Gel polymer electrolyte composition, gel polymer electrolyte, lithium metal battery and capacity repairing method thereof

Abstract

The invention provides a gel polymer electrolyte composition, a gel polymer electrolyte, a lithium metal battery and a capacity repairing method of the lithium metal battery. The gel polymer electrolyte composition comprises the following components in percentage by mass: 1-10% of polymeric monomer, 60-85% of organic solvent and the balance of lithium salt, wherein the organic solvent at least contains a cyclic fluorocarbonate compound, a fluorine-free ether compound and a fluorinated ether compound, and the polymeric monomer at least contains a fluorine-free acrylate monomer and a fluorinated ester monomer. The gel polymer electrolyte formed by the gel polymer electrolyte composition provided by the invention is helpful for inhibiting the growth of lithium dendrites, forming stable SEI films on the positive electrode and the negative electrode of the battery, and reducing side reactions, thereby being helpful for improving the cycling stability and safety of the lithium metal battery at normal temperature and high temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and more particularly, to a gel polymer electrolyte composition, a gel polymer electrolyte, a lithium metal battery, and a method for restoring its capacity. Background Art

[0002] With the popularization of consumer electronic products such as laptop computers, mobile phones, handheld game consoles, tablet computers, mobile power supplies, and drones, people's requirements for the electrochemical devices (e.g., batteries) therein are becoming increasingly stringent. For example, people not only require the battery to be lightweight, but also require the battery to have a short charging time and a long working life. Among various batteries, lithium metal batteries have attracted much attention in the research and development field due to their highest energy density. Currently, how to improve the cycling performance of lithium metal batteries has become the focus of research and development in the field of lithium metal batteries.

[0003] The specific capacity of lithium metal as the negative electrode can reach 3860 mAh / g, which is more than ten times higher than the theoretical specific capacity of 372 mAh / g of current graphite. However, lithium metal has the lowest chemical potential (-3.04 V) and very high reactivity, and will react with the electrolyte in the battery, consuming lithium, increasing the impedance of the battery, and finally leading to cycling failure. Therefore, although the energy density can be greatly improved when lithium metal is used as the negative electrode material of the battery, the cycle life will also be sharply shortened.

[0004] There are three important directions for improving the cycling performance of lithium metal batteries: 1. Form a stable solid electrolyte interface (SEI) on the surface of the lithium metal negative electrode. A uniform and stable SEI can reduce the reactivity between lithium metal and the electrolyte, and can also inhibit the formation of lithium dendrites, effectively improving the cycling performance of the battery. 2. Develop an electrolyte with lower reactivity with the lithium metal negative electrode. The electrolyte can be liquid, gel, or all-solid-state. After the reactivity between the electrolyte and lithium metal is reduced, the cycling Coulomb efficiency and cycle life of the battery can be effectively improved. 3. Use a suitable capacity restoration mechanism to restore the capacity of a lithium metal battery that has shown a trend of cycling decay. However, the existing technologies still have limitations in improving the cycling performance of lithium metal batteries. Summary of the Invention

[0005] The main object of the present invention is to provide a gel polymer electrolyte composition, a gel polymer electrolyte, a lithium metal battery, and a method for restoring its capacity, so as to solve the problem of poor cycling performance of lithium metal batteries in the prior art.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided a gel polymer electrolyte composition. By mass fraction, the gel polymer electrolyte composition includes: 1 to 10% of a polymerizable monomer, 60 to 85% of an organic solvent, and the balance being a lithium salt; wherein, the organic solvent contains at least a cyclic fluorinated carbonate compound, a fluorine-free ether compound, and a fluorinated ether compound, and the polymerizable monomer contains at least a fluorine-free acrylate monomer and a fluorinated ester monomer.

[0007] Further, the above-mentioned organic solvent is a combination of a cyclic fluorinated carbonate compound, a fluorine-free ether compound, and a fluorinated ether compound, and the mass ratio of the cyclic fluorinated carbonate compound, the fluorine-free ether compound, and the fluorinated ether compound is (1 to 40):(1 to 70):(1 to 40).

[0008] Further, the structure of the above-mentioned cyclic fluorinated carbonate compound is wherein, R 1 , R 2 , R 3 and R 4 each independently selected from hydrogen, fluorine, fluorine-substituted or unsubstituted C 1 -C 12 alkyl, fluorine-substituted or unsubstituted C 3 -C 12 cycloalkyl, fluorine-substituted or unsubstituted C 2 -C 12 alkenyl, and fluorine-substituted or unsubstituted C 3 -C 12 heterocyclic group, and at least one of R 1 , R 2 , R 3 and R 4 is selected from fluorine, fluorine-substituted C 1 -C 12 alkyl, fluorine-substituted C 3 -C 12 cycloalkyl, fluorine-substituted C 2 -C 12 alkenyl and fluorine-substituted C 3 -C 12 heterocyclic group; preferably, R 1 , R 2 , R 3 and R 4 each independently selected from hydrogen, fluorine, fluorine-substituted or unsubstituted C 1 -C 6 alkyl, fluorine-substituted or unsubstituted C 3 -C 6 cycloalkyl, fluorine-substituted or unsubstituted C 2 -C6 an alkenyl group, and a fluoro-substituted or unsubstituted C 3 to C 6 heterocyclic group, and at least one of R 1 , R 2 , R 3 and R 4 is selected from any one of fluorine, a fluoro-substituted C 1 to C 6 alkyl group, a fluoro-substituted C 3 to C 6 cycloalkyl group, a fluoro-substituted C 2 to C 6 alkenyl group, and a fluoro-substituted C 3 to C 6 heterocyclic group; more preferably, R 1 , R 2 , R 3 and R 4 are each independently selected from hydrogen, fluorine, and any one of fluoro-substituted or unsubstituted C 1 to C 3 alkyl group, and at least one of R 1 , R 2 , R 3 and R 4 is selected from fluorine and any one of fluoro-substituted C 1 to C 3 alkyl group; most preferably, R 1 , R 2 , R 3 and R 4 are each independently hydrogen or fluorine, and one of R 1 , R 2 , R 3 and R 4 is fluorine.

[0009] Furthermore, the structural formula of the above-mentioned fluorine-free ether compound is wherein, R 5 and R 6 are each independently selected from any one of C 1 to C 10 alkyl group; preferably, R 5 and R 6 are each independently selected from any one of C 1 to C 6 alkyl group; more preferably, R 5 and R 6 are each independently selected from any one of C 1 to C 3 alkyl group; most preferably, R 5 and R 6 are each independently methyl.

[0010] Further, the structure of the above-mentioned fluoroether compound is wherein, R 7 and R 8 each independently selected from C 1 to C 10 haloalkyl and C 2 to C 10 any one of haloalkenyl; preferably, R 7 and R 8 each independently selected from C 1 to C 6 haloalkyl and C 2 to C 6 any one of haloalkenyl; more preferably, R 7 and R 8 each independently selected from C 1 to C 3 any one of haloalkyl; most preferably, R 7 and R 8 each independently is

[0011] Further, the above polymerization monomer is a combination of a non-fluorinated acrylate monomer and a fluoroester monomer, and the mass ratio of the non-fluorinated acrylate monomer to the fluoroester monomer is 1:(0.1 - 0.5); more preferably, the non-fluorinated acrylate monomer is selected from any one or more of ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, ethyl acetoacetate methacrylate, methyl methacrylate, ethyl acrylate, and decyl acrylate; and / or, the fluoroester monomer is selected from any one or more of trifluoroethyl methacrylate, allyl trifluoroacetate, fluorinated ethylene carbonate, hexafluorobutyl methacrylate, hexafluoroisobutyl methacrylate, 1H,1H-perfluorooctyl methacrylate, methyl 2-trifluoromethylacrylate, methyl 2-fluoroacrylate, and pentafluorophenyl acrylate; most preferably, the non-fluorinated acrylate monomer is ethoxylated trimethylolpropane triacrylate; and / or, the fluoroester monomer is trifluoroethyl methacrylate.

[0012] Further, the above gel polymer electrolyte composition further includes 0.01-10% of an additive. Preferably, the additive is selected from any one or more of lithium-containing compounds, ester compounds, thiophene compounds, acid anhydride compounds, amide compounds, cyclic ether compounds, nitrile compounds, and cyano-containing compounds. Further preferably, the lithium-containing compound is selected from any one or more of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium nitrate. And / or, the ester compound is selected from any one or more of fluoroethylene carbonate, vinylene ethylene carbonate, methylene methanedisulfonate, 4-trifluoromethyl ethylene carbonate, fluoroethylene carbonate, ethylene sulfite, vinylene carbonate, propylene sulfite, allyl-1,3-sultone, and bis(trimethylsilyl) sulfate. And / or, the thiophene compound is 1,3,2-dioxathiolane-2,2-dioxide. And / or, the acid anhydride compound is succinic anhydride. And / or, the amide compound is N-methyl, butylpyrrolidinium bis(trifluoromethylsulfonyl)imide and / or N-methyl, propylpiperidinium bis(trifluoromethylsulfonyl)imide. And / or, the cyclic ether compound is 1,3-dioxane and / or 1,4-dioxane. And / or, the nitrile compound is adiponitrile and / or fumaronitrile. And / or, the cyano-containing compound is selected from any one or more of 1,2-bis(cyanoethoxy)ethane, 1,3,5-pentanetricarbonitrile, and 1,2,3-tris(2-cyanoethoxy)propane. Most preferably, the additive is methylene methanedisulfonate. And / or, the lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluorophosphate.

[0013] According to another aspect of the present invention, there is provided a gel polymer electrolyte, which is prepared by subjecting the aforementioned gel polymer electrolyte composition to a polymerization reaction.

[0014] According to still another aspect of the present invention, there is provided a lithium metal battery, including a positive electrode sheet, a gel polymer electrolyte, and a lithium metal negative electrode sheet, wherein the gel polymer electrolyte is the aforementioned gel polymer electrolyte.

[0015] According to still another aspect of the present invention, there is provided a method for restoring the capacity of the aforementioned lithium metal battery, the capacity restoration method including: testing the capacity retention rate H of the lithium metal battery, and when 85% ≤ H ≤ 90%, allowing the lithium metal battery to stand at 45-50 °C for 1-2 h and cycle 5-10 times to end the capacity restoration.

[0016] Applying the technical solution of the present application, the presence of the polymerizable monomer helps to form a stable and uniform copolymer framework during the subsequent polymerization reaction. This framework not only provides physical structure support but also can effectively restrict the free flow of the electrolyte, thereby inhibiting the formation of lithium dendrites, reducing the risk of internal short circuits, and improving the safety of the battery. The main role of the acrylate monomer without fluorine in the polymerizable monomer is to form the gel polymer skeleton. The addition of the fluorinated ester monomer helps to improve the oxidation resistance of the skeleton at the positive electrode and can also form a LiF-rich SEI film at the negative electrode, thus contributing to improving the long-cycle stability of the lithium metal battery. An excessively low proportion of the polymerizable monomer may result in insufficient mechanical strength of the gel polymer electrolyte, while an excessively high proportion may increase the viscosity of the gel and affect the mobility of lithium ions. Controlling the proportion of the polymerizable monomer within the above range helps to make the formed gel polymer electrolyte have appropriate mechanical strength and good ionic conductivity, balancing the kinetic performance and chemical stability. The presence of cyclic fluorinated carbonate compounds and fluorinated ether compounds in the organic solvent helps to form an SEI film with LiF components on the surface of the negative electrode, and this organic solvent is more oxidation-resistant on the positive electrode side, which is beneficial to improving the cycle performance of the lithium metal battery. Moreover, the cyclic fluorinated carbonate compound has good solubility in the lithium salt and can also form an organic polymer SEI containing C and O on the surface of the negative electrode. After combining with inorganic LiF and Li 3 N, it can exhibit better stability performance. The cyclic fluorinated carbonate compound has a relatively high viscosity, while the fluorine-free ether compound and the fluorinated ether compound have relatively low viscosities. The presence of the fluorine-free ether compound helps to regulate the viscosity of the electrolyte on the one hand and helps to reduce the reaction activity of the electrolyte at the negative electrode on the other hand, thus being beneficial to improving the long-cycle performance of the lithium metal battery. In addition to helping to regulate the viscosity of the electrolyte, the fluorinated ether compound has good stability towards the lithium metal negative electrode, is difficult to react with the active lithium metal, and can form a tight positive electrode protective film at the positive electrode. Controlling the mass proportion of the organic solvent within the above range helps to form stable SEI films on the positive and negative electrodes of the battery, thus contributing to improving the cycle stability of the lithium metal battery. The gel polymer electrolyte formed from the gel polymer electrolyte composition of the present application helps to inhibit the growth of lithium dendrites, forms stable SEI films on the positive and negative electrodes of the battery, and reduces side reactions, thus contributing to improving the cycle stability performance and safety of the lithium metal battery at normal temperature and high temperature. Detailed Embodiments

[0017] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0018] As analyzed in the background art of this application, the lithium metal battery in the prior art has the problem of poor cycling performance. To solve this problem, this application provides a gel polymer electrolyte composition, a gel polymer electrolyte, a lithium metal battery, and a method for restoring its capacity.

[0019] In a typical embodiment of this application, a gel polymer electrolyte composition is provided. In terms of mass fraction, the gel polymer electrolyte composition includes: 1-10% of polymerizable monomers, 60-85% of organic solvents, and the balance of lithium salts; wherein, the organic solvents contain at least cyclic fluorinated carbonate compounds, non-fluorinated ether compounds, and fluorinated ether compounds, and the polymerizable monomers contain at least non-fluorinated acrylate monomers and fluorinated ester monomers.

[0020] The presence of polymerizable monomers helps to form a stable and uniform copolymer framework during the subsequent polymerization reaction. This framework not only provides physical structure support but also effectively restricts the free flow of the electrolyte, thereby inhibiting the formation of lithium dendrites, reducing the risk of internal short circuits, and improving the safety of the battery. The main role of the non-fluorinated acrylate monomers in the polymerizable monomers is to form the gel polymer skeleton. The addition of fluorinated ester monomers helps to improve the oxidation resistance of the skeleton at the positive electrode and can also form a LiF-rich SEI film at the negative electrode, thus contributing to improving the long-cycle stability of the lithium metal battery. Too low a proportion of polymerizable monomers may result in insufficient mechanical strength of the gel polymer electrolyte, while too high a proportion may increase the viscosity of the gel and affect the mobility of lithium ions. Controlling the proportion of polymerizable monomers within the above range helps to make the formed gel polymer electrolyte have appropriate mechanical strength and good ionic conductivity, balancing kinetic performance and chemical stability. The presence of cyclic fluorinated carbonate compounds and fluorinated ether compounds in the organic solvents helps to form a SEI film with LiF components on the surface of the negative electrode, and this organic solvent is more oxidation-resistant on the positive electrode side, which is beneficial to improving the cycling performance of the lithium metal battery. Moreover, cyclic fluorinated carbonate compounds have good solubility in lithium salts, and they can also form an organic polymer SEI containing C and O on the surface of the negative electrode, together with inorganic LiF, Li 3After N binding, better stability performance can be exerted. Cyclic fluorinated carbonate compounds have relatively high viscosities, while fluorine-free ether compounds and fluorinated ether compounds have relatively low viscosities. The presence of fluorine-free ether compounds helps to regulate the viscosity of the electrolyte on the one hand and reduce the reaction activity of the electrolyte at the negative electrode on the other hand, thus contributing to improving the long-cycle performance of lithium metal batteries. In addition to helping to regulate the viscosity of the electrolyte, fluorinated ether compounds have good stability towards lithium metal anodes, are difficult to react with active lithium metal, and can form a tight positive electrode protective film at the positive electrode. Controlling the mass ratio of the organic solvent within the above range helps to form a stable SEI film on the positive and negative electrodes of the battery, thus contributing to improving the cycle stability of the lithium metal battery. The gel polymer electrolyte formed from the gel polymer electrolyte composition of the present application helps to inhibit the growth of lithium dendrites, form a stable SEI film on the positive and negative electrodes of the battery, reduce side reactions, and thus contribute to improving the cycle stability performance and safety of the lithium metal battery at room temperature and high temperature.

[0021] It should be noted that the compounds of the present application are all known compounds in the prior art and can be commercially purchased.

[0022] In one embodiment of the present application, the mass ratio of the above-mentioned polymer monomer to the organic solvent is (3 - 5):(81 - 84), specifically it can be 3:84, 3:83, 4:83, 4:82, 5:81, and the range values between the two ratios.

[0023] The polymer monomer can form a moderately cross-linked three-dimensional network structure, namely a gel polymer framework, in the organic solvent. This framework can not only maintain good mechanical stability to prevent the penetration of lithium dendrites, but also not overly increase the viscosity of the electrolyte and affect the migration rate of lithium ions. Controlling the mass ratio of the polymer monomer to the organic solvent within the above range helps to keep the electrolyte at an appropriate viscosity, helps to improve the solubility of the lithium salt and the transport efficiency of lithium ions, and helps to promote the formation of a stable SEI film on the surfaces of the positive and negative electrodes of the electrolyte, thereby contributing to improving the cycle efficiency and stability of the lithium metal battery.

[0024] In one embodiment of the present application, the above-mentioned organic solvent is a combination of cyclic fluorinated carbonate compounds, fluorine-free ether compounds, and fluorinated ether compounds, and the mass ratio of the cyclic fluorinated carbonate compounds, fluorine-free ether compounds, and fluorinated ether compounds is (1 - 40):(1 - 70):(1 - 40), preferably (13 - 19):(50 - 52):(14 - 18).

[0025] Cyclic fluorinated carbonates have good solubility for lithium salts and can form a stable SEI film on the surface of the negative electrode. However, cyclic fluorinated carbonates have a relatively high viscosity and cannot be added in too large amounts, otherwise it will affect the viscosity of the electrolyte and thus the kinetic performance of the battery. Moreover, at high voltages, cyclic fluorinated carbonates will undergo ring-opening reactions to produce carbon dioxide, which affects the stability of the positive electrode and causes gas generation in the battery. When used in combination with fluorine-free ether compounds and fluorinated ether compounds, it can adjust the viscosity of the electrolyte, and also helps to reduce the reaction activity of the electrolyte at the negative electrode, which is beneficial to the long cycle of the battery. In addition, fluorinated ether compounds can form a tight positive electrode protective film on the positive electrode. Controlling the mass ratio of cyclic fluorinated carbonates, fluorine-free ether compounds and fluorinated ether compounds within the above range helps to improve the mutual synergistic effect among the three, thereby helping to form stable protective films on the surfaces of the positive and negative electrodes, improving the interfacial stability, and thus helping to improve the cycle stability of the lithium metal battery.

[0026] In order to further improve the solubility of cyclic fluorinated carbonates for lithium salts and the stability of the SEI film formed on the surface of the negative electrode, in one embodiment of the present application, the structure of the above cyclic fluorinated carbonate is preferably wherein, R 1 , R 2 , R 3 and R 4 each independently selected from hydrogen, fluorine, fluorine-substituted or unsubstituted C 1 ~C 12 alkyl, fluorine-substituted or unsubstituted C 3 ~C 12 cycloalkyl, fluorine-substituted or unsubstituted C 2 ~C 12 alkenyl and fluorine-substituted or unsubstituted C 3 ~C 12 heterocyclic group, and at least one of R 1 , R 2 , R 3 and R 4 is selected from fluorine, fluorine-substituted C 1 ~C 12 alkyl, fluorine-substituted C 3 ~C 12 cycloalkyl, fluorine-substituted C 2 ~C 12 alkenyl, and fluorine-substituted C 3 ~C 12 heterocyclic group; preferably, R 1 , R 2 , R 3 and R 4Each independently selected from hydrogen, fluorine, fluorine-substituted or unsubstituted C 1 ~C 6 alkyl, fluorine-substituted or unsubstituted C 3 ~C 6 cycloalkyl, fluorine-substituted or unsubstituted C 2 ~C 6 alkenyl, and fluorine-substituted or unsubstituted C 3 ~C 6 heterocyclic group, and at least one of R 1 , R 2 , R 3 and R 4 is selected from any one of fluorine, fluorine-substituted C 1 ~C 6 alkyl, fluorine-substituted C 3 ~C 6 cycloalkyl, fluorine-substituted C 2 ~C 6 alkenyl and fluorine-substituted C 3 ~C 6 heterocyclic group; further preferably, R 1 , R 2 , R 3 and R 4 are each independently selected from hydrogen, fluorine, and fluorine-substituted or unsubstituted C 1 ~C 3 alkyl, and at least one of R 1 , R 2 , R 3 and R 4 is selected from any one of fluorine and fluorine-substituted C 1 ~C 3 alkyl; most preferably, R 1 , R 2 , R 3 and R 4 are each independently hydrogen or fluorine, and one of R 1 , R 2 , R 3 and R 4 is fluorine.

[0027] In order to further reduce the viscosity of the fluorine-free ether compound and its reactivity on the surface of the negative electrode, in one embodiment of the present application, it is preferred that the structural formula of the above-mentioned fluorine-free ether compound is wherein, R 5 and R 6 are each independently selected from any one of C 1 ~C 10 alkyl; preferably, R 5 and R 6 are each independently selected from C1 ~C 6 any one of the alkyl groups; more preferably, R 5 and R 6 are each independently selected from C 1 ~C 3 any one of the alkyl groups; most preferably, R 5 and R 6 are each independently methyl.

[0028] In order to further reduce the reaction activity of the fluoroether compound on the surface of the lithium metal negative electrode and improve the stability of the protective film formed on the surface of the positive electrode, in one embodiment of the present application, the structure of the above-mentioned fluoroether compound is preferably wherein, R 7 and R 8 are each independently selected from C 1 ~C 10 haloalkyl and C 2 ~C 10 any one of the haloalkenyl groups; preferably, R 7 and R 8 are each independently selected from C 1 ~C 6 haloalkyl and C 2 ~C 6 any one of the haloalkenyl groups; more preferably, R 7 and R 8 are each independently selected from C 1 ~C 3 any one of the haloalkyl groups; most preferably, R 7 and R 8 are each independently

[0029] In one embodiment of the present application, the above-mentioned polymerization monomers are a combination of non-fluorinated acrylate monomers and fluorinated ester monomers, and the mass ratio of the non-fluorinated acrylate monomers to the fluorinated ester monomers is 1:(0.1 - 0.5), specifically, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, and the range values between the two ratios; further preferably, the non-fluorinated acrylate monomers are selected from any one or more of ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, ethyl acetoacetate methacrylate, methyl methacrylate, ethyl acrylate, and decyl acrylate; and / or, the fluorinated ester monomers are selected from any one or more of trifluoroethyl methacrylate, allyl trifluoroacetate, fluorinated ethylene carbonate, hexafluorobutyl methacrylate, hexafluoroisobutyl methacrylate, 1H,1H-perfluorooctyl methacrylate, methyl 2-trifluoromethylacrylate, methyl 2-fluoroacrylate, and pentafluorophenyl acrylate; most preferably, the non-fluorinated acrylate monomer is ethoxylated trimethylolpropane triacrylate; and / or, the fluorinated ester monomer is trifluoroethyl methacrylate.

[0030] Too high content of fluorinated ester monomers will affect the polymerization ability of non-fluorinated acrylate monomers, thereby reducing the ability of the polymer backbone to cage the electrolyte. Controlling the mass ratio of non-fluorinated acrylate monomers to fluorinated ester monomers within the above range helps to improve the ability of the polymer to cage the electrolyte while enhancing the oxidation resistance of the polymer.

[0031] In an embodiment of the present application, the above gel polymer electrolyte composition further comprises 0.01-10% of an additive. Preferably, the additive is selected from any one or more of lithium-containing compounds, ester compounds, thiophene compounds, anhydride compounds, amide compounds, cyclic ether compounds, nitrile compounds and cyano-containing compounds; More preferably, the lithium-containing compound is selected from any one or more of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate and lithium nitrate; And / or, the ester compound is selected from any one or more of vinyl fluorocarbonate, vinylene ethylene carbonate, methylene methanedisulfonate, 4-trifluoromethyl vinyl carbonate, vinyl fluorocarbonate, ethylene sulfite, vinylene carbonate, propylene sulfite, allyl-1,3-sultone and bis(trimethylsilyl) sulfate; And / or, the thiophene compound is 1,3,2-dioxazolothiophene-2,2-dioxide; And / or, the anhydride compound is succinic anhydride; And / or, the amide compound is N-methyl, butylpyrrolidinium bis(trifluoromethanesulfonyl)imide salt and / or N-methyl, propylpiperidinium bis(trifluoromethanesulfonyl)imide salt; And / or, the cyclic ether compound is 1,3-dioxane and / or 1,4-dioxane; And / or, the nitrile compound is adiponitrile and / or fumarodinitrile; And / or, the cyano-containing compound is selected from any one or more of 1,2-bis(cyanoethoxy)ethane, 1,3,5-pentanetricarbonitrile and 1,2,3-tris(2-cyanoethoxy)propane; Most preferably, the additive is methylene methanedisulfonate; And / or, the lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate and lithium difluorophosphate; Preferably, the lithium salt is lithium bis(fluorosulfonyl)imide.

[0032] The addition of the additive helps to further improve the comprehensive performance of the gel polymer electrolyte. In particular, the addition of methylene methanedisulfonate helps to promote the formation of the SEI film, reduce the internal resistance of the battery and improve the performance of the battery at high rates. Controlling the type of lithium salt within the above range helps to improve the solubility of the lithium salt in the organic solvent. In particular, lithium bis(fluorosulfonyl)imide has a high solubility in the organic solvent, and it has a low charge transfer resistance and good SEI film formation ability, which helps to further improve the cycle stability of the lithium metal battery.

[0033] In an embodiment of the present application, by mass fraction, the above gel polymer electrolyte composition consists of 83% of an organic solvent, 13% of a lithium salt, 1% of an additive and 3% of a polymerization monomer, wherein the organic solvent is a combination of The mass ratio is 17:50:16. The lithium salt is lithium bis(fluorosulfonyl)imide, the additive is methylene methanedisulfonate, the polymerizable monomer is a combination of ethoxylated trimethylolpropane triacrylate and trifluoroethyl methacrylate, and the mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate is 1:0.3.

[0034] In one embodiment of the present application, by mass fraction, the above gel polymer electrolyte composition consists of 81% organic solvent, 13% lithium salt, 1% additive, and 5% polymerizable monomer. Among them, the organic solvent is a combination of The mass ratio is 17:50:14. The lithium salt is lithium bis(fluorosulfonyl)imide, the additive is methylene methanedisulfonate, the polymerizable monomer is a combination of ethoxylated trimethylolpropane triacrylate and trifluoroethyl methacrylate, and the mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate is 1:0.5.

[0035] In another typical embodiment of the present application, a gel polymer electrolyte is provided, which is prepared by a polymerization reaction of the aforementioned gel polymer electrolyte composition.

[0036] Since the above gel polymer electrolyte is prepared by a polymerization reaction of the gel polymer electrolyte composition of the present application, the gel polymer electrolyte has good interfacial stability with the positive and negative electrodes, and the gel polymer electrolyte can form a relatively stable protective film on the surfaces of the positive and negative electrodes.

[0037] In one embodiment of the present application, the above gel polymer electrolyte is prepared by mixing the gel polymer electrolyte composition with an initiator and then undergoing a polymerization reaction; preferably, the mass of the initiator accounts for 0.5-1% of the polymerizable monomer, the initiator is azobisisobutyronitrile, the polymerization reaction is a thermal polymerization reaction, the temperature of the thermal polymerization reaction is 60-70 °C, and the time is 12-14 h.

[0038] In yet another typical embodiment of the present application, a lithium metal battery is provided, including a positive electrode sheet, a gel polymer electrolyte, and a lithium metal negative electrode sheet, and the gel polymer electrolyte is the aforementioned gel polymer electrolyte.

[0039] Since the above lithium metal battery has a gel polymer electrolyte prepared by a polymerization reaction of the gel polymer electrolyte composition of the present application, the lithium metal battery has excellent long-cycle performance at normal temperature and high temperature.

[0040] In yet another typical embodiment of the present application, a method for preparing a lithium metal battery is provided, including: stacking a positive electrode, a separator, and a lithium metal negative electrode in sequence and then superposing them; welding the electrode tabs and placing them in an outer packaging aluminum-plastic film, mixing the gel polymer electrolyte composition with an initiator and then adding it into the aluminum-plastic film, and performing in-situ polymerization through vacuum packaging, standing at room temperature for 24 hours, and heating at 60 °C for 12 hours to obtain a gel polymer electrolyte, followed by processes such as formation (constant current charging at 0.02C to 3.75V and then constant current charging at 0.1C to 4.3V), shaping, and capacity testing to obtain the lithium metal battery.

[0041] In yet another typical embodiment of the present application, a method for capacity restoration of the aforementioned lithium metal battery is provided. The capacity restoration method includes: testing the capacity retention rate H of the lithium metal battery. When 85% ≤ H ≤ 90%, the lithium metal battery is sequentially allowed to stand at 45 - 50 °C for 1 - 2 hours and cycled 5 - 10 times to end the capacity restoration.

[0042] The above capacity restoration mechanism can only be used when the capacity retention rate of the lithium metal battery has decayed to less than 90%. Because when the battery capacity retention rate is still relatively high, using high temperature for capacity restoration will affect the battery performance and accelerate the risk of cycle failure. However, if the capacity retention rate has decayed to less than 85% and then capacity restoration is carried out, many parts of the battery are already in an irreversible state and a good capacity restoration effect cannot be achieved. There are several benefits to performing capacity restoration within the above temperature range: (1) After the battery has undergone long-term cycling, a relatively thick electrolyte film will form on the surfaces of the positive and negative electrodes. After high-temperature heating, some components in the film will be thermally decomposed, and during the charge and discharge process, the electrolyte film is reset to obtain a thin and compact electrolyte film, reducing the overall impedance of the battery and thus restoring part of the capacity loss caused by battery polarization. (2) At high temperatures, the lithium ion migration speed of the battery can be effectively increased, which can dredge the lithium ions deposited on the negative electrode surface and restore part of the capacity loss caused by battery polarization. (3) During the cycling process of the lithium metal battery, the formation of lithium dendrites is inevitable. Some dendrites will gradually grow into the interior of the gel polymer electrolyte, posing a risk of short circuit. At high temperatures, there is a self-repair effect on the polymer, which can repair some of the micro-perforations caused by lithium dendrites.

[0043] In an embodiment of the present application, the above lithium metal battery is charged at a charging rate C1 and discharged at a discharging rate C2, and cycled in this way. When 85% ≤ H ≤ 90%, the lithium metal battery is placed in a 45 °C high-temperature oven and allowed to stand for two hours; in the 45 °C high-temperature oven, it is charged at a charging rate C3 and discharged at a discharging rate C4, and the cycle is repeated 5 - 10 times to end. The battery is restored to 25 °C, and the capacity restoration ends, where 1 ≤ C3 / C1 ≤ 1.5 and 0.2 ≤ C4 / C2 ≤ 1.

[0044] The beneficial effects of the present application will be further described below in conjunction with embodiments.

[0045] Example 1

[0046] In a dry argon atmosphere, a cyclic fluorinated carbonate compound a fluorine-free ether compound and a fluorinated ether compound are mixed evenly to obtain an organic solvent. Then, a lithium salt and an additive methylene methanesulfonate are added to the organic solvent and dissolved uniformly. Then, a polymer monomer is added. The polymer monomer is a fluorine-free acrylate monomer ethoxylated trimethylolpropane triacrylate and a fluorinated ester monomer trifluoroethyl methacrylate with a mass ratio of 1:0.3. After stirring evenly, a gel polymer electrolyte composition is obtained. In the gel polymer electrolyte composition, the mass ratio of the organic solvent is 83%, the mass ratio of the lithium salt is 13%, the mass ratio of the additive is 1%, the mass ratio of the polymer monomer is 3%, and the mass ratio of the cyclic fluorinated carbonate compound, the fluorine-free ether compound, and the fluorinated ether compound is 17:50:16.

[0047] Example 2

[0048] The difference from Example 1 is that the addition of the additive is cancelled. In the gel polymer electrolyte composition, the mass ratio of the organic solvent is 84%, the mass ratio of the lithium salt is 13%, the mass ratio of the polymer monomer is 3%, and the mass ratio of the cyclic fluorinated carbonate compound, the fluorine-free ether compound, and the fluorinated ether compound is 17:50:17.

[0049] Example 3

[0050] The difference from Example 1 is that in the gel polymer electrolyte composition, the mass ratio of the organic solvent is 81%, the mass ratio of the lithium salt is 13%, the mass ratio of the additive is 1%, the mass ratio of the polymer monomer is 5%, and the mass ratio of the cyclic fluorinated carbonate compound, the fluorine-free ether compound, and the fluorinated ether compound is 17:50:14.

[0051] Example 4

[0052] The difference from Example 1 is that in the gel polymer electrolyte composition, the mass ratio of the organic solvent is 85%, the mass ratio of the lithium salt is 13%, the mass ratio of the additive is 1%, the mass ratio of the polymer monomer is 1%, and the mass ratio of the cyclic fluorinated carbonate compound, the fluorine-free ether compound, and the fluorinated ether compound is 17:50:18.

[0053] Example 5

[0054] The difference from Example 1 is that the mass ratio of the cyclic fluorinated carbonate compound, the fluorine-free ether compound, and the fluorinated ether compound is 13:52:18.

[0055] Example 6

[0056] The difference from Example 1 is that the mass ratio of the cyclic fluorinated carbonate compound, the fluorine-free ether compound, and the fluorinated ether compound is 19:50:14.

[0057] Example 7

[0058] The difference from Example 1 is that the mass ratio of the cyclic fluorinated carbonate compound, the fluorine-free ether compound, and the fluorinated ether compound is 40:20:23.

[0059] Example 8

[0060] The difference from Example 1 is that the cyclic fluorinated carbonate compound is R 1 is methyl, R 2 is ethyl, R 3 is propyl, R 4 is fluorine; the fluorine-free ether compound is R 5 is ethyl, R 6 is methoxy; the fluorinated ether compound is

[0061] Example 9

[0062] The difference from Example 1 is that the cyclic fluorinated carbonate compound is R 1 is cyclohexyl, R 2 is 1-butenyl, R 3 is pyridyl, R 4 is fluorine; the fluorine-free ether compound is R 5 is n-butyl, R 6 is n-butoxy; the fluorinated ether compound is

[0064] Example 10

[0065] The difference from Example 1 is that the mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate is 1:0.1.

[0066] Example 11

[0067] The difference from Example 1 is that the mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate is 1:0.5.

[0068] Example 12

[0069] It is different from Example 1 in that the mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate is 1:1.

[0070] Example 13

[0071] It is different from Example 1 in that the acrylate monomer without fluorine is ethyl acetoacetate methacrylate, and the fluorinated ester monomer is methyl 2-fluoropropionate.

[0072] Example 14

[0073] It is different from Example 1 in that the acrylate monomer without fluorine is trimethylolpropane triacrylate, and the fluorinated ester monomer is 1H,1H-perfluorooctyl methacrylate.

[0074] Comparative Example 1

[0075] It is different from Example 1 in that the addition of the cyclic fluorinated carbonate compound is cancelled, the mass fraction of the fluorine-free ether compound in the gel polymer electrolyte composition is 67%, and the mass fraction of the fluorinated ether compound is 16.

[0076] Comparative Example 2

[0077] It is different from Example 1 in that the addition of the fluorine-free ether compound is cancelled, the mass fraction of the cyclic fluorinated carbonate compound in the gel polymer electrolyte composition is 67%, and the mass fraction of the fluorinated ether compound is 16.

[0078] Comparative Example 3

[0079] It is different from Example 1 in that the addition of the fluorinated ether compound is cancelled, the mass fraction of the fluorine-free ether compound in the gel polymer electrolyte composition is 67%, and the mass fraction of the cyclic fluorinated carbonate compound is 16.

[0080] Comparative Example 4

[0081] It is different from Example 1 in that the mass fraction of the organic solvent in the gel polymer electrolyte composition is 66%, the mass fraction of the lithium salt is 13%, the mass fraction of the additive is 1%, the mass fraction of the polymerization monomer is 20%, and the mass ratio of the cyclic fluorinated carbonate compound, the fluorine-free ether compound and the fluorinated ether compound is 13:41:12.

[0082] Battery Preparation

[0083] In a physical rolling method, metallic lithium is compounded onto a copper foil of the negative electrode current collector with a thickness of about 12 μm. By adjusting the pressure of the roller, lithium is coated on one side of the copper current collector, and the thickness is controlled to be about 50 μm. Then, after slitting and cutting, a negative electrode sheet is obtained; nickel cobalt manganese (NCM) positive electrode active material, a conductive agent (conductive carbon of Super P), and a binder polyvinylidene fluoride are mixed in a weight ratio of 97:1.4:1.6, N-methylpyrrolidone (NMP) is added, and the mixture is stirred in a vacuum mixer until the system is homogeneous to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry is 72 wt%; the positive electrode slurry is uniformly coated on an aluminum foil of the positive electrode current collector; after drying, and then through cold pressing, slitting, and cutting, it is dried under vacuum conditions at about 85 °C for about 4 h to obtain a positive electrode sheet; polyethylene (PE) with a thickness of 15 μm is used as the separator;

[0084] Azobisisobutyronitrile is added as an initiator to the gel polymer electrolyte composition prepared in the above examples and comparative examples. The mass of azobisisobutyronitrile accounts for 0.5% of the mass of the polymerization monomer to obtain a mixed solution. The positive electrode sheet, the separator, and the lithium metal negative electrode sheet are stacked in sequence and then superposed; after welding the electrode tabs, they are placed in an outer packaging aluminum plastic film, and the above mixed solution is injected into the aluminum plastic film. Through vacuum packaging, standing at room temperature for 24 hours, and in-situ polymerization by heating at 60 °C for 12 h, a gel polymer electrolyte is obtained, followed by processes such as formation (constant current charging at 0.02C to 3.75V, and then constant current charging at 0.1C to 4.3V), shaping, and capacity testing to obtain a soft-pack laminated lithium metal battery.

[0085] Performance testing

[0086] The soft-pack laminated lithium metal batteries prepared above are respectively subjected to cycle testing at 25 °C and 45 °C. 25 °C cycle testing: The lithium metal battery is placed in a 25 °C constant temperature oven and left to stand for 30 minutes to make the lithium metal battery reach a constant temperature. The lithium metal battery at a constant temperature is subjected to constant current charging at 0.2C to 4.3V, then constant voltage to 0.5V, and then constant current discharging at 1C to a voltage of 3V. This is one charge-discharge cycle. Taking the capacity of the first discharge as 100%, the charge-discharge cycle is repeated until the discharge capacity decays to 80%, at which point the test is stopped and the number of cycle turns is recorded as an index for evaluating the cycle performance of the lithium metal battery. 45 °C cycle testing: The lithium metal battery is placed in a 45 °C constant temperature oven and left to stand for 30 minutes to make the lithium metal battery reach a constant temperature. The lithium metal battery at a constant temperature is subjected to constant current charging at 0.2C to 4.3V, then constant voltage to 0.5V, and then constant current discharging at 1C to a voltage of 3V. This is one charge-discharge cycle. Taking the capacity of the first discharge as 100%, the charge-discharge cycle is repeated until the discharge capacity decays to 80%, at which point the test is stopped and the number of cycle turns is recorded as an index for evaluating the cycle performance of the lithium metal battery.

[0087] And during the test, the following capacity repair methods are adopted for capacity repair:

[0088] Capacity repair method 1: When the capacity retention rate of the lithium metal battery reaches 85%, remove the battery and place it in a high-temperature oven at 45°C. Charge it at a charging rate of 0.3C and discharge it at a discharging rate of 1C. Repeat the cycle 5 times and then end. Next, restore the battery to room temperature, and the capacity repair is completed.

[0089] Capacity repair method 2: When the capacity retention rate of the lithium metal battery reaches 90%, remove the battery and place it in a high-temperature oven at 45°C. Charge it at a charging rate of 0.3C and discharge it at a discharging rate of 1C. Repeat the cycle 5 times and then end. Next, restore the battery to room temperature, and the capacity repair is completed.

[0090] Capacity repair method 3: When the capacity retention rate of the lithium metal battery reaches 85%, remove the battery and place it in a high-temperature oven at 45°C. Charge it at a charging rate of 0.2C and discharge it at a discharging rate of 0.2C. Repeat the cycle 5 times and then end. Next, restore the battery to room temperature, and the capacity repair is completed.

[0091] Capacity repair method 4: When the capacity retention rate of the lithium metal battery reaches 60%, remove the battery and place it in a high-temperature oven at 45°C. Charge it at a charging rate of 0.2C and discharge it at a discharging rate of 0.2C. Repeat the cycle 5 times and then end. Next, restore the battery to room temperature, and the capacity repair is completed.

[0092] Capacity repair method 5: When the capacity retention rate of the lithium metal battery reaches 85%, remove the battery and place it in a high-temperature oven at 60°C. Charge it at a charging rate of 0.2C and discharge it at a discharging rate of 0.2C. Repeat the cycle 5 times and then end. Next, restore the battery to room temperature, and the capacity repair is completed.

[0093] The results of the cycle tests of the above lithium metal battery at 25°C and 45°C are shown in Table 1.

[0094] Table 1

[0095]

[0096]

[0097] In Table 1, from the test results of the capacity repair method of the battery combination method 1 prepared in Example 1 and Example 2, it can be seen that adding additives can improve the cycle performance of the lithium metal battery because the additives form a film on the negative electrode, which is beneficial to the deposition of lithium.

[0098] From the test results of the batteries prepared in Example 1 combined with the capacity restoration methods of Method 1, Method 2, Method 3, Method 4, and Method 5 respectively, it can be seen that if incorrect capacity restoration methods are used, the cycle performance of the batteries will be greatly affected.

[0099] From the test results of Comparative Examples 1-3 and Example 1 combined with the capacity restoration method of Method 1, it can be seen that three compounds, namely cyclic fluorinated carbonate compounds, fluorine-free ether compounds, and fluorinated ether compounds, need to be used in combination to achieve a better cycle effect.

[0100] From the test results of Comparative Example 4 and Example 1 combined with the capacity restoration method of Method 1, it can be seen that if too much copolymer monomer is added and the degree of electrolyte solidification is too high, the kinetic performance of the battery will decline, which will greatly affect the normal temperature cycle performance of the battery.

[0101] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0102] The presence of the polymerization monomer helps to form a stable and uniform copolymer framework during the subsequent polymerization reaction process. This framework not only provides physical structure support but also can effectively restrict the free flow of the electrolyte, thereby inhibiting the formation of lithium dendrites, reducing the risk of internal short circuits, and improving the safety of the battery. The main role of the fluorine-free acrylate monomer in the polymerization monomer is to form the gel polymer skeleton. The addition of the fluorinated ester monomer helps to improve the oxidation resistance of the skeleton at the positive electrode and can also form a SEI film rich in LiF at the negative electrode, thus contributing to improving the long-cycle stability of the lithium metal battery. Too low a proportion of the polymerization monomer may result in insufficient mechanical strength of the gel polymer electrolyte, while too high a proportion may increase the viscosity of the gel and affect the mobility of lithium ions. Controlling the proportion of the polymerization monomer within the above range helps to make the formed gel polymer electrolyte have appropriate mechanical strength and good ionic conductivity, balancing the kinetic performance and chemical stability. The presence of cyclic fluorinated carbonate compounds and fluorinated ether compounds in the organic solvent helps the electrolyte to form a SEI film with LiF components on the surface of the negative electrode, and this organic solvent is more oxidation-resistant on the positive electrode side, which is beneficial to improving the cycle performance of the lithium metal battery. Moreover, the cyclic fluorinated carbonate compound has good solubility in the lithium salt, and it can also form an organic polymer SEI containing C and O on the surface of the negative electrode, together with the inorganic LiF, Li 3After N binding, better stability performance can be exerted. Cyclic fluorinated carbonate compounds have a relatively high viscosity, while fluorine-free ether compounds and fluorinated ether compounds have a relatively low viscosity. The presence of fluorine-free ether compounds helps to regulate the viscosity of the electrolyte on the one hand and reduces the reaction activity of the electrolyte at the negative electrode on the other hand, thus contributing to improving the long-cycle performance of the lithium metal battery. In addition to helping to regulate the viscosity of the electrolyte, fluorinated ether compounds have good stability towards the lithium metal negative electrode, are difficult to react with active lithium metal, and can form a tight positive electrode protective film at the positive electrode. Controlling the mass ratio of the organic solvent within the above range helps to form a stable SEI film on the positive and negative electrodes of the battery, thus contributing to improving the cycle stability of the lithium metal battery. The gel polymer electrolyte formed from the gel polymer electrolyte composition of the present application helps to inhibit the growth of lithium dendrites, forms a stable SEI film on the positive and negative electrodes of the battery, and reduces side reactions, thus contributing to improving the cycle stability performance and safety of the lithium metal battery at room temperature and high temperature.

[0103] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A gel polymer electrolyte composition, characterized in that: Measured by mass fraction, the gel polymer electrolyte composition comprises: 1-10% of polymerized monomers; 60-85% organic solvent; and The balance of lithium salt; The organic solvent contains at least cyclic fluorinated carbonate compounds, fluorine-free ether compounds and fluorinated ether compounds, and the polymerizable monomers contain at least fluorine-free acrylate monomers and fluorinated ester monomers.

2. The gel polymer electrolyte composition according to claim 1, characterized in that: The organic solvent is a combination of the cyclic fluorocarbonate compound, the fluorine-free ether compound and the fluorinated ether compound, and the mass ratio of the cyclic fluorocarbonate compound, the fluorine-free ether compound and the fluorinated ether compound is (1-40):(1-70):(1-40).

3. The gel polymer electrolyte composition according to claim 1 or 2, characterized in that: The structure of the cyclic fluorinated carbonate compound is wherein R1, R2, R3 and R4 are each independently selected from hydrogen, fluorine, fluorine-substituted or unsubstituted C1-C 12 Alkyl, fluorine-substituted or unsubstituted C3~C 12 Cycloalkyl, fluorine-substituted or unsubstituted C2~C 12 alkenyl, and fluorine-substituted or unsubstituted C3~C 12 any one of the heterocyclic groups, and at least one of the R1, R2, R3 and R4 is selected from the fluorine, the fluorine-substituted C1-C 12 Alkyl, the fluorine-substituted C3~C 12 Cycloalkyl, the fluorine-substituted C2-C 12 The alkenyl and the fluorine-substituted C3~C 12 Any of the heterocyclic groups; Preferably, the R1, the R2, the R3 and the R4 are each independently selected from any one of the hydrogen, the fluorine, the fluorine-substituted or unsubstituted C1-C6 alkyl, the fluorine-substituted or unsubstituted C3-C6 cycloalkyl, the fluorine-substituted or unsubstituted C2-C6 alkenyl, and the fluorine-substituted or unsubstituted C3-C6 heterocyclic group, and at least one of the R1, the R2, the R3 and the R4 is selected from any one of the fluorine, the fluorine-substituted C1-C6 alkyl, the fluorine-substituted C3-C6 cycloalkyl, the fluorine-substituted C2-C6 alkenyl and the fluorine-substituted C3-C6 heterocyclic group; Further preferably, the R1, the R2, the R3 and the R4 are each independently selected from any one of the hydrogen, the fluorine, and a fluorine-substituted or unsubstituted C1-C3 alkyl group, and at least one of the R1, the R2, the R3 and the R4 is selected from any one of the fluorine and the fluorine-substituted C1-C3 alkyl group; Most preferably, the R1, R2, R3 and R4 are each independently the hydrogen or the fluorine, and one of the R1, R2, R3 and R4 is the fluorine.

4. The gel polymer electrolyte composition according to any one of claims 1 to 3, characterized in that: The structural formula of the non-fluorinated ether compound is Wherein, R5 and R6 are each independently selected from C1 to C 10 Any of the alkyl groups; Preferably, the R5 and the R6 are each independently selected from any one of C1 to C6 alkyl groups; Further preferably, the R5 and the R6 are each independently selected from any one of C1 to C3 alkyl groups; Most preferably, said R5 and said R6 are each independently methyl.

5. The gel polymer electrolyte composition according to any one of claims 1 to 4, characterized in that: The structure of the fluoroether compound is Wherein, R7 and R8 are each independently selected from C1 to C 10 Halogenated alkyl and C2~C 10 Any of the following haloalkenyl groups; Preferably, the R7 and R8 are each independently selected from any one of C1-C6 haloalkyl and C2-C6 haloalkenyl; Further preferably, the R7 and the R8 are each independently selected from any one of C1 to C3 haloalkyl groups; Most preferably, said R7 and said R8 are each independently 6. The gel polymer electrolyte composition according to any one of claims 1 to 5, characterized in that: The polymerizable monomer is a combination of the fluorine-free acrylic ester monomer and the fluorinated ester monomer, and the mass ratio of the fluorine-free acrylic ester monomer to the fluorinated ester monomer is 1:(0.1-0.5); Further preferably, the fluorine-free acrylate monomer is selected from any one or more of ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, acetoacetoxyethyl methacrylate, methyl methacrylate, ethyl acrylate and decaacrylate; And / or, the fluoroester monomer is selected from any one or more of trifluoroethyl methacrylate, allyl trifluoroacetate, fluoroethylene carbonate, hexafluorobutyl methacrylate, hexafluoroisobutyl methacrylate, 1H,1H-perfluorooctyl methacrylate, methyl 2-trifluoromethacrylate, methyl 2-fluoroacrylate and pentafluorophenol acrylate; Most preferably, the fluorine-free acrylate monomer is ethoxylated trimethylolpropane triacrylate; And / or, the fluorinated ester monomer is trifluoroethyl methacrylate.

7. The gel polymer electrolyte composition according to any one of claims 1 to 6, characterized in that: The gel polymer electrolyte composition further comprises 0.01 to 10% of an additive, Preferably, the additive is selected from any one or more of lithium-containing compounds, ester compounds, thiophene compounds, acid anhydride compounds, amide compounds, cyclic ether compounds, nitrile compounds and cyano compounds; Further preferably, the lithium-containing compound is selected from any one or more of lithium dioxalatoborate, lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium nitrate; And / or, the ester compound is selected from any one or more of fluoroethylene carbonate, ethylene ethylene, methylene methanedisulfonate, 4-trifluoromethylethylene carbonate, fluoroethylene carbonate, ethylene sulfite, vinylene carbonate, propylene sulfite, propenyl-1,3-sultone and bis(trimethylsilyl) sulfate; And / or, the thiophene compound is 1,3,2-dioxazolethiophene-2,2-dioxide; And / or, the acid anhydride compound is succinic anhydride; And / or, the amide compound is N-methyl, butyl pyrrolidine bis trifluoromethanesulfonyl imide salt and / or N-methyl, propyl piperidine bis trifluoromethanesulfonyl imide salt; And / or, the cyclic ether compound is 1,3-dioxane and / or 1,4-dioxane; And / or, the nitrile compound is adiponitrile and / or butylenedinitrile; And / or, the cyano compound is selected from any one or more of 1,2-bis(cyanoethoxy)ethane, 1,3,5-pentanetricarbonitrile and 1,2,3-tris(2-cyanoethoxy)propane; Most preferably, the additive is methylene methanedisulfonate; And / or, the lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl imide), lithium bis(fluorosulfonyl imide), lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium trifluoromethylsulfonate and lithium difluorophosphate.

8. A gel polymer electrolyte, characterized in that: The gel polymer electrolyte is prepared by a polymerization reaction of the gel polymer electrolyte composition according to any one of claims 1 to 7.

9. A lithium metal battery, comprising a positive electrode, a gel polymer electrolyte and a lithium metal negative electrode, characterized in that: The gel polymer electrolyte is the gel polymer electrolyte according to claim 8.

10. A method for repairing the capacity of a lithium metal battery according to claim 9, characterized in that: The capacity repair method comprises: The capacity retention rate H of the lithium metal battery is tested. When 85%≤H≤90%, the lithium metal battery is left to stand for 1 to 2 hours and cycled for 5 to 10 times at 45 to 50° C. to complete the capacity repair.

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