Composite solid electrolyte membrane and preparation method thereof, secondary battery

Abstract

The application provides a composite solid electrolyte film, a preparation method thereof and a secondary battery. The composite solid electrolyte film comprises a modified pyrochlore-type oxide solid electrolyte, a polymer matrix and a lithium salt. The modified pyrochlore-type oxide solid electrolyte comprises a pyrochlore-type oxide solid electrolyte and a polymer coating layer coated on the surface of the pyrochlore-type oxide solid electrolyte. The polymer coating layer and the pyrochlore-type oxide solid electrolyte are connected by a covalent bond. The polymer coating layer is formed by in-situ polymerization of polymer monomers on the surface of the pyrochlore-type oxide solid electrolyte. The polymer monomers are selected from monomers with trifluoroacetamide functional groups and / or monomers with urethane functional groups. The composite solid electrolyte film has excellent lithium ion conductivity.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a composite solid electrolyte membrane and its preparation method, and a secondary battery. Background Technology

[0002] With the increasing demands for energy density and safety in rechargeable batteries from fields such as new energy vehicles and energy storage systems, traditional liquid electrolytes have become a key bottleneck restricting the industry's development due to their flammability, leakage risks, and short-circuit risks caused by lithium dendrite growth. Solid electrolytes, as the core component of next-generation rechargeable batteries, are widely recognized as the ultimate solution due to their inherent safety. Solid electrolytes are mainly divided into two categories: solid inorganic electrolytes and solid polymer electrolytes.

[0003] While inorganic solid electrolytes possess high lithium-ion conductivity, their high rigidity and brittleness hinder the formation of good interfacial contacts, resulting in poor processability. Furthermore, sulfide solid electrolytes, which offer the highest lithium-ion conductivity, are unstable in the environment, readily decomposing in air to produce toxic hydrogen sulfide gas, and are also costly. Polymer solid electrolytes exhibit good flexibility, achieving good interfacial contact and enabling thin-film processing. However, their lithium-ion transport relies on the movement of polymer chain segments, resulting in weak lithium-ion transport capabilities, and lithium-ion conductivity is often below 10. -4 It has a strength of S / cm and relatively weak mechanical properties.

[0004] Existing composite systems mostly employ a blending strategy of inorganic fillers and polymer matrices, but they still face key technical challenges:

[0005] 1. The inorganic phase is unevenly dispersed and easily forms agglomerates. Furthermore, the interfacial energy between the organic and inorganic phases is high, which easily leads to phase separation and severely hinders the transport of lithium ions.

[0006] 2. Agglomeration of the inorganic phase can easily form stress concentration points, reducing the mechanical properties of the composite solid electrolyte. Summary of the Invention

[0007] The main objective of this invention is to provide a composite solid electrolyte membrane and its preparation method, as well as a secondary battery, to solve the problem of low ionic conductivity of solid electrolyte membranes in the prior art.

[0008] To achieve the above objectives, according to one aspect of the present invention, a composite solid electrolyte membrane is provided, comprising a modified pyrochlore oxide solid electrolyte, a polymer matrix, and a lithium salt. The modified pyrochlore oxide solid electrolyte comprises a pyrochlore oxide solid electrolyte and a polymer coating layer coated on the surface of the pyrochlore oxide solid electrolyte. The polymer coating layer and the pyrochlore oxide solid electrolyte are connected by covalent bonds. The polymer coating layer is formed by in-situ polymerization of polymer monomers on the surface of the pyrochlore oxide solid electrolyte. The polymer monomers are selected from monomers having trifluoroacetamide functional groups and / or monomers having urethane functional groups.

[0009] In modified pyrochlore oxide solid electrolytes, the polymer coating layer exhibits good compatibility with the polymer matrix. Its presence helps improve the dispersion of the inorganic phase within the organic phase, facilitating lithium-ion transport at the organic / inorganic interface. Furthermore, the presence of trifluoroacetamide and urethane functional groups in the polymer coating layer enhances the solubility and stability of the lithium salt, while also enabling the formation of stable complexes with lithium ions, thereby contributing to improved lithium-ion conductivity.

[0010] Furthermore, the mass content of modified pyrochlore oxide solid electrolyte in the composite solid electrolyte membrane is 15-60%.

[0011] Controlling the mass content of modified pyrochlore oxide solid electrolyte in the composite solid electrolyte membrane within the above-mentioned range helps to improve the lithium-ion conductivity of the composite solid electrolyte membrane while controlling its mechanical properties within a suitable range.

[0012] Furthermore, the mass ratio of the pyrochlore oxide solid electrolyte to the polymer coating layer is 1:(0.4~10); and / or, the average particle size of the pyrochlore oxide solid electrolyte is 100~5000 nm; and / or, the weight-average molecular weight of the polymer in the polymer coating layer is 2000~50000 g / mol; and / or, the weight-average molecular weight of the polymer matrix is ​​60000~1200000 g / mol.

[0013] Controlling the thickness of the polymer coating layer within the aforementioned range helps to improve lithium-ion transport efficiency in both the bulk and interfacial regions while reducing the interfacial energy between the pyrochlore oxide solid electrolyte and the polymer matrix. Controlling the average particle size of the pyrochlore oxide solid electrolyte within the aforementioned range facilitates the formation of the polymer coating layer, thereby contributing to further improvement in the lithium-ion conductivity of the composite solid electrolyte membrane. Controlling the weight-average molecular weight of the polymer in the polymer coating layer within the aforementioned range helps to ensure that the modified pyrochlore oxide solid electrolyte provides sufficient lithium-ion transport channels while maintaining good dispersibility and compatibility with other components. Controlling the weight-average molecular weight of the polymer matrix within the aforementioned range helps to improve the mechanical strength, flexibility, and processability of the composite solid electrolyte membrane.

[0014] Furthermore, the polymer monomer is a combination of monomers having trifluoroacetamide functional groups and monomers having urethane functional groups, and the mass ratio of monomers having trifluoroacetamide functional groups to monomers having urethane functional groups is 1:(2~3).

[0015] Controlling the mass ratio of monomers with trifluoroacetamide functional groups to monomers with urethane functional groups within the above range helps to form random copolymers, thereby helping to improve lithium-ion transport capacity.

[0016] Further, the monomer having a trifluoroacetamide functional group is selected from N-allyl-2,2,2-trifluoroacetamide and / or N,N-diallyl-2,2,2-trifluoroacetamide; and / or, the monomer having a carbamate functional group is selected from any one or more of N,N-diallyl tert-butyl carbamate, allyl (2-oxoethyl) carbamate, allyl (2-oxoethyl) carbamate, and tert-butylallyl (pent-4-enyl) carbamate; and / or, the chemical formula of the pyrochlore-type oxide solid electrolyte is (Li a A1 b ) x (La c A2 d ) y (Nb e A3 f)2O6F, where A1 is selected from any one or more of Na, K, Rb, Cs, and Fr; A2 is selected from any one or more of Be, Mg, Ca, Sr, Ba, and Ra; A3 is selected from any one or more of Ta, Zr, W, Hf, Mo, and V; 0 ≤ x ≤ 2, y is used to balance the valence, a + b = 1, 0 < a ≤ 1, 0 ≤ b < 1, c + d = 1, 0 < c ≤ 1, 0 ≤ d < 1, e + f = 1, 0 < e ≤ 1, 0 ≤ f < 1; and / or, the polymer matrix is selected from any one or more of polyvinylidene fluoride, polyvinylidene fluoride-trifluorochloroethylene copolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene copolymer, polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, polyvinylidene fluoride-hexafluoropropylene-trifluoroethylene copolymer, polyvinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer, polyacrylonitrile, polymethyl methacrylate, polyurethane, polyurea, polyvinylpyrrolidone, polypropylene carbonate, polyvinylidene carbonate, polyimide, polyvinyl carbonate, nylon, polyethylene terephthalate, and polyvinyl alcohol; and / or, the lithium salt is selected from any one or more of LiPF6, LiBF4, LiCl, LiI, LiBr, LiClO4, LiAsF6, CH3CO2Li, CF3SO3Li, N(CF3SO2)2Li, N(FSO2)2Li, C(CF2SO2)3Li, C2BF4O4Li, B(C2O4)2Li.

[0017] Controlling the types of monomers with trifluoroacetamide functional groups and monomers with urethane functional groups within the above ranges helps to further improve the ionic conductivity of the composite solid electrolyte membrane. Controlling the types of pyrochlore-type oxide solid electrolytes within the above ranges helps to reduce charge traps and enhance lithium ion mobility. Controlling the types of polymer matrices within the above ranges helps to improve the electrochemical stability and mechanical strength of the composite solid electrolyte membrane. Controlling the types of lithium salts within the above ranges helps to increase the electrochemical window of lithium ions while maintaining good conductivity and electrochemical stability.

[0018] Furthermore, the lithium ion conductivity of the composite solid electrolyte membrane is 1.8~2.7 mS·cm -1 .

[0019] The composite solid electrolyte membrane with the above lithium ion conductivity can shorten the charge-discharge time of the battery, improve the overall energy conversion efficiency of the battery system, reduce the heat generation of the battery, thereby reducing side reactions inside the battery, and further contributing to improving the cycle life of the battery.

[0020] According to another aspect of the present invention, a method for preparing the aforementioned composite solid electrolyte membrane is provided, the method comprising: step S1, mixing raw materials including pyrochlore oxide solid electrolyte, aminosilane coupling agent, and a first organic solvent and performing a hydrolysis-condensation reaction to obtain an aminosilane coupling agent modified pyrochlore oxide solid electrolyte; step S2, mixing raw materials including aminosilane coupling agent modified pyrochlore oxide solid electrolyte, haloacyl halogen initiator, a first catalyst, and a second organic solvent and performing a substitution reaction to obtain an initiator modified pyrochlore oxide solid electrolyte; step S3, mixing raw materials including initiator modified pyrochlore oxide solid electrolyte, polymer monomer, a second catalyst, and a third organic solvent and performing a polymerization reaction to form a polymer coating layer on the surface of the pyrochlore oxide solid electrolyte to obtain a modified pyrochlore oxide solid electrolyte; and step S4, mixing raw materials including modified pyrochlore oxide solid electrolyte, polymer matrix, lithium salt, and a fourth organic solvent and sequentially casting and drying to obtain a composite solid electrolyte membrane.

[0021] In step S1, the siloxy groups in the aminosilane coupling agent are hydrolyzed to generate silanols. The silanols undergo a dehydration condensation reaction with the hydroxyl groups on the surface of the pyrochlore oxide solid electrolyte to form -Si-O- bonds, thus grafting the aminosilane coupling agent onto the surface of the pyrochlore oxide solid electrolyte, forming an aminosilane coupling agent-modified pyrochlore oxide solid electrolyte. In step S2, the amino groups on the surface of the aminosilane coupling agent-modified pyrochlore oxide solid electrolyte undergo a substitution reaction with the halogen atoms in the haloacyl halide initiator to form an initiator-modified pyrochlore oxide solid electrolyte. Introducing haloacyl halide initiators onto the surface of the pyrochlore oxide solid electrolyte helps to grow a polymer coating layer with high uniformity of thickness in situ on the surface of the pyrochlore oxide solid electrolyte, thereby further improving the lithium-ion conductivity of the modified pyrochlore oxide solid electrolyte. In step S3, a polymerization reaction is carried out on the surface of the initiator-modified pyrochlore oxide solid electrolyte to form a polymer coating layer linked by covalent bonds. Finally, the modified pyrochlore oxide solid electrolyte, polymer matrix, lithium salt and fourth organic solvent are thoroughly mixed, and the composite solid electrolyte membrane is prepared by casting and drying.

[0022] Further, the hydrolysis-condensation reaction temperature is 120~140℃; and / or, the hydrolysis-condensation reaction time is 8~12h; and / or, the substitution reaction temperature is -5~0℃; and / or, the substitution reaction time is 8~12h; and / or, the polymerization reaction temperature is 45~55℃; and / or, the polymerization reaction time is 8~12h; and / or, the mass ratio of pyrochlore oxide solid electrolyte to aminosilane coupling agent is 1:(0.5~1.5); and / or, the mass ratio of pyrochlore oxide solid electrolyte, haloacyl halide initiator to first catalyst is 1:(0.2~1.5):(0.1~2); and / or, the mass ratio of pyrochlore oxide solid electrolyte, polymer monomer to second catalyst is 1:(0.4~10):(0.005~0.03).

[0023] Controlling the temperature and time of the hydrolysis-condensation reaction, substitution reaction, and polymerization reaction within the above-mentioned ranges helps to improve the reaction efficiency and the purity of the reaction products. Controlling the mass ratio of pyrochlore oxide solid electrolyte to aminosilane coupling agent within the above-mentioned range provides sufficient active sites to promote subsequent reactions. Controlling the mass ratio of pyrochlore oxide solid electrolyte, haloacyl halide initiator, and first catalyst within the above-mentioned range helps to introduce an appropriate amount of haloacyl halide initiator onto the surface of the pyrochlore oxide solid electrolyte, which is beneficial to improving the uniformity of subsequent polymer coating growth. Controlling the mass ratio of pyrochlore oxide solid electrolyte, polymer monomer, and second catalyst within the above-mentioned range helps to control the weight-average molecular weight of the polymer in the polymer coating layer, thereby contributing to further improvement of the lithium-ion conductivity and mechanical properties of the composite solid electrolyte membrane.

[0024] To further improve the lithium-ion conductivity of the composite solid electrolyte membrane, the aminosilane coupling agent is further selected from γ-3-aminopropyltrimethoxysilane, trimethoxy[3-(methylamino)propyl]silane, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, N-(3-(trimethoxysilyl)propyl)ethylenediamine, N-(3-(trimethoxysilyl)propyl)but-1-amine, 3-(2-aminoethylamino)propyltriethoxysilane, (3-aminopropyl)dimethylmethoxysilane, N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane, and N-methylaminopropyldimethoxysilane. The catalyst is selected from any one or more of alkyl and aminoethylaminoisobutylmethyldimethoxysilane; and / or, the haloacyl halogen initiator is selected from any one or more of 2-bromoisobutyryl bromide, 2-bromobutyryl bromide, 2-bromopropionyl bromide and 3-bromopropionyl chloride; and / or, the first catalyst is selected from any one or more of triethylamine, 2,2'-bipyridine, tris(2-aminoethyl)amine, tetramethylethylenediaminetris(2-pyridinylmethyl)amine, N,N,N',N'',N''-pentamethyldiethylenetriamine, hexamethyltriethylenetetramine, 1,1'-dimethyl-2,2'-biimidazole; and / or, the second catalyst is selected from any one or more of cuprous chloride dihydrate, cuprous chloride tetrahydrate, cuprous bromide, and cuprous bromide.

[0025] According to another aspect of the present invention, a secondary battery is provided, the secondary battery comprising the aforementioned composite solid electrolyte membrane.

[0026] Because the aforementioned secondary battery contains the composite solid electrolyte membrane of this application, the secondary battery has higher energy conversion efficiency and cycle stability.

[0027] By applying the technical solution of this application, a polymer coating layer is covalently bonded to the surface of a pyrochlore oxide solid electrolyte, constructing a stable bulk-interface lithium-conducting network. This reduces the energy barrier at the organic-inorganic interface and promotes rapid lithium-ion transport within the composite solid electrolyte membrane. The pyrochlore oxide solid electrolyte, as the inorganic phase, not only provides high lithium conductivity but is also stable in air, avoiding the safety hazards and cost issues associated with sulfide solid electrolytes. The polymer coating layer in the modified pyrochlore oxide solid electrolyte exhibits good compatibility with the polymer matrix, and its presence helps improve the dispersion of the inorganic phase in the organic phase, facilitating lithium-ion transport at the organic / inorganic phase interface. Furthermore, the presence of trifluoroacetamide and urethane functional groups in the polymer coating layer enhances the solubility and stability of the lithium salt and also allows it to form stable complexes with lithium ions, thereby contributing to improved lithium-ion conductivity. Therefore, the composite solid electrolyte membrane of this application exhibits excellent lithium-ion conductivity. Detailed Implementation

[0028] 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.

[0029] As analyzed in the background section of this application, the existing solid electrolyte membranes have low ionic conductivity. To solve this problem, this application provides a composite solid electrolyte membrane, its preparation method, and a secondary battery.

[0030] In a typical embodiment of this application, a composite solid electrolyte membrane is provided. The composite solid electrolyte membrane includes a modified pyrochlore oxide solid electrolyte, a polymer matrix, and a lithium salt. The modified pyrochlore oxide solid electrolyte includes a pyrochlore oxide solid electrolyte and a polymer coating layer coated on the surface of the pyrochlore oxide solid electrolyte. The polymer coating layer and the pyrochlore oxide solid electrolyte are connected by covalent bonds. The polymer coating layer is formed by in-situ polymerization of polymer monomers on the surface of the pyrochlore oxide solid electrolyte. The polymer monomers are selected from monomers having trifluoroacetamide functional groups and / or monomers having urethane functional groups.

[0031] This application constructs a stable bulk-interface lithium-conducting network by covalently bonding a polymer coating layer to the surface of a pyrochlore oxide solid electrolyte, thereby reducing the energy barrier at the organic-inorganic interface and promoting rapid lithium-ion transport within the composite solid electrolyte membrane. The pyrochlore oxide solid electrolyte, as the inorganic phase, not only provides high lithium conductivity but is also stable in air, avoiding the safety hazards and cost issues associated with sulfide solid electrolytes. The polymer coating layer in the modified pyrochlore oxide solid electrolyte exhibits good compatibility with the polymer matrix, and its presence helps improve the dispersion of the inorganic phase within the organic phase, facilitating lithium-ion transport at the organic / inorganic interface. Furthermore, the presence of trifluoroacetamide and urethane functional groups in the polymer coating layer enhances the solubility and stability of the lithium salt and allows it to form stable complexes with lithium ions, thus contributing to improved lithium-ion conductivity. Therefore, the composite solid electrolyte membrane of this application exhibits excellent lithium-ion conductivity.

[0032] In some embodiments of this application, the mass content of modified pyrochlore oxide solid electrolyte in the composite solid electrolyte membrane is 15-60%.

[0033] Controlling the mass content of modified pyrochlore oxide solid electrolyte in the composite solid electrolyte membrane within the above-mentioned range helps to improve the lithium-ion conductivity of the composite solid electrolyte membrane while controlling its mechanical properties within a suitable range.

[0034] In some embodiments of this application, the mass ratio of the modified pyrochlore oxide solid electrolyte, the polymer matrix, and the lithium salt is (3~7):10:(3~7).

[0035] Modified pyrochlore oxide solid electrolytes have high ionic conductivity, polymer matrix provides flexibility and processability, and lithium salt provides freely moving lithium ions. Controlling the mass ratio of modified pyrochlore oxide solid electrolytes, polymer matrix and lithium salt within the above range helps to further improve the lithium ion conductivity of composite solid electrolyte membranes.

[0036] In some embodiments of this application, the mass ratio of pyrochlore oxide solid electrolyte to polymer coating is 1: (0.4~10); and / or, the average particle size of the pyrochlore oxide solid electrolyte is 100~5000 nm; and / or, the weight-average molecular weight of the polymer in the polymer coating is 2000~50000 g / mol; and / or, the weight-average molecular weight of the polymer matrix is ​​60000~1200000 g / mol.

[0037] Controlling the thickness of the polymer coating layer within the aforementioned range helps to improve lithium-ion transport efficiency in both the bulk and interfacial regions while reducing the interfacial energy between the pyrochlore oxide solid electrolyte and the polymer matrix. Controlling the average particle size of the pyrochlore oxide solid electrolyte within the aforementioned range facilitates the formation of the polymer coating layer, thereby contributing to further improvement in the lithium-ion conductivity of the composite solid electrolyte membrane. Controlling the weight-average molecular weight of the polymer in the polymer coating layer within the aforementioned range helps to ensure that the modified pyrochlore oxide solid electrolyte provides sufficient lithium-ion transport channels while maintaining good dispersibility and compatibility with other components. Controlling the weight-average molecular weight of the polymer matrix within the aforementioned range helps to improve the mechanical strength, flexibility, and processability of the composite solid electrolyte membrane.

[0038] In some embodiments of this application, the polymer monomer is a combination of a monomer having a trifluoroacetamide functional group and a monomer having a urethane functional group, and the mass ratio of the monomer having a trifluoroacetamide functional group to the monomer having a urethane functional group is 1:(2~3).

[0039] Controlling the mass ratio of monomers with trifluoroacetamide functional groups to monomers with urethane functional groups within the above range helps to form random copolymers, thereby helping to improve lithium-ion transport capacity.

[0040] In some embodiments of the present application, the monomer having a trifluoroacetamide functional group is selected from N-allyl-2,2,2-trifluoroacetamide and / or N,N-diallyl-2,2,2-trifluoroacetamide; and / or, the monomer having a carbamate functional group is selected from any one or more of tert-butyl N,N-diallylcarbamate, ethyl allyl(2-oxoethyl)carbamate, tert-butyl allyl(2-oxoethyl)carbamate, and ethyl tert-butyl allyl(pent-4-enyl)carbamate; and / or, the chemical formula of the pyrochlore-type oxide solid electrolyte is (Li a A1 b ) x (La c A2 d ) y (Nb e A3 f )2O6F, where A1 is selected from any one or more of Na, K, Rb, Cs, and Fr, A2 is selected from any one or more of Be, Mg, Ca, Sr, Ba, and Ra, A3 is selected from any one or more of Ta, Zr, W, Hf, Mo, and V, 0 ≤ x ≤ 2, y is used to balance the valence, a + b = 1, 0 < a ≤ 1, 0 ≤ b < 1, c + d = 1, 0 < c ≤ 1, 0 ≤ d < 1, e + f = 1, 0 < e ≤ 1, 0 ≤ f < 1; and / or, the polymer matrix is selected from any one or more of polyvinylidene fluoride, polyvinylidene fluoride-trifluorochloroethylene copolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene copolymer, polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer, polyvinylidene fluoride-hexafluoropropylene-trifluoroethylene copolymer, polyvinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer, polyacrylonitrile, polymethyl methacrylate, polyurethane, polyurea, polyvinylpyrrolidone, polypropylene carbonate, polyvinylidene carbonate, polyimide, polyvinyl carbonate, nylon, polyethylene terephthalate, and polyvinyl alcohol; and / or, the lithium salt is selected from any one or more of LiPF6, LiBF4, LiCl, LiI, LiBr, LiClO4, LiAsF6, CH3CO2Li, CF3SO3Li, N(CF3SO2)2Li, N(FSO2)2Li, C(CF2SO2)3Li, C2BF4O4Li, B(C2O4)2Li.

[0041] Controlling the types of monomers with trifluoroacetamide and urethane functional groups within the aforementioned range helps to further improve the ionic conductivity of the composite solid electrolyte membrane. Controlling the types of pyrochlore-type oxide solid electrolytes within the aforementioned range helps to reduce charge trapping and improve lithium-ion mobility. Controlling the types of polymer matrices within the aforementioned range helps to improve the electrochemical stability and mechanical strength of the composite solid electrolyte membrane. Controlling the types of lithium salts within the aforementioned range helps to increase the electrochemical window for lithium ions while maintaining good conductivity and electrochemical stability.

[0042] In some embodiments of this application, the lithium-ion conductivity of the composite solid electrolyte membrane is 1.8~2.7 mS·cm. -1 .

[0043] Composite solid electrolyte membranes with the aforementioned lithium-ion conductivity can shorten battery charge and discharge time, improve the overall energy conversion efficiency of the battery system, reduce battery heat generation, thereby reducing internal side reactions and thus helping to improve battery cycle life.

[0044] In another typical embodiment of this application, a method for preparing the aforementioned composite solid electrolyte membrane is provided. The method includes: step S1, mixing raw materials including pyrochlore oxide solid electrolyte, aminosilane coupling agent, and a first organic solvent, and then performing a hydrolysis-condensation reaction to obtain an aminosilane coupling agent modified pyrochlore oxide solid electrolyte; step S2, mixing raw materials including aminosilane coupling agent modified pyrochlore oxide solid electrolyte, haloacyl halogen initiator, a first catalyst, and a second organic solvent, and then performing a substitution reaction to obtain an initiator modified pyrochlore oxide solid electrolyte; step S3, mixing raw materials including initiator modified pyrochlore oxide solid electrolyte, polymer monomer, a second catalyst, and a third organic solvent, and then performing a polymerization reaction to form a polymer coating layer on the surface of the pyrochlore oxide solid electrolyte to obtain a modified pyrochlore oxide solid electrolyte; and step S4, mixing raw materials including modified pyrochlore oxide solid electrolyte, polymer matrix, lithium salt, and a fourth organic solvent, and then sequentially casting and drying the mixture to obtain a composite solid electrolyte membrane.

[0045] In step S1, the siloxy groups in the aminosilane coupling agent are hydrolyzed to generate silanols. The silanols undergo a dehydration condensation reaction with the hydroxyl groups on the surface of the pyrochlore oxide solid electrolyte to form -Si-O- bonds, thus grafting the aminosilane coupling agent onto the surface of the pyrochlore oxide solid electrolyte, forming an aminosilane coupling agent-modified pyrochlore oxide solid electrolyte. In step S2, the amino groups on the surface of the aminosilane coupling agent-modified pyrochlore oxide solid electrolyte undergo a substitution reaction with the halogen atoms in the haloacyl halide initiator to form an initiator-modified pyrochlore oxide solid electrolyte. Introducing haloacyl halide initiators onto the surface of the pyrochlore oxide solid electrolyte helps to grow a polymer coating layer with high uniformity of thickness in situ on the surface of the pyrochlore oxide solid electrolyte, thereby further improving the lithium-ion conductivity of the modified pyrochlore oxide solid electrolyte. In step S3, a polymerization reaction is carried out on the surface of the initiator-modified pyrochlore oxide solid electrolyte to form a polymer coating layer linked by covalent bonds. Finally, the modified pyrochlore oxide solid electrolyte, polymer matrix, lithium salt and fourth organic solvent are thoroughly mixed, and the composite solid electrolyte membrane is prepared by casting and drying.

[0046] Including but not limited to, the first organic solvent is selected from any one or more of toluene, tetrahydrofuran, dichloromethane, acetone, chloroform, ethyl acetate, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, diethylene glycol dimethyl ether, ethanol, propanol, isopropanol, n-butanol, isobutanol, and isoamyl alcohol; the second organic solvent is selected from any one of toluene, tetrahydrofuran, dichloromethane, acetone, chloroform, ethyl acetate, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, and diethylene glycol dimethyl ether. One or more of the following: the third organic solvent is selected from toluene, tetrahydrofuran, dichloromethane, acetone, chloroform, ethyl acetate, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, diethylene glycol dimethyl ether, ethanol, propanol, isopropanol, n-butanol, isobutanol, and isoamyl alcohol; the fourth organic solvent is selected from diethyl ether, ethanol, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran, malononitrile, toluene, and dichloromethane.

[0047] In some embodiments of this application, the hydrolysis-condensation reaction temperature is 120~140℃; and / or, the hydrolysis-condensation reaction time is 8~12h; and / or, the substitution reaction temperature is -5~0℃; and / or, the substitution reaction time is 8~12h; and / or, the polymerization reaction temperature is 45~55℃; and / or, the polymerization reaction time is 8~12h; and / or, the mass ratio of pyrochlore oxide solid electrolyte to aminosilane coupling agent is 1:(0.5~1.5); and / or, the mass ratio of pyrochlore oxide solid electrolyte, haloacyl halide initiator to first catalyst is 1:(0.2~1.5):(0.1~2); and / or, the mass ratio of pyrochlore oxide solid electrolyte, polymer monomer to second catalyst is 1:(0.4~10):(0.005~0.03).

[0048] Controlling the temperature and time of the hydrolysis-condensation reaction, substitution reaction, and polymerization reaction within the above-mentioned ranges helps to improve the reaction efficiency and the purity of the reaction products. Controlling the mass ratio of pyrochlore oxide solid electrolyte to aminosilane coupling agent within the above-mentioned range provides sufficient active sites to promote subsequent reactions. Controlling the mass ratio of pyrochlore oxide solid electrolyte, haloacyl halide initiator, and first catalyst within the above-mentioned range helps to introduce an appropriate amount of haloacyl halide initiator onto the surface of the pyrochlore oxide solid electrolyte, which is beneficial to improving the uniformity of subsequent polymer coating growth. Controlling the mass ratio of pyrochlore oxide solid electrolyte, polymer monomer, and second catalyst within the above-mentioned range helps to control the weight-average molecular weight of the polymer in the polymer coating layer, thereby contributing to further improvement of the lithium-ion conductivity and mechanical properties of the composite solid electrolyte membrane.

[0049] To further improve the lithium-ion conductivity of the composite solid electrolyte membrane, in some embodiments of this application, the aminosilane coupling agent is selected from γ3-aminopropyltrimethoxysilane, trimethoxy[3-(methylamino)propyl]silane, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, N-(3-(trimethoxysilyl)propyl)ethylenediamine, N-(3-(trimethoxysilyl)propyl)but-1-amine, 3-(2-aminoethylamino)propyltriethoxysilane, (3-aminopropyl)dimethylmethoxysilane, N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane, N-methylaminopropyldimethoxysilane, etc. The catalyst is selected from one or more of oxysilanes and aminoethylaminoisobutylmethyldimethoxysilanes; and / or, the halogenated acyl halide initiator is selected from one or more of 2-bromoisobutyryl bromide, 2-bromobutyryl bromide, 2-bromopropionyl bromide and 3-bromopropionyl chloride; and / or, the first catalyst is selected from one or more of triethylamine, 2,2'-bipyridine, tris(2-aminoethyl)amine, tetramethylethylenediaminetris(2-pyridinylmethyl)amine, N,N,N',N'',N''-pentamethyldiethylenetriamine, hexamethyltriethylenetetramine, 1,1'-dimethyl-2,2'-biimidazole; and / or, the second catalyst is selected from one or more of cuprous chloride dihydrate, cuprous chloride tetrahydrate, cuprous bromide, and cuprous bromide.

[0050] In another typical embodiment of this application, a secondary battery is provided, which contains the aforementioned composite solid electrolyte membrane.

[0051] Because the aforementioned secondary battery contains the composite solid electrolyte membrane of this application, the secondary battery has higher energy conversion efficiency and cycle stability.

[0052] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0053] Example 1

[0054] pyrochlore-type oxide solid electrolyte Li 1.25 La 0.58 The preparation method of Nb2O6F is as follows: 1.847g of Li2CO3, 8.146g of La2O3, 26.581g of Nb2O, and ethanol are placed together in a ball mill jar, and milling beads are added. The material ratio of milling beads to material is 6:1. The mixture is ball-milled at 400 rpm for 12 hours. After milling, the mixture is removed, dried, ground, and placed in an alumina ceramic boat. The mixture is heated to 1200℃ in a muffle furnace under air atmosphere at a heating rate of 5℃ / min and held at that temperature for 12 hours. After natural cooling to room temperature, the precursor Li is obtained. 0.5 La 0.5 Nb₂O₆, 3.5472g of Li0.5 La 0.5 Nb₂O₆, 1.5672 g of LaF₃, 3.709 g of LiF, and anhydrous ethanol were added to a ball mill jar, along with milling beads, at a ball-to-material ratio of 6:1. The mixture was ball-milled at 400 rpm for 12 hours. After drying, the product was placed in a tube furnace and held at 1000 °C for 12 hours under an argon atmosphere. The product was then removed and ball-milled again to control the average particle size to 600 nm, yielding the pyrochlore-type oxide solid electrolyte LiF. 1.25 La 0.58 Nb2O6F.

[0055] (1) Preparation of pyrochlore-type oxide solid electrolyte modified with aminosilane coupling agent: Take 10g of pyrochlore-type oxide solid electrolyte Li 1.25 La 0.58 Nb₂O₆F was placed in a 250 mL Erlenmeyer flask, and 25 mL of toluene was added as solvent. The mixture was ultrasonically dispersed for 10 min, and 10 g of γ-3-aminopropyltrimethoxysilane was added dropwise. The mixture was subjected to a hydrolysis-condensation reaction at 130 °C for 12 h. After cooling, the solid sample was separated by centrifugation and washed at least three times each with toluene and ethanol. The sample was then dried in a vacuum oven at 80 °C for 24 h to obtain an aminosilane coupling agent-modified pyrochlore oxide solid electrolyte.

[0056] (2) Preparation of initiator-modified pyrochlore oxide solid electrolyte: 100 mL of toluene was placed in a 2500 mL Erlenmeyer flask, and the above-mentioned aminosilane coupling agent-modified pyrochlore oxide solid electrolyte was added. The mixture was ultrasonically dispersed for 10 min, placed in ice water at 0 °C, and triethylamine was added as the first catalyst. The mixture was stirred for 30 min. 2-bromoisobutyryl bromide was dissolved in 30 mL of toluene and added dropwise to an Erlenmeyer flask placed in an ice water bath. The mixture was stirred for 12 h. The mass ratio of pyrochlore oxide solid electrolyte, 2-bromoisobutyryl bromide and triethylamine was 1:0.75:0.36. The solid sample was then separated by centrifugation, washed with ethanol more than six times, and dried in a vacuum oven at 80 °C for 24 h to obtain the initiator-modified pyrochlore oxide solid electrolyte.

[0057] (3) Preparation of modified pyrochlore oxide solid electrolyte: Take the above-mentioned initiator-modified pyrochlore oxide solid electrolyte and the second catalyst, place them in a 500 mL three-necked flask, the second catalyst is a mixture of cuprous chloride dihydrate and cupric chloride tetrahydrate in a mass ratio of 5:1, add 250 mL of isopropanol, ultrasonically disperse for 5 min, add polymer monomer (N-allyl-2,2,2-trifluoroacetamide), the mass ratio of pyrochlore oxide solid electrolyte, polymer monomer and second catalyst is 1:1:0.006, place in ice water and stir, purge with argon gas for 30 min to remove oxygen in the system, seal the flask, polymerize at 50 °C for 8 h, cool to room temperature, wash several times with isopropanol and methanol respectively, dry in a vacuum drying oven at 50 °C for 24 h to obtain modified pyrochlore oxide solid electrolyte, the mass ratio of pyrochlore oxide solid electrolyte to polymer coating layer is 1:1, the weight average molecular weight of polymer is 5000 g / mol.

[0058] (4) Preparation of composite solid electrolyte membrane: Take 5g of the above modified pyrochlore oxide solid electrolyte, 10g of polyvinylidene fluoride-hexafluoropropylene copolymer (weight average molecular weight of 600000g / mol), and 5g of N(CF3SO2)2Li and dissolve them in 60mL of N,N-dimethylformamide. Place them in a 250mL Erlenmeyer flask, stir for 12h, ultrasonically disperse for 1h, let stand for 12h, and then cast and dry to obtain a composite solid electrolyte membrane with a thickness of 100μm.

[0059] Example 2

[0060] The difference from Example 1 is that trimethoxy[3-(methylamino)propyl]silane was used instead of γ3-aminopropyltrimethoxysilane, and a composite solid electrolyte membrane was finally obtained.

[0061] Example 3

[0062] The difference from Example 1 is that 2-bromopropionyl bromide is used instead of 2-bromoisobutyryl bromide, and a composite solid electrolyte membrane is finally obtained.

[0063] Example 4

[0064] The difference from Example 1 is that N,N-diallylcarbamate tert-butyl ester was used instead of N-allyl-2,2,2-trifluoroacetamide, and a composite solid electrolyte membrane was finally obtained.

[0065] Example 5

[0066] The difference from Example 1 is that polyvinylidene fluoride-trifluorochloroethylene copolymer is used instead of polyvinylidene fluoride-hexafluoropropylene copolymer, and finally a composite solid electrolyte membrane is obtained.

[0067] Example 6

[0068] The difference from Example 1 is that the amount of γ3-aminopropyltrimethoxysilane added is 5g, and a composite solid electrolyte membrane is finally obtained.

[0069] Example 7

[0070] The difference from Example 1 is that the amount of γ3-aminopropyltrimethoxysilane added is 15g, and a composite solid electrolyte membrane is finally obtained.

[0071] Example 8

[0072] The difference from Example 1 is that the amount of 2-bromoisobutyryl bromide added is 4g, and a composite solid electrolyte membrane is finally obtained.

[0073] Example 9

[0074] The difference from Example 1 is that the amount of 2-bromoisobutyryl bromide added is 11g, and a composite solid electrolyte membrane is finally obtained.

[0075] Example 10

[0076] The difference from Example 1 is that the amount of polyvinylidene fluoride-hexafluoropropylene copolymer added is 15g, and a composite solid electrolyte membrane is finally obtained.

[0077] Example 11

[0078] The difference from Example 1 is that the amount of polyvinylidene fluoride-hexafluoropropylene copolymer added is 5g, and a composite solid electrolyte membrane is finally obtained.

[0079] Example 12

[0080] The difference from Example 1 is that the mass of the modified pyrochlore oxide solid electrolyte is 3g, the mass of the polyvinylidene fluoride-hexafluoropropylene copolymer is 10g, the mass of N(CF3SO2)2Li is 7g, and finally a composite solid electrolyte membrane is obtained, with the mass content of the modified pyrochlore oxide solid electrolyte being 15%.

[0081] Example 13

[0082] The difference from Example 1 is that the mass of the modified pyrochlore oxide solid electrolyte is 12g, the mass of the polyvinylidene fluoride-hexafluoropropylene copolymer is 6g, the mass of N(CF3SO2)2Li is 2g, and finally a composite solid electrolyte membrane is obtained, with the mass content of the modified pyrochlore oxide solid electrolyte being 60%.

[0083] Example 14

[0084] The difference from Example 1 is that the mass of N-allyl-2,2,2-trifluoroacetamide is 4g, the mass ratio of pyrochlore oxide solid electrolyte to polymer coating layer in the obtained modified pyrochlore oxide solid electrolyte is 1:0.4, the weight average molecular weight of polymer is 2000g / mol, and finally a composite solid electrolyte membrane is obtained.

[0085] Example 15

[0086] The difference from Example 1 is that the mass of N-allyl-2,2,2-trifluoroacetamide is 100g, the mass ratio of pyrochlore oxide solid electrolyte to polymer coating layer in the obtained modified pyrochlore oxide solid electrolyte is 1:10, the weight average molecular weight of polymer is 50000g / mol, and finally a composite solid electrolyte membrane is obtained.

[0087] Example 16

[0088] The difference from Example 1 is that the mass of N-allyl-2,2,2-trifluoroacetamide is 2g, the mass ratio of pyrochlore oxide solid electrolyte to polymer coating layer in the obtained modified pyrochlore oxide solid electrolyte is 1:0.2, the weight average molecular weight of polymer is 1000g / mol, and finally a composite solid electrolyte membrane is obtained.

[0089] Example 17

[0090] The difference from Example 1 is that N-allyl-2,2,2-trifluoroacetamide is replaced by a combination of N-allyl-2,2,2-trifluoroacetamide and allyl (2-oxoethyl)carbamate, and the mass ratio of N-allyl-2,2,2-trifluoroacetamide to allyl (2-oxoethyl)carbamate in the combination is 1:2, finally obtaining a composite solid electrolyte membrane.

[0091] Example 18

[0092] The difference from Example 1 is that N-allyl-2,2,2-trifluoroacetamide is replaced by a combination of N-allyl-2,2,2-trifluoroacetamide and allyl (2-oxoethyl)carbamate, and the mass ratio of N-allyl-2,2,2-trifluoroacetamide to allyl (2-oxoethyl)carbamate in the combination is 1:3, finally obtaining a composite solid electrolyte membrane.

[0093] Comparative Example 1

[0094] The difference from Example 1 is that 5g of pyrochlore-type oxide solid electrolyte Li was used.1.25 La 0.58 Nb2O6F, 10g of polyvinylidene fluoride-hexafluoropropylene copolymer, and 5g of N(CF3SO2)2Li were dissolved in 60mL of N,N-dimethylformamide, placed in a 250mL Erlenmeyer flask, stirred for 12h, ultrasonically dispersed for 1h, and then allowed to stand for 12h. After that, the mixture was cast into a film and dried to obtain a composite solid electrolyte membrane.

[0095] Comparative Example 2

[0096] The difference from Example 1 is that the addition of γ3-aminopropyltrimethoxysilane was omitted, and a composite solid electrolyte membrane was finally obtained.

[0097] Comparative Example 3

[0098] The difference from Example 1 is that ammonium persulfate was used instead of 2-bromoisobutyryl bromide, and a composite solid electrolyte membrane was finally obtained.

[0099] Comparative Example 4

[0100] The difference from Example 1 is that ethyl acrylate was used instead of N-allyl-2,2,2-trifluoroacetamide, and a composite solid electrolyte membrane was finally obtained.

[0101] Comparative Example 5

[0102] The difference from Example 1 is that a garnet-type oxide solid electrolyte, Li7La3Zr2O, is used. 12 Replacement of pyrochlore-type oxide solid electrolyte Li 1.25 La 0.58 Nb2O6F was used to obtain a composite solid electrolyte membrane.

[0103] Lithium-ion conductivity test: The solid electrolyte membranes prepared in the examples and comparative examples were placed between two steel sheets with a diameter of 15.5 mm, and encapsulated with a CR2025 button cell battery case to assemble a battery. The lithium-ion conductivity at 25 °C was tested using the AC impedance method. The test results are shown in Table 1. Lithium-ion conductivity of solid electrolyte membrane and battery performance test results.

[0104] Battery performance testing: Lithium iron phosphate positive electrode, solid electrolyte membrane prepared in the examples and comparative examples, and lithium metal negative electrode were stacked and hot-pressed to obtain bare cells. The bare cells were placed in battery cases for encapsulation to obtain coin cells. The coin cells were tested at room temperature, with a voltage range of 2.5~4.0V and a rate of 0.1C for the first discharge specific capacity and capacity retention after 50 cycles. The test results are shown in Table 1 for the lithium-ion conductivity of the solid electrolyte membrane and the battery performance test results.

[0105] Table 1. Test results of lithium-ion conductivity and battery performance of solid electrolyte membranes.

[0106]

[0107] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0108] This application constructs a stable bulk-interface lithium-conducting network by covalently bonding a polymer coating layer to the surface of a pyrochlore oxide solid electrolyte, thereby reducing the energy barrier at the organic-inorganic interface and promoting rapid lithium-ion transport within the composite solid electrolyte membrane. The pyrochlore oxide solid electrolyte, as the inorganic phase, not only provides high lithium conductivity but is also stable in air, avoiding the safety hazards and cost issues associated with sulfide solid electrolytes. The polymer coating layer in the modified pyrochlore oxide solid electrolyte exhibits good compatibility with the polymer matrix, and its presence helps improve the dispersion of the inorganic phase within the organic phase, facilitating lithium-ion transport at the organic / inorganic interface. Furthermore, the presence of trifluoroacetamide and urethane functional groups in the polymer coating layer enhances the solubility and stability of the lithium salt and allows it to form stable complexes with lithium ions, thus contributing to improved lithium-ion conductivity. Therefore, the composite solid electrolyte membrane of this application exhibits excellent lithium-ion conductivity.

[0109] 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 composite solid electrolyte membrane, characterized in that, The composite solid electrolyte membrane comprises a modified pyrochlore oxide solid electrolyte, a polymer matrix, and a lithium salt. The modified pyrochlore oxide solid electrolyte includes a pyrochlore oxide solid electrolyte and a polymer coating layer covering the surface of the pyrochlore oxide solid electrolyte. The polymer coating layer and the pyrochlore oxide solid electrolyte are connected by covalent bonds. The polymer coating layer is formed by in-situ polymerization of polymer monomers on the surface of the pyrochlore oxide solid electrolyte. The polymer monomers are selected from monomers having trifluoroacetamide functional groups and / or monomers having urethane functional groups.

2. The composite solid electrolyte membrane according to claim 1, characterized in that, The mass content of the modified pyrochlore oxide solid electrolyte in the composite solid electrolyte membrane is 15-60%.

3. The composite solid electrolyte membrane according to claim 1, characterized in that, The mass ratio of the pyrochlore oxide solid electrolyte to the polymer coating layer is 1:(0.4~10); and / or, the average particle size of the pyrochlore oxide solid electrolyte is 100~5000 nm; and / or, the weight-average molecular weight of the polymer in the polymer coating layer is 2000~50000 g / mol; and / or, the weight-average molecular weight of the polymer matrix is ​​60000~1200000 g / mol.

4. The composite solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The polymer monomer is a combination of the monomer having a trifluoroacetamide functional group and the monomer having a carbamate functional group, and the mass ratio of the monomer having a trifluoroacetamide functional group to the monomer having a carbamate functional group is 1:(2~3).

5. The composite solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The monomer having the trifluoroacetamide functional group is selected from N-allyl-2,2,2-trifluoroacetamide and / or N,N-diallyl-2,2,2-trifluoroacetamide; And / or, the monomer having a carbamate functional group is selected from any one or more of N,N-diallyl tert-butyl carbamate, allyl (2-oxoethyl) ethyl carbamate, allyl (2-oxoethyl) tert-butyl carbamate and tert-butylallyl (pent-4-enyl) ethyl carbamate. And / or, the chemical formula of the pyrochlore-type oxide solid electrolyte is (Li a A1 b ) x (La c A2 d ) y (Nb e A3 f )2O6F, where A1 is selected from any one or more of Na, K, Rb, Cs, and Fr; A2 is selected from any one or more of Be, Mg, Ca, Sr, Ba, and Ra; A3 is selected from any one or more of Ta, Zr, W, Hf, Mo, and V; 0≤x≤2; y is used to balance valence; a+b=1; 0 <a≤1,0≤b<1,c+d=1,0<c≤1,0≤d<1,e+f=1,0<e≤1,0≤f<1; And / or, the polymer matrix is ​​selected from any one or more of polyvinylidene fluoride, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride-hexafluoropropylene-trifluoroethylene copolymer, polyvinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer, polyacrylonitrile, polymethyl methacrylate, polyurethane, polyurea, polyvinylpyrrolidone, polypropylene carbonate, polyvinyl carbonate, polyimide, polyvinyl carbonate, nylon, polyethylene terephthalate, and polyvinyl alcohol; And / or, the lithium salt is selected from any one or more of LiPF6, LiBF4, LiCl, LiI, LiBr, LiClO4, LiAsF6, CH3CO2Li, CF3SO3Li, N(CF3SO2)2Li, N(FSO2)2Li, C(CF2SO2)3Li, C2BF4O4Li, and B(C2O4)2Li.

6. The composite solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The lithium-ion conductivity of the composite solid electrolyte membrane is 1.8~2.7 mS·cm. -1 .

7. A method for preparing a composite solid electrolyte membrane according to any one of claims 1 to 6, characterized in that, The preparation method includes: Step S1: The raw materials including pyrochlore oxide solid electrolyte, aminosilane coupling agent and first organic solvent are mixed and subjected to hydrolysis-condensation reaction to obtain aminosilane coupling agent modified pyrochlore oxide solid electrolyte. Step S2: The raw materials including the aminosilane coupling agent-modified pyrochlore oxide solid electrolyte, haloacyl halogen initiator, first catalyst and second organic solvent are mixed and subjected to a substitution reaction to obtain the initiator-modified pyrochlore oxide solid electrolyte. Step S3: The raw materials including the initiator-modified pyrochlore oxide solid electrolyte, polymer monomer, second catalyst and third organic solvent are mixed and subjected to polymerization reaction to form a polymer coating layer on the surface of the pyrochlore oxide solid electrolyte, thereby obtaining the modified pyrochlore oxide solid electrolyte. Step S4 involves mixing the modified pyrochlore oxide solid electrolyte, polymer matrix, lithium salt, and fourth organic solvent, then sequentially casting and drying the mixture to obtain the composite solid electrolyte membrane.

8. The preparation method according to claim 7, characterized in that, The hydrolysis-condensation reaction is carried out at a temperature of 120~140℃; and / or the hydrolysis-condensation reaction is carried out for a time of 8~12h. And / or, the temperature of the substitution reaction is -5 to 0°C; and / or, the time of the substitution reaction is 8 to 12 hours; And / or, the polymerization reaction temperature is 45~55℃; and / or, the polymerization reaction time is 8~12h; And / or, the mass ratio of the pyrochlore-type oxide solid electrolyte to the aminosilane coupling agent is 1:(0.5~1.5). And / or, the mass ratio of the pyrochlore-type oxide solid electrolyte, the haloacyl halide initiator, and the first catalyst is 1:(0.2~1.5):(0.1~2). And / or, the mass ratio of the pyrochlore oxide solid electrolyte, the polymer monomer, and the second catalyst is 1:(0.4~10):(0.005~0.03).

9. The preparation method according to claim 7 or 8, characterized in that, The aminosilane coupling agent is selected from any one or more of γ3-aminopropyltrimethoxysilane, trimethoxy[3-(methylamino)propyl]silane, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, N-(3-(trimethoxysilyl)propyl)ethylenediamine, N-(3-(trimethoxysilyl)propyl)but-1-amine, 3-(2-aminoethylamino)propyltriethoxysilane, (3-aminopropyl)dimethylmethoxysilane, N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane, N-methylaminopropyldimethoxysilane, and aminoethylaminoisobutylmethyldimethoxysilane. And / or, the haloacyl halogen initiator is selected from any one or more of 2-bromoisobutyryl bromide, 2-bromobutyryl bromide, 2-bromopropionyl bromide, and 3-bromopropionyl chloride; And / or, the first catalyst is selected from any one or more of triethylamine, 2,2'-bipyridine, tris(2-aminoethyl)amine, tetramethylethylenediaminetris(2-pyridinemethyl)amine, N,N,N',N'',N''-pentamethyldiethylenetriamine, hexamethyltriethylenetetramine, and 1,1'-dimethyl-2,2'-biimidazole; And / or, the second catalyst is selected from any one or more of cuprous chloride dihydrate, cuprous chloride tetrahydrate, cuprous bromide, and cuprous bromide.

10. A secondary battery, characterized in that, The secondary battery contains a composite solid electrolyte membrane as described in any one of claims 1 to 6.

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