Electrolyte with super-wide temperature range of use and electrochemical device thereof

Abstract

The application provides an electrolyte with a super-wide temperature use range, which comprises a composite solvent accounting for more than 70% of the total amount of the electrolyte, wherein the composite solvent comprises 5%-30% of a carbonate solvent, 10%-65% of a carboxylic acid ester solvent and 10%-65% of a mononitrile solvent in the composition of the electrolyte. The application solves the problem of the discharge of a battery under a temperature condition of-80 DEG C and below, which cannot be realized by the prior art, and the battery can also be normally used under a temperature ranging from room temperature to 50 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, in particular to an electrolyte with a super-wide temperature use range and an electrochemical device thereof. BACKGROUND

[0002] With the development of science and technology, the polar, deep space, deep sea exploration ability has become an important part of the national strength. However, the polar, deep space, deep sea temperature is usually below-60℃, which requires the electric mobile tool to work, which is very demanding on the power supply. Whether the power supply can work normally depends largely on the ability of the blood (electrolyte) to transmit ions. There are documents reporting that the gas liquefied electrolyte can work at-60℃ (Science 2017, 356, 6345), but the fluoromethane added is gaseous at room temperature, which is easy to cause safety hazards of the battery, in addition, its-60℃ capacity retention rate is only 60%, which is difficult to apply to-80℃ and below environment. Therefore, solving the problem of ion transmission of electrolyte under super-low temperature condition is the key. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides an electrolyte with a super-wide temperature use range and an electrochemical device thereof, which solves the problem of battery discharge under-80℃ and below temperature conditions which cannot be achieved by the prior art, and can also be used normally at room temperature to 50℃ range temperature.

[0004] The present application first provides an electrolyte with a super-wide temperature use range, which comprises a composite solvent accounting for more than 70% of the total amount of the electrolyte, wherein the composite solvent comprises 5%-30% of a carbonate solvent, 10%-65% of a carboxylic acid ester solvent and 10%-65% of a mononitrile solvent in the electrolyte composition.

[0005] Preferably, the composite solvent accounts for 80%-90% of the total amount of the electrolyte; the composite solvent can also be optimized as follows: 5%-20% of a carbonate solvent, 30%-54% of a carboxylic acid ester solvent and 20%-45% of a mononitrile solvent in the electrolyte composition; and can be further optimized as follows: 10%-20% of a carbonate solvent, 30%-50% of a carboxylic acid ester solvent and 25%-45% of a mononitrile solvent in the electrolyte composition.

[0006] The carbonate solvent is a cyclic carbonate solvent, preferably a cyclic carbonate solvent with no substituent or a substituent of an alkyl chain of not more than 3 on the ring, and more preferably at least one of vinyl carbonate and propylene carbonate.

[0007] The carboxylic acid ester solvent is a substituted or unsubstituted carboxylic acid ester solvent of not more than C7; preferably at least one of ethyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, methyl butyrate, methyl acetate, ethyl fluoroacetate, ethyl difluoroacetate, ethyl trifluoroacetate, ethyl trifluoropropionate, methyl trifluoropropionate, methyl fluoroacetate, methyl difluoroacetate, methyl trifluoroacetate.

[0008] The mononitrile solvent is a substituted or unsubstituted mononitrile solvent of C3-C6; preferably at least one of propionitrile, butyronitrile, valeronitrile, hexanonitrile, 4,4,4-trifluorobutyronitrile, perfluoroisobutyronitrile, heptafluorobutyronitrile, 4,4,4-trifluoro-3-oxobutyronitrile, 4,4,4-tris(trifluoromethyl)butyronitrile, 5,5,5-trifluorovaleronitrile, 3,3,3-trifluoro-propionitrile, 2,2-difluoropropanenitrile; and further preferably a mononitrile having a melting point of -100°C or lower.

[0009] The electrolyte of the present application further comprises 0-8% of an additive and a balance of a soluble metal salt.

[0010] Further, the additive can include one or more of sulfonate, sulfate, phosphate, phosphite, fluoroether, anhydride, 1,3 dioxane, 1,4 dioxane, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluoro oxalate borate, lithium bisoxalate borate, lithium difluoro oxalate phosphate, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, fluoroethylene carbonate, adiponitrile, 1,3,6 hexanetricarbonitrile, ethylene glycol bispropiononitrile ether, ethoxy pentafluorocyclotriphosphazene.

[0011] Further, the soluble metal salt is selected from one or more of XYn, wherein X is one of Li + , Na + , K + , Rb + , Cs + , Ca 2+ , Mg 2+ , Al 3+ ; and Y is one of Cl - , Br - , I - , BF4 - , PF6 - , FSI - , TFSI - , AsF6 - , SbF6 - , SiF6 - , ClO4 - , AlCl4 - , FSO3 - , CF3SO3 - , C4F9SO3- , [N(FSO2)2] - , [N(CF3SO2)2] - , [N(C2F5SO2)2] - , [N(FSO2)(CF3SO2)] - , CF3BF3 - , C2F5BF3 - and CB 11 H 12 - One of the following: n is the stoichiometric ratio of Y to X according to charge balance.

[0012] The application also provides an electrochemical device, comprising a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, a separator film, and the above-mentioned electrolyte.

[0013] The positive electrode active material comprises one or more positive electrode active substances capable of deintercalating lithium, sodium, and / or potassium ions, and the positive electrode active substance contains or does not contain a transition metal element, is doped or not doped with one or more doping elements, has or does not have a surface coating, and is mixed or not mixed with a compound having a coating; the negative electrode active material comprises at least one of natural graphite, artificial graphite, mesophase carbon microbeads, hard carbon, soft carbon, silicon (oxygen), silicon (oxygen)-carbon composite, Li-Sn alloy, Li-Ge alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithiated TiO2-Li4Ti5O 12 , MXene, Li-Al alloy, metallic lithium, sodium, potassium; and the separator film comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid.

[0014] The application has the beneficial effects that: by specific solvent compounding, an electrolyte product with a super-wide temperature application range is formed, which is expected to have a large capacity yield rate in the temperature range of-100℃ to 50℃. At the same time, the electrolyte of the application can be applied to various different battery systems, and further performance optimization can be carried out through further proportioning and selection of battery materials. BRIEF DESCRIPTION OF DRAWINGS

[0015] The technical solutions of the embodiments of the application will be further described in detail below with reference to the drawings and examples.

[0016] Fig. 1 The-80℃ discharge capacity curve of the system of embodiment 4 of the application.

[0017] Fig. 2 The first two circle charge-discharge curves of the system of embodiment 4 of the application at 45℃. DETAILED DESCRIPTION

[0018] The application will be further described below by the accompanying drawings and specific examples, but it should be understood that these examples are only for more detailed description and should not be understood as limiting the application in any form, i.e. not intended to limit the protection scope of the application.

[0019] The electrolyte of the application has a super-wide temperature use range, including 70%-90% of a composite solvent.

[0020] The composite solvent is an important guarantee for the low-temperature operation of the electrolyte of the application, including 5%-30% of a carbonate solvent, 10%-65% of a carboxylate solvent and 10%-65% of a mononitrile solvent in the electrolyte. According to the following experiments, the composition of the composite solvent can be further optimized as follows: 5%-20% of a carbonate solvent, 30%-54% of a carboxylate solvent and 20%-45% of a mononitrile solvent in the electrolyte; and further optimized as follows: 10%-20% of a carbonate solvent, 30%-50% of a carboxylate solvent and 25%-45% of a mononitrile solvent in the electrolyte.

[0021] The carbonate solvent is a cyclic carbonate solvent, and the cyclic structure brings very high dielectric constant, which is conducive to good cooperation with electrolyte ions to play a discharge role. However, the carbonate solvent has relatively large viscosity, which is not in the same order of magnitude as the viscosity of the carboxylate solvent and the mononitrile solvent. Therefore, in order to optimize and improve the flowability of the electrolyte and reduce ion migration resistance, the type of the cyclic carbonate solvent can be further optimized, preferably the carbon atom on the ring has no substituent or the substituent is an alkyl chain with not more than 3, and more preferably at least one of ethylene carbonate and propylene carbonate.

[0022] The carboxylate solvent is a substituted or unsubstituted carboxylate solvent with not more than C7, including at least one of ethyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, methyl butyrate, methyl acetate, ethyl fluoroacetate, ethyl difluoroacetate, ethyl trifluoroacetate, ethyl trifluoropropionate, methyl trifluoropropionate, methyl fluoroacetate, methyl difluoroacetate and methyl trifluoroacetate. Such carboxylate has low viscosity, which can effectively cooperate with the carbonate solvent to improve the flowability of the electrolyte, improve the migration rate of ions in the solvent and promote the capacity at low temperature.

[0023] The mononitrile solvent is at least one of C3-C6 substituted or unsubstituted mononitrile solvent, including propionitrile, butyronitrile, valeronitrile, hexanitrile, 4,4,4-trifluorobutyronitrile, perfluoroisobutyronitrile, heptafluorobutyronitrile, 4,4,4-trifluoro-3-oxobutyronitrile, 4,4,4-tris(trifluoromethyl)butyronitrile, 5,5,5-trifluorovaleronitrile, 3,3,3-trifluoro-propionitrile, 2,2-difluoropropanenitrile. Such mononitrile has high dielectric constant and low viscosity, and is matched with carboxylic acid ester in dielectric ability while reducing the viscosity of carboxylic acid ester, and makes up for the deficiency of carboxylic acid ester in oxidation and reduction performance. Specifically, the mononitrile of the present application has lower symmetry and greater polarity than dinitrile and trinitrile, which is beneficial to the reduction of the melting point of the solvent and the improvement of low-temperature performance, and is beneficial to the improvement of dielectric constant, forming a match in dielectric ability; at the same time, the cyano group has strong coordination ability and good stability at the positive electrode, which can improve the comprehensive oxidation resistance of the solvent composed of carbonate and carboxylic acid ester; the mononitrile can be well miscible with ester, and the freezing point temperature of the miscible system after adding the mononitrile is much lower than that of the single solvent, which is very beneficial to the improvement of low-temperature performance; according to the following experiment, the mononitrile with a melting point of below -100℃ can be further selected; however, acetonitrile with the shortest carbon chain is easily reduced at the negative electrode due to the small interval between methyl and cyano, which reduces the service life of the battery, so it is not a good solvent for the battery system, and the following comparative example also proves the limitation of acetonitrile in application.

[0024] In addition to the above-mentioned composite solvent, the electrolyte of the present application can also include 0-8% of an additive and the balance of a soluble metal salt. The addition of the additive can improve the mutual solubility between the soluble metal salt and the composite solvent, thereby promoting the effective performance of the capacity at low temperature.

[0025] The additive can include one or more of sulfonate, sulfate, phosphate, phosphite, fluorinated ether, acid anhydride, 1,3 dioxane, 1,4 dioxane, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluoro oxalate borate, lithium bisoxalate borate, lithium difluoro oxalate phosphate, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, fluorinated ethylene carbonate, adiponitrile, 1,3,6 hexanetricarbonitrile, ethylene glycol bispropionitrile ether, ethoxy pentafluorocyclo-triphosphazene.

[0026] The soluble metal salt is selected from one or more of XYn, wherein X is a metal Li + , Na + , K + , Rb + , Cs + , Ca 2+ , Mg 2+, Al 3+ Y is one of Cl - , Br - , I - , BF4 - , PF6 - , FSI - , TFSI - , AsF6 - , SbF6 - , SiF6 - , CIO4 - , AICI4 - , FSO3 - , CF3SO3 - , C4F9SO3 - , [N(FSO2)2] - , [N(CF3SO2)2] - , [N(C2F5SO2)2] - , [N(FSO2)(CF3SO2)] - , CF3BF3 - , C2F5BF3 - and CB 11 H 12 - n is the stoichiometric ratio of Y to X according to charge balance. The type of soluble metal salt can be selected according to the battery material system, for example, in a lithium battery or a sodium battery system, a soluble lithium salt or a soluble sodium salt is usually selected to prepare the electrolyte.

[0027] The above electrolyte can be applied to low-temperature applications of various battery systems, and has a wide application space. The electrochemical device includes a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, a separator film, and the electrolyte.

[0028] The positive electrode active material includes one or more positive electrode active substances capable of deintercalating lithium, sodium, and / or potassium ions, a positive electrode binder, and a positive electrode conductive agent.

[0029] The positive electrode active substance includes a lithium-, sodium-, and / or potassium-containing compound.

[0030] The lithium-, sodium-, and / or potassium-containing compound includes at least one of a transition metal-containing complex oxide or a transition metal-containing phosphate compound.

[0031] The transition metal element is one or more of Co, Ni, Mn, and Fe, thereby obtaining a higher voltage.

[0032] The chemical formula of the transition metal-containing complex oxide or the transition metal-containing phosphate compound is Ax M1O2, A y M2PO4, xA2MnO3·(1-x)AM3O2, A z (M4)2O4wherein M1, M2, M3, M4 each represent one or more transition metal elements, A represents lithium, sodium or potassium, 0.05≤x≤1.20, 0.05≤y≤1.20, 0.05≤z≤1.20.

[0033] The transition metal-containing complex oxide or the transition metal-containing phosphate compound can further contain a doping element selected from one or more of Al, Co, Mg, Ta, W, Nb, Zr, Ca, V, Mo, Cr, La, Sc, Lu, Y and B.

[0034] The transition metal-containing complex oxide or the transition metal-containing phosphate compound can have a coating on the surface thereof or can be mixed with another compound having a coating.

[0035] The coating is at least one coating element compound of an oxide of a coating element, a hydroxide of a coating element, a hydroxy oxide of a coating element, a carbonate or nitrate or phosphate or borate of a coating element, a hydroxycarbonate of a coating element.

[0036] The coating element compound is an amorphous body or a crystal.

[0037] The coating element is Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, Ta, Nb, La or a mixture thereof.

[0038] The positive electrode conductive agent is a carbon material, a metal material or a conductive polymer.

[0039] The negative electrode active material is at least one of natural graphite, artificial graphite, meso-carbon microbead, hard carbon, soft carbon, silicon (oxide), silicon (oxide)-carbon composite, Li-Sn alloy, Li-Ge alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithiated TiO2-Li4Ti5O 12 , MXene, Li-Al alloy, metallic lithium, sodium, potassium.

[0040] The separator film is at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide and aramid.

[0041] The separator film includes a porous layer provided on at least one surface of the separator film.

[0042] The porous layer includes inorganic particles and a binder.

[0043] The inorganic particles are at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.

[0044] The binder is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0045] To evaluate and verify the performance of the electrolyte and the electrochemical device prepared by the present application, the following devices of three different battery systems were prepared in a specific example manner and the performance was evaluated.

[0046] 1. Preparation of lithium ion battery

[0047] The positive active material lithium cobaltate (LCO), lithium manganate (LMO), or lithium nickel cobalt manganate (NCM622), conductive agent Super P, polyvinylidene fluoride (PVDF), and carbon nanotubes were mixed in a weight ratio of 95:2:2.5:0.5, N-methyl pyrrolidone (NMP) was added, and the mixture was stirred uniformly under the action of a vacuum stirrer to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry was 70 wt%. The obtained positive electrode slurry was uniformly coated on a positive electrode current collector aluminum foil, the aluminum foil coated with the positive electrode slurry was dried at 90°C, and then after cold pressing, cutting, and slitting, a positive electrode sheet was obtained.

[0048] The negative active material graphite, conductive agent Super P, sodium carboxymethyl cellulose (CMC), binder styrene-butadiene rubber (SBR), and carbon nanotubes were mixed in a weight ratio of 95:1.5:1.4:1.6:0.5, deionized water was added, and a negative electrode slurry was obtained under the action of a vacuum stirrer, wherein the solid content of the negative electrode slurry was 50 wt%; the negative electrode slurry was uniformly coated on a negative electrode current collector copper foil; the copper foil was dried at 80°C, and then after cold pressing, cutting, and slitting, it was dried at 110°C under vacuum conditions for 12h to obtain a negative electrode sheet.

[0049] In a dry argon atmosphere glove box, carbonate solvents, carboxylic acid ester solvents, and nitrile solvents were mixed in a certain proportion, then 0.5% vinyl sulfate, 2% fluoroethylene carbonate were added, dissolved and stirred thoroughly, then 12.5% lithium salt was added, and the mixture was uniformly mixed to obtain an electrolyte. The specific content ratio of the solvents in the electrolyte is shown in Table 1. Comparative Example 1 used a conventional electrolyte solvent EC:DMC=3:7.

[0050] The isolation film is a 16 μm thick polyethylene (PE) isolation film.

[0051] The positive electrode sheet, the isolation film, and the negative electrode sheet are stacked in order, with the isolation film between the positive electrode sheet and the negative electrode sheet to play a role of isolation. After the welding of the tab, the lithium ion battery is placed in an outer packaging aluminum plastic film, dried, injected with the prepared electrolyte, and subjected to vacuum packaging, standing, formation, shaping, capacity testing, and other processes.

[0052] The arrangements of the embodiments are shown in Table 1. The carbonate solvents are selected from ethylene carbonate (labeled as A) and propylene carbonate (labeled as B); the carboxylate solvents are selected from methyl acetate (labeled as 1) and ethyl acetate (labeled as 2); the nitrile compounds are selected from propionitrile (labeled as I) and butyronitrile (labeled as II); LiBF4 (labeled as M), LiFSI (labeled as N), and LiPF6 (labeled as P).

[0053] Table 1: Examples and Comparative Examples

[0054]

[0055] 2. Test Methods

[0056] (1) Test of Cycle Performance of Lithium Ion Batteries

[0057] The lithium ion battery is placed in a 25℃ constant temperature oven and allowed to stand for 2 hours to reach a constant temperature. The lithium ion battery that has reached a constant temperature is charged at a constant current of 0.1C to a voltage of 4.2V, and then discharged at a constant current of 0.1C to a voltage of 2V at -80℃, 25℃, and 45℃ for 2 hours. The discharge capacity of the battery is obtained, and the low-temperature discharge capacity retention rate is calculated as the low-temperature discharge capacity / room-temperature discharge capacity. The discharge capacity retention rates of the lithium ion battery at different temperatures are shown in Table 2.

[0058] 3. Test Results

[0059] Table 2: Test Results of System Performance

[0060]

[0061] As can be seen from Table 2, the electrolyte of the present application can play a good role at a low temperature of-80℃ in three different battery systems. The conventional electrolyte composition (Comparative Example 1) has already been unable to maintain a liquid state at this low temperature. Acetonitrile (Comparative Example 2) has a certain capacity play at-80℃ due to the limited action of the cyano group and the short chain length, but it is extremely limited, and acetonitrile begins to condense at-100℃. For carbonates, linear carbonates without a ring (Comparative Example 3) also have a solution maintaining state at a low temperature and a certain capacity play, but due to the poor dielectric performance, the overall capacity of the system is maintained at a very low level. In addition, from the overall perspective of the three different battery systems, the capacity play rate of the electrolyte of the present application for LMO and LCO is obviously better than that of the NCM622 system.

[0062] From the results of the examples, the optimized material and ratio in the composite solvent can further obtain the improvement of the capacity play rate. Since the carbonate solvent has a relatively higher viscosity order of magnitude, the amount thereof can be further optimized, and examples 8-11 can reflect that the carbonate solvent is better when the amount thereof is not more than 20%. In addition, the cyano group has a more optimal ratio with the carboxylate compound in order to fully play its role in the solvent system, and further combining examples 1-4 can obtain a more optimized composition range of the three solvents, wherein examples 2-3 are the best, and it can be known that the optimal composition of the three can be 10%-20% of the carbonate solvent, 30%-50% of the carboxylate solvent and 25%-45% of the mononitrile solvent.

[0063] Figs. 1-2 Examples 4 are taken as examples, respectively, to show the discharge capacity curve of the electrolyte of the present application at-80℃ and the first two circle charge-discharge curves at 45℃. It can be seen that the electrolyte of the present application has a good capacity play rate, which indicates a very wide temperature application range.

[0064] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An electrolyte with an ultra-wide temperature use range, comprising a composite solvent, the composite solvent comprising 5%-20% of a carbonate solvent, 30%-54% of a carboxylate solvent, and 20%-45% of a butyronitrile, based on the total electrolyte composition. The carbonate solvent is a cyclic carbonate solvent with no substituent or an alkyl chain of no more than 3 substituents on the ring. The carboxylate solvent is a substituted or unsubstituted carboxylate solvent with no more than C7. The electrolyte is capable of delivering capacity in a temperature range of -100℃ to 50℃.

2. The electrolyte solution of ultra-wide temperature range of use according to claim 1, characterized in that, The composite solvent accounts for more than 70% of the total electrolyte.

3. The electrolyte of ultra-wide temperature range of use according to claim 1, characterized in that, The composite solvent accounts for 80%-90% of the total electrolyte.

4. The electrolyte of ultra-wide temperature range of use according to claim 1, characterized in that, The composite solvent comprises 10%-20% of a carbonate solvent, 30%-50% of a carboxylate solvent, and 25%-45% of a butyronitrile, based on the total electrolyte composition.

5. The electrolyte of ultra-wide temperature range of use according to claim 1, characterized in that, The carbonate solvent is at least one of ethylene carbonate and propylene carbonate.

6. The electrolyte of ultra-wide temperature range of use according to claim 1, characterized in that, The carboxylate solvent is at least one of ethyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, methyl butyrate, methyl acetate, ethyl fluoroacetate, ethyl difluoroacetate, ethyl trifluoroacetate, ethyl trifluoropropionate, methyl trifluoropropionate, methyl fluoroacetate, methyl difluoroacetate, and methyl trifluoroacetate.

7. The electrolyte of ultra-wide temperature range of use according to claim 1, characterized in that, 0-8% of an additive and a residual amount of a soluble metal salt are further included.

8. The electrolyte of ultra-wide temperature range of use according to claim 7, characterized in that, The additive comprises one or more of sulfonate, sulfate, phosphate, phosphite, fluoroether, anhydride, 1,3 dioxolane, 1,4 dioxolane, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluoro oxalate borate, lithium bisoxalate borate, lithium difluoro oxalate phosphate, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, fluoroethylene carbonate, adiponitrile, 1,3,6 hexanetricarbonitrile, ethylene glycol bispropionitrile ether, ethoxy pentafluorocyclotriphosphazene.

9. The electrolyte of ultra-wide temperature range of use according to claim 7, characterized in that, The soluble metal salt is selected from one or more of X, Y, and n, wherein X is the metal Li. + Na + K + 、Rb + Cs + Ca 2+ Mg 2+ Al 3+ One of them; Y is Cl - ,Br - I - BF4 - PF6 - FSI - TFSI - AsF6 - SbF6 - SiF6 - ClO4 - AlCl4 - FSO3 - CF3SO3 - C4F9SO3 - [N(FSO2)2] - [N(CF3SO2)2] - [N(C2F5SO2)2] - [N(FSO2)(CF3SO2)] - CF3BF3 - C2F5BF3 - and CB 11 H 12 - One of them; n is the stoichiometric ratio of Y to X obtained according to charge balance. 10.An electrochemical device, comprising a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, a separator film, and the electrolyte of any one of claims 1-9.

11. The electrochemical device of claim 10, wherein, The positive electrode active material includes one or more positive electrode active substances capable of deintercalating lithium, sodium, and / or potassium ions, the positive electrode active substance containing or not containing a transition metal element, being doped or not doped with one or more doping elements, having or not having a surface coating, being mixed or not mixed with a compound having a coating; the negative electrode active material includes at least one of natural graphite, artificial graphite, mesophase microcarbon, hard carbon, soft carbon, silicon (oxygen), silicon (oxygen)-carbon composite, Li-Sn alloy, Li-Ge alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithiated TiO2-Li4Ti5O 12 , MXene, Li-Al alloy, metallic lithium, sodium, potassium; the separator film includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid.

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