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

Abstract

This invention provides a gel polymer electrolyte composition, a gel polymer electrolyte, a lithium metal battery, and a method for capacity restoration thereof. The gel polymer electrolyte composition comprises, by mass fraction: 1-10% polymeric monomers, 60-85% organic solvents, and the balance lithium salt; wherein the organic solvent contains at least cyclic fluorocarbonate compounds, non-fluorinated ether compounds, and fluorinated ether compounds, and the polymeric monomers contain at least non-fluorinated acrylate monomers and fluorinated ester monomers. The gel polymer electrolyte formed from the gel polymer electrolyte composition of this application helps to suppress the growth of lithium dendrites, forms a stable SEI film on the positive and negative electrodes of the battery, and reduces side reactions, thereby contributing to improving the cycle stability and safety of lithium metal batteries at room temperature and high temperature.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a gel polymer electrolyte composition, a gel polymer electrolyte, a lithium metal battery, and a method for restoring the capacity of the same. Background Technology

[0002] With the widespread adoption of consumer electronics such as laptops, mobile phones, handheld game consoles, tablets, power banks, and drones, the requirements for their electrochemical components (e.g., batteries) are becoming increasingly stringent. For example, batteries are not only required to be lightweight, but also to have short charging times and long operating lifespans. Among the various battery types, lithium metal batteries have garnered significant attention in research and development due to their highest energy density. Currently, improving the cycle performance of lithium metal batteries has become a key focus of research in this field.

[0003] The specific capacity of lithium metal as the anode can reach 3860 mAh / g, which is more than ten times higher than the theoretical specific capacity of graphite (372 mAh / g). However, lithium metal has the lowest chemical potential (-3.04V) and very high reactivity. In the battery, it reacts with the electrolyte, consuming lithium, increasing the battery impedance, and ultimately leading to cycle failure. Therefore, although lithium metal can significantly improve energy density when used as a battery anode material, its cycle life is also drastically shortened.

[0004] There are three important directions for improving the cycle performance of lithium metal batteries: 1. Forming a stable solid electrolyte interphase (SEI) film on the surface of the lithium metal anode. A uniform and stable SEI can reduce the reactivity between lithium metal and the electrolyte, and also inhibit the formation of lithium dendrites, effectively improving the battery's cycle performance. 2. Developing electrolytes with low reactivity with the lithium metal anode. The electrolyte can be liquid, gel, or all-solid-state. Reduced reactivity between the electrolyte and lithium metal can effectively improve the battery's cycle coulombic efficiency and cycle life. 3. Using appropriate capacity repair mechanisms to restore the capacity of lithium metal batteries that have already shown a trend of cycle degradation. However, current technologies still have limitations in improving the cycle performance of lithium metal batteries. Summary of the Invention

[0005] The main objective of this invention is to provide a gel polymer electrolyte composition, a gel polymer electrolyte, a lithium metal battery, and a method for capacity restoration thereof, so as to solve the problem of poor cycle performance of lithium metal batteries in the prior art.

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

[0007] Furthermore, the organic solvent is a combination of cyclic fluorocarbonate compounds, non-fluorinated ether compounds, and fluoroether compounds, and the mass ratio of the cyclic fluorocarbonate compounds, non-fluorinated ether compounds, and fluoroether compounds is (1-40):(1-70):(1-40).

[0008] Furthermore, the structure of the above-mentioned cyclic fluorocarbonate compounds is as follows: Among them, R1, R2, R3, and R4 are each independently selected from hydrogen, fluorine, fluorine-substituted or unsubstituted C1 to C4 atoms. 12 Alkyl, fluorinated or unsubstituted C3-C 12 Cycloalkyl, fluorinated or unsubstituted C2-C 12 Alkenyl groups, and fluorinated or unsubstituted C3-C3 groups. 12 Any one of the heterocyclic groups, and at least one of R1, R2, R3, and R4 is selected from fluorine, fluorine-substituted C1-C4 groups. 12 Alkyl or fluorine-substituted C3-C 12 Cycloalkyl, fluorine-substituted C2-C 12 Alkenyl and fluorine-substituted C3-C 12 Any one of the heterocyclic groups; preferably, R1, R2, R3, and R4 are each independently selected from any one of hydrogen, fluorine, fluorine-substituted or unsubstituted C1-C6 alkyl, fluorine-substituted or unsubstituted C3-C6 cycloalkyl, fluorine-substituted or unsubstituted C2-C6 alkenyl, and fluorine-substituted or unsubstituted C3-C6 heterocyclic groups, and at least one of R1, R2, R3, and R4 is selected from fluorine, fluorine-substituted C1-C6 alkyl, fluorine-substituted C3-C6 cycloalkyl, fluorine-substituted C2-C6 heterocyclic groups. Any one of C6 alkenyl and fluorinated C3-C6 heterocyclic groups; more preferably, R1, R2, R3 and R4 are each independently selected from hydrogen, fluorine and fluorinated or unsubstituted C1-C3 alkyl groups, and at least one of R1, R2, R3 and R4 is selected from fluorine and fluorinated C1-C3 alkyl groups; most preferably, R1, R2, R3 and R4 are each independently hydrogen or fluorine, and one of R1, R2, R3 and R4 is fluorine.

[0009] Furthermore, the structural formula of the above-mentioned non-fluorinated ether compounds is as follows: Among them, R5 and R6 are each independently selected from C1 to C2. 10 R5 and R6 are each independently selected from any one of C1 to C6 alkyl groups; more preferably, R5 and R6 are each independently selected from any one of C1 to C3 alkyl groups; most preferably, R5 and R6 are each independently methyl groups.

[0010] Furthermore, the structure of the above-mentioned fluorinated ether compounds is as follows: Among them, R7 and R8 are each independently selected from C1 to C2. 10 Haloalkyl and C2-C 10 R7 and R8 are each independently selected from any one of C1-C6 haloalkyl and C2-C6 haloalkyl groups; more preferably, R7 and R8 are each independently selected from any one of C1-C3 haloalkyl groups; most preferably, R7 and R8 are each independently selected from any one of C1-C3 haloalkyl groups.

[0011] Further, the above-mentioned polymerizable monomers are a combination of fluorine-free acrylate monomers and fluorinated ester monomers, and the mass ratio of fluorine-free acrylate monomers to fluorinated ester monomers is 1:(0.1-0.5); more preferably, the fluorine-free acrylate monomers are selected from any one or more of ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, ethyl acetoacetate methacrylate, methyl methacrylate, ethyl acrylate, and decaacrylate; and / or, the fluorinated ester monomers are selected from any one or more of trifluoroethyl methacrylate, allyl trifluoroacetate, fluoroethylene carbonate, hexafluorobutyl methacrylate, hexafluoroisobutyl methacrylate, 1H,1H-perfluorooctyl methacrylate, methyl 2-trifluoromethyl methacrylate, 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.

[0012] Further, the above-mentioned gel polymer electrolyte composition further includes 0.01-10% of additives, preferably selected from 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; more preferably, the lithium-containing compounds are selected from one or more of lithium dioxolane borate, lithium difluorooxolane borate, lithium tetrafluoroborate, and lithium nitrate; and / or, the ester compounds are selected from one or more of fluoroethylene carbonate, ethylene ethylene, methane disulfonate, 4-trifluoromethyl ethylene carbonate, fluoroethylene carbonate, ethylene sulfite, ethylene carbonate, propylene sulfite, propylene-1,3-sulfonyl lactone, and bis(trimethylsilyl)sulfate; and / or, the thiophene compound is 1,3,2-dioxazothiophene-2,2-dioxazothiophene. Oxides; and / or, acid anhydrides are succinic anhydride; and / or, amides are N-methyl,butylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and / or N-methyl,propylpiperidine bis(trifluoromethanesulfonyl)imide salt; and / or, cyclic ethers are 1,3-dioxane and / or 1,4-dioxane; and / or, nitriles are adiponitrile and / or trans-butenedionitrile; and / or, cyano-containing compounds are selected from 1,2-bis(cyanoethoxy) The lithium salt is selected from any one or more of ethane, 1,3,5-pentanetricarbonyl nitrile, and 1,2,3-tris(2-cyanoethoxy)propane; most preferably, the additive is methylene disulfonate; 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 dioxalateborate, lithium difluorooxalateborate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluorophosphate.

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

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

[0015] According to another aspect of the present invention, a capacity repair method for the aforementioned lithium metal battery is provided, the capacity repair method comprising: testing the capacity retention rate H of the lithium metal battery; when 85% ≤ H ≤ 90%, sequentially placing the lithium metal battery at 45-50°C for 1-2 hours and cycling it for 5-10 cycles to end the capacity repair.

[0016] By applying the technical solution of this application, the presence of polymeric monomers helps to form a stable and uniform copolymer framework during the subsequent polymerization reaction. This framework not only provides physical structural support but also effectively restricts the free flow of electrolyte, thereby inhibiting the formation of lithium dendrites, reducing the risk of internal short circuits, and improving battery safety. The main role of fluorine-free acrylate monomers in the polymeric monomers is to form the gel polymer backbone. The addition of fluorinated ester monomers helps to improve the oxidation resistance of the backbone at the positive electrode and can also form a LiF-rich SEI film at the negative electrode, thus contributing to improved long-cycle stability of lithium metal batteries. Too low a proportion of polymeric monomers may lead to insufficient mechanical strength of the gel polymer electrolyte, while too high a proportion may increase the viscosity of the gel, affecting lithium-ion mobility. Controlling the proportion of polymeric monomers within the aforementioned range helps to ensure that the formed gel polymer electrolyte has suitable mechanical strength and good ionic conductivity, balancing kinetic performance and chemical stability. The presence of cyclic fluorocarbonates and fluoroethers in organic solvents facilitates the formation of a LiF-based SEI film on the negative electrode surface. Furthermore, these organic solvents offer greater oxidation resistance on the positive electrode side, improving the cycle performance of lithium metal batteries. Cyclic fluorocarbonates exhibit excellent solubility for lithium salts and can form C- and O-containing organic polymer SEIs on the negative electrode surface, exhibiting better stability when combined with inorganic LiF and Li3N. Cyclic fluorocarbonates have higher viscosity, while fluorine-free ethers and fluoroethers have lower viscosity. The presence of fluorine-free ethers helps regulate electrolyte viscosity and reduces electrolyte reactivity at the negative electrode, thus improving the long-cycle performance of lithium metal batteries. In addition to regulating electrolyte viscosity, fluoroethers offer good stability to the lithium metal negative electrode, are less likely to react with reactive lithium metal, and can form a tight protective film on the positive electrode. Controlling the mass percentage of organic solvents within the aforementioned range helps to form stable SEI films on the positive and negative electrodes of the battery, thereby improving the cycle stability of lithium metal batteries. The gel polymer electrolyte formed from the gel polymer electrolyte composition of this application helps to suppress lithium dendrite growth, form stable SEI films on the positive and negative electrodes of the battery, and reduce side reactions, thereby contributing to improved cycle stability and safety of lithium metal batteries at both room temperature and high temperature. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0018] As analyzed in the background section of this application, lithium metal batteries in the prior art have the problem of poor cycle performance. In order to solve this problem, this application provides a gel polymer electrolyte composition, a gel polymer electrolyte, a lithium metal battery, and a method for capacity restoration thereof.

[0019] In a typical embodiment of this application, a gel polymer electrolyte composition is provided, comprising, by mass fraction: 1-10% polymeric monomers, 60-85% organic solvents, and the balance being a lithium salt; wherein the organic solvent contains at least cyclic fluorocarbonate compounds, fluorine-free ether compounds, and fluorinated ether compounds, and the polymeric monomers contain at least fluorine-free acrylate monomers and fluorinated ester monomers.

[0020] The presence of monomers facilitates the formation of a stable and uniform copolymer framework during subsequent polymerization reactions. This framework not only provides physical structural support but also effectively restricts the free flow of electrolyte, thereby inhibiting lithium dendrite formation, reducing the risk of internal short circuits, and improving battery safety. The main role of fluorine-free acrylate monomers in the polymerization process is to form the gel polymer backbone. The addition of fluorinated ester monomers helps improve the oxidation resistance of the backbone at the positive electrode and can also form a LiF-rich SEI film at the negative electrode, thus contributing to improved long-cycle stability of lithium metal batteries. Too low a monomer ratio may lead to insufficient mechanical strength of the gel polymer electrolyte, while too high a ratio may increase the viscosity of the gel, affecting lithium-ion mobility. Controlling the monomer ratio within the aforementioned range helps to ensure that the formed gel polymer electrolyte has suitable mechanical strength and good ionic conductivity, balancing kinetic performance and chemical stability. The presence of cyclic fluorocarbonate compounds and fluoroether compounds in the organic solvent helps the electrolyte form a LiF-component SEI film on the negative electrode surface, and this organic solvent is more oxidation-resistant on the positive electrode side, which is beneficial for improving the cycle performance of lithium metal batteries. Furthermore, cyclic fluorocarbonate compounds exhibit excellent solubility for lithium salts and can form C- and O-containing organic polymers (SEI) on the negative electrode surface. When combined with inorganic LiF and Li3N, they demonstrate superior stability. Cyclic fluorocarbonate compounds have high viscosity, while non-fluorinated ether compounds and fluoroether compounds have lower viscosity. The presence of non-fluorinated ether compounds helps regulate electrolyte viscosity and reduces electrolyte reactivity at the negative electrode, thus improving the long-cycle performance of lithium metal batteries. Fluorinated ether compounds, in addition to helping regulate electrolyte viscosity, exhibit good stability at the lithium metal negative electrode, rarely reacting with reactive lithium metal, and can form a tight protective film at the positive electrode. Controlling the mass percentage of organic solvents within the aforementioned range helps them form stable SEI films at both the positive and negative electrodes, thereby improving the cycle stability of lithium metal batteries. The gel polymer electrolyte formed by the gel polymer electrolyte composition of this application helps to suppress the growth of lithium dendrites, form a stable SEI film on the positive and negative electrodes of the battery, and reduce side reactions, thereby helping to improve the cycle stability and safety of lithium metal batteries at room temperature and high temperature.

[0021] It should be noted that the compounds in this application are all known compounds in the prior art and are commercially available.

[0022] In one embodiment of this application, the mass ratio of the polymeric monomer to the organic solvent is (3-5):(81-84), specifically 3:84, 3:83, 4:83, 4:82, 5:81, and a range between the two ratios.

[0023] Polymer monomers can form a moderately cross-linked three-dimensional network structure, namely a gel polymer framework, in organic solvents. This framework maintains good mechanical stability, preventing lithium dendrite penetration, without excessively increasing the electrolyte viscosity and affecting the lithium-ion migration rate. Controlling the mass ratio of polymer monomers to organic solvents within the aforementioned range helps maintain an appropriate electrolyte viscosity, improves the solubility of lithium salts and lithium-ion transport efficiency, and promotes the formation of a stable SEI film on the positive and negative electrode surfaces, thereby improving the cycle efficiency and stability of lithium metal batteries.

[0024] In one embodiment of this application, the organic solvent is a combination of cyclic fluorocarbonate compounds, non-fluorinated ether compounds, and fluoroether compounds, and the mass ratio of the cyclic fluorocarbonate compounds, non-fluorinated ether compounds, and fluoroether compounds is (1-40):(1-70):(1-40), preferably (13-19):(50-52):(14-18).

[0025] Cyclic fluorocarbonate compounds exhibit good solubility for lithium salts and can form a stable SEI film on the negative electrode surface. However, their high viscosity limits their application, as excessive amounts can negatively impact electrolyte viscosity and thus battery kinetics. Furthermore, at high voltages, cyclic fluorocarbonate compounds undergo ring-opening reactions, producing carbon dioxide, which affects positive electrode stability and leads to gas generation within the battery. Combining them with non-fluorinated ether compounds and fluorinated ether compounds can regulate electrolyte viscosity and reduce electrolyte reactivity at the negative electrode, promoting longer battery cycles. Additionally, fluorinated ether compounds can form a tight protective film on the positive electrode. Maintaining the mass ratio of cyclic fluorocarbonate compounds, non-fluorinated ether compounds, and fluorinated ether compounds within the aforementioned range enhances their synergistic effect, contributing to the formation of a stable protective film on both the positive and negative electrode surfaces, improving interfacial stability, and ultimately enhancing the cycle stability of lithium metal batteries.

[0026] To further improve the solubility of cyclic fluorocarbonate compounds in lithium salts and enhance the stability of the SEI film formed on the negative electrode surface, in one embodiment of this application, the structure of the aforementioned cyclic fluorocarbonate compound is preferably as follows: Among them, R1, R2, R3, and R4 are each independently selected from hydrogen, fluorine, fluorine-substituted or unsubstituted C1 to C4 atoms. 12 Alkyl, fluorinated or unsubstituted C3-C 12 Cycloalkyl, fluorinated or unsubstituted C2-C 12 Alkenyl and fluorine-substituted or unsubstituted C3-C 12Any one of the heterocyclic groups, and at least one of R1, R2, R3, and R4 is selected from fluorine, fluorine-substituted C1-C4 groups. 12 Alkyl or fluorine-substituted C3-C 12 Cycloalkyl, fluorine-substituted C2-C 12 Alkenyl groups and fluorinated C3-C groups 12 Any one of the heterocyclic groups; preferably, R1, R2, R3, and R4 are each independently selected from any one of hydrogen, fluorine, fluorine-substituted or unsubstituted C1-C6 alkyl, fluorine-substituted or unsubstituted C3-C6 cycloalkyl, fluorine-substituted or unsubstituted C2-C6 alkenyl, and fluorine-substituted or unsubstituted C3-C6 heterocyclic groups, and at least one of R1, R2, R3, and R4 is selected from fluorine, fluorine-substituted C1-C6 alkyl, fluorine-substituted C3-C6 cycloalkyl, fluorine-substituted C2-C6 heterocyclic groups. Any one of C6 alkenyl and fluorinated C3-C6 heterocyclic groups; more preferably, R1, R2, R3 and R4 are each independently selected from hydrogen, fluorine and fluorinated or unsubstituted C1-C3 alkyl groups, and at least one of R1, R2, R3 and R4 is selected from fluorine and fluorinated C1-C3 alkyl groups; most preferably, R1, R2, R3 and R4 are each independently hydrogen or fluorine, and one of R1, R2, R3 and R4 is fluorine.

[0027] To further reduce the viscosity and reactivity of the fluorine-free ether compound on the negative electrode surface, in one embodiment of this application, the preferred structural formula of the fluorine-free ether compound is as follows: Among them, R5 and R6 are each independently selected from C1 to C2. 10 R5 and R6 are each independently selected from any one of C1 to C6 alkyl groups; more preferably, R5 and R6 are each independently selected from any one of C1 to C3 alkyl groups; most preferably, R5 and R6 are each independently methyl groups.

[0028] To further reduce the reactivity of fluorinated ether compounds on the lithium metal anode surface and improve the stability of the protective film formed on the cathode surface, in one embodiment of this application, the structure of the aforementioned fluorinated ether compounds is preferably as follows: Among them, R7 and R8 are each independently selected from C1 to C2. 10 Haloalkyl and C2-C 10 R7 and R8 are each independently selected from any one of C1-C6 haloalkyl and C2-C6 haloalkyl groups; more preferably, R7 and R8 are each independently selected from any one of C1-C3 haloalkyl groups; most preferably, R7 and R8 are each independently selected from any one of C1-C3 haloalkyl groups.

[0029] In one embodiment of this application, the polymerizable monomer is a combination of fluorine-free acrylate monomers and fluorinated ester monomers, and the mass ratio of the fluorine-free acrylate monomers to the fluorinated ester monomers is 1:(0.1 to 0.5), specifically 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, and a range between these two ratios; more preferably, the fluorine-free acrylate monomers are selected from ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, ethyl acetoacetate methacrylate, and methyl methacrylate. The monomer is selected from any one or more of ethyl acrylate and decaacrylate; and / or, the fluorinated ester 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-trifluoromethyl methacrylate, 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.

[0030] Excessive fluorinated ester monomer content can impair the polymerization ability of non-fluorinated acrylate monomers, thereby reducing the polymer backbone's ability to encapsulate electrolytes. Controlling the mass ratio of non-fluorinated acrylate monomers to fluorinated ester monomers within the aforementioned range helps to improve both the polymer's oxidation resistance and its encapsulation ability with electrolytes.

[0031] In one embodiment of this application, the above-mentioned gel polymer electrolyte composition further includes 0.01 to 10% of additives. Preferably, the additives are 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. More preferably, the lithium-containing compounds are selected from any one or more of lithium dioxolane borate, lithium difluorooxolane borate, lithium tetrafluoroborate, and lithium nitrate. And / or, the ester compounds are selected from any one or more of fluoroethylene carbonate, ethylene ethylene, methane disulfonate, 4-trifluoromethyl ethylene carbonate, fluoroethylene carbonate, ethylene sulfite, ethylene carbonate, propylene sulfite, propylene-1,3-sulfonyl lactone, and bis(trimethylsilyl)sulfate. And / or, the thiophene compound is 1,3,2-dioxazothiophene-2,2-dioxide. And / or, the acid anhydride is succinic anhydride; and / or, the amide is N-methyl, butylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and / or N-methyl, propylpiperidine bis(trifluoromethanesulfonyl)imide salt; and / or, the cyclic ether is 1,3-dioxane and / or 1,4-dioxane; and / or, the nitrile is adiponitrile and / or trans-butenedionitrile; and / or, the cyano-containing compound is selected from 1,2-bis(cyanoethoxy)ethane, 1,3,5- Trimethylpentanenitrile and 1,2,3-tris(2-cyanoethoxy)propane are selected from any one or more of the following: most preferably, the additive is methylene methane disulfonate; 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 di(oxalato)borate, lithium di(fluorooxalato)borate, lithium tetra(fluoroborate), lithium tri(fluoromethanesulfonate), and lithium di(fluorophosphate); preferably, the lithium salt is lithium bis(fluorosulfonyl)imide.

[0032] The addition of additives helps to further improve the overall performance of gel polymer electrolytes, especially the addition of methylene methane disulfonate, which helps to promote the formation of the SEI film, reduce the internal resistance of the battery, and improve the battery performance at high rates. Controlling the type of lithium salt within the above-mentioned range helps to improve the solubility of lithium salt in organic solvents, especially lithium bis(fluorosulfonyl)imide, which has high solubility in organic solvents and has low charge transfer resistance and good SEI film formation ability, thus helping to further improve the cycle stability of lithium metal batteries.

[0033] In one embodiment of this application, the above-mentioned gel polymer electrolyte composition, by mass fraction, comprises 83% organic solvent, 13% lithium salt, 1% additives, and 3% polymeric monomers, wherein the organic solvent is... The combination, and The mass ratio is 17:50:16, the lithium salt is lithium difluorosulfonylimide, the additive is methane disulfonate methylene ester, and the polymer monomer is a combination of ethoxylated trimethylolpropane triacrylate and trifluoroethyl methacrylate, with a mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate of 1:0.3.

[0034] In one embodiment of this application, the above-mentioned gel polymer electrolyte composition, by mass fraction, comprises 81% organic solvent, 13% lithium salt, 1% additives, and 5% polymeric monomers, wherein the organic solvent is... The combination, and The mass ratio is 17:50:14, the lithium salt is lithium difluorosulfonylimide, the additive is methane disulfonate methylene ester, and the polymer monomer is a combination of ethoxylated trimethylolpropane triacrylate and trifluoroethyl methacrylate, with the mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate being 1:0.5.

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

[0036] Since the above-mentioned gel polymer electrolyte is prepared by the gel polymer electrolyte composition of this application through a polymerization reaction, 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 surface of the positive and negative electrodes.

[0037] In one embodiment of this application, the above-mentioned gel polymer electrolyte is prepared by mixing a gel polymer electrolyte composition with an initiator and then undergoing a polymerization reaction; preferably, the initiator accounts for 0.5-1% of the polymer monomer by mass, 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 12-14h.

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

[0039] Because the lithium metal battery described above contains a gel polymer electrolyte prepared by polymerization of the gel polymer electrolyte composition of this application, the lithium metal battery exhibits excellent long-cycle performance at both room temperature and high temperature.

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

[0041] In another typical embodiment of this application, a capacity repair method for the aforementioned lithium metal battery is provided. The capacity repair method includes: testing the capacity retention rate H of the lithium metal battery; when 85% ≤ H ≤ 90%, the lithium metal battery is placed at 45-50°C for 1-2 hours and circulated for 5-10 cycles to end the capacity repair.

[0042] The above-mentioned capacity repair mechanism can only be used when the capacity retention rate of the lithium metal battery has decayed to below 90%, because when the battery capacity retention rate is still high, high temperature for capacity repair will affect battery performance and accelerate cycle failure. However, if capacity repair is performed after the capacity retention rate has decayed to below 85%, many parts of the battery are already in an irreversible state and cannot achieve a good capacity repair effect. There are several advantages to capacity repair within the above temperature range: (1) After long-term cycling, a thick electrolyte film will form on the positive and negative electrode surfaces. After high-temperature heating, some components of the film will be decomposed by heating. During the charging and discharging process, the electrolyte film is reset to obtain a thin and compact electrolyte film, reducing the overall impedance of the battery, thereby restoring some of the capacity loss caused by battery polarization. (2) At high temperature, the lithium ion migration speed of the battery can be effectively improved, which can guide the lithium ions accumulated on the negative electrode surface and restore some of the capacity loss caused by battery polarization. (3) During the cycling process, lithium metal batteries inevitably form lithium dendrites. Some dendrites will gradually grow into the interior of the gel polymer electrolyte, which poses a risk of short circuit. At high temperatures, the polymer has a self-repairing effect and can repair some of the micro-perforations caused by lithium dendrites.

[0043] In one embodiment of this application, the lithium metal battery is charged at a charging rate C1 and discharged at a discharging rate C2, and cycled in this manner. When 85% ≤ H ≤ 90%, the lithium metal battery is placed in a 45°C high-temperature chamber for two hours. In the 45°C high-temperature chamber, it is charged at a charging rate C3 and discharged at a discharging rate C4, and the cycle is repeated for 5 to 10 times. The battery is then restored to 25°C, and the capacity repair is completed. 1 ≤ C3 / C1 ≤ 1.5, 0.2 ≤ C4 / C2 ≤ 1.

[0044] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0045] Example 1

[0046] In a dry argon atmosphere, cyclic fluorocarbonate compounds are... Fluorine-free ether compounds and fluorinated ether compounds Mix thoroughly to obtain an organic solvent, then add lithium salt to the organic solvent. The additive methylene disulfonate was dissolved uniformly, and then polymerizable monomers were added. The polymerizable monomers were a mixture of fluorine-free acrylate monomers ethoxylated trimethylolpropane triacrylate and fluorinated ester monomer trifluoroethyl methacrylate in a mass ratio of 1:0.3. After stirring evenly, a gel polymer electrolyte composition was obtained. The gel polymer electrolyte composition contained 83% organic solvent, 13% lithium salt, 1% additive, 3% polymerizable monomer, and the mass ratio of cyclic fluorinated carbonate compound, fluorine-free ether compound, and fluorinated ether compound was 17:50:16.

[0047] Example 2

[0048] The difference from Example 1 is that the additives are omitted, and the mass percentage of organic solvent in the gel polymer electrolyte composition is 84%, the mass percentage of lithium salt is 13%, the mass percentage of polymer monomer is 3%, and the mass ratio of cyclic fluorocarbonate compound, non-fluorinated ether compound and fluoroether compound is 17:50:17.

[0049] Example 3

[0050] The difference from Example 1 is that the mass percentage of organic solvent in the gel polymer electrolyte composition is 81%, the mass percentage of lithium salt is 13%, the mass percentage of additives is 1%, the mass percentage of polymeric monomers is 5%, and the mass ratio of cyclic fluorocarbonate compound, non-fluorinated ether compound and fluoroether compound is 17:50:14.

[0051] Example 4

[0052] The difference from Example 1 is that the mass percentage of organic solvent in the gel polymer electrolyte composition is 85%, the mass percentage of lithium salt is 13%, the mass percentage of additives is 1%, the mass percentage of polymeric monomers is 1%, and the mass ratio of cyclic fluorocarbonate compound, non-fluorinated ether compound and fluoroether compound is 17:50:18.

[0053] Example 5

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

[0055] Example 6

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

[0057] Example 7

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

[0059] Example 8

[0060] The difference from Example 1 is that the cyclic fluorocarbonate compound is... R1 is methyl, R2 is ethyl, R3 is propyl, and R4 is fluorine; fluorine-free ether compounds are... R5 is ethyl, R6 is methyl; fluorinated ether compounds are...

[0061] Example 9

[0062] The difference from Example 1 is that the cyclic fluorocarbonate compound is... R1 is cyclohexyl, R2 is 1-butenyl, R3 is pyridyl, and R4 is fluorine; fluorine-free ether compounds are... R5 is n-butyl, R6 is n-butyl; fluoroether compounds are...

[0063] Example 10

[0064] The difference from Example 1 is that the mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate is 1:0.1.

[0065] Example 11

[0066] The difference from Example 1 is that the mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate is 1:0.5.

[0067] Example 12

[0068] The difference from Example 1 is that the mass ratio of ethoxylated trimethylolpropane triacrylate to trifluoroethyl methacrylate is 1:1.

[0069] Example 13

[0070] The difference from Example 1 is that the fluorine-free acrylate monomer is ethyl acetoacetate methacrylate, and the fluorinated ester monomer is methyl 2-fluoroacrylate.

[0071] Example 14

[0072] The difference from Example 1 is that the fluorine-free acrylate monomer is trimethylolpropane triacrylate, and the fluorinated ester monomer is methacrylate-1H,1H-perfluorooctyl ester.

[0073] Comparative Example 1

[0074] The difference from Example 1 is that the addition of cyclic fluorocarbonate compounds is omitted, and the mass percentage of fluorine-free ether compounds in the gel polymer electrolyte composition is 67%, while the mass percentage of fluorinated ether compounds is 16%.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that the addition of fluorine-free ether compounds is omitted, and the mass percentage of cyclic fluorocarbonate compounds in the gel polymer electrolyte composition is 67%, and the mass percentage of fluoroether compounds is 16%.

[0077] Comparative Example 3

[0078] The difference from Example 1 is that the addition of fluorinated ether compounds is omitted, and the mass percentage of fluorine-free ether compounds in the gel polymer electrolyte composition is 67%, while the mass percentage of cyclic fluorinated carbonate compounds is 16%.

[0079] Comparative Example 4

[0080] The difference from Example 1 is that the mass percentage of organic solvent in the gel polymer electrolyte composition is 66%, the mass percentage of lithium salt is 13%, the mass percentage of additives is 1%, the mass percentage of polymeric monomers is 20%, and the mass ratio of cyclic fluorocarbonate compound, non-fluorinated ether compound and fluoroether compound is 13:41:12.

[0081] Battery manufacturing

[0082] Lithium metal was laminated onto a copper foil current collector with a thickness of approximately 12 μm using a physical rolling process. By adjusting the roller pressure, lithium was coated on one side of the copper current collector, with a thickness controlled to approximately 50 μm. The resulting negative electrode sheet was then cut and slit. Nickel-cobalt-manganese (NCM) positive electrode active material, conductive agent (SuperP's conductive carbon), and polyvinylidene fluoride binder were mixed in a weight ratio of 97:1.4:1.6. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until homogeneous, yielding a positive electrode slurry with a solid content of 72 wt%. The positive electrode slurry was uniformly coated onto an aluminum foil current collector. After drying, it underwent cold pressing, cutting, and slitting, and was then dried under vacuum at approximately 85°C for about 4 hours to obtain the positive electrode sheet. A 15 μm thick polyethylene (PE) separator was used.

[0083] Azobisisobutyronitrile (AIBN) was added as an initiator to the gel polymer electrolyte composition prepared in the above examples and comparative examples. The mass of AIBN accounted for 0.5% of the mass of the polymer monomers to obtain a mixture. The positive electrode, separator, and lithium metal negative electrode were stacked in sequence and then stacked. After welding the tabs, the mixture was placed in the outer packaging aluminum-plastic film. The mixture was injected into the aluminum-plastic film. After vacuum sealing, standing at room temperature for 24 hours, and high-temperature polymerization at 60°C for 12 hours, in-situ polymerization was carried out to obtain the gel polymer electrolyte. The mixture underwent formation (0.02C constant current charging to 3.75V, and then 0.1C constant current charging to 4.3V), shaping, capacity testing, and other processes to obtain a soft-pack stacked lithium metal battery.

[0084] Performance testing

[0085] The prepared pouch-type stacked lithium metal batteries were subjected to cycle tests at 25°C and 45°C, respectively. For the 25°C cycle test: the lithium metal batteries were placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow them to reach a constant temperature. The batteries were then charged at a constant current of 0.2C to 4.3V, then at a constant voltage of 0.5V, and finally discharged at a constant current of 1C to 3V. This constituted one charge-discharge cycle. The initial discharge capacity was taken as 100%, and the charge-discharge cycles were repeated until the discharge capacity decreased to 80%. The number of cycles was recorded as an indicator of the cycle performance of the lithium metal batteries. For the 45°C cycle test: the lithium metal batteries were placed in a 45°C constant temperature chamber and left to stand for 30 minutes to allow them to reach a constant temperature. The batteries were then charged at a constant current of 0.2C to 4.3V, then at a constant voltage of 0.5V, and finally discharged at a constant current of 1C to 3V. This constituted one charge-discharge cycle. The initial discharge capacity was taken as 100%, and repeated charge-discharge cycles were performed until the discharge capacity decayed to 80%. The test was then stopped, and the number of cycles was recorded as an indicator to evaluate the cycle performance of lithium metal batteries.

[0086] Furthermore, the following capacity repair method was used during the testing process:

[0087] Capacity restoration method 1: When the lithium metal battery capacity retention rate is 85%, remove the battery and place it in a 45°C high-temperature chamber. Charge it at a charging rate of 0.3C and discharge it at a discharging rate of 1C. Repeat this cycle 5 times. Then, restore the battery to room temperature. The capacity restoration is now complete.

[0088] Capacity repair method two: When the lithium metal battery capacity retention rate is 90%, remove the battery and place it in a 45°C high-temperature chamber. Charge it at a charging rate of 0.3C and discharge it at a discharging rate of 1C. Repeat this cycle 5 times. Then, restore the battery to room temperature. The capacity repair is now complete.

[0089] Capacity repair method 3: When the lithium metal battery capacity retention rate is 85%, remove the battery and place it in a 45°C high-temperature chamber. Charge it at a charging rate of 0.2C and discharge it at a discharging rate of 0.2C. Repeat this cycle 5 times. Then, restore the battery to room temperature. The capacity repair is now complete.

[0090] Capacity repair method four: When the lithium metal battery capacity retention rate is 60%, remove the battery and place it in a 45°C high-temperature chamber. Charge it at a charging rate of 0.2C and discharge it at a discharging rate of 0.2C. Repeat this cycle 5 times. Then, restore the battery to room temperature. The capacity repair is now complete.

[0091] Fifth method for capacity repair: When the lithium metal battery capacity retention rate is 85%, remove the battery and place it in a 60°C high-temperature chamber. Charge it at a charging rate of 0.2C and discharge it at a discharging rate of 0.2C. Repeat this cycle 5 times. Then, restore the battery to room temperature. The capacity repair is now complete.

[0092] The results of the cycle tests of the above lithium metal batteries at 25°C and 45°C are shown in Table 1.

[0093] Table 1

[0094]

[0095]

[0096] Table 1 shows the test results of the capacity repair method of the batteries prepared in Example 1 and Example 2. It can be seen that the addition of additives improves the cycle performance of lithium metal batteries. This is because the additives facilitate lithium deposition when forming a film on the negative electrode.

[0097] The test results of the batteries prepared in Example 1 with capacity repair methods 1, 2, 3, 4 and 5 show that if an incorrect capacity repair method is used, the cycle performance of the battery will be greatly affected.

[0098] The test results of the capacity repair method in Comparative Examples 1-3 and Example 1 show that a combination of three compounds—cyclic fluorocarbonate compounds, non-fluorinated ether compounds, and fluoroether compounds—is required to achieve a better cycling effect.

[0099] The test results of the capacity repair method in Comparative Example 4 and Example 1 show that if too much copolymer monomer is added and the electrolyte is too solidified, the kinetic performance of the battery will decrease, which will greatly affect the battery's room temperature cycle performance.

[0100] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0101] The presence of monomers facilitates the formation of a stable and uniform copolymer framework during subsequent polymerization reactions. This framework not only provides physical structural support but also effectively restricts the free flow of electrolyte, thereby inhibiting lithium dendrite formation, reducing the risk of internal short circuits, and improving battery safety. The main role of fluorine-free acrylate monomers in the polymerization process is to form the gel polymer backbone. The addition of fluorinated ester monomers helps improve the oxidation resistance of the backbone at the positive electrode and can also form a LiF-rich SEI film at the negative electrode, thus contributing to improved long-cycle stability of lithium metal batteries. Too low a monomer ratio may lead to insufficient mechanical strength of the gel polymer electrolyte, while too high a ratio may increase the viscosity of the gel, affecting lithium-ion mobility. Controlling the monomer ratio within the aforementioned range helps to ensure that the formed gel polymer electrolyte has suitable mechanical strength and good ionic conductivity, balancing kinetic performance and chemical stability. The presence of cyclic fluorocarbonate compounds and fluoroether compounds in the organic solvent helps the electrolyte form a LiF-component SEI film on the negative electrode surface, and this organic solvent is more oxidation-resistant on the positive electrode side, which is beneficial for improving the cycle performance of lithium metal batteries. Furthermore, cyclic fluorocarbonate compounds exhibit excellent solubility for lithium salts and can form C- and O-containing organic polymers (SEI) on the negative electrode surface. When combined with inorganic LiF and Li3N, they demonstrate superior stability. Cyclic fluorocarbonate compounds have high viscosity, while non-fluorinated ether compounds and fluoroether compounds have lower viscosity. The presence of non-fluorinated ether compounds helps regulate electrolyte viscosity and reduces electrolyte reactivity at the negative electrode, thus improving the long-cycle performance of lithium metal batteries. Fluorinated ether compounds, in addition to helping regulate electrolyte viscosity, exhibit good stability at the lithium metal negative electrode, rarely reacting with reactive lithium metal, and can form a tight protective film at the positive electrode. Controlling the mass percentage of organic solvents within the aforementioned range helps them form stable SEI films at both the positive and negative electrodes, thereby improving the cycle stability of lithium metal batteries. The gel polymer electrolyte formed by the gel polymer electrolyte composition of this application helps to suppress the growth of lithium dendrites, form a stable SEI film on the positive and negative electrodes of the battery, and reduce side reactions, thereby helping to improve the cycle stability and safety of lithium metal batteries at room temperature and high temperature.

[0102] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gel polymer electrolyte composition, characterized in that, The gel polymer electrolyte composition comprises, by mass fraction: 1~10% of polymeric monomers; 60-85% organic solvents; and The remaining lithium salt; The organic solvent is a combination of cyclic fluorocarbonate compounds, non-fluorinated ether compounds, and fluorinated ether compounds, wherein the mass ratio of the cyclic fluorocarbonate compounds, the non-fluorinated ether compounds, and the fluorinated ether compounds is (1~40):(1~70):(1~40); the polymerizable monomer is a combination of non-fluorinated acrylate monomers and fluorinated ester monomers, wherein the mass ratio of the non-fluorinated acrylate monomers to the fluorinated ester monomers is 1:(0.1~0.5); the polymerizable monomer is capable of forming a moderately cross-linked three-dimensional network structure in the organic solvent.

2. The gel polymer electrolyte composition according to claim 1, characterized in that, The structure of the cyclic fluorocarbonate compound is as follows: R1, R2, R3, and R4 are each independently selected from hydrogen, fluorine, fluorine-substituted or unsubstituted C1~C4 atoms. 12 Alkyl, fluorinated or unsubstituted C3~C 12 Cycloalkyl, fluorinated or unsubstituted C2~C 12 Alkenyl groups, and fluorinated or unsubstituted C3~C groups 12 Any one of the heterocyclic groups, and at least one of R1, R2, R3, and R4 is selected from the fluorine, the fluorine-substituted C1~C. 12 Alkyl groups, fluorine-substituted C3-C groups 12 cycloalkyl groups, fluorinated C2-C groups 12 Alkenyl and fluorine-substituted C3~C 12 Any of the heterocyclic groups.

3. The gel polymer electrolyte composition according to claim 2, characterized in that, R1, R2, R3, and R4 are each independently selected from any one of the following: hydrogen, fluorine, fluorinated or unsubstituted C1-C6 alkyl, fluorinated or unsubstituted C3-C6 cycloalkyl, fluorinated or unsubstituted C2-C6 alkenyl, and fluorinated or unsubstituted C3-C6 heterocyclic group. At least one of R1, R2, R3, and R4 is selected from any one of the following: fluorine, fluorinated C1-C6 alkyl, fluorinated C3-C6 cycloalkyl, fluorinated C2-C6 alkenyl, and fluorinated C3-C6 heterocyclic group.

4. The gel polymer electrolyte composition according to claim 3, characterized in that, R1, R2, R3 and R4 are each independently selected from any one of hydrogen, fluorine, and fluorine-substituted or unsubstituted C1-C3 alkyl groups, and at least one of R1, R2, R3 and R4 is selected from any one of fluorine and fluorine-substituted C1-C3 alkyl groups.

5. The gel polymer electrolyte composition according to claim 4, characterized in that, R1, R2, R3 and R4 are each independently hydrogen or fluorine, and one of R1, R2, R3 and R4 is fluorine.

6. The gel polymer electrolyte composition according to any one of claims 1 to 5, characterized in that, The structural formula of the non-fluorinated ether compound is as follows: Among them, R5 and R6 are each independently selected from C1 to C2. 10 Any one of the alkyl groups.

7. The gel polymer electrolyte composition according to claim 6, characterized in that, R5 and R6 are each independently selected from any one of C1 to C6 alkyl groups.

8. The gel polymer electrolyte composition according to claim 7, characterized in that, R5 and R6 are each independently selected from any one of C1 to C3 alkyl groups.

9. The gel polymer electrolyte composition according to claim 8, characterized in that, R5 and R6 are each independently methyl.

10. The gel polymer electrolyte composition according to any one of claims 1 to 5, characterized in that, The structure of the fluorinated ether compound is as follows: Among them, R7 and R8 are each independently selected from C1 to C2. 10 Halogenated alkyl groups and C2~C 10 Any of the haloalkenyl groups.

11. The gel polymer electrolyte composition according to claim 10, characterized in that, R7 and R8 are each independently selected from any one of C1-C6 haloalkyl and C2-C6 haloalkenyl groups.

12. The gel polymer electrolyte composition according to claim 11, characterized in that, R7 and R8 are each independently selected from any one of C1 to C3 haloalkyl groups.

13. The gel polymer electrolyte composition according to claim 12, characterized in that, R7 and R8 are each independently for .

14. The gel polymer electrolyte composition according to any one of claims 1 to 5, characterized in that, The fluorine-free acrylate monomers are selected from any one or more of ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, ethyl acetoacetate methacrylate, methyl methacrylate, ethyl acrylate, and decaacrylate. And / or, the fluorinated ester monomers are selected from any one or more of trifluoroethyl methacrylate, allyl trifluoroacetate, fluoroethylene carbonate, hexafluorobutyl methacrylate, hexafluoroisobutyl methacrylate, 1H,1H-perfluorooctyl methacrylate, methyl 2-trifluoromethyl methacrylate, methyl 2-fluoroacrylate, and pentafluorophenol acrylate.

15. The gel polymer electrolyte composition according to claim 14, characterized in that, The fluorine-free acrylate monomer is ethoxylated trimethylolpropane triacrylate; and / or, the fluorinated ester monomer is trifluoroethyl methacrylate.

16. The gel polymer electrolyte composition according to any one of claims 1 to 5, characterized in that, The gel polymer electrolyte composition further includes 0.01-10% of additives, wherein the additives are 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; 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 dioxalateborate, lithium difluorooxalateborate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and lithium difluorophosphate.

17. The gel polymer electrolyte composition according to claim 16, characterized in that, The lithium-containing compound is selected from any one or more of lithium dioxolane borate, lithium difluorooxolane borate, lithium tetrafluoroborate, and lithium nitrate. And / or, the ester compound is selected from any one or more of fluoroethylene carbonate, ethylene ethylene ester, methane disulfonate, 4-trifluoromethyl ethylene carbonate, fluoroethylene carbonate, ethylene sulfite, ethylene carbonate, propylene sulfite, propylene-1,3-sulfonyl lactone, and bis(trimethylsilyl)sulfate. And / or, the thiophene compound is 1,3,2-dioxazothiophene-2,2-dioxide; And / or, the acid anhydride compound is succinic anhydride; And / or, the amide compound is N-methyl, butylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and / or N-methyl, propylpiperidine 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 trans-butenedionitrile; And / or, the cyano-containing compound is selected from any one or more of 1,2-bis(cyanoethoxy)ethane, 1,3,5-pentanetricarbonyl nitrile, and 1,2,3-tris(2-cyanoethoxy)propane.

18. The gel polymer electrolyte composition according to claim 17, characterized in that, The additive is methylene methane disulfonate.

19. A gel polymer electrolyte, characterized in that, The gel polymer electrolyte is prepared by polymerization reaction from the gel polymer electrolyte composition according to any one of claims 1 to 18.

20. 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 19.

21. A method for restoring the capacity of a lithium metal battery according to claim 20, characterized in that, The capacity restoration method includes: 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 then circulated for 5 to 10 cycles at 45 to 50°C to complete the capacity repair.

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