Gel electrolyte precursor and preparation method thereof, gel electrolyte and secondary battery

Abstract

The invention relates to a gel electrolyte precursor and a preparation method thereof, a gel electrolyte and a secondary battery, and belongs to the technical field of methods or devices for directly converting chemical energy into electric energy. The gel electrolyte precursor comprises a polymeric monomer, a catalyst, an initiator and a lithium salt, the polymeric monomers comprise a monomer A and a monomer B; the monomer B comprises at least one of a polyether compound, a polysiloxane compound, boric acid and a derivative thereof. The gel electrolyte formed by polymerizing the gel electrolyte precursor has relatively high oxidation potential, can be matched with a ternary positive electrode or a lithium cobalt oxide positive electrode, and remarkably improves the cycle performance of a battery.

Description

Technical Field

[0001] The present invention relates to the technical field of methods or devices for directly converting chemical energy into electrical energy, and in particular to a gel electrolyte precursor and a preparation method thereof, a gel electrolyte, and a secondary battery. Background Art

[0002] The molecular chain of polyurethane has both rigid hard segments and flexible soft segments, of which the hard segments can provide good mechanical properties, while the soft segments can be used for complexation and transport of lithium ions through structural design. At present, the existing technology for preparing polyurethane electrolytes by in situ polymerization mainly forms a three-dimensional network structure in situ by reacting active hydrogen-containing monomers (such as polyols, polyamines / imines, etc.) with isocyanate groups, thereby obtaining a gel electrolyte or a quasi-solid electrolyte. However, studies have found that active hydrogen-containing monomers are prone to side reactions with the negative electrode material of the battery, thereby increasing the interfacial resistance and deteriorating the battery cycle performance; moreover, especially monomers containing hydroxyl or amino groups, have poor oxidative stability, resulting in poor cycle stability of the gel electrolyte in high-voltage battery systems. In addition, the reaction process between active hydrogen-containing monomers and isocyanate groups is extremely fast, resulting in a sharp increase in the viscosity of the gel electrolyte precursor, making it difficult to effectively infiltrate the electrode, thereby preventing the gel electrolyte precursor from being uniformly polymerized inside the battery, thereby affecting the battery performance. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a gel electrolyte precursor and a preparation method thereof, a gel electrolyte, and a secondary battery.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] In a first aspect, the present invention provides a gel electrolyte precursor, which includes a polymerizable monomer, a catalyst, an initiator, and a lithium salt; the polymerizable monomer includes monomer A and monomer B;

[0006] The chemical structural formula of the monomer A is shown below:

[0007]

[0008] wherein n is an integer between 0 and 10 (for example, n can be any one of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any two of them; the value of n affects the state of the gel electrolyte precursor and thus the performance of the battery);

[0009] R1 is any one of H, -CH3, -CH2CH3;

[0010] R2 is O, any one of , m is an integer between 0 and 10 (for example, m can be any one of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or any two of them, and the value of m will affect the compatibility between the in-situ polymerized polymer and the plasticizer in the gel electrolyte, thereby affecting the performance of the battery);

[0011] R3 is any one of an isocyanate group and an isothiocyanate group;

[0012] The monomer B includes at least one of polyether compounds, polysiloxane compounds, boric acid and derivatives thereof.

[0013] The present invention combines a polymeric monomer A containing both a carbon-carbon double bond and an isocyanate group with a specific polymeric monomer B to form a low-viscosity gel electrolyte precursor, thereby improving the wettability to the battery core and improving the cycle stability and rate performance of the secondary battery. The isocyanate group in the polymeric monomer A reacts with the polymeric monomer B containing active hydrogen to reduce the content of hydroxyl or amino groups in the gel electrolyte precursor, thereby improving the stability of the gel electrolyte precursor to positive and negative electrode materials. At the same time, the boron element, fluorine element or silicon element in the polymeric monomer B is used to increase the electrochemical window of the gel electrolyte and construct a stable positive electrode / electrolyte interface (CEI), thereby improving the flame retardancy of the gel electrolyte and thus improving the safety of the battery.

[0014] The role of the catalyst in the above-mentioned gel electrolyte precursor is to react monomer A with monomer B. The present invention does not particularly limit the type of catalyst, as long as the purpose of the present invention can be achieved. For example, the catalyst can be at least one of stannous octoate, dibutyltin dilaurate, di(dodecylsulfide)dibutyltin, dibutyltin diacetate, tin tert-butoxide, triethylphosphine, tri-n-butylphosphine, triphenylphosphine, dimethylphenylphosphine, pyridine, tris(dimethylaminopropyl)hexahydrotriazine, tetramethylammonium octoate, tributyltin oxide, tetrabutyl titanate, tetrabutyl zirconate, N,N-dimethylcyclohexylamine, triethylenediamine, triethylamine, N-methylmorpholine, N,N-diethylpiperazine, N,N-diethyl-2-methylpiperazine, (dimethylaminoethyl) ether, N-methylethylenediamine, dimethylformamide, triethyleneethylenediamine, methyldiethylene glycolamine and triethylenediamine, and hexamethyldisilazane.

[0015] The function of the initiator in the aforementioned gel electrolyte precursor is to polymerize the double bonds in monomers A and C to ultimately form a gel electrolyte. The present invention does not particularly limit the type of initiator, as long as it can achieve the objectives of the present invention. For example, the initiator can be at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, dibenzoyl peroxide, N,N-dimethylaniline, dicumyl peroxide, di-tert-butyl peroxide, isopropylbenzene hydroperoxide, tert-butyl hydroperoxide, diisopropyl peroxydicarbonate, and potassium persulfate.

[0016] As a preferred embodiment of the gel electrolyte precursor of the present invention, monomer A in the polymerized monomer includes at least one of ethyl isocyanate acrylate (CAS No. 13641-96-8), ethyl methacrylate isocyanate (CAS No. 30674-80-7), 2-[2-(methacryloyloxy)ethoxy]ethyl isocyanate (CAS No. 107023-60-9), and 3-isopropyl-dimethylbenzyl isocyanate (CAS No. 2094-99-7).

[0017] As a preferred embodiment of the gel electrolyte precursor of the present invention, the gel electrolyte precursor satisfies at least one of the following conditions:

[0018] (1) The polyether compound includes at least one of polyethylene glycol, perfluoropolyether alcohol, perfluoropolyether diol, and polyether amine;

[0019] (2) The polysiloxane compound includes at least one of aminopropyl-terminated polydimethylsiloxane, hydroxypropyl-terminated polydimethylsiloxane, and hydrocarbon-terminated polydimethylsiloxane;

[0020] (3) The boric acid and its derivatives include at least one of boric acid, metaboric acid, phenylboric acid, phenylboric acid substituted with an alkyl or halogen group on the benzene ring, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triphenyl borate, triisopropyl borate, tris(hexafluoroisopropyl) borate, tris(2-methylpropyl) borate, tri-tert-butyl borate, tris(2-cyanoethyl)borate, tris(trimethylsilyl)borate, triallyl borate, trimethoxyboroxine, triethoxyboroxine, and tributoxyboroxine.

[0021] In a preferred embodiment of the gel electrolyte precursor of the present invention, monomer B in the polymerizable monomers comprises at least one of triisopropyl borate (CAS No. 5419-55-6), hydroxypropyl-terminated polydimethylsiloxane (CAS No. 104780-66-7), and perfluoropolyether alcohol (CAS No. 90317-77-4). More preferably, the viscosity of the hydroxypropyl-terminated polydimethylsiloxane is 40 to 75 cSt (25°C), preferably 50 to 65 cSt (25°C); and the weight-average molecular weight (Mw) of the perfluoropolyether alcohol is 500 to 1500, preferably 800 to 1200.

[0022] As a preferred embodiment of the gel electrolyte precursor of the present invention, the polymerizable monomer further comprises a monomer C; the monomer C comprises at least one of an acrylic monomer and a vinyl monomer.

[0023] As a preferred embodiment of the gel electrolyte precursor of the present invention, the gel electrolyte precursor satisfies at least one of the following conditions:

[0024] (1) The acrylic monomer includes at least one of methyl acrylate, ethyl acrylate, methyl cyanoacrylate, ethyl cyanoacrylate, methyl methacrylate, ethyl methacrylate, polyethylene glycol methyl ether acrylate, polyethylene glycol diacrylate, trimethylol propane ethoxylate triacrylate, polyethylene glycol methyl ether methacrylate, trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, and hexafluoroisopropyl methacrylate; preferably at least one of methyl methacrylate and trifluoroethyl methacrylate.

[0025] (2) The vinyl monomer includes at least one of acrylonitrile, methacrylamide, styrene, halogen-substituted styrene (the halogen substitution position is on the benzene ring, such as chlorostyrene, bromostyrene, iodostyrene, etc.), methyl vinyl sulfone, vinylene carbonate, and vinyl carbonate; preferably vinyl carbonate.

[0026] As a preferred embodiment of the gel electrolyte precursor of the present invention, the molar ratio of monomer A, monomer B and monomer C is (2-50):(2-50):(0-96). For example, in terms of molar fractions, the molar fraction of monomer A in the polymerized monomers can be any one of 2 parts, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any two of the range values, the molar fraction of monomer B can be any one of 2 parts, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, or any two of the range values, and the molar fraction of monomer C can specifically be any one of 0 parts, 5 parts, 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, or 96 parts, or any two of the range values.

[0027] By regulating the molar ratio of monomer A, monomer B and monomer C in the polymerized monomer within the above range, the comprehensive performance of the gel electrolyte can be significantly optimized. Specifically, the increase of monomer A and monomer B can enhance the electrochemical window, thermal stability and mechanical strength of the electrolyte, while the introduction of monomer C helps to improve the toughness of the electrolyte and the interfacial compatibility between the electrolyte and the electrode. When the molar ratio of the three is within the above range, the gel electrolyte exhibits higher ionic conductivity, better mechanical properties and a wider electrochemical stability window, thereby effectively improving the cycle stability and rate performance of the battery, while significantly reducing the risk of interfacial impedance and lithium dendrite growth; thereby improving the energy density and safety performance of the battery.

[0028] As a preferred embodiment of the gel electrolyte precursor of the present invention, the gel electrolyte precursor further comprises a plasticizer. The main function of the plasticizer is to promote the dissociation of lithium salts, increase ionic conductivity, and improve the mechanical properties and interfacial compatibility of the electrolyte.

[0029] The present invention does not particularly limit the type of plasticizer, as long as the purpose of the present invention can be achieved. For example, the plasticizer can be ethylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, butylene carbonate, methylpropyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, ethyl acetate, ethyl difluoroacetate, ethyl trifluoroacetate, propyl acetate, butyl acetate, methyl propionate, methyl trifluoropropionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, delta-pentyl carbonate, ethyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, ethyl propionate, propyl propionate, ethyl butyrate, propyl propionate, ethyl butyrate, propyl propionate, ethyl butyrate, propyl butyrate, ethyl ... At least one of lactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, sulfolane, dimethyl sulfoxide, hexaphenoxy cyclotriphosphazene, hexafluorotripolyphosphazene, ethoxy pentafluorocyclotriphosphazene, tricresyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, and toluene diphenyl phosphate.

[0030] Among them, fluoroethylene carbonate and the like are mainly used to improve the stability of the electrolyte and the negative electrode, ethylene carbonate and the like are mainly used to improve the ionic conductivity of the electrolyte, methyl formate and the like are mainly used to improve the low-temperature performance of the battery, and hexafluorotripolyphosphazene and the like are mainly used to improve the stability and safety of the electrolyte and the positive electrode.

[0031] As a preferred embodiment of the gel electrolyte precursor of the present invention, the mass percentage of the polymerized monomer is 3% to 80% based on the mass of the gel electrolyte precursor. For example, the mass percentage of the polymerized monomer can be any one of or any two of 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and 80%.

[0032] In a second aspect, the present invention provides a method for preparing the above-mentioned gel electrolyte precursor, which comprises the following steps: uniformly mixing a polymerization monomer, a catalyst, an initiator, a lithium salt and a plasticizer to obtain a gel electrolyte precursor.

[0033] Preferably, the preparation method of the gel electrolyte precursor is: first, monomer A, monomer B and catalyst in the polymerization monomer are dissolved in a plasticizer, and mixed at 0-70°C (for example, it can be any one of 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or any two of the range values) for 1-10h (for example, it can be any one of 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h or any two of the range values); then, monomer C, lithium salt and initiator are added, and mixed evenly to obtain a gel electrolyte precursor.

[0034] In a third aspect, the present invention provides a gel electrolyte obtained by polymerizing the above-mentioned gel electrolyte precursor.

[0035] In a fourth aspect, the present invention provides a secondary battery comprising a positive electrode plate, a negative electrode plate and an electrolyte, wherein the electrolyte is the above-mentioned gel electrolyte.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention combines a polymeric monomer A containing both a carbon-carbon double bond and an isocyanate group with a specific polymeric monomer B to form a low-viscosity gel electrolyte precursor, thereby improving the wettability to the battery core and improving the cycle stability and rate performance of the battery. The isocyanate group in the polymeric monomer A reacts with the polymeric monomer B containing active hydrogen to reduce the content of hydroxyl or amino groups in the gel electrolyte precursor, thereby improving the stability of the gel electrolyte precursor to positive and negative electrode materials. At the same time, the boron element, fluorine element or silicon element in the polymeric monomer B is used to increase the electrochemical window of the gel electrolyte and construct a stable positive electrode / electrolyte interface (CEI), thereby improving the flame retardancy of the gel electrolyte and thus improving the safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 are photos of the gel electrolyte precursor in Example 1 before and after polymerization;

[0039] Figure 2 1 is an electrochemical window diagram of the gel electrolyte corresponding to the gel electrolyte precursor in Example 1 and Comparative Example 1;

[0040] Figure 3 This is a cycle curve diagram of the in-situ polymerized electrolyte lithium battery corresponding to the gel electrolyte precursor in Example 1;

[0041] Figure 4 This is a cycle curve diagram of the in-situ polymerized electrolyte lithium battery corresponding to the gel electrolyte precursor in Comparative Example 1. DETAILED DESCRIPTION

[0042] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0043] Hydroxypropyl-terminated polydimethylsiloxane, manufactured by McLean, with a viscosity of 50-65 cSt (25°C);

[0044] Perfluoropolyether alcohol, manufactured by McLean, Mw=1000.

[0045] Unless otherwise specified, other materials and reagents used in the examples can be obtained from commercial sources.

[0046] Example 1

[0047] This embodiment provides a gel electrolyte precursor, which includes a polymerizable monomer, a catalyst, an initiator, a lithium salt, and a plasticizer, and is prepared by the following preparation method:

[0048] Under the condition that the water and oxygen concentrations are less than 0.1ppm, the polymerization monomers (consisting of monomer A, monomer B and monomer C), 0.01g of catalyst (dibutyltin dilaurate), and 10g of LiTFSI solution (concentration is 1M, the lithium salt is LiTFSI, and the solvent is composed of EC and EMC in a volume ratio of 3:7) are mixed evenly and stirred at room temperature for 4h; then, 0.02g of initiator (azobisisobutyronitrile) is added to obtain a gel electrolyte precursor (in which the mass percentage of the polymerization monomer is 20%).

[0049] Examples 2 to 10

[0050] Examples 2 to 10 provide a gel electrolyte precursor, the preparation method of which is substantially the same as that of Example 1, with the only difference being that the composition and molar ratio of monomer A, monomer B, and monomer C in the polymerizable monomers are different.

[0051] Table 1

[0052]

[0053] Example 11

[0054] This embodiment provides a gel electrolyte precursor, and its preparation method is basically the same as that of Example 1, except that the mass percentage of the polymerized monomer in the gel electrolyte precursor is 10%, and the polymerized monomer is composed of ethyl isocyanate acrylate, trimethoxyboroxine, and methyl methacrylate in a molar ratio of 30:10:60.

[0055] Comparative Example 1

[0056] This comparative example provides a gel electrolyte precursor, comprising a polymerizable monomer, a catalyst, an initiator, a lithium salt, and a plasticizer, and is prepared by the following preparation method:

[0057] Under the condition that the water and oxygen concentrations are less than 0.1ppm, the polymerization monomer (composed of hexamethylene diisocyanate and hydroxypropyl-terminated polydimethylsiloxane in a molar ratio of 50:50), 0.01g of catalyst (dibutyltin dilaurate) and 10g of LiTFSI solution (concentration is 1M, lithium salt is LiTFSI, and the solvent is composed of EC and EMC in a volume ratio of 3:7) are mixed evenly and stirred at room temperature for 4h; then, 0.02g of initiator (azobisisobutyronitrile) is added to obtain a gel electrolyte precursor (in which the mass percentage of the polymerization monomer is 20%).

[0058] Comparative Example 2

[0059] This comparative example provides a gel electrolyte precursor, and its preparation method is basically the same as that of Example 1, except that the polymerization monomer is ethyl isocyanate.

[0060] Comparative Example 3

[0061] This comparative example provides a gel electrolyte precursor, and its preparation method is basically the same as that of Example 1, except that the polymerization monomer is methyl methacrylate.

[0062] Comparative Example 4

[0063] This comparative example provides a gel electrolyte precursor, and its preparation method is basically the same as that of Example 1, except that the polymerization monomer is composed of ethyl isocyanate acrylate and methyl methacrylate in a molar ratio of 50:50.

[0064] Performance Testing

[0065] 1. Polymerization test of gel electrolyte precursor

[0066] The photos of the gel electrolyte precursor before and after polymerization in Example 1 are as follows: Figure 1 As shown, according to Figure 1 It can be seen that the gel electrolyte precursor before polymerization is in a transparent liquid state, while the gel electrolyte precursor after polymerization is in an opaque gel state, indicating that the gel electrolyte precursor of the present invention is successfully polymerized to form a gel electrolyte.

[0067] 2. Electrochemical window test

[0068] The test method is as follows: the gel electrolyte precursors and separators in each embodiment and comparative example are assembled together to form a lithium sheet / separator (PP separator with a thickness of 12 μm) + gel electrolyte precursor / steel sheet battery, which is placed at 60°C for curing for 7 hours, and then heated to 80°C for curing for 2 hours; the LSV curve is tested using an electrochemical workstation with a test voltage range of 3 to 6 V and a scan rate of 1 mV / s.

[0069] according to Figure 2 It can be seen that the oxidation potential of the gel electrolyte formed by the gel electrolyte precursor in Example 1 is 4.53V, which is better than the oxidation potential of the gel electrolyte formed by the gel electrolyte precursor in Comparative Example 1 (4.25V). This may be because the hydroxyl groups in the unreacted hydroxypropyl-terminated polydimethylsiloxane monomer in Comparative Example 1 are easily oxidized and decomposed, which is not conducive to improving its electrochemical window. A wider electrochemical window helps improve the cycling stability of the gel electrolyte when paired with high-voltage positive electrode materials, thereby helping to increase the battery energy density.

[0070] 3. Cycle performance test

[0071] The gel electrolyte precursors in the embodiments and comparative examples were prepared into in-situ polymerized electrolyte lithium batteries, and the preparation method included the following steps:

[0072] A positive electrode sheet, a separator (a PP separator with a thickness of 12 μm), and a negative electrode sheet were laminated to form a dry cell. After the cell was baked, 7.5 g of the gel electrolyte precursor in each embodiment and comparative example was injected into the dry cell (5 Ah cell) under anhydrous and oxygen-isolated conditions, and the cells were allowed to stand for 10 hours. The cells were then placed at 60° C. for curing for 7 hours, and then heated to 80° C. for curing for 2 hours to obtain an in-situ polymerized electrolyte lithium battery.

[0073] The negative electrode sheet in the above preparation method is a lithium-copper composite strip (a lithium metal layer is pressed on the copper surface); the positive electrode sheet is composed of aluminum foil and a positive electrode material coated on the aluminum foil. The positive electrode material is composed of commercial high-nickel ternary (NCM811), polyvinylidene fluoride (PVDF) and single-walled carbon nanotubes in a mass ratio of 9:0.5:0.5.

[0074] The above-mentioned in-situ polymer electrolyte lithium battery was subjected to a cycle performance test, and was charged and discharged for 100 cycles at a current of 0.33C in the range of 2.5 to 4.2V at 25°C.

[0075] First cycle efficiency (%) = discharge capacity of the first cycle / charge capacity of the first cycle × 100%;

[0076] Capacity retention rate (%) = discharge specific capacity at the 100th cycle / discharge specific capacity at the 1st cycle×100%.

[0077] Table 2

[0078]

[0079]

[0080] According to Table 2, Figure 3 and Figure 4It can be seen that the electrochemical window of the gel electrolyte corresponding to the gel electrolyte precursor in Examples 1 to 11 is ≥4.45V, the first cycle efficiency of the in-situ polymerized electrolyte lithium battery is ≥85% and the cycle capacity retention rate of 100 cycles is ≥81%, indicating that the gel electrolyte formed by the polymerization of the gel electrolyte precursor of the present invention has a high oxidation potential, can be adapted to the ternary positive electrode and the lithium cobalt oxide positive electrode, and can effectively improve the cycle performance of the secondary battery. At the same time, according to Comparative Example 1, it can be seen that when hexamethylene diisocyanate and hydroxypropyl-terminated polydimethylsiloxane are used as polymerization monomers, it is not only difficult to improve the electrochemical window of the gel electrolyte, but also due to the poor interface compatibility between the hydroxypropyl-terminated polydimethylsiloxane monomer and the positive / negative electrode, the first cycle efficiency and 100 cycle capacity retention rate of the in-situ polymerized electrolyte lithium battery are greatly reduced. In addition, according to Comparative Examples 2 to 4, it can be found that it is difficult to effectively improve the electrochemical window of the gel electrolyte and the cycle performance of the in-situ polymerized electrolyte lithium battery by using ethyl isocyanate acrylate or methyl methacrylate as the polymerization monomer alone or by combining the two.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A gel electrolyte precursor, characterized in that: It includes polymerization monomers, catalysts, initiators and lithium salts; the polymerization monomers include monomer A and monomer B; The chemical structural formula of the monomer A is shown below: Wherein, n is an integer between 0 and 10; R1 is any one of H, -CH3, -CH2CH3; R2 is O, Any of, m is an integer between 0 and 10; R3 is any one of an isocyanate group and an isothiocyanate group; The monomer B includes at least one of polyether compounds, polysiloxane compounds, boric acid and derivatives thereof.

2. The gel electrolyte precursor according to claim 1, wherein The gel electrolyte precursor satisfies at least one of the following conditions: (1) The polyether compound includes at least one of polyethylene glycol, perfluoropolyether alcohol, perfluoropolyether diol, and polyether amine; (2) The polysiloxane compound includes at least one of aminopropyl-terminated polydimethylsiloxane, hydroxypropyl-terminated polydimethylsiloxane, and hydrocarbon-terminated polydimethylsiloxane; (3) The boric acid and its derivatives include at least one of boric acid, metaboric acid, phenylboric acid, phenylboric acid substituted with an alkyl or halogen group on the benzene ring, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triphenyl borate, triisopropyl borate, tris(hexafluoroisopropyl) borate, tris(2-methylpropyl) borate, tri-tert-butyl borate, tris(2-cyanoethyl)borate, tris(trimethylsilyl)borate, triallyl borate, trimethoxyboroxine, triethoxyboroxine, and tributoxyboroxine.

3. The gel electrolyte precursor according to claim 1, wherein The polymerizable monomer further includes a monomer C; the monomer C includes at least one of an acrylic monomer and a vinyl monomer.

4. The gel electrolyte precursor according to claim 3, wherein The gel electrolyte precursor satisfies at least one of the following conditions: (1) The acrylic monomer includes at least one of methyl acrylate, ethyl acrylate, methyl cyanoacrylate, ethyl cyanoacrylate, methyl methacrylate, ethyl methacrylate, polyethylene glycol methyl ether acrylate, polyethylene glycol diacrylate, trimethylol propane ethoxylate triacrylate, polyethylene glycol methyl ether methacrylate, trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, and hexafluoroisopropyl methacrylate; (2) The vinyl monomer includes at least one of acrylonitrile, methacrylamide, styrene, halogen-substituted styrene, methyl vinyl sulfone, vinylene carbonate, and vinyl ethylene carbonate.

5. The gel electrolyte precursor according to claim 3, wherein The molar ratio of the monomer A, monomer B and monomer C is (2-50):(2-50):(0-96).

6. The gel electrolyte precursor according to claim 1, wherein The gel electrolyte precursor further includes a plasticizer.

7. The gel electrolyte precursor according to claim 1, wherein Based on the mass of the gel electrolyte precursor, the mass percentage of the polymerized monomer is 3% to 80%.

8. The method for preparing the gel electrolyte precursor according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: uniformly mixing polymerization monomers, catalysts, initiators, lithium salts and plasticizers to obtain a gel electrolyte precursor.

9. A gel electrolyte, characterized in that The invention is obtained by polymerizing the gel electrolyte precursor according to any one of claims 1 to 7.

10. A secondary battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, characterized in that: The electrolyte is the gel electrolyte according to claim 9.

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