Deep eutectic electrolyte based on phenylsulfone and fluorine-substituted derivative thereof, preparation method of deep eutectic electrolyte and lithium battery

Abstract

The invention relates to the field of lithium batteries, in particular to a deep eutectic electrolyte based on phenylsulfone and a fluorine-substituted derivative thereof and a preparation method of the deep eutectic electrolyte, and the electrolyte is suitable for the lithium batteries. The electrolyte is composed of a deep eutectic solvent and an additive, wherein the deep eutectic solvent is formed by mixing a compound of phenylsulfone and a fluorine-substituted derivative thereof with a lithium salt. The electrolyte has the remarkable advantages of incombustibility, high thermal stability, high lithium ion transference number, wide electrochemical window and the like, and the safety can be improved while the cycle performance of the lithium ion battery can be remarkably improved. In addition, the electrolyte is simple and convenient in preparation process, is suitable for large-scale industrial production, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the field of lithium batteries, and in particular to a deep eutectic electrolyte based on phenylmethyl sulfone and its fluorine-substituted derivatives, a preparation method thereof, and a lithium battery. Background Art

[0002] Lithium batteries have been widely used in modern society due to their advantages such as high energy density and high operating voltage.

[0003] The components of commercial electrolytes currently contain a large number of carbonate and ether solvents, but both types of solvents have some significant disadvantages. First, carbonate electrolytes are volatile, flammable and have poor thermal stability, which makes them prone to fire or explosion when the battery undergoes thermal runaway, posing a major safety hazard. In addition, carbonate electrolytes have poor compatibility with lithium metal, which may cause lithium ions to form lithium dendrites during the deposition process. These dendrites may pierce the battery separator, causing the battery to short-circuit, seriously affecting the safety and reliability of the battery. Although ether electrolytes have good compatibility with lithium metal and can effectively inhibit the formation of lithium dendrites, their electrochemical window is narrow, usually less than 4V, which makes them unsuitable for use in high-voltage lithium-ion battery systems and limits their application in high-energy-density battery systems.

[0004] It is precisely because traditional carbonate and ether electrolytes have low flash points and are volatile that they are prone to combustion and even explosion. In order to solve this problem, the current practice is to add flame retardants to conventional electrolytes. However, flame retardants are usually added in high amounts and have limited flame retardant effects, and usually sacrifice the electrochemical performance of the battery. At the same time, this practice also increases the manufacturing cost of the battery. Therefore, the development of new electrolytes that are non-flammable, have excellent electrochemical properties, higher safety, wider electrochemical windows, and are more compatible with lithium metal has become the focus of current research to adapt to the next generation of high-safety and high-energy-density lithium batteries. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a deep eutectic electrolyte based on phenylmethyl sulfone and its fluorine-substituted derivatives, aiming to balance the problem between the non-flammability and electrochemical performance of the existing electrolyte.

[0006] The technical solution of the present invention is as follows: a deep eutectic electrolyte based on phenylmethyl sulfone and its fluorine-substituted derivatives is provided, which includes: a low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives and an additive, wherein the low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives is obtained by mixing phenylmethyl sulfone and its fluorine-substituted derivative compounds with lithium salts and then stirring.

[0007] Optionally, the molar ratio of the anisole sulfone and its fluorine-substituted derivative compound to the lithium salt is 1:10-5:1, and the mass of the additive accounts for 0.01%-20% of the mass of the electrolyte.

[0008] Optionally, the sulfone compound is selected from one or more of phenyl methyl sulfone, phenyl trifluoromethyl sulfone, bis(4-fluorophenyl) sulfone, 4-fluorophenyl methyl sulfone, 2-fluorophenyl methyl sulfone, fluoromethyl phenyl sulfone, 3,4-difluorophenyl methyl sulfone, difluoromethyl phenyl sulfone, 2-fluoro-4-methylsulfonylaniline or 4-fluoro-3-nitrophenyl methyl sulfone.

[0009] Optionally, the lithium salt is selected from one or more of common lithium salts such as lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium nitrate.

[0010] Optionally, the additive is selected from one or more of organic ester compounds, fluoride additives, nitrates and organic lithium salts.

[0011] Optionally, the organic ester is selected from one or more of organic carbonate compounds, organic sulfate esters, and organic sulfonate esters.

[0012] Another technical solution provided by the present invention is as follows: a method for preparing a deep eutectic electrolyte based on phenylmethyl sulfone and its fluorine-substituted derivatives, which comprises the steps of: In an inert atmosphere, the compound of phenylmethyl sulfone and its fluorine-substituted derivatives is mixed with a lithium salt and fully stirred at a set temperature to obtain a low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives; then an additive is added and stirring is continued to finally obtain the electrolyte.

[0013] Optionally, a certain proportion of phenylmethyl sulfone and its fluorine-substituted derivative compounds are mixed with lithium salt and stirred, and after cooling, a low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives is obtained; then an additive is added to the low eutectic solvent and then stirred; the specific steps are: adjusting the proportion of phenylmethyl sulfone and its fluorine-substituted derivative compounds and lithium salt to mix, and stirring evenly at a temperature of 30-100°C to obtain a low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives; then adding an additive to the low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives and then stirring evenly.

[0014] Another technical solution provided by the present invention is as follows: a lithium battery is provided, comprising the deep eutectic electrolyte based on phenylmethyl sulfone and its fluorine-substituted derivatives described in the present invention.

[0015] Optionally, the lithium battery also includes: a positive electrode, a negative electrode and a separator; wherein the material of the positive electrode is one or more of lithium iron phosphate, lithium manganese oxide, lithium iron manganese phosphate, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium cobalt oxide, lithium nickel manganese oxide and sulfide materials; the negative electrode is one or more of a metal lithium negative electrode, a graphite negative electrode, a silicon-carbon negative electrode, a silicon negative electrode, a silicon-oxygen negative electrode and an organic negative electrode; the separator is one or more of a polyethylene separator, a polypropylene separator, a PP / PE composite separator, a glass fiber separator and separators modified from the above separators.

[0016] The beneficial effects of the present invention are as follows: the electrolyte prepared by the present invention has the advantages of being non-flammable, non-volatile, having high thermal stability and a wide electrochemical window, and can have excellent electrochemical properties while ensuring high battery safety, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the linear sweep voltammogram of the electrolyte prepared in Example 1 of the present invention.

[0018] Figure 2 Thermogravimetric diagrams of the electrolyte prepared in Example 1 of the present invention and the traditional commercial electrolyte in Comparative Example 1.

[0019] Figure 3 This is a long cycle performance diagram of the electrolyte prepared in Example 1 of the present invention and the traditional commercial electrolyte in Comparative Example 1. DETAILED DESCRIPTION

[0020] The present invention provides a deep eutectic electrolyte based on benzylsulfone and its fluorine-substituted derivatives, a preparation method thereof, and a lithium battery. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] Deep eutectic electrolytes have many advantages, such as non-flammability, high stability and non-volatility. Among them, non-flammability can effectively solve the safety issues of current commercial carbonate electrolytes. In addition, the low cost and easy manufacturing characteristics of deep eutectic electrolytes are also ideal choices for battery electrolytes.

[0022] Based on this, an embodiment of the present invention provides a deep eutectic electrolyte based on phenylmethyl sulfone and its fluorine-substituted derivatives, which includes: a low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives and an additive, wherein the low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives is obtained by blending phenylmethyl sulfone and its fluorine-substituted derivative compounds and lithium salts.

[0023] This embodiment introduces an electrolyte based on a low eutectic solvent (DES) of anisolesulfone and its fluorinated derivatives. The electrolyte forms DES by eutectic melting of anisolesulfone and its fluorinated derivatives with lithium salts in different molar ratios, and a certain amount of additives are added as required to prepare a deep eutectic electrolyte. This electrolyte has many advantages, including non-flammability, high thermal stability, and a wide electrochemical window. It can not only meet the non-flammability required for the electrolyte, but also exhibit excellent electrochemical properties at the same time. In addition, since the preparation method is simple and meets the needs of large-scale industrial production, the deep eutectic electrolyte has good application prospects.

[0024] A low eutectic solvent is a eutectic mixture formed by mixing two or more substances in a specific proportion. Due to the interaction between the components (such as hydrogen bonds, Lewis acid-base effects, and van der Waals forces, etc.), the melting point of the mixture is significantly lower than the melting point of each individual component. In the low eutectic solvent of anisole sulfone and its fluorinated derivatives provided in this embodiment, there is a strong coordination effect between the lithium ions in the lithium salt and the -S=O group in the anisole sulfone and its fluorinated derivative compounds. This effect can effectively reduce the interaction between the lithium ions and anions (such as TFSI⁻, BOB⁻, etc.) in the lithium salt and the interaction between the molecules of the sulfone compound, thereby reducing the melting point of the mixture as a whole, and finally forming anisole sulfone and its fluorinated derivatives low eutectic solvent, and the introduction of the -F group makes the low eutectic solvent contribute to the formation of the solid electrolyte interface layer (SEI) of the lithium ion battery electrode to a certain extent, effectively protecting the electrode from erosion by side reactions.

[0025] After research, it was found that by fully mixing phenyl sulfone and its fluorine-substituted derivative compounds with lithium salts in a certain stoichiometric ratio, a low eutectic solvent can be formed by utilizing the interaction between them. The electrolyte made of this low eutectic solvent has high thermal stability and excellent oxidation resistance (greater than 5V), and has the advantages of being non-flammable and having excellent electrochemical properties. It is suitable for various positive electrode materials (ternary materials, lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide and lithium manganese oxide, etc.) and various negative electrodes (graphite, lithium metal, silicon, silicon carbon and silicon oxygen negative electrodes), and can contribute excellent electrochemical performance.

[0026] In this embodiment, the deep eutectic electrolyte based on anisole and its fluorine-substituted derivatives can induce more anions to participate in the SEI film formation process, thereby generating a more stable SEI film rich in inorganic substances (such as LiF, Li3N, BO / F, etc.), ensuring the stability of the battery in long-term operation.

[0027] In one embodiment, the molar ratio of the anisole sulfone and its fluorine-substituted derivative compound to the lithium salt is 1:10-5:1, and the mass of the additive accounts for 0.01%-20% of the mass of the electrolyte. Within a certain ratio range, the deep eutectic solvent formed by the anisole sulfone and its fluorine-substituted derivative compound and the lithium salt is more stable, and the content of the additive within a certain ratio range can form a more stable SEI.

[0028] In one embodiment, the phenylmethyl sulfone and its fluorine-substituted derivative compounds are selected from one or more of phenylmethyl sulfone, phenyltrifluoromethyl sulfone, bis(4-fluorophenyl) sulfone, 4-fluorophenyl methyl sulfone, 2-fluorophenyl methyl sulfone, fluoromethyl phenyl sulfone, 3,4-difluorophenyl methyl sulfone, difluoromethyl phenyl sulfone, 2-fluoro-4-methylsulfonylaniline or 4-fluoro-3-nitrophenyl methyl sulfone.

[0029] In one embodiment, the lithium salt is selected from one or more of common lithium salts such as lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium nitrate.

[0030] In one embodiment, the additive is selected from one or more of an organic ester compound, a fluoride additive, a nitrate and an organic lithium salt, wherein the organic ester compound is selected from one or more of an organic carbonate, an organic sulfate and an organic sulfonate. The use of these film-forming additives can form a stable SEI interface film, including the generation of LiF, Li3N, and BO / F compounds.

[0031] In one embodiment, the organic esters are one or more of cyclic esters, chain esters and organic substitution products thereof.

[0032] Compared with the existing ones, the deep eutectic electrolyte of phenylmethyl sulfone and its fluorine-substituted derivatives described in this embodiment has the following advantages and outstanding effects: ① Different from traditional commercial electrolytes, this deep eutectic electrolyte is non-flammable, highly thermally stable and highly safe; ② Different from traditional commercial electrolytes, the electrochemical window of this deep eutectic electrolyte is as high as 5V and above; it is suitable for various high-voltage cathode materials; ③ The deep eutectic electrolyte can form stable interfacial SEI film and CEI film on the surface of anode and cathode materials, ensuring the stability of the battery during long cycle charge and discharge and improving the cycle life of the battery; ④ The electrolyte synthesis method is simple and convenient, and is suitable for large-scale application; ⑤ The electrolyte has extremely low volatility, is not easy to inhale, and causes little harm to the human body.

[0033] The embodiment of the present invention provides a method for preparing the deep eutectic electrolyte of the above-mentioned phenylmethyl sulfone and its fluorine-substituted derivatives, which comprises the steps of: In an inert atmosphere, the compound of phenylmethyl sulfone and its fluorine-substituted derivatives is mixed with a lithium salt and fully stirred at a set temperature to obtain a low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives; then an additive is added and stirring is continued to finally obtain the electrolyte.

[0034] In one embodiment, the step of mixing a certain proportion of phenylmethyl sulfone and its fluorine-substituted derivative compound with a lithium salt and stirring, cooling to obtain a low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivative; then adding an additive to the low eutectic solvent and then stirring, specifically comprises: adjusting the proportion of phenylmethyl sulfone and its fluorine-substituted derivative compound and lithium salt to mix, and stirring evenly at 30-100° C. to obtain a low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivative; then adding an additive to the low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivative and stirring evenly.

[0035] In one embodiment, the inert atmosphere environment can be an argon atmosphere environment, a nitrogen atmosphere environment or a helium atmosphere environment. Further, in the inert atmosphere environment, the water content and the oxygen content are both below 1 ppm.

[0036] An embodiment of the present invention provides a lithium battery, which includes the deep eutectic electrolyte based on anisyl sulfone and its fluorine-substituted derivatives as described above.

[0037] The electrolyte described in this embodiment is suitable for lithium batteries. Specifically, the lithium battery includes: an electrolyte, a positive electrode, a negative electrode and a diaphragm, wherein the electrolyte is the electrolyte described in this embodiment, the material of the positive electrode is one or more of lithium iron phosphate, lithium manganese oxide, lithium iron manganese phosphate, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium cobalt oxide, lithium nickel manganese oxide and sulfide materials; the negative electrode is one or more of a metal lithium negative electrode, a graphite negative electrode, a silicon carbon negative electrode, a silicon negative electrode, a silicon oxygen negative electrode and an organic negative electrode; the diaphragm is one or more of a polyethylene diaphragm, a polypropylene diaphragm, a PP / PE composite diaphragm, a glass fiber diaphragm and a diaphragm modified from the above diaphragms.

[0038] The present invention will be further described below through several specific embodiments.

[0039] Comparative Example 1 The carbonate solvent electrolyte of this comparative example is composed of LiPF6, ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC), wherein the concentration of LiPF6 in the electrolyte is 1M, and the volume ratio of EC, DMC and EMC is 1:1:1. The electrolyte system is used for battery testing with metallic lithium as the negative electrode and lithium iron phosphate as the positive electrode. After testing, it is found that the coulomb efficiency of the battery reaches 98.0% and the cycle life is 500 cycles.

[0040] Comparative Example 2 The carbonate solvent electrolyte of this comparative example is composed of LiPF6, ethylene carbonate (EC) and diethyl carbonate (DEC), wherein the concentration of LiPF6 in the electrolyte is 1M, and the volume ratio of EC to DEC is 1:1. The electrolyte system is used for battery testing with graphite as the negative electrode and nickel-cobalt-manganese 811 as the positive electrode. After testing, it is found that the coulomb efficiency of the battery reaches 99.0% and the cycle life is 400 cycles.

[0041] Example 1 Lithium bis(trifluoromethanesulfonyl)imide and 2-fluorophenylmethyl sulfone were mixed in a molar ratio of 1:5, stirred at 60°C until clear and transparent, and then fluoroethylene carbonate accounting for 5% of the electrolyte mass was added after cooling to prepare a eutectic electrolyte based on a sulfone-based low eutectic solvent. The electrolyte system was used to test a battery with metallic lithium as the negative electrode and lithium iron phosphate as the positive electrode. After testing, it was found that the coulomb efficiency of the battery reached more than 99.9%, and the cycle life could reach 3000 cycles.

[0042] Figure 1 This is the linear sweep voltammogram of the electrolyte prepared in Example 1 of the present invention. It can be seen from the figure that the anti-oxidation potential of the electrolyte reaches above 5V, which is suitable for all high-voltage cathode materials.

[0043] Figure 2 The thermogravimetric diagrams of the electrolyte prepared in Example 1 of the present invention and the traditional electrolyte in Comparative Example 1 show that the weight loss rate of the electrolyte in Example 1 is less than 10% at 100°C, while the weight loss rate of the traditional carbonate electrolyte is about 50%.

[0044] Figure 3 This is a long cycle performance diagram of the electrolyte prepared in Example 1 of the present invention. It can be seen from the figure that at a rate of 1C, after 2950 cycles, the discharge capacity is 142.3 mAh / g, and the capacity retention rate is 98.3%.

[0045] Example 2 Lithium bis(trifluoromethanesulfonyl)imide and anisole sulfone were mixed in a molar ratio of 1:3, stirred at 60°C until clear and transparent, and then fluoroethylene carbonate accounting for 5% of the electrolyte mass was added after cooling to prepare a sulfone-based low eutectic solvent-based eutectic electrolyte. This electrolyte system was used for battery testing with lithium metal as the negative electrode and lithium iron phosphate as the positive electrode. After testing, it was found that the coulomb efficiency of the battery reached more than 99% and the cycle life could reach 800 cycles.

[0046] Example 3 Lithium bis(trifluoromethanesulfonyl)imide and phenyl(trifluoromethylsulfone) were mixed in a molar ratio of 1:3.5, stirred at 60°C until clear and transparent, and then 2% of the electrolyte mass was added to the fluoroethylene carbonate after cooling, and then stirred evenly to prepare a gel eutectic electrolyte based on a sulfone-based low eutectic solvent. The electrolyte system was used for full battery testing with lithium metal as the negative electrode and lithium iron phosphate as the positive electrode. After testing, it was found that the coulomb efficiency of the battery reached more than 99%, and the cycle life could reach 1000 cycles.

[0047] Example 4 Lithium bis(fluorosulfonyl)imide and anisole sulfone were mixed in a molar ratio of 2:5, stirred at 60°C until clear and transparent, and then fluoroethylene carbonate accounting for 2% of the electrolyte mass was added after cooling, and then stirred evenly to prepare a gel eutectic electrolyte based on a sulfone-based low eutectic solvent. This electrolyte system was used for full battery testing with lithium metal as the negative electrode and lithium iron phosphate as the positive electrode. After testing, it was found that the coulomb efficiency of the battery reached more than 99%, and the cycle life could reach 750 cycles.

[0048] Example 5 Lithium bis(fluorosulfonyl)imide and 2-fluoromethylphenylsulfone were mixed in a molar ratio of 1:4 and stirred at 60°C until clear and transparent to prepare a gel-state eutectic electrolyte based on a sulfone-based low eutectic solvent. The electrolyte system was used for full battery testing with lithium metal as the negative electrode and lithium iron phosphate as the positive electrode. The test found that the coulombic efficiency of the battery reached more than 99% and the cycle life could reach 1500 cycles.

[0049] Example 6 Lithium bis(trifluoromethanesulfonyl)imide, lithium difluoroborate and 2-fluorophenylmethyl sulfone were mixed in a molar ratio of 2:1:9 and stirred evenly at 60°C to prepare a gel eutectic electrolyte based on a sulfone-based low eutectic solvent. The electrolyte system was used for full battery testing with lithium metal as the negative electrode and lithium iron phosphate as the positive electrode. The test found that the coulomb efficiency of the battery reached more than 99% and the cycle life could reach 1700 cycles.

[0050] Table 1 Cycle performance test results of lithium ion batteries prepared in Examples 1-6 and Comparative Examples 1-2 As can be seen from Table 1, the electrolyte prepared by the present invention has a wide electrochemical window, indicating that this type of electrolyte can exist stably within a higher voltage range, which enables it to be applied to all known cathode materials; when applied to Li-LFP batteries, the batteries still have a high capacity retention rate after thousands of cycles, that is, they can provide the batteries with a longer service life and thus have great commercial potential.

[0051] In summary, the present invention provides a deep eutectic electrolyte based on anisole and its fluorine-substituted derivatives, a preparation method thereof, and a lithium battery, specifically, anisole and its fluorine-substituted derivative compounds are mixed with lithium salts in different molar ratios, and a certain proportion of additives are added to form a deep eutectic electrolyte. The electrolyte has the advantages of being non-flammable, non-volatile, having high thermal stability and a wide electrochemical window. It is applied to lithium batteries and can effectively improve the cycle performance and safety of the battery. Moreover, since the preparation method is simple and meets the needs of large-scale industrial production, the deep eutectic electrolyte has good application prospects.

[0052] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A deep eutectic electrolyte based on phenylmethyl sulfone and its fluorinated derivatives, characterized in that: include: A low eutectic solvent and an additive, wherein the low eutectic solvent is obtained by mixing a compound of phenylmethyl sulfone and a fluorine-substituted derivative thereof with a lithium salt.

2. The deep eutectic electrolyte based on anisyl sulfone and its fluorinated derivatives according to claim 1, characterized in that: The molar ratio of the compound of the anisole sulfone and its fluorine-substituted derivative to the lithium salt is 10:1-1:5, and the mass of the additive accounts for 0.01%-20% of the mass of the deep eutectic electrolyte.

3. The deep eutectic electrolyte based on anisyl sulfone and its fluorinated derivatives according to claim 1, characterized in that: The sulfone compound is selected from one or more of phenyl methyl sulfone, phenyl trifluoromethyl sulfone, bis(4-fluorophenyl) sulfone, 4-fluorophenyl methyl sulfone, 2-fluorophenyl methyl sulfone, fluoromethyl phenyl sulfone, 3,4-difluorophenyl methyl sulfone, difluoromethyl phenyl sulfone, 2-fluoro-4-methylsulfonyl aniline or 4-fluoro-3-nitrophenyl methyl sulfone.

4. The deep eutectic electrolyte based on anisyl sulfone and its fluorinated derivatives according to claim 1, characterized in that: The lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium nitrate.

5. The deep eutectic electrolyte based on anisyl sulfone and its fluorine-substituted derivatives according to claim 1, characterized in that: The additive is selected from one or more of organic ester compounds, fluoride additives, nitrates and organic lithium salts.

6. The deep eutectic electrolyte based on anisyl sulfone and its fluorinated derivatives according to claim 5, characterized in that: The organic ester compound is selected from one or more of organic carbonates, organic sulfates, and organic sulfonates.

7. A method for preparing a deep eutectic electrolyte based on anisyl sulfone and its fluorine-substituted derivatives as claimed in any one of claims 1 to 6, characterized in that: Includes steps: Under an inert atmosphere, a compound of phenylmethyl sulfone and its fluorine-substituted derivatives is mixed with a lithium salt and stirred evenly at 30-100° C. After cooling, a low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives is obtained; then, an additive is added to the low eutectic solvent of phenylmethyl sulfone and its fluorine-substituted derivatives and stirred evenly to finally obtain the electrolyte.

8. A lithium battery, characterized in that: It comprises the deep eutectic electrolyte based on phenylmethyl sulfone and its fluorine-substituted derivatives as claimed in claim 7.

9. The lithium-ion battery according to claim 8, characterized in that: The lithium battery also includes: a positive electrode, a negative electrode and a separator; Wherein, the material of the positive electrode is one or more of lithium iron phosphate, lithium manganese oxide, lithium iron manganese phosphate, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium cobalt oxide, lithium nickel manganese oxide and sulfide material; The negative electrode is one or more of a metal lithium negative electrode, a graphite negative electrode, a silicon-carbon negative electrode, a silicon negative electrode, a silicon-oxygen negative electrode and an organic negative electrode; The diaphragm is one or more of a polyethylene diaphragm, a polypropylene diaphragm, a PP / PE composite diaphragm, a glass fiber diaphragm and diaphragms modified from the above diaphragms.

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