Electrolyte, electrolyte, preparation method of electrolyte and lithium ion battery

Abstract

The invention provides an electrolyte, an electrolyte, a preparation method of the electrolyte and a lithium ion battery. The electrolyte comprises an organic solvent, a lithium salt, a polymer monomer and an initiator, optionally, the initiator comprises an imidazole monomer and a monomer A, the monomer A comprises at least one of a sultone compound and a cyclic anhydride compound, and the imidazole monomer and the monomer A can react to generate the zwitterionic liquid. In the application, on one hand, in the process of generating the zwitterionic liquid through the reaction of the imidazole monomer and the monomer A, the polymerization reaction of the polymer monomer can be initiated; on the other hand, the imidazole monomer and the monomer A react to generate the zwitterionic liquid, and the zwitterionic liquid has relatively high chemical stability, so that even if the zwitterionic liquid is left in the battery, the zwitterionic liquid does not easily react with other components in the lithium ion battery, and the stability of the battery performance is maintained; in addition, the zwitterionic liquid can improve the mobility of lithium ions and the charge-discharge efficiency of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrolyte, an electrolyte and a preparation method thereof, and a lithium ion battery. Background Art

[0002] With the development of science and technology in recent years, lithium-ion batteries with high energy density and long cycle life are being widely used in many consumer electronic products such as smart wearables and mobile communications. Polymer electrolytes are used in lithium-ion batteries because of their flexibility, scalability, easy processing, and good compatibility with electrode interfaces. Polymer electrolytes are usually prepared by in-situ polymerization. During the in-situ polymerization process, polymer monomers in the electrolyte can undergo polymerization under external conditions and initiators, thereby forming polymer electrolytes in situ.

[0003] In the related art, there is usually a phenomenon of residual initiator after the polymerization reaction is completed, and azo initiators such as azobisisobutyronitrile and azobisisoheptanenitrile are generally used in traditional electrolytes. When these initiators remain in the battery, they are prone to produce side reactions in the battery, resulting in degradation of battery performance. Summary of the invention

[0004] The embodiments of the present invention provide an electrolyte, an electrolyte and a preparation method thereof, and a lithium ion battery, which can improve the technical problem of battery performance degradation caused by side reactions of residual initiators in the battery.

[0005] In a first aspect, an embodiment of the present invention provides an electrolyte, the electrolyte comprising an organic solvent, a lithium salt, a polymer monomer and an initiator;

[0006] The initiator comprises an imidazole monomer and a monomer A, wherein the monomer A comprises at least one of a sultone compound and a cyclic anhydride compound, and the imidazole monomer and the monomer A can react to generate a zwitterionic liquid.

[0007] In one embodiment, the imidazole monomer includes at least one of 1-vinyl imidazole, 2-methyl imidazole, 1-ethyl-2-methyl imidazole, 1H-benzotriazole, and N-acetylimidazole; and / or

[0008] The sultone compound includes at least one of 1,3-propane sultone, 1,5-propane sultone, propenyl-1,3-sultone, and 1,4-butane sultone; and / or

[0009] The cyclic anhydride compound includes at least one of succinic anhydride, maleic anhydride, 1,2-cyclohexanedicarboxylic anhydride, cyclobutane-1,2-dicarboxylic anhydride, phthalic anhydride, and 1,2,4-cyclohexanetricarboxylic anhydride.

[0010] In one embodiment, in the electrolyte, the mass fraction of the initiator is 1%-20%; and / or

[0011] In the initiator, the mass fraction of the imidazole monomer is 20%-60%, and the mass fraction of the monomer A is 20%-50%; and / or

[0012] In the monomer A, the mass fraction of the sultone compound is 0-50%, and the mass fraction of the cyclic anhydride compound is 0-50%.

[0013] In one embodiment, in the electrolyte, the mass fraction of the polymer monomer is 0.1%-20%; and / or

[0014] The polymer monomer includes at least one of 2-phenoxyethyl acrylate, 2,2,3,3-tetrafluoropropyl methacrylate, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, 2-(perfluorooctyl)ethyl methacrylate, acrylonitrile, 2-cyano-3-ethoxyethyl acrylate, adiponitrile, hexamethylene diisocyanate, and vinyltrimethoxysilane.

[0015] In one embodiment, the electrolyte further includes an additive and / or a cross-linking agent.

[0016] In one embodiment, in the electrolyte, the mass fraction of the cross-linking agent is 0.1%-5%; and / or

[0017] The crosslinking agent includes at least one of triethylene glycol dimethacrylate, diallyl disulfide, N,N-methylenebisacrylamide, propoxy neopentyl glycol diacrylate, pentaerythritol tetraacrylate, diallyl isophthalate, divinyl propylene terephthalate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, and divinylbenzene.

[0018] In one embodiment, in the electrolyte, the mass fraction of the organic solvent is 60%-80%; and / or

[0019] In the electrolyte, the mass fraction of the lithium salt is 7.5%-18%; and / or

[0020] In the electrolyte, the mass fraction of the additive is 1.5%-9%; and / or

[0021] The organic solvent comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate and propylene carbonate; and / or

[0022] The lithium salt comprises at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium tetrafluorooxalate phosphate, lithium bisfluorobisoxalate phosphate, lithium difluorophosphate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bisoxalate borate, and lithium difluorooxalate borate; and / or

[0023] The additive includes at least one of vinylene carbonate, fluoroethylene carbonate, vinyl vinyl carbonate, 1,3-propane sultone, fluoroethylene carbonate, allyl ethyl carbonate, vinyl acetate, vinyl sulfite, 1-propylene-1,3-sultone, vinyl sulfate, 3-fluoro-1,3-propane sultone, 1,3-propane sultone, trimethylsilane, vinyl vinyl sulfite, and dimethyl sulfoxide.

[0024] In a second aspect, an embodiment of the present invention provides an electrolyte, wherein the electrolyte is prepared from the electrolyte solution as described above.

[0025] In one embodiment, the electrolyte includes a zwitterionic liquid, and the zwitterionic liquid is generated by the reaction of an imidazole monomer and a monomer A, wherein the monomer A includes at least one of a sultone compound and a cyclic anhydride compound.

[0026] In a third aspect, an embodiment of the present invention provides a method for preparing an electrolyte, comprising the following steps:

[0027] providing an electrolyte as described above;

[0028] The electrolyte is injected into the battery cell and heated and solidified to obtain the electrolyte.

[0029] In one embodiment, the method for preparing the electrolyte comprises the following steps:

[0030] Evenly mixing the initiator and other raw materials in the formula amount to obtain the electrolyte;

[0031] The initiator includes an imidazole monomer and a monomer A, the monomer A includes at least one of a sultone compound and a cyclic anhydride compound, and the other raw materials include a formulated amount of an organic solvent, a lithium salt and a polymer monomer.

[0032] In one embodiment, the other raw materials further include a formulated amount of additives and a cross-linking agent; and / or

[0033] Before the heating and curing step, a packaging step and a standing step are also included.

[0034] In one embodiment, the mixing is performed in dry air, argon atmosphere or nitrogen atmosphere, and / or the mixing temperature is 20° C.-30° C.; and / or

[0035] The temperature of the heating and curing is 45°C-100°C, and / or the time of the heating and curing is 1h-24h; and / or

[0036] The packaging includes vacuum packaging, and the vacuum degree of the vacuum packaging is -70kPa to -90kPa; and / or

[0037] The standing temperature is 20°C-30°C, and / or the standing time is 12h-48h.

[0038] In a fourth aspect, an embodiment of the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, and the electrolyte as described above or an electrolyte prepared by the method as described above.

[0039] Beneficial effects of the embodiments of the present invention:

[0040] In an embodiment of the present invention, the electrolyte includes an organic solvent, a lithium salt, a polymer monomer and an initiator; wherein the initiator includes an imidazole monomer and a monomer A, the monomer A includes at least one of a sultone compound and a cyclic anhydride compound, and the imidazole monomer and the monomer A can react to form a zwitterionic liquid. In the present invention, on the one hand, the polymer monomer can be induced to undergo a polymerization reaction during the reaction of the imidazole monomer and the monomer A to form a zwitterionic liquid; on the other hand, the reaction product of the imidazole monomer and the monomer A is a zwitterionic liquid, which has high chemical stability, and the zwitterionic liquid remaining in the battery is not easy to react with other components in the lithium-ion battery, thereby improving the problem of battery performance deterioration due to the side reactions of the residual initiator in the battery. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state; while "inside" and "outside" refer to the outline of the device.

[0042] In the related art, the initiator of the lithium-ion battery remains in the battery after the polymerization reaction. The residual initiator is prone to cause side reactions in the battery, resulting in degradation of battery performance, which needs to be further improved.

[0043] To solve the above problems, an embodiment of the present application provides an electrolyte, which includes an organic solvent, a lithium salt, a polymer monomer and an initiator; wherein the initiator includes an imidazole monomer and a monomer A, and the monomer A includes at least one of a sultone compound and a cyclic anhydride compound, and the imidazole monomer and the monomer A can react to form a zwitterionic liquid.

[0044] In this embodiment, the sultone compounds and cyclic anhydride compounds having a cyclic structure have high reactivity, so that the sultone compounds and cyclic anhydride compounds can undergo a ring-opening reaction with the imidazole monomers under relatively low temperature conditions to generate ionic liquids, and the relatively low reaction temperature helps to reduce the occurrence of side reactions; in addition, the polymer monomers can be induced to undergo a polymerization reaction during the reaction of the imidazole monomers and the monomer A to generate the zwitterionic liquid; in addition, the reaction product of the imidazole monomers and the monomer A is a zwitterionic liquid, which has high chemical stability, and the zwitterionic liquid remaining in the battery is not easy to undergo side reactions with other components in the lithium-ion battery, thereby improving the problem of battery performance deterioration due to side reactions of the residual initiator in the battery.

[0045] In one embodiment, the imidazole monomer includes at least one of 1-vinylimidazole, 2-methylimidazole, 1-ethyl-2-methylimidazole, 1H-benzotriazole, and N-acetylimidazole.

[0046] In one embodiment, the sultone compound includes at least one of 1,3-propane sultone, 1,5-propane sultone, propenyl-1,3-sultone, and 1,4-butane sultone.

[0047] In one embodiment, the cyclic anhydride compound includes at least one of succinic anhydride, maleic anhydride, 1,2-cyclohexanedicarboxylic anhydride, cyclobutane-1,2-dicarboxylic anhydride, phthalic anhydride, and 1,2,4-cyclohexanetricarboxylic anhydride.

[0048] In one embodiment, in the electrolyte, the mass fraction of the initiator is 1%-20%; alternatively, the mass fraction of the initiator can be any one of 1%, 3%, 7%, 10%, 13%, 15%, 18%, 20%, etc. or a range between any two. In the present invention, if the content of the initiator is too little, the number of anions and cations generated by the initiator is reduced, which can easily cause the polymerization reaction rate to slow down, the polymerization reaction time to be prolonged, and the polymerization reaction to be incomplete, thereby reducing the conversion rate and production efficiency of the polymer monomer; if the content of the initiator is too much, the polymerization reaction rate may be too fast and cause implosion.

[0049] In one embodiment, in the initiator, the mass fraction of the imidazole monomer is 20%-60%, and the mass fraction of the monomer A is 20%-50%. Alternatively, the mass fraction of the imidazole monomer can be any one of 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc., or a range between any two thereof; the mass fraction of the monomer A can be any one of 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc., or a range between any two thereof.

[0050] In one embodiment, in monomer A, the mass fraction of the sultone compound is 0-50%, and the mass fraction of the cyclic anhydride compound is 0-50%. Optionally, the mass fraction of the sultone compound can be any one of 0, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc., or a range between any two thereof; the mass fraction of the cyclic anhydride compound can be any one of 0, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc., or a range between any two thereof.

[0051] In one embodiment, in the electrolyte, the mass fraction of the polymer monomer is 0.1%-20%. Optionally, the mass fraction of the polymer monomer can be any one of 0.1%, 1%, 3%, 8%, 10%, 13%, 16%, 18%, 20%, etc., or a range between any two.

[0052] In one embodiment, the polymer monomer includes at least one of 2-phenoxyethyl acrylate, 2,2,3,3-tetrafluoropropyl methacrylate, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, 2-(perfluorooctyl)ethyl methacrylate, acrylonitrile, 2-cyano-3-ethoxyethyl acrylate, adiponitrile, hexamethylene diisocyanate, and vinyltrimethoxysilane.

[0053] In one embodiment, the electrolyte further comprises a crosslinking agent. In the present invention, the crosslinking agent connects the molecules or polymer segments in the electrolyte through chemical bonds, so that the electrolyte forms a more stable three-dimensional network structure, thereby improving the mechanical properties, thermal stability, chemical stability and electrochemical stability of the electrolyte.

[0054] In one embodiment, in the electrolyte, the mass fraction of the crosslinking agent is 0.1%-5%. Optionally, the mass fraction of the crosslinking agent can be any one of 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., or a range between any two.

[0055] In one embodiment, the crosslinking agent includes at least one of triethylene glycol dimethacrylate, diallyl disulfide, N,N-methylenebisacrylamide, propoxy neopentyl glycol diacrylate, pentaerythritol tetraacrylate, diallyl isophthalate, divinyl propylene terephthalate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, and divinylbenzene.

[0056] In one embodiment, the electrolyte further includes an additive.

[0057] Optionally, the organic solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate, and propylene carbonate.

[0058] Optionally, the lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium tetrafluorooxalate phosphate, lithium bisfluorobisoxalate phosphate, lithium difluorophosphate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bisoxalate borate, and lithium difluorooxalate borate.

[0059] Optionally, the additive includes at least one of vinylene carbonate, fluoroethylene carbonate, vinyl vinyl carbonate, 1,3-propane sultone, fluoroethylene carbonate, allyl ethyl carbonate, vinyl acetate, vinyl sulfite, 1-propylene-1,3-sultone, vinyl sulfate, 3-fluoro-1,3-propane sultone, 1,3-propane sultone, trimethylsilane, vinyl vinyl sulfite, and dimethyl sulfoxide.

[0060] In one embodiment, in the electrolyte, the mass fraction of the organic solvent is 60%-80%. Optionally, the mass fraction of the organic solvent can be any one of 60%, 64%, 68%, 70%, 74%, 80%, etc. or a range between any two.

[0061] In one embodiment, in the electrolyte, the mass fraction of the lithium salt is 7.5%-18%. Optionally, the mass fraction of the lithium salt can be any one of 7.5%, 10%, 13%, 15%, 18%, etc., or a range between any two.

[0062] In one embodiment, in the electrolyte, the mass fraction of the additive is 1.5%-9%; alternatively, the mass fraction of the additive can be any one of 1.5%, 3%, 5%, 7%, 9%, etc. or a range between any two.

[0063] The present application also provides an electrolyte, which is prepared from the electrolyte as described above.

[0064] In this embodiment, the electrolyte contains imidazole monomers and monomer A. During the reaction of the imidazole monomers and monomer A to generate a zwitterionic liquid, the polymer monomers can be induced to undergo an in-situ polymerization reaction to generate a solid electrolyte. The solid electrolyte has the advantages of high mechanical strength, good electrochemical stability, good thermal stability, etc., and can significantly improve the safety performance of lithium-ion batteries.

[0065] In one embodiment, the electrolyte includes a zwitterionic liquid, which is generated by the reaction of an imidazole monomer and a monomer A, wherein the monomer A includes at least one of a sultone compound and a cyclic anhydride compound. In this embodiment, on the one hand, the reaction product of the imidazole monomer and the monomer A is a zwitterionic liquid, which has high chemical stability and thermal stability, and the zwitterionic liquid in the electrolyte is not easy to react with other components in the lithium ion battery, thereby improving the problem of battery performance deterioration caused by the side reaction of the residual initiator in the battery, and optimizing the battery cycle performance; on the other hand, the zwitterionic liquid has good conductivity, which can accelerate the transmission speed and mobility of lithium ions in the electrolyte, thereby improving the charge and discharge rate and energy density of the lithium ion battery.

[0066] The present application also provides a method for preparing an electrolyte, comprising the following steps:

[0067] S1, providing the electrolyte as described above;

[0068] S2. Inject the electrolyte into the battery cell, heat and solidify it to obtain the electrolyte.

[0069] In one embodiment, the method for preparing the electrolyte comprises the following steps:

[0070] S3, mixing the initiator and other raw materials in the formula amount uniformly to obtain an electrolyte;

[0071] Optionally, the initiator includes an imidazole monomer and a monomer A, the monomer A includes at least one of a sultone compound and a cyclic anhydride compound, and other raw materials include a formulated amount of an organic solvent, a lithium salt and a polymer monomer.

[0072] In this embodiment, on the one hand, the process of the imidazole monomer and monomer A reacting to form a zwitterionic liquid can induce a polymerization reaction of the polymer monomer; on the other hand, the reaction product of the imidazole monomer and monomer A is a zwitterionic liquid, which has high chemical stability. The zwitterionic liquid remaining in the battery is not easy to react with other components in the lithium-ion battery, thereby improving the problem of battery performance deterioration due to side reactions of residual initiators in the battery.

[0073] Optionally, other raw materials also include a formula amount of cross-linking agent and additives. In the present invention, the cross-linking agent connects the molecules or polymer segments in the electrolyte through chemical bonds, so that the electrolyte forms a more stable three-dimensional network structure, thereby improving the mechanical properties, thermal stability, chemical stability and electrochemical stability of the electrolyte.

[0074] In one embodiment, in step S3, the mixing step can be performed in dry air, argon atmosphere or nitrogen atmosphere, which is not limited here. Optionally, the mixing temperature is 20° C.-30° C. Using a lower mixing temperature can prevent the lithium salt, additives and initiators in the electrolyte from being decomposed by heat.

[0075] In one embodiment, in step S2, the temperature of heating and curing is 45°C-100°C; optionally, the temperature of heating and curing can be any one of 45°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, etc. or a range between any two thereof. In this embodiment, if the temperature of heating and curing is too high, it is easy to cause side reactions and aging and cracking of the polymer; if the heating temperature is too low, it is easy to cause the polymerization reaction speed to slow down and inhibition to occur.

[0076] In one embodiment, in step S2, the heating and curing time is 1 hour to 24 hours. Optionally, the heating and curing time can be any one of 1 hour, 4 hours, 8 hours, 12 hours, 16 hours, 20 hours, 24 hours, etc. or a range between any two. In this embodiment, if the heating and curing time is too short, it is easy to cause incomplete polymerization and low molecular weight of the polymer; if the heating and curing time is too long, it is easy to cause too high molecular weight of the polymer and polymer aging.

[0077] In one embodiment, in step S2, a packaging step and a standing step are further included before the heating and curing step. The packaging includes vacuum packaging, and the vacuum degree of the vacuum packaging is -70 kPa to -90 kPa. Optionally, the vacuum degree of the vacuum packaging is any one of -70 kPa, -74 kPa, -78 kPa, -80 kPa, -84 kPa, -87 kPa, -90 kPa, etc., or a range between any two.

[0078] In this embodiment, the standing temperature is 20°C-30°C, and the standing time is 12h-48h. Optionally, the standing temperature can be any one of 20°C, 22°C, 25°C, 27°C, 29°C, 30°C, etc., or a range between any two thereof; the standing time can be any one of 12h, 15h, 20h, 25h, 30h, 35h, 40h, 44h, 48h, etc., or a range between any two thereof.

[0079] The present application also provides a lithium-ion battery, wherein the lithium-ion battery comprises a positive electrode, a negative electrode and the electrolyte as described above or an electrolyte prepared by the method as described above.

[0080] In this embodiment, the type of lithium-ion battery is not limited, and the lithium-ion battery can be one of a ternary soft-pack battery, a ternary steel-shell battery, a lithium cobalt oxide soft-pack battery, and a lithium cobalt oxide steel-shell battery.

[0081] The above scheme is further described below in conjunction with specific implementation examples. The preferred embodiments of the present application are described in detail as follows:

[0082] Example 1

[0083] This embodiment provides an electrolyte solution, including: an organic solvent, a lithium salt, an additive, an initiator, a cross-linking agent, and a polymer monomer.

[0084] The lithium salt is lithium hexafluorophosphate, and the mass of the lithium salt accounts for 12% of the mass of the electrolyte.

[0085] The organic solvents are ethylene carbonate and ethyl methyl carbonate, and the mass of the organic solvents accounts for 61.4% of the mass of the electrolyte.

[0086] The additive is vinylene carbonate, and the mass of the additive accounts for 1.6% of the mass of the electrolyte.

[0087] The cross-linking agent is triethylene glycol dimethacrylate, and the mass of the cross-linking agent accounts for 5% of the mass of the electrolyte.

[0088] The polymer monomer is pentaerythritol tetraacrylate, and the mass of the polymer monomer accounts for 15% of the mass of the electrolyte.

[0089] The initiator consists of 1-ethyl-2-methylimidazole and 1,3-propane sultone, and the mass of the initiator accounts for 5% of the mass of the electrolyte; based on the total mass of the initiator being 100%, the mass fraction of 1-ethyl-2-methylimidazole is 50%, and the mass fraction of 1,3-propane sultone is 50%.

[0090] This embodiment also provides a method for preparing a lithium ion battery, the specific method is:

[0091] (1) A negative electrode material graphite, a conductive agent acetylene black, and a binder sodium carboxymethyl cellulose and styrene-butadiene rubber were prepared into a slurry in a mass percentage of 94:1:2:3, coated on a copper foil current collector, and vacuum dried to obtain a negative electrode sheet; a positive electrode material NCM811 (LiNi 0.8 Co 0.1 Mn 0.1O2), acetylene black as a conductive agent and polyvinylidene fluoride as a binder are prepared into a slurry in a mass ratio of 95:3:2 and coated on an aluminum foil current collector, and then dried by blasting to obtain a positive electrode sheet. The positive electrode sheet, the negative electrode sheet and the separator are assembled to obtain a battery cell.

[0092] (2) Under an argon atmosphere, the organic solvent, lithium salt, additive, initiator, crosslinking agent and polymer monomer in the above-mentioned formula are mixed at 25° C. to obtain an electrolyte.

[0093] (3) Injecting the electrolyte into the battery cell, vacuum packaging, allowing it to stand, and heat curing to obtain the electrolyte, wherein the vacuum degree of the vacuum packaging is -80 kPa, the standing temperature is 25° C., the standing time is 24 h, the heating curing temperature is 60° C., and the heating curing time is 10 h.

[0094] (4) Assembling the battery cell containing the electrolyte and the aluminum shell together to obtain a lithium-ion battery.

[0095] Example 2

[0096] The difference between Example 2 and Example 1 is:

[0097] 1-Ethyl-2-methylimidazole was replaced by 1-vinylimidazole. Based on the total mass of the initiator being 100%, the mass fraction of 1-vinylimidazole was 50%. The rest was the same as in Example 1.

[0098] Example 3

[0099] The difference between Example 3 and Example 1 is that:

[0100] 1-ethyl-2-methylimidazole was replaced by N-acetylimidazole. Based on the total mass of the initiator being 100%, the mass fraction of N-acetylimidazole was 50%. The rest was the same as in Example 1.

[0101] Example 4

[0102] The difference between Example 4 and Example 1 is:

[0103] 1,3-propane sultone was replaced by 1,5-propane sultone. Based on the total mass of the initiator being 100%, the mass fraction of 1,5-propane sultone was 50%. The rest was the same as in Example 1.

[0104] Example 5

[0105] The difference between Example 5 and Example 1 is:

[0106] 1,3-propane sultone was replaced by maleic anhydride. Based on the total mass of the initiator being 100%, the mass fraction of maleic anhydride was 50%. The rest was the same as in Example 1.

[0107] Example 6

[0108] The difference between Example 6 and Example 1 is:

[0109] 1,3-propane sultone was replaced by succinic anhydride. Based on the total mass of the initiator being 100%, the mass fraction of succinic anhydride was 50%. The rest was the same as in Example 1.

[0110] Example 7

[0111] The difference between Example 7 and Example 1 is:

[0112] The initiator is composed of 1-ethyl-2-methylimidazole, 1,3-propane sultone and maleic anhydride. Taking the total volume of the initiator as 100%, the mass fraction of 1-ethyl-2-methylimidazole is 35%, the mass fraction of 1,3-propane sultone is 35%, and the mass fraction of maleic anhydride is 30%, and all the other are the same as in Example 1.

[0113] Example 8

[0114] The difference between Example 8 and Example 1 is:

[0115] The mass of the initiator accounts for 1% of the mass of the raw materials for preparing the electrolyte, and the rest is the same as in Example 1.

[0116] Example 9

[0117] The difference between Example 9 and Example 1 is:

[0118] The mass of the initiator accounts for 20% of the mass of the raw materials for preparing the electrolyte, and the rest is the same as in Example 1.

[0119] Comparative Example 1

[0120] The difference between Comparative Example 1 and Example 1 is:

[0121] The initiator is azobisisobutyronitrile, and the rest is the same as in Example 1.

[0122] Comparative Example 2

[0123] The difference between Comparative Example 2 and Example 1 is:

[0124] The initiator is azobisisoheptanonitrile, and the rest is the same as in Example 1.

[0125] Comparative Example 3

[0126] The difference between Comparative Example 3 and Example 1 is:

[0127] The initiator is tert-butyl peroxy-2-ethylhexanoate, and the rest is the same as in Example 1.

[0128] Comparative Example 4

[0129] The difference between Comparative Example 4 and Example 1 is:

[0130] The initiator is benzoyl peroxide, and the rest is the same as in Example 1.

[0131] Comparative Example 5

[0132] The difference between Comparative Example 5 and Example 1 is:

[0133] The initiator consists of 1-ethyl-2-methylimidazole and 1,3-propane sultone, and the mass of the initiator accounts for 0.5% of the mass of the raw materials for preparing the electrolyte; based on the total mass of the initiator being 100%, the mass fraction of 1-ethyl-2-methylimidazole is 50%, the mass fraction of 1,3-propane sultone is 50%, and the rest is the same as in Example 1.

[0134] Comparative Example 6

[0135] The difference between Comparative Example 6 and Example 1 is:

[0136] The initiator consists of 1-ethyl-2-methylimidazole and 1,3-propane sultone, and the mass of the initiator accounts for 30% of the mass of the raw materials for preparing the electrolyte; based on the total mass of the initiator being 100%, the mass fraction of 1-ethyl-2-methylimidazole is 50%, and the mass fraction of 1,3-propane sultone is 50%, and the rest is the same as in Example 1.

[0137] Test Method

[0138] The electrochemical performance of the lithium-ion batteries prepared in Examples 1 to 9 and Comparative Examples 1 to 6 was tested, and the specific method is as follows:

[0139] (1) Cycling performance: Full battery test of lithium-ion batteries at 25°C with constant current and constant voltage charging and discharging at a current density of 1C, with a charge and discharge voltage window of 3.0V-4.2V.

[0140] (2) Rate performance: The lithium-ion battery is charged at a current density of 1C and discharged at a current density of 3C with a constant current and constant voltage for full battery testing. The charge and discharge voltage window is 3.0V-4.2V.

[0141] The test results are shown in Table 1 below:

[0142] Table 1

[0143]

[0144] Based on the test results of the above embodiments and comparative examples, it can be seen that the lithium ion batteries prepared in Examples 1 to 9 have good rate performance and excellent cycle performance, which shows that the imidazole monomer and monomer A of the present invention can induce an in-situ polymerization reaction of the polymer monomer to generate a solid electrolyte during the reaction to generate a zwitterionic liquid; in addition, the reaction product of the imidazole monomer and monomer A is a zwitterionic liquid, which has high chemical stability and thermal stability. The zwitterionic liquid in the electrolyte is not easy to react with other components in the lithium ion battery, thereby improving the problem of battery performance deterioration caused by side reactions of residual initiators in the battery and improving the battery cycle performance; in addition, the zwitterionic liquid has good conductivity, which can accelerate the transmission speed and mobility of lithium ions in the electrolyte, thereby improving the rate performance of the lithium ion battery.

[0145] From the comparison of Examples 1 to 7 and Comparative Examples 1 to 4, it can be seen that Comparative Examples 1 to 4 use initiators such as azobisisobutyronitrile, azobisisoheptanenitrile, tert-butyl peroxide-2-ethylhexanoate, and benzoyl oxide, which leads to a decrease in the battery cycle performance and rate performance; the initiators of Examples 1 to 7 include imidazole monomers and monomer A, which can improve the battery cycle performance and the battery rate performance.

[0146] From the comparison of Examples 8 to 9 and Comparative Examples 5 to 6, it can be seen that when the initiator content is too little or too much, the battery cycle performance and rate performance will decrease. This is because when the initiator content is too little, the number of anions and cations produced by the initiator is reduced, resulting in a slower polymerization reaction rate, longer polymerization reaction time and incomplete polymerization reaction, thereby reducing the conversion rate of the polymer monomer; when the initiator content is too much, the polymerization reaction rate is too fast and explosion occurs.

[0147] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An electrolyte, characterized in that: include: Organic solvent, lithium salt, polymer monomer and initiator; The initiator comprises an imidazole monomer and a monomer A, wherein the monomer A comprises at least one of a sultone compound and a cyclic anhydride compound, and the imidazole monomer and the monomer A can react to generate a zwitterionic liquid.

2. The electrolyte according to claim 1, characterized in that The imidazole monomer includes at least one of 1-vinylimidazole, 2-methylimidazole, 1-ethyl-2-methylimidazole, 1H-benzotriazole, and N-acetylimidazole; and / or The sultone compound includes at least one of 1,3-propane sultone, 1,5-propane sultone, propenyl-1,3-sultone, and 1,4-butane sultone; and / or The cyclic anhydride compound includes at least one of succinic anhydride, maleic anhydride, 1,2-cyclohexanedicarboxylic anhydride, cyclobutane-1,2-dicarboxylic anhydride, phthalic anhydride, and 1,2,4-cyclohexanetricarboxylic anhydride.

3. The electrolyte according to claim 1 or 2, characterized in that In the electrolyte, the mass fraction of the initiator is 1%-20%; and / or In the initiator, the mass fraction of the imidazole monomer is 20%-60%, and the mass fraction of the monomer A is 20%-50%; and / or In the monomer A, the mass fraction of the sultone compound is 0-50%, and the mass fraction of the cyclic anhydride compound is 0-50%.

4. The electrolyte according to claim 1 or 2, characterized in that In the electrolyte, the mass fraction of the polymer monomer is 0.1%-20%; and / or The polymer monomer includes at least one of 2-phenoxyethyl acrylate, 2,2,3,3-tetrafluoropropyl methacrylate, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, 2-(perfluorooctyl)ethyl methacrylate, acrylonitrile, 2-cyano-3-ethoxyethyl acrylate, adiponitrile, hexamethylene diisocyanate, and vinyltrimethoxysilane.

5. The electrolyte according to claim 1 or 2, characterized in that: The electrolyte further comprises an additive and / or a cross-linking agent.

6. The electrolyte according to claim 5, characterized in that In the electrolyte, the mass fraction of the cross-linking agent is 0.1%-5%; and / or The crosslinking agent includes at least one of triethylene glycol dimethacrylate, diallyl disulfide, N,N-methylenebisacrylamide, propoxy neopentyl glycol diacrylate, pentaerythritol tetraacrylate, diallyl isophthalate, divinyl propylene terephthalate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, and divinylbenzene.

7. The electrolyte according to claim 5, characterized in that In the electrolyte, the mass fraction of the organic solvent is 60%-80%; and / or In the electrolyte, the mass fraction of the lithium salt is 7.5%-18%; and / or In the electrolyte, the mass fraction of the additive is 1.5%-9%; and / or The organic solvent comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate and propylene carbonate; and / or The lithium salt comprises at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium tetrafluorooxalate phosphate, lithium bisfluorobisoxalate phosphate, lithium difluorophosphate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bisoxalate borate, and lithium difluorooxalate borate; and / or The additive includes at least one of vinylene carbonate, fluoroethylene carbonate, vinyl vinyl carbonate, 1,3-propane sultone, fluoroethylene carbonate, allyl ethyl carbonate, vinyl acetate, vinyl sulfite, 1-propylene-1,3-sultone, vinyl sulfate, 3-fluoro-1,3-propane sultone, 1,3-propane sultone, trimethylsilane, vinyl vinyl sulfite, and dimethyl sulfoxide.

8. An electrolyte, characterized in that The electrolyte is prepared from the electrolyte according to any one of claims 1 to 7.

9. The electrolyte according to claim 8, characterized in that The electrolyte includes a zwitterionic liquid, which is generated by the reaction of an imidazole monomer and a monomer A, wherein the monomer A includes at least one of a sultone compound and a cyclic anhydride compound.

10. A method for preparing an electrolyte, characterized in that: The following steps are involved: Providing an electrolyte according to any one of claims 1 to 7; The electrolyte is injected into the battery cell and heated and solidified to obtain the electrolyte.

11. The preparation method according to claim 10, characterized in that: The preparation method of the electrolyte comprises the following steps: Evenly mixing the initiator and other raw materials in the formula amount to obtain the electrolyte; The initiator includes an imidazole monomer and a monomer A, the monomer A includes at least one of a sultone compound and a cyclic anhydride compound, and the other raw materials include a formulated amount of an organic solvent, a lithium salt and a polymer monomer.

12. The preparation method according to claim 11, characterized in that: The other raw materials also include a formulated amount of cross-linking agent and additives; and / or Before the heating and curing step, a packaging step and a standing step are also included.

13. The preparation method according to claim 12, characterized in that: The mixing is carried out in dry air, argon atmosphere or nitrogen atmosphere, and / or the mixing temperature is 20° C.-30° C.; and / or The temperature of the heating and curing is 45°C-100°C, and / or the time of the heating and curing is 1h-24h; and / or The packaging includes vacuum packaging, and the vacuum degree of the vacuum packaging is -70kPa to -90kPa; and / or The standing temperature is 20°C-30°C, and / or the standing time is 12h-48h.

14. A lithium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode and the electrolyte according to claim 8 or 9 or an electrolyte prepared by the method according to any one of claims 10 to 13.

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