Gel polymer electrolyte, preparation method thereof and secondary battery
By preparing gel polymer electrolytes containing phosphorus groups and oxygen functional groups, the problems of easy leakage and poor cycle stability of liquid electrolytes were solved, thereby improving the safety and stability of secondary batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- MICROVAST POWER SYST CO LTD
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-17
AI Technical Summary
The liquid electrolyte in existing secondary batteries is prone to leakage, resulting in poor safety performance and low cycle stability. Especially when using lithium metal anodes or a design without anodes, the reaction between the liquid electrolyte and the anode is aggravated, leading to thermal runaway and lithium dendrite formation.
The gel polymer electrolyte comprises a polymer matrix, lithium salt, and solvent. By mixing the polymer monomers, lithium salt, and solvent in an inert atmosphere, a gel electrolyte is formed. The polymer matrix contains phosphorus-containing and oxygen-containing functional groups, which can release phosphorus free radicals to retard flame and inhibit lithium dendrites during thermal runaway. The flexible chain segments buffer volume changes and ensure the integrity of the solid electrolyte interface film.
It reduces the risk of leakage in secondary batteries, improves thermal and cycle stability, and reduces irreversible capacity loss by suppressing lithium dendrites and maintaining the integrity of the solid electrolyte interface film.
Smart Images
Figure CN121885751A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrolyte materials technology, and more specifically, to a gel polymer electrolyte, its preparation method, and a secondary battery. Background Technology
[0002] With the continuous growth of energy demand and the increasing awareness of environmental protection, the safety, cycle stability and energy density of secondary batteries, as a key component of portable electronic devices, electric vehicles and large-scale energy storage systems, have become the focus of research.
[0003] Liquid electrolytes are typically composed of organic solvents and lithium salts. In practical applications, liquid electrolytes for secondary batteries mainly present the following two problems:
[0004] (1) Safety issues of secondary batteries: batteries may leak when subjected to external impact.
[0005] (2) Cyclic stability issues of secondary batteries. For example, using lithium metal anode or cell design without anode can significantly improve battery energy density, but at the same time, it faces problems such as low cycle stability caused by the intensified reaction between liquid electrolyte and anode. Summary of the Invention
[0006] The main objective of this invention is to provide a gel polymer electrolyte, its preparation method, and a secondary battery, in order to solve the problems in the prior art where the liquid electrolyte of the secondary battery is prone to leakage, resulting in poor battery safety performance; battery thermal runaway caused by electrolyte solvent evaporation and electrolyte side reactions; and poor cycle stability due to the easy formation of lithium dendrites.
[0007] To achieve the above objectives, the present invention provides a gel polymer electrolyte comprising a polymer matrix, a lithium salt, and a solvent, wherein the polymer matrix is selected from one or more compounds with the structure shown in formula (I):
[0008] (I),
[0009] Among them, R1, R2, R3, R4 and R5 are each independently selected from hydrogen atoms, halogens, nitro groups, cyano groups, and C1 to C5 atoms. 10 Alkyl or halogen-substituted C1-C 10 Alkyl or nitro-substituted C6-C 12 aryl or halogen-substituted C6-C 12 aryl, C1-C 10 alkoxy groups, C1-C 10The alkyl ester group or -C(=O)-NR'2, wherein R' is selected from C2 to C4 alkyl groups; X represents a carbon atom, and y is 1 or 2; or, X represents an oxygen atom, and y is 0; n is any integer from 1 to 1000; m is 1 or 2.
[0010] In one embodiment, the weight-average molecular weight of the polymer matrix is 1,000 to 100,000.
[0011] In one embodiment, R1 is selected from C2 to C7 alkyl, nitro-substituted phenyl or hydrogen atom; R2 is selected from hydrogen atom, C2 to C4 alkyl ester or -C(=O)-NR'2, wherein R' is selected from C2 to C4 alkyl; R3 is selected from hydrogen atom; R4 is selected from C1 to C8 alkyl or hydrogen atom; R5 is selected from hydrogen atom.
[0012] In one embodiment, X is an oxygen atom; y is 0; R1 is selected from ethyl, nitro-substituted phenyl, or hydrogen atom; R3 is selected from hydrogen atom; R4 is selected from methyl or hydrogen atom; R5 is selected from hydrogen atom; m is 1 or 2; or, X is a carbon atom; y is 1 or 2; R1 is selected from ethyl; R2 is selected from hydrogen atom, ethyl ester group, or -C(=O)N(C2H5)2; R3 is selected from hydrogen atom; R4 is selected from hydrogen atom; R5 is selected from hydrogen atom.
[0013] In one embodiment, the polymer matrix is selected from one or more of compounds 1 to 6:
[0014] , , ,
[0015] , , .
[0016] As one implementation method, the content of the polymer matrix is 1 wt% to 25 wt%, based on the mass percentage of the gel polymer electrolyte.
[0017] In one embodiment, the mass ratio of lithium salt to polymer matrix is (0.625-25):1.
[0018] In one embodiment, the solvent is selected from ester solvents and / or ether solvents.
[0019] To achieve the above objectives, another aspect of this application provides a method for preparing the gel polymer electrolyte provided in this application. The method includes: mixing a polymeric monomer, a lithium salt, and a solvent in an inert atmosphere to obtain a precursor solution, and then performing a polymerization reaction to obtain the gel polymer electrolyte; wherein the polymeric monomer is selected from one or more compounds with the structure shown in formula (II).
[0020] (II)
[0021] Among them, R1, R2, R3, R4 and R5 are each independently selected from hydrogen atoms, halogens, nitro groups, cyano groups, and C1 to C5 atoms. 10 Alkyl or halogen-substituted C1-C 10 Alkyl or nitro-substituted C6-C 12 aryl or halogen-substituted C6-C 12 aryl, C1-C 10 alkoxy groups, C1-C 10 The alkyl ester group or -C(=O)-NR'2, wherein R' is selected from C2 to C4 alkyl groups;
[0022] X represents a carbon atom, and y takes the value 1 or 2; or, X represents an oxygen atom, and y takes the value 0.
[0023] n can be any integer from 1 to 1000;
[0024] m can be 1 or 2.
[0025] In one embodiment, R1 is selected from C2 to C7 alkyl, nitro-substituted phenyl or hydrogen atom; R2 is selected from hydrogen atom, C2 to C4 alkyl ester or -C(=O)-NR'2, wherein R' is selected from C2 to C4 alkyl; R3 is selected from hydrogen atom; R4 is selected from C1 to C8 alkyl or hydrogen atom; R5 is selected from hydrogen atom.
[0026] In one embodiment, X is an oxygen atom; y is 0; R1 is selected from ethyl, nitro-substituted phenyl, or hydrogen atom; R3 is selected from hydrogen atom; R4 is selected from methyl or hydrogen atom; R5 is selected from hydrogen atom; m is 1 or 2; or, X is a carbon atom; y is 1 or 2; R1 is selected from ethyl; R2 is selected from hydrogen atom, ethyl ester group, or -C(=O)N(C2H5)2; R3 is selected from hydrogen atom; R4 is selected from hydrogen atom; R5 is selected from hydrogen atom.
[0027] In one embodiment, the polymerizing monomer is selected from one or more of compounds D1 to D6:
[0028] , , ,
[0029] , , .
[0030] As one embodiment, the precursor solution also includes a crosslinking agent; the preparation method of the above-mentioned gel polymer electrolyte includes: mixing the polymer monomer, lithium salt, crosslinking agent and solvent in an inert atmosphere to obtain a precursor solution, and carrying out a polymerization reaction to obtain a gel polymer electrolyte.
[0031] In one embodiment, the crosslinking agent is an acrylate crosslinking agent, selected from one or more of methyl methacrylate, ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, trimethylolpropane trimethacrylate, di(trimethylolpropane)tetraacrylate, and ethoxylated trimethylolpropane triacrylate.
[0032] As one implementation method, the content of the sum of the mass of the polymer monomer and the crosslinking agent is 1.5wt% to 20wt%, based on the mass percentage of the total mass of the polymer monomer, lithium salt and solvent.
[0033] In one implementation method, the molar ratio of polymeric monomer to crosslinking agent is (1-99):(99-1).
[0034] As one embodiment, the precursor solution further includes a crosslinking agent initiator; the crosslinking agent initiator is selected from one or more of 2,2-azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, and benzoyl peroxide; the preparation method of the above-mentioned gel polymer electrolyte includes: mixing the polymer monomer, lithium salt, crosslinking agent, crosslinking agent initiator, and solvent in an inert atmosphere to obtain a precursor solution, and carrying out a polymerization reaction to obtain a gel polymer electrolyte.
[0035] As one implementation method, the content of the crosslinking agent initiator is 0.02wt% to 1wt%, based on the mass percentage of the crosslinking agent.
[0036] In one implementation method, the mass ratio of polymeric monomer to lithium salt is (0.00015 to 1.6):1.
[0037] In one implementation method, the polymerization reaction temperature is 50℃~100℃; the reaction time is 3h~24h.
[0038] Another aspect of this application provides a secondary battery, including a positive electrode, a negative electrode, and a gel electrolyte disposed between the positive electrode and the negative electrode, wherein the gel electrolyte is selected from the gel polymer electrolyte provided in this application.
[0039] By applying the technical solution of this application, the gel polymer electrolyte provided by this application is in gel form, which can reduce the risk of leakage of secondary batteries compared with liquid electrolyte.
[0040] Furthermore, the polymer matrix of the gel polymer electrolyte provided in this application contains repeating units with phosphorus-containing groups (as shown in the n-corresponding chain segment in the structure of formula (I)). These units can release phosphorus free radicals when the battery experiences thermal runaway, thereby exerting their flame-retardant properties and improving the thermal stability of the secondary battery. At the same time, the polymer matrix contains abundant oxygen-containing functional groups, which can promote the uniform and directional deposition of lithium, thereby suppressing lithium dendrites and improving the cycle stability of the secondary battery.
[0041] In addition, the flexible segments and framework of the polymer matrix can effectively buffer the huge volume changes of the negative electrode material during the charging and discharging process of the secondary battery, thereby ensuring the integrity of the solid electrolyte interphase (SEI) membrane, reducing irreversible capacity loss, and further improving the cycle stability of the secondary battery. Detailed Implementation
[0042] 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.
[0043] As described in the background section, existing liquid electrolytes in secondary batteries suffer from problems such as easy leakage leading to poor battery safety, electrolyte solvent evaporation and electrolyte side reactions causing battery thermal runaway, and easy formation of lithium dendrites leading to poor cycle stability. To address these technical problems, the first aspect of this application provides a gel polymer electrolyte comprising a polymer matrix, a lithium salt, and a solvent, wherein the polymer matrix is selected from one or more compounds with the structure shown in formula (I):
[0044] (I),
[0045] Among them, R1, R2, R3, R4 and R5 are each independently selected from hydrogen atoms, halogens, nitro groups, cyano groups, and C1 to C5 atoms. 10 Alkyl or halogen-substituted C1-C 10 Alkyl or nitro-substituted C6-C 12 aryl or halogen-substituted C6-C 12 aryl, C1-C 10 alkoxy groups, C1-C 10 The alkyl ester group or -C(=O)-NR'2, wherein R' is selected from C2 to C4 alkyl groups; X represents a carbon atom, and y is 1 or 2; or, X represents an oxygen atom, and y is 0; n is any integer from 1 to 1000; m is 1 or 2.
[0046] Compared to liquid electrolytes, the gel polymer electrolyte provided in this application is gel-like, which is less prone to leakage and can reduce the risk of leakage in secondary batteries.
[0047] Furthermore, the polymer matrix of the gel polymer electrolyte provided in this application contains repeating units containing phosphorus groups (i.e., the chain segment corresponding to n in the structure shown in formula (I)). These units can release phosphorus free radicals when the battery experiences thermal runaway, thereby exerting their flame-retardant properties and improving the thermal stability of the secondary battery. At the same time, the repeating units containing oxygen functional groups in the polymer matrix can promote the uniform and directional deposition of lithium, thereby suppressing lithium dendrites and improving the cycle stability of the secondary battery.
[0048] In addition, the flexible segments and framework of the polymer matrix can effectively buffer the huge volume changes of the negative electrode material during the charging and discharging process of the secondary battery, thereby ensuring the integrity of the solid electrolyte interphase (SEI) membrane, reducing irreversible capacity loss, and improving the cycle stability of the secondary battery.
[0049] In one embodiment, the weight-average molecular weight of the polymer matrix is 1,000 to 100,000, or 2,000 to 90,000, or 3,000 to 80,000, or 4,000 to 70,000, or 5,000 to 60,000, or 6,000 to 50,000, or 7,000 to 40,000, or 8,000 to 30,000, or 9,000 to 20,000, or 10,000 to 15,000. The weight-average molecular weight of the polymer matrix includes, but is not limited to, the range mentioned above. Limiting it to this range is beneficial in two ways: firstly, it allows the phosphorus-containing repeating units to release phosphorus free radicals during thermal runaway, thereby enhancing flame retardant properties; secondly, it allows the oxygen-containing functional groups to promote uniform and directional lithium deposition, thus suppressing lithium dendrites and improving the cycle stability of the secondary battery. On the other hand, its flexible segments and framework can effectively buffer the volume changes of the negative electrode material during charging and discharging, which is beneficial in improving the integrity of the SEI film, reducing irreversible capacity loss, and improving the cycle stability of the secondary battery.
[0050] In one embodiment, R1 includes, but is not limited to, C2-C7 alkyl groups, nitro-substituted phenyl groups, or hydrogen atoms; R2 includes, but is not limited to, hydrogen atoms, C2-C4 alkyl ester groups, or -C(=O)-NR'2, wherein R' includes, but is not limited to, C2-C4 alkyl groups; R3 includes, but is not limited to, hydrogen atoms; R4 includes, but is not limited to, C1-C8 alkyl groups or hydrogen atoms; and R5 includes, but is not limited to, hydrogen atoms.
[0051] Compared to other types, using the above-mentioned substituent groups (i.e., limiting the types of R1, R2, R3, R4 and R5 to the above range) is beneficial for monomers to polymerize under milder conditions, obtain structurally stable polymer products, and thus obtain polymer matrices with the structure shown in formula (I), which is beneficial for improving the safety, cycle stability and thermal stability of secondary batteries.
[0052] In one embodiment, X is an oxygen atom; y is 0; R1 includes, but is not limited to, ethyl, nitro-substituted phenyl, or hydrogen atom; R3 includes, but is not limited to, hydrogen atom; R4 includes, but is not limited to, methyl or hydrogen atom; R5 includes, but is not limited to, hydrogen atom; m is 1 or 2; or, X is a carbon atom; y is 1 or 2; R1 includes, but is not limited to, ethyl; R2 includes, but is not limited to, hydrogen atom, ethyl ester group, or -C(=O)N(C2H5)2; R3 includes, but is not limited to, hydrogen atom; R4 includes, but is not limited to, hydrogen atom; R5 includes, but is not limited to, hydrogen atom.
[0053] Compared to other types, using R1, R3, R4 and R5 as described above is beneficial for monomers to polymerize under milder conditions, resulting in structurally stable polymer products and thus obtaining a polymer matrix with the structure shown in formula (I).
[0054] In one embodiment, the polymer matrix includes, but is not limited to, one or more of compounds 1 to 6:
[0055] , , ,
[0056] , , .
[0057] Using the aforementioned specific types of polymer matrices has several advantages. First, it allows for better utilization of the phosphorus-containing repeating units to release phosphorus free radicals during thermal runaway, thereby enhancing flame retardant properties. It also helps utilize oxygen-containing functional groups to promote uniform and directional lithium deposition, thus suppressing lithium dendrite formation and improving the cycle stability of the secondary battery. Second, its flexible segments and framework can effectively buffer the volume changes of the negative electrode material during charging and discharging, which helps improve the integrity of the SEI film, reduce irreversible capacity loss, and enhance the cycle stability of the secondary battery.
[0058] In one embodiment, the polymer matrix content, based on the mass percentage of the gel polymer electrolyte, is 1 wt% to 25 wt%; or 5 wt% to 15 wt%; or 8 wt% to 12 wt%. The polymer matrix content includes, but is not limited to, the above ranges. Limiting it within these ranges is beneficial for balancing the mechanical stability and ionic conductivity of the gel polymer electrolyte, improving the lithium-ion transport efficiency of the secondary battery during charging and discharging, and also helps to suppress the formation of lithium dendrites and reduce side reactions, thereby improving the cycle stability and safety of the secondary battery. Specifically, the polymer matrix content can be 25 wt%, 24 wt%, 23 wt%, 22 wt%, 21 wt%, 20 wt%, 19 wt%, 18 wt%, 17 wt%, 16 wt%, 15 wt%, 14 wt%, 13 wt%, 12 wt%, 11 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3.5 wt%, 2 wt%, or 1 wt%, or any range of two of the above values.
[0059] In one embodiment, the mass ratio of lithium salt to polymer matrix is (0.625–25):1; or (1–5):1; or (5–10):1; or (10–15):1; or (15–20):1; or (20–25):1. The mass ratio of lithium salt to polymer matrix includes, but is not limited to, the above ranges. Limiting it to these ranges is beneficial for improving the ionic conductivity and mechanical stability of the gel polymer electrolyte, thereby improving the lithium-ion transport efficiency of the secondary battery during charge and discharge. It also helps to suppress the formation of lithium dendrites and reduce side reactions, thus improving the cycle stability and safety of the secondary battery. Specifically, the mass ratio of lithium salt to polymer matrix can be 0.625:1, 1:1, 5:1, 10:1, 15:1, 20:1, or 25:1, or any two of the above ratios within a range.
[0060] In one embodiment, the lithium salt includes, but is not limited to, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO2)2, LiN(CF3SO2)2, and LiN(FSO2)2. One or more of LiCl and LiI, wherein x and z are each independent natural numbers between 1 and 4.
[0061] Compared to other types, the lithium salts mentioned above are advantageous in two ways: firstly, they can play an initiator role in the polymerization reaction, enabling the polymer matrix to undergo in-situ polymerization; secondly, they can provide a source of lithium ions, thereby improving the electrochemical capacity of secondary batteries.
[0062] In one embodiment, the solvent includes, but is not limited to, ester solvents and / or ether solvents; ester solvents include, but are not limited to, one or more of halocarbonates, ethylene carbonate, vinylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate (FEC), trimethyl phosphate (TMP), triethyl phosphate (TEP), and vinylene carbonate (VC); ether solvents include, but are not limited to, one or more of tetrahydrofuran (THF), fluorotetrahydrofuran, diethylene glycol dimethyl ether (DGM), and triethylene glycol dimethyl ether (TGM). Compared to other types, using the above-mentioned solvents is beneficial to improving the compatibility of the lithium salt, polymer matrix, and solvent, allowing the gel polymer electrolyte to better perform its function.
[0063] A second aspect of this application also provides a method for preparing the gel polymer electrolyte provided in this application. The method includes: mixing a polymeric monomer, a lithium salt, and a solvent in an inert atmosphere to obtain a precursor solution, and then performing a polymerization reaction to obtain the gel polymer electrolyte; wherein the polymeric monomer is selected from one or more compounds with the structure shown in formula (II).
[0064] (II)
[0065] Among them, R1, R2, R3, R4 and R5 are each independently selected from hydrogen atoms, halogens, nitro groups, cyano groups, and C1 to C5 atoms. 10 Alkyl or halogen-substituted C1-C 10 Alkyl or nitro-substituted C6-C 12 aryl or halogen-substituted C6-C 12 aryl, C1-C 10 alkoxy groups, C1-C 10 The alkyl ester group or -C(=O)-NR'2, wherein R' is selected from C2 to C4 alkyl groups; X represents a carbon atom, and y is 1 or 2; or, X represents an oxygen atom, and y is 0; n is any integer from 1 to 1000; m is 1 or 2.
[0066] In the preparation method provided in this application, firstly, in an inert atmosphere (including but not limited to argon, nitrogen, or helium), the polymer monomer, lithium salt, and solvent are mixed to obtain a precursor solution; then, the polymer monomer in the precursor solution undergoes a polymerization reaction to obtain a gel polymer electrolyte, which includes a polymer matrix, a lithium salt, and a solvent. The polymer matrix is selected from compounds with the structure shown in formula (I). The product obtained after the polymerization reaction of the polymer monomer with the structure shown in formula (II) includes a polymer matrix containing repeating units with phosphorus-containing groups (i.e., the n-corresponding chain segment in the structure shown in formula (I)). These units can release phosphorus free radicals during thermal runaway of the battery, thereby exerting their flame-retardant properties and improving the thermal stability of the secondary battery. Simultaneously, the repeating units with oxygen-containing functional groups can promote the uniform and directional deposition of lithium, thereby suppressing lithium dendrites and improving the cycle stability of the secondary battery.
[0067] In addition, the flexible segments and framework of the polymer matrix can effectively buffer the huge volume changes of the negative electrode material during the charging and discharging process of the secondary battery, thereby ensuring the integrity of the solid electrolyte interphase (SEI) membrane, reducing irreversible capacity loss, and improving the cycle stability of the secondary battery.
[0068] In one embodiment, R1 includes, but is not limited to, C2-C7 alkyl, nitro-substituted phenyl or hydrogen atoms; R2 includes, but is not limited to, C2-C4 alkyl ester or -C(=O)-NR'2, wherein R' includes, but is not limited to, C2-C4 alkyl; R3 includes, but is not limited to, hydrogen atoms; R4 includes, but is not limited to, C1-C8 alkyl or hydrogen atoms; R5 includes, but is not limited to, hydrogen atoms.
[0069] In one embodiment, X is an oxygen atom; y is 0; R1 includes, but is not limited to, ethyl, nitro-substituted phenyl or hydrogen atom; R3 includes, but is not limited to, hydrogen or chlorine-substituted phenyl; R4 includes, but is not limited to, methyl or hydrogen atom; R5 includes, but is not limited to, hydrogen or chlorine-substituted phenyl; m is 1 or 2.
[0070] In another embodiment, X is a carbon atom; y is 1 or 2; R1 includes, but is not limited to, ethyl; R2 includes, but is not limited to, hydrogen atom, ethyl ester group or -C(=O)N(C2H5)2; R3 includes, but is not limited to, hydrogen atom; R4 includes, but is not limited to, hydrogen atom; R5 includes, but is not limited to, hydrogen atom.
[0071] In one embodiment, the polymerizing monomer includes, but is not limited to, one or more of compounds D1 to D6:
[0072] , , ,
[0073] , , .
[0074] In one embodiment, the precursor solution further includes a crosslinking agent; the preparation method of the above-mentioned gel polymer electrolyte includes: mixing polymeric monomers, lithium salts, crosslinking agents, and solvents in an inert atmosphere to obtain a precursor solution, and then carrying out a polymerization reaction to obtain a gel polymer electrolyte. Introducing a crosslinking agent into the precursor solution facilitates more uniform dispersion of the crosslinking agent and allows for physical crosslinking with the polymer matrix obtained from subsequent polymerization, promoting the formation of an efficient and ordered gel network structure. This, in turn, improves the stability and ionic conductivity of the gel polymer electrolyte, thereby enhancing the cycle performance and safety of the secondary battery.
[0075] To further promote the formation of the gel network structure, in one embodiment, the crosslinking agent is an acrylate crosslinking agent, including but not limited to one or more of methyl methacrylate, ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, trimethylolpropane trimethacrylate, di(trimethylolpropane)tetraacrylate and ethoxylated trimethylolpropane triacrylate.
[0076] In one embodiment, the total mass percentage of the monomer and crosslinking agent in the precursor solution is 1.5 wt% to 20 wt%; or 5 wt% to 15 wt%; or 8 wt% to 12 wt%. The total mass percentage of the monomer and crosslinking agent in the precursor solution includes, but is not limited to, the above ranges. Limiting it to these ranges is beneficial for further promoting the formation of the gel network structure, improving the stability and ionic conductivity of the gel polymer electrolyte, and thus enhancing the cycle performance and safety of the secondary battery. Specifically, the total mass percentage of the monomer and crosslinking agent can be 20 wt%, 19 wt%, 18 wt%, 17 wt%, 16 wt%, 15 wt%, 14 wt%, 13 wt%, 12 wt%, 11 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, or 3.5 wt%, or any range of two of the above values.
[0077] In one embodiment, the molar ratio of the polymeric monomer to the crosslinking agent is (1-99):(99-1); or 1:(19-9); or (3-1):(17-3); or (3-2):(7-3); or (3-17):(1-3); or (19-9):1. The molar ratio of the polymeric monomer to the crosslinking agent includes, but is not limited to, the above ranges. Limiting it to these ranges is beneficial for further promoting the formation of the gel network structure, improving the stability and ionic conductivity of the gel polymer electrolyte, and thus enhancing the cycle performance and safety of the secondary battery. Specifically, the molar ratio of the polymerizable monomer to the crosslinking agent can be 1:99, 1:85, 1:72, 1:68, 1:51, 1:47, 1:35, 1:21, 1:14, 1:9, 1:1, 9:1, 14:1, 21:1, 35:1, 47:1, 51:1, 68:1, 72:1, 85:1, or 99:1. Further, the molar ratio of the polymerizable monomer to the crosslinking agent can be 3:1, 2:1, 1:1, 1:1.5, or 1:3.
[0078] In one embodiment, the precursor solution further includes a crosslinking initiator; the preparation method of the above-mentioned gel polymer electrolyte includes: mixing the polymeric monomer, lithium salt, crosslinking agent, crosslinking initiator and solvent in an inert atmosphere to obtain a precursor solution, and carrying out a polymerization reaction to obtain the gel polymer electrolyte. The introduction of the crosslinking initiator is beneficial to improving the efficiency of gel network formation, thereby improving the mechanical strength and ionic conductivity of the gel polymer electrolyte.
[0079] To further improve the efficiency of gel network formation, in one embodiment, the crosslinking initiator includes, but is not limited to, one or more of 2,2-azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), dimethyl azobisisobutyrate (AIBME), and benzoyl peroxide (BPO).
[0080] In one embodiment, the content of the crosslinking agent initiator, based on its mass percentage as a percentage of the crosslinking agent, is 0.02 wt% to 1 wt%; or 0.1 wt% to 0.5 wt%. The percentage of the crosslinking agent initiator relative to the crosslinking agent includes, but is not limited to, the above range. Limiting it to this range is beneficial for further enhancing the mechanical strength and stability of the gel polymer electrolyte, while also improving lithium-ion transport efficiency, thus enhancing the performance and safety of the secondary battery. Specifically, the content of the crosslinking agent initiator can be 0.02 wt%, 0.05 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.48 wt%, or 0.5 wt%, or any range of two of the above values.
[0081] In one embodiment, the mass ratio of polymeric monomer to lithium salt is (0.00015–1.6):1; or (0.1–0.5):1; or (0.5–1):1; or (1–1.6):1. The mass ratio of polymeric monomer to lithium salt includes, but is not limited to, the above ranges. Limiting it to these ranges is beneficial for improving the ionic conductivity and mechanical stability of the gel polymer electrolyte, thereby improving the lithium-ion transport efficiency of the secondary battery during charging and discharging. It also helps to suppress the formation of lithium dendrites and reduce side reactions, thus improving the cycle stability and safety of the secondary battery. Specifically, the mass ratio of the polymer monomer to the lithium salt can be 0.00015:1, 0.0002:1, 0.0003:1, 0.0004:1, 0.0005:1, 0.0006:1, 0.0007:1, 0.0008:1, 0.001:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, or 0. 06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1 or 1.6:1, or any range of values consisting of any two of the above ratios.
[0082] In one embodiment, the precursor solution also includes additives. The introduction of additives helps to suppress the effects of water and HF on battery performance, protect the cathode material, and thus improve the cycle performance of the secondary battery.
[0083] To further improve battery cycle performance, in one embodiment, the additives include, but are not limited to, one or more of 1,3-propanesulfonyl lactone (1,3-PS), sulfate additives, and isocyanate additives.
[0084] In one embodiment, the additive accounts for 0.1 wt% to 10 wt% of the precursor solution by mass. Specifically, the content of the additive can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, or a range of any two of the above ratios.
[0085] In one embodiment, the polymerization reaction temperature is 50°C–100°C, or 60°C–90°C, or 70°C–80°C; the reaction time is 3h–24h, or 5h–20h, or 10h–15h. The polymerization reaction temperature and time include, but are not limited to, the above ranges. Limiting them to these ranges is beneficial for improving polymerization reaction efficiency and for forming a gel-like polymer matrix; it also helps to suppress side reactions and increase the formation rate of the polymer matrix. Specifically, the reaction temperature of the polymerization reaction can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, or 100℃, or any range of any two of the above values; the reaction time of the polymerization reaction can be 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, or 24h, or any range of any two of the above values.
[0086] A third aspect of this application also provides a secondary battery, including a positive electrode, a negative electrode, and a gel electrolyte disposed between the positive electrode and the negative electrode, wherein the gel electrolyte is selected from the gel polymer electrolytes provided in this application.
[0087] Compared to liquid electrolytes, the gel polymer electrolyte provided in this application is gel-like, which is less prone to leakage and can reduce the risk of leakage in secondary batteries.
[0088] Furthermore, the polymer matrix of the gel polymer electrolyte provided in this application contains repeating units with phosphorus-containing groups (as shown in the n-corresponding chain segment in the structure of formula (I)). These units can release phosphorus free radicals when the battery experiences thermal runaway, thereby exerting their flame-retardant properties and improving the thermal stability of the secondary battery. At the same time, the polymer matrix contains abundant repeating units with oxygen functional groups, which can promote the uniform and directional deposition of lithium, thereby suppressing lithium dendrites and improving the cycle stability of the secondary battery.
[0089] In addition, the flexible segments and framework of the polymer matrix can effectively buffer the huge volume changes of the negative electrode material during the charging and discharging process of the secondary battery, thereby ensuring the integrity of the solid electrolyte interphase (SEI) membrane, reducing irreversible capacity loss, and improving the cycle stability of the secondary battery.
[0090] In one embodiment, the above-mentioned gel polymer electrolyte can be applied to lithium metal batteries, negative electrodeless batteries, lithium-ion batteries, or sodium-ion batteries.
[0091] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.
[0092] The method for preparing a 2.7Ah dry cell in this embodiment is as follows:
[0093] (1) Weigh the positive electrode active material LiNi according to the mass ratio of 95:2:2:1 0.8 Co 0.1 Mn 0.1 O2, polyvinylidene fluoride (PVDF), conductive carbon black and vapor-grown carbon fiber (VGCF) are mixed with N-methylpyrrolidone (NMP) to obtain a positive electrode slurry. The positive electrode slurry is coated on the surface of aluminum foil and dried to obtain a positive electrode sheet.
[0094] (2) Weigh artificial graphite, carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), SP and VGCF in a mass ratio of 2:1:1:1. Mix the above materials with NMP to obtain a negative electrode slurry. Coat the negative electrode slurry onto the surface of copper foil and dry it to obtain a negative electrode sheet.
[0095] (3) A dry cell is made by using a polyethylene (PE) diaphragm and a lamination process.
[0096] It should be noted that this application does not limit the proportions or types of materials such as separators, positive electrode active materials, negative electrode active materials, binders, conductive agents, and solvents used in the manufacturing process of dry cell batteries, as long as they meet the requirements for the manufacturing and use of dry cell batteries.
[0097] Example 1
[0098] A method for preparing a secondary battery containing a gel polymer electrolyte, comprising:
[0099] (1) Under an argon protective atmosphere, 3.125g of LiPF6 was dissolved in 19.375g of solvent (the solvent was a mixed solvent of ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a mass ratio of 26.5:55:6) to obtain a lithium salt solution;
[0100] (2) 2.50g of the polymerized monomer compound D1 (X is an oxygen atom, R1 is an ethyl atom, y=0, and R3, R4 and R5 are all hydrogen atoms) are mixed with 22.5g of the lithium salt solution prepared in step (1) to obtain a precursor solution;
[0101] (3) Take the dry cell with a capacity of 2.7Ah prepared by the above scheme, inject the precursor solution obtained in step (2) into the dry cell, and let it stand at room temperature for 48h to ensure that the electrode material in the dry cell is fully wetted. Then place it in a 65℃ oven for polymerization reaction for 24h to obtain a cell containing gel polymer electrolyte.
[0102] (4) The cell containing gel polymer electrolyte obtained in step (3) above is subjected to room temperature pressure formation and capacity testing in sequence to obtain a secondary battery containing gel polymer electrolyte.
[0103] Example 2
[0104] The difference from Example 1 is that step (2) includes:
[0105] (2) 0.660g of the polymerized monomer compound D1 (X is an oxygen atom, R1 is an ethyl group, y=0, R3, R4 and R5 are all hydrogen atoms), 1.840g of crosslinking agent di(trimethylolpropane)tetraacrylate, 0.020g of crosslinking agent initiator AIBN are mixed with the lithium salt solution obtained in step (1) to obtain the precursor solution;
[0106] The remaining steps are the same as in Example 1.
[0107] Example 3
[0108] A method for preparing a secondary battery containing a gel polymer electrolyte, comprising:
[0109] (1) Under an argon protective atmosphere, 3.125g of LiPF6 was dissolved in 19.375g of solvent (the solvent was a mixed solvent of ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a mass ratio of 26.5:55:6) to obtain a lithium salt solution;
[0110] (2) 2.50g of the polymerized monomer compound D3 (X is a carbon atom, R1 is an ethyl group, y=2, R2, R3, R4 and R5 are all hydrogen atoms), 22.5g of the lithium salt solution obtained in step (1) are mixed to obtain a precursor solution;
[0111] (3) Take the 2.7Ah dry cell prepared by the above scheme (the model is the same as in Example 1), inject the precursor solution obtained in step (2) into the dry cell, and let it stand at room temperature for 48h to ensure that the electrode material in the dry cell is fully wetted. Then place it in a 65℃ oven for polymerization reaction for 24h to obtain a cell containing gel polymer electrolyte.
[0112] (4) The cell containing gel polymer electrolyte obtained in step (3) above is subjected to room temperature pressure formation and capacity testing in sequence to obtain a secondary battery containing gel polymer electrolyte.
[0113] Example 4
[0114] A method for preparing a secondary battery containing a gel polymer electrolyte, comprising:
[0115] (1) Under an argon protective atmosphere, 3.125 g of LiBF6 was dissolved in 19.375 g of solvent (diethylene glycol dimethyl ether) to obtain a lithium salt solution;
[0116] (2) 0.0005g of the polymerized monomer compound D2 (X is oxygen atom, R1 is ethyl, y=0, R3 is hydrogen atom, R4 is methyl, m is 2, R5 is hydrogen atom), 0.343g of crosslinking agent methyl methacrylate, 0.00007g of crosslinking agent initiator azobisisoheptanenitrile, 0.0229g of additive 1,3-propanesulfonyl lactone are mixed with the lithium salt solution obtained in step (1) to obtain the precursor solution;
[0117] (3) Take the dry cell with a capacity of 2.7Ah prepared by the above scheme, inject the precursor solution obtained in step (2) into the dry cell, and let it stand at room temperature for 48h to ensure that the electrode material in the dry cell is fully wetted. Then place it in a 50℃ oven for polymerization reaction for 24h to obtain a cell containing gel polymer electrolyte.
[0118] (4) The cell containing gel polymer electrolyte obtained in step (3) above is subjected to room temperature pressure formation and capacity testing in sequence to obtain a secondary battery containing gel polymer electrolyte.
[0119] Example 5
[0120] A method for preparing a secondary battery containing a gel polymer electrolyte, comprising:
[0121] (1) Under an argon protective atmosphere, 3.125g of LiAsF6 was dissolved in 19.375g of solvent (the solvent was a mixed solvent of ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a mass ratio of 26.5:55:6) to obtain a lithium salt solution;
[0122] (2) 5.000g of polymerized monomer compound D4 (X is a carbon atom, R1 is an ethyl group, y=1, R2 is an ethyl ester group, and R3, R4, and R5 are all hydrogen atoms), 0.500g of crosslinking agent pentaerythritol tetraacrylate, 0.005g of crosslinking agent initiator dimethyl azobisisobutyrate, 2.750g of vinyl sulfate additive are mixed with the lithium salt solution obtained in step (1) to obtain a precursor solution;
[0123] (3) Take the dry cell with a capacity of 2.7Ah prepared by the above scheme, inject the precursor solution obtained in step (2) into the dry cell, and let it stand at room temperature for 48h to ensure that the electrode material in the dry cell is fully wetted. Then place it in a 100℃ oven for polymerization reaction for 3h to obtain a cell containing gel polymer electrolyte.
[0124] (4) The cell containing gel polymer electrolyte obtained in step (3) above is subjected to room temperature pressure formation and capacity testing in sequence to obtain a secondary battery containing gel polymer electrolyte.
[0125] Example 6
[0126] A method for preparing a secondary battery containing a gel polymer electrolyte, comprising:
[0127] (1) Under an argon protective atmosphere, 3.125g of LiSbF6 was dissolved in 19.375g of solvent (the solvent was triethylene glycol dimethyl ether) to obtain a lithium salt solution;
[0128] (2) 2.500g of the polymerized monomer compound D5 (X is an oxygen atom, R1 is a nitro-substituted phenyl, y=0, R3, R4, and R5 are all hydrogen atoms), 1.250g of crosslinking agent ethoxylated trimethylolpropane triacrylate, 0.006g of crosslinking agent initiator AIBN, 1.250g of 3-(trifluoromethyl)phenyl isocyanate additive are mixed with the lithium salt solution obtained in step (1) to obtain a precursor solution;
[0129] (3) Take the dry cell with a capacity of 2.7Ah prepared by the above scheme, inject the precursor solution obtained in step (2) into the dry cell, and let it stand at room temperature for 48h to ensure that the electrode material in the dry cell is fully wetted. Then place it in an 80℃ oven for polymerization reaction for 10h to obtain a cell containing gel polymer electrolyte.
[0130] (4) The cell containing gel polymer electrolyte obtained in step (3) above is subjected to room temperature pressure formation and capacity testing in sequence to obtain a secondary battery containing gel polymer electrolyte.
[0131] Example 7
[0132] A method for preparing a secondary battery containing a gel polymer electrolyte, comprising:
[0133] (1) Under an argon protective atmosphere, 3.125g of LiPF6 was dissolved in 19.375g of solvent (the solvent was a mixture of vinylene carbonate and propylene carbonate in a mass ratio of 1:1) to obtain a lithium salt solution;
[0134] (2) 2.500g of the polymerized monomer compound D6 (X is a carbon atom, R1 is an ethyl group, y=1, R2 is -C(=O)N(C2H5)2, R3, R4, and R5 are all hydrogen atoms), 1.250g of crosslinking agent ethoxylated trimethylolpropane triacrylate, 0.006g of crosslinking agent initiator benzoyl peroxide, 1.250g of 2-fluoro-5-trifluoromethylphenyl isocyanate additive are mixed with the lithium salt solution obtained in step (1) to obtain a precursor solution;
[0135] (3) Take the dry cell with a capacity of 2.7Ah prepared by the above scheme, inject the precursor solution obtained in step (2) into the dry cell, and let it stand at room temperature for 48h to ensure that the electrode material in the dry cell is fully wetted. Then place it in an 80℃ oven for polymerization reaction for 10h to obtain a cell containing gel polymer electrolyte.
[0136] (4) The cell containing gel polymer electrolyte obtained in step (3) above is subjected to room temperature pressure formation and capacity testing in sequence to obtain a secondary battery containing gel polymer electrolyte.
[0137] Comparative Example 1
[0138] A method for preparing a secondary battery containing a liquid electrolyte, comprising:
[0139] (1) 3.125g of lithium salt LiPF6 was mixed with 19.375g of mixed solvent to prepare a liquid electrolyte, wherein the mixed solvent was a mixture of ethylene carbonate, diethyl carbonate and fluoroethylene carbonate in a mass ratio of 26.5:55:6.
[0140] (2) Take a dry cell with a capacity of 2.7Ah (the same model as in Example 1), inject 22.5g of the liquid electrolyte obtained in step (1) into the dry cell, and let it stand at room temperature for 48h to ensure that the electrode material in the dry cell is fully wetted, so as to obtain a cell containing electrolyte.
[0141] (3) The electrolyte-containing cells obtained in step (2) above are subjected to room temperature pressure formation and capacity testing in sequence to obtain secondary batteries.
[0142] Performance testing and results:
[0143] Cyclic stability test, nail penetration test and thermal stability test were performed on the secondary batteries prepared in all the above embodiments of this application and the secondary batteries prepared in the comparative example.
[0144] At 45°C, 0.5C rate, and a voltage range of 3.0–4.25V, the secondary batteries prepared in Examples 1 to 7 were subjected to constant current charge-discharge cycle tests on a dual-range tester (model: CT-4008-5V6A-S1, manufacturer: Shenzhen Xinwei Electronics Co., Ltd.). After 1000 charge-discharge cycles, the capacity retention rate of the secondary batteries in Examples 1 to 7 was found to be above 80%.
[0145] The secondary batteries prepared in the above embodiments of this application were subjected to nail penetration tests in accordance with GB 38031-2025 "Safety Requirements for Power Batteries for Electric Vehicles", and the test results showed that they all met the requirements.
[0146] All the secondary batteries prepared in the above embodiments did not experience thermal runaway when heated to 200°C, while the secondary battery prepared in the comparative example did experience thermal runaway when heated to 200°C. It should be noted that the thermal runaway test was specifically implemented in accordance with the safety testing standard GB 38031-2025 "Safety Requirements for Power Batteries for Electric Vehicles".
[0147] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:
[0148] Compared to liquid electrolytes, the gel polymer electrolyte provided in this application is gel-like, which is less prone to leakage and can reduce the risk of leakage in secondary batteries.
[0149] Furthermore, the polymer matrix of the gel polymer electrolyte provided in this application contains repeating units containing phosphorus groups (i.e., the chain segment corresponding to n in the structure shown in formula (I)). These units can release phosphorus free radicals when the battery experiences thermal runaway, thereby exerting their flame-retardant properties and improving the thermal stability of the secondary battery. At the same time, the polymer matrix contains abundant repeating units containing oxygen-containing functional groups, which can promote the uniform and directional deposition of lithium, thereby suppressing lithium dendrites and improving the cycle stability of the secondary battery.
[0150] In addition, the flexible segments and framework of the polymer matrix can effectively buffer the huge volume changes of the negative electrode material during the charging and discharging process of the secondary battery, thereby ensuring the integrity of the solid electrolyte interphase (SEI) membrane, reducing irreversible capacity loss, and improving the cycle stability of the secondary battery.
[0151] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.
[0152] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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, characterized in that, The gel polymer electrolyte comprises a polymer matrix, a lithium salt, and a solvent, wherein the polymer matrix is selected from one or more compounds with the structure shown in formula (I): （I）， Among them, R1, R2, R3, R4 and R5 are each independently selected from hydrogen atoms, halogens, nitro groups, cyano groups, and C1 to C5 atoms. 10 Alkyl or halogen-substituted C1-C 10 Alkyl or nitro-substituted C6-C 12 aryl or halogen-substituted C6-C 12 aryl, C1-C 10 alkoxy groups, C1-C 10 The alkyl ester group or -C(=O)-NR'2, wherein R' is selected from C2 to C4 alkyl groups; X represents a carbon atom, and y takes the value 1 or 2; or, X represents an oxygen atom, and y takes the value 0. n can be any integer from 1 to 1000; m can be 1 or 2.
2. The gel polymer electrolyte according to claim 1, characterized in that, The weight-average molecular weight of the polymer matrix is 1,000 to 100,000.
3. The gel polymer electrolyte according to claim 1, characterized in that, R1 is selected from C2-C7 alkyl, nitro-substituted phenyl, or hydrogen atom; R2 is selected from hydrogen atom, C2-C4 alkyl ester or -C(=O)-NR'2, R' is selected from C2-C4 alkyl; R3 is selected from hydrogen atom; R4 is selected from C1-C8 alkyl or hydrogen atom; R5 is selected from hydrogen atom.
4. The gel polymer electrolyte according to claim 1, characterized in that, X is an oxygen atom; y is 0; R1 is selected from ethyl, nitro-substituted phenyl, or hydrogen atom; R3 is selected from hydrogen atom; R4 is selected from methyl or hydrogen atom; R5 is selected from hydrogen atom; m is 1 or 2; or, X is a carbon atom; y is 1 or 2; R1 is selected from ethyl; R2 is selected from hydrogen atom, ethyl ester group or -C(=O)N(C2H5)2; R3 is selected from hydrogen atom; R4 is selected from hydrogen atom; R5 is selected from hydrogen atom.
5. The gel polymer electrolyte according to claim 1, characterized in that, The polymer matrix is selected from one or more of compounds 1 to 6: 、 、 、 、 、 。 6. The gel polymer electrolyte according to claim 1, characterized in that, The content of the polymer matrix is 1 wt% to 25 wt%, based on the mass percentage of the gel polymer electrolyte.
7. The gel polymer electrolyte according to claim 1, characterized in that, The mass ratio of the lithium salt to the polymer matrix is (0.625~25):
1.
8. The gel polymer electrolyte according to claim 1, characterized in that, The solvent is selected from ester solvents and / or ether solvents.
9. A method for preparing a gel polymer electrolyte according to any one of claims 1 to 8, characterized in that, The preparation method includes: In an inert atmosphere, the polymer monomer, lithium salt and solvent are mixed to obtain a precursor solution, and a polymerization reaction is carried out to obtain the gel polymer electrolyte. The polymeric monomer is selected from one or more compounds with the structure shown in formula (II): (II), Among them, R1, R2, R3, R4 and R5 are each independently selected from hydrogen atoms, halogens, nitro groups, cyano groups, and C1 to C5 atoms. 10 Alkyl or halogen-substituted C1-C 10 Alkyl or nitro-substituted C6-C 12 aryl or halogen-substituted C6-C 12 aryl, C1-C 10 alkoxy groups, C1-C 10 The alkyl ester group or -C(=O)-NR'2, wherein R' is selected from C2 to C4 alkyl groups; X represents a carbon atom, and y takes the value 1 or 2; or, X represents an oxygen atom, and y takes the value 0. n can be any integer from 1 to 1000; m can be 1 or 2.
10. The method for preparing the gel polymer electrolyte according to claim 9, characterized in that, R1 is selected from C2-C7 alkyl, nitro-substituted phenyl, or hydrogen atom; R2 is selected from hydrogen atom, C2-C4 alkyl ester or -C(=O)-NR'2, wherein R' is selected from C2-C4 alkyl; R3 is selected from hydrogen atom; R4 is selected from C1-C8 alkyl or hydrogen atom; R5 is selected from hydrogen atom.
11. The method for preparing the gel polymer electrolyte according to claim 9, characterized in that, X is an oxygen atom; y is 0; R1 is selected from ethyl, nitro-substituted phenyl, or hydrogen atom; R3 is selected from hydrogen atom; R4 is selected from methyl or hydrogen atom; R5 is selected from hydrogen atom; m is 1 or 2; or, X is a carbon atom; y is 1 or 2; R1 is selected from ethyl; R2 is selected from hydrogen atom, ethyl ester group or -C(=O)N(C2H5)2; R3 is selected from hydrogen atom; R4 is selected from hydrogen atom; R5 is selected from hydrogen atom.
12. The method for preparing the gel polymer electrolyte according to claim 9, characterized in that, The polymerizable monomer is selected from one or more compounds D1 to D6: 、 、 、 、 、 。 13. The method for preparing the gel polymer electrolyte according to claim 9, characterized in that, The precursor solution also includes a crosslinking agent; the preparation method includes: mixing the polymeric monomer, the lithium salt, the crosslinking agent and the solvent in the inert atmosphere to obtain a precursor solution, and carrying out a polymerization reaction to obtain the gel polymer electrolyte.
14. The method for preparing the gel polymer electrolyte according to claim 13, characterized in that, The crosslinking agent is an acrylate crosslinking agent, selected from one or more of methyl methacrylate, ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, trimethylolpropane trimethacrylate, di(trimethylolpropane)tetraacrylate and ethoxylated trimethylolpropane triacrylate.
15. The method for preparing the gel polymer electrolyte according to claim 13, characterized in that, The content of the polymeric monomer and the crosslinking agent, based on the mass percentage of the total mass of the precursor solution, is 1.5 wt% to 20 wt%; and / or, The molar ratio of the polymer monomer to the crosslinking agent is (1-99):(99-1).
16. The method for preparing the gel polymer electrolyte according to claim 13, characterized in that, The precursor solution further includes a crosslinking initiator; the crosslinking initiator is selected from one or more of 2,2-azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, and benzoyl peroxide; the preparation method includes: in the inert atmosphere, mixing the polymer monomer, the lithium salt, the crosslinking agent, the crosslinking initiator, and the solvent to obtain the precursor solution, and carrying out a polymerization reaction to obtain the gel polymer electrolyte.
17. The method for preparing the gel polymer electrolyte according to claim 16, characterized in that, The content of the crosslinking agent initiator is 0.02wt% to 1wt%, based on the mass percentage of the crosslinking agent.
18. The method for preparing the gel polymer electrolyte according to claim 9, characterized in that, The mass ratio of the polymer monomer to the lithium salt is (0.00015~1.6):
1.
19. The method for preparing the gel polymer electrolyte according to claim 9, characterized in that, The polymerization reaction is carried out at a temperature of 50℃ to 100℃ and for a reaction time of 3h to 24h.
20. A secondary battery, comprising a positive electrode, a negative electrode, and a gel electrolyte disposed between the positive electrode and the negative electrode, characterized in that, The gel electrolyte is selected from the gel polymer electrolytes according to any one of claims 1 to 8.