Solid electrolyte diaphragm, preparation method thereof and battery

Abstract

The invention relates to the technical field of batteries, in particular to a solid electrolyte diaphragm, a preparation method thereof and a battery. The solid electrolyte diaphragm comprises a porous composite skeleton, a solid electrolyte matrix layer and an interface modification layer which are sequentially compounded, the porous composite skeleton comprises ceramic fibers and a polymer base material, and the porous composite skeleton is of a three-dimensional network structure; pores of the porous composite skeleton are at least partially filled with the solid electrolyte matrix layer, and the solid electrolyte matrix layer comprises a lithium salt, a polymer matrix and an inorganic filler; wherein the ceramic fiber and the inorganic filler have the same crystal structure, and the polymer substrate of the porous composite skeleton and the polymer substrate of the solid electrolyte substrate layer are made of the same material. The solid electrolyte diaphragm disclosed by the invention has the properties of high mechanical strength, low interface impedance and high ionic conductivity, and can effectively inhibit lithium dendrites.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a solid electrolyte separator, its preparation method, and a battery. Background Technology

[0002] Solid-state lithium batteries have become the core development direction of the next generation of lithium batteries due to their advantages such as high energy density and good safety. The solid electrolyte membrane is a key component that determines the performance of solid-state lithium batteries. It needs to meet the requirements of high ionic conductivity, excellent mechanical strength, good interfacial compatibility and suppression of lithium dendrite growth.

[0003] Existing solid electrolyte membranes mainly fall into three categories: polymer-based, ceramic-based, and composite-based. Polymer-based solid electrolytes offer good flexibility and processability, but suffer from low mechanical strength, are easily punctured by lithium dendrites, and have insufficient ionic conductivity. Ceramic-based solid electrolytes (such as LLZTO) exhibit high ionic conductivity and excellent mechanical strength, but are brittle, difficult to process, have poor compatibility with electrode interfaces, and are prone to interfacial impedance. Composite-based solid electrolytes, through the combination of polymers and ceramic materials, achieve a balance between flexibility and mechanical strength to some extent, but still have the following problems: The unreasonable pore structure of the composite framework leads to uneven solid electrolyte loading and discontinuous ion transport channels; there is a serious charge transfer resistance at the electrolyte-electrode interface, which affects the rate performance of the battery; mechanical strength and ionic conductivity are difficult to optimize simultaneously, and lithium dendrite growth cannot be effectively suppressed.

[0004] For example, existing technologies disclose ceramic-polymer composite solid electrolytes, which are prepared by blending ceramic particles with polymers. Although this improves mechanical strength, it results in high interfacial impedance (≥100 Ω·cm). 2 Furthermore, ceramic particles are prone to agglomeration, affecting ion transport. Existing technology also discloses an electrospun composite solid electrolyte, using ceramic fiber-reinforced polymer matrix, which increases mechanical strength to 10 MPa, but its ionic conductivity is only 5 × 10⁻⁶ at 25°C. -5 The current S / cm ratio is insufficient to meet practical application requirements. Current composite electrolytes suffer from two main problems: a "dead zone"—poor ion conduction at the ceramic filler-polymer interface; and an "interface mismatch"—high impedance caused by physical / chemical incompatibility between rigid ceramics and flexible polymers, and between the electrolyte and electrode.

[0005] Therefore, developing a composite solid electrolyte membrane that combines high mechanical strength, low interfacial impedance, and high ionic conductivity has become the key to solving the bottleneck of solid-state lithium battery industrialization. Summary of the Invention

[0006] This invention provides a solid electrolyte separator, its preparation method, and a battery, which solves the technical problems of insufficient mechanical strength, high interfacial impedance, low ionic conductivity, and poor lithium dendrite suppression effect of existing solid electrolyte separators.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A solid electrolyte membrane includes a porous composite framework, a solid electrolyte matrix layer, and an interface modification layer sequentially laminated together. The porous composite framework comprises ceramic fibers and a polymer substrate, and the porous composite framework has a three-dimensional network structure. The solid electrolyte matrix layer at least partially fills the pores of the porous composite framework. The solid electrolyte matrix layer comprises lithium salt, a polymer matrix, and an inorganic filler. The ceramic fibers and the inorganic filler have the same crystal structure, and the polymer substrate of the porous composite framework and the polymer matrix of the solid electrolyte matrix layer are made of the same material.

[0008] In some embodiments, the ceramic fiber is lithium lanthanum zirconium tantalum oxide fiber, the inorganic filler is lithium lanthanum zirconium tantalum oxide nanoparticles; and / or, the polymer substrate of the porous composite skeleton and the polymer matrix of the solid electrolyte matrix layer are polyvinylidene fluoride-hexafluoropropylene.

[0009] In some embodiments, the ceramic fiber has a diameter of 50-500 nm and an aspect ratio greater than 20; and / or, the inorganic filler has a particle size of 10-100 nm.

[0010] In some embodiments, the mass ratio of the ceramic fiber to the polymer substrate is 4:6 to 6:4.

[0011] In some embodiments, the porosity of the porous composite skeleton is 40%-70%.

[0012] In some embodiments, the mass ratio of lithium salt, polymer matrix, and inorganic filler in the solid electrolyte matrix layer is 3:5:2-5:4:1.

[0013] In some embodiments, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide. In some embodiments, the interface modification layer is a lithium-ion graphene layer.

[0014] The present invention also provides a method for preparing the above-mentioned solid electrolyte membrane, comprising the following preparation steps: (1) Preparation of porous composite skeleton: Ceramic fiber and polymer substrate are dissolved in organic solvent, ultrasonically dispersed to form spinning solution, fiber membrane is prepared by electrospinning process, and then the fiber membrane is vacuum dried to obtain porous composite skeleton layer; (2) Preparation of solid electrolyte slurry: Lithium salt, polymer matrix and inorganic filler are mixed in proportion, organic solvent is added and stirred until the raw material components are completely dissolved to form a uniform slurry; (3) Loaded solid electrolyte matrix layer: The slurry from step (2) is coated on the surface of the porous composite skeleton and then vacuum dried to solidify the slurry on the surface and inside the pores of the porous composite skeleton to form a solid electrolyte matrix layer. (4) Preparation of interface modification layer: The interface modification material is dispersed in anhydrous ethanol to form a dispersion, which is then coated on the surface of the solid electrolyte matrix layer by spraying or dipping. After vacuum drying, a composite solid electrolyte membrane is obtained.

[0015] The present invention also provides a battery comprising the above-described solid electrolyte separator.

[0016] The beneficial effects of this invention are: This invention achieves high mechanical strength, high bulk ionic conductivity, and low interfacial impedance by constructing a coherent ion transport channel inside a solid electrolyte membrane and simultaneously realizing an atomic / molecular level compatible interface with the electrode.

[0017] The solid electrolyte membrane of the present invention uses ceramic fiber as the skeleton fiber of the porous composite skeleton, and uses a material with the same crystal structure as the ceramic fiber as the inorganic filler of the solid electrolyte matrix layer. By utilizing their consistent crystal structure and lithium ion migration activation energy, an ion transport highway network from the nanometer to the micrometer scale is formed in the solid electrolyte membrane, which is beneficial to significantly reduce the interfacial impedance.

[0018] Secondly, the polymer substrate of the porous composite framework of the present invention and the polymer matrix of the solid electrolyte matrix layer are made of the same polymer material, which ensures excellent physical fusion and chemical compatibility between the porous composite framework and the solid electrolyte matrix layer and avoids interlayer delamination.

[0019] The present invention also provides an interface modification layer on the surface of the solid electrolyte matrix layer. The interface modification layer can provide uniform nucleation sites to guide uniform lithium deposition; and it has high thermal conductivity, which is beneficial to eliminate local "hot spots" at the dendrite tips and inhibit dendrite growth. Detailed Implementation

[0020] To make the objectives, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. The embodiments described below are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art in conjunction with the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed; where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0021] In the description of 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.

[0022] In the description of 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 mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0023] It should be understood that the weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope of this invention. Specifically, the weights mentioned in the embodiments of this invention can be well-known units of mass in the chemical industry, such as μg, mg, g, and kg.

[0024] Furthermore, unless the context explicitly uses it otherwise, the singular form of a word should be understood as including the plural form of that word. The terms "comprising" or "having" are intended to specify the presence of a feature, quantity, step, operation, element, part, or combination thereof, but are not intended to exclude the presence or possible addition of one or more other features, quantities, steps, operations, elements, parts, or combinations thereof.

[0025] This invention provides a solid electrolyte membrane comprising a porous composite framework, a solid electrolyte matrix layer, and an interface modification layer sequentially laminated together. The porous composite framework comprises ceramic fibers and a polymer substrate, and the porous composite framework has a three-dimensional network structure. The solid electrolyte matrix layer at least partially fills the pores of the porous composite framework. The solid electrolyte matrix layer comprises lithium salt, a polymer matrix, and an inorganic filler. The ceramic fibers and the inorganic filler have the same crystal structure, and the polymer substrate of the porous composite framework and the polymer matrix of the solid electrolyte matrix layer are made of the same material.

[0026] The solid electrolyte membrane of the present invention uses ceramic fiber as the skeleton fiber of the porous composite skeleton, and uses a material with the same crystal structure as the ceramic fiber as the inorganic filler of the solid electrolyte matrix layer. By utilizing their consistent crystal structure and lithium ion migration activation energy, an ion transport highway network from the nanometer to the micrometer scale is formed in the solid electrolyte membrane, which is beneficial to significantly reduce the interfacial impedance.

[0027] Secondly, the polymer substrate of the porous composite framework of the present invention and the polymer matrix of the solid electrolyte matrix layer are made of the same polymer material, which ensures excellent physical fusion and chemical compatibility between the porous composite framework and the solid electrolyte matrix layer and avoids interlayer delamination.

[0028] The present invention also provides an interface modification layer on the surface of the solid electrolyte matrix layer. The interface modification layer can provide uniform nucleation sites to guide uniform lithium deposition; and it has high thermal conductivity, which is beneficial to eliminate local "hot spots" at the dendrite tips and inhibit dendrite growth.

[0029] In some embodiments, the ceramic fiber is lithium lanthanum zirconium tantalum oxide fiber, the inorganic filler is lithium lanthanum zirconium tantalum oxide nanoparticles; and / or, the polymer substrate of the porous composite skeleton and the polymer matrix of the solid electrolyte matrix layer are polyvinylidene fluoride-hexafluoropropylene.

[0030] This invention defines the ceramic fiber as lithium lanthanum zirconium tantalum oxide (LLZTO) fiber and the inorganic filler as lithium lanthanum zirconium tantalum oxide nanoparticles. This ensures that the reinforcing phase in the porous composite framework and the inorganic filler in the solid electrolyte matrix layer are completely identical in chemical composition and crystal structure, thereby achieving atomic-level lattice matching at the interface. This significantly reduces the interfacial impedance between ceramic-polymer and ceramic-ceramic layers, constructing a continuous, low-resistance lithium-ion transport channel. Simultaneously, the LLZTO material itself possesses high ionic conductivity and excellent electrochemical stability, contributing to an overall improvement in the ion conductivity and stability of the separator against lithium metal.

[0031] Furthermore, the polymer substrate of the porous composite framework and the polymer matrix of the solid electrolyte matrix layer are unified as polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). This copolymer possesses excellent dielectric properties, film-forming properties, flexibility, and high solubility for lithium salts. It not only facilitates lithium salt dissociation and increases ion transport number but also exhibits good compatibility with the LLZTO component, reducing phase separation and further optimizing the uniformity of the composite structure and the interfacial bonding strength. The introduction of PVDF-HFP also effectively buffers the brittleness of the ceramic component, improving the overall mechanical flexibility and processing adaptability of the membrane.

[0032] In summary, by selecting the constituent materials of the porous composite framework and the solid electrolyte matrix layer, this invention achieves synergistic optimization of crystal structure consistency, ion transport continuity, interface compatibility and mechanical properties, effectively solving the problems of "dead zone" and "interface mismatch" existing in existing composite solid electrolytes.

[0033] In some embodiments, the ceramic fiber has a diameter of 50-500 nm and an aspect ratio greater than 20; and / or, the inorganic filler has a particle size of 10-100 nm.

[0034] This invention limits the diameter of ceramic fibers to 50-500 nm and the aspect ratio to greater than 20. The nanoscale diameter and high aspect ratio of the ceramic fibers enable the construction of a highly interconnected three-dimensional network structure within a porous composite framework formed by electrospinning. This high aspect ratio fiber not only significantly improves the mechanical strength and puncture resistance of the framework (effectively suppressing lithium dendrite penetration), but also forms a continuous rigid support within the polymer matrix, preventing deformation or collapse of the separator during battery cycling. Simultaneously, the nanoscale fiber surface provides a larger specific surface area, facilitating sufficient contact with the polymer matrix and subsequently filled solid electrolyte, thus enhancing interfacial adhesion.

[0035] The inorganic filler uses 10-100nm nanoparticles, which can effectively fill the micropores and gaps in the polymer matrix of the porous composite framework, reduce the "dead volume", and improve the density and uniformity of the solid electrolyte matrix layer. On the other hand, the nano-size effect helps to reduce the migration barrier of lithium ions at the filler-polymer interface and form a "fiber-particle" synergistic conductive network with ceramic fibers with the same crystal structure, realizing the connection of cross-scale ion transport channels from the micron-scale framework to the nano-scale filler, and significantly improving the overall ionic conductivity.

[0036] In summary, by precisely controlling the dimensional parameters of ceramic fibers and inorganic fillers, a triple technical effect of high-strength skeleton construction, efficient ion transport network formation, and improved interface uniformity is achieved, which is beneficial to improving the mechanical strength and ionic conductivity of solid electrolyte membranes and reducing their interfacial impedance.

[0037] In some embodiments, the mass ratio of the ceramic fiber to the polymer substrate is 4:6 to 6:4.

[0038] This invention, by limiting the mass ratio of ceramic fibers to polymer substrate to 4:6-6:4, effectively enhances the mechanical properties, ion transport capacity, and structural stability of the separator. When the proportion of ceramic fibers is too low, the skeleton cannot form an effective rigid support network, resulting in insufficient mechanical strength and an inability to effectively suppress lithium dendrite penetration. Conversely, when the proportion of ceramic fibers is too high, the polymer substrate is insufficient to fully cover and bond the fibers, leading to increased skeleton brittleness, easy breakage, and decreased processability. Controlling the mass ratio within the range of 4:6-6:4 ensures that the ceramic fibers construct a continuous, high-strength three-dimensional network, providing excellent puncture resistance, while retaining sufficient polymer phase to maintain the separator's flexibility and processability.

[0039] On the other hand, this ratio range helps to form a uniform, interconnected, and appropriately sized pore structure during electrospinning, avoiding loose fiber bonding and excessively large pores due to insufficient polymer, or pore blockage due to excessive polymer. The resulting porous framework has good porosity and surface wettability, which is beneficial for the uniform penetration and loading of subsequent solid electrolyte slurry, reducing "voids" or "enriched areas" and ensuring the continuity of ion transport channels. At this ratio, a tight physical entanglement and chemical interaction are formed between the ceramic fibers and the polymer substrate, significantly reducing interphase interface defects and minimizing ion transport "dead zones." Simultaneously, this ratio balances the high ion conductivity potential of the inorganic phase with the interfacial buffering effect of the organic phase, helping to reduce overall interfacial impedance and improve the rate performance and cycle life of the battery.

[0040] In some embodiments, the porosity of the porous composite skeleton is 40%-70%.

[0041] This invention limits the porosity of the porous composite framework to 40%–70%, which, while ensuring the mechanical integrity of the membrane, helps to improve the uniform loading and ion transport capacity of the solid electrolyte matrix layer.

[0042] When the porosity is below 40%, the porous composite framework has too few or too narrow pores, making it difficult for the subsequently coated solid electrolyte slurry to fully penetrate into the framework. This results in the electrolyte mainly accumulating on the surface, forming a non-uniform structure that is dense on the outside and sparse on the inside, which easily creates ion transport bottlenecks. Conversely, when the porosity is above 70%, the framework fiber network is too sparse, and the mechanical strength decreases significantly. Controlling the porosity within the range of 40%-70% ensures that the slurry penetrates uniformly into the entire three-dimensional network, allowing the solid electrolyte matrix layer to solidify simultaneously on the framework surface and within the pores, forming a continuous, dense, and defect-free composite structure.

[0043] In some embodiments, the porous composite skeleton has a tensile strength greater than or equal to 15 MPa and an elongation at break greater than or equal to 20%.

[0044] In some embodiments, the mass ratio of lithium salt, polymer matrix, and inorganic filler in the solid electrolyte matrix layer is 3:5:2-5:4:1.

[0045] This invention optimizes the ratio of ion-conducting phase, continuous flexible phase, and inorganic reinforcing / conducting phase at the molecular scale by limiting the mass ratio of lithium salt, polymer matrix, and inorganic filler in the solid electrolyte matrix layer to 3:5:2-5:4:1. This maximizes ionic conductivity and reduces interfacial impedance while ensuring mechanical integrity, thereby achieving a synergistic improvement in electrochemical performance and structural stability.

[0046] When the lithium salt content is too low, it can lead to the movement of Li... + Insufficient lithium salt content limits ionic conductivity; while excessive content can lead to salt precipitation, crystallization, or decreased polymer compatibility, thus creating an obstacle to ion transport. Controlling the lithium salt ratio at 30%-50% (i.e., 3-5 parts by mass), combined with a polymer matrix with high dielectric constant, can effectively promote lithium salt dissociation and increase the free lithium content. + The concentration should be controlled, while avoiding phase separation or interfacial side reactions caused by excessive salt.

[0047] The polymer matrix, as a continuous phase, not only provides flexible support and film-forming ability, but its polar groups can also interact with Li. + Coordination facilitates ion migration; inorganic fillers, as active fillers, not only provide additional lithium-ion conduction pathways but also inhibit polymer crystallization, increase the proportion of amorphous regions, and further enhance ion mobility. Within this proportion range, the inorganic fillers are uniformly dispersed without agglomeration, forming a multi-scale ion highway with the polymer and isomorphous ceramic fiber skeleton, significantly reducing bulk and interfacial impedance.

[0048] If the proportion of inorganic filler is too high, it will weaken the continuity of the polymer, leading to increased brittleness and poor interfacial contact; if it is too low, it will not be able to effectively suppress lithium dendrites and improve conductivity. The proportion range defined in this invention is more conducive to enhancing mechanical strength, maintaining good flexibility, and improving ionic conductivity. At the same time, an appropriate amount of inorganic filler can also adsorb trace amounts of moisture or HF impurities, improving the electrochemical window stability of the electrolyte.

[0049] At 25°C, the ionic conductivity of the solid electrolyte matrix layer is greater than or equal to 10. -4 S / cm.

[0050] In some embodiments, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

[0051] This invention significantly improves the ionic conductivity, electrochemical stability, and interfacial compatibility of solid electrolyte membranes by limiting the lithium salt to lithium bis(trifluoromethanesulfonylimide) (LiTFSI), effectively overcoming the problems of traditional lithium salts (such as LiClO4, LiPF6, etc.) in solid systems, such as difficulty in dissociation, poor thermal stability, and easy reaction with electrode side reactions.

[0052] LiTFSI possesses a large anionic radius and a highly delocalized negatively charged structure, giving it extremely strong dissociation capabilities in polymer matrices (such as PVDF-HFP), enabling it to generate high concentrations of free Li even at room temperature. + Meanwhile, its anion (TFSI) - A lower migration number helps improve Li + The migration number is increased, concentration polarization is reduced, thereby significantly improving the overall ionic conductivity of the solid electrolyte and meeting the requirements of high-rate charge and discharge.

[0053] LiTFSI exhibits a wide electrochemical stability window, allowing for good compatibility with high-voltage cathode materials (such as NCM811 and LCO) and preventing oxidative decomposition at high potentials. Simultaneously, its thermal decomposition temperature exceeds 360℃, significantly better than LiPF6 (<200℃), substantially improving battery safety under high-temperature or abusive conditions. Furthermore, LiTFSI has low moisture sensitivity and is less prone to hydrolysis and acid formation in solid-state systems, reducing corrosion at the electrode / electrolyte interface and extending battery cycle life.

[0054] TFSI - Anions can form weak interactions with fluorine atoms in PVDF-HFP, promoting polymer chain segment movement, lowering the glass transition temperature (Tg), increasing the proportion of amorphous regions, and benefiting Li + Migration; at the same time, LiTFSI can also form a stable LiF-rich or sulfur-containing interface layer on the surface of inorganic fillers such as LLZTO, passivate surface defects of the filler, reduce the space charge layer effect, thereby significantly reducing the ceramic-polymer interface impedance and alleviating the "dead zone" problem.

[0055] In some embodiments, the interface modification layer is a lithium-ion graphene layer.

[0056] Using lithium-ionized graphene as an interface modification layer can provide uniform nucleation sites and guide uniform lithium deposition. On the other hand, the high thermal conductivity of graphene can be used to eliminate local "hot spots" at the dendrite tips and inhibit dendrite growth. At the same time, the two-dimensional structure and high lithium-ion affinity can not only physically cover and reduce resistance, but also chemically guide the uniform distribution of lithium-ion flow, thus inhibiting dendrite growth at the source.

[0057] Specifically, the lithium-ion graphene is chemically bonded to the surface of the solid electrolyte matrix layer.

[0058] The tensile strength of the solid electrolyte membrane is greater than or equal to 15 MPa, and the room temperature ionic conductivity is greater than or equal to 10. -4 S / cm, the interfacial impedance with the lithium metal anode is less than or equal to 50 Ω·cm. 2 The contact angle with the lithium metal electrode is less than or equal to 30°.

[0059] The present invention also provides a method for preparing the above-mentioned solid electrolyte membrane, comprising the following preparation steps: (1) Preparation of porous composite skeleton: Ceramic fiber and polymer substrate are dissolved in organic solvent, ultrasonically dispersed to form spinning solution, fiber membrane is prepared by electrospinning process, and then the fiber membrane is vacuum dried to obtain porous composite skeleton layer; (2) Preparation of solid electrolyte slurry: Lithium salt, polymer matrix and inorganic filler are mixed in proportion, organic solvent is added and stirred until the raw material components are completely dissolved to form a uniform slurry; (3) Loaded solid electrolyte matrix layer: The slurry from step (2) is coated on the surface of the porous composite skeleton and then vacuum dried to solidify the slurry on the surface and inside the pores of the porous composite skeleton to form a solid electrolyte matrix layer. (4) Preparation of interface modification layer: The interface modification material is dispersed in anhydrous ethanol to form a dispersion, which is then coated onto the surface of the solid electrolyte matrix layer by spraying or dipping. After vacuum drying, an interface modification layer is formed on the surface of the solid electrolyte matrix layer to obtain a composite solid electrolyte membrane.

[0060] This invention employs an electrospinning process to co-spin ceramic fibers and a polymer substrate into a film, allowing for precise control of the three-dimensional network structure. Combined with subsequent vacuum drying, solvent residue is effectively removed, preventing pore collapse. This step ensures that the porous composite framework possesses a high-porosity interconnected network and excellent mechanical strength, providing an ideal support platform for subsequent electrolyte loading.

[0061] By coating and vacuum drying a slurry containing lithium salt, polymer matrix and inorganic filler onto a porous framework, the slurry fully wets the pores inside the framework, achieving integrated filling on the surface and inside the pores of the porous composite framework. This ensures the continuous distribution of the solid electrolyte, significantly reduces bulk impedance and improves ionic conductivity.

[0062] Interface-modifying materials can be introduced onto the surface of a solid electrolyte matrix layer using spraying or dip coating. This method is simple, allows for controllable thickness, and enables the material to form a good chemical bond with the underlying layer. This modified layer not only provides uniform lithium deposition nucleation sites and inhibits dendrite growth, but also dissipates localized "hot spots" due to its high thermal conductivity, thus improving interfacial thermal management and significantly reducing electrode / electrolyte interface impedance.

[0063] In some implementations, the ultrasonic dispersion time in step (1) is 30-60 min.

[0064] In some embodiments, in step (1), the mass ratio of ceramic fiber to polymer substrate is 4:6-6:4, and the total mass of ceramic fiber and polymer substrate accounts for 5%-15% of the mass of spinning solution.

[0065] In some embodiments, in step (1), the spinning voltage is 15-25kV, the receiving distance is 10-20cm, and the spinning rate is 0.5-2mL / h.

[0066] The spinning voltage is controlled within the range of 15-25kV. The electrostatic force is sufficient to overcome the surface tension of the spinning solution, forming a stable Taylor cone and generating a continuous jet. This avoids situations where the voltage is too low, leading to insufficient spraying and resulting in coarse fibers or beaded structures, or too high, causing excessive current splitting, resulting in fiber breakage and increased fly waste. This voltage range is suitable for composite spinning solutions containing high-dielectric-constant ceramic fibers (such as LLZTO), effectively promoting uniform stretching of charged particles in the electric field and preventing the ceramic components from settling or agglomerating due to gravity or polarity differences.

[0067] The spinning rate is controlled at 0.5-2 mL / h. The low liquid supply rate ensures that the solvent has enough time to evaporate during the flight, avoiding excessive solvent residue during fiber deposition that could lead to adhesion or pore closure. At the same time, this rate is matched with the voltage to maintain jet stability and obtain composite nanofibers with uniform diameter and smooth surface, which is beneficial for the subsequent construction of a high-porosity, high-strength skeleton.

[0068] A receiving distance of 10-20 cm ensures sufficient stretching and solvent evaporation during jet flight, resulting in dry, independent fibers. Too short a distance leads to undried solvent, fiber adhesion, and reduced porosity; too long a distance may cause fiber breakage or uneven deposition due to jet instability. A receiving distance of 10-20 cm, combined with the aforementioned voltage and flow rate, can form a highly interconnected, highly porous, and uniformly sized three-dimensional network structure, facilitating unobstructed channels for subsequent electrolyte slurry penetration.

[0069] In summary, by precisely controlling the key process parameters of electrospinning, this invention facilitates the preparation of porous composite frameworks with controllable fiber diameter, uniform distribution, reasonable pore structure, and high mechanical integrity. It effectively solves the problems of uneven electrolyte loading, discontinuous ion channels, and weak interfacial bonding caused by framework defects in traditional composite electrolytes, which is beneficial for the subsequent construction of solid electrolyte membranes with high ionic conductivity and high dendrite resistance.

[0070] In some embodiments, the vacuum drying conditions in step (1) are 60-120°C for 12-24 hours.

[0071] If organic solvents used in electrospinning remain in the fiber membrane, they will not only reduce the polymer's crystallinity and mechanical strength, but may also react with lithium metal or high-voltage cathodes during subsequent battery assembly or cycling, generating gas or impedance layers. Controlling the drying temperature within the range of 60-120℃, higher than the boiling point of commonly used solvents but lower than the thermal decomposition temperature of the polymer substrate, allows for efficient solvent removal without damaging the fiber morphology. Controlling the drying time to 12-24 hours ensures that the solvent fully diffuses and escapes from the dense fiber interior and the micropores between fibers. Especially for thick films formed by high-viscosity spinning solutions or high-ceramic-content skeletons, extending the drying time can significantly reduce residual solvent content and improve membrane purity and electrochemical stability.

[0072] Under normal pressure or high-temperature rapid drying conditions, the violent evaporation of solvent can easily lead to a sudden increase in capillary force, causing fiber shrinkage, pore closure, and even membrane embrittlement. This invention dries the fiber in a vacuum environment, significantly lowering the solvent boiling point and allowing the solvent to evaporate smoothly at a lower temperature. This effectively suppresses capillary stress and maintains the high porosity and open pore structure formed by electrospinning. Furthermore, by controlling the drying temperature within the range of 60-120℃, this invention avoids rapid hardening of the fiber surface and solvent retention inside, thus preserving uniform and interconnected pore channels. This provides structural assurance for the full penetration and uniform filling of the subsequent solid electrolyte slurry.

[0073] During vacuum drying, moderate heat treatment (especially in the range of 80–120℃) can cause local rearrangement of polymer chains such as PVDF-HFP, enhance the physical entanglement and van der Waals effect between fibers, improve the overall cohesion of the skeleton, and help improve the tensile strength and flexibility of porous composite skeletons. At the same time, the interface between ceramic fibers and polymer substrates is more tightly bonded due to thermal relaxation effect, reducing the risk of microcracks or debonding.

[0074] In some embodiments, the organic solvent in step (1) is at least one of N,N-dimethylformamide (DMF), acetone, or ethyl acetate.

[0075] In some embodiments, the organic solvent in step (2) is at least one of acetonitrile, dimethyl carbonate, or tetrahydrofuran.

[0076] In some implementations, the stirring time in step (2) is 6-12 hours and the stirring speed is 800-1000 rpm.

[0077] In some embodiments, the initial coating thickness of the slurry applied to the surface of the porous composite skeleton in step (3) is 50-200 μm.

[0078] In some implementations, the vacuum drying conditions in step (3) are 80-120°C for 4-8 hours.

[0079] By employing a vacuum drying process at 80–120℃ for 4–8 h, a high-uniformity film formation, low solvent residue, strong interfacial fusion, and structural conformation of the solid electrolyte matrix layer were achieved. This not only significantly improved the ionic conductivity and electrochemical stability of the membrane but also ensured the overall mechanical integrity of the multilayer composite structure.

[0080] In some embodiments, the coating method of step (3) is scraping, rolling, or casting.

[0081] In some implementations, the curing process in step (3) employs a gradient heating method with a heating rate of 5-10℃ / h.

[0082] By gradually increasing the temperature by a slow gradient of 5-10℃ / h, the solvent is removed step by step and smoothly according to the boiling point gradient at different temperature stages, avoiding a sudden increase in local vapor pressure. This keeps the film dense, crack-free, and shrinkage-free, achieving shape preservation and uniform filling of the porous composite framework pores, and ensuring the continuity and integrity of the ion transport channels.

[0083] During slow heating, polymers such as PVDF-HFP allow sufficient time for chain segment rearrangement and relaxation, which is beneficial for forming a more uniform amorphous / microcrystalline structure and expanding the Li-chain structure. + Migration channels enhance the interfacial contact between the polymer and LLZTO nanofillers, reducing "dead zones" and improving the dispersion uniformity and dissociation efficiency of lithium salts in the matrix. Gradient heating also avoids microcracks caused by thermal shock-induced mismatch in the coefficients of thermal expansion between the ceramic filler and the polymer, significantly reducing bulk and interfacial impedance and improving overall ionic conductivity.

[0084] A gentle heating rate of 5–10℃ / h ensures that heat is evenly conducted to the entire composite structure, avoiding the accumulation of thermal stress caused by excessive temperature gradients. This effectively maintains the original three-dimensional network morphology and porosity of the porous composite framework, ensuring a strong and seamless composite interface between the solid electrolyte matrix layer and the framework.

[0085] In some embodiments, the mass fraction of the dispersion in step (4) is 0.5%-2%.

[0086] In some embodiments, the vacuum drying conditions in step (4) are 60-100℃ for 2-4 hours.

[0087] High-temperature rapid drying can cause the ethanol solvent to evaporate violently, leading to uneven stacking of graphene sheets, wrinkling of the film, or peeling off from the underlying electrolyte. Low-temperature vacuum drying at 60-100℃ can stably evaporate ethanol, while a suitable drying time of 2-4 hours ensures that the solvent completely escapes from the gaps between the nanosheets, forming a continuous, uniform, and defect-free interface modification layer.

[0088] Lithium-ionized graphene is temperature-sensitive; excessively high temperatures can lead to lithium deintercalation, structural oxidation, or decreased conductivity. This process controls the upper temperature limit below 100℃, effectively preserving its high electronic / ionic mixed conductivity, high specific surface area, and abundant nucleation sites, thereby fully leveraging its function of guiding uniform lithium deposition and suppressing dendrite growth.

[0089] Slow drying in a vacuum environment helps the lithium graphene sheet form van der Waals forces or weak chemical bonds with the underlying PVDF-HFP / LLZTO surface, improving interlayer adhesion, preventing interface delamination due to volume changes during battery cycling, and significantly reducing electrode / electrolyte interface impedance.

[0090] In some embodiments, in step (4), when spraying is used, the spraying pressure is 0.1-0.3MPa and the spraying distance is 10-15cm; when dipping is used, the dipping time is 1-5min and the lifting speed is 5-10mm / min.

[0091] Controlling the pressure between 0.1 and 0.3 MPa provides suitable atomization kinetic energy, which effectively atomizes the lithium-ion graphene dispersion into micron-sized droplets while avoiding excessive pressure that could damage the underlying porous structure or cause localized buildup. Maintaining the spraying distance between 10 and 15 cm ensures sufficient time for droplets to evaporate, decelerate, and settle during flight, resulting in uniform deposition. Too close a distance can lead to an excessively thick wet film and flow, while too far a distance results in over-drying of the droplets and poor adhesion. In summary, controlling the spraying pressure and distance is beneficial for obtaining an ultrathin interface-modified layer, providing ample nucleation sites without significantly increasing ion transport resistance.

[0092] Controlling the immersion time to 1-5 min ensures that the lithium-ion graphene dispersion fully wets the surface and shallow pores of the solid electrolyte matrix layer. Too short a time will result in incomplete wetting, while too long a time will easily lead to excessive adsorption or agglomeration of the filler. The pulling rate should be 5-10 mm / min. This rate range is conducive to precise control of the liquid film thickness and the formation of a uniform coating. Too fast a rate will result in a thin and discontinuous film, while too slow a rate will result in a thick film that is prone to cracking after drying.

[0093] The thickness of the interface modification layer is 5-50 nm.

[0094] In summary, the solid electrolyte membrane of the present invention has the following advantages compared with the prior art: Excellent mechanical strength: Ceramic fibers in the porous composite skeleton layer form a three-dimensional support network, the tensile strength of the diaphragm is ≥15MPa, the elongation at break is ≥20%, which can effectively resist lithium dendrite puncture; High ionic conductivity: The inorganic filler and polymer matrix in the solid electrolyte matrix layer work synergistically, resulting in an ionic conductivity ≥10 at 25℃. -4S / cm, meeting the requirements for use at room temperature; Low interfacial impedance: The interfacial modification layer improves the compatibility between the electrolyte and the electrode, with an interfacial impedance ≤50Ω·cm. 2 Improve battery rate performance; Good cycle stability: The three-layer composite structure synergistically suppresses lithium dendrite growth, and after being assembled into a solid-state lithium battery, the capacity retention rate is ≥85% after 500 cycles; The preparation process is simple: it adopts mature processes such as electrospinning and coating, which are easy to scale up and the cost is controllable.

[0095] The present invention also provides a battery comprising the above-described solid electrolyte separator.

[0096] To enable those skilled in the art to clearly understand the above-described implementation details and operations of the present invention, and to demonstrate the significant advancements in the performance of the embodiments of the present invention, the following examples illustrate the above technical solutions.

[0097] Example 1 The preparation method for solid electrolyte membranes includes the following steps: Step 1: Preparation of a porous composite framework layer: LLZTO ceramic fibers (200 nm in diameter and 5 μm in length) were mixed with PVDF-HFP at a mass ratio of 4:6, and a mixed solvent of DMF and acetone (volume ratio of 1:1) was added. The mixture was ultrasonically dispersed for 45 min to form a spinning solution with a mass fraction of 10%. The fiber membrane was prepared by electrospinning at a voltage of 20 kV, a receiving distance of 15 cm, and a spinning rate of 1 mL / h. The membrane was then vacuum dried at 80 °C for 18 h to obtain a porous composite framework with a porosity of 55%.

[0098] Step 2: Preparation of solid electrolyte slurry: LiTFSI, PVDF-HFP and LLZTO nanoparticles (50 nm in diameter) were mixed in a mass ratio of 4:4:2, acetonitrile solvent was added, and the mixture was stirred for 8 hours until completely dissolved to form a homogeneous slurry.

[0099] Step 3: Loading solid electrolyte matrix layer: The slurry was coated onto the surface of the porous composite skeleton layer by a scraping method, with a coating thickness of 100 μm. The coating was then heated to 100 °C and vacuum dried for 6 h at a heating rate of 8 °C / h to obtain the composite layer.

[0100] Step 4: Prepare the interface modification layer: Lithium-ionized graphene was dispersed in anhydrous ethanol to form a 1% (w / w) dispersion. The dispersion was then coated onto the surface of the composite layer by spraying at a pressure of 0.2 MPa and a distance of 12 cm. The coating was then vacuum dried at 80 °C for 3 h to obtain a composite solid electrolyte membrane. The thickness of the prepared interface-modified layer was 20 nm.

[0101] The preparation method of lithium-ion graphene is as follows: 1) Dissolve 1 part by weight of graphene in 100 parts by weight of deionized water and sonicate at 300W for 40 minutes to obtain a graphene oxide suspension. 2) Transfer the ferric nitrate solution and lithium nitrate solution into the graphene oxide suspension, with a Fe:Li mass ratio of 1:1, and sonicate at 300W for 40 min to obtain a mixed solution; 3) Place the mixture in a vacuum oven and dry it at 70℃ and a vacuum degree ≤0.1MPa until all moisture is removed, then perform grinding. 4) Place the ground sample into a heating device and heat it to 300°C under an inert atmosphere, then stop heating to obtain lithium-ion graphene material.

[0102] Example 2 The preparation method for solid electrolyte membranes includes the following steps: Step 1: Preparation of the composite framework layer: LLZTO ceramic fibers (100 nm in diameter and 3 μm in length) were mixed with PVDF-HFP at a mass ratio of 6:4, DMF solvent was added, and the mixture was ultrasonically dispersed for 30 min to form a spinning solution with a mass fraction of 8%. The electrospinning voltage was 18 kV, the receiving distance was 12 cm, and the spinning rate was 0.8 mL / h to prepare a fiber membrane. The membrane was then vacuum dried at 100 °C for 12 h to obtain a porous composite framework with a porosity of 48%.

[0103] Step 2: Preparation of solid electrolyte slurry: LiTFSI, PVDF-HFP and LLZTO nanoparticles (30 nm in diameter) were mixed in a mass ratio of 3:5:2, dimethyl carbonate solvent was added, and the mixture was stirred for 6 hours to form a uniform slurry.

[0104] Step 3: Loading solid electrolyte matrix layer: The slurry was coated onto the surface of the porous composite skeleton layer by roller coating, with a thickness of 80 μm. It was then heated to 90 °C and vacuum dried for 5 h at a heating rate of 5 °C / h.

[0105] Step 4: Prepare the interface modification layer: Lithium-ionized graphene was dispersed in anhydrous ethanol to form a dispersion with a mass fraction of 0.8%. The immersion coating time was 3 min, the pulling rate was 8 mm / min, and the membrane was vacuum dried at 60 °C for 2 h to obtain a composite solid electrolyte membrane with an interface modification layer thickness of 15 nm.

[0106] The preparation method of lithium graphene is the same as in Example 1.

[0107] Example 3 The preparation method for solid electrolyte membranes includes the following steps: Step 1: Preparation of the composite framework layer: LLZTO ceramic fibers (100 nm in diameter and 3 μm in length) were mixed with PVDF-HFP at a mass ratio of 5:5, DMF solvent was added, and the mixture was ultrasonically dispersed for 60 min to form a spinning solution with a mass fraction of 5%. The electrospinning voltage was 15 kV, the receiving distance was 10 cm, and the spinning rate was 0.5 mL / h to prepare a fiber membrane. The membrane was then vacuum dried at 60 °C for 24 h to obtain a porous composite framework with a porosity of 40%.

[0108] Step 2: Preparation of solid electrolyte slurry: LiTFSI, PVDF-HFP and LLZTO nanoparticles (100 nm in diameter) were mixed at a mass ratio of 5:4:1, dimethyl carbonate solvent was added, and the mixture was stirred for 12 h to form a uniform slurry.

[0109] Step 3: Loading solid electrolyte matrix layer: The slurry was coated onto the surface of the porous composite skeleton layer by roller coating, with a thickness of 200 μm, and then vacuum dried at 120 °C for 4 h at a heating rate of 10 °C / h.

[0110] Step 4: Prepare the interface modification layer: Lithium-ionized graphene was dispersed in anhydrous ethanol to form a 2% (w / w) dispersion. The coating time was 5 min, the pulling rate was 10 mm / min, and the membrane was vacuum dried at 100 °C for 4 h to obtain a composite solid electrolyte membrane. The thickness of the interface modified layer was 15 nm.

[0111] The preparation method of lithium graphene is the same as in Example 1.

[0112] Example 4 The difference between Example 4 and Example 1 is that in Example 4, the ceramic fiber in step one is alumina ceramic fiber, the inorganic filler in step two is alumina nanoparticles, and other process conditions are the same as in Example 1.

[0113] Example 5 The difference between Example 5 and Example 1 is that in Example 5, the polymer substrate in step one and the polymer matrix in step two are both PEO materials, while other process conditions are the same as in Example 1.

[0114] Example 6 The difference between Example 6 and Example 1 is that in Example 6, the lithium graphene in step four is replaced with Li3PO4, while the other process conditions are the same as in Example 1.

[0115] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the preparation method of Comparative Example 1 does not include step four, that is, the solid electrolyte membrane obtained does not contain the interface modification layer. Other process conditions are the same as those in Example 1.

[0116] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the LLZTO ceramic fibers in step one are replaced with LLZTO ceramic particles (particle size 500nm), while the rest of the process is the same.

[0117] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, the inorganic filler in the solid electrolyte slurry is Li3PO4, and the polymer matrix is ​​PEO. Other process conditions are the same as in Example 1.

[0118] Performance testing The membranes prepared in Examples 1-6 and Comparative Examples 1-3 were subjected to the following performance tests, and the test results are recorded in the table.

[0119] 1. Tensile strength test: The tensile strength of the diaphragms in the examples and comparative examples was tested according to the methods in GB / T 36363-2018.

[0120] 2. Elongation at break test: The tensile strength test was conducted simultaneously, and the calculations were based on the same stress-strain curve. Elongation at break (%) = (L...) f -L0) / L0×100%, where L0 is the initial length of the sample, L f This represents the length of the sample when it breaks.

[0121] 3. Ionic conductivity test at 25℃: Electrochemical impedance spectroscopy (EIS) was employed. A circular separator sample was sandwiched between two lithium metal electrodes to form an "SS|Separator|SS" sandwich structure battery, which was then placed in a constant temperature environment at 25°C. A 10mV perturbation signal was applied using an electrochemical workstation, and Nyquist plots were measured in the frequency range of 1MHz-0.1Hz. The intersection of the high-frequency region and the real axis represents the bulk resistance R.b (Ω), ionic conductivity σ (S / cm) = d / (R) b ×A), where d is the diaphragm thickness (cm) and A is the electrode contact area (cm²). 2 Before testing, the sample should be left to stand at 25°C for 2 hours to ensure temperature equilibrium.

[0122] 4. Method for testing interfacial impedance with lithium metal electrode: An electrochemical impedance spectroscopy (EIS) method was used to assemble a “Li|membrane|Li” symmetrical cell. The membrane was placed between two lithium foils in an argon-filled glove box, compressed, and then sealed to the cell casing. After aging at a constant temperature of 25°C for 12 hours, a 10 mV AC signal was applied, with a scanning frequency of 1 MHz–10 mHz. The Nyquist plot typically presents a high-frequency semicircle (bulk impedance) and a low-frequency semicircle (interfacial impedance). The interfacial charge transfer impedance R can be separated by equivalent circuit fitting. int (Ω·cm) 2 ), which is the interfacial impedance value between the separator and the lithium metal electrode.

[0123] 5. Use the electrolyte titration method to test the contact angle between the diaphragm and the electrolyte.

[0124] The separators prepared in Examples 1-6 and Comparative Examples 1-3 were assembled into Li / LiFePO4 solid-state batteries. The capacity retention of the batteries at 0.5C rate and different number of cycles was then tested. The test method is as follows: Coin cells (CR2032 type) were assembled in an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm): a lithium metal sheet was used as the negative electrode, a LiFePO4 positive electrode was used as the positive electrode, and a prepared solid electrolyte membrane was sandwiched in between. After assembly, the cells were sealed and allowed to stand for 6-12 hours to ensure sufficient interface contact.

[0125] Subsequently, the battery was placed in a constant-temperature battery testing system and subjected to constant-current charge-discharge cycle testing at 25°C. The charge-discharge voltage window was set to 2.5-3.6V, and the charge-discharge rate was 0.5C. The discharge specific capacity per cycle was recorded. The capacity retention rate (%) after n cycles was calculated using the formula: Capacity retention rate = discharge specific capacity of the nth cycle / discharge specific capacity of the 1st cycle × 100%.

[0126] Table 1: Test Result Analysis: Compared to Comparative Example 1, which lacks an interface modification layer, the present invention reduces interface impedance by more than 60% and extends cycle life by more than 150%. Comparative Example 1, lacking an interface modification layer (lithium-modified graphene), suffers from a sharp increase in impedance, leading to rapid battery failure.

[0127] Compared to Comparative Example 2, which uses ceramic particles, the mechanical strength of this invention is improved by nearly 100%, effectively solving the dendrite puncture problem. Comparative Example 2 lacks the synergistic effect of LLZTO ceramic fibers and LLZTO ceramic particles, resulting in decreased membrane strength, decreased cell conductivity, increased impedance, and severely deteriorated cycle life.

[0128] Compared to Example 4, which used ceramic fibers and particulate materials for alumina, the choice of LLZTO material yielded better results than other materials.

[0129] Compared to Example 5, where the polymer is PEO, the selection of polymer and ceramic fiber in this invention has a synergistic effect.

[0130] Compared to Example 6, where the modified layer material was Li3PO4, using lithium-ion graphene as the interface modified layer material resulted in a greater improvement in the contact surface.

[0131] In Comparative Example 3, the inorganic filler in the solid electrolyte matrix layer and the ceramic fiber in the skeleton are made of different materials, and the polymer materials are also different. The test results of Comparative Example 3 and Example 1 show that using the same materials for the skeleton and matrix layer in this invention can achieve better results.

[0132] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A solid electrolyte membrane, characterized in that, The invention comprises a porous composite framework, a solid electrolyte matrix layer, and an interface modification layer, which are sequentially composited. The porous composite framework consists of ceramic fibers and a polymer substrate, and has a three-dimensional network structure. The solid electrolyte matrix layer at least partially fills the pores of the porous composite framework and comprises lithium salt, a polymer matrix, and an inorganic filler. The ceramic fibers and the inorganic filler have the same crystal structure, and the polymer substrate of the porous composite framework and the polymer matrix of the solid electrolyte matrix layer are made of the same material.

2. The solid electrolyte membrane according to claim 1, characterized in that, The ceramic fiber is lithium lanthanum zirconium tantalum oxide fiber, and the inorganic filler is lithium lanthanum zirconium tantalum oxide nanoparticles. And / or, the polymer substrate of the porous composite framework and the polymer matrix of the solid electrolyte matrix layer are polyvinylidene fluoride-hexafluoropropylene.

3. The solid electrolyte membrane according to claim 1, characterized in that, The diameter of the ceramic fiber is 50-500 nm, and the aspect ratio of the ceramic fiber is greater than 20. And / or, the particle size of the inorganic filler is 10-100 nm.

4. The solid electrolyte membrane according to claim 1, characterized in that, The mass ratio of the ceramic fiber to the polymer substrate is 4:6-6:

4.

5. The solid electrolyte membrane according to claim 1, characterized in that, The porosity of the porous composite skeleton is 40%-70%.

6. The solid electrolyte membrane according to claim 1, characterized in that, In the solid electrolyte matrix layer, the mass ratio of lithium salt, polymer matrix and inorganic filler is 3:5:2-5:4:

1.

7. The solid electrolyte membrane according to claim 1, characterized in that, The lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

8. The solid electrolyte membrane according to claim 1, characterized in that, The interface modification layer is a lithium-ion graphene layer.

9. A method for preparing a solid electrolyte membrane as described in any one of claims 1-8, characterized in that, The preparation steps include the following: (1) Preparation of porous composite skeleton: Ceramic fiber and polymer substrate are dissolved in organic solvent, ultrasonically dispersed to form spinning solution, fiber membrane is prepared by electrospinning process, and then the fiber membrane is vacuum dried to obtain porous composite skeleton layer; (2) Preparation of solid electrolyte slurry: Lithium salt, polymer matrix and inorganic filler are mixed in proportion, organic solvent is added and stirred until the raw material components are completely dissolved to form a uniform slurry; (3) Loaded solid electrolyte matrix layer: The slurry from step (2) is coated on the surface of the porous composite skeleton and then vacuum dried to solidify the slurry on the surface and inside the pores of the porous composite skeleton to form a solid electrolyte matrix layer. (4) Preparation of interface modification layer: The interface modification material is dispersed in anhydrous ethanol to form a dispersion, which is then coated on the surface of the solid electrolyte matrix layer by spraying or dipping. After vacuum drying, a composite solid electrolyte membrane is obtained.

10. A battery, characterized in that, Includes the solid electrolyte membrane according to any one of claims 1-8 or the solid electrolyte membrane prepared by the preparation method of claim 9.

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