High-temperature-resistant and flame-retardant double-salt lithium battery electrolyte, preparation method and application thereof

Abstract

The application discloses a high-temperature-resistant and flame-retardant double-salt lithium battery electrolyte, which comprises a lithium salt, an ether organic solvent, a phosphate organic solvent and a diluent, and the lithium salt comprises a main salt and a secondary salt. The raw materials required by the electrolyte are simple to prepare and have superior high-temperature performance, and when the electrolyte is applied to a lithium ion battery with a high-nickel material as a positive electrode, the electrochemical performance of the battery, in particular, the cycle performance, is obviously improved. Compared with the prior art, the electrolyte has the advantages of non-flammability, high-temperature resistance, improved cycle performance and rate performance of the battery, and the electrolyte can make the lithium ion battery have very excellent high-temperature cycle performance and has a very excellent capacity retention rate in a high-temperature environment above 60 DEG C, which is significantly better than a lithium ion battery prepared by using a commercial electrolyte.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a high-temperature-resistant and flame-retardant double-salt lithium battery electrolyte as well as a preparation method and application thereof. BACKGROUND

[0002] As a new chemical energy, lithium battery has been widely used in people's production and living fields due to its excellent energy density, high working voltage, long cycle life and environmental friendliness. It has been widely used not only in mobile phones, notebook computers, camcorders and other portable electronic devices, but also is considered as an ideal power source for future electric vehicles and hybrid electric vehicles. This development trend gives lithium batteries a wide application prospect and huge economic benefits.

[0003] Lithium battery electrolyte, as a key component for ion transport, is usually composed of lithium salt and organic solvent. Its main function is to transport ions between the positive and negative electrodes of lithium batteries, thereby ensuring that lithium-ion batteries have superior performance such as high voltage and high specific energy. The formulation of electrolyte generally includes high-purity organic solvents, electrolyte lithium salts, and necessary additives, which are prepared by mixing in a certain proportion under certain conditions. LiAlCl4+SO2 in traditional electrolyte is an electrolyte that can obtain high cycle efficiency. The lithium metal electrode cycle efficiency of this electrolyte is close to 100%. However, due to the strong corrosiveness of this electrolyte and the volatility of SO2, it is easy to pollute the environment, and the preparation process requires high requirements, so it is not suitable for practical application. In addition, LiAsF6 / DOL system electrolyte can also achieve high cycle efficiency at low current density. However, the solute LiAsF6 in this electrolyte is toxic, and the system is not stable enough and is easy to decompose at high temperature. Especially in high temperature environment (>55℃), the stability of lithium battery electrolyte will decrease sharply, which has a great safety hazard. Therefore, when selecting electrolyte, factors such as cycle efficiency, toxicity, environmental friendliness and stability need to be considered to ensure that lithium batteries can perform well in actual use and meet the requirements of safety and environmental protection. The aging speed of lithium battery is significantly affected by temperature. As the internal temperature of lithium battery rises, the internal resistance of the battery increases, leading to a decrease in battery capacity and thus shortening the service life of lithium battery. In extreme cases, too high a temperature may even cause an explosion. Therefore, researchers have been actively exploring new high-temperature-resistant lithium battery electrolytes to expand the working temperature range of lithium batteries, so that they can operate normally at temperatures higher than 60℃, thereby expanding the application field of lithium batteries. For example, a patent with the patent application number "CN201410116478.0" discloses a high-temperature lithium battery electrolyte. The electrolyte includes non-aqueous organic solvent, lithium salt and electrolyte additive. The electrolyte additive is thioacyl dipropionitrile, which contains two terminal cyano groups and a sulfone group, and its amount is between 0.3wt% and 5wt% of the total weight of the electrolyte. Studies have shown that this electrolyte effectively improves the cycle performance of lithium batteries in high temperature (55℃) environment. However, it is worth noting that this electrolyte still shows relatively poor discharge performance at high temperatures above 60℃. This challenge shows that although some progress has been made, achieving superior performance of lithium batteries in high temperature environment is still an area that needs continuous research and improvement. Future research may need to focus on finding more innovative and feasible solutions to overcome the problem of lithium battery performance degradation under high temperature conditions.

[0004] Therefore, it is of great significance to develop an electrolyte with excellent high-temperature cycle performance and flame retardancy for improving the safety of batteries. SUMMARY

[0005] The application provides a high-temperature-resistant and flame-retardant double-salt lithium battery electrolyte, a preparation method and application thereof, and aims to solve the above technical problems.

[0006] The application provides a high-temperature-resistant and flame-retardant double-salt lithium battery electrolyte, which comprises a lithium salt, an ether organic solvent, a phosphate organic solvent and a diluent, the lithium salt comprises a main salt and a secondary salt, the main salt accounts for 70-95% of the total mass of the lithium salt, the secondary salt accounts for 5-30% of the total mass of the lithium salt, the main salt is selected from any one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(nonafluorobutylsulfonyl)imide, lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide, lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium perfluoroethylsulfonate, lithium perfluorobutylsulfonate and lithium n-perfluorobutylsulfonylimide, and the secondary salt is selected from any one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium difluorodioxalate phosphate, lithium difluoroborate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium tetracyano borate, lithium tetrakis(trifluoromethyl)borate, lithium pentafluoroethyltrifluoroborate, lithium fluorododecaborate, lithium tetramethoxyborate, lithium perfluoro-t-butoxytrifluoroborate, lithium nitrate and lithium perchlorate.

[0007] Preferably, the main salt is lithium bis(fluorosulfonyl)imide, and the secondary salt is lithium difluoro oxalate borate.

[0008] Further, the ether organic solvent has a general structure of R1O(CH2) r OR2, wherein r is 1-4, R1 and R2 are independently selected from any one of methyl, ethyl, chlorine, fluorine, monochloromethyl, dichloromethyl, trichloromethyl, monofluoromethyl, difluoromethyl and trifluoromethyl.

[0009] Further, the phosphate organic solvent has a general structure of P(=O)-(OR3)3, wherein R3 is selected from any one of methyl, ethyl, propyl, butyl, monofluoromethyl, difluoromethyl, trifluoromethyl and phenyl.

[0010] Further, the diluent is selected from any one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, fluorobenzene and 1,2-difluorobenzene.

[0011] Further, the mass percentage of the lithium salt is 20-40wt%, the mass percentage of the ether organic solvent is 15-30wt%, the mass percentage of the phosphate organic solvent is 20-30wt%, and the mass percentage of the diluent is 20-40wt%, based on the total mass of the lithium salt, the ether organic solvent, the phosphate organic solvent and the diluent being 100%.

[0012] Preferably, the mass percentage of the lithium salt is 33wt%, the mass percentage of the ether organic solvent is 17wt%, the mass percentage of the phosphate organic solvent is 20wt%, and the mass percentage of the diluent is 30wt%, based on the total mass of the lithium salt, the ether organic solvent and the phosphate organic solvent being 100%.

[0013] The application also provides a preparation method of the above-mentioned double-salt lithium battery electrolyte, comprising the following steps:

[0014] The ether organic solvent and the phosphate organic solvent are dehydrated.

[0015] The lithium salt is dried at 80-120℃.

[0016] The ether organic solvent and the phosphate organic solvent are mixed in proportion, the lithium salt and the diluent are added, and the mixture is uniformly mixed until completely dissolved to obtain the double-salt lithium battery electrolyte.

[0017] Further, the dehydration and the drying are performed in a glove box.

[0018] Further, the temperature of the drying is 100℃.

[0019] Further, the humidity in the glove box is less than 0.01ppm.

[0020] Further, the dehydration method is selected from any one or more of distillation, addition of molecular sieves and addition of drying substances.

[0021] Further, the drying substance is selected from any one or more of calcium hydride, activated carbon, anhydrous calcium oxide, lithium hydride, calcium chloride, phosphorus pentoxide, alkali metal and alkaline earth metal.

[0022] Preferably, the mixing method is stirring, and the stirring time is 12 hours.

[0023] The application provides an application of the above-mentioned double-salt lithium battery electrolyte in a lithium ion battery, and the positive electrode material of the lithium ion battery is one of lithium iron phosphate, lithium cobaltate, ternary, lithium-rich manganese-based and other positive electrode materials.

[0024] Preferably, the lithium ion battery is a ternary positive electrode made button lithium battery, the positive electrode of the ternary positive electrode button lithium battery is a ternary positive electrode material (ternary layered lithium nickel cobalt manganese oxide), the negative electrode material is a lithium sheet, the positive and negative electrodes are PP films, and the electrolyte is the double-salt lithium battery electrolyte.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] The present application uses ether ester mixed organic solvents with specific proportions and types as electrolyte solvents, and uses lithium salts with specific proportions and types as electrolyte salts, which improves the safety performance of the battery under high temperature conditions. The main salt of the present application is an organic lithium salt, the anion radius is large, the charge distribution is relatively dispersed, and the electron delocalization effect is strong, which reduces the lattice energy of the lithium salt, weakens the bonding effect between the anion and the cation, increases the solubility and improves the electrolyte conductivity, and is also beneficial to the improvement of electrochemical and thermal stability; the secondary salt has good passivation effect on aluminum foil, can effectively prevent the corrosion of organic lithium salt on aluminum foil, can improve the compatibility of electrolyte and lithium metal negative electrode, optimize the SEI film, thereby improving the cycle and rate performance of the battery. The present application selects the main salt and the secondary salt to be used in combination, which can combine the advantages and avoid the corresponding defects, so that the electrolyte has high ion conductivity and good positive and negative electrode compatibility.

[0027] The phosphate organic solvent used in the present application has good stability, high flash point and high dielectric constant, can well dissolve lithium salt and is miscible with other solvents; the ether organic solvent used in the present application has low viscosity, can improve the ion conductivity of the electrolyte and improve the rate performance, and has good compatibility with the lithium metal negative electrode, can optimize the properties of the negative electrode interface SEI film, and the SEI film generated on the electrode surface is more stable under high temperature conditions. The phosphate organic solvent and the ether organic solvent are mixed as the electrolyte organic solvent, which has the advantages of non-flammability, high temperature resistance, improved cycle performance and rate performance of the battery.

[0028] The raw materials required by the electrolyte of the present application are simple to prepare and have excellent high temperature performance. When the electrolyte is applied to a lithium ion battery with high nickel material (NCM811) as the positive electrode, the electrochemical performance of the battery, especially the cycle performance, is significantly improved. Compared with the prior art, the electrolyte of the present application has the advantages of non-flammability, high temperature resistance, improved cycle performance and rate performance of the battery. The electrolyte of the present application can make the lithium ion battery have very excellent high temperature cycle performance and very excellent capacity retention rate under high temperature environment above 60 DEG C, which is significantly better than the lithium ion battery prepared by the commercial electrolyte.

[0029] The electrolyte of the present application has the following advantages:

[0030] (1) Compared with the current commercial electrolyte, the electrolyte of the application has the characteristics of high flash point and non-combustibility;

[0031] (2) Compared with the current commercial electrolyte (the highest use temperature is not more than 45 DEG C), the lithium salt and solvent used in the electrolyte of the application are more suitable for high-temperature 60 DEG C cycle and have the effect of high-temperature resistance, which can be used at 60 DEG C high temperature;

[0032] (3) Compared with the current commercial electrolyte, the electrolyte of the application has excellent rate performance at high temperature;

[0033] (4) The organic solvent used in the application can ensure that the electrolyte is fully dissolved, and the SEI film generated on the electrode surface under high temperature conditions is more stable;

[0034] (5) The component ratio of the electrolyte of the application is reasonable, has good charge-discharge and high-temperature cycle stability, and is suitable for power lithium batteries working at high temperature. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the application. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0036] Figure 1 The NCM811 ternary lithium battery cycle performance comparison chart of the electrolyte prepared for example 1, example 2, comparative example 1 and comparative example 2 under the conditions of 2.7-4.3V, 60 DEG C high temperature, 1C charge-discharge;

[0037] Figure 2 The NCM811 ternary lithium battery charge-discharge curve chart of the electrolyte prepared for example 1 under the conditions of 2.7-4.3V, 60 DEG C high temperature, 1C charge-discharge;

[0038] Figure 3 The NCM811 ternary lithium battery rate performance comparison chart of the electrolyte prepared for example 1 and comparative example 1 under the conditions of 2.7-4.3V, 60 DEG C high temperature, different rates;

[0039] Figure 4 The coulomb efficiency comparison chart of the Li-Cu battery of the electrolyte prepared for example 1 and comparative example 1.

[0040] Wherein, the higher the coulomb efficiency, the better the compatibility with the negative electrode. DETAILED DESCRIPTION

[0041] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in conjunction with embodiments and drawings. It should be understood that the specific embodiments described herein are only intended to explain the present application and not to limit the present application. The present application will be specifically introduced below in conjunction with specific embodiments.

[0042] The embodiment of the present application provides a high-temperature-resistant and flame-retardant double-salt lithium battery electrolyte, the electrolyte comprises a lithium salt, an ether organic solvent, a phosphate organic solvent and a diluent.

[0043] Specifically, the lithium salt comprises a main salt and a secondary salt, wherein the main salt accounts for 70% to 95% of the total mass of the lithium salt, and the secondary salt accounts for 5% to 30% of the total mass of the lithium salt.

[0044] Specifically, the main salt is selected from any one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(nonafluorobutylsulfonyl)imide, lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylimide, lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, lithium trifluoromethanesulfonate, lithium perfluoroethylsulfonate, lithium perfluorobutylsulfonate and lithium n-perfluorobutylsulfonylimide.

[0045] Specifically, the secondary salt is selected from any one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium difluorodioxalate phosphate, lithium difluoroborate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium tetracyanoborate, lithium tetrakis(trifluoromethyl)borate, lithium pentafluoroethyltrifluoroborate, lithium fluorododecaborate, lithium tetramethoxyborate, lithium perfluoro-t-butoxytrifluoroborate, lithium nitrate and lithium perchlorate.

[0046] Preferably, the main salt is lithium bis(fluorosulfonyl)imide, and the secondary salt is lithium difluoro oxalate borate.

[0047] Specifically, the ether organic solvent has a general structure of R1O(CH2) r OR2, wherein r is 1-4, and R1 and R2 are independently selected from any one of methyl, ethyl, chlorine, fluorine, monochloromethyl, dichloromethyl, trichloromethyl, monofluoromethyl, difluoromethyl and trifluoromethyl.

[0048] Specifically, the phosphate organic solvent has a general structure of P(=O)-(OR3)3, wherein R3 is selected from any one of methyl, ethyl, propyl, butyl, monofluoromethyl, difluoromethyl, trifluoromethyl and phenyl.

[0049] Specifically, the diluent is selected from any one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, fluorobenzene and 1,2-difluorobenzene.

[0050] Specifically, the mass percentage of the lithium salt is 20-40wt%, the mass percentage of the ether organic solvent is 15-30wt%, the mass percentage of the phosphate organic solvent is 20-30wt%, and the mass percentage of the diluent is 20-40wt%, based on the total mass of the lithium salt, the ether organic solvent, the phosphate organic solvent and the diluent being 100%.

[0051] Preferably, the mass percentage of the lithium salt is 33wt%, the mass percentage of the ether organic solvent is 17wt%, the mass percentage of the phosphate organic solvent is 20wt%, and the mass percentage of the diluent is 30wt%, based on the total mass of the lithium salt, the ether organic solvent and the phosphate organic solvent being 100%.

[0052] The embodiment of the present application also provides a preparation method of the double-salt lithium battery electrolyte.

[0053] The ether organic solvent and the phosphate organic solvent are dehydrated.

[0054] The lithium salt is dried at 80-120℃.

[0055] The ether organic solvent and the phosphate organic solvent are mixed in proportion, the lithium salt and the diluent are added, and the mixture is uniformly mixed until completely dissolved to obtain the double-salt lithium battery electrolyte.

[0056] Specifically, the dehydration and the drying are performed in a glove box.

[0057] Preferably, the temperature of the drying is 100℃.

[0058] Specifically, the humidity in the glove box is less than 0.01ppm.

[0059] Specifically, the dehydration method is selected from any one or more of distillation, addition of molecular sieves and addition of drying substances.

[0060] Specifically, the drying substance is selected from any one or more of calcium hydride, activated carbon, anhydrous calcium oxide, lithium hydride, calcium chloride, phosphorus pentoxide, alkali metal and alkaline earth metal.

[0061] Preferably, the mixing mode is stirring, and the stirring time is 12 hours.

[0062] The application provides application of the double-salt lithium battery electrolyte in a lithium ion battery.

[0063] Preferably, the lithium ion battery is a ternary positive electrode made button lithium battery, the positive electrode of the ternary positive electrode button lithium battery is a ternary positive electrode material (ternary layered lithium nickel cobalt manganese oxide), the negative electrode material is a lithium sheet, the positive electrode and the negative electrode are separated by a PP film, and the electrolyte is the double-salt lithium battery electrolyte.

[0064] The application is described below in combination with specific examples.

[0065] Example 1

[0066] The electrolyte is prepared according to the following steps:

[0067] (1) lithium bisfluorosulfonylimide (LiFSI) is selected as a main salt, lithium difluoro(oxalato)borate (LiDFOB) is selected as a secondary salt, ethylene glycol dimethyl ether (DME) is selected as an ether organic solvent, triethyl phosphate (TEP) is selected as a phosphate organic solvent, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) is selected as a diluent;

[0068] (2) in a glove box with humidity less than 0.01 ppm, molecular sieves are added to DME and TEP respectively for water removal, and then left to stand for 12 hours; LiFSI and LiDFOB are placed in the glove box and then dried at 100 DEG C.

[0069] (3) 17% of DME, 20% of TEP, 30% of TTE, 30% of LiFSI and 3% of LiDFOB are weighed according to the mass percentage, so that the total concentration of lithium salts (including the main salt and the secondary salt) in the electrolyte is 3 mol / L, and then the mixture is fully mixed and uniformly dissolved to obtain a double-salt electrolyte.

[0070] Example 2

[0071] The electrolyte is prepared according to the following steps:

[0072] (1) lithium bisfluorosulfonylimide (LiFSI) is selected as a main salt, lithium difluoro(oxalato)borate (LiDFOB) is selected as a secondary salt, diethoxymethane (DEM, molecular formula CH3CH2OCH2OCH2CH3) is selected as an ether organic solvent, triethyl phosphate (TEP) is selected as a phosphate organic solvent, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) is selected as a diluent;

[0073] (2) In a glove box with humidity less than 0.01 ppm, molecular sieves were added to DEM and TEP respectively to remove water, and left to stand for 12 hours; LiFSI and LiDFOB were placed in the glove box, and then dried at 100 ℃.

[0074] (3) 16% of DEM, 21% of TEP, 30% of TTE, 30% of LiFSI and 3% of LiDFOB were weighed according to the mass percentage, so that the total concentration of lithium salts (including main salt and auxiliary salt) in the electrolyte was 3 mol / L, and the mixture was fully mixed and dissolved to obtain a double salt electrolyte.

[0075] Comparative Example 1

[0076] The commercial electrolyte was prepared according to the following steps:

[0077] (1) In a glove box with humidity less than 0.01 ppm, vinyl carbonate, dimethyl carbonate and methyl ethyl carbonate were respectively measured according to the volume ratio of 1:1:1 to prepare an organic solvent;

[0078] (2) Lithium salt LiPF6 was added to the organic solvent of step (1) to make the concentration of the lithium salt in the electrolyte 1 mol / L, and the commercial electrolyte was obtained by fully stirring.

[0079] Comparative Example 2

[0080] The commercial electrolyte was prepared according to the following steps:

[0081] (1) In a glove box with humidity less than 0.01 ppm, vinyl carbonate and diethyl carbonate were respectively measured according to the volume ratio of 3:7 to prepare an organic solvent;

[0082] (2) Lithium salt LiPF6 was added to the organic solvent of step (1) to make the concentration of the lithium salt in the electrolyte 1 mol / L, and the commercial electrolyte was obtained by fully stirring.

[0083] Performance test:

[0084] The electrolytes prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 were respectively injected into a 2025 button cell shell with an injection amount of 70 μL, and a positive electrode of a commercial NCM811 electrode sheet and a negative electrode of lithium metal were selected to prepare a full cell for testing. The voltage range was 2.7-4.3 V, the environmental temperature was 60 ℃, and the cycle performance results were seen in Figure 1 ; the results of NCM811 ternary lithium battery charging and discharging of the electrolyte prepared in Example 1 under the conditions of 2.7-4.3 V, 60 ℃ high temperature and 1C charging and discharging were seen in Figure 2The NCM811 ternary lithium battery rate performance of the electrolyte prepared in Example 1 and Comparative Example 1 at 2.7-4.3V, high temperature of 60 DEG C and different rates was tested, and the results are shown in Table 1. Figure 3 The Coulomb efficiency of the Li-Cu battery of the electrolyte prepared in Example 1 and Comparative Example 1 was tested, and the results are shown in Table 2. Figure 4 .

[0085] From Figure 1 , Figure 2 , Figure 3 and Figure 4 , it can be seen that the electrolyte prepared in Example 1 has excellent cycle performance, the ternary lithium battery made therefrom has a discharge specific capacity of more than 200 mAh / g at high temperature (60 DEG C), the Coulomb efficiency is more than 99.5%, and the discharge specific capacity retention rate at 250 cycles reaches 87%; from Figure 3 , it can be seen that the electrolyte prepared in Example 1 also has excellent rate performance, and the capacity at 10C rate is as high as 138 mAh / g.

[0086] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement and improvement within the principles of the present application shall be included in the protection scope of the present application.

Claims

1. A high temperature resistant, flame retardant, double salt lithium battery electrolyte, characterized in that, The electrolyte comprises a lithium salt, an ether organic solvent, a phosphate organic solvent and a diluent, the lithium salt contains a main salt and a secondary salt, wherein the main salt accounts for 70%-95% of the total mass of the lithium salt, the secondary salt accounts for 5%-30% of the total mass of the lithium salt, the main salt is lithium bisfluorosulfonylimide; the secondary salt is lithium difluoro(oxalato)borate; the ether organic solvent is ethylene glycol dimethyl ether; and the phosphate organic solvent is triethyl phosphate.

2. The double salt lithium battery electrolyte of claim 1, wherein, The diluent is selected from any one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, fluorobenzene and 1,2-difluorobenzene.

3. The double salt lithium battery electrolyte of claim 1, wherein, The mass percentage content of the lithium salt is 20-40 wt%, the mass percentage content of the ether organic solvent is 15-30 wt%, the mass percentage content of the phosphate organic solvent is 20-30 wt%, and the mass percentage content of the diluent is 20-40 wt%, based on 100% of the total mass of the lithium salt, the ether organic solvent, the phosphate organic solvent and the diluent.

4. Process for the preparation of a double salt lithium battery electrolyte according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: The ether organic solvent and the phosphate organic solvent are dehydrated; The lithium salt is dried at 80-120°C; The ether organic solvent and the phosphate organic solvent are mixed in a certain proportion, the lithium salt and the diluent are added, and the mixture is uniformly mixed until completely dissolved to obtain the double-salt lithium battery electrolyte.

5. The method of claim 4, wherein the lithium bisalt battery electrolyte is prepared by the steps of: a) dissolving the lithium salt in the solvent; b) adding the second salt to the solution of step a); and c) adding the first salt to the solution of step b). 5 The dehydration method is selected from any one or more of distillation, addition of molecular sieves and addition of a drying substance.

6. The method of claim 5, wherein the lithium bisalt battery electrolyte is prepared by the steps of: a) dissolving the lithium salt in the solvent; b) adding the second salt to the solution of step a); and c) adding the first salt to the solution of step b). 5 The drying substance is selected from any one or more of calcium hydride, activated carbon, anhydrous calcium oxide, lithium hydride, calcium chloride, diphosphorus pentoxide, an alkali metal and an alkaline earth metal.

7. Use of the double salt lithium battery electrolyte according to any one of claims 1 to 3 in a lithium ion battery, characterized in that, The positive electrode material of the lithium ion battery is one of lithium iron phosphate, lithium cobaltate, a ternary material and a lithium-rich manganese-based positive electrode material.

8. Use according to claim 7, characterized in that, The lithium ion battery is a ternary positive electrode-made button lithium battery, the positive electrode of the ternary positive electrode button lithium battery is a ternary positive electrode material, the negative electrode material is a lithium sheet, the positive electrode and the negative electrode are separated by a PP film, and the electrolyte is the double-salt lithium battery electrolyte.

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