Electrolyte for lithium ion battery and lithium ion battery

Abstract

The application provides a kind of electrolyte for lithium ion battery and lithium ion battery, belong to lithium ion battery field, can solve the problem that the film formed by the polymerization of existing electrolyte additive is thick and dense, increases the film impedance, affects the performance of battery.The electrolyte for lithium ion battery comprises phosphoric acid derivative additive, the structural formula of phosphoric acid derivative additive is wherein, R1 is one of carboxylate group, dicarboxylic acid ester group, R2 is one of saturated or unsaturated alkyl, alkoxy, cyano-substituted alkyl, halogenated alkyl, phenyl, silane group containing 1-6 carbon atoms, R3 is cyano-substituted alkyl, R4 is one of saturated or unsaturated alkyl, alkoxy, cyano-substituted alkyl, halogenated alkyl, phenyl, silane group containing 1-6 carbon atoms.The application can be applied to lithium ion battery electrolyte, improve the performance of electrolyte, meet the requirements of long cycle life, good rate performance, adapt to high and low temperature environment of battery under high voltage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lithium ion batteries, and particularly relates to an electrolyte for lithium ion batteries and a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries are favored by various industries due to their high energy density, low self-discharge rate, long cycle life, cleanliness, and no pollution. Electronic mobile devices such as notebook computers, mobile phones, handheld game consoles, and tablet computers using lithium ion batteries can achieve more and more functions. The application technology of electric vehicles, smart grids, and other aspects is also becoming mature. At the same time, consumers have also put forward higher requirements for mutual consideration of battery energy density, cycle life, and environmental suitability. As an important carrier for ion transmission of lithium ion batteries, the composition and performance of electrolyte will greatly affect the cycle capacity and service life of the battery. Current battery design generally improves battery energy density by increasing the working voltage of the battery and increasing the compaction of the electrode sheet, which requires the electrolyte to have a higher electrochemical window and better compatibility with the electrode material.

[0003] Lithium ion batteries with conventional electrolyte systems often have low charge and discharge capacity and lithium precipitation at low temperatures due to increased electrolyte viscosity and reduced conductivity, which can cause the product to not work properly or even explode. At high temperatures, the electrolyte is easily volatilized, decomposed, and generates a large amount of heat, which can cause the battery to expand, deteriorate in performance, and even pose a safety hazard. Through research, the use of electrolyte solvents and additives can effectively improve the temperature cycling performance of lithium ion batteries. However, conventional carbonate-based electrolytes for lithium ion batteries are easily decomposed at high voltage, producing CO, CO2, and other organic compounds containing ester bonds and hydroxyl groups. At low voltage, decomposition occurs on the negative electrode surface, producing olefin gas, which can be trapped between the positive and negative electrodes, causing the battery performance to drop sharply and posing a threat to the safety of the battery, resulting in reduced charge and discharge efficiency and poor cycle performance of the lithium ion battery. In addition, lithium ion secondary batteries can release a large amount of heat under conditions of excessive charge and discharge, short circuit, and long-term operation at high current, which can cause catastrophic thermal breakdown, and even the battery can catch fire, explode, and other unsafe behaviors.

[0004] Chinese invention patent CN112290094A discloses a kind of high infiltration high safety electrolyte additive, electrolyte, preparation method and battery, wherein, high infiltration high safety electrolyte additive is halogenated alkyl benzene sulfonate allyl phosphate ester derivative.Electrolyte additive breaks and forms long straight chain alkyl benzene sulfonic acid lithium, which reduces the surface tension of electrolyte, improves its wettability, reduces the amount of electrolyte, and improves safety;Electrolyte additive greatly improves the flame retardant performance of electrolyte through a large number of F elements and aromatic groups;The film formed by electrolyte additive polymerization is thick and dense, and has high stability, which greatly reduces the short-circuit current of battery in needle test, thereby improving the safety performance of battery.

[0005] However, the film formed by the above-mentioned electrolyte additive polymerization is thick and dense, but increases the film impedance, thereby affecting the battery performance.Therefore, it is necessary to develop a new type of electrolyte additive to improve the performance of electrolyte and meet the requirements of long cycle life, good rate performance and adaptation to high and low temperature environment of battery under high voltage. SUMMARY

[0006] The present application aims to solve the technical problem that the film formed by the polymerization of the existing electrolyte additive is thick and dense, which increases the film impedance and affects the battery performance, and proposes a kind of electrolyte for lithium ion battery to improve the performance of electrolyte and meet the requirements of long cycle life, good rate performance and adaptation to high and low temperature environment of battery under high voltage.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a kind of electrolyte for lithium ion battery, the electrolyte for lithium ion battery includes phosphoric acid derivative additive, the structural formula of the phosphoric acid derivative additive is

[0008]

[0009] Among them, R1 is one of carboxylate group and dicarboxylic acid ester group, R2 is one of saturated or unsaturated hydrocarbon group, alkoxy group, cyano-substituted alkyl group, halogenated alkyl group, phenyl group and silane group containing 1-6 carbon atoms, R3 is cyano-substituted alkyl group, and R4 is one of saturated or unsaturated hydrocarbon group, alkoxy group, cyano-substituted alkyl group, halogenated alkyl group, phenyl group and silane group containing 1-6 carbon atoms.

[0010] As a preferred, the phosphoric acid derivative additive is one of the substances shown in the following structural formula:

[0011]

[0012]

[0013] As a preferred, the mass percentage of the phosphoric acid derivative additive in the electrolyte for lithium ion battery is 0.2-20%.

[0014] As preferred, the electrolyte for lithium ion battery further comprises a solvent, a lithium salt and an auxiliary additive, wherein the mass percentage of the solvent in the electrolyte for lithium ion battery is 50-98%, and the mass percentage of the lithium salt in the electrolyte for lithium ion battery is 1-18%.

[0015] As preferred, the solvent is at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dimethyl ether, diethyl ether, hexanedinitrile, butanedinitrile, pentanedinitrile, dimethyl sulfoxide, sulfolane, 1,4-butyrolactone, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate.

[0016] As preferred, the lithium salt is at least one of lithium hexafluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide.

[0017] As preferred, the auxiliary additive is at least one of a first auxiliary additive and a second auxiliary additive, wherein the first auxiliary additive is at least one of 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sulfonic acid lactone, ethylene sulfate, propylene sulfate, butylene sulfite, ethylene carbonate, vinylene carbonate, fluorinated ethylene carbonate, and the second auxiliary additive is at least one of lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate, lithium difluoro(oxalato)phosphate, lithium difluorophosphate, lithium tetrafluoroborate.

[0018] As preferred, the mass percentage of the first auxiliary additive in the electrolyte for lithium ion battery is 0.1-3.0%, and the mass percentage of the second auxiliary additive in the electrolyte for lithium ion battery is 0-1.0%.

[0019] Another aspect of the present application provides a lithium ion battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is any of the electrolytes for lithium ion battery described above.

[0020] As preferred, the lithium ion battery is prepared by the following method, comprising the following steps:

[0021] Preparation of positive electrode sheet: sequentially adding a binder, a conductive agent and a positive electrode active material into a solvent, fully stirring and mixing to obtain a first slurry, coating the first slurry on an aluminum foil current collector, drying, cold pressing and punching to obtain a positive electrode sheet;

[0022] Negative sheet preparation: the binder, negative active material are added into deionized water in turn, and are fully stirred and mixed to obtain a second slurry, the second slurry is coated on a copper foil current collector, and is dried, cold-pressed, and punched to obtain a negative sheet;

[0023] Electrolyte preparation: in an inert gas-filled glove box, lithium salt is added into a solvent, and then a phosphoric acid derivative additive and an auxiliary additive are added, and the electrolyte is obtained by stirring at room temperature;

[0024] Lithium ion battery preparation: the positive sheet, the negative sheet and the separator are subjected to a winding process to prepare a square cell, the bare cell is placed in an outer package, the electrolyte is injected into the dried battery, and the lithium ion battery is prepared through packaging, standing, formation, shaping, capacity distribution and the like.

[0025] Compared with the prior art, the advantages and positive effects of the present application are that: the electrolyte for lithium ion battery of the present application comprises a phosphoric acid derivative additive, the phosphoric acid derivative additive contains a cyano functional group, which can be complexed with metal ions to inhibit the irreversible oxidation reaction of organic solvents on the positive electrode surface, thereby improving the oxidation resistance of the electrolyte; the phosphoric acid derivative additive contains a carboxylate group, the presence of this structure can improve the compatibility of the additive with the positive and negative electrode materials, reduce the viscosity of the electrolyte, and improve the Li + Conductivity rate; the phosphoric acid derivative additive contains an amine group with "Lewis" basicity in the molecule, which can be complexed with trace amounts of HF and PF5 in the electrolyte, thereby effectively improving the stability of the electrolyte; the above structural features of the phosphoric acid derivative additive are beneficial to improving the high-voltage cycle performance of the battery and inhibiting the gas production during high-temperature storage; the phosphoric acid derivative additive contains N and P elements, which makes the additive have a certain flame retardant effect. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0027] The electrolyte for lithium ion battery of the present application comprises a phosphoric acid derivative additive, and the structural formula of the phosphoric acid derivative additive is

[0028]

[0029] Wherein, R1 is one of carboxylate group, dicarboxylate group, R2 is one of saturated or unsaturated alkyl group containing 1-6 carbon atoms, alkoxy group, cyano-substituted alkyl group, halogenated alkyl group, phenyl group, silane group, R3 is cyano-substituted alkyl group, and R4 is one of saturated or unsaturated alkyl group containing 1-6 carbon atoms, alkoxy group, cyano-substituted alkyl group, halogenated alkyl group, phenyl group, silane group.

[0030] The cyano functional group contained in the phosphoric acid derivative additive can be complexed with metal ions to inhibit irreversible oxidation reaction of organic solvents on the surface of the positive electrode, and improve the oxidation resistance of the electrolyte; the carboxylate group contained in the phosphoric acid derivative additive can improve the compatibility of the additive with the positive and negative electrode materials, reduce the viscosity of the electrolyte, and improve the Li + Conduction rate; the amine group with "Lewis" basicity contained in the phosphoric acid derivative additive can effectively improve the stability of the electrolyte by complexing with trace amounts of HF and PF5 in the electrolyte. The above structural features of the phosphoric acid derivative additive of the application are beneficial to improve the high-pressure cycle performance of the battery and inhibit the gas production during high-temperature storage. In addition, the N and P elements contained in the phosphoric acid derivative additive make the phosphoric acid derivative additive have certain flame-retardant effect.

[0031] The mass percentage of the phosphoric acid derivative additive in the electrolyte is 0.2-20%, and the phosphoric acid derivative additive includes but is not limited to one of the substances represented by the following formula (III)-formula (XII):

[0032]

[0033]

[0034] The electrolyte for lithium ion batteries also comprises a solvent, a lithium salt and an auxiliary additive, wherein the mass percentage of the solvent in the electrolyte for lithium ion batteries is 50-98%, the solvent is at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dimethyl ether, diethyl ether, hexanedinitrile, butanedinitrile, pentanedinitrile, dimethyl sulfoxide, cyclobutyl sulfone, 1,4-butyrolactone, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate; the mass percentage of the lithium salt in the electrolyte for lithium ion batteries is 1-18%, and the lithium salt is at least one of lithium hexafluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide; the auxiliary additive is at least one of a first auxiliary additive and a second auxiliary additive, wherein the mass percentage of the first auxiliary additive in the electrolyte for lithium ion batteries is 0.1-3.0%, and the first auxiliary additive is at least one of 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sulfonic acid lactone, ethylene sulfate, propylene sulfate, butylene sulfite, ethylene carbonate, vinylene carbonate and fluorinated ethylene carbonate; the mass percentage of the second auxiliary additive in the electrolyte for lithium ion batteries is 0-1.0%, and the second auxiliary additive is at least one of lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate, lithium difluoro(oxalate)phosphate and lithium difluorophosphate.

[0035] The application also provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is the electrolyte for lithium ion batteries described above.

[0036] Preparation of the positive electrode sheet: the binder, the conductive agent and the positive electrode active material are sequentially added to the solvent, and are fully stirred and mixed to obtain a first slurry, the first slurry is coated on an aluminum foil current collector, and is dried, cold-pressed and punched to obtain the positive electrode sheet;

[0037] Preparation of the negative electrode sheet: the binder and the negative electrode active material are sequentially added to deionized water, and are fully stirred and mixed to obtain a second slurry, the second slurry is coated on a copper foil current collector, and is dried, cold-pressed and punched to obtain the negative electrode sheet;

[0038] Preparation of the electrolyte: in a glove box filled with inert gas, the lithium salt is added to the solvent, and then the phosphoric acid derivative additive and the auxiliary additive are added, and the electrolyte is obtained by stirring at room temperature, wherein the mass percentage of the solvent in the electrolyte is 74.5-87.5% of the total mass of the electrolyte;

[0039] Lithium ion battery preparation: the positive plate, the negative plate and the separator are made into square cells through the winding process, the bare cells are placed in the outer package, the electrolyte is injected into the dried battery, and the lithium ion battery is prepared through packaging, standing, formation, shaping, capacity distribution, etc.

[0040] In order to more clearly and detailedly introduce the electrolyte for lithium ion battery provided by the embodiments of the present application, the following will be described in combination with specific embodiments.

[0041] Example 1

[0042] The electrolyte component and additive ratio of Example 1 are shown in Table 1.

[0043] According to the capacity design (2000mAh) of the battery, the coating area density is determined according to the capacity of the positive and negative electrode materials. The positive active material is a high-voltage lithium cobaltate material from Tianjin Bamotech, the negative active material is a artificial graphite material from Jiangxi Zichen, and the separator is a PE ceramic coated separator with a thickness of 20μm purchased from Xingyuan Material.

[0044] The preparation method of the lithium ion battery of Example 1 includes the following steps:

[0045] Preparation of positive plate: 3% polyvinylidene fluoride (PVDF), 2% conductive agent super P and 95% lithium cobaltate (LiCoO2) were weighed and added to N-methyl pyrrolidone (NMP) in turn, and were fully stirred and mixed to obtain a first slurry. The first slurry was coated on an aluminum foil current collector, dried, cold-pressed, and punched to obtain a positive plate;

[0046] Preparation of negative plate: 2% CMC, 3% SBR and 94% graphite were weighed and added to deionized water in turn, and were fully stirred and mixed to obtain a second slurry. The second slurry was coated on a copper foil current collector, dried, cold-pressed, and punched to obtain a negative plate;

[0047] Preparation of electrolyte: in an argon-filled glove box, ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (EMC) were mixed in a weight ratio of EC:DEC:EMC=1:1:1 to obtain a mixed solvent. 12.5% lithium hexafluorophosphate (1mol / L) of the total mass of the electrolyte was added to the above-mentioned mixed solvent, and the phosphoric acid derivative additive shown in structural formula (III) shown in Table 1, 0.5% vinylene carbonate (VC), 1.0% fluoroethylene carbonate (FEC), 1.0% 1,3-propane sulfone (PS) were added, and the electrolyte was obtained by stirring at room temperature. The proportion of the additive is the proportion of the total weight of the electrolyte;

[0048] Lithium ion battery preparation: the above positive plate, negative plate and PE coated ceramic separator are subjected to a winding process to make a square cell, the naked cell is placed in an outer package, the above prepared electrolyte is injected into the dried battery, and the lithium ion battery is prepared after packaging, standing, formation, shaping, capacity distribution, etc.

[0049] Examples 2-14

[0050] The electrolyte component and additive ratio of Examples 2-14 are shown in Table 1, respectively.

[0051] The preparation method of lithium ion battery of Examples 2-14 is the same as that of Example 1.

[0052] Comparative Examples 1-3

[0053] The electrolyte component and additive ratio of Comparative Examples 1-3 are shown in Table 1, respectively.

[0054] The preparation method of lithium ion battery of Comparative Examples 1-3 is the same as that of Example 1.

[0055] Among them, the phosphoric acid derivative additive used in Examples 1-14 is selected from the substances shown in formula (III) to formula (XII), the structural formula of the additive in Comparative Example 1 is shown in formula (XIII), the structural formula of the additive in Comparative Example 2 is shown in formula (XIV), and no phosphoric acid derivative additive is added in Comparative Example 3.

[0056]

[0057] Table 1: Electrolyte component and additive ratio

[0058]

[0059]

[0060] Performance test

[0061] The lithium ion batteries obtained in Examples 1-14 and Comparative Examples 1-3 are subjected to normal temperature cycle performance test, high temperature storage performance test, and self-extinguishing time test of electrolyte, and the test results are shown in Table 2, and the test methods are as follows:

[0062] Normal temperature cycle performance test

[0063] At 25°C, the lithium cobaltate battery after formation is charged to 4.45V with 1C constant current and constant voltage, and then discharged to 3.0V with 1C constant current, and the capacity retention rate of the 500th cycle is calculated after 500 cycles of charge and discharge, and the calculation formula is as follows:

[0064] The capacity retention rate of the 500th cycle (%) = (the 500th cycle discharge capacity / the 1st cycle discharge capacity) x 100%.

[0065] High temperature storage performance test

[0066] After the formation of the battery at room temperature with 0.5C constant current constant voltage to 4.45V, measure the initial thickness of the battery, initial discharge capacity, then store at 85℃ for 4h, wait for the battery to cool to room temperature to measure the final thickness of the battery, calculate the thickness expansion rate of the battery; then 0.5C discharge to 3.0V to measure the retention capacity and recovery capacity of the battery. The calculation formula is as follows:

[0067] Battery thickness expansion rate (%) = (final thickness-initial thickness) / initial thickness * 100%;

[0068] Battery capacity retention rate (%) = retention capacity / initial capacity * 100%

[0069] Battery capacity recovery rate (%) = recovery capacity / initial capacity * 100%

[0070] Electrolyte self-extinguishing time test

[0071] Take a PP or PE separator with length* width = 20cm*40cm, immerse the separator in the electrolyte sample for 5min, then use tweezers to take out the electrolyte- immersed separator, use a lighter to ignite the electrolyte- immersed separator, and record the combustion condition of the electrolyte- immersed separator and the time from combustion to automatic extinguishing.

[0072] Table 2 Performance test table of examples 1-14 and comparative examples 1-3

[0073]

[0074]

[0075] As can be seen from the above, the phosphoric acid ester derivative additive is added in examples 1-14, compared with the electrolyte containing phosphoric acid ester additive in comparative examples 1-2, has better cycle performance and high temperature storage performance, and the fluorinated alkyl group can improve the coulomb efficiency and cycle performance; appropriately increasing the content of the phosphoric acid ester derivative additive can effectively inhibit the gas expansion rate; the phosphorus-containing additive is added in examples 1-14, compared with the electrolyte without adding phosphorus-containing additive in comparative example 3, the self-extinguishing time of the electrolyte with phosphorus-containing additive is shorter than that of the electrolyte without adding phosphorus-containing additive, which shows that the phosphoric acid ester derivative additive has certain flame retardant ability, especially the structure with fluorine substitution, the flame retardant effect is better. In summary, the electrolyte for lithium ion battery using the technical scheme of the present application has higher oxidation potential and is not easy to decompose under high pressure and high temperature conditions, and has good flame retardant effect, improves the cycle life and safety of the lithium ion battery.

[0076] The above merely illustrates the embodiments of the present application, and is not intended to limit the patent scope of the present application, and any equivalent transformation or direct or indirect application in the related technical field based on the content of the present application should be included in the patent protection scope of the present application.

Claims

1. An electrolyte for a lithium ion battery, characterized by comprising The electrolyte for the lithium ion battery comprises a phosphoric acid derivative additive, the structural formula of the phosphoric acid derivative additive is Formula (I) or Formula (II), wherein, R1 is a dicarboxylic acid ester group, R2 is one of saturated or unsaturated alkyl groups containing 1-6 carbon atoms, alkoxy, cyano-substituted alkyl, halogenated alkyl, phenyl, silane group, R3 is cyano-substituted alkyl, and R4 is one of saturated or unsaturated alkyl groups containing 1-6 carbon atoms, alkoxy, cyano-substituted alkyl, halogenated alkyl, phenyl, silane group.

2. The electrolyte for a lithium-ion battery according to claim 1, characterized by The phosphoric acid derivative additive is one of substances shown in formula (III)-formula (XII): Formula (III) Formula (IV) Formula (V) Formula (VI) Formula (VII) Formula (VIII) Formula (IX) Formula (X) Formula (XI) Formula (XII).

3. The electrolyte for a lithium-ion battery according to claim 1, characterized by, The mass percentage of the phosphoric acid derivative additive in the electrolyte for the lithium ion battery is 0.2-20%.

4. The electrolyte for lithium-ion batteries according to claim 1, characterized by The electrolyte for the lithium ion battery further comprises a solvent, a lithium salt and an auxiliary additive, wherein the mass percentage of the solvent in the electrolyte for the lithium ion battery is 50-98%, and the mass percentage of the lithium salt in the electrolyte for the lithium ion battery is 1-18%.

5. The electrolyte for a lithium-ion battery according to claim 4, characterized by The solvent is at least one of vinyl carbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dimethyl ether, diethyl ether, hexanedinitrile, butanedinitrile, pentanedinitrile, dimethyl sulfoxide, cyclobutane sulfone, 1,4-butyrolactone, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate.

6. The electrolyte for lithium-ion batteries according to claim 4, characterized in that, The lithium salt is at least one of lithium hexafluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

7. The electrolyte for lithium-ion batteries according to claim 4, characterized in that, The auxiliary additive is at least one of a first auxiliary additive and a second auxiliary additive, wherein the first auxiliary additive is at least one of 1,3-propane sultone, 1,4-butane sultone, propylene-1,3-sulfonic acid lactone, ethylene sulfate, propylene sulfate, butylene sulfite, vinyl carbonate, vinylene carbonate and fluoro-vinyl carbonate, and the second auxiliary additive is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium difluoro(oxalato)borate, lithium difluoro(oxalate)phosphate and lithium difluorophosphate.

8. The electrolyte for lithium-ion batteries according to claim 7, characterized in that, The mass percentage of the first auxiliary additive in the electrolyte for the lithium ion battery is 0.1-3.0%, and the mass percentage of the second auxiliary additive in the electrolyte for the lithium ion battery is 0-1.0%.

9. A lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that, The electrolyte is the electrolyte for the lithium ion battery according to any one of claims 1-8.

10. The lithium-ion battery of claim 9, wherein, The electrolyte is prepared by the following method comprising the following steps: Preparation of positive electrode sheet: sequentially adding a binder, a conductive agent and a positive electrode active material into a solvent, fully stirring and mixing to obtain a first slurry, coating the first slurry on an aluminum foil current collector, drying, cold pressing and punching to obtain a positive electrode sheet; Preparation of negative electrode sheet: sequentially adding a binder and a negative electrode active material into deionized water, fully stirring and mixing to obtain a second slurry, coating the second slurry on a copper foil current collector, drying, cold pressing and punching to obtain a negative electrode sheet; Electrolyte preparation: in the glove box filled with inert gas, the lithium salt is added into the solvent, and then the phosphoric acid derivative additive and the auxiliary additive are added, and the electrolyte is obtained by stirring at room temperature; Lithium ion battery preparation: the positive electrode sheet, the negative electrode sheet and the separator are subjected to a winding process to prepare a square cell, the bare cell is placed in an outer package, the electrolyte is injected into the dried battery, and the lithium ion battery is prepared after packaging, standing, formation, shaping, capacity distribution and the like.

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