Composite solid electrolyte membrane and preparation method and application thereof

Abstract

The application discloses a composite solid electrolyte film and a preparation method and application thereof, and the electrolyte film comprises: a positive electrode side high ion conductive layer containing a first polymer matrix, a lithium salt and inorganic fast ion conductor fillers; a gradient transition layer containing a second polymer matrix, the lithium salt, the inorganic fast ion conductor fillers and ceramic reinforcing fillers; a ceramic reinforcing layer containing the first polymer matrix, the lithium salt and the ceramic reinforcing fillers; and a negative electrode side self-repairing layer containing the second polymer matrix and the lithium salt; wherein the positive electrode side high ion conductive layer, the gradient transition layer, the ceramic reinforcing layer and the negative electrode side self-repairing layer are sequentially stacked along the thickness direction of the electrolyte film. Compared with the prior art, the application solves the problems of insufficient ion conductivity of the solid electrolyte film, unstable interface contact, limited mechanical strength and accumulated interface damage in the cycle process through the synergistic design of positive and negative electrode function zoning, gradient transition and ceramic reinforcement, and is suitable for high-safety and high-energy-density solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, and particularly relates to a composite solid-state electrolyte membrane, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, drones, energy storage power stations, and high-safety battery systems, traditional liquid lithium-ion batteries are facing increasingly higher requirements in terms of energy density, safety, and long-term reliability. While liquid electrolyte systems possess high ionic conductivity and good electrode wettability, they also suffer from flammability, leakage, insufficient thermal stability, and a tendency to induce side reactions and lithium dendrite growth in lithium metal anode systems. Therefore, replacing traditional liquid electrolytes with solid-state electrolytes is considered a crucial technological approach to improving the safety, energy density, and service stability of lithium batteries.

[0003] Solid-state electrolyte membranes (SEMs), as a key component of solid-state batteries, are typically located between the positive and negative electrodes, serving functions such as conducting lithium ions, isolating electrons, preventing direct contact between the positive and negative electrodes, and suppressing lithium dendrite penetration. An ideal SEM should simultaneously possess high lithium-ion conductivity, good electrochemical stability, excellent mechanical strength, low interfacial impedance, and good solid-solid contact capability with both the positive and negative electrodes. However, in practical applications, these properties often exhibit interdependent relationships, making it difficult for SEMs to simultaneously meet the requirements of high ion transport, high mechanical stability, and high interfacial compatibility.

[0004] Currently, solid-state electrolyte membranes mainly include inorganic ceramic solid-state electrolyte membranes, polymer solid-state electrolyte membranes, and organic-inorganic composite solid-state electrolyte membranes. Inorganic ceramic solid-state electrolytes, such as oxide-type, sulfide-type, phosphate-type, and halide-type solid-state electrolytes, typically exhibit high lithium-ion conductivity, a wide electrochemical window, and good thermal stability. Among them, LLZO, LATP, LAGP, and LPSC inorganic solid-state electrolytes have been extensively studied. However, inorganic ceramic electrolytes generally suffer from problems such as high brittleness, difficulty in processing into films, poor rigidity at the electrode interface, and high interfacial impedance. During battery cycling, changes in electrode volume, localized stress concentration, or external pressure fluctuations can easily lead to cracks, interfacial debonding, or localized contact failure in the ceramic electrolyte membrane, thus affecting the long-term cycle stability of the battery.

[0005] Polymer solid electrolyte membranes typically use polymers such as polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polycarbonate polymers, and polycaprolactone as the matrix, and incorporate lithium salts to form lithium-ion transport channels. Compared with inorganic ceramic electrolytes, polymer solid electrolytes have advantages such as good flexibility, strong film-forming ability, simple processing technology, and good adhesion to the electrode interface, making them suitable for preparing large-area, thin, and flexible solid electrolyte membranes. However, traditional polymer solid electrolytes are usually limited by the mobility and crystallinity of polymer chains at room temperature, resulting in relatively low ionic conductivity. Simultaneously, their mechanical strength and resistance to lithium dendrite penetration are limited, making them prone to problems such as local deformation, increased interfacial porosity, and intensified electrochemical polarization under high current density or long-term cycling conditions.

[0006] To balance the flexibility of polymer electrolytes with the high ion conductivity and mechanical reinforcement of inorganic electrolytes, organic-inorganic composite solid electrolyte membranes have been proposed. For example, introducing inorganic fillers such as LLZO, LATP, LAGP, Al2O3, SiO2, and TiO2 into the polymer matrix can, to some extent, reduce polymer crystallinity, promote lithium salt dissociation, improve mechanical strength, and enhance the ion transport capacity of the solid electrolyte membrane. Furthermore, other approaches utilize porous ceramic frameworks, continuous inorganic ion conductor networks, surface-modified fillers, or in-situ polymerized electrolyte membranes to improve the overall performance of composite electrolyte membranes. These methods can, to some extent, address the problems inherent in traditional single polymer electrolytes or single ceramic electrolytes.

[0007] However, existing composite solid electrolyte membranes still have significant shortcomings. First, most composite electrolyte membranes employ a homogeneous composition design, meaning that inorganic fillers, lithium salts, and polymers are uniformly distributed throughout the membrane, making it difficult to functionally partition them according to the different interface requirements of the positive and negative electrode sides. The positive electrode side typically requires high ion transport capacity and good electrochemical stability to reduce the positive electrode / electrolyte interface impedance and improve the utilization rate of active materials; while the negative electrode side, especially the lithium metal negative electrode side, requires higher mechanical strength, uniform ion flux distribution, and stable interface contact to suppress lithium dendrite growth and interface side reactions. Traditional homogeneous electrolyte membranes cannot simultaneously meet these two types of interface requirements. Second, existing solid electrolyte membranes generally face the problem of unstable solid-solid interface contact during cycling. Unlike liquid electrolytes, which can continuously wet the electrode surface, solid electrolytes mainly rely on mechanical pressing or local adhesion to form the contact interface with the electrode. During battery charging and discharging, the positive and negative electrode materials undergo volume changes and stress fluctuations, making it easy for micropores, local debonding, or interface cracks to form between the solid electrolyte membrane and the electrode. If the interface contact is insufficient, the resistance to lithium-ion transport across the interface will increase significantly, and the local current density distribution will become uneven, which will lead to increased battery polarization, accelerated capacity decay, and even induce preferential growth of lithium dendrites.

[0008] Some technologies have been developed to improve the stability of the positive and negative electrode interfaces through surface coatings, interfacial buffer layers, or artificial solid electrolyte interfacial layers. However, these approaches typically act primarily on the electrode or electrolyte surface, making it difficult to create a continuous ion transport gradient and mechanical property gradient along the electrolyte membrane thickness. Other technologies introduce self-healing polymers or dynamic bond structures to improve interfacial damage generated during cycling. However, these typically focus on repairing single interfacial contacts, and the synergistic regulation of high ion transport on the positive electrode side, dendrite suppression on the negative electrode side, and overall membrane structural stability remains insufficient.

[0009] Therefore, existing solid electrolyte membrane technologies still lack a structured design that can simultaneously achieve rapid ion transport on the positive electrode side, mechanical enhancement on the negative electrode side, stable interface contact, and self-repair of cyclic damage. Summary of the Invention

[0010] The purpose of this invention is to provide a composite solid electrolyte membrane, its preparation method, and its application, which can improve the problems of insufficient solid-solid contact of electrolyte / electrode, discontinuous ion transport, lithium dendrite penetration, and long-term cycle interface failure in solid batteries, thereby improving the safety, cycle stability, and rate performance of the battery.

[0011] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a composite solid electrolyte membrane, comprising: A positive electrode side high ion conductive layer, wherein the positive electrode side high ion conductive layer comprises a first polymer matrix, a lithium salt and an inorganic fast ion conductor filler; A gradient transition layer comprising a second polymer matrix, a lithium salt, an inorganic fast ion conductor filler, and a ceramic reinforcing filler; A ceramic reinforcement layer comprising a first polymer matrix, a lithium salt, and a ceramic reinforcement filler; A negative electrode side self-healing layer, wherein the negative electrode side self-healing layer comprises a second polymer matrix and a lithium salt; The positive electrode side high ion conductivity layer, the gradient transition layer, the ceramic reinforcement layer, and the negative electrode side self-healing layer are stacked sequentially along the thickness direction of the electrolyte membrane.

[0012] Preferably, the first polymer matrix is ​​selected from at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polycarbonate polymers, polycaprolactone, polymethyl methacrylate, polysiloxane, and polyurethane.

[0013] Preferably, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium iodide, lithium nitrate, and lithium fluoride.

[0014] Preferably, the inorganic fast ion conductor filler is selected from Li7La3Zr2O 12 Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li6PS5Cl, Li 10 GeP2S 12 At least one of Li3InCl6, Li3YCl6 and their doped and modified materials; The inorganic fast ion conductor filler in the high ion conductive layer on the positive electrode side has a mass fraction of 5% to 60%.

[0015] Preferably, the ceramic reinforcing filler is selected from at least one of LLZO, LATP, LAGP, Al2O3, SiO2, TiO2, ZrO2, BN, MgO, LiF, Li3N and their surface-modified products; The ceramic reinforcing filler in the ceramic reinforcing layer has a mass fraction of 10% to 80%.

[0016] Preferably, the second polymer matrix is ​​selected from at least one of low-melting-point polymers, dynamically reconfigurable polymers, ionically conductive polymers, and their composites; The low-melting-point polymer is selected from at least one of polyethylene glycol, low molecular weight polyethylene oxide, polycaprolactone and its copolymers; the dynamically reconfigurable polymer is selected from at least one of polymers containing hydrogen bonds, ionic bonds, borate ester bonds, disulfide bonds, imine bonds, metal coordination bonds, and host-guest interactions.

[0017] Preferably, the contents of the second polymer matrix, lithium salt, inorganic fast ion conductor filler, and ceramic reinforcing filler in the gradient transition layer vary in a continuous gradient, a step gradient, or a semi-continuous gradient along the film thickness direction.

[0018] Preferably, the structure of the composite solid electrolyte membrane is selected from at least one of the following: layered structure, continuous gradient structure, interlayer interpenetrating structure, and localized reinforcement structure.

[0019] Preferably, the thickness of the high ion conductivity layer on the positive electrode side is 1μm~100μm; the thickness of the gradient transition layer is 1μm~150μm; the thickness of the ceramic reinforcement layer is 1μm~100μm; the thickness of the self-healing layer on the negative electrode side is 1μm~50μm; and the total thickness of the composite solid electrolyte membrane is 10μm~300μm.

[0020] Secondly, the present invention provides a method for preparing a composite solid electrolyte membrane, comprising the following steps: (1) Preparation of high ion conductive layer slurry on the positive electrode side: The first polymer matrix, lithium salt and inorganic fast ion conductor filler are dispersed in an organic solvent to obtain a uniform high ion conductive layer slurry on the positive electrode side; (2) Preparation of gradient transition layer slurry: The second polymer matrix, lithium salt, inorganic fast ion conductor filler and ceramic reinforcing filler are mixed in a preset gradient ratio to obtain gradient transition layer slurry; (3) Preparation of ceramic reinforcement layer slurry: The first polymer matrix, lithium salt and ceramic reinforcement filler are mixed and dispersed to obtain ceramic reinforcement layer slurry; (4) Preparation of self-healing layer slurry on the negative electrode side: Mix low melting point polymer, dynamic reconfigurable polymer, lithium salt, plasticizer, crosslinking agent and ionic liquid to obtain self-healing layer slurry on the negative electrode side; (5) The slurry obtained in steps (1) to (4) is molded in sequence to form a film consisting of a high ion conductivity layer on the positive electrode side, a gradient transition layer, a ceramic reinforcement layer and a self-healing layer on the negative electrode side. (6) The membrane obtained in step (5) is dried and hot-pressed to make the layers tightly bonded, thus obtaining the composite solid electrolyte membrane.

[0021] Preferably, the organic solvent in step (1) is selected from at least one of acetonitrile, N-methylpyrrolidone, tetrahydrofuran, dimethylformamide, dimethylacetamide, ethanol, water, and mixed solvents thereof.

[0022] Preferably, the hot pressing temperature in step (6) is 40℃~150℃, the pressure is 0.1MPa~20MPa, and the hot pressing time is 1min~120min.

[0023] Thirdly, the present invention provides a solid-state battery, including a positive electrode, a negative electrode, and a composite solid electrolyte membrane disposed between the positive electrode and the negative electrode.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects: 1) The composite solid electrolyte membrane of this invention has clearly defined functional zones, capable of adapting to the different interface requirements of the positive and negative electrode sides. By setting a high ion conductivity layer near the positive electrode side, the positive electrode / electrolyte interface impedance can be reduced, improving lithium-ion transport efficiency and active material utilization. By setting a ceramic reinforcement layer and a self-healing layer near the negative electrode side, the mechanical stability, interface adhesion, and resistance to lithium dendrite penetration of the electrolyte membrane can be improved. Compared with traditional homogeneous solid electrolyte membranes, this invention avoids the problem that a single membrane structure cannot simultaneously achieve high ion conductivity and high mechanical strength.

[0025] 2) The gradient transition layer of this invention can reduce interfacial abrupt changes and mechanical mismatches between multifunctional layers. By adjusting the distribution of inorganic fast ion conductors, ceramic reinforcing fillers, lithium salts, and polymer components in the film thickness direction, continuous or hierarchically varied ion transport channels and mechanically reinforced structures can be formed, enabling synergistic optimization of lithium-ion transport capacity, film strength, and interfacial compatibility. Compared to simple laminated multilayer electrolyte membranes, this invention can reduce the risks of increased interlayer impedance, interlayer delamination, and local ion pathway interruption.

[0026] 3) The self-healing layer on the negative electrode side of this invention has the functions of repairing interface damage and restoring ion pathways. Under the action of heat, pressure, or cyclic stress, this self-healing layer can undergo chain segment migration, local softening, interface wetting, or dynamic bond recombination, thereby filling the micropores, microcracks, and local debonding areas generated at the lithium metal negative electrode interface, maintaining a stable solid-solid contact between the electrolyte membrane and the negative electrode. Compared with existing solutions that rely solely on initial bonding or a single interface coating, this invention can continuously alleviate interface contact failure and impedance growth problems during cycling.

[0027] 4) The synergistic effect of the inorganic fast ion conductor and ceramic reinforcing filler of this invention can enhance the mechanical strength and dimensional stability of the membrane while improving ion transport capability. The inorganic fast ion conductor on the positive electrode side helps to construct a fast lithium-ion migration channel and reduce battery polarization; the ceramic reinforcing filler on the negative electrode side helps to improve the membrane modulus, uniform lithium-ion flux, and suppress lithium dendrite penetration; by controlling the type, content, particle size, and distribution position of the filler, a balance can be achieved between ionic conductivity, flexibility, mechanical strength, and safety.

[0028] 5) The composite solid electrolyte membrane preparation method of the present invention has good process adjustability and applicability. The electrolyte membrane can be prepared by methods such as blade coating, casting, spraying, layer coating, transfer printing, hot pressing, in-situ polymerization, or multilayer co-extrusion. The composition, thickness, and gradient distribution of each functional layer can be adjusted according to different battery systems. Moreover, this method is applicable to lithium metal batteries, all-solid-state lithium-ion batteries, all-solid-state lithium-sulfur batteries, and other solid-state electrochemical energy storage devices, which is beneficial to improving the cycle stability, rate performance, and safety reliability of solid-state batteries. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the composite solid electrolyte membrane of the present invention; Figure 2 This is a schematic diagram of the solid-state battery structure of the present invention.

[0031] In the figure: 1. High ion conductivity layer on the positive electrode side; 2. Gradient transition layer; 3. Ceramic reinforcement layer; 4. Self-healing layer on the negative electrode side; 5. Positive electrode; 6. Negative electrode. Detailed Implementation

[0032] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0033] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0034] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0035] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0036] According to a first aspect of the invention, such as Figure 1 As shown, the present invention provides a composite solid electrolyte membrane, comprising: The positive electrode side high ion conductive layer 1 includes a first polymer matrix, a lithium salt and an inorganic fast ion conductor filler. Gradient transition layer 2 comprises a first polymer matrix, lithium salt, inorganic fast ion conductor filler and ceramic reinforcing filler; Ceramic reinforcement layer 3, comprising a first polymer matrix, lithium salt and ceramic reinforcement filler; The negative electrode side self-healing layer 4 includes a second polymer matrix and a lithium salt. Among them, the high ion conductivity layer 1, gradient transition layer 2, ceramic reinforcement layer 3 on the positive electrode side and the self-healing layer 4 on the negative electrode side are stacked sequentially along the thickness direction of the electrolyte membrane.

[0037] Among them, the high ion conductivity layer 1 on the positive electrode side is used to reduce the impedance of the positive electrode / electrolyte interface and promote the rapid migration of lithium ions; the gradient transition layer 2 is used to adjust the continuous change of inorganic filler content, lithium salt concentration or polymer composition in the film thickness direction and reduce the interface abruptness between adjacent functional layers; the ceramic reinforcement layer 3 is used to improve the mechanical strength, dimensional stability and resistance to lithium dendrite penetration of the film; and the self-healing layer 4 on the negative electrode side is used to adaptively fill and repair the micropores, microcracks and local debonding areas formed at the negative electrode interface during battery assembly, heating, pressurization or cycling.

[0038] In some embodiments of the present invention, the first polymer matrix is ​​selected from at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polycarbonate polymers, polycaprolactone, polymethyl methacrylate, polysiloxane, and polyurethane.

[0039] The positive electrode side high ion conductivity layer uses polyethylene oxide, polycarbonate polymers or polyvinylidene fluoride-hexafluoropropylene copolymer as the matrix to improve ion transport capacity and interface wettability; the negative electrode side self-healing layer uses polyethylene oxide, polyethylene glycol, polycaprolactone, dynamically crosslinked polyurethane or polymers containing reversible hydrogen bonds / ionic bonds / boronic acid ester bonds as the matrix to achieve flexible interface bonding and cyclic damage repair.

[0040] In some embodiments of the present invention, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium iodide, lithium nitrate, and lithium fluoride.

[0041] The molar ratio of lithium salt to coordinateable functional groups in the polymer matrix can be adjusted according to the ionic conductivity and the mechanical properties of the membrane. In this invention, the lithium salt content in the high ionic conductivity layer on the positive electrode side is higher than the lithium salt content in the self-healing layer on the negative electrode side, thereby forming a lithium-ion transport gradient along the film thickness direction, promoting rapid lithium-ion transport on the positive electrode side and reducing polarization.

[0042] In some embodiments of the present invention, the inorganic fast ion conductor filler is selected from Li7La3Zr2O. 12 Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5(PO4)3, Li6PS5Cl, Li 10 GeP2S 12 At least one of Li3InCl6, Li3YCl6 and their doped and modified materials; The mass fraction of the inorganic fast ion conductor filler in the high ion conductivity layer on the positive electrode side is 5% to 60%. For example, the mass fraction of the inorganic fast ion conductor filler in the high ion conductivity layer on the positive electrode side can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc. Preferably, it is 10% to 40%. The morphology of the inorganic fast ion conductor filler is selected from at least one of nanoparticles, nanowires, nanosheets, porous frameworks, and continuous network structures. The positive electrode side high ion conductivity layer of this invention can also incorporate LATP, LAGP, LLZO, or halide solid electrolyte particles to improve lithium-ion transport capability.

[0043] In some embodiments of the present invention, the ceramic reinforcing filler is selected from at least one of LLZO, LATP, LAGP, Al2O3, SiO2, TiO2, ZrO2, BN, MgO, LiF, Li3N and their surface-modified products; The mass fraction of ceramic reinforcing filler in the ceramic reinforcing layer is 10% to 80%. For example, the mass fraction of ceramic reinforcing filler in the ceramic reinforcing layer can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc., preferably 20% to 60%.

[0044] Among them, ceramic reinforcing fillers are used to improve the mechanical modulus and dimensional stability of composite solid electrolyte membranes and to uniformly regulate the lithium-ion flux on the lithium metal anode side; and by adjusting the type, particle size, morphology and content of ceramic reinforcing fillers, a balance can be achieved between the mechanical strength, flexibility and dendrite resistance of solid electrolyte membranes.

[0045] In some embodiments of the present invention, the second polymer matrix is ​​selected from at least one of low-melting-point polymers, dynamically reconfigurable polymers, ion-conducting polymers, and their composites; The low-melting-point polymer is selected from at least one of polyethylene glycol, low molecular weight polyethylene oxide, polycaprolactone and its copolymers; the dynamically reconfigurable polymer is selected from at least one of polymers containing hydrogen bonds, ionic bonds, borate ester bonds, disulfide bonds, imine bonds, metal coordination bonds, and host-guest interactions.

[0046] The second polymer matrix in the self-healing layer on the negative electrode side can undergo chain segment migration, local softening, interface wetting, or dynamic bond recombination within a temperature range of 40~90℃, thereby filling the micropores and microcracks formed at the lithium metal negative electrode interface and restoring the continuity of the lithium-ion transport channel. Its thickness is set at 1~50μm to characterize and ensure the interface repair capability and avoid excessive increase in battery internal resistance.

[0047] In some embodiments of the present invention, the contents of the second polymer matrix, lithium salt, inorganic fast ion conductor filler, and ceramic reinforcing filler in the gradient transition layer vary in a continuous gradient, a step gradient, or a semi-continuous gradient along the film thickness direction.

[0048] In this process, from the positive electrode side to the negative electrode side, the content of inorganic fast ion conductor filler and lithium salt component gradually decreases, while the content of ceramic reinforcing filler and the second polymer matrix gradually increases. This gradient transition layer can reduce the interfacial impedance and mechanical mismatch between the high ion conductivity layer on the positive electrode side and the mechanical reinforcement / self-healing layer on the negative electrode side, thereby reducing the risk of interlayer delamination in the multilayer composite film during bending, hot pressing, and cycling.

[0049] In some embodiments of the present invention, the structure of the composite solid electrolyte membrane is selected from at least one of the following: layered structure, continuous gradient structure, interlayer interpenetrating structure, and local reinforcement structure.

[0050] The structure of composite solid electrolyte membranes serves different purposes for different solid-state batteries. For high-rate solid-state batteries, the content of inorganic fast ion conductors and lithium salts in the high ion conductivity layer on the positive electrode side can be increased to reduce polarization on the positive electrode side. For lithium metal solid-state batteries, the content of ceramic reinforcing filler and the second polymer matrix on the negative electrode side can be increased to enhance resistance to dendrite penetration and interface repair capabilities. For flexible solid-state batteries, the thickness of the ceramic reinforcing layer can be reduced and the proportion of flexible polymers can be increased to improve the bending stability of the membrane.

[0051] In some embodiments of the present invention, the thickness of the high ion conductivity layer on the positive electrode side is 1 μm to 100 μm; the thickness of the gradient transition layer is 1 μm to 150 μm; the thickness of the ceramic reinforcement layer is 1 μm to 100 μm; the thickness of the self-healing layer on the negative electrode side is 1 μm to 50 μm; and the total thickness of the composite solid electrolyte membrane is 10 μm to 300 μm.

[0052] By controlling the thickness and component ratio of each functional layer, synergistic optimization of ionic conductivity, mechanical strength, interface stability, and self-healing performance can be achieved.

[0053] According to a second aspect of the present invention, the present invention provides a method for preparing a composite solid electrolyte membrane, comprising the following steps: (1) Preparation of high ion conductive layer slurry on the positive electrode side: The first polymer matrix, lithium salt and inorganic fast ion conductor filler are dispersed in an organic solvent to obtain a uniform high ion conductive layer slurry on the positive electrode side; (2) Preparation of gradient transition layer slurry: The second polymer matrix, lithium salt, inorganic fast ion conductor filler and ceramic reinforcing filler are mixed in a preset gradient ratio to obtain gradient transition layer slurry; (3) Preparation of ceramic reinforcement layer slurry: The first polymer matrix, lithium salt and ceramic reinforcement filler are mixed and dispersed to obtain ceramic reinforcement layer slurry; (4) Preparation of self-healing layer slurry on the negative electrode side: Mix low melting point polymer, dynamic reconfigurable polymer, lithium salt, plasticizer, crosslinking agent and ionic liquid to obtain self-healing layer slurry on the negative electrode side; (5) The slurry obtained in steps (1) to (4) is molded in sequence to form a film consisting of a high ion conductivity layer on the positive electrode side, a gradient transition layer, a ceramic reinforcement layer and a self-healing layer on the negative electrode side. (6) The membrane obtained in step (5) is dried and hot-pressed to make the layers tightly bonded to obtain a composite solid electrolyte membrane.

[0054] In step (1), the slurry is used to form a high ion-conducting layer near the positive electrode side to improve the lithium-ion transport capability at the positive electrode / electrolyte interface; in step (2), by adjusting the ratio of inorganic fast ion conductor filler, ceramic reinforcing filler and lithium salt in each slurry, the ion transport capability and mechanical reinforcement capability in the film thickness direction are continuously or hierarchically varied; in step (3), the ceramic reinforcing filler can also be surface modified, and the surface modification treatment is selected from at least one of silane coupling, polymer coating, lithium salt modification and ion conductor coating to improve the dispersion and interfacial compatibility of the ceramic filler in the polymer matrix; in step (4), the self-healing layer slurry is subjected to heat, pressure or cyclic stress after film formation. It has the ability to migrate chains, soften locally, wet interfaces or reorganize dynamic bonds, and is used to improve the interface contact of lithium metal anode and repair interface defects generated by cycling; in step (5), the molding is selected from at least one of the following methods: scraping, casting, spraying, spin coating, dip coating, electrospinning, layer coating, transfer printing, hot pressing composite, in-situ polymerization, multilayer co-extrusion. The functional layers can be composited in a semi-dry state to form an interpenetrating interface structure and reduce the risk of interlayer peeling; in step (6), the composite solid electrolyte membrane can be further processed. The processing method is selected from at least one of the following methods: crosslinking, ultraviolet curing, thermosetting, in-situ polymerization, surface modification treatment, to improve the stability of the membrane structure and the interface tolerance.

[0055] In some embodiments of the present invention, the organic solvent in step (1) is selected from at least one of acetonitrile, N-methylpyrrolidone, tetrahydrofuran, dimethylformamide, dimethylacetamide, ethanol, water, and mixed solvents thereof.

[0056] In some embodiments of the present invention, the hot pressing temperature in step (6) is 40°C to 150°C, the pressure is 0.1 MPa to 20 MPa, and the hot pressing time is 1 min to 120 min.

[0057] According to a third aspect of the invention, such as Figure 2 As shown, the present invention provides a solid-state battery, including a positive electrode 5, a negative electrode 6, and a composite solid electrolyte membrane disposed between the positive electrode 5 and the negative electrode 6.

[0058] Among them, the composite solid electrolyte membrane has an asymmetric functional structure in the thickness direction.

[0059] The high-ion conductivity layer near the positive electrode contains a first polymer matrix, lithium salt, and inorganic fast-ion conductor filler, providing a low-impedance migration channel for lithium ions. During solid-state battery charging and discharging, continuous lithium-ion exchange is required between the positive electrode active material and the solid electrolyte. Traditional homogeneous polymer electrolyte membranes are prone to increased battery polarization on the positive electrode side due to insufficient ionic conductivity, inadequate solid-solid contact, and high local interface impedance. This invention, by setting a high-ion conductivity layer on the positive electrode side, enables the synergistic effect of lithium salt dissociation, polymer chain migration, and inorganic fast-ion conductor transport channels, thereby reducing the lithium-ion migration resistance at the positive electrode / electrolyte interface and improving the utilization rate and rate performance of the positive electrode active material.

[0060] A gradient transition layer is used to mitigate abrupt changes in composition and mechanical properties between different functional layers. In traditional multilayer solid electrolyte membranes, direct lamination between different layers can easily lead to problems such as increased interlayer impedance, interruption of ion transport paths, or debonding during cycling. This invention addresses this by ensuring that the inorganic fast ion conductor filler, ceramic reinforcing filler, lithium salt, or polymer components vary continuously or in stages along the membrane thickness, creating a transitional connection between the high ion conductivity region on the positive electrode side and the mechanically reinforced / self-healing region on the negative electrode side. This gradient structure reduces ion transport discontinuities at multilayer interfaces, while also minimizing modulus differences and stress concentration between different functional layers, thereby improving the overall structural stability of the composite solid electrolyte membrane.

[0061] The ceramic reinforcement layer is mainly used to improve the mechanical strength, dimensional stability, and resistance to lithium dendrite penetration of the composite solid electrolyte membrane. During cycling, the lithium metal anode undergoes repeated deposition and stripping. If the ion flux distribution on the anode side is uneven or the local mechanical strength of the membrane is insufficient, dendritic or needle-like lithium deposits can easily form, further piercing the electrolyte membrane and causing a short circuit. This invention introduces ceramic reinforcement filler near the anode side, which can increase the local modulus of the membrane, uniformly distribute lithium ion flux, and physically block the growth and penetration of lithium dendrites. Simultaneously, some ceramic fillers can also improve the polymer chain arrangement and lithium salt dissociation environment, enabling simultaneous mechanical reinforcement and ion transport regulation.

[0062] The self-healing layer on the negative electrode side is a key functional layer in this invention for improving the long-term cycling interface stability. Solid-state batteries differ from liquid electrolyte batteries; the solid electrolyte membrane and electrode primarily rely on mechanical pressing to form a solid-solid contact. During charge-discharge cycles, micropores, microcracks, or localized debonding areas can form on the negative electrode surface due to uneven lithium deposition / stripping, volume changes, and localized stress fluctuations. If these interface defects are not filled and repaired in time, lithium-ion transport will be locally impeded, interface impedance will increase, and this will further induce uneven current density distribution and lithium dendrite growth. This invention incorporates a low-melting-point polymer or dynamically reconfigurable polymer component on the negative electrode side, which undergoes chain segment migration, localized softening, interface wetting, or dynamic bond recombination under certain temperature, pressure, or cyclic stress conditions. This adaptively fills the pores and cracks at the negative electrode interface, restoring the continuous contact interface between the electrolyte membrane and the negative electrode.

[0063] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0064] Example 1

[0065] Preparation of composite solid electrolyte membranes (1) Preparation of high ion conductive layer slurry on the positive electrode side: Polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide and LATP nanoparticles were added to acetonitrile, wherein the amount of polyethylene oxide added was 2.00 g, the amount of lithium bis(trifluoromethanesulfonyl)imide added was 1.00 g, the amount of LATP nanoparticles added was 1.50 g, and the amount of acetonitrile was 40 mL per 1 g of solid component. After stirring for 24 h and ultrasonically dispersing for 60 min, the high ion conductive layer slurry on the positive electrode side was obtained.

[0066] (2) Preparation of gradient transition layer slurry: polyethylene oxide, lithium bis(trifluoromethanesulfonylimide), LATP nanoparticles and LLZO nanoparticles are added to acetonitrile, and the mass ratio of LATP to LLZO is controlled to be 1:2, and the total mass fraction of LATP and LLZO is 50wt%; after stirring and ultrasonic dispersion, gradient transition layer slurry is obtained.

[0067] (3) Preparation of ceramic reinforcement layer slurry: Polyethylene oxide, lithium bis(trifluoromethanesulfonylimide), LLZO nanoparticles and Al2O3 nanoparticles are added to acetonitrile, wherein the total mass fraction of LLZO and Al2O3 is 60wt% and the mass ratio of LLZO to Al2O3 is 1:1; after stirring, ball milling or high-speed shear dispersion, ceramic reinforcement layer slurry is obtained.

[0068] (4) Preparation of the self-healing layer slurry on the negative electrode side: Polyethylene oxide, polyethylene glycol, and lithium bis(trifluoromethanesulfonyl)imide were added to acetonitrile, wherein the mass ratio of polyethylene oxide to polyethylene glycol was 1:2, and the mass ratio of lithium salt to the total amount of polyethylene oxide and polyethylene glycol was 1:8; after stirring for 24 h, the self-healing layer slurry on the negative electrode side was obtained. The number average molecular weight of polyethylene glycol was 4000.

[0069] (5) The above slurry is coated onto the surface of polytetrafluoroethylene substrate by scraping in sequence to form a film consisting of a high ion conductivity layer on the positive electrode side, a gradient transition layer, a ceramic reinforcement layer and a self-healing layer on the negative electrode side. After each layer is coated, it is vacuum dried at 70 °C for 3 h to remove residual solvent.

[0070] (6) After the multilayer coating is completed, the membrane is peeled off from the substrate and hot-pressed at 100 °C and 10 MPa for 60 min to obtain the composite solid electrolyte membrane.

[0071] The thickness of the high-ion conductive layer on the positive electrode side is 5-50 μm, the thickness of the gradient transition layer is 5-80 μm, the thickness of the ceramic reinforcement layer is 5-60 μm, the thickness of the self-healing layer on the negative electrode side is 3-30 μm, and the total thickness of the resulting composite solid electrolyte membrane is 30-150 μm.

[0072] Example 2

[0073] The difference from Example 1 is that in step (1), polyethylene oxide is replaced with polyvinylidene fluoride-hexafluoropropylene copolymer, and the remaining steps are the same as in Example 1.

[0074] Example 3

[0075] Unlike Example 1, in step (2), the mass ratio of LATP to LLZO is 1:0.5, and the total mass fraction of LATP and LLZO is 10wt%. The remaining steps are the same as in Example 1.

[0076] Example 4

[0077] Unlike Example 1, in step (3), the total mass fraction of LLZO and Al2O3 is 75wt%, the mass ratio of LLZO to Al2O3 is 1:1.5, the thickness of the self-healing layer on the negative electrode side is 5-20μm, and the remaining steps are the same as in Example 1.

[0078] Example 5

[0079] The difference from Example 1 is that in step (4), polyethylene glycol is replaced with polycaprolactone, and the rest of the steps are the same as in Example 1.

[0080] Example 6

[0081] The difference from Example 1 is that lithium bis(trifluoromethanesulfonylimide) is replaced with lithium difluorooxalateborate, while the rest of the steps are the same as in Example 1.

[0082] Comparative Example 1 The difference from Example 1 is that step (2) is omitted, while the remaining steps are the same as in Example 1.

[0083] Comparative Example 2 Unlike Example 1, LLZO nanoparticles and Al2O3 nanoparticles are not added in step (3), while the remaining steps are the same as in Example 1.

[0084] Comparative Example 3 Unlike Example 1, step (4) is omitted; the remaining steps are the same as in Example 1.

[0085] Comparative Example 4 Polyethylene oxide, lithium bis(trifluoromethanesulfonylimide), LATP, LLZO and Al2O3 were mixed and dispersed in acetonitrile in a mass ratio of 2:1:1.5:3:3. After stirring, ultrasonic dispersion, coating and drying, a composite solid electrolyte membrane was obtained.

[0086] The composite solid electrolyte membranes obtained from the above embodiments and comparative examples were subjected to the following tests, and the test results are shown in Table 1.

[0087] 1) Ionic conductivity test: The composite solid electrolyte membrane is cut into circular pieces with a diameter of 10-16 mm and sandwiched between stainless steel blocking electrodes to assemble a stainless steel / electrolyte membrane / stainless steel symmetrical cell; AC impedance test is performed using an electrochemical workstation with a test frequency range of 1MHz~0.1Hz, a perturbation voltage of 5-10mV, and a test temperature of 25-80℃, and the ionic conductivity is calculated based on the tested membrane thickness, effective contact area, and impedance value.

[0088] 2) Mechanical property testing: The composite solid electrolyte membrane is cut into strip samples and its tensile strength, elongation at break, puncture strength or compressive modulus is tested.

[0089] 3) Self-healing performance test: Micro-scratches or local micro-cracks are artificially introduced into the surface of the composite solid electrolyte membrane or the interface of the negative electrode. Then, the membrane is treated at 50-80℃ and 0.5-5MPa pressure for 10-60 min, and the impedance change of the membrane before and after repair is tested.

[0090] 4) Lithium-Li Symmetric Battery Cycling Test: A composite solid electrolyte membrane was sandwiched between two lithium metal sheets to assemble a Li / electrolyte membrane / Li symmetric battery. Constant current lithium deposition / stripping tests were performed at 40-80℃ with a current density of 0.2 mA·cm⁻¹. -2 The single-step deposition / stripping time is 1 hour.

[0091] Table 1

[0092] From Table 1, we can obtain: The composite solid electrolyte membranes of Examples 1-6 all exhibited good ionic conductivity in the range of 25-80℃, and the ionic conductivity increased significantly with increasing temperature, indicating that polymer chain segment movement, lithium salt dissociation and inorganic fast ion conductor transport channels can synergistically promote lithium ion migration. Among them, Example 1 showed the highest overall ionic conductivity, indicating that the high ionic conductivity layer and gradient transition layer on the positive electrode side are conducive to the formation of a continuous lithium-ion transport path. In Example 2, after replacing polyethylene oxide with polyvinylidene fluoride-hexafluoropropylene copolymer as the polymer matrix, the ionic conductivity decreased slightly, but remained at a high level, indicating that polyvinylidene fluoride-hexafluoropropylene copolymer can balance membrane stability and lithium-ion transport capability. In Example 3, after appropriately reducing the content of LATP / LLZO inorganic fast ion conductor, the ionic conductivity decreased, but a relatively continuous ion transport network could still be formed, meeting the ion transport requirements of solid-state batteries. In Example 4, due to the high content of ceramic reinforcing filler, the ionic conductivity decreased slightly, but remained at a high level. In Example 5, the introduction of self-healing components did not significantly hinder ion transport. In Example 6, after replacing bis(trifluoromethanesulfonyl)imide with lithium difluorooxalate borate as the lithium salt, the ionic conductivity was similar to that of Example 2, indicating that lithium difluorooxalate borate also has good lithium-ion dissociation capability and transport performance, and is also conducive to improving the interface stability between the electrolyte membrane and the lithium metal anode. In contrast, the ionic conductivity of Comparative Examples 1-4 is generally low, especially that of Comparative Example 4, which has a homogeneous structure and lacks a clear gradient transport channel, resulting in greater resistance to lithium-ion migration. These results demonstrate that the composite solid electrolyte membrane of the present invention can improve lithium-ion transport capacity while maintaining functional partitioning and membrane stability.

[0093] The composite solid electrolyte membranes of Examples 1-6 all exhibited good mechanical strength and dimensional stability. In Example 4, due to the high content of ceramic reinforcing filler, the tensile strength, puncture strength, and compressive modulus reached 11.4 MPa, 2.35 N, and 318 MPa, respectively, indicating that the ceramic reinforcing layer significantly improves the membrane's resistance to deformation and puncture. Example 5, due to the introduction of dynamically reconfigurable or low-melting-point self-healing components, showed an increased elongation at break of 72%, demonstrating good flexibility and interfacial adaptability. In contrast, Comparative Example 2, without a ceramic reinforcing layer, showed significantly reduced tensile strength, puncture strength, and compressive modulus, indicating that the lack of ceramic reinforcement weakens the membrane's mechanical support and is detrimental to suppressing lithium dendrite penetration. These results demonstrate that the present invention, through the synergistic design of the ceramic reinforcing layer and the self-healing layer on the negative electrode side, can improve the mechanical stability of the composite solid electrolyte membrane while maintaining a certain degree of flexibility.

[0094] The impedance of the composite solid electrolyte membranes in Examples 1-6 significantly increased after the introduction of micro-scratches or local micro-cracks, indicating that interfacial damage disrupts lithium-ion transport channels. After treatment at 70°C and 2 MPa for 30 min, the impedance of Examples 1-6 significantly decreased, with impedance recovery rates reaching 88.9%, 87.5%, 92.2%, 81.6%, 96.1%, and 89.7%, respectively. This indicates that the self-healing layer on the negative electrode side can undergo chain segment migration, local softening, or dynamic reconstruction under heat and pressure, thereby restoring the continuity of ion transport in the damaged area. Among them, Example 5, using polycaprolactone or a dynamically reconfigurable polymer as the self-healing component, showed the best impedance recovery effect; Example 4, due to its high content of ceramic-reinforced filler, had a slightly lower recovery rate because polymer chain segment migration was somewhat restricted. In contrast, Comparative Example 3, without a self-healing layer, and Comparative Example 4, with a homogeneous structure, had lower impedance recovery rates, indicating that without a self-healing functional layer on the negative electrode side, it is difficult to effectively restore the ion pathway after membrane damage. Although Comparative Example 2 exhibits a high impedance recovery rate, mechanical performance tests reveal that it lacks a ceramic reinforcement layer, resulting in insufficient puncture resistance. These results demonstrate that the present invention, through the synergistic design of a self-healing layer on the negative electrode side and a ceramic reinforcement layer, can simultaneously improve both interfacial damage repair capability and membrane structural stability.

[0095] The composite solid electrolyte membranes obtained in Examples 1-6 all exhibited relatively stable lithium deposition / stripping behavior in Li / electrolyte membrane / Li symmetric batteries, without short circuits after long-term cycling, and with minimal polarization voltage increase. Specifically, Example 4, due to its high ceramic reinforcement layer content, demonstrated strong resistance to dendrite penetration and could cycle stably for 1200 hours. Example 5, with its self-healing layer on the negative electrode side exhibiting good interface wetting and defect repair capabilities, showed the lowest polarization voltage during cycling. In contrast, Comparative Example 3, lacking a self-healing layer, experienced gradual deterioration of the interface contact during cycling; Comparative Example 2, also lacking a ceramic reinforcement layer, had insufficient resistance to dendrite penetration; and Comparative Example 4, being a homogeneous composite membrane, lacked the gradient structure and the synergistic effect of ceramic reinforcement and self-healing, resulting in the earliest short circuit time and the most significant polarization increase. These results demonstrate that the composite solid electrolyte membrane of the present invention can effectively stabilize the lithium metal negative electrode interface, reduce cyclic polarization, and improve resistance to lithium dendrite penetration.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite solid electrolyte membrane, characterized in that, include: A positive electrode side high ion conductive layer, wherein the positive electrode side high ion conductive layer comprises a first polymer matrix, a lithium salt and an inorganic fast ion conductor filler; A gradient transition layer comprising a second polymer matrix, a lithium salt, an inorganic fast ion conductor filler, and a ceramic reinforcing filler; A ceramic reinforcement layer comprising a first polymer matrix, a lithium salt, and a ceramic reinforcement filler; A negative electrode side self-healing layer, wherein the negative electrode side self-healing layer comprises a second polymer matrix and a lithium salt; The positive electrode side high ion conductivity layer, the gradient transition layer, the ceramic reinforcement layer, and the negative electrode side self-healing layer are stacked sequentially along the thickness direction of the electrolyte membrane.

2. The composite solid electrolyte membrane according to claim 1, characterized in that, The first polymer matrix is ​​selected from at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polycarbonate polymers, polycaprolactone, polymethyl methacrylate, polysiloxane, and polyurethane; And / or, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium iodide, lithium nitrate, and lithium fluoride.

3. The composite solid electrolyte membrane according to claim 1, characterized in that, The inorganic fast ion conductor filler is selected from Li7La3Zr2O 12 Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li6PS5Cl, Li 10 GeP2S 12 At least one of Li3InCl6, Li3YCl6 and their doped and modified materials; The inorganic fast ion conductor filler in the high ion conductive layer on the positive electrode side has a mass fraction of 5% to 60%.

4. The composite solid electrolyte membrane according to claim 1, characterized in that, The ceramic reinforcing filler is selected from at least one of LLZO, LATP, LAGP, Al2O3, SiO2, TiO2, ZrO2, BN, MgO, LiF, Li3N and their surface-modified products; The ceramic reinforcing filler in the ceramic reinforcing layer has a mass fraction of 10% to 80%.

5. The composite solid electrolyte membrane according to claim 1, characterized in that, The second polymer matrix is ​​selected from at least one of low-melting-point polymers, dynamically reconfigurable polymers, ion-conducting polymers, and their composites; The low-melting-point polymer is selected from at least one of polyethylene glycol, low molecular weight polyethylene oxide, polycaprolactone and its copolymers; the dynamically reconfigurable polymer is selected from at least one of polymers containing hydrogen bonds, ionic bonds, borate ester bonds, disulfide bonds, imine bonds, metal coordination bonds, and host-guest interactions.

6. The composite solid electrolyte membrane according to claim 1, characterized in that, The contents of the second polymer matrix, lithium salt, inorganic fast ion conductor filler, and ceramic reinforcing filler in the gradient transition layer vary along the film thickness direction in a continuous gradient, a step gradient, or a semi-continuous gradient. And / or, the structure of the composite solid electrolyte membrane is selected from at least one of the following: layered structure, continuous gradient structure, interlayer interpenetrating structure, and localized reinforcement structure.

7. The composite solid electrolyte membrane according to claim 1, characterized in that, The thickness of the high-ion conductive layer on the positive electrode side is 1μm~100μm; the thickness of the gradient transition layer is 1μm~150μm; the thickness of the ceramic reinforcement layer is 1μm~100μm; the thickness of the self-healing layer on the negative electrode side is 1μm~50μm; and the total thickness of the composite solid electrolyte membrane is 10μm~300μm.

8. A method for preparing the composite solid electrolyte membrane according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Preparation of high ion conductive layer slurry on the positive electrode side: The first polymer matrix, lithium salt and inorganic fast ion conductor filler are dispersed in an organic solvent to obtain a uniform high ion conductive layer slurry on the positive electrode side; (2) Preparation of gradient transition layer slurry: The second polymer matrix, lithium salt, inorganic fast ion conductor filler and ceramic reinforcing filler are mixed in a preset gradient ratio to obtain gradient transition layer slurry; (3) Preparation of ceramic reinforcement layer slurry: The first polymer matrix, lithium salt and ceramic reinforcement filler are mixed and dispersed to obtain ceramic reinforcement layer slurry; (4) Preparation of self-healing layer slurry on the negative electrode side: Mix low melting point polymer, dynamic reconfigurable polymer, lithium salt, plasticizer, crosslinking agent and ionic liquid to obtain self-healing layer slurry on the negative electrode side; (5) The slurry obtained in steps (1) to (4) is molded in sequence to form a film consisting of a high ion conductivity layer on the positive electrode side, a gradient transition layer, a ceramic reinforcement layer and a self-healing layer on the negative electrode side. (6) The membrane obtained in step (5) is dried and hot-pressed to make the layers tightly bonded, thus obtaining the composite solid electrolyte membrane.

9. The preparation method according to claim 8, characterized in that, The organic solvent mentioned in step (1) is selected from at least one of acetonitrile, N-methylpyrrolidone, tetrahydrofuran, dimethylformamide, dimethylacetamide, ethanol, water and mixed solvents thereof; And / or, the hot pressing temperature in step (6) is 40℃~150℃, the pressure is 0.1MPa~20MPa, and the hot pressing time is 1min~120min.

10. A solid-state battery, characterized in that, The composite solid electrolyte membrane according to any one of claims 1 to 7 includes a positive electrode, a negative electrode, and a composite solid electrolyte membrane disposed between the positive electrode and the negative electrode.

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