Electrolyte solution, electrolyte and preparation method therefor, and lithium-ion battery

Abstract

An electrolyte solution, an electrolyte and a preparation method therefor, and a lithium-ion battery. The electrolyte solution comprises an organic solvent, a lithium salt, and a polymer monomer, wherein the polymer monomer comprises an acrylate monomer and a thioether monomer. The thioether monomer can introduce disulfide bonds into a generated solid polymer, and the disulfide bonds have dynamic reversibility, allowing the reformation of a solid polymer interface protection layer at a crack in a solid electrolyte interphase.

Description

Electrolytes, electrolytes and their preparation methods and lithium-ion batteries

[0001] This application claims priority to Chinese Patent Application No. 202411818550.4, filed with the Chinese Patent Office on December 10, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, specifically to an electrolyte, an electrolyte solution, a method for preparing the same, and a lithium-ion battery. Background Technology

[0003] Lithium-ion batteries, characterized by high energy density, high power density, long lifespan, and no memory effect, are widely used in smart homes, smart wearables, smart communication tools, and the Internet of Things. Gel electrolytes, with their advantages of high mechanical strength, good electrochemical stability, and good thermal stability, are also used in lithium-ion batteries. Gel electrolytes are typically prepared using in-situ polymerization. During this process, the polymer monomers in the electrolyte participate in the formation of both the positive and negative electrode films, forming a solid electrolyte interphase (SEI) film on the surfaces of both the positive and negative electrode material particles. Invention Overview

[0004] However, during long-term charge-discharge cycles, the volume of the positive and negative electrode material particles in lithium-ion batteries changes, causing the solid electrolyte interfacial film covering the surface of the positive and negative electrode material particles to rupture. After the solid electrolyte interfacial film ruptures, the electrolyte's repair effect on the solid electrolyte interfacial film is not ideal, affecting the battery's cycle performance and electrochemical performance.

[0005] This application provides an electrolyte comprising an organic solvent, a lithium salt, and a polymer monomer;

[0006] The polymer monomers include acrylate monomers and thioether monomers, and the structural formula of the thioether monomers is shown in Formula I:

[0007]

[0008] (I)

[0009] Where n is selected from 2, 3, 4, 5, 6, 7 or 8;

[0010] y and z are each independently selected from 0, 1, 2, 3, 4, 5, or 6;

[0011] Substituents R1-R6 are each independently selected from hydrogen atoms, halogens, cyano groups, isocyanate groups, C1-C18 substituted or unsubstituted straight-chain or branched alkyl groups, C1-C10 substituted or unsubstituted straight-chain or branched alkoxy groups, C3-C10 straight-chain or branched carboxyl ester groups, C3-C10 straight-chain or branched acrylate groups, C3-C10 straight-chain or branched alkenyl groups, C3-C10 straight-chain or branched alkynyl groups, C6-C26 unsubstituted aryl groups, C6-C26 aryl groups substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen groups, C6-C26 heterocyclic aryl groups substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen groups, C7-C27 unsubstituted benzyl groups, C7-C27 benzyl groups substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen groups, or combinations of these groups.

[0012] This application also provides an electrolyte, which is prepared from the above-described electrolyte solution.

[0013] This application also provides a method for preparing an electrolyte, comprising the following steps:

[0014] Provide the electrolyte described above;

[0015] Electrolyte is injected into the battery cell, left to stand, and then heated to solidify, thus obtaining the electrolyte.

[0016] This application also provides a lithium-ion battery, including the electrolyte described above or an electrolyte prepared using the method described above. Beneficial effects

[0017] The electrolyte provided in this application includes an organic solvent, a lithium salt, and polymer monomers. The polymer monomers include acrylate monomers and thioether monomers. These acrylate and thioether monomers can undergo polymerization to form a solid polymer. Simultaneously, during the polymerization process, the acrylate and thioether monomers participate in the formation of both the positive and negative electrode films, forming a solid electrolyte interface film containing the solid polymer on the surface of the positive and negative electrode material particles. This solid electrolyte interface film can reduce the contact between the positive and negative electrode materials and components such as organic solvents and lithium salts in the battery, and inhibit the contact between the positive and negative electrode materials and these components. The dissolution and release of transition metals and lattice oxygen in the positive and negative electrode materials reduce the generation of internal side reactions in the battery. When the solid electrolyte interface film on the surface of the positive and negative electrode material particles breaks, the solid polymer contains disulfide bonds, which have dynamic reversibility and covalent stability. These disulfide bonds can reform a solid polymer interface protective layer at the cracks in the solid electrolyte interface film, thereby effectively achieving self-repair of the solid electrolyte interface film. This reduces the contact between the positive and negative electrode active materials and components such as organic solvents and lithium salts, and the generation of side reactions, thereby improving the cycle performance and electrochemical performance of the battery. Embodiments of the present invention

[0018] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0019] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, where the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, where the first feature is at a lower horizontal level than the second feature.

[0020] In the description of this embodiment, the terms "upper," "lower," "left," "right," "front," and "rear," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for distinction in description and have no special meaning.

[0021] In related technologies, after the solid electrolyte interface film on the surface of the positive electrode material particles and the negative electrode material particles of lithium-ion batteries is broken, the repair effect of the electrolyte on the solid electrolyte interface film is not ideal, which affects the cycle performance and electrochemical performance of the battery and needs to be further improved.

[0022] Therefore, this application provides an electrolyte comprising an organic solvent, a lithium salt, and a polymer monomer; wherein the polymer monomer comprises acrylate monomers and thioether monomers, and the structural formula of the thioether monomer is shown in Formula I:

[0023]

[0024] (I)

[0025] Where n is selected from 2, 3, 4, 5, 6, 7 or 8;

[0026] y and z are each independently selected from 0, 1, 2, 3, 4, 5 or 6;

[0027] Substituents R1-R6 are each independently selected from hydrogen atoms, halogens, cyano groups, isocyanate groups, C1-C18 substituted or unsubstituted straight-chain or branched alkyl groups, C1-C10 substituted or unsubstituted straight-chain or branched alkoxy groups, C3-C10 straight-chain or branched carboxyl ester groups, C3-C10 straight-chain or branched acrylate groups, C3-C10 straight-chain or branched alkenyl groups, C3-C10 straight-chain or branched alkynyl groups, C6-C26 unsubstituted aryl groups, C6-C26 aryl groups substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen groups, C6-C26 heterocyclic aryl groups substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen groups, C7-C27 unsubstituted benzyl groups, C7-C27 benzyl groups substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen groups, or combinations of these groups.

[0028] In this embodiment, the polymer monomers include acrylate monomers and thioether monomers. On one hand, acrylate monomers and thioether monomers can undergo polymerization to form a solid polymer. Simultaneously, during the polymerization process, acrylate monomers and thioether monomers participate in the formation of the positive and negative electrode films, forming a solid electrolyte interface film containing the solid polymer on the surface of the positive and negative electrode material particles. This solid electrolyte interface film can reduce the contact between the positive and negative electrode materials and components such as organic solvents and lithium salts in the battery, and suppress the dissolution and release of transition metals and lattice oxygen from the positive and negative electrode materials, thereby reducing the generation of side reactions and gases inside the battery and lowering the battery capacity loss. On the one hand, the loss of the solid polymer can increase the thermal runaway temperature of the battery. On the other hand, the solid polymer contains disulfide bonds. When the solid electrolyte interfacial film on the surface of the positive and negative electrode material particles breaks, the disulfide bonds have dynamic reversibility and can reform the solid polymer interfacial protective layer at the cracks in the solid electrolyte interfacial film. This can effectively self-repair the solid electrolyte interfacial film and improve the cycle performance and electrochemical performance of the battery. In addition, thioether monomers containing carbon-carbon double bonds have high reactivity, which can improve the conversion rate of the reaction between thioether monomers and acrylate monomers, reduce the reaction temperature, reduce the residue of polymer monomers in the battery and the side effects of residual monomers on the battery, and improve the battery's service life.

[0029] In one embodiment, n is selected from 2 or 3.

[0030] In one embodiment, y and z are each independently selected from 0 or 1.

[0031] In one embodiment, the substituents R1-R6 are each independently selected from hydrogen atoms and / or C1-C18 straight-chain or branched alkyl groups.

[0032] In one embodiment, the sulfide monomer includes at least one selected from diethylene disulfide, diallyl disulfide, and diallyl trisulfide. In this embodiment, on the one hand, the aforementioned sulfide monomers are commercially available, making the raw materials readily available and saving on the synthesis steps of sulfide monomers, thus simplifying the battery manufacturing process; on the other hand, the aforementioned sulfide monomers do not contain gas-generating groups such as hydroxyl or amino groups, so when sulfide monomers remain in the battery, they are unlikely to generate gas, ensuring the battery's cycle performance and safety performance.

[0033] In one embodiment, the acrylate monomers include at least one selected from pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, bis(trimethylolpropane) tetraacrylate, methyl methacrylate, butyl methacrylate, polyethylene glycol diacrylate, polyethylene glycol diacrylate, and cyanoacrylate. The acrylate monomers in this embodiment are readily available and have low cost, which can reduce the raw material cost of the battery.

[0034] In one embodiment, the polymer monomer content in the electrolyte is 2%-34% by mass. Optionally, the polymer monomer content in the electrolyte can be any one or any two of 2%, 5%, 10%, 15%, 20%, 25%, 30%, and 34%. In this embodiment, if the polymer monomer content is too low, the resulting solid polymer will not effectively coat the positive and negative electrode particles. Simultaneously, it will reduce the repair effect of disulfide bonds in the solid polymer on the solid electrolyte interface film, leading to decreased stability of the solid electrolyte interface film on the surfaces of the positive and negative electrode particles. This makes the positive and negative electrode particles more susceptible to side reactions with organic solvents, lithium salts, and other components in the battery, consuming both positive and negative electrode materials and lithium ions. Conversely, if the polymer monomer content is too high, it can lead to an excessively large molecular weight of the solid polymer and an increase in side reactions, thus reducing the electrochemical performance of the battery.

[0035] In one embodiment, the acrylate monomers constitute 30%-85% of the polymer monomers by mass, and the thioether monomers constitute 15%-65% of the polymer monomers by mass. Optionally, the mass percentage of acrylate monomers in the polymer monomers can be any one or any two of the following: 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%; and the mass percentage of thioether monomers in the polymer monomers can be any one or any two of the following: 15%, 20%, 25%, 35%, 40%, 45%, 50%, 55%, 60%, 65%.

[0036] In this embodiment, if the content of acrylate monomers is too high and the content of thioether monomers is too low, it can easily lead to too few reversible repair sites in the solid polymer, resulting in an unsatisfactory repair effect of disulfide bonds on the solid electrolyte interface film. This can also increase the precipitation of transition metal ions during battery cycling, increase the generation of internal side reactions in the battery, and reduce battery performance. If the content of acrylate monomers is too low and the content of thioether monomers is too high, it can easily lead to too low mechanical strength of the solid electrolyte interface film formed on the surface of the positive and negative electrode material particles. When the solid electrolyte interface film is subjected to volume changes of the positive and negative electrode material particles, it is prone to severe rupture, resulting in an unsatisfactory self-repair effect. At the same time, since the cost of thioether monomers is high, it can easily increase the manufacturing cost of the battery.

[0037] In one embodiment, the polymer monomer further includes thiol monomers. In this embodiment, on the one hand, after the reaction between thioether monomers and acrylate monomers is completed, a small amount of thioether monomers usually remain. Thiol monomers can react with thioether monomers, consuming them. At the same time, since thioether monomers contain carbon-carbon double bonds, they have high reactivity, which can improve the conversion rate of the reaction between thioether monomers and thiol monomers, reduce the residue of polymer monomers, and thus reduce the side reactions between the residual polymer monomers and the electrode active materials. On the other hand, thiol monomers can undergo exchange reactions with disulfide bonds on solid polymers, causing some solid polymers to fold. The folded solid polymers accumulate at the interface between the positive and negative electrode material particles and the electrolyte, and can coat the surface of the positive and negative electrode material particles with a nanofilm layer. The nanofilm layer helps to reduce the contact between the positive and negative electrode material particles and components such as lithium salts and organic solvents, and inhibits the dissolution and release of transition metals and lattice oxygen in the positive and negative electrode material particles, reducing the occurrence of side reactions and gas generation inside the battery, reducing battery capacity loss, and improving the battery's thermal runaway temperature and cycle life.

[0038] In one embodiment, the thiol monomers include at least one selected from 1,3-ethanedithiol, benzenethiol, dodecylthiol, 1,4-butanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol, 1,5-pentanedithiol, and 2,3-butanedithiol.

[0039] In one embodiment, the mass percentage of thiol monomers in the polymer monomer is 0-65%. Optionally, the mass percentage of thiol monomers in the polymer monomer can be any one or any two of 0, 10%, 20%, 30%, 40%, 50%, 60%, and 65%. In this embodiment, if the content of thiol monomers is too high, it can easily lead to an increase in thiol monomer residues, thereby increasing the side reactions between thiol monomers and electrodes, causing battery gas production and capacity impairment; if the content of thiol monomers is too low, the effect of reducing the residual amount of thioether monomers is not ideal.

[0040] In one embodiment, the electrolyte further includes an initiator and / or additives.

[0041] In one embodiment, the organic solvent includes at least one selected from dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, ethylene carbonate, vinylene carbonate, methyl formate, ethyl formate, ethyl acetate, methyl propionate, ethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol tert-butyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, hexaethylene glycol dimethyl ether, and heptaethylene glycol.

[0042] In one embodiment, the lithium salt includes at least one of lithium nitrate, lithium hexafluorophosphate, lithium perchlorate, lithium difluorooxalate borate, lithium trifluoromethanesulfonylimide, lithium difluorosulfonylimide, lithium diacetate borate, lithium tetrafluoroborate, and lithium difluorophosphate.

[0043] In one embodiment, the initiator includes azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, diethyl azodicarboxylate, di-2-methoxyethyl azodicarboxylate, di-tert-butyl azodicarboxylate, diisopropyl azodicarboxylate, dibenzyl azodicarboxylate, dimethyl azobisisobutyrate, dimethyl azobenzene-4,4'-dicarboxylate, dibenzyl azodihydroxyacid, azodiacyldipiperidine, azodicarbonyldimorphine, azodicarboxamide, azobenzene, 4,4'-azobisisobutyronitrile, etc. At least one of the following: pyridine, diethyl 4,4'-azodibenzoate, 4-methyl-4-dimethylaminoazobenzene, 3,3-dimethylazobenzene, phenylazomalonide, tert-butane, methyl red, methyl orange, golden orange O, tert-butyl peroxide, cyclohexanone peroxide, dimethylsulfonyl peroxide, tert-butyl peroxide, tert-butyl peroxycarbonate, 2-butanone peroxide, dilauroyl peroxide, benzoyl peroxide, lithium persulfate, and lithium monosulfate.

[0044] In one embodiment, the additive includes at least one of vinylene carbonate, fluorovinyl carbonate, triethyl phosphite, 1,3-propanesulfonate lactone, ethylene sulfite, 1,3,2-dioxazothiophene-2,2-dioxide, 1,4-butanesulfonate lactone, phenyl methanesulfonate, adiponitrile, 3-methoxypropionitrile, hexane-1,3,6-tricarboxynitrile, ethylene glycol bis(propionitrile) ether, hexamethyldisilazane, and trimethylsilyldiethylamine.

[0045] In one embodiment, the organic solvent has a mass percentage of 30%-80% in the electrolyte. Optionally, the mass percentage of the organic solvent in the electrolyte can be any one or any two of 30%, 40%, 50%, 60%, 70%, 80%, etc.

[0046] In one embodiment, the lithium salt has a mass percentage of 5%-20% in the electrolyte. Optionally, the mass percentage of the lithium salt in the electrolyte can be any one or any two of 5%, 8%, 10%, 14%, 18%, 20%, etc.

[0047] In one embodiment, the initiator has a mass percentage of 0.01%-3% in the electrolyte. Optionally, the mass percentage of the initiator in the electrolyte can be any one or any two of 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0048] In one embodiment, the mass percentage of the additive in the electrolyte is 2%-30%. Optionally, the mass percentage of the additive in the electrolyte can be any one or any two of 2%, 5%, 10%, 15%, 20%, 25%, 30%, etc.

[0049] This application also provides an electrolyte, which is prepared from the above-mentioned electrolyte solution.

[0050] In this embodiment, the solid polymer in the electrolyte contains disulfide bonds. When the solid electrolyte interface film on the surface of the positive electrode material particles and the negative electrode material particles breaks, the disulfide bonds have dynamic reversibility and can reform the solid polymer interface protective layer at the crack of the solid electrolyte interface film, thereby effectively self-repairing the solid electrolyte interface film and improving the cycle performance and electrochemical performance of the battery.

[0051] This application also provides a method for preparing an electrolyte, comprising the following steps:

[0052] S1. Provide the electrolyte as described above;

[0053] S2. Inject the electrolyte into the battery cell, let it stand, and heat it to solidify to obtain the electrolyte.

[0054] In one embodiment, the method for preparing the electrolyte includes the following steps:

[0055] The prescribed amounts of organic solvent, lithium salt, polymer monomer, and other raw materials are mixed to obtain the electrolyte.

[0056] In one embodiment, other raw materials also include an initiator and / or additives in the formulation amount.

[0057] In one embodiment, mixing can be carried out in an argon atmosphere, a nitrogen atmosphere, or a dry air atmosphere, and this application is not limited thereto.

[0058] In one embodiment, the mixing temperature is 20°C-30°C, and / or the mixing time is 0.5h-3h. Optionally, the mixing temperature can be any one or any two of 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, etc.; the mixing time can be any one or any two of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, etc.

[0059] In one embodiment, the settling temperature is 20°C-35°C, and / or the settling time is 24h-72h. Optionally, the settling temperature can be any one or any two of 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, 35°C, etc.; the settling time can be any one or any two of 24h, 30h, 35h, 40h, 50h, 60h, 70h, 72h, etc.

[0060] In one embodiment, the heat curing temperature is 45℃-120℃, and / or the heat curing time is 8h-60h. Optionally, the heat curing temperature can be any one or any two of 45℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, etc.; the heat curing time can be any one or any two of 8h, 10h, 20h, 30h, 40h, 50h, 60h, etc.

[0061] This application also provides a lithium-ion battery, which includes the electrolyte described above or an electrolyte prepared by the method described above.

[0062] In this embodiment, the type of lithium-ion battery is not limited, and the lithium-ion battery can be one of the following: ternary soft-pack battery, ternary steel-cased battery, lithium cobalt oxide soft-pack battery, and lithium cobalt oxide steel-cased battery.

[0063] The above solution will be further explained below with reference to specific embodiments. Some embodiments of this application are described in detail below:

[0064] Example 1

[0065] This embodiment provides an electrolyte comprising: lithium salt, organic solvent, additives, initiator, and polymer monomer;

[0066] The lithium salt is lithium hexafluorophosphate, and its mass percentage in the electrolyte is 10.6%.

[0067] The organic solvent consists of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate, with a volume ratio of 1:1:1. The organic solvent accounts for 68% of the electrolyte by mass.

[0068] The additive consists of vinylene carbonate and 1,3-propanesulfonic acid lactone, and the additive accounts for 3% by mass in the electrolyte.

[0069] The initiator is azobisisobutyronitrile (AIBN), and the initiator's mass percentage in the electrolyte is 0.4%.

[0070] The polymer monomer is composed of diallyl disulfide and pentaerythritol tetraacrylate. The mass percentage of diallyl disulfide in the polymer monomer is 30%, the mass percentage of pentaerythritol tetraacrylate in the polymer monomer is 70%, and the mass percentage of the polymer monomer in the electrolyte is 18%.

[0071] This embodiment also provides a method for preparing a lithium battery, the specific method being:

[0072] (1) A slurry was prepared by mixing graphite (anode material), acetylene black (conductive agent), sodium carboxymethyl cellulose (binder), and styrene-butadiene rubber in a mass ratio of 97:1:0.5:1.5. This slurry was coated onto a copper foil current collector and dried under vacuum to obtain the anode sheet. The cathode material was NCM811 (LiNi) 0.8 Co 0.1 Mn 0.1 The conductive agent acetylene black and the binder polyvinylidene fluoride are prepared into a slurry in a mass ratio of 96:2:2, which is then coated onto an aluminum foil current collector and dried to obtain a positive electrode sheet. The positive electrode sheet, negative electrode sheet and separator are then assembled to obtain a battery cell.

[0073] (2) Under an argon atmosphere, the lithium salt, organic solvent, additives, initiator and polymer monomers of the above formula are mixed at an ambient temperature of 20°C to obtain an electrolyte.

[0074] (3) Inject the electrolyte into the cell, vacuum seal, let stand, heat to solidify, and obtain the electrolyte. The vacuum degree of vacuum sealing is -90kPa, the temperature of standing is 30℃, the standing time is 30h, the temperature of heating to solidify is 70℃, and the heating to solidify time is 32h.

[0075] (4) Cool the cell containing electrolyte to room temperature, form, and test capacity to obtain a lithium-ion battery.

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is:

[0078] The polymer monomer is composed of diethylene disulfide and pentaerythritol tetraacrylate, with diethylene disulfide accounting for 30% by mass and pentaerythritol tetraacrylate accounting for 70% by mass. The rest is the same as in Example 1.

[0079] Example 3

[0080] The difference between Example 3 and Example 1 is:

[0081] The polymer monomer is composed of diallyl disulfide and pentaerythritol hexaacrylate, with diallyl disulfide accounting for 30% by mass and pentaerythritol hexaacrylate accounting for 70% by mass. The rest is the same as in Example 1.

[0082] Example 4

[0083] The difference between Example 4 and Example 1 is:

[0084] The polymer monomers consist of diallyl disulfide, pentaerythritol tetraacrylate and 1,4-butanedithiol. Based on the total mass of the polymer monomers as 100%, the mass fraction of diallyl disulfide is 30%, the mass fraction of pentaerythritol tetraacrylate is 60%, and the mass fraction of 1,4-butanedithiol is 10%, and the rest is the same as in Example 1.

[0085] Example 5

[0086] The difference between Example 5 and Example 1 is:

[0087] The polymer monomers consist of diallyl disulfide, pentaerythritol tetraacrylate and benzenethiol. Based on the total mass of the polymer monomers as 100%, the mass fraction of diallyl disulfide is 30%, the mass fraction of pentaerythritol tetraacrylate is 60%, the mass fraction of benzenethiol is 10%, and the rest is the same as in Example 1.

[0088] Example 6

[0089] The difference between Example 6 and Example 1 is:

[0090] The polymer monomer in the electrolyte is 2% by mass, and the rest is the same as in Example 1.

[0091] Example 7

[0092] The difference between Example 7 and Example 1 is:

[0093] The polymer monomer in the electrolyte is 34% by mass, and the rest is the same as in Example 1.

[0094] Example 8

[0095] The difference between Example 8 and Example 1 is:

[0096] The polymer monomers consist of diallyl disulfide and pentaerythritol tetraacrylate. Based on the total mass of the polymer monomers as 100%, the mass fraction of diallyl disulfide is 15%, the mass fraction of pentaerythritol tetraacrylate is 85%, and the rest is the same as in Example 1.

[0097] Example 9

[0098] The difference between Example 9 and Example 1 is:

[0099] The polymer monomers consist of diallyl disulfide and pentaerythritol tetraacrylate. Based on the total mass of the polymer monomers as 100%, the mass fraction of diallyl disulfide is 65%, the mass fraction of pentaerythritol tetraacrylate is 35%, and the rest is the same as in Example 1.

[0100] Example 10

[0101] The difference between Example 10 and Example 1 is:

[0102] The polymer monomer is composed of diallyl disulfide and pentaerythritol tetraacrylate, with diallyl disulfide accounting for 75% by mass and pentaerythritol tetraacrylate accounting for 25% by mass. The rest is the same as in Example 1.

[0103] Comparative Example 1

[0104] The difference between Comparative Example 1 and Example 1 is as follows:

[0105] The polymer monomer is composed of diallyl disulfide, which accounts for 100% of the polymer monomer by mass, and the rest is the same as in Example 1.

[0106] Comparative Example 2

[0107] The difference between Comparative Example 2 and Example 1 is as follows:

[0108] The polymer monomer is composed of pentaerythritol tetraacrylate, which accounts for 100% of the polymer monomer by mass, and the rest is the same as in Example 1.

[0109] Comparative Example 3

[0110] The difference between Comparative Example 3 and Example 1 is as follows:

[0111] The polymer monomer is composed of diphenyl disulfide and pentaerythritol tetraacrylate, with diphenyl disulfide accounting for 30% by mass and pentaerythritol tetraacrylate accounting for 70% by mass. The rest is the same as in Example 1.

[0112] Test methods

[0113] The lithium-ion batteries obtained in Examples 1 to 10 and Comparative Examples 1 to 3 were subjected to performance testing, and the specific methods are as follows:

[0114] (1) Cyclic performance: The lithium-ion battery was tested at 25°C with constant current and constant voltage charge and discharge at 1C current density. The charge and discharge voltage window was 2.8V-4.2V.

[0115] (2) Rate performance: The lithium-ion battery was charged at a constant current and constant voltage at a current density of 1C and discharged at a constant current and constant voltage at a current density of 3C. The charge and discharge voltage window was 2.8V-4.2V.

[0116] (3) 130℃ thermal abuse pass rate: The lithium-ion battery is heated from room temperature (25℃) to 130℃ at a rate of 5℃ / min, and then kept at 130℃ for 1 hour. If it does not catch fire or explode, the battery is considered to have passed the test.

[0117] The test results are shown in Table 1 below:

[0118] Table 1

[0119]

[0120] 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 10 have good rate performance, excellent cycle performance, and high thermal abuse pass rate at 130°C. This indicates that the sulfide monomers of this application can introduce disulfide bonds into the generated solid polymer. The disulfide bonds have dynamic reversibility and can reform the solid polymer interface protective layer at the cracks of the solid electrolyte interface film, thereby effectively self-repairing the solid electrolyte interface film, reducing the contact between the positive and negative electrode materials and components such as organic solvents and lithium salts in the battery, reducing the generation of side reactions and gases inside the battery, increasing the thermal runaway temperature of the battery, and improving the cycle performance and electrochemical performance of the battery.

[0121] A comparison of Examples 1 to 7 with Comparative Examples 1 and 2 shows that the electrolytes of Examples 1 to 7 contain both acrylate monomers and thioether monomers. The high reactivity between acrylate monomers and thioether monomers can reduce the amount of residual polymer monomers, reduce side reactions between residual polymer monomers and electrode active materials, and reduce crosstalk reactions of residual polymer monomers under an electric field. At the same time, it effectively promotes self-repair of the solid electrolyte interface film, improving the cycle performance and electrochemical performance of the battery.

[0122] A comparison of Examples 1 to 10 and Comparative Example 3 shows that the thioether monomers in the electrolytes of Examples 1 to 10 contain carbon-carbon double bonds. Thioether monomers containing carbon-carbon double bonds have high reactivity, which can improve the conversion rate of the reaction between thioether monomers and acrylate monomers, reduce the reaction temperature, reduce the residue of polymer monomers in the battery and the side effects of residual monomers on the battery, and improve the cycle performance and rate performance of the battery.

[0123] A comparison of Examples 1 to 3 and Examples 4 and 5 shows that adding thiol monomers to the electrolyte can consume thioether monomers, effectively reducing the residue of polymer monomers. At the same time, thiol monomers can undergo exchange reactions with disulfide bonds on the solid polymer, inducing some solid polymers to fold. The folded solid polymers can coat the surface of the positive and negative electrode material particles with a nanofilm layer, which helps to reduce the occurrence of side reactions and gas generation inside the battery, reduce battery capacity loss, and improve the electrochemical performance and safety performance of the battery.

[0124] A comparison of Examples 1 to 3 and Example 10 shows that controlling the content of acrylate monomers and thioether monomers within an appropriate range can ensure the electrochemical performance and safety performance of the battery.

[0125] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An electrolyte, comprising: Organic solvents, lithium salts, and polymer monomers; The polymer monomers include acrylate monomers and thioether monomers, and the structural formula of the thioether monomers is shown in Formula I: （I） Where n is selected from 2, 3, 4, 5, 6, 7 or 8; y and z are each independently selected from 0, 1, 2, 3, 4, 5, or 6; Substituents R1-R6 are each independently selected from hydrogen atoms, halogens, cyano groups, isocyanate groups, C1-C18 substituted or unsubstituted straight-chain or branched alkyl groups, C1-C10 substituted or unsubstituted straight-chain or branched alkoxy groups, C3-C10 straight-chain or branched carboxyl ester groups, C3-C10 straight-chain or branched acrylate groups, C3-C10 straight-chain or branched alkenyl groups, C3-C10 straight-chain or branched alkynyl groups, C6-C26 unsubstituted aryl groups, C6-C26 aryl groups substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen groups, C6-C26 heterocyclic aryl groups substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen groups, C7-C27 unsubstituted benzyl groups, C7-C27 benzyl groups substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen groups, or combinations of these groups.

2. The electrolyte according to claim 1, wherein, The n is selected from 2 or 3; and / or The y and z are each independently selected from 0 or 1; and / or The substituents R1-R6 are each independently selected from hydrogen atoms and / or C1-C18 straight-chain or branched alkyl groups.

3. The electrolyte according to claim 1 or 2, wherein, The thioether monomers include at least one of diethylene disulfide, diallyl disulfide, and diallyl trisulfide.

4. The electrolyte according to any one of claims 1 to 3, wherein, The acrylate monomers include at least one of pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, bis(trimethylolpropane) tetraacrylate, methyl methacrylate, butyl methacrylate, polyethylene glycol diacrylate, polyethylene glycol diacrylate, and cyanoacrylate.

5. The electrolyte according to any one of claims 1 to 4, wherein, The polymer monomer has a mass percentage of 2%-34% in the electrolyte.

6. The electrolyte according to any one of claims 1 to 5, wherein, The acrylate monomers comprise 30%-85% by mass of the polymer monomers.

7. The electrolyte according to any one of claims 1 to 6, wherein, The thioether monomers constitute 15%-65% of the mass percentage of the polymer monomers.

8. The electrolyte according to any one of claims 1 to 7, wherein, The polymer monomers also include thiol monomers.

9. The electrolyte according to claim 8, wherein, The thiol monomers include at least one of 1,3-ethanedithiol, benzenethiol, dodecanethiol, 1,4-butanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol, 1,5-pentanedithiol, and 2,3-butanedithiol.

10. The electrolyte according to claim 8 or 9, wherein, The thiol monomers constitute 0-65% of the polymer monomers by mass.

11. The electrolyte according to any one of claims 1 to 10, wherein, The electrolyte also includes an initiator and / or additives.

12. The electrolyte according to claim 11, wherein, The initiators include azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, diethyl azodicarboxylate, di-2-methoxyethyl azodicarboxylate, di-tert-butyl azodicarboxylate, diisopropyl azodicarboxylate, dibenzyl azodicarboxylate, dimethyl azobisisobutyrate, dimethyl azobenzene-4,4'-dicarboxylate, dibenzyl azodihydroxyacid, azodiacyldipiperidine, azodicarbonyldimorphine, azodicarboxamide, azobenzene, and 4,4-azopyridine. At least one of the following: diethyl 4,4'-azodibenzoate, 4-methyl-4-dimethylaminoazobenzene, 3,3-dimethylazobenzene, phenylazomalonide, tert-butane azo, methyl red, methyl orange, golden orange O, tert-butyl peroxide, cyclohexanone peroxide, dimethylsulfonyl peroxide, tert-butyl peroxide, tert-butyl peroxycarbonate, isopropyl 2-butanone peroxide, dilauroyl peroxide, benzoyl peroxide, lithium persulfate, and lithium monosulfate; and / or The additives include at least one of the following: vinylene carbonate, fluorovinyl carbonate, triethyl phosphite, 1,3-propanesulfonate lactone, ethylene sulfite, 1,3,2-dioxazothiophene-2,2-dioxide, 1,4-butanesulfonate lactone, phenyl methanesulfonate, adiponitrile, 3-methoxypropionitrile, hexane-1,3,6-tricarboxynitrile, ethylene glycol bis(propionitrile) ether, hexamethyldisilazane, and trimethylsilyldiethylamine.

13. The electrolyte according to claim 11 or 12, wherein, The initiator has a mass percentage of 0.01%-3% in the electrolyte; and / or The additive is present in the electrolyte at a mass percentage of 2%-30%.

14. The electrolyte according to any one of claims 1 to 13, wherein, The organic solvent includes at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, ethylene carbonate, vinylene carbonate, methyl formate, ethyl formate, ethyl acetate, methyl propionate, ethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol tert-butyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, hexaethylene glycol dimethyl ether, and heptaethylene glycol; and / or The lithium salt includes at least one of lithium nitrate, lithium hexafluorophosphate, lithium perchlorate, lithium difluorooxalate borate, lithium trifluoromethanesulfonylimide, lithium difluorosulfonylimide, lithium diacetate borate, lithium tetrafluoroborate, and lithium difluorophosphate.

15. The electrolyte according to any one of claims 1 to 14, wherein, The organic solvent in the electrolyte has a mass percentage of 30%-80%; and / or The lithium salt in the electrolyte has a mass percentage of 5%-20%.

16. An electrolyte prepared from the electrolyte according to any one of claims 1 to 15.

17. A method for preparing the electrolyte as described in claim 16, comprising the following steps: Provide an electrolyte as described in any one of claims 1 to 15; The electrolyte is injected into the battery cell, left to stand, and then heated to solidify, thus obtaining the electrolyte.

18. The preparation method according to claim 17, wherein, The preparation method of the electrolyte includes the following steps: mixing the prescribed amounts of organic solvent, lithium salt, polymer monomer and other raw materials to obtain the electrolyte.

19. The preparation method according to claim 17 or 18, wherein, The other raw materials also include, in formula amounts, initiators and / or additives; and / or The mixing is carried out in an argon atmosphere, a nitrogen atmosphere, or a dry air atmosphere, and / or the mixing temperature is 20℃-30℃, and / or the mixing time is 0.5h-3h; and / or The settling temperature is 20℃-35℃, and / or the settling time is 24h-72h; and / or The temperature for heat curing is 45℃-120℃, and / or the time for heat curing is 8h-60h.

20. A lithium-ion battery comprising the electrolyte of claim 16 or an electrolyte prepared by any one of claims 17 to 19.

Images