An ionic liquid-based electrolyte and its application
By combining ionic liquid-based electrolytes with diluents and additives, a dense SEI film is formed, which solves the problems of lithium dendrite growth and safety hazards in lithium metal batteries, and achieves high safety and high energy density lithium-ion battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG LANDE ENERGY TECHNOLOGY DEVELOPMENT CO LTD
- Filing Date
- 2026-05-13
- Publication Date
- 2026-07-31
AI Technical Summary
In existing lithium metal batteries, traditional carbonate electrolytes decompose at high reduction potentials, forming an unstable SEI film, which leads to lithium dendrite growth and safety hazards. Ionic liquid electrolytes have high viscosity, resulting in performance degradation. Glass fiber separators have poor mechanical strength and high cost, making it impossible to balance high safety and battery energy density.
An ionic liquid-based electrolyte is used, which contains ionic liquid, lithium salt, diluent and additives to form a locally high concentration solvation structure. The diluent reduces the viscosity and forms a dense SEI membrane. A polyolefin separator is used to avoid the defects of glass fiber separators.
It achieves high safety, wide electrochemical window and high ionic conductivity, suppresses lithium dendrite growth, improves coulombic efficiency and cycle stability, and is suitable for electric vehicles and energy storage fields with strict safety requirements.
Smart Images
Figure CN122494742A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrolyte technology, and in particular to an ionic liquid-based electrolyte and its application. Background Technology
[0002] Lithium metal, with its extremely high theoretical specific capacity (3860 mAh / g) and the most negative electrochemical potential (-3.04 V vs. standard hydrogen electrode), is considered the "ultimate anode" material for realizing next-generation high-energy-density batteries. Using lithium metal anodes can significantly improve battery energy density; for example, when matched with high-capacity cathodes (such as sulfur and oxygen), the theoretical energy density can reach over 500 Wh / kg, far exceeding current commercial lithium-ion batteries (<300 Wh / kg). However, the commercial application of lithium metal anodes faces severe challenges, such as lithium dendrite growth, interface instability, significant volume changes, and safety issues with traditional carbonate electrolytes. Traditional carbonate electrolytes continuously decompose under the high reduction potential of lithium metal, forming an unstable, porous SEI film. This not only consumes active lithium and electrolyte but also easily induces the concentrated growth of lithium dendrites due to the uneven decomposition products, severely restricting its practical application.
[0003] To address the safety concerns of carbonate electrolytes, researchers have explored using ionic liquids as the electrolyte matrix. Ionic liquids possess excellent thermal stability, non-flammability, and a wide electrochemical window, potentially mitigating the thermal runaway risk of lithium metal batteries. However, ionic liquids face the challenge of high viscosity, leading to significant performance degradation when using traditional, thin, low-cost commercial separators. Consequently, most batteries employing ionic liquid electrolytes in current technologies are forced to use glass fiber (GF) separators as alternatives, resulting in substantial performance compromises. Glass fiber has significant drawbacks: ① Poor mechanical strength: Composed of glass microfiber nonwoven fabric, its loose structure results in extremely low puncture resistance (<10N), weak physical resistance to lithium dendrite growth, and significant safety hazards; ② Excessive thickness: To achieve basic mechanical strength, the separator thickness exceeds 500μm, severely encroaching on the battery's internal volume and drastically reducing the battery's volumetric and gravimetric energy densities; ③ High electrolyte retention but poor electrolyte balance: Easily wetted by high-viscosity liquids, but easily "saturated" after absorbing liquid, and the electrolyte distribution during cycling is prone to unevenness; ④ High cost: Price is 5-10 times that of commercial separators (PP separators, PE separators); ⑤ No thermal shut-off function: It does not possess the melt-closing characteristics of commercial separators, and cannot provide additional passive safety protection in the early stages of thermal runaway. In contrast, commercial separators (especially polyolefin separators such as PE and PP) have unique advantages: ① Extremely thin, 10~25μm, which can improve the energy density of the battery to a certain extent; ② High mechanical strength, excellent tensile and puncture resistance (puncture strength >300N / mm), which can improve the safety performance of the battery; ③ Good thermal safety, with a "thermal shut-off" function (PE separator melts and closes pores at about 135℃), which can block the current; ④ Good wettability with electrolyte and low interfacial impedance; ⑤ Extremely low cost, high maturity, and perfect compatibility with existing large-scale winding / stacking processes.
[0004] Therefore, developing an ionic liquid-based high-safety electrolyte for lithium metal batteries that can maintain high safety, be well compatible with commercial separators, and have excellent electrochemical performance has become a technical challenge that urgently needs to be solved in this field. Summary of the Invention
[0005] The purpose of this invention is to provide an ionic liquid-based electrolyte and its application, addressing the shortcomings of existing technologies.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an ionic liquid-based electrolyte, which comprises an ionic liquid, a lithium salt, a diluent, and an additive; The mass ratio of the diluent to the ionic liquid is 1~2:1; In the ionic liquid-based electrolyte, the mass fraction of lithium salt is 5-15%, and the mass fraction of additives is 15-25%.
[0007] Preferably, the ionic liquid comprises one or more of pyrrole borates, pyrrole sulfonyl imides, piperidine sulfonyl imides, imidazole sulfonyl imides, and quaternary ammonium sulfonyl imides.
[0008] Preferably, the pyrrole borate is N,N-dimethylpyrrole tetrafluoroborate; The pyrrole sulfonyl imide salt comprises one or more of N-propyl-N-methylpyrrole bis(trifluoromethanesulfonyl imide), 1-ethyl-1-methylpyrrole bis(trifluoromethanesulfonyl imide), N-butyl-N-methylpyrrole bis(trifluoromethanesulfonyl imide), and N-butyl-N-methylpyrrole bis(fluorosulfonyl imide). The piperidine sulfonyl imide salt is 1-propyl-1-methylpiperidine bis(trifluoromethylsulfonyl imide salt); The imidazole sulfonyl imide salt comprises one or more of 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl imide), 1,2-bis(2-(N-methylimidazol)ethoxy)ethane bis(fluorosulfonyl imide) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide). The quaternary ammonium sulfonyl imide salt is N-methoxyethyl-N-methyldiethylammonium bis(trifluoromethanesulfonyl)imide salt.
[0009] Preferably, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonylimide, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium difluorobis(oxalato)phosphate, and lithium difluorophosphate.
[0010] Preferably, the additive comprises one or more of vinylene carbonate, trimethyl phosphate, fluoroethylene carbonate, 1,3-propane sulphol, tris(trimethylsilyl)borate, lithium difluorooxalate borate, lithium nitrate, and succinate.
[0011] Preferably, the diluent comprises one or more of hydrofluoroether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.
[0012] The present invention also provides the application of the ionic liquid-based electrolyte in a lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode, a separator and the ionic liquid-based electrolyte, wherein the separator is a polyolefin separator.
[0013] Preferably, the negative electrode is lithium metal.
[0014] The beneficial effects of this invention are: 1) In the ionic liquid-based electrolyte of this invention, both the ionic liquid and the diluent are non-flammable, fundamentally eliminating the risk of electrolyte combustion; the lithium salt is mainly dissolved in the ionic liquid and additives to form Li + The locally high-concentration solvation structure, tightly surrounded by a large number of ionic liquid anions and additive molecules, promotes the preferential reduction of anions on the lithium metal surface during charging and discharging, forming a dense, stable, and LiF-rich solid electrolyte interphase (SEI) film. This greatly inhibits the growth of lithium dendrites and improves coulombic efficiency and cycle stability. By using a diluent to locally dilute the high-viscosity ionic liquid at a high concentration, the viscosity of the electrolyte is significantly reduced, allowing for full wetting of commercial membranes. This avoids the drawback of using glass fiber membranes for high-viscosity ionic liquid electrolytes, while also giving the electrolyte higher ionic conductivity and faster ion transport.
[0015] 2) The battery system composed of the ionic liquid-based electrolyte of the present invention maintains high safety while having high ionic conductivity (>5mS / cm) and a wide electrochemical window (≥5.0V), as well as excellent cycle performance and rate performance, making it particularly suitable for electric vehicles and energy storage fields with strict safety requirements. Attached Figure Description
[0016] Figure 1 A comparison chart of the flammability of electrolytes; Figure 2 A comparison diagram of the wettability of electrolytes; Figure 3 This is a linear sweep voltammetry plot of the electrolyte. Figure 4 The charge-discharge curves of the lithium-ion battery assembled using the ionic liquid-based electrolyte of Example 2 are shown. Figure 5 The graph shows the cycle performance of a lithium-ion battery assembled using the ionic liquid-based electrolyte of Example 2. Figure 6 The coulombic efficiency diagram shows the lithium-ion battery assembled using the ionic liquid-based electrolyte of Example 2. Figure 7 The graph shows the rate performance of a lithium-ion battery assembled using the ionic liquid-based electrolyte of Example 2. Detailed Implementation
[0017] This invention provides an ionic liquid-based electrolyte, which comprises an ionic liquid, a lithium salt, a diluent, and an additive; The mass ratio of the diluent to the ionic liquid is 1~2:1; In the ionic liquid-based electrolyte, the mass fraction of lithium salt is 5-15%, and the mass fraction of additives is 15-25%.
[0018] In this invention, the mass ratio of the diluent to the ionic liquid is preferably 1.2 to 1.8:1, more preferably 1.4 to 1.6:1, and even more preferably 1.5:1; In the ionic liquid-based electrolyte, the mass fraction of lithium salt is preferably 8-12%, more preferably 9%; the mass fraction of additive is preferably 16-22%, more preferably 18-20%, and even more preferably 18.2-19%.
[0019] In this invention, the ionic liquid preferably comprises one or more of pyrrole borates, pyrrole sulfonamide salts, piperidine sulfonamide salts, imidazole sulfonamide salts, and quaternary ammonium sulfonamide salts.
[0020] In this invention, the pyrrole borate is preferably N,N-dimethylpyrrole tetrafluoroborate; The pyrrole sulfonyl imide salt preferably comprises one or more of N-propyl-N-methylpyrrole bis(trifluoromethanesulfonyl imide), 1-ethyl-1-methylpyrrole bis(trifluoromethanesulfonyl imide), N-butyl-N-methylpyrrole bis(trifluoromethanesulfonyl imide), and N-butyl-N-methylpyrrole bis(fluorosulfonyl imide). The piperidine sulfonyl imide salt is preferably 1-propyl-1-methylpiperidine bis(trifluoromethylsulfonyl imide) salt; The imidazole sulfonyl imide salt preferably comprises one or more of 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl imide), 1,2-bis(2-(N-methylimidazol)ethoxy)ethane bis(fluorosulfonyl imide) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide). The preferred quaternary ammonium sulfonyl imide salt is N-methoxyethyl-N-methyldiethylammonium bis(trifluoromethanesulfonyl)imide salt.
[0021] In this invention, the lithium salt preferably comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonylimide, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium difluorobis(oxalato)phosphate, and lithium difluorophosphate.
[0022] In this invention, the additive preferably comprises one or more of the following: vinylene carbonate, trimethyl phosphate, fluoroethylene carbonate, 1,3-propanesulfonyl lactone, tris(trimethylsilyl)borate, lithium difluorooxalate borate, lithium nitrate, and succinate.
[0023] In this invention, the diluent preferably comprises one or more of hydrofluoroether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.
[0024] The present invention also provides the application of the ionic liquid-based electrolyte in a lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode, a separator and the ionic liquid-based electrolyte, wherein the separator is a polyolefin separator.
[0025] In this invention, the negative electrode is preferably lithium metal.
[0026] In this invention, the active material of the positive electrode preferably includes lithium iron phosphate, lithium nickel cobalt manganese oxide, or lithium cobalt oxide.
[0027] In this invention, the polyolefin separator preferably comprises a PP separator or a PE separator.
[0028] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0029] Example 1
[0030] The ionic liquid-based electrolyte is composed of an ionic liquid, a lithium salt, a diluent, and additives. The ionic liquid is N-propyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide, the diluent is hydrofluoroether HFE-458, and the additives are fluoroethylene carbonate and succinate. The mass ratio of the ionic liquid, succinate, fluoroethylene carbonate, hydrofluoroether HFE-458, and lithium salt is 6:3:1:10:2.
[0031] The preparation method of the ionic liquid N-propyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt is as follows: 364 g of 1-methylpyrrolidine (4.28 mol) was added to a three-necked flask, and 896 g of deionized water was added dropwise under nitrogen protection, maintaining the temperature below 31 °C during the addition. After the addition was complete, 4.48 g of lithium hydroxide was added until completely dissolved to obtain a mixture. 578.4 g of bromopropane was added to the mixture through a constant pressure dropping funnel, and the addition was completed in 40 min. Then the temperature was raised to 70 °C and reacted at 70 °C for 5 h. After the reaction was completed, 5% activated carbon (by mass of the solution) was added, and the mixture was decolorized at 60 °C for 18 h. After cooling to room temperature, the mixture was filtered to obtain an N-propyl-N-methylpyrrolidine bromide salt solution. 1228.7 g of bis(trifluoromethanesulfonyl)imide lithium salt and 900 g of dichloromethane were added to the obtained N-propyl-N-methylpyrrolidine bromide salt solution, and the mixture was reacted at room temperature for 6 h. After standing and separating into layers, the lower layer is washed with water until no precipitate is found in the washing solution when tested with 5% silver nitrate. Dichloromethane is removed by rotary evaporation, and water is removed by an oil pump at 65°C to obtain the ionic liquid N-propyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt.
[0032] The preparation method of the ionic liquid-based electrolyte is as follows: In an argon glove box at 40℃ (H2O<0.1ppm, O2<0.1ppm), the ionic liquid, diluent, and additives are mixed and magnetically stirred for 2 hours until homogeneous and transparent. Then, lithium salt is added, and stirring is continued for 12 hours until completely dissolved, thus obtaining a clear and transparent ionic liquid-based electrolyte.
[0033] The ionic liquid-based electrolyte in this embodiment has a viscosity of 68.4 Pa·s at 25°C and an electrochemical window of 5.2 V.
[0034] Example 2
[0035] The difference from Example 1 is that the diluent is bis(2,2,2-trifluoroethyl) ether, otherwise it is the same as Example 1.
[0036] The ionic liquid-based electrolyte in this embodiment has a viscosity of 44.5 Pa·s at 25°C and an electrochemical window of 5.2 V.
[0037] Example 3
[0038] The difference from Example 2 is that the ionic liquid is 1-ethyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt. The preparation method of the ionic liquid 1-ethyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt is as follows: 102.8 g of 1-methylpyrrolidine (1.2 mol) and 1.5 g of lithium hydroxide are added to a two-necked flask, followed by 200 g of pure water. Then, 156.1 g of bromoethane (1.45 mol) is added dropwise at a rate of 30 mL / h. After the addition is complete, the temperature is raised to 60 °C and reacted at 60 °C for 18 h. After the reaction is complete, 18 g of activated carbon is added, and the temperature is raised to 65 °C for decolorization for 7 h. After cooling to room temperature, the mixture is filtered to obtain an N-ethyl-N-methylpyrrolidine bromide solution. 344.51 g of bis(trifluoromethanesulfonyl)imide lithium salt (1.2 mol) is added to the obtained N-ethyl-N-methylpyrrolidine bromide solution, followed by 400 g of dichloromethane. The mixture is reacted at room temperature for 6 h. After the reaction was completed, the mixture was allowed to stand and separate into layers. The upper aqueous layer was washed with dichloromethane and the dichloromethane phases were combined. Then, the mixture was washed with pure water and concentrated by rotary evaporation to remove the solvent. Finally, it was dried under vacuum at 70°C for 4 hours to obtain the ionic liquid 1-ethyl-1-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt.
[0039] The ionic liquid-based electrolyte in this embodiment has a viscosity of 70.1 Pa·s at 25°C and an electrochemical window of 5.1 V.
[0040] Example 4
[0041] The difference from Example 2 is that the ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. The preparation method of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is as follows: 1-ethyl-3-methylimidazolium chloride is dissolved in twice the amount of deionized water, then 5% of the total mass of activated carbon is added, and the mixture is decolorized at 65°C for 4 hours. The solution is then filtered to obtain a 1-ethyl-3-methylimidazolium chloride solution. 194.3 g of the 1-ethyl-3-methylimidazolium chloride solution, 380.5 g of bis(trifluoromethanesulfonyl)imide lithium salt, and 1000 g of dichloromethane are added sequentially to a flask, and the reaction is carried out at room temperature for 4 hours. After standing and separating the layers, the lower layer is washed with water until no precipitate is found when the washing liquid is tested with 5% silver nitrate. The dichloromethane is removed by rotary evaporation, and the solution is dehydrated under vacuum at 65°C to obtain the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.
[0042] The ionic liquid-based electrolyte of this embodiment has a viscosity of 75.5 Pa·s at 25°C and an electrochemical window of 5.1 V.
[0043] Example 5
[0044] In Example 2, succinic acid was replaced with vinylene carbonate, and everything else was the same as in Example 2.
[0045] The ionic liquid-based electrolyte in this embodiment has a viscosity of 45.7 Pa·s at 25°C and an electrochemical window of 5.2 V.
[0046] Example 6
[0047] The difference from Example 2 is that the mass ratio of ionic liquid, succinic acid, fluoroethylene carbonate, hydrofluoroether HFE-458 and lithium salt is 9:3:1:10:2, while the rest is the same as in Example 2.
[0048] The ionic liquid-based electrolyte in this embodiment has a viscosity of 76.3 Pa·s at 25°C and an electrochemical window of 5.1 V.
[0049] Comparative Example 1
[0050] The difference from Example 1 is that it does not contain a diluent, and the mass ratio of ionic liquid, succinic acid, fluoroethylene carbonate and lithium salt is 6:3:1:2.
[0051] The ionic liquid-based electrolyte in this comparative example has a viscosity >1000 Pa·s at 25 °C and an electrochemical window of 5.2 V.
[0052] Comparative Example 2
[0053] The electrolyte was a 1 mol / L LiPF6 solution, and the solvent was ethylene carbonate and diethyl carbonate in a volume ratio of 1:1.
[0054] The electrolyte in this comparative example has a viscosity of 51.2 Pa·s at 25 °C and an electrochemical window of 4.4 V.
[0055] The flammability and wettability of the electrolytes in Examples 1-6 and Comparative Examples 1-2 were tested. The flammability test involved dripping 0.5 mL of electrolyte onto a stainless steel cap and igniting it with a butane torch flame (approximately 3000°C) for 10 seconds, observing the combustion. The wettability test involved dripping 0.5 mL of electrolyte onto a PE diaphragm and observing the wetting.
[0056] Figure 1 This is a comparison chart of the flammability of electrolytes. (From...) Figure 1 It can be seen that the electrolyte in Comparative Example 2 is flammable, while the electrolytes in Examples 1-6 and Comparative Example 1 are all non-flammable. This result indicates that ionic liquid-based electrolytes have high safety.
[0057] Figure 2 This is a comparison chart of the wettability of electrolytes. (From...) Figure 2 It can be seen that the electrolyte of Comparative Example 1 exhibits a clear contact angle on the PE membrane, indicating that it cannot wet the PE membrane; while the electrolytes of Examples 1-6 and Comparative Example 2 did not show any visible contact angle on the PE membrane, indicating that the addition of a diluent to the ionic liquid-based electrolyte can achieve good wettability with the PE membrane.
[0058] Figure 3 This is a linear sweep voltammogram of the electrolyte. (From...) Figure 3 It can be seen that the electrolytes in Examples 1 to 6 all have an electrochemical window greater than 5V, exhibiting a wide electrochemical window.
[0059] The electrolytes from Examples 1-6 and Comparative Examples 1-2 were assembled into coin cells, and their electrochemical performance was tested. The coin cell preparation method was as follows: lithium iron phosphate, conductive agent SP, and binder PVDF were mixed at a mass ratio of 80:1:1, and N-methylpyrrolidone was used to prepare the slurry to obtain the positive electrode slurry. The positive electrode slurry was coated onto carbon-coated aluminum foil to achieve an areal density of 3.5 mg / cm³. 2 The positive electrode was prepared by assembling a lithium metal negative electrode, a positive electrode sheet, a polypropylene microporous membrane, and electrolytes from Examples 1-6 and Comparative Examples 1-2 into CR2032 coin cells. The cycle performance of the cells was tested at 25°C and 1C rate, and the rate performance was tested after 10 cycles at 1-5C. The electrochemical performance test results are shown in Table 1.
[0060] Table 1 Electrochemical performance test results
[0061] Figure 4 The image shows the charge-discharge curves of a lithium-ion battery assembled using the ionic liquid-based electrolyte of Example 2. Figure 5The graph shows the cycle performance of a lithium-ion battery assembled using the ionic liquid-based electrolyte of Example 2. Figure 6 The image shows the coulombic efficiency of a lithium-ion battery assembled using the ionic liquid-based electrolyte of Example 2. Figure 7 This is a rate performance graph of a lithium-ion battery assembled using the ionic liquid-based electrolyte of Example 2. Figures 4-7 It can be seen that the lithium-ion battery assembled using the ionic liquid-based electrolyte of Example 2 has a capacity retention rate of 98.63% after 1000 cycles at 1C rate, an initial discharge specific capacity of over 120mAh / g, a coulombic efficiency of over 99.9%, and excellent rate performance.
[0062] As can be seen from the above embodiments, the present invention provides an ionic liquid-based electrolyte and its application, which is compounded with non-flammable ionic liquid and diluent to fundamentally eliminate safety risks; lithium salt is mainly dissolved in ionic liquid and additives to form a locally high-concentration solvation structure, which preferentially forms a dense, stable and LiF-rich SEI film during charging and discharging, inhibiting the growth of lithium dendrites, improving coulombic efficiency and cycle stability, and enabling it to be used in conjunction with traditional commercial polyolefin separators without the need for glass fiber separators, thus exhibiting excellent electrochemical performance.
[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. An ionic liquid-based electrolyte, characterized in that, The ionic liquid-based electrolyte comprises an ionic liquid, a lithium salt, a diluent, and additives; The mass ratio of the diluent to the ionic liquid is 1~2:1; In the ionic liquid-based electrolyte, the mass fraction of lithium salt is 5-15%, and the mass fraction of additives is 15-25%.
2. The ionic liquid-based electrolyte according to claim 1, characterized in that, The ionic liquid comprises one or more of pyrrole borate, pyrrole sulfonyl imide salt, piperidine sulfonyl imide salt, imidazole sulfonyl imide salt, and quaternary ammonium sulfonyl imide salt.
3. The ionic liquid-based electrolyte according to claim 2, characterized in that, The pyrrole borate is N,N-dimethylpyrroletetrafluoroborate; The pyrrole sulfonyl imide salt comprises one or more of N-propyl-N-methylpyrrole bis(trifluoromethanesulfonyl imide), 1-ethyl-1-methylpyrrole bis(trifluoromethanesulfonyl imide), N-butyl-N-methylpyrrole bis(trifluoromethanesulfonyl imide), and N-butyl-N-methylpyrrole bis(fluorosulfonyl imide). The piperidine sulfonyl imide salt is 1-propyl-1-methylpiperidine bis(trifluoromethylsulfonyl imide salt); The imidazole sulfonyl imide salt comprises one or more of 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl imide), 1,2-bis(2-(N-methylimidazol)ethoxy)ethane bis(fluorosulfonyl imide) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide). The quaternary ammonium sulfonyl imide salt is N-methoxyethyl-N-methyldiethylammonium bis(trifluoromethanesulfonyl)imide salt.
4. The ionic liquid-based electrolyte according to any one of claims 1 to 3, characterized in that, The lithium salt comprises one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium difluorobis(oxalato)phosphate, and lithium difluorophosphate.
5. The ionic liquid-based electrolyte according to claim 4, characterized in that, The additive comprises one or more of vinylene carbonate, trimethyl phosphate, fluoroethylene carbonate, 1,3-propane sulphol, tris(trimethylsilyl)borate, lithium difluorooxalate borate, lithium nitrate, and succinic anhydride.
6. The ionic liquid-based electrolyte according to claim 5, characterized in that, The diluent comprises one or more of hydrofluoroether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.
7. The application of the ionic liquid-based electrolyte according to any one of claims 1 to 6 in lithium-ion batteries, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an ionic liquid-based electrolyte, wherein the separator is a polyolefin separator.
8. The application according to claim 7, characterized in that, The negative electrode is lithium metal.