A composite solid electrolyte membrane with high ceramic content, its preparation method and application

Abstract

This invention relates to a composite solid electrolyte membrane with high ceramic content, its preparation method, and its application. The preparation method includes: mixing ceramic solid electrolyte particles activated by a silane coupling agent with an in-situ polymerization solution containing a crosslinking agent, organic monomers, a plasticizer, a lithium salt, an ultraviolet photoinitiator, and a thermal initiator to form a solid electrolyte slurry, wherein the ceramic solid electrolyte particles account for 60% to 90% of the total mass of the composite solid electrolyte membrane; coating the solid electrolyte slurry onto a positive electrode sheet; firstly, in-situ polymerization of the shallow organic monomers and crosslinking agent is initiated by an ultraviolet photoinitiator; then, a negative electrode sheet is covered and hot-pressed; the remaining organic monomers and crosslinking agent are in-situ polymerized by a thermal initiator to form a composite electrolyte membrane with high ceramic content, and an all-solid-state battery containing this composite solid electrolyte membrane; the solid-state battery containing the in-situ formed composite solid electrolyte membrane has high cycle stability.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery materials technology, and in particular to a composite solid-state electrolyte membrane with high ceramic content, its preparation method, and its application. Background Technology

[0002] With the surge in demand for high-energy-density and high-safety batteries from the new energy vehicle and energy storage industries, all-solid-state batteries (ASSBs) are considered the core direction of next-generation lithium battery technology. Among them, ceramic solid electrolytes (such as LLZO, LATP, etc.) have become a research hotspot due to their non-flammability, high ionic conductivity, and excellent dendrite suppression capabilities. The current mainstream method is to directly use ceramic electrolyte particles (such as LLZO, LLTO, etc.) as passive fillers, simply physically mixing them into a pre-polymerized polymer solution, then casting and coating them, and finally drying them to form a film. However, its industrialization still faces the following three major technical bottlenecks.

[0003] (1) Uneven dispersion: Nanoscale ceramic particles have extremely high surface energy and are prone to agglomeration in polymer solutions, forming micron-sized aggregates. Agglomerates become local "dead zones," which not only fail to contribute to ionic conductivity but also become obstacles to ion migration, leading to a decrease in overall ionic conductivity. At the same time, agglomeration can cause uneven film thickness and deterioration of mechanical properties.

[0004] (2) Poor interfacial compatibility: The inorganic ceramic particles and the organic polymer matrix are chemically incompatible, which leads to high interfacial impedance.

[0005] (3) The ceramic content is limited. When the amount added is higher than 50%, the above-mentioned agglomeration and compatibility problems will be amplified indefinitely, and the rheological properties of the slurry will become extremely poor (too viscous or shear thinning will occur), making it impossible to carry out high-quality coating and severely reducing film formation.

[0006] Therefore, it is necessary to develop a novel solid electrolyte membrane that is formed in situ during the preparation of solid-state batteries and has a high ceramic solid electrolyte content. While overcoming the above problems, it can improve the ionic conductivity, mechanical strength and stability of the composite solid electrolyte membrane and reduce the interfacial impedance. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a composite solid electrolyte membrane with high ceramic content, its preparation method, and its applications.

[0008] This invention involves mixing ceramic solid electrolyte particles activated by a silane coupling agent with an in-situ polymerization liquid to form a solid electrolyte slurry, wherein the content of ceramic solid electrolyte particles is much greater than that of the in-situ polymerization liquid. The solid electrolyte slurry is coated on a positive electrode and pre-cured by ultraviolet irradiation. Then, it is hot-pressed together with a negative electrode to perform in-situ polymerization, forming a composite electrolyte membrane with high ceramic content, and an all-solid-state battery containing the composite solid electrolyte membrane.

[0009] This invention activates ceramic solid electrolyte particles using a silane coupling agent, enabling covalent bonding between the ceramic solid electrolyte particles and the in-situ polymerized polymer. This ensures that although the composite solid electrolyte membrane contains a high proportion of ceramic solid electrolyte particles, its electrochemical performance is not affected. Simultaneously, the composite solid electrolyte membrane exhibits high ionic conductivity and mechanical strength, improving the stability of the solid-state battery. Through a two-stage polymerization process, firstly, shallow cross-linking is triggered by ultraviolet light to form a semi-cured state of "ceramic framework locked + flowable polymer phase." Then, simultaneous hot pressing and polymerization: after stacking, pressure and high temperature are applied, causing the uncured polymer to flow and fill the pores of the negative electrode. Simultaneously, a thermal initiator completes deep polymerization, achieving "in-situ interfacial molecular anchoring," improving the interfacial state, reducing sheet resistance, and increasing the electrochemical window, thereby enhancing the cycle performance of the solid-state battery.

[0010] The "high ceramic content-dual solidification in-situ integration" technology proposed in this invention provides a new approach for all-solid-state batteries.

[0011] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a composite solid electrolyte membrane with high ceramic content, the preparation method comprising:

[0012] Ceramic solid electrolyte particles and silane coupling agent are added to a solvent to form a mixed solution. The mixed solution is ball-milled and then vacuum-dried to allow the silane coupling agent to undergo a hydrolysis-condensation reaction on the particle surface, exposing and fixing the organic side chains on the particle surface, thus obtaining ceramic solid electrolyte particles activated by silane coupling agent.

[0013] The crosslinking agent, organic monomer, plasticizer and lithium salt are mixed evenly in proportion, and then the ultraviolet photoinitiator and thermal initiator are added and mixed evenly to obtain the in-situ polymerization solution.

[0014] The ceramic solid electrolyte particles activated by the silane coupling agent are ball-milled and mixed with the in-situ polymerization solution to obtain a solid electrolyte slurry.

[0015] The solid electrolyte slurry is coated onto the positive electrode to obtain a composite solid electrolyte membrane precursor.

[0016] The composite solid electrolyte membrane precursor is irradiated with ultraviolet light, and the organic monomers and crosslinking agents on the surface of the composite solid electrolyte membrane precursor are polymerized in situ by the ultraviolet photoinitiator to form a shallow crosslinked curing region on the membrane surface, thereby obtaining a pre-cured composite solid electrolyte membrane. The shallow crosslinked curing region is used to lock the ceramic solid electrolyte particles in a fixed spatial framework to avoid precipitation or agglomeration during subsequent hot pressing and polymerization processes.

[0017] A negative electrode sheet is placed on the surface of the pre-cured composite solid electrolyte membrane, and then hot-pressed. During the hot-pressing process, a thermal initiator initiates the in-situ polymerization of the remaining organic monomers and crosslinking agents to form a three-dimensional network polymer structure. This drives the uncured polymer phase to penetrate and fill the pores on the negative electrode surface, achieving molecular-level anchoring of the electrolyte membrane and the negative electrode interface, thus forming a composite solid electrolyte membrane with high ceramic content.

[0018] In the composite solid electrolyte membrane with high ceramic content, the mass of the ceramic solid electrolyte particles accounts for 60% to 90% of the total mass of the composite solid electrolyte membrane with high ceramic content.

[0019] Preferably, the particle size Dv50 of the ceramic solid electrolyte particles is 50 nm to 5 μm.

[0020] The ceramic solid electrolyte particles include: garnet-type oxide solid electrolyte Li7Al3B12O 12 Perovskite oxide solid electrolyte Li 3x A2 2 / 3-x B2O3, NASICON-type oxide solid electrolyte Li 1+y A3 y B3 2-y (PO4)3, fluoride oxide solid electrolyte Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Fluoride oxide solid electrolyte Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Fluoride oxide solid electrolyte Li₂VO₂F, fluoride oxide solid electrolyte Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 fluoride oxide solid electrolyte Li m La n M1 a M2b M3 c One or more of O6F; wherein, 0.01≤x≤0.5, 0.01≤y≤0.5, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3, 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2; A1 is one or more of La, Ca, Sr, Ba, K, B1 is one or more of Zr, Ta, Nb, Hf; A2 is one or more of La, Al, Mg, Fe, Ta, B2 is one or more of Ti, Nb, Sr, Pr; A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, La, B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, Hf; M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn; M2 is one or more of Nb, Sb, Bi, V, Ta; M3 is one or more of W, Cr, Mo, Mn.

[0021] The silane coupling agent comprises one or more of the following: γ-aminopropyltriethoxysilane (KH-550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and γ-(methacryloyloxy)propyltrimethoxysilane (KH-570); the mass ratio of the silane coupling agent to the ceramic solid electrolyte particles is 0.5:100 to 5:100.

[0022] The solvent includes ethanol; the solid content of the mixed solution is 10wt% to 40wt%.

[0023] The ball milling process is performed at a speed of 300 rpm to 500 rpm for 1 hour to 8 hours.

[0024] The vacuum drying temperature is 50℃~80℃, and the vacuum drying time is 1 hour~8 hours.

[0025] Preferably, the mass ratio of the crosslinking agent, the organic monomer, the plasticizer and the lithium salt is [4-6]:[2-3]:[5-8]:[2-3].

[0026] The crosslinking agent includes: polyethylene glycol diacrylate-200 (PEGDA-200).

[0027] The organic monomers include one or more of butyl acrylate (BA), triethylene glycol dimethacrylate (TEGDMA), ethylene ethylene carbonate (VEC), or trimethylolpropane triacrylate (TMPTA).

[0028] The plasticizer includes one or more of the following: succinic anhydride (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC).

[0029] The lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium dioxolane borate (LiBOB).

[0030] The mass ratio of the ultraviolet photoinitiator to the thermal initiator is 1:9 to 9:1.

[0031] The ultraviolet photoinitiator includes 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide (TPO).

[0032] The thermal initiator includes azobisisobutyronitrile (AIBN).

[0033] The total mass ratio of the ultraviolet photoinitiator and the thermal initiator to the mass ratio of the in-situ polymerization solution is 0.5:100 to 5:100.

[0034] Preferably, the ball milling speed is 300 rpm to 500 rpm, and the ball milling time is 1 hour to 8 hours.

[0035] Preferably, the coating thickness is 5μm to 20μm.

[0036] The wavelength of the ultraviolet light is 280nm to 400nm, and the irradiation time is 10min to 60min.

[0037] The hot pressing temperature is 50℃~80℃, the pressure is 0.5MPa~3MPa, and the time is 10min~60min.

[0038] Preferably, the positive electrode sheet includes any one of the following: a positive electrode sheet containing lithium cobalt oxide, a positive electrode sheet containing ternary materials, a positive electrode sheet containing lithium manganese oxide, and a positive electrode sheet containing lithium iron phosphate.

[0039] The negative electrode sheet includes any one of the following: lithium metal sheet, negative electrode sheet containing silicon-carbon negative electrode material, negative electrode sheet containing graphite, negative electrode sheet containing graphene, and negative electrode sheet containing transition metal.

[0040] In a second aspect, the present invention provides a composite solid electrolyte membrane with high ceramic content prepared by the preparation method described in the first aspect, the composite solid electrolyte membrane comprising: a polymer with a three-dimensional network structure polymerized in situ, and lithium salt and ceramic solid electrolyte particles activated by a silane coupling agent dispersed in the polymer.

[0041] The polymer is formed by in-situ prepolymerization of organic monomers, crosslinking agents and plasticizers on the surface of a composite solid electrolyte membrane precursor initiated by an ultraviolet photoinitiator, followed by in-situ polymerization of the remaining organic monomers, crosslinking agents and plasticizers initiated by a thermal initiator during hot pressing.

[0042] The ceramic solid electrolyte particles, which have been activated by silane coupling agent, are covalently bonded to the polymer.

[0043] In the composite solid electrolyte membrane with high ceramic content, the mass of the ceramic solid electrolyte particles accounts for 60% to 90% of the total mass of the composite solid electrolyte membrane with high ceramic content.

[0044] Preferably, the ultraviolet photoinitiator includes 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide (TPO).

[0045] The organic monomers include one or more of butyl acrylate (BA), triethylene glycol dimethacrylate (TEGDMA), ethylene ethylene carbonate (VEC), or trimethylolpropane triacrylate (TMPTA).

[0046] The crosslinking agent includes: polyethylene glycol diacrylate-200 (PEGDA-200).

[0047] The plasticizer includes one or more of the following: succinic anhydride (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC).

[0048] The thermal initiator includes azobisisobutyronitrile (AIBN); the lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium dioxolaneborate (LiBOB); the lithium salt accounts for 1% to 20% of the mass of the composite solid electrolyte membrane.

[0049] Preferably, the particle size Dv50 of the ceramic solid electrolyte particles is 50 nm to 5 μm.

[0050] The ceramic solid electrolyte particles include: garnet-type oxide solid electrolyte Li7Al3B12O 12 Perovskite oxide solid electrolyte Li 3x A2 2 / 3-x B2O3, NASICON-type oxide solid electrolyte Li 1+y A3 y B3 2-y (PO4)3, fluoride oxide solid electrolyte Li 1.5 Al 0.5Ge 1.5 (PO4) 2.9 F 0.1 Fluoride oxide solid electrolyte Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Fluoride oxide solid electrolyte Li₂VO₂F, fluoride oxide solid electrolyte Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Fluoride oxide solid electrolyte Li m La n M1 a M2 b M3 c One or more of O6F; wherein, 0.01≤x≤0.5, 0.01≤y≤0.5, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3, 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2; A1 is one or more of La, Ca, Sr, Ba, K, B1 is one or more of Zr, Ta, Nb, Hf; A2 is one or more of La, Al, Mg, Fe, Ta, B2 is one or more of Ti, Nb, Sr, Pr; A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, La, B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, Hf; M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn; M2 is one or more of Nb, Sb, Bi, V, Ta; M3 is one or more of W, Cr, Mo, Mn.

[0051] The silane coupling agent includes one or more of the following: γ-aminopropyltriethoxysilane (KH-550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and γ-(methacryloyloxy)propyltrimethoxysilane (KH-570).

[0052] Thirdly, the present invention provides a solid-state battery, the solid-state battery comprising a composite solid electrolyte membrane with high ceramic content prepared by the preparation method described in the first aspect above, or comprising a composite solid electrolyte membrane with high ceramic content described in the second aspect above.

[0053] The present invention provides a composite solid electrolyte membrane with high ceramic content, its preparation method and application, which has the following technical effects.

[0054] This invention involves mixing ceramic solid electrolyte particles activated by a silane coupling agent with an in-situ polymerization solution containing a crosslinking agent, organic monomers, plasticizer, lithium salt, ultraviolet photoinitiator, and thermal initiator to form a solid electrolyte slurry. The ceramic solid electrolyte particles account for 60% to 90% of the total mass of the composite solid electrolyte membrane. The solid electrolyte slurry is coated onto a positive electrode. First, the shallow organic monomers and crosslinking agent undergo in-situ polymerization initiated by an ultraviolet photoinitiator. Then, a negative electrode is covered and hot-pressed. The remaining organic monomers and crosslinking agents undergo in-situ polymerization initiated by a thermal initiator, forming a high-ceramic-content composite electrolyte membrane with high ionic conductivity, low surface resistivity, and high electrochemical window, as well as an all-solid-state battery containing this composite solid electrolyte membrane.

[0055] This invention activates ceramic solid electrolyte particles using a silane coupling agent, causing the silane coupling agent to undergo a hydrolysis-condensation reaction on the particle surface. This exposes and fixes the organic side chains on the particle surface, making them "surface-active groups" that can participate in polymer reactions. This solves the dispersion problem of ceramic solid electrolyte particles and establishes a bridge between the ceramic solid electrolyte particles and the in-situ polymerized polymer through covalent bonding, thereby reducing interfacial impedance. As a result, although the composite solid electrolyte membrane contains a high proportion of ceramic solid electrolyte particles, its electrochemical performance is not affected. At the same time, the composite solid electrolyte membrane also has high ionic conductivity and mechanical strength, improving the stability of solid-state batteries.

[0056] This invention employs two in-situ polymerization processes: photopolymerization and thermal polymerization. First, ultraviolet light triggers the curing of shallow cross-linked regions, forming a semi-cured state of "supporting framework locking ceramic particles + flowable polymer phase." This rapidly polymerizes shallow organic monomers and cross-linking agents in situ, creating a "supporting framework" that pre-shapes the surface of the solid electrolyte slurry. This locks the ceramic solid electrolyte particles within a fixed spatial framework, preventing precipitation or agglomeration during subsequent hot pressing and polymerization. Then, hot pressing and polymerization occur simultaneously. After stacking, pressure and high temperature are applied, causing the uncured polymer to flow and fill the pores of the negative electrode. Simultaneously, a thermal initiator completes deep polymerization, driving the uncured polymer phase to penetrate and fill the pores on the negative electrode surface. This achieves molecular-level anchoring at the interface between the electrolyte membrane and the negative electrode, realizing "in-situ interface molecular anchoring," improving the interface state, reducing sheet resistance, and increasing the electrochemical window, thereby enhancing the cycle performance of the solid-state battery.

[0057] This invention constructs a ceramic framework by adding an ultra-high content of ceramic-like solid electrolyte particles. Lithium ions can migrate rapidly along the surface of the highly conductive ceramic-like solid electrolyte particles or through the contact points between the particles, while an extremely thin polymer layer is responsible for bonding and flexibility, and also assists in transport. This structure is expected to enable the ionic conductivity of the composite electrolyte to approach that of pure ceramic electrolytes. Furthermore, the dual-curing process of pre-curing and original polymerization curing is more suitable for existing roll-to-roll large-scale manufacturing processes. Attached Figure Description

[0058] Figure 1 A flowchart illustrating the preparation method of a composite solid electrolyte membrane with high ceramic content provided in an embodiment of the present invention. Detailed Implementation

[0059] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0060] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0061] This invention provides a high-ceramic-content composite solid electrolyte membrane, comprising: a polymer with an in-situ polymerized three-dimensional network structure, and lithium salt and ceramic solid electrolyte particles activated by a silane coupling agent dispersed in the polymer.

[0062] The polymer with a three-dimensional network structure is formed by in-situ prepolymerization of organic monomers, crosslinking agents and plasticizers on the surface of the composite solid electrolyte membrane precursor initiated by ultraviolet photoinitiator, and then in-situ polymerization of the remaining organic monomers, crosslinking agents and plasticizers initiated by thermal initiator during hot pressing.

[0063] Specifically, the organic monomers include one or more of the following: butyl acrylate (BA), triethylene glycol dimethacrylate (TEGDMA), ethylene ethylene carbonate (VEC), or trimethylolpropane triacrylate (TMPTA).

[0064] Crosslinking agents include: polyethylene glycol diacrylate-200 (PEGDA-200).

[0065] Ultraviolet photoinitiators include: 2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO); thermal initiators include: azobisisobutyronitrile (AIBN).

[0066] The mass ratio of ultraviolet photoinitiator to thermal initiator is 1:9 to 9:1, and can be any mass ratio within this range, such as 1:9, 2:9, 3:9, 4:9, 5:9, 6:9, 7:9, 8:9, 9:9, 9:8, 9:7, 9:6, 9:5, 9:4, 9:3, 9:1, etc., but is not limited to the listed mass ratios. Other unlisted mass ratios within this range are also applicable.

[0067] Plasticizers include one or more of the following: succinic anhydride (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC).

[0068] The lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium dioxolane borate (LiBOB); the mass percentage of the lithium salt in the polymer is 1% to 20%, and can be any value within this range, such as: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0069] The ceramic solid electrolyte particles are activated by silane coupling agents, which include one or more of the following: γ-aminopropyltriethoxysilane (KH-550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and γ-(methacryloyloxy)propyltrimethoxysilane (KH-570).

[0070] Ceramic solid electrolyte particles activated by silane coupling agents are covalently bonded to the polymer.

[0071] In the composite solid electrolyte membrane with high ceramic content provided in the embodiments of the present invention, the mass of ceramic solid electrolyte particles accounts for 60% to 90% of the total mass of the composite solid electrolyte membrane with high ceramic content. It can be any value within this range, such as 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0072] The particle size Dv50 of ceramic solid electrolyte particles is 50nm to 5μm, and can be any value within this range, such as: 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 2μm, 3μm, 4μm, 5μm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0073] In this invention, the particle size Dv50 of the ceramic solid electrolyte particles refers to the volume median particle size of the material, representing the particle size corresponding to 50% of the material's volume distribution, a meaning known in the art. The particle size Dv50 of the ceramic solid electrolyte particles provided in this embodiment can be determined using instruments and conventional methods known in the art. Specifically, 1g of material sample is weighed and added to 20ml of deionized water, then 50ul of a 1% (w / w) aqueous solution of ethyl phenyl polyethylene glycol dispersant is added. The mixture is sonicated for 5 minutes, and then the dispersion is added to a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd. for particle size determination. The Dv50 value is then read.

[0074] Ceramic solid electrolyte particles include: garnet-type oxide solid electrolyte Li7Al3B12O 12 Perovskite oxide solid electrolyte Li 3x A2 2 / 3-x B2O3, NASICON-type oxide solid electrolyte Li 1+y A3 y B3 2-y (PO4)3, fluoride oxide solid electrolyte Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Fluoride oxide solid electrolyte Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Fluoride oxide solid electrolyte Li₂VO₂F, fluoride oxide solid electrolyte Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Fluoride oxide solid electrolyte Li m La n M1 a M2 b M3 cOne or more of O6F; wherein, 0.01≤x≤0.5, 0.01≤y≤0.5, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3, 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2; A1 is one or more of La, Ca, Sr, Ba, K, B1 is one or more of Zr, Ta, Nb, Hf; A2 is one or more of La, Al, Mg, Fe, Ta, B2 is one or more of Ti, Nb, Sr, Pr; A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, La, B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, Hf; M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn; M2 is one or more of Nb, Sb, Bi, V, Ta; M3 is one or more of W, Cr, Mo, Mn.

[0075] The ceramic solid electrolyte particles used in the embodiments of the present invention are preferably fluoride oxide solid electrolytes Li. m La n M1 a M2 b M3 c One or more of O6F; wherein, 0.01≤x≤0.5, 0.01≤y≤0.5, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3, 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2; M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn; M2 is one or more of Nb, Sb, Bi, V, Ta; M3 is one or more of W, Cr, Mo, Mn. This is because the fluoride oxide solid electrolyte Li m La n M1 a M2 b M3 c O6F possesses high mechanical strength, high density, high purity, as well as high volumetric energy density, low internal resistance, and excellent ion conductivity. Furthermore, Li... m La n M1 a M2 b M3 c O6F has a rigid structure with adjustable elemental composition. By introducing diverse coordination environments through multivalent cation doping, it can form open channels that facilitate lithium-ion transport. At the same time, fluorine doping can further enhance the polarity and interfacial wettability of the material, improve the interfacial contact with the electrolyte and electrodes, and reduce interfacial impedance.

[0076] This invention provides a method for preparing the above-mentioned high ceramic content composite solid electrolyte membrane, such as... Figure 1 As shown, the specific steps include:

[0077] Step 110: Add ceramic solid electrolyte particles and silane coupling agent to a solvent to form a mixed solution. Perform ball milling on the mixed solution and then vacuum dry it to allow the silane coupling agent to complete the hydrolysis-condensation reaction on the particle surface, thereby exposing and fixing the organic side chains on the particle surface, and obtaining ceramic solid electrolyte particles that have been activated by silane coupling agent.

[0078] Among them, ceramic solid electrolyte particles include: garnet-type oxide solid electrolyte Li7Al3B12O 12 Perovskite oxide solid electrolyte Li 3x A2 2 / 3-x B2O3, NASICON-type oxide solid electrolyte Li 1+y A3 y B3 2-y (PO4)3, fluoride oxide solid electrolyte Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 fluoride oxide solid electrolyte Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Fluoride oxide solid electrolyte Li₂VO₂F, fluoride oxide solid electrolyte Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 fluoride oxide solid electrolyte Li m La n M1 a M2 b M3 cOne or more of O6F; wherein, 0.01≤x≤0.5, 0.01≤y≤0.5, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3, 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2; A1 is one or more of La, Ca, Sr, Ba, K, B1 is one or more of Zr, Ta, Nb, Hf; A2 is one or more of La, Al, Mg, Fe, Ta, B2 is one or more of Ti, Nb, Sr, Pr; A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, La, B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, Hf; M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn; M2 is one or more of Nb, Sb, Bi, V, Ta; M3 is one or more of W, Cr, Mo, Mn. The particle size Dv50 of ceramic solid electrolyte particles is between 50 nm and 5 μm.

[0079] Silane coupling agents include one or more of the following: γ-aminopropyltriethoxysilane (KH-550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and γ-(methacryloyloxy)propyltrimethoxysilane (KH-570).

[0080] The mass ratio of the silane coupling agent to the ceramic solid electrolyte particles is 0.5:100 to 5:100.

[0081] Solvents include, but are not limited to, ethanol; the solid content of the mixed solution is 10 wt% to 40 wt%.

[0082] The ball milling speed is 300 rpm to 500 rpm, and the ball milling time is 1 hour to 8 hours.

[0083] The vacuum drying temperature is 50℃~80℃, and the vacuum drying time is 1 hour~8 hours.

[0084] In this step, the silane coupling agent undergoes hydrolysis in a solvent environment, converting its terminal –Si–OR group into –Si–OH. Under ball milling, the hydrolyzed silane coupling agent –Si–OH condenses with the –OH groups on the surface of the ceramic solid electrolyte particles, forming a –Si–O–M bond (where M is a metal element contained on the surface of the ceramic solid electrolyte particles, such as Li, Al, Zr, etc.). The drying step removes the solvent and further promotes the condensation reaction between the silane coupling agent and the ceramic surface. Thus, the organic side chain –R–X at the other end of the silane coupling agent is fixed on the surface of the ceramic solid electrolyte particles, becoming a "surface-active group" that can participate in polymer reactions. Here, X can be alkenyl, amino, epoxy, methacryloxy, etc.

[0085] Step 120: Mix the crosslinking agent, organic monomer, plasticizer and lithium salt in proportion, then add the ultraviolet photoinitiator and thermal initiator, and mix evenly to obtain an in-situ polymerization solution.

[0086] The mass ratio of crosslinking agent, organic monomer, plasticizer and lithium salt is [4-6]: [2-3]: [5-8]: [2-3].

[0087] Crosslinking agents include: polyethylene glycol diacrylate-200 (PEGDA-200).

[0088] The organic monomers include one or more of the following: butyl acrylate (BA), triethylene glycol dimethacrylate (TEGDMA), ethylene ethylene carbonate (VEC), or trimethylolpropane triacrylate (TMPTA).

[0089] Plasticizers include one or more of the following: succinic anhydride (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC).

[0090] Lithium salts include one or more of the following: lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium dioxolane borate (LiBOB).

[0091] The mass ratio of ultraviolet photoinitiator to thermal initiator is 1:9 to 9:1.

[0092] Ultraviolet photoinitiators include: 2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO).

[0093] Thermal initiators include azobisisobutyronitrile (AIBN).

[0094] The mass ratio of the total mass of the UV photoinitiator and thermal initiator to the mass of the in-situ polymerization solution is 0.5:100 to 5:100.

[0095] Step 130: The ceramic solid electrolyte particles activated by silane coupling agent are ball-milled and mixed with the in-situ polymerization solution to obtain a solid electrolyte slurry.

[0096] The ball milling speed is 300 rpm to 500 rpm, and the ball milling time is 1 hour to 8 hours.

[0097] During the ball milling process, the ceramic solid electrolyte particles and polymer precursors (crosslinking agents, organic monomers, etc.) are uniformly dispersed through ball milling, so that the organic functional groups exposed on the surface of the ceramic solid electrolyte particles are uniformly distributed in the slurry.

[0098] Step 140: The solid electrolyte slurry is coated onto the positive electrode to obtain the composite solid electrolyte membrane precursor.

[0099] The coating method is a conventional method, such as roller coating or blade coating; the coating thickness is 5μm to 20μm.

[0100] Step 150: The composite solid electrolyte membrane precursor is irradiated with ultraviolet light. The organic monomers and crosslinking agents on the surface of the composite solid electrolyte membrane precursor are polymerized in situ by ultraviolet photoinitiator to form a shallow crosslinked curing region on the membrane surface, thereby obtaining a pre-cured composite solid electrolyte membrane.

[0101] The wavelength of the ultraviolet light is 280nm to 400nm, and the irradiation time is 10min to 60min.

[0102] The shallow cross-linked curing region is used to lock ceramic solid electrolyte particles within a fixed spatial framework to prevent precipitation or agglomeration during subsequent hot pressing and polymerization processes.

[0103] In this step, shallow cross-linking is triggered by ultraviolet (UV) light irradiation, forming a cross-linked network on the surface of the composite solid electrolyte membrane, which acts as a "skeleton lock." This allows the high-content ceramic particles to be fixed in a relatively stable distribution position, preventing significant migration, precipitation, or agglomeration during subsequent hot pressing and polymerization processes, thereby ensuring the structural uniformity of the electrolyte membrane.

[0104] Because UV light has limited penetration depth in systems containing ceramic particles, it can only penetrate the shallow layer of the film, thus only curing the surface layer (typically tens to hundreds of micrometers), while the interior remains in a monomer / oligomery state. The monomers and crosslinking agents in the internal region remain unpolymerized, maintaining good fluidity. This allows the uncured polymer phase inside to flow and redistribute under pressure during subsequent hot pressing. Simultaneously, the surface crosslinked network formed in this step is not a completely barrier-free dense layer, but a semi-cured network layer. It maintains macroscopic shape stability while allowing the uncured polymer phase inside to migrate through micropores or gaps under pressure.

[0105] After UV curing, a cross-linked polymer framework can be rapidly formed on the surface, macroscopically stabilizing the entire film's structural framework. This inhibits the large-scale migration, accumulation, or precipitation of ceramic solid electrolyte particles inside the film during subsequent hot pressing. In other words, by constructing a cross-linked network on the surface to stabilize the entire film's structural framework, the high content of ceramic particles distributed throughout the film maintains its original uniform distribution and does not migrate or agglomerate during subsequent hot pressing and deep polymerization. At the same time, the surface cross-linked network, acting as a "supporting framework," maintains morphological stability and provides constraint and guidance for the flow and penetration of the uncured polymer phase inside, thus balancing overall structural uniformity and interfacial filling capacity.

[0106] Step 160: Cover the surface of the pre-cured composite solid electrolyte membrane with the negative electrode sheet, and then perform hot pressing. During the hot pressing process, the remaining organic monomers and crosslinking agents are initiated to undergo in-situ polymerization to form a three-dimensional network polymer structure, which drives the uncured polymer phase to penetrate and fill the pores on the negative electrode surface, thereby achieving molecular-level anchoring of the electrolyte membrane and the negative electrode interface and forming a composite solid electrolyte membrane with high ceramic content.

[0107] There are no special restrictions on the positive electrode sheet; any positive electrode sheet that can be used in solid-state batteries is acceptable. The positive electrode sheet is prepared using conventional methods. The positive electrode sheet includes any one of the following: lithium cobalt oxide positive electrode sheet, ternary material positive electrode sheet, lithium manganese oxide positive electrode sheet, and lithium iron phosphate positive electrode sheet. The ternary material can be NCM523, NCM622, NCM811, etc.

[0108] There are no special restrictions on the negative electrode sheet; any negative electrode sheet that can be used in solid-state batteries is acceptable. The negative electrode sheet is prepared using conventional methods. The negative electrode sheet includes any one of the following: lithium metal sheet, negative electrode sheet containing silicon-carbon negative electrode material, negative electrode sheet containing graphite, negative electrode sheet containing graphene, and negative electrode sheet containing transition metal.

[0109] The hot pressing temperature is 50℃~80℃, the pressure is 0.5MPa~3MPa, and the time is 10min~60min.

[0110] During the hot-pressing stage, the pre-cured surface layer acts as a "support layer," ensuring the overall structure does not collapse. The polymer phase, which remained fluid in the previous step, is driven to penetrate the surface and pore structure of the negative electrode under pressure and temperature. The high temperature and pressure not only reduce the viscosity of the polymer phase but also force the uncured polymer to flow outwards, entering the negative electrode pores, and finally completing deep cross-linking under the action of the thermal initiator. As the thermal initiator initiates deep polymerization, the polymer phase that has penetrated the negative electrode pores solidifies in situ, thus achieving molecular-level anchoring.

[0111] The core advantage of this invention's stepwise curing method lies in: first constructing a stable ceramic-polymer framework, then utilizing the retained flowing polymer phase to achieve interfacial penetration and molecular anchoring, ultimately balancing the structural uniformity and interfacial bonding of the membrane. In other words, this invention achieves a "first lock the framework, then fill the interface" process through surface photoinitiated pre-curing followed by hot-press curing, resulting in a continuous three-dimensional cross-linked network between the composite electrolyte membrane and the negative electrode—a process beyond simple physical contact. This reduces interfacial contact resistance, improves mechanical bonding, and alleviates interfacial delamination during cycling.

[0112] The preparation method provided in this invention ultimately forms a composite solid electrolyte membrane and a solid battery containing the composite solid electrolyte membrane through in-situ polymerization.

[0113] This invention utilizes in-situ polymerization to modify ceramic solid electrolyte particles, addressing their dispersibility issues. A bridge is established between the particles and the in-situ polymerization solution, reducing interfacial impedance. By adding an ultra-high content of ceramic particles to construct a ceramic framework, lithium ions can migrate rapidly along the highly conductive ceramic particle surface or through contact points between particles. The extremely thin polymer layer provides adhesion, flexibility, and facilitates transport. This structure promises to achieve an ionic conductivity of the composite electrolyte approaching that of pure ceramic electrolytes. Solid-state batteries containing this composite solid electrolyte membrane exhibit high safety and good cycle performance.

[0114] To better understand the technical solution provided by the present invention, the preparation process and characteristics of the high ceramic content composite solid electrolyte membrane of the present invention are illustrated below with several specific examples.

[0115] Example 1

[0116] This embodiment provides a method for preparing a composite solid electrolyte membrane with high ceramic content.

[0117] First, prepare ceramic solid electrolyte particles Li 1.25 La 0.58The Nb₂O₆F process specifically includes: mixing lithium carbonate, lanthanum trioxide, and niobium pentoxide in a stoichiometric ratio of 1:1:4, with a total mass of 2 kg, to obtain a first mixture. The first mixture is placed in a box furnace and heated to 300°C at a rate of 5°C / min, held for 2 hours, and then further heated to 1000°C at a rate of 5°C / min, held for 6 hours to obtain a precursor powder. Lithium fluoride, lanthanum fluoride, and the aforementioned precursor powder are mixed in a stoichiometric ratio of 78:8:100 and ball-milled to obtain a second mixture. The second mixture is transferred to a tube furnace, and nitrogen is introduced to maintain a nitrogen atmosphere. The temperature is increased to 900°C at a rate of 2°C / min, held for 5 hours, and after discharge, sieved to obtain ceramic-like solid electrolyte particles (Li₂O₆F) with a particle size Dv₅₀ of 100 nm. 1.25 La 0.58 Nb2O6F.

[0118] The preparation process of a composite solid electrolyte membrane with high ceramic content includes the following steps.

[0119] (1) 200g of ceramic solid electrolyte particles Li with a particle size Dv50 of 100nm were placed in the container. 1.25 La 0.58 Nb2O6F and 2g of silane coupling agent KH-550 were added to an ethanol solution to form a mixed solution with a solid content of 20%. The mixed solution was placed in a ball mill and ball-milled at 500 rpm for 3 hours. Then it was placed in a vacuum dryer and vacuum dried at 70°C for 6 hours to allow the silane coupling agent to complete the hydrolysis-condensation reaction on the particle surface, exposing and fixing the organic side chains on the particle surface, thus obtaining ceramic solid electrolyte particles that have been activated by the silane coupling agent.

[0120] (2) PEGDA-200 crosslinking agent, BA organic monomer, SN plasticizer, and LiTFSI lithium salt were mixed in a mass ratio of 6:2:5:2, totaling 100g. Then, UV photoinitiator TPO and thermal initiator AIBN were added in a mass ratio of 1:1, and the mixture was stirred until homogeneous to obtain an in-situ polymerization solution. The total mass of the UV photoinitiator and thermal initiator accounted for 0.8% of the total mass of the in-situ polymerization solution.

[0121] (3) The ceramic solid electrolyte particles that have been activated by silane coupling agent are placed in a ball mill and the in-situ polymerization solution is ball milled at 500 rpm for 3 hours to obtain a solid electrolyte slurry.

[0122] (4) The solid electrolyte slurry is coated on a commercial lithium cobalt oxide positive electrode with a coating thickness of 10 μm to obtain a composite solid electrolyte membrane precursor.

[0123] (5) The precursor of the composite solid electrolyte membrane is irradiated with ultraviolet light with a wavelength of 350 nm and an irradiation time of 20 min. The organic monomers and crosslinking agents on the surface of the precursor of the composite solid electrolyte membrane are polymerized in situ by ultraviolet photoinitiator to form a shallow crosslinked curing region on the membrane surface, thereby obtaining a pre-cured composite solid electrolyte membrane.

[0124] (6) A commercial graphite negative electrode sheet is placed on the surface of the pre-cured composite solid electrolyte membrane. Then, it is hot-pressed at a pressure of 1 MPa and a temperature of 70°C for 50 min. During the hot-pressing process, the remaining organic monomers and crosslinking agents are polymerized in situ to form a three-dimensional network structure of polymer, which drives the uncured polymer phase to penetrate and fill the pores on the negative electrode surface, thereby achieving molecular-level anchoring of the electrolyte membrane and the negative electrode interface and forming a composite solid electrolyte membrane with high ceramic content. The mass of ceramic solid electrolyte particles accounts for 80% of the total mass of the composite solid electrolyte membrane.

[0125] Example 2

[0126] This embodiment provides a method for preparing a composite solid electrolyte membrane with high ceramic content. The difference from Example 1 is that step (1) uses ceramic solid electrolyte particles (Li). 1.25 La 0.58 The particle size Dv50 of Nb2O6F is 1 μm, and the other preparation processes are the same as in Example 1.

[0127] Example 3

[0128] This embodiment provides a method for preparing a composite solid electrolyte membrane with high ceramic content. The difference from Example 1 is in step (2), where the mass ratio of crosslinking agent PEGDA-200, organic monomer BA, plasticizer SN and lithium salt LiTFSI is 4:2:8:3, the mass ratio of ultraviolet photoinitiator TPO and thermal initiator AIBN is 3:7, and the total mass of ultraviolet photoinitiator and thermal initiator accounts for 1% of the total mass of the in-situ polymerization solution; other preparation processes are the same as in Example 1.

[0129] Example 4

[0130] This embodiment provides a method for preparing a composite solid electrolyte membrane with high ceramic content. The difference from Embodiment 1 is that the mass of ceramic solid electrolyte particles accounts for 75% of the total mass of the composite solid electrolyte membrane. The other preparation processes are the same as in Embodiment 1.

[0131] Example 5

[0132] This embodiment provides a method for preparing a composite solid electrolyte membrane with high ceramic content, which differs from Embodiment 1 in steps (4) and (5).

[0133] Step (4) involves coating a solid electrolyte slurry onto a commercial ternary material (NCM811) positive electrode with a coating thickness of 15 μm to obtain a composite solid electrolyte membrane precursor.

[0134] Step (5): The composite solid electrolyte membrane precursor is irradiated with ultraviolet light with a wavelength of 400 nm and an irradiation time of 40 min. The organic monomers and crosslinking agents on the surface of the composite solid electrolyte membrane precursor are prepolymerized in situ by the ultraviolet photoinitiator to obtain the precured composite solid electrolyte membrane.

[0135] The other preparation processes are the same as in Example 1.

[0136] Example 6

[0137] This embodiment provides a method for preparing a composite solid electrolyte membrane with high ceramic content. The difference from Embodiment 1 is in step (6), where a commercial graphite negative electrode sheet is covered on the surface of the pre-cured composite solid electrolyte membrane, and then hot-pressed at a pressure of 2 MPa and a temperature of 80°C for 40 min. During the hot-pressing process, the remaining organic monomers and crosslinking agents are initiated by a thermal initiator to undergo in-situ polymerization to form a polymer with a three-dimensional network structure, thereby obtaining a composite solid electrolyte membrane with high ceramic content.

[0138] The other preparation processes are the same as in Example 1.

[0139] Example 7

[0140] This embodiment provides a method for preparing a composite solid electrolyte membrane with high ceramic content. The difference from Embodiment 1 is that the ceramic solid electrolyte particles selected in step (1) are Li₂ with a particle size Dv₅₀ of 100 nm. 1.3 Al 0.3 Ti 1.7 (PO4)3 (LATP); other preparation steps are the same as in Example 1.

[0141] To better illustrate the effects of the embodiments of the present invention, a comparative example is provided to be made with the embodiments described above.

[0142] Comparative Example 1

[0143] This comparative example provides a method for preparing a solid electrolyte membrane, which uses ceramic solid electrolyte particles with a particle size Dv50 of 100 nm, as used in Example 1. 1.25 La 0.58Nb2O6F is directly cold-pressed into sheets to obtain a solid electrolyte membrane. This solid electrolyte membrane is then assembled with commercial graphite anode sheets and commercial lithium cobalt oxide cathode sheets to form a solid-state battery.

[0144] Comparative Example 2

[0145] This comparative example provides a method for preparing a solid electrolyte membrane. The difference from Example 1 is that ceramic solid electrolyte particles are not used. Instead, the in-situ polymerization solution prepared in step (2) of Example 1 is directly coated on the positive electrode. The polymer electrolyte membrane and the solid battery containing the polymer electrolyte membrane are prepared according to the methods of steps (4), (5) and (6).

[0146] Comparative Example 3

[0147] This comparative example provides a method for preparing a composite solid electrolyte membrane. Unlike Example 1, the method uses a lower content of ceramic solid electrolyte particles and does not employ an initiator-initiated in-situ polymerization of organic monomers. Instead, it involves mixing low-ceramic-content ceramic solid electrolyte particles with a polymer solution to form a slurry, which is then coated onto an electrode and cured by heating. The specific preparation method is as follows.

[0148] A polymer solution was prepared by uniformly mixing 40g of PVDF, 30g of SN and 10g of LiTFSI with 80g of solvent DMF.

[0149] 20g of ceramic solid electrolyte particles Li, which had been activated with a silane coupling agent, were used. 1.25 La 0.58 A solid electrolyte slurry was prepared by mixing Nb2O6F with 80g of polymer solution.

[0150] Solid electrolyte slurry is coated onto a commercial lithium cobalt oxide positive electrode with a coating thickness of 10 μm, and then baked at 80°C for 1 hour to form a composite solid electrolyte membrane. A commercial graphite negative electrode is then covered on top, and the membrane is assembled into a solid-state battery using conventional methods.

[0151] Comparative Example 4

[0152] This comparative example provides a method for preparing a composite solid electrolyte membrane. The difference from Example 1 is that the composite solid electrolyte membrane contains a lower content of ceramic solid electrolyte particles, with the ceramic solid electrolyte particles accounting for 20% of the total mass of the composite solid electrolyte membrane. All other preparation steps are the same as in Example 1.

[0153] Comparative Example 5

[0154] This comparative example provides a method for preparing a composite solid electrolyte membrane. Unlike Example 1, it does not involve in-situ polymerization initiated by ultraviolet photoinitiator or in-situ polymerization initiated by thermal initiator. Instead, it directly casts the membrane for imaging and then heats it to form the composite solid electrolyte membrane, as detailed below.

[0155] (1) The preparation process of ceramic solid electrolyte particles activated by silane coupling agent is the same as that in Example 1.

[0156] (2) Mix 100g of crosslinking agent PEGDA-200, organic monomer BA, plasticizer SN and lithium salt LiTFSI in a mass ratio of 6:2:5:2 to obtain an in-situ polymerization solution.

[0157] (3) The ceramic solid electrolyte particles that have been activated by silane coupling agent are placed in a ball mill and the in-situ polymerization solution is ball milled at 500 rpm for 3 hours to obtain a solid electrolyte slurry.

[0158] (4) The solid electrolyte slurry was cast onto a polytetrafluoroethylene mold with a thickness of 10 μm and cured at 80°C for 1 hour to obtain a composite solid electrolyte membrane. This composite solid electrolyte membrane was then assembled into a solid-state battery using conventional methods with commercial graphite negative electrode sheets and commercial lithium iron phosphate positive electrode sheets. The ceramic solid electrolyte particles accounted for 80% of the total mass of the composite solid electrolyte membrane.

[0159] Comparative Example 6

[0160] This comparative example provides a method for preparing a composite solid electrolyte membrane. Unlike Example 1, it only adds a UV photoinitiator and does not add a thermal initiator. The organic monomers and crosslinking agents are polymerized in situ only through the UV photoinitiator, as detailed below.

[0161] (1) Same as the process in Example 1.

[0162] (2) Mix 100g of crosslinking agent PEGDA-200, organic monomer BA, plasticizer SN and lithium salt LiTFSI in a mass ratio of 6:2:5:2. Then add UV photoinitiator TP0 and mix well to obtain an in-situ polymerization solution. The mass of UV photoinitiator and its percentage of the total mass of the in-situ polymerization solution is 0.8%.

[0163] (3) The process is the same as in Example 1.

[0164] (4) The process is the same as in Example 1.

[0165] (5) The precursor of the composite solid electrolyte membrane is irradiated with ultraviolet light with a wavelength of 350 nm and an irradiation time of 40 min. The organic monomers and crosslinking agents on the surface of the precursor of the composite solid electrolyte membrane are polymerized in situ by ultraviolet photoinitiator to obtain a pre-cured composite solid electrolyte membrane.

[0166] (6) Cover the surface of the pre-cured composite solid electrolyte membrane with a commercial graphite negative electrode sheet, and then hot press it for 50 min at a pressure of 1 MPa and a temperature of 70 °C to obtain a composite solid electrolyte membrane with high ceramic content.

[0167] Comparative Example 7

[0168] This comparative example provides a method for preparing a composite solid electrolyte membrane. Unlike Example 1, it only adds a thermal initiator and does not add a UV initiator. The organic monomers and crosslinking agents are polymerized in situ only through the thermal initiator, as detailed below.

[0169] (1) Same as the process in Example 1.

[0170] (2) Mix 100g of crosslinking agent PEGDA-200, organic monomer BA, plasticizer SN and lithium salt LiTFSI in a mass ratio of 6:2:5:2. Then add thermal initiator AIBN and mix well to obtain an in-situ polymerization solution. The mass of thermal initiator AIBN and its percentage of the total mass of the in-situ polymerization solution are 0.8%.

[0171] (3) The process is the same as in Example 1.

[0172] (4) The solid electrolyte slurry is coated on a commercial lithium cobalt oxide positive electrode with a coating thickness of 10 μm to obtain a composite solid electrolyte membrane precursor.

[0173] (5) A commercial graphite negative electrode sheet is covered on the surface of the composite solid electrolyte membrane precursor. Then, it is hot-pressed for 50 minutes at a pressure of 1 MPa and a temperature of 70 °C. During the hot-pressing process, the remaining organic monomers and crosslinking agents are polymerized in situ to form a three-dimensional network structure, thus obtaining a composite solid electrolyte membrane with high ceramic content.

[0174] The performance of the high ceramic content composite solid electrolyte membranes of Examples 1-7 and the composite solid electrolyte membranes of Comparative Examples 1-7 were tested as follows.

[0175] 1. Ionic conductivity and surface resistivity tests are as follows.

[0176] (1) Ionic conductivity was tested by electrochemical impedance spectroscopy (EIS) on an electrochemical workstation.

[0177] First, test batteries were prepared. The solid electrolyte slurry prepared in step (3) of Examples 1-7, the in-situ polymerization solution of Comparative Example 2, and the solid electrolyte slurries of Comparative Examples 3, 4, 5, 6, and 7 were coated onto stainless steel (SS) inert electrodes. Then, they were cured according to the solid conditions in each example and comparative example to assemble the test batteries of Examples 1-7, Comparative Example 2, and Comparative Examples 3 to 7. For Comparative Example 1, the cold-pressed solid electrolyte membrane was cut into circular pieces with a diameter of 17 mm and sandwiched between two stainless steel (SS) inert electrodes to assemble the test battery of Comparative Example 1. Then, it was connected to an electrochemical workstation for testing. To ensure the accuracy of the test, the test battery was placed in a constant temperature chamber for temperature control. In the EIS test, the frequency range was set from 0.01 Hz to 1 MHz, and the amplitude voltage was set to 10 mV. The purpose was to accurately measure the resistance of the electrolyte. Next, by analyzing the Nyquist impedance spectrum, the ionic conductivity of the electrolyte can be calculated using the following formula: In the process of determining ionic conductivity, d in the formula represents the thickness of the solid electrolyte film between the stainless steel electrodes, R is the impedance value of the solid electrolyte film read from the Nyquist impedance diagram of EIS, and S represents the effective contact area between the solid electrolyte film and the stainless steel inert electrode. To ensure the accuracy of the measurement, when testing the ionic conductivity at different temperatures, the constant temperature chamber needs to be set to the target temperature and maintained for half an hour to allow the test battery to reach thermal equilibrium. This step ensures the stability of the test environment, thereby allowing for accurate measurement of the ionic conductivity of the solid electrolyte at various temperatures. The ionic conductivity tests of this invention were all conducted at 25±2℃ and humidity less than 50%. Detailed test data are shown in Table 1.

[0178] (2) Calculate the surface resistance. The formula is: Surface resistance = impedance value R × area S of solid electrolyte membrane.

[0179] 2. Electrochemical window test: Specifically, lithium metal sheet is used as the reference electrode and counter electrode, while stainless steel sheet (SS) is used as the working electrode.

[0180] First, lithium / stainless steel (Li|SS) batteries were prepared. The solid electrolyte slurry prepared in step (3) of Examples 1-7, the in-situ polymerization solution of Comparative Example 2, and the solid electrolyte slurries of Comparative Examples 3, 4, 5, 6, and 7 were coated onto stainless steel (SS) inert electrodes. Then, they were cured according to the solid conditions in each example and comparative example to assemble the lithium / stainless steel (Li|SS) batteries of Examples 1-7, Comparative Example 2, and Comparative Examples 3 to 7. Comparative Example 1 was prepared by cutting a cold-pressed solid electrolyte membrane into a circular shape with a diameter of 17 mm and sandwiching it between a stainless steel (SS) sheet and a lithium metal sheet to assemble the lithium / stainless steel (Li|SS) battery of Comparative Example 1. During the test, the lithium / stainless steel (Li|SS) battery was assembled in a glove box and then subjected to linear sweep voltammetry (LSV) test in a constant temperature chamber at room temperature. During testing, the scan rate was set to 1 millivolt per second (mV / s), scanning from the open-circuit voltage to 6V. The electrochemical window was tested, and its upper limit was recorded. The upper limit of the electrochemical window can be used to determine the degree of polymerization of organic monomers and crosslinking agents in the composite solid electrolyte. The test results are detailed in Table 1.

[0181] 3. Cyclic performance testing: The solid-state batteries prepared using Examples 1-7 and Comparative Examples 1-7 were subjected to 500 cycles at a 3C current density using a Blue Electricity Tester. The capacity retention rate was calculated and recorded. The test results are detailed in Table 1.

[0182] Table 1 summarizes the test data for Examples 1-7 and Comparative Examples 1-7:

[0183]

[0184] As can be seen from the data in Table 1, the ionic conductivity of Examples 1-6 is much higher than that of Comparative Examples 1-7, the sheet resistance of Examples 1-6 is significantly higher than that of Comparative Examples 1-7, the electrochemical window of Examples 1-6 is significantly higher than that of Comparative Examples 1-7, and the heat shrinkage temperature of Examples 1-6 is significantly higher than that of Comparative Examples 1-7.

[0185] This is because Comparative Example 1 directly uses ceramic solid electrolyte particles without polymer encapsulation. Its Young's modulus is high, and there are gaps between the particles under cold pressure, which seriously affects the bulk conduction of ions. Therefore, the solid electrolyte membrane of Comparative Example 1 has very low ionic conductivity, sheet resistance and electrochemical window. However, due to the difficulty in film formation, the assembled full cell cannot operate.

[0186] In contrast, Comparative Example 2, which did not add ceramic solid electrolyte particles with high ionic conductivity, although in-situ solidification optimized the interface contact, had low ionic conductivity, which affected the electrochemical performance of the solid electrolyte membrane and thus the cycle performance of the solid battery.

[0187] The preparation method used in Comparative Example 3 is different from that in Example 1. The ceramic solid electrolyte particles are directly mixed with the polymer solution without pre-curing and in-situ polymerization. In addition, the content of ceramic solid electrolyte particles is low. The composite solid electrolyte membrane prepared in Comparative Example 3 has problems such as easy agglomeration and uneven dispersion of ceramic solid electrolyte particles, low ionic conductivity and mechanical strength, and high interfacial impedance. Therefore, the test data is not good.

[0188] The ceramic solid electrolyte particle content in Comparative Example 4 is relatively low. The composite electrolyte membrane prepared from it is essentially a polymer as the continuous phase, which cannot form an efficient ceramic solid electrolyte ion transport channel. This severely limits the performance of the intrinsic high ionic conductivity, and its performance is closer to that of traditional polymer electrolytes. Therefore, the test data is inferior to that of Example 1.

[0189] Although Comparative Example 5 maintained a high content of ceramic solid electrolyte particles, it abandoned the key pre-curing and in-situ polymerization processes, resulting in only simple physical mixing and solid-solid contact between the polymer matrix and ceramic particles. This led to poor interfacial compatibility and a significant increase in interfacial impedance. At the same time, the lack of a hot-pressing step also resulted in insufficient contact between the polymer matrix and the electrodes, ultimately leading to a decline in the overall performance of the battery.

[0190] In the comparative example 6, the organic monomers and crosslinking agents were polymerized in situ using a UV photoinitiator. Since no thermal initiator was added, the organic monomers and crosslinking agents inside the composite solid electrolyte membrane were not deeply initiated during the hot pressing process, resulting in incomplete formation of the internal three-dimensional crosslinking network, which affected ion transport.

[0191] Comparative Example 7 only uses a thermal initiator to initiate in-situ polymerization of organic monomers and crosslinking agents. Since no ultraviolet initiator is added, the curing speed and shape accuracy cannot be improved. The solid electrolyte slurry suffers some mass loss during hot pressing, and the thickness of the final composite solid electrolyte membrane cannot be controlled. Its thickness is less than that of Example 1, thus affecting the performance of the final solid electrolyte membrane.

[0192] The test data for Example 7 were all better than those for Comparative Examples 1-3, but the ionic conductivity, electrochemical window, and cycling capacity retention were all lower than those for Example 1. This is because Example 7 and Example 1 used different types of ceramic solid electrolyte particles. The ceramic solid electrolyte particles in Example 1 were Li... 1.25 La 0.58Compared to the traditional ceramic solid electrolyte particles LATP in Example 7, Nb2O6F has the characteristics of high mechanical strength, high density, high purity, as well as high volumetric energy density, low internal resistance and excellent ion conduction performance.

[0193] The upper limit of the electrochemical window in Table 1 can be used to illustrate the degree of polymerization of organic monomers and crosslinking agents in the composite solid electrolyte membrane. The upper limit of the electrochemical window is the critical voltage value for oxidative decomposition during the testing of the composite solid electrolyte membrane. If the polymerization of organic monomers and crosslinking agents is incomplete during the preparation of the composite solid electrolyte membrane, the residual monomers will preferentially oxidize and decompose, thereby consuming lithium ions and generating byproducts, resulting in a decrease in oxidation potential and a reduction in the upper limit of the electrochemical window. The upper limits of the electrochemical windows in Examples 1-7 are all greater than those in Comparative Examples 1-7, indicating that the composite solid electrolyte membranes prepared by the preparation methods provided in Examples 1-7 have a better degree of polymerization of organic monomers and crosslinking agents.

[0194] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. 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 method for preparing a composite solid electrolyte membrane with high ceramic content, characterized in that, The preparation method includes: Ceramic solid electrolyte particles and silane coupling agent are added to a solvent to form a mixed solution. The mixed solution is ball-milled and then vacuum-dried to allow the silane coupling agent to complete a hydrolysis-condensation reaction on the particle surface, exposing and fixing the organic side chains on the particle surface, thus obtaining ceramic solid electrolyte particles activated by silane coupling agent. The crosslinking agent, organic monomer, plasticizer and lithium salt are mixed evenly in proportion, and then the ultraviolet photoinitiator and thermal initiator are added and mixed evenly to obtain the in-situ polymerization solution. The ceramic solid electrolyte particles activated by silane coupling agent are ball-milled and mixed with the in-situ polymerization solution to obtain a solid electrolyte slurry. The solid electrolyte slurry is coated onto the positive electrode to obtain a composite solid electrolyte membrane precursor. The composite solid electrolyte membrane precursor is irradiated with ultraviolet light, and the organic monomers and crosslinking agents on the surface of the composite solid electrolyte membrane precursor are polymerized in situ by the ultraviolet photoinitiator to form a shallow crosslinked curing region on the membrane surface, thereby obtaining a pre-cured composite solid electrolyte membrane. The shallow crosslinked curing region is used to lock the ceramic solid electrolyte particles in a fixed spatial framework to prevent precipitation or agglomeration during subsequent hot pressing and polymerization processes. A negative electrode sheet is placed on the surface of the pre-cured composite solid electrolyte membrane, and then hot-pressed. During the hot-pressing process, the remaining organic monomers and crosslinking agents are initiated by a thermal initiator to undergo in-situ polymerization to form a three-dimensional network polymer structure. This drives the uncured polymer phase to penetrate and fill the pores on the negative electrode surface, thereby achieving molecular-level anchoring of the electrolyte membrane and the negative electrode interface and forming a composite solid electrolyte membrane with high ceramic content. In the composite solid electrolyte membrane with high ceramic content, the mass of the ceramic solid electrolyte particles accounts for 60% to 90% of the total mass of the composite solid electrolyte membrane with high ceramic content.

2. The preparation method according to claim 1, characterized in that, The particle size Dv50 of the ceramic solid electrolyte particles is 50nm to 5μm; The ceramic solid electrolyte particles include: garnet-type oxide solid electrolyte Li7Al3B12O 12 Perovskite oxide solid electrolyte Li 3x A2 2 / 3-x B2O3, NASICON-type oxide solid electrolyte Li 1+y A3 y B3 2-y (PO4)3, fluoride oxide solid electrolyte Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Fluoride oxide solid electrolyte Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Fluoride oxide solid electrolyte Li₂VO₂F, fluoride oxide solid electrolyte Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Fluoride oxide solid electrolyte Li m La n M1 a M2 b M3 c One or more of O6F; wherein, 0.01≤x≤0.5, 0.01≤y≤0.5, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3, 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2; A1 is one or more of La, Ca, Sr, Ba, K; B1 is one or more of Zr, Ta, Nb, Hf; A2 is one or more of La, Al, Mg, Fe, Ta; B2 is one or more of Ti, Nb, Sr, Pr; A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, La; B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, Hf; M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn; M2 is one or more of Nb, Sb, Bi, V, Ta; M3 is one or more of W, Cr, Mo, Mn; The silane coupling agent comprises one or more of the following: γ-aminopropyltriethoxysilane (KH-550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and γ-(methacryloyloxy)propyltrimethoxysilane (KH-570); the mass ratio of the silane coupling agent to the ceramic solid electrolyte particles is 0.5:100 to 5:

100. The solvent includes ethanol; the solid content of the mixed solution is 10wt% to 40wt%. The ball milling process is performed at a speed of 300 rpm to 500 rpm for 1 hour to 8 hours. The vacuum drying temperature is 50℃~80℃, and the vacuum drying time is 1 hour~8 hours.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the crosslinking agent, the organic monomer, the plasticizer, and the lithium salt is [4-6]:[2-3]:[5-8]:[2-3]; The crosslinking agent includes: polyethylene glycol diacrylate-200 (PEGDA-200); The organic monomers include one or more of the following: butyl acrylate (BA), triethylene glycol dimethacrylate (TEGDMA), ethylene ethylene carbonate (VEC), or trimethylolpropane triacrylate (TMPTA); The plasticizer includes one or more of the following: succinic anhydride (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC); The lithium salt includes one or more of the following: lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium dioxolane borate (LiBOB); The mass ratio of the ultraviolet photoinitiator to the thermal initiator is 1:9 to 9:1; The ultraviolet photoinitiator includes: 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide (TPO); The thermal initiator includes: azobisisobutyronitrile (AIBN); The total mass ratio of the ultraviolet photoinitiator and the thermal initiator to the mass ratio of the in-situ polymerization solution is 0.5:100 to 5:

100.

4. The preparation method according to claim 1, characterized in that, The ball milling speed is 300 rpm to 500 rpm, and the ball milling time is 1 hour to 8 hours.

5. The preparation method according to claim 1, characterized in that, The coating thickness is 5μm to 20μm; The wavelength of the ultraviolet light is 280nm to 400nm, and the irradiation time is 10min to 60min; The hot pressing temperature is 50℃~80℃, the pressure is 0.5MPa~3MPa, and the time is 10min~60min.

6. The preparation method according to claim 1, characterized in that, The positive electrode includes any one of the following: a positive electrode containing lithium cobalt oxide, a positive electrode containing ternary materials, a positive electrode containing lithium manganese oxide, and a positive electrode containing lithium iron phosphate. The negative electrode sheet includes any one of the following: lithium metal sheet, negative electrode sheet containing silicon-carbon negative electrode material, negative electrode sheet containing graphite, negative electrode sheet containing graphene, and negative electrode sheet containing transition metal.

7. A composite solid electrolyte membrane with high ceramic content prepared by the preparation method according to claims 1-6, characterized in that, The composite solid electrolyte membrane comprises: a polymer with a three-dimensional network structure polymerized in situ, and lithium salt and ceramic solid electrolyte particles activated by a silane coupling agent dispersed in the polymer. The polymer is formed by in-situ prepolymerization of organic monomers, crosslinking agents and plasticizers on the surface of a composite solid electrolyte membrane precursor initiated by an ultraviolet photoinitiator, followed by in-situ polymerization of the remaining organic monomers, crosslinking agents and plasticizers initiated by a thermal initiator during hot pressing. The ceramic solid electrolyte particles, which have been activated by silane coupling agent, are covalently bonded to the polymer. In the composite solid electrolyte membrane with high ceramic content, the mass of the ceramic solid electrolyte particles accounts for 60% to 90% of the total mass of the composite solid electrolyte membrane with high ceramic content.

8. The composite solid electrolyte membrane according to claim 7, characterized in that, The ultraviolet photoinitiator includes: 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide (TPO); The organic monomers include one or more of the following: butyl acrylate (BA), triethylene glycol dimethacrylate (TEGDMA), ethylene ethylene carbonate (VEC), or trimethylolpropane triacrylate (TMPTA); The crosslinking agent includes: polyethylene glycol diacrylate-200 (PEGDA-200); The plasticizer includes one or more of the following: succinic anhydride (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC); The thermal initiator includes azobisisobutyronitrile (AIBN); the lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium dioxolaneborate (LiBOB); the lithium salt accounts for 1% to 20% of the mass of the composite solid electrolyte membrane.

9. The composite solid electrolyte membrane according to claim 7, characterized in that, The particle size Dv50 of the ceramic solid electrolyte particles is 50nm to 5μm; The ceramic solid electrolyte particles include: garnet-type oxide solid electrolyte Li7Al3B12O 12 Perovskite oxide solid electrolyte Li 3x A2 2 / 3-x B2O3, NASICON-type oxide solid electrolyte Li 1+y A3 y B3 2-y (PO4)3, fluoride oxide solid electrolyte Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Fluoride oxide solid electrolyte Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Fluoride oxide solid electrolyte Li₂VO₂F, fluoride oxide solid electrolyte Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Fluoride oxide solid electrolyte Li m La n M1 a M2 b M3 c One or more of O6F; wherein, 0.01≤x≤0.5, 0.01≤y≤0.5, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3, 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2; A1 is one or more of La, Ca, Sr, Ba, K; B1 is one or more of Zr, Ta, Nb, Hf; A2 is one or more of La, Al, Mg, Fe, Ta; B2 is one or more of Ti, Nb, Sr, Pr; A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, La; B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, Hf; M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn; M2 is one or more of Nb, Sb, Bi, V, Ta; M3 is one or more of W, Cr, Mo, Mn; The silane coupling agent includes one or more of the following: γ-aminopropyltriethoxysilane (KH-550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and γ-(methacryloyloxy)propyltrimethoxysilane (KH-570).

10. A solid-state battery, characterized in that, The solid-state battery includes a composite solid-state electrolyte membrane with high ceramic content obtained by the preparation method according to any one of claims 1-6, or includes a composite solid-state electrolyte membrane with high ceramic content according to any one of claims 7-9.

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