％、18％或20％等
本申请提供的电解液中，有机溶剂可以占整个电解液体系的质量分数的80-85％。
作为本申请可选的技术方案，所述电解质盐包括六氟磷酸锂LiPF 6、六氟砷酸锂LiAsF 6、高氯酸锂LiClO 4、双氟磺酰亚胺锂LiFSI、四氟硼酸锂LiBF4和双三氟甲烷磺酰亚胺锂LiTFSI中的至少一种。
可选地，所述电解液中，电解质盐的浓度为1.0-1.5mol/L，例如1.0mol/L、1.1mol/L、1.2mol/L、1.3mol/L、1.4mol/L或1.5mol/L等。
第二方面，本申请提供一种如第一方面所述电解液的制备方法，所述方法包括以下步骤：
在保护性气氛下，将配方量的添加剂和其他原料混合，得到所述电解液，所述添加剂包括不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B。
本申请提供的制备方法操作简单，流程短，能够满足进行产业化大规模生产的需要。
作为本申请可选的技术方案，所述其他原料包括配方量的有机溶剂和电解质盐。
可选地，所述混合的原料加入顺序为向有机溶剂中加入添加剂，再加入电解质盐。
可选地，所述混合为搅拌混合。
可选地，所述混合的温度为5-20℃，例如5℃、6℃、7℃、8℃、9℃或10℃等。采用较低的混合温度的目的在于防止锂盐、添加剂受热分解导致电解液游离酸升高。
可选地，所述保护性气氛包括氮气气氛和/或氩气气氛。
作为本申请可选的技术方案，所述制备方法包括以下步骤：
在保护性气氛下，向有机溶剂中加入配方量的不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B，之后加入电解质盐，搅拌混合，得到所述电解液。
第三方面，本申请提供一种锂离子电池，所述锂离子电池包含如第一方面所述的电解液。
作为本申请可选的技术方案，所述锂离子电池还包含正极、负极和隔膜。
可选地，所述正极的活性物质为高镍三元材料。所述高镍三元材料是指三元材料中除锂之外，在其他三种金属元素中，镍元素的摩尔百分含量在50％以上。
可选地，所述正极的活性物质包括镍钴锰三元材料和/或镍钴铝三元材料。
本申请中，所述镍钴锰三元材料的化学式可以表示为：Li(Ni xCo yMn z)O 2，其中0.5<x≤0.8，0<y≤0.2，0<z≤0.3且x+y+z＝1。
可选地，所述镍钴铝三元材料的化学式为：Li(Ni xCo yAl z)O 2，其中0.5<x≤0.8，0<y≤0.2，0<z≤0.05且x+y+z＝1。
可选地，所述负极的活性物质包括石墨。
与现有技术相比，本申请具有以下有益效果：
(1)在本申请提供的电解液体系中，不饱和碳酸酯类添加剂作为负极成膜添加剂，在电解液体系中能够起到的作用为在石墨负极表面形成致密的SEI膜，提高负极材料结构稳定性，降低电池循环阻抗，提高了电池循环性能；锂盐类添加剂在电解液体系中的作用是通过强化正负极表面膜在高温下的稳定性，提高高温存储性能，抑制电池内的产气量；在电解液体系中，添加剂A在负极形成致密且导锂性能好的SEI膜，有利于改善高温性能和功率特性；添加剂B由于具有酰胺结构，在电解液体系中不仅能够稳定电解质盐，而且环状酰胺在正极氧化成膜后的正极膜与正极的某些包覆层(例如含硼包覆层)具有络合作用，有效提高了正极包覆层的稳定性，有利于改善电解液的高温性能，减少电池高温存储产气。
(2)本申请提供的制备方法操作简单，流程短，能够满足进行产业化大规模生产的需要。
具体实施方式
为更好地说明本申请，便于理解本申请的技术方案，下面对本申请进一步详细说明。但下述的实施例仅仅是本申请的简易例子，并不代表或限制本申请的权利保护范围，本申请保护范围以权利要求书为准。
以下为本申请典型但非限制性实施例：
实施例1
本实施例提供一种电解液，所述电解液由有机溶剂、电解质盐和添加剂组成。所述添加剂为不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B。
不饱和碳酸酯添加剂为碳酸亚乙烯酯，在电解液中的质量分数0.8％；
锂盐添加剂为双氟磺酰亚胺锂，在电解液中的质量分数2％；
添加剂A为2-磺基苯甲酸酐(化合物10)，在电解液中的质量分数0.6％；
添加剂B为异氰脲酸三甲酯(化合物1)，在电解液中的质量分数0.6％。
所述锂盐为六氟磷酸锂，其在电解液中的浓度为1.0mol/L。
所述有机溶剂由碳酸乙烯酯、碳酸二甲酯、碳酸甲乙酯和链状羧酸酯(丙酸乙酯)组成，以有机溶剂的总体积为100％计，碳酸乙烯酯的体积分数为30％，碳酸二甲酯的体积分数为15％，碳酸甲乙酯的体积分数为40％，链状羧酸酯的体积分数为15％；以电解液质量百分数为100％算，有机溶剂占电解液的质量百分数为83.5％。
本实施例还提供一种上述电解液的制备方法，其具体方法为：
在氩气气氛下，向有机溶剂中加入配方量的不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B，之后加入电解质盐，在15℃温度下搅拌混合，得到所述电解液。
本实施例制备的电解液的测试结果见表1。
实施例2
本实施例提供一种电解液，所述电解液由有机溶剂、电解质盐和添加剂组成。所述添加剂为不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B。
不饱和碳酸酯添加剂为氟代碳酸乙烯酯，在电解液中的质量分数0.6％；
锂盐添加剂为二氟磷酸锂，在电解液中的质量分数1.0％；
添加剂A为2-磺丙酸酐(化合物7)，在电解液中的质量分数0.8％；
添加剂B为异氰脲酸三乙酯(化合物2)，在电解液中的质量分数0.4％。
所述锂盐为六氟磷酸锂，其在电解液中的浓度为1.2mol/L。
所述有机溶剂由碳酸乙烯酯、碳酸二甲酯、碳酸甲乙酯和链状羧酸酯(丙 酸甲酯)组成，以有机溶剂的总体积为100％计，碳酸乙烯酯的体积分数为20％，碳酸二甲酯的体积分数为10％，碳酸甲乙酯的体积分数为60％，链状羧酸酯的体积分数为10％。；以电解液质量百分数为100％算，有机溶剂占电解液的质量百分数为82.2％。
本实施例还提供一种上述电解液的制备方法，其具体方法为：
在氩气气氛下，向有机溶剂中加入配方量的不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B，之后加入电解质盐，在5℃温度下搅拌混合，得到所述电解液。
本实施例制备的电解液的测试结果见表1。
实施例3
本实施例提供一种电解液，所述电解液由有机溶剂、电解质盐和添加剂组成。所述添加剂为不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B。
不饱和碳酸酯添加剂为碳酸亚乙烯酯和氟代碳酸乙烯酯的混合物(碳酸亚乙烯酯和氟代碳酸乙烯酯的质量比为1:1)，在电解液中的质量分数1.0％；
锂盐添加剂为双草酸硼酸锂，在电解液中的质量分数0.5％；
添加剂A为4,4-二甲基-2-磺丙酸酐(化合物8)，在电解液中的质量分数1.0％；
添加剂B为三氯异氰脲酸(化合物5)，在电解液中的质量分数1.0％。
所述锂盐为六氟磷酸锂，其在电解液中的浓度为1.2mol/L。
所述有机溶剂由碳酸乙烯酯、碳酸二甲酯、碳酸甲乙酯和链状羧酸酯(乙酸丙酯)组成，以有机溶剂的总体积为100％计，碳酸乙烯酯的体积分数为30％，碳酸二甲酯的体积分数为10％，碳酸甲乙酯的体积分数为50％，链状羧酸酯的 体积分数为10％。以电解液质量百分数为100％算，有机溶剂占电解液的质量百分数为81.5％。
本实施例还提供一种上述电解液的制备方法，其具体方法为：
在氩气气氛下，向有机溶剂中加入配方量的不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B，之后加入电解质盐，在15℃温度下搅拌混合，得到所述电解液。
本实施例制备的电解液的测试结果见表1。
实施例4
本实施例提供一种电解液，所述电解液由有机溶剂、电解质盐和添加剂组成。所述添加剂为不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B。
不饱和碳酸酯添加剂为碳酸亚乙烯酯和氟代碳酸乙烯酯的混合物(碳酸亚乙烯酯和氟代碳酸乙烯酯的质量比为1:3)，在电解液中的质量分数1.0％；
锂盐添加剂为二氟双草酸磷酸锂，在电解液中的质量分数1.0％；
添加剂A为3,4-二甲基磺丙酸酐(化合物9)，在电解液中的质量分数0.2％；
添加剂B异氰脲酸三烯丙酯(化合物4)，在电解液中的质量分数0.1％。
所述锂盐为六氟磷酸锂，其在电解液中的浓度为1.2mol/L。
所述有机溶剂由碳酸乙烯酯、碳酸二甲酯、碳酸甲乙酯和链状羧酸酯(丁酸甲酯)组成，以有机溶剂的总体积为100％计，碳酸乙烯酯的体积分数为20％，碳酸二甲酯的体积分数为20％，碳酸甲乙酯的体积分数为40％，链状羧酸酯的体积分数为20％。以电解液质量百分数为100％算，有机溶剂占电解液的质量百分数为82.7％。
本实施例制备的电解液的测试结果见表1。
实施例5
本实施例提供一种电解液，所述电解液由有机溶剂、电解质盐和添加剂组成。所述添加剂为不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B。
不饱和碳酸酯添加剂为碳酸亚乙烯酯，在电解液中的质量分数0.8％；
锂盐添加剂为双氟磺酰亚胺锂，在电解液中的质量分数2％；
添加剂A为2-磺基苯甲酸酐(化合物10)，在电解液中的质量分数0.6％；
添加剂B为异氰脲酸三甲酯(化合物1)，在电解液中的质量分数0.6％。
所述锂盐为六氟磷酸锂，其在电解液中的浓度为1.0mol/L。
所述有机溶剂由碳酸乙烯酯、碳酸甲乙酯组成，以有机溶剂的总体积为100％计，碳酸乙烯酯的体积分数为30％，碳酸甲乙酯的体积分数为70％；以电解液质量百分数为100％算，有机溶剂占电解液的质量百分数为83.5％。
本实施例还提供一种上述电解液的制备方法，其具体方法为：
在氩气气氛下，向有机溶剂中加入配方量的不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B，之后加入电解质盐，在15℃温度下搅拌混合，得到所述电解液。
本实施例制备的电解液的测试结果见表1。
对比例1
本对比例提供的电解液除了所述添加剂中不含有不饱和碳酸酯添加剂，其他各方面均与实施例1的电解液相同。
本对比例制备的电解液的测试结果见表1。
对比例2
本对比例提供的电解液除了所述添加剂中不含有锂盐添加剂，其他各方面 均与实施例1的电解液相同。
本对比例制备的电解液的测试结果见表1。
对比例3
本对比例提供的电解液除了所述添加剂中不含有添加剂A，其他各方面均与实施例1的电解液相同。
本对比例制备的电解液的测试结果见表1。
对比例4
本对比例提供的电解液除了所述添加剂中不含有添加剂B，其他各方面均与实施例1的电解液相同。
本对比例制备的电解液的测试结果见表1。
对比例5
本对比例提供的电解液除了所述添加剂中不含有添加剂A，其他各方面均与实施例5的电解液相同。
本对比例制备的电解液的测试结果见表1。
对比例6
本对比例提供的电解液除了所述添加剂中不含有添加剂B，其他各方面均与实施例5的电解液相同。
本对比例制备的电解液的测试结果见表1。
测试方法
将各实施例和对比例提供的电解液应用于锂离子电池，用锂离子电池进行性能测试。测试用的锂离子电池的具体制备方法包括：将负极材料石墨、导电 剂乙炔黑和粘结剂SBR按质量百分比94:1:5制备成浆料涂覆于铜箔集流体上，真空烘干、制得负极极片；将正极材料NCM811、导电剂乙炔黑和粘结剂PVDF按质量比94:3:3制备成浆料涂覆于铝箔集流体上，真空烘干、制得正极极片。将正极极片、负极极片、Celgard2400隔膜以及实施例或对比例制备的电解液装配成软包电池，采用新威充放电测试柜进行电化学测试。
(1)锂离子电池的循环性能测试：
在25℃/45℃下，将锂离子电池以1.5C(标称容量)恒流充电到电压为4.2V，然后以4.2V恒压充电至电流≤0.05C，搁置10min后，以1C恒流放电至截至电压2.8V，以上为一次充放电循环。将锂离子电池按照上述条件进行25℃下1500次充放电循环；45℃下1000次充放电循环。
锂离子电池N次循环后的容量保持率(％)＝(第N次循环的放电容量/首次放电容量)×100％，N为锂离子电池的循环次数。
(2)锂离子电池的功率性能测试：
在25℃下，将锂离子电池以1C恒流充电到电压为4.2V，然后以4.2V恒压充电至电流为0.05C，然后，以1C恒流放电30min，即锂离子电池的荷电状态为50％SOC。之后分别在25℃以2C脉冲放电30s、-20℃以0.33C脉冲放电10s，测定其直流阻抗(DCR)，表征锂离子电池的常温功率性能和低温功率性能。
DCR＝(放电前电压-脉冲放电末期电压)/(放电电流)。
(3)锂离子电池的高温存储性能测试：
在25℃下，将锂离子电池以1C恒流充电到电压为4.2V，然后以4.2V恒压充电至电流为0.05C，测试锂离子电池的体积为V0；之后将锂离子电池放入60℃的恒温箱，分别储存30天、60天，且取出测试锂离子电池的体积并记为 Vn。
锂离子电池60℃存储n天后的体积膨胀率(％)＝(Vn-V0)/V0×100％。
测试结果如下表所示：
表1
Figure PCTCN2021073200-appb-000005
综合上述实施例和对比例可知，实施例提供的电解液中添加不饱和碳酸酯类添加剂作为负极成膜添加剂，在石墨负极表面形成致密的SEI膜，提高负极材料结构稳定性，降低电池循环阻抗，提高了电池循环性能；通过在电解液中添加锂盐类添加剂，通过强化正负极表面膜在高温下的稳定性，提高高温存储性能，抑制电池内的产气量；通过在电解液中添加添加剂A在负极形成致密且导锂性能好的SEI膜，有利于改善高温和功率特性；通过在电解液中添加添加剂B，由于具有酰胺结构，不仅能够稳定电解质盐，而且环状酰胺在正极氧化成膜后的正极膜与正极的某些包覆层(例如含硼包覆层)具有络合作用，有效提高了正极包覆层的稳定性，有利于改善电解液的高温性能，减少电池高温存储产气。
对比例1因为不含不饱和碳酸酯添加剂，导致循环性能下降。
对比例2因为不含锂盐添加剂，导致循环性能、低温功率性能下降。
对比例3、5因为不含添加剂A，导致高温循环性能、高温存储性能变差。
对比例4、6因为不含添加剂B，导致高温循环、高温存储性能显著恶化。
实施例1-4和对比例3、4的对比可知，在快充溶剂体系中，添加剂A、B的加入显著提高了电池的高温循环和高温存储，且常温循环无明显下降，常温DCR和低温DCR没有明显提高，证明添加剂A、B的加入能够使电池在保持原有的循环性能和功率性能的基础上，提高电池的高温性能。解决了高镍电池电解液快充循环性能、高温性能、常温和低温功率性能难以兼顾的问题。
实施例5与对比例5、6的对比可知，在非快充溶剂体系中，添加剂A、B的加入也能使电池在保持原有的循环性能和功率性能的基础上，提高电池的高温性能。
申请人声明，本申请通过上述实施例来说明本申请的详细方法，但本申请并不局限于上述详细方法，即不意味着本申请必须依赖上述详细方法才能实施。

Claims (12)

  1. 一种电解液，其包括添加剂，所述添加剂包括不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B，所述添加剂B包括异氰脲酸衍生物。
  2. 根据权利要求1所述的电解液，其中，所述异氰脲酸衍生物的结构通式为
    Figure PCTCN2021073200-appb-100001
    其中X包括甲基、乙基、正丙基、烯丙基、氯或氟。
  3. 根据权利要求1或2所述的电解液，其中，所述异氰脲酸衍生物包括异氰脲酸三甲酯、异氰脲酸三乙酯、异氰脲酸三丙酯、异氰脲酸三烯丙酯、三氟异氰脲酸、三氯异氰脲酸中的任意一种或至少两种的组合。
  4. 根据权利要求1-3中任一项所述的电解液，其中，所述不饱和碳酸酯添加剂包括碳酸亚乙烯酯、氟代碳酸乙烯酯或乙烯基碳酸乙烯酯中的任意一种或至少两种的组合；
    可选地，所述锂盐添加剂包括双氟磺酰亚胺锂、二氟磷酸锂、双草酸硼酸锂、双氟草酸硼酸锂、二氟双草酸磷酸锂或四氟草酸磷酸锂中的任意一种或至少两种的组合；
    可选地，所述添加剂A为磺丙酸酐衍生物；
    可选地，所述磺丙酸酐衍生物包括2-磺丙酸酐、3,4-二甲基-2-磺丙酸酐、4,4-二甲基-2-磺丙酸酐或2-磺基苯甲酸酐中的任意一种或至少两种的组合；
    可选地，所述电解液中，基于所述电解液的总质量为100％计，不饱和碳酸酯添加剂的质量分数为0.2-1.0％；
    可选地，所述电解液中，基于所述电解液的总质量为100％计，锂盐添加剂 的质量分数为0.5-2.0％；
    可选地，所述电解液中，基于所述电解液的总质量为100％计，添加剂A的质量分数为0.2-1.0％；
    可选地，所述电解液中，基于所述电解液的总质量为100％计，添加剂B的质量分数为0.1-1.0％。
  5. 根据权利要求1-4中任一项所述的电解液，其中，所述电解液还包括有机溶剂和电解质盐；
    可选地，所述电解液为高镍电池的电解液。
  6. 根据权利要求5所述的电解液，其中，所述有机溶剂包括环状碳酸酯和链状碳酸酯；
    可选地，所述环状碳酸酯包括碳酸乙烯酯和/或碳酸丙烯酯；
    可选地，所述链状碳酸酯包括碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯或碳酸甲丙酯中的任意一种或至少两种的组合；
    可选地，所述有机溶剂还包括链状羧酸酯；
    可选地，所述链状羧酸酯包括甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸丁酯、丁酸甲酯、丁酸乙酯或丁酸丁酯中的任意一种或至少两种的组合；
    可选地，所述有机溶剂中，基于所述有机溶剂的总体积为100％计，环状碳酸酯的体积分数为20-40％，碳酸二甲酯的体积分数为0-20％，除碳酸二甲酯外的其他链状碳酸酯的体积分数为40-70％，链状羧酸酯的体积分数为0-20％；
    可选地，所述有机溶剂由碳酸乙烯酯、碳酸二甲酯、碳酸甲乙酯和链状羧酸酯组成；
    可选地，所述有机溶剂中，基于所述有机溶剂的总体积为100％计，碳酸乙烯酯的体积分数为20-40％，碳酸二甲酯的体积分数为10-20％，碳酸甲乙酯的体积分数为40-70％，链状羧酸酯的体积分数为10-20％。
  7. 根据权利要求1-6中任一项所述的电解液，其中，所述电解质盐包括六氟磷酸锂、六氟砷酸锂、高氯酸锂、双氟磺酰亚胺锂、四氟硼酸锂和双三氟甲烷磺酰亚胺锂中的至少一种；
    可选地，所述电解液中，电解质盐的浓度为1.0-1.5mol/L。
  8. 一种如权利要求1-7中任一项所述的电解液的制备方法，其包括以下步骤：
    在保护性气氛下，将配方量的添加剂和其他原料混合，得到所述电解液，所述添加剂包括不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B。
  9. 根据权利要求8所述的制备方法，其中，所述其他原料包括配方量的有机溶剂和电解质盐；
    可选地，所述混合的原料加入顺序为向有机溶剂中加入添加剂，再加入电解质盐；
    可选地，所述混合为搅拌混合；
    可选地，所述混合的温度为5-20℃；
    可选地，所述保护性气氛包括氮气气氛和/或氩气气氛。
  10. 根据权利要求8或9所述的制备方法，其包括以下步骤：
    在保护性气氛下，向有机溶剂中加入配方量的不饱和碳酸酯添加剂、锂盐添加剂、添加剂A和添加剂B，之后加入电解质盐，搅拌混合，得到所述电解液。
  11. 一种锂离子电池，其包含如权利要求1-7任一项所述的电解液。
  12. 根据权利要求11所述的锂离子电池，其还包含正极、负极和隔膜；
    可选地，所述正极的活性物质为高镍三元材料；
    可选地，所述高镍三元材料为除锂之外，在其他三种金属元素中，以所述其他三种金属元素的总摩尔百分含量为100％计，镍元素的摩尔百分含量在50％以上的三元材料；
    可选地，所述正极的活性物质包括镍钴锰三元材料和/或镍钴铝三元材料；
    可选地，所述镍钴锰三元材料的化学式为：Li(Ni xCo yMn z)O 2，其中0.5<x≤0.8，0<y≤0.2，0<z≤0.3且x+y+z＝1；
    可选地，所述镍钴铝三元材料的化学式为：Li(Ni xCo yAl z)O 2，其中0.5<x≤0.8，0<y≤0.2，0<z≤0.05且x+y+z＝1；
    可选地，所述负极的活性物质包括石墨。
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