Electrolyte, electrolyte preparation method and lithium ion battery

Abstract

The application provides an electrolyte, an electrolyte and a preparation method thereof and a lithium ion battery. The electrolyte comprises an organic solvent, a lithium salt and a polymer monomer, wherein the polymer monomer comprises an acrylate monomer and a sulfide monomer; the sulfide monomer can introduce a disulfide bond into a generated solid-state polymer; the disulfide bond has dynamic reversibility, can re-form a solid-state polymer interface protective layer at a crack of a solid electrolyte interface film, and thus effectively repairs the solid electrolyte interface film, reduces the contact between positive and negative electrode materials and components such as the organic solvent and the lithium salt in the battery, reduces the generation of a battery internal side reaction and the generation of gas, improves the thermal runaway temperature of the battery, and improves the cycle performance and electrochemical performance of the battery.

Description

TECHNICAL FIELD

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

[0002] Lithium ion batteries with high energy density, high power density, long life, no memory and other characteristics are widely used in smart home, smart wear, smart communication tools, Internet of Everything and other scenarios. Gel electrolyte has the advantages of high mechanical strength, good electrochemical stability, good thermal stability and is applied to lithium ion batteries. Gel electrolyte is usually prepared by in-situ polymerization. In the process of in-situ polymerization, the polymer monomer in the electrolyte can participate in the formation of the positive electrode film and the negative electrode film, and form a solid electrolyte interface film on the surface of the positive material particles and the negative material particles.

[0003] In related technologies, during long-term cycle charging and discharging of the lithium ion battery, the volume of the positive material particles and the negative material particles changes, which causes the solid electrolyte interface film (SEI) wrapped on the surface of the positive material particles and the negative material particles to break. After the solid electrolyte interface film breaks, the electrolyte has an unsatisfactory repairing effect on the solid electrolyte interface film, which affects the cycle performance and electrochemical performance of the battery. SUMMARY

[0004] Embodiments of the present application provide an electrolyte, an electrolyte and a preparation method thereof and a lithium ion battery, which can improve the technical problem that the electrolyte has an unsatisfactory repairing effect on the solid electrolyte interface film after the solid electrolyte interface film on the surface of the positive material particles and the negative material particles breaks.

[0005] In a first aspect, embodiments of the present application provide an electrolyte, comprising an organic solvent, a lithium salt and a polymer monomer;

[0006] The polymer monomer comprises an acrylic ester monomer and a thioether monomer, and the structure of the thioether monomer is shown as formula I:

[0007]

[0008] n is selected from 2, 3, 4, 5, 6, 7 or 8;

[0009] y and z are each independently selected from 0, 1, 2, 3, 4, 5 or 6;

[0010] each of the substituents R1-R6 is independently selected from a hydrogen atom, a halogen, a cyano group, an isocyanate group, a C1-C18 substituted or unsubstituted linear or branched alkyl group, a C1-C10 substituted or unsubstituted linear or branched alkoxy group, a C3-C10 linear or branched carboxylate group, a C3-C10 linear or branched acrylate group, a C3-C10 linear or branched alkenyl group, a C3-C10 linear or branched alkynyl group, a C6-C26 unsubstituted aryl group, a C6-C26 aryl group substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen, a C6-C26 heterocyclic aryl group substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen, a C7-C27 unsubstituted benzyl group, a C7-C27 benzyl group substituted with alkyl, alkoxy, hydroxyl, cyano and / or halogen, or a combination of these groups.

[0011] In an embodiment, the n is selected from 2 or 3; and / or

[0012] each of the y and the z is independently selected from 0 or 1; and / or

[0013] each of the substituents R1-R6 is independently selected from a hydrogen atom and / or a C1-C18 linear or branched alkyl group.

[0014] In an embodiment, the thioether monomer includes at least one of divinyl disulfide, diallyl disulfide, diallyl trisulfide; and / or

[0015] the acrylate monomer includes at least one of pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, methyl methacrylate, butyl methacrylate, polyethylene glycol dimethacrylate, polytriethylene glycol dimethacrylate, cyanoacrylate.

[0016] In an embodiment, the mass percentage of the polymer monomer in the electrolyte is 2%-34%; and / or

[0017] the mass percentage of the acrylate monomer in the polymer monomer is 30%-85%, and the mass percentage of the thioether monomer in the polymer monomer is 15%-65%.

[0018] In an embodiment, the polymer monomer further includes a thiol monomer.

[0019] In an embodiment, the thiol monomer includes at least one of 1,3-ethanedithiol, benzenethiol, dodecanethiol, 1,4-butanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol, 1,5-pentanedithiol, 2,3-butanedithiol; and / or

[0020] The mass percentage of the thiol monomer in the polymer monomer is 0-65%.

[0021] In an embodiment, the electrolyte further comprises an initiator and / or an additive.

[0022] In an embodiment, the organic solvent comprises 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

[0023] The lithium salt comprises at least one of lithium nitrate, lithium hexafluorophosphate, lithium perchlorate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium bis(acetic acid)borate, lithium tetrafluoroborate, lithium difluorophosphate; and / or

[0024] The initiator comprises at least one of azobisisobutyronitrile, azobisisopentyl nitrile, azobisisoheptyl nitrile, azobisdimethyl ethyl carbonate, di-2-methoxyethyl azodicarboxylate, di-tert-butyl azodicarboxylate, diisopropyl azodicarboxylate, dibenzyl azodicarboxylate, dimethyl azobis-2-methylpropionate, dimethyl azobenzene-4,4'-dicarboxylate, dibenzyl azodicarboxylate, azobisacyl dipiperidine, azobiscarbonyl dimorpholine, azodicarboxamide, azobenzene, 4,4-azopyridine, diethyl 4,4'-azobenzenedicarboxylate, 4-methyl 4-dimethylaminoazobenzene, 3,3-dimethylazobenzene, phenylazopropionitrile, azotert-butane, methyl red, methyl orange, aurin orange O, tert-butyl ketone peroxide, cyclohexanone peroxide, dimethylsulfonyl peroxide, tert-butyl benzene peroxide, tert-butyl peroxy isopropyl carbonate, 2-butyronitrile peroxide, dilauroyl peroxide, benzoyl peroxide, lithium persulfate, lithium monopersulfate; and / or

[0025] The additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, triethyl phosphite, 1,3-propanesultone, ethylene sulfite, 1,3,2-dioxazolothiophene-2,2-dioxide, 1,4-butanesultone, benzyl methanesulfonate, hexanedinitrile, 3-methoxypropanenitrile, hexane-1,3,6-trinitrile, ethylene glycol bis(propionitrile) ether, hexamethyldisilazane, trimethylsilyl diethyl amine; and / or

[0026] The mass percentage of the organic solvent in the electrolyte is 30%-80%; and / or

[0027] The mass percentage of the lithium salt in the electrolyte is 5%-20%; and / or

[0028] the mass percentage of the initiator in the electrolyte is 0.01%-3%; and / or

[0029] the mass percentage of the additive in the electrolyte is 2%-30%.

[0030] In a second aspect, embodiments of the present application provide an electrolyte prepared from the electrolyte as described above.

[0031] In a third aspect, embodiments of the present application provide a method for preparing an electrolyte, the method comprising the steps of:

[0032] providing the electrolyte as described above;

[0033] injecting the electrolyte into an electric cell, standing, heating and curing to obtain the electrolyte.

[0034] In an embodiment, the method for preparing the electrolyte comprises the step of mixing formula amount of organic solvent, lithium salt, polymer monomer and other raw materials to obtain the electrolyte.

[0035] In an embodiment, the other raw materials further comprise formula amount of initiator and / or additive; and / or

[0036] the mixing is performed in an argon atmosphere, a nitrogen atmosphere or a dry air atmosphere, and / or the temperature of the mixing is 20℃-30℃, and / or the time of the mixing is 0.5h-3h; and / or

[0037] the temperature of the standing is 20℃-35℃, and / or the time of the standing is 24h-72h; and / or

[0038] the temperature of the heating and curing is 45℃-120℃, and / or the time of the heating and curing is 8h-60h.

[0039] In a fourth aspect, embodiments of the present application provide a lithium ion battery comprising the electrolyte as described above or prepared by the method as described above.

[0040] The beneficial effects of embodiments of the present application are as follows:

[0041] In the embodiment of the present application, the polymer monomer includes an acrylic ester monomer and a sulfide monomer, the acrylic ester monomer and the sulfide monomer can undergo a polymerization reaction to generate a solid polymer, at the same time, the acrylic ester monomer and the sulfide monomer participate in the formation of a positive electrode film and a negative electrode film during the polymerization reaction, and can form a solid electrolyte interface film containing the solid polymer on the surface of the positive electrode material particles and the negative electrode material particles, the solid electrolyte interface film can reduce the contact between the positive and negative electrode materials and the organic solvent, lithium salt and other components in the battery, inhibit the dissolution and precipitation of transition metals and the release of lattice oxygen, and reduce the generation of side reactions in the battery; when the solid electrolyte interface film on the surface of the positive electrode material particles and the negative electrode material particles is broken, due to the presence of disulfide bonds in the solid polymer, the disulfide bonds have dynamic reversibility and the stability of covalent bonds, and can re-form a solid polymer interface protective layer at the crack of the solid electrolyte interface film, thereby effectively realizing self-repair of the solid electrolyte interface film, reducing the contact between the positive and negative active materials and the organic solvent, lithium salt and other components, and the generation of side reactions, and improving the cycle performance and electrochemical performance of the battery. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and "inner" and "outer" refer to the outline of the device.

[0043] In the related art, after the solid electrolyte interface film on the surface of the positive electrode material particles and the negative electrode material particles of the lithium ion battery is broken, the electrolyte cannot effectively repair the solid electrolyte interface film, which affects the cycle performance and electrochemical performance of the battery, and needs to be further improved.

[0044] To solve the above problems, the present application provides an electrolyte, which comprises an organic solvent, a lithium salt and a polymer monomer; wherein the polymer monomer comprises an acrylic ester monomer and a sulfide monomer, and the structure of the sulfide monomer is shown as formula I:

[0045]

[0046] wherein n is selected from 2, 3, 4, 5, 6, 7 or 8;

[0047] y and z are each independently selected from 0, 1, 2, 3, 4, 5, or 6;

[0048] each of the substituents R1-R6 is independently selected from a hydrogen atom, a halogen, a cyano group, an isocyanate group, a C1-C18 substituted or unsubstituted linear or branched alkyl group, a C1-C10 substituted or unsubstituted linear or branched alkoxy group, a C3-C10 linear or branched carboxylate group, a C3-C10 linear or branched acrylate group, a C3-C10 linear or branched alkenyl group, a C3-C10 linear or branched alkynyl group, a C6-C26 unsubstituted aryl group, a C6-C26 aryl group substituted with an alkyl group, an alkoxy group, a hydroxyl group, a cyano group, and / or a halogen, a C6-C26 heterocyclic aryl group substituted with an alkyl group, an alkoxy group, a hydroxyl group, a cyano group, and / or a halogen, a C7-C27 unsubstituted benzyl group, a C7-C27 benzyl group substituted with an alkyl group, an alkoxy group, a hydroxyl group, a cyano group, and / or a halogen, or a combination of these groups.

[0049] In the present embodiment, the polymer monomers include acrylate monomers and thioether monomers; on the one hand, the acrylate monomers and the thioether monomers can undergo a polymerization reaction to generate a solid polymer, and on the other hand, the acrylate monomers and the thioether monomers participate in the formation of a positive electrode film and a negative electrode film during the polymerization reaction, and can form a solid electrolyte interface film containing the solid polymer on the surface of the positive electrode material particles and the negative electrode material particles, which can reduce the contact between the positive and negative electrode materials and the organic solvent, lithium salt, and other components in the battery, inhibit the dissolution and precipitation of transition metals and the release of lattice oxygen, reduce the generation of side reactions and gas in the battery, reduce the loss of battery capacity, and improve the thermal runaway temperature of the battery; on the other hand, the solid polymer contains a disulfide bond, and when the solid electrolyte interface film on the surface of the positive electrode material particles and the negative electrode material particles is broken, the disulfide bond has dynamic reversibility, can re-form a solid polymer interface protective layer at the crack of the solid electrolyte interface film, and thus effectively repairs the solid electrolyte interface film, improves the cycle performance and electrochemical performance of the battery; in addition, the thioether monomers containing carbon-carbon double bonds have high reactivity, which can improve the conversion rate of the reaction between the thioether monomers and the acrylate monomers, reduce the reaction temperature, reduce the residue of the polymer monomers in the battery and the side effects of the residual monomers on the battery, and improve the service life of the battery.

[0050] In an embodiment, n is selected from 2 or 3.

[0051] In an embodiment, y and z are each independently selected from 0 or 1.

[0052] In an embodiment, each of the substituents R1-R6 is independently selected from a hydrogen atom and / or a C1-C18 linear or branched alkyl group.

[0053] In an embodiment, the sulfide monomer includes at least one of divinyl disulfide, diallyl disulfide, diallyl trisulfide. In this embodiment, on the one hand, the sulfide monomer can be directly commercially available, and the raw material is easy to obtain, and the synthesis step of the sulfide monomer can be saved, and the production process of the battery is simplified; on the other hand, the sulfide monomer does not contain gas generating groups such as hydroxyl and amino groups, and when the sulfide monomer remains in the battery, it is not easy to generate gas, and the cycle performance and safety performance of the battery are further ensured.

[0054] In an embodiment, the acrylate monomer includes at least one of pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, methyl methacrylate, butyl methacrylate, polyethylene glycol dimethacrylate, polytriethylene glycol dimethacrylate, cyanoacrylate. In this embodiment, the acrylate monomer is easy to obtain and has low cost, and the raw material cost of the battery can be reduced.

[0055] In an embodiment, the mass percentage of the polymer monomer in the electrolyte is 2%-34%. Alternatively, the mass percentage of the polymer monomer in the electrolyte is any one of 2%, 5%, 10%, 15%, 20%, 25%, 30%, 34%, or a range between any two of them. In this embodiment, if the content of the polymer monomer is too low, the coating effect of the generated solid polymer on the positive material particles and the negative material particles is not ideal, at the same time, the repair effect of the disulfide bond in the solid polymer on the solid electrolyte interface film is reduced, the stability of the solid electrolyte interface film on the surface of the positive material particles and the negative material particles is poor, and the positive material particles and the negative material particles are easy to react with the organic solvent, lithium salt and other components in the battery, consuming the positive and negative materials and lithium ions; if the content of the polymer monomer is too high, it is easy to cause the molecular weight of the solid polymer to be too large and the increase of the side reaction, and the electrochemical performance of the battery is reduced.

[0056] In an embodiment, the mass percentage of the acrylate monomer in the polymer monomer is 30%-85%, and the mass percentage of the sulfide monomer in the polymer monomer is 15%-65%. Alternatively, the mass percentage of the acrylate monomer in the polymer monomer is any one of 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or a range between any two of them; the mass percentage of the sulfide monomer in the polymer monomer is any one of 15%, 20%, 25%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or a range between any two of them.

[0057] In the present embodiment, if the content of the acrylate monomer is too much and the content of the sulfide monomer is too little, it is easy to cause too few reversible repair sites in the solid polymer, the repair effect of the disulfide bond on the solid electrolyte interface film is not ideal, the precipitation of transition metal ions in the battery during the battery cycle is increased, the generation of side reactions in the battery is increased, and the battery performance is reduced; if the content of the acrylate monomer is too little and the content of the sulfide monomer is too much, it is easy to cause the mechanical strength of the solid electrolyte interface film generated on the surface of the positive material particles and the negative material particles to be too low, the solid electrolyte interface film is easy to be severely cracked when coping with the volume change of the positive material particles and the negative material particles, resulting in an ideal self-repairing effect, and at the same time, due to the high cost of the sulfide monomer, the manufacturing cost of the battery is easily increased.

[0058] In an embodiment, the polymer monomer further includes a thiol monomer. In the present embodiment, on the one hand, after the reaction of the sulfide monomer with the acrylate monomer is completed, a small amount of sulfide monomer is usually left, the thiol monomer can react with the sulfide monomer, further consuming the sulfide monomer, and at the same time, since the sulfide monomer contains a carbon-carbon double bond, the sulfide monomer has high reactivity, which can improve the conversion rate of the reaction between the sulfide monomer and the thiol monomer, reduce the residue of the polymer monomer, and further reduce the side reaction between the residual polymer monomer and the electrode active material; on the other hand, the thiol monomer can exchange with the disulfide bond on the solid polymer, causing part of the solid polymer to fold, the folded solid polymer is gathered at the interface between the positive material particles and the negative material particles and the electrolyte, and can coat a layer of nanometer film on the surface of the positive material particles and the negative material particles, which is conducive to reducing the contact between the positive material particles and the negative material particles and lithium salt, organic solvent and other components, inhibiting the dissolution and precipitation of transition metal and the release of lattice oxygen, reducing the occurrence of side reactions and the generation of gas in the battery, reducing the loss of battery capacity, and improving the thermal runaway temperature and cycle life of the battery.

[0059] In an embodiment, the thiol monomer includes at least one of 1,3-ethanedithiol, phenyl mercaptan, dodecanethiol, 1,4-butanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol, 1,5-pentanedithiol, and 2,3-butanedithiol.

[0060] In an embodiment, the mass percentage of the thiol monomer in the polymer monomer is 0-65%. Alternatively, the mass percentage of the thiol monomer in the polymer monomer is any one of 0, 10%, 20%, 30%, 40%, 50%, 60%, 65%, or a range between any two of them. In this embodiment, if the content of the thiol monomer is too high, it is easy to cause the increase of the thiol monomer residue, and then increase the side reaction between the thiol monomer and the electrode, causing the battery to produce gas and the capacity to be damaged; if the content of the thiol monomer is too low, the effect of reducing the amount of thioether monomer residue is not ideal.

[0061] In an embodiment, the electrolyte further comprises an initiator and / or an additive.

[0062] In an embodiment, the organic solvent comprises 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.

[0063] In an embodiment, the lithium salt comprises at least one of lithium nitrate, lithium hexafluorophosphate, lithium perchlorate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium bis(aceto)borate, lithium tetrafluoroborate, lithium difluorophosphate.

[0064] In an embodiment, the initiator comprises at least one of azobisisobutyronitrile, azobisisopentyl nitrile, azobisisoheptyl nitrile, azobisdimethyl carbonate, di-2-methoxyethyl azodicarboxylate, di-tert-butyl azodicarboxylate, diisopropyl azodicarboxylate, dibenzyl azodicarboxylate, dimethyl azobisbutyrate, dimethyl azobenzene-4,4'-dicarboxylate, dibenzyl azodicarboxylate, azobisacyl dipiperidine, azobiscarbonyl dimorpholine, azodicarboxamide, azobenzene, 4,4-azopyridine, 4,4'-azobisdiethyl benzoate, 4-methyl 4-dimethylaminoazobenzene, 3,3-dimethylazobenzene, phenylazopropionitrile, azotert-butane, methyl red, methyl orange, aurin orange O, tert-butyl ketone peroxide, cyclohexanone peroxide, dimethylsulfonyl peroxide, tert-butyl benzene peroxide, tert-butyl isopropyl carbonate peroxide, 2-butyronitrile peroxide, dilauryl peroxide, benzoyl peroxide, lithium persulfate, lithium monopersulfate.

[0065] In an embodiment, the additive includes at least one of vinylene carbonate, fluoroethylene carbonate, triethyl phosphite, 1,3-propane sultone, ethylene sulfite, 1,3,2-dioxazolothiophene-2,2-dioxide, 1,4-butane sultone, phenyl methanesulfonate, hexanedinitrile, 3-methoxypropanenitrile, hexane-1,3,6-trinitrile, ethyleneglycol bis(propionitrile) ether, hexamethyldisilazane, trimethylsilyl diethylamine, or the like.

[0066] In an embodiment, the mass percentage of the organic solvent in the electrolyte is 30%-80%. Alternatively, the mass percentage of the organic solvent in the electrolyte is any one of 30%, 40%, 50%, 60%, 70%, 80%, or a range between any two of them.

[0067] In an embodiment, the mass percentage of the lithium salt in the electrolyte is 5%-20%. Alternatively, the mass percentage of the lithium salt in the electrolyte is any one of 5%, 8%, 10%, 14%, 18%, 20%, or a range between any two of them.

[0068] In an embodiment, the mass percentage of the initiator in the electrolyte is 0.01%-3%. Alternatively, the mass percentage of the initiator in the electrolyte is any one of 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or a range between any two of them.

[0069] In an embodiment, the mass percentage of the additive in the electrolyte is 2%-30%. Alternatively, the mass percentage of the additive in the electrolyte is any one of 2%, 5%, 10%, 15%, 20%, 25%, 30%, or a range between any two of them.

[0070] The application also provides an electrolyte prepared from the electrolyte described above.

[0071] In the embodiment, the solid-state polymer in the electrolyte contains a disulfide bond, which has dynamic reversibility and can reform a solid-state polymer interface protective layer at the crack of the solid electrolyte interface film when the solid electrolyte interface film on the surface of the positive material particles and the negative material particles is broken, thereby effectively repairing the solid electrolyte interface film and improving the cycle performance and electrochemical performance of the battery.

[0072] The application also provides a preparation method of an electrolyte, including the following steps:

[0073] S1, providing the electrolyte as described above;

[0074] S2, injecting the electrolyte into an electric core, standing, heating and curing to obtain an electrolyte.

[0075] In an embodiment, the method for preparing the electrolyte comprises the following steps:

[0076] The formula amount of organic solvent, lithium salt, polymer monomer and other raw materials are mixed to obtain the electrolyte.

[0077] In an embodiment, the other raw materials further comprise formula amount of initiator and / or additive.

[0078] In an embodiment, the mixing can be carried out in an argon atmosphere, a nitrogen atmosphere or a dry air atmosphere, which is not limited in the application.

[0079] In an embodiment, the temperature of mixing is 20-30℃, and / or the time of mixing is 0.5-3h. Alternatively, the temperature of mixing can be any one of 20℃, 22℃, 24℃, 26℃, 28℃, 30℃ or a range between any two of them; the time of mixing can be any one of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h or a range between any two of them.

[0080] In an embodiment, the temperature of standing is 20-35℃, and / or the time of standing is 24-72h. Alternatively, the temperature of standing can be any one of 20℃, 22℃, 24℃, 26℃, 28℃, 30℃, 35℃ or a range between any two of them; the time of standing can be any one of 24h, 30h, 35h, 40h, 50h, 60h, 70h, 72h or a range between any two of them.

[0081] In an embodiment, the temperature of heating and curing is 45-120℃, and / or the time of heating and curing is 8-60h. Alternatively, the temperature of heating and curing can be any one of 45℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃ or a range between any two of them; the time of heating and curing can be any one of 8h, 10h, 20h, 30h, 40h, 50h, 60h or a range between any two of them.

[0082] The application also provides a lithium ion battery, which comprises the electrolyte as described above or is prepared by the method as described above.

[0083] In the embodiment, the type of lithium ion battery is not limited, and the lithium ion battery can be one of ternary soft package battery, ternary steel shell battery, lithium cobaltate soft package battery and lithium cobaltate steel shell battery.

[0084] The above scheme is further described in combination with specific embodiments, and the preferred embodiments of the application are described in detail as follows:

[0085] Embodiment 1

[0086] The embodiment provides an electrolyte, which comprises a lithium salt, an organic solvent, an additive, an initiator and a polymer monomer;

[0087] The lithium salt is lithium hexafluorophosphate, and the mass percentage of the lithium salt in the electrolyte is 10.6 %;

[0088] The organic solvent is composed of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate, the volume ratio of the ethylene carbonate, the methyl ethyl carbonate and the dimethyl carbonate is 1:1:1, and the mass percentage of the organic solvent in the electrolyte is 68 %;

[0089] The additive is composed of vinylene carbonate and 1,3-propane sultone, and the mass percentage of the additive in the electrolyte is 3 %;

[0090] The initiator is azobisisobutyronitrile, and the mass percentage of the initiator in the electrolyte is 0.4 %;

[0091] The polymer monomer is composed of diallyl disulfide and pentaerythritol tetraacrylate, the mass percentage of the diallyl disulfide in the polymer monomer is 30 %, the mass percentage of the pentaerythritol tetraacrylate in the polymer monomer is 70 %, and the mass percentage of the polymer monomer in the electrolyte is 18 %.

[0092] The embodiment further provides a preparation method of a lithium battery.

[0093] (1) A slurry is prepared by mixing graphite as a negative electrode material, acetylene black as a conductive agent and sodium carboxymethyl cellulose and butadiene-styrene rubber as binders at a mass ratio of 97:1:0.5:1.5, and the slurry is coated on a copper foil current collector, vacuum dried, and a negative electrode sheet is prepared; a slurry is prepared by mixing NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 ) as a positive electrode material, acetylene black as a conductive agent and polyvinylidene fluoride as a binder at a mass ratio of 96:2:2, and the slurry is coated on an aluminum foil current collector, dried, and a positive electrode sheet is prepared; the positive electrode sheet, the negative electrode sheet and a separator are assembled, and a cell is obtained.

[0094] (2) The lithium salt, the organic solvent, the additive, the initiator and the polymer monomer are mixed at an ambient temperature of 20 DEG C under an argon atmosphere, and an electrolyte is obtained.

[0095] (3) The electrolyte precursor is injected into the cell, vacuum packaged, left to stand, heated and cured, and an electrolyte is obtained, wherein the vacuum degree of the vacuum packaging is -90 kPa, the temperature of the left to stand is 30 DEG C, the time of the left to stand is 30 h, the temperature of the heating and curing is 70 DEG C, and the time of the heating and curing is 32 h.

[0096] (4) cooling the cell containing electrolyte to room temperature, formation, and discharging to obtain a lithium ion battery.

[0097] Example 2

[0098] The difference between Example 2 and Example 1 is that:

[0099] The polymer monomer is composed of divinyl disulfide and pentaerythritol tetraacrylate, the mass percentage of divinyl disulfide in the polymer monomer is 30%, the mass percentage of pentaerythritol tetraacrylate in the polymer monomer is 70%, and the rest is the same as Example 1.

[0100] Example 3

[0101] The difference between Example 3 and Example 1 is that:

[0102] The polymer monomer is composed of divinyl disulfide and pentaerythritol tetraacrylate, the mass percentage of divinyl disulfide in the polymer monomer is 30%, the mass percentage of pentaerythritol tetraacrylate in the polymer monomer is 70%, and the rest is the same as Example 1.

[0103] Example 4

[0104] The difference between Example 4 and Example 1 is that:

[0105] The polymer monomer is composed of divinyl disulfide, pentaerythritol tetraacrylate and 1,4-butanedithiol, the mass percentage of divinyl disulfide is 30%, the mass percentage of pentaerythritol tetraacrylate is 60%, and the mass percentage of 1,4-butanedithiol is 10%, based on the total mass of the polymer monomer, and the rest is the same as Example 1.

[0106] Example 5

[0107] The difference between Example 5 and Example 1 is that:

[0108] The polymer monomer is composed of divinyl disulfide, pentaerythritol tetraacrylate and 1,4-butanedithiol, the mass percentage of divinyl disulfide is 30%, the mass percentage of pentaerythritol tetraacrylate is 60%, and the mass percentage of 1,4-butanedithiol is 10%, based on the total mass of the polymer monomer, and the rest is the same as Example 1.

[0109] Example 6

[0110] The difference between Example 6 and Example 1 is that:

[0111] The mass percentage of the polymer monomer in the electrolyte is 2%, and the rest is the same as Example 1.

[0112] Example 7

[0113] Example 7 differs from Example 1 in that:

[0114] The mass percentage of the polymer monomer in the electrolyte is 34%, and the rest is the same as Example 1.

[0115] Example 8

[0116] Example 8 differs from Example 1 in that:

[0117] The polymer monomer is composed of diallyl disulfide and pentaerythritol tetraacrylate, the mass percentage of diallyl disulfide is 15% based on the total mass of the polymer monomer, the mass percentage of pentaerythritol tetraacrylate is 85% based on the total mass of the polymer monomer, and the rest is the same as Example 1.

[0118] Example 9

[0119] Example 9 differs from Example 1 in that:

[0120] The polymer monomer is composed of diallyl disulfide and pentaerythritol tetraacrylate, the mass percentage of diallyl disulfide is 65% based on the total mass of the polymer monomer, the mass percentage of pentaerythritol tetraacrylate is 35% based on the total mass of the polymer monomer, and the rest is the same as Example 1.

[0121] Example 10

[0122] Example 10 differs from Example 1 in that:

[0123] The polymer monomer is composed of diallyl disulfide and pentaerythritol tetraacrylate, the mass percentage of diallyl disulfide in the polymer monomer is 75%, the mass percentage of pentaerythritol tetraacrylate in the polymer monomer is 25%, and the rest is the same as Example 1.

[0124] Comparative Example 1

[0125] Comparative Example 1 differs from Example 1 in that:

[0126] The polymer monomer is composed of diallyl disulfide, the mass percentage of diallyl disulfide in the polymer monomer is 100%, and the rest is the same as Example 1.

[0127] Comparative Example 2

[0128] Comparative Example 2 differs from Example 1 in that:

[0129] The polymer monomer is composed of pentaerythritol tetraacrylate, the mass percentage of pentaerythritol tetraacrylate in the polymer monomer is 100%, and the rest is the same as Example 1.

[0130] Comparative Example 3

[0131] The difference between Comparative Example 3 and Example 1 is that:

[0132] The polymer monomer is composed of diphenyl disulfide and pentaerythritol tetraacrylate, the mass percentage of diphenyl disulfide in the polymer monomer is 30%, the mass percentage of pentaerythritol tetraacrylate in the polymer monomer is 70%, and the rest is the same as Example 1.

[0133] Test method

[0134] The lithium ion batteries obtained from Examples 1-10 and Comparative Examples 1-3 were tested for performance, and the specific method was as follows:

[0135] (1) Cycle performance: The lithium ion battery was tested at a current density of 1C at 25°C, and the full battery test was performed by constant current and constant voltage charging and discharging, and the charge and discharge voltage window was 2.8V-4.2V.

[0136] (2) Rate performance: The lithium ion battery was tested at a current density of 1C by constant current and constant voltage charging, and at a current density of 3C by constant current and constant voltage discharging, and the full battery test was performed, and the charge and discharge voltage window was 2.8V-4.2V.

[0137] (3) 130°C thermal abuse pass rate: The lithium ion battery was heated from room temperature (25°C) to 130°C at a rate of 5°C / min, and then kept at 130°C for 1h, and no fire or explosion occurred, which was determined to pass the test.

[0138] The test results are shown in Table 1 below:

[0139] Table 1

[0140]

[0141] From the test results of the above examples and comparative examples, it can be seen that the lithium ion batteries prepared in Examples 1-10 have good rate performance, excellent cycle performance and high 130°C thermal abuse pass rate, which shows that the sulfide monomer of the present application can introduce disulfide bonds in the generated solid polymer, the disulfide bonds have dynamic reversibility, can reform the solid polymer interface protection layer at the crack of the solid electrolyte interface film, and then effectively repair the solid electrolyte interface film, reduce the contact between the positive and negative materials and the organic solvent, lithium salt and other components in the battery, reduce the generation of side reactions and gas in the battery, improve the thermal runaway temperature of the battery, and improve the cycle performance and electrochemical performance of the battery.

[0142] The comparison of examples 1 to 7 and comparative examples 1, 2 shows that the electrolyte of examples 1 to 7 contains both acrylate monomers and sulfide monomers, and the reactivity between the acrylate monomers and the sulfide monomers is high, which can reduce the residual amount of polymer monomers, reduce the side reaction between the residual polymer monomers and the electrode active material, and reduce the crosstalk reaction of the residual polymer monomers under the electric field; at the same time, the solid electrolyte interface film is effectively self-repaired, and the cycle performance and electrochemical performance of the battery are improved.

[0143] The comparison of examples 1 to 10 and comparative example 3 shows that the sulfide monomers in the electrolyte of examples 1 to 10 contain carbon-carbon double bonds, and the sulfide monomers containing carbon-carbon double bonds have high reactivity, which can improve the conversion rate of the reaction between the sulfide monomers and the acrylate monomers, reduce the reaction temperature, reduce the residual 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.

[0144] The comparison of examples 1 to 3 and examples 4, 5 shows that the addition of mercaptan monomers in the electrolyte can further consume sulfide monomers and effectively reduce the residual of polymer monomers; at the same time, the mercaptan monomers can exchange with the disulfide bond on the solid polymer to induce the folding of part of the solid polymer, and the folded solid polymer can coat a layer of nanometer film on the surface of the positive and negative material particles, which is beneficial to reduce the occurrence of side reactions and gas generation in the battery, reduce the loss of battery capacity, and further improve the electrochemical performance and safety performance of the battery.

[0145] The comparison of examples 1 to 3 and example 10 shows that controlling the content of acrylate monomers and sulfide monomers within a proper range can further ensure the electrochemical performance and safety performance of the battery.

[0146] The above describes the embodiments of the present application in detail, and the principles and implementation modes of the present application are described by applying specific examples; the above examples are only used to help understand the method and core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed, and the above description should not be understood as a limitation of the present application.

Claims

1. An electrolyte, characterized by, Comprise: an organic solvent, a lithium salt and a polymer monomer; wherein the polymer monomer comprises an acrylate monomer, a sulfide monomer and a thiol monomer, the acrylate monomer and the sulfide monomer can undergo a polymerization reaction to generate a solid polymer; the structure of the sulfide monomer is shown as Formula I: （I） wherein n is selected from 2 or 3; y and z are each independently selected from 0, 1, 2, 3 or 4; the substituents R1-R6 are each independently selected from a hydrogen atom, a C1-C18 substituted or unsubstituted linear or branched alkyl group and / or a C1-C10 substituted or unsubstituted linear or branched alkoxy group; the thiol monomer comprises at least one of 1,3-ethanedithiol, benzene thiol, dodecanethiol, 1,4-butanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol, 1,5-pentanedithiol and 2,3-butanedithiol; the mass percentage of the acrylate monomer in the polymer monomer is 30%-85%, the mass percentage of the sulfide monomer in the polymer monomer is 15%-65%, the mass percentage of the thiol monomer in the polymer monomer is 10%-65%, and the mass percentage of the acrylate monomer, the sulfide monomer and the thiol monomer in the polymer monomer is 100%.

2. The electrolyte of claim 1, wherein: the sulfide monomer comprises at least one of divinyl disulfide, diallyl disulfide and diallyl trisulfide; and / or the acrylate monomer comprises at least one of pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, methyl methacrylate, butyl methacrylate, polyethylene glycol dimethacrylate, polytriethylene glycol dimethacrylate and cyanoacrylate.

3. The electrolyte of claim 1, wherein: the mass percentage of the polymer monomer in the electrolyte is 2%-34%.

4. The electrolyte of any one of claims 1-3, wherein: the electrolyte further comprises an initiator and / or an additive.

5. The electrolyte of claim 4, wherein: the organic solvent comprises 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 comprises at least one of lithium nitrate, lithium hexafluorophosphate, lithium perchlorate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium bis(oxalato)borate, lithium tetrafluoroborate, lithium difluorophosphate; and / or The initiator includes at least one of azobisisobutyronitrile, azobisisopentanitrile, azobisisoheptylnitrile, diethyl azodicarboxylate, di-2-methoxyethyl azodicarboxylate, di-tert-butyl azodicarboxylate, diisopropyl azodicarboxylate, dibenzyl azodicarboxylate, dimethyl azobisbutanoate, dimethyl azobenzene-4,4'-dicarboxylate, dibenzyl azodicarboxylate, azobisdimethylpiperidine, azobiscarbonyldimorpholine, azodicarboxamide, azobenzene, 4,4-azopyridine, diethyl 4,4'-azobenzenedicarboxylate, 4-methyl 4-dimethylaminoazobenzene, 3,3-dimethylazobenzene, phenylazopropanedinitrile, azotert-butane, methyl red, methyl orange, aurin orange O, tert-butyl ketone peroxide, cyclohexanone peroxide, dimethylsulfonyl peroxide, tert-butyl benzene peroxide, tert-butyl isopropyl peroxide carbonate, 2-butyronitrile peroxide, dilauryl peroxide, benzoyl peroxide, lithium peroxide, lithium monopersulfate; and / or The additive includes at least one of vinylene carbonate, fluoroethylene carbonate, triethyl phosphite, 1,3-propanesultone, ethylene sulfite, 1,3,2-dioxazolothiophene-2,2-dioxide, 1,4-butanesultone, phenyl methanesulfonate, hexanedinitrile, 3-methoxypropanenitrile, hexane-1,3,6-trinitrile, ethylene glycol bis(propionitrile) ether, hexamethyldisilazane, trimethylsilyl diethylamine; and / or The mass percentage of the organic solvent in the electrolyte is 30%-80%; and / or The mass percentage of the lithium salt in the electrolyte is 5%-20%; And / or The mass percentage of the initiator in the electrolyte is 0.01%-3%; and / or The mass percentage of the additive in the electrolyte is 2%-30%.

6. An electrolyte characterized in that, The electrolyte is prepared from the electrolyte of any one of claims 1 to 5.

7. A method of preparing an electrolyte, characterized by, The method comprises the following steps: Providing the electrolyte of any one of claims 1 to 5; Injecting the electrolyte into an electric core, standing, heating and curing to obtain the electrolyte.

8. The preparation method of claim 7, wherein The preparation method of the electrolyte comprises the following steps: mixing the formula amount of organic solvent, lithium salt, polymer monomer and other raw materials to obtain the electrolyte.

9. The preparation method of claim 8, wherein The other raw materials further include formula amount of initiator and / or additive; 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°C, and / or the mixing time is 0.5-3h; and / or The standing temperature is 20-35°C, and / or the standing time is 24-72h; and / or The heating and curing temperature is 45-120°C, and / or the heating and curing time is 8-60h.

10. A lithium-ion battery, characterized by, The electrolyte of claim 6 or prepared by the method of any one of claims 7 to 9.

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