Gradient composite solid electrolyte and preparation method and in-situ interface repair structure thereof

Abstract

The application provides a gradient composite solid-state electrolyte and a preparation method and an in-situ interface repair structure, and belongs to the field of semi-solid / solid-liquid hybrid power batteries. The gradient composite solid-state electrolyte comprises a flexible polymer layer, a composite layer and a nano-porous layer; the composite layer is located between the flexible polymer layer and the nano-porous layer, and the Young's modulus of the flexible polymer layer, the composite layer and the nano-porous layer is gradually increased in turn. The application adopts the gradient increasing design of the Young's modulus of the flexible layer, the composite layer and the nano-porous layer, so that the structure is matched with the thermal expansion coefficients of the silicon negative electrode and the high-nickel positive electrode, thereby improving the cycle stress dispersion efficiency, effectively inhibiting the expansion of the interface cracks, and finally solving the interface failure problem caused by the dynamic stress mismatch between the composite solid-state electrolyte and the electrode in the semi-solid / solid-liquid hybrid power battery.

Description

Technical Field

[0001] This application relates to the field of semi-solid / solid-liquid hybrid battery technology, and in particular to a gradient composite solid electrolyte and its preparation method, and an in-situ interface repair structure. Background Technology

[0002] To alleviate range anxiety for pure electric vehicles, the development of high-energy-density power batteries focuses on "NCM9 series high-nickel cathode + SiO2". x The " / C silicon-based anode system" has a theoretical energy density exceeding 400Wh / kg, meeting the requirements for long-range driving. However, this system faces severe interface failure problems in semi-solid / solid-liquid hybrid batteries, accounting for more than 60% of the bottlenecks in industrialization.

[0003] In the existing technology, flexible electrolyte membranes are formed by combining polymers and inorganic ceramic particles, but there are many problems, such as the inability to match the dynamic volume expansion of silicon anodes, interfacial side reactions, etc., and the lack of coordinated control of the electrode-electrolyte interface. Summary of the Invention

[0004] This application provides a gradient composite solid electrolyte and its preparation method, as well as an in-situ interface repair structure, to solve the interface failure problem of dynamic stress mismatch between the composite solid electrolyte and the electrode in the semi-solid / solid-liquid hybrid battery of "NCM9-based high-nickel cathode + SiOx / C silicon-based anode system".

[0005] In a first aspect, embodiments of this application provide a gradient composite solid electrolyte, comprising:

[0006] Flexible polymer layers, composite layers, and nanoporous layers;

[0007] The composite layer is located between the flexible polymer layer and the nanoporous layer, and the Young's modulus of the flexible polymer layer, the composite layer and the nanoporous layer increase in a gradient.

[0008] Optionally, the Young's modulus of the flexible polymer layer is 0.2 GPa to 0.4 GPa, and / or,

[0009] The composite layer has a Young's modulus of 4 GPa to 6 GPa, and / or,

[0010] The Young's modulus of the nanoporous layer is 7 GPa to 9 GPa.

[0011] Optionally, the thickness of the flexible polymer layer is 4 μm to 6 μm, and / or,

[0012] The thickness of the composite layer is 12μm to 18μm, and / or,

[0013] The thickness of the nanoporous layer is 8 μm to 12 μm.

[0014] Optionally, the flexible polymer layer includes the following performance parameters: an ionic conductivity of 0.5 × 10⁻⁶ at 25°C. -3 S / cm~1.5×10 -3 S / cm, porosity 5%–10%, thermal decomposition temperature 310℃–330℃, and / or,

[0015] The composite layer has the following performance parameters: an ionic conductivity of 1.5 × 10⁻⁶ at 25°C. -3 S / cm~2.5×10 - 3 S / cm, porosity 9%–11%, thermal decomposition temperature 330℃–450℃, and / or,

[0016] The nanoporous layer has the following performance parameters: porosity ≥60%, thermal decomposition temperature ≥1000℃.

[0017] Optionally, the material of the flexible polymer layer includes a copolymer matrix material, a reinforcing material, an elastomer, and a lithium salt; and / or,

[0018] The composite layer is made of inorganic electrolyte, polymer matrix, and lithium salt; and / or,

[0019] The material of the nanoporous layer includes nanoporous materials.

[0020] Optionally, the matrix material includes a fluoropolymer or a high-pressure-resistant polymer, and / or,

[0021] The reinforcing material includes fluorinated elastomers or hydrogenated styrene-based elastomers, and / or,

[0022] The elastomer includes hydrogenated styrene elastomers, fluorinated elastomers, or acrylate rubbers.

[0023] Optionally, the inorganic electrolyte includes one or a combination of at least two of lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, or lithium phosphorus sulfur chloride, and / or,

[0024] The polymer matrix comprises one or a combination of at least two of polyethylene oxide, polypropylene oxide, or polycaprolactone, and / or,

[0025] The lithium salt includes one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, or lithium dioxalateborate.

[0026] Optionally, the nanoporous material includes one or a combination of at least two of SiO2, Al2O3, or ZrO2.

[0027] Secondly, this application provides an in-situ interface repair structure comprising thermally responsive microcapsules, wherein the thermally responsive microcapsules are embedded in the composite layer of the gradient composite solid electrolyte described in any embodiment of the first aspect.

[0028] Optionally, the thermally responsive microcapsule comprises a shell material and a core material, and the thermal response temperature of the thermally responsive microcapsule is 60°C to 80°C.

[0029] Optionally, the shell material is one or a combination of at least two of polydopamine, thermoplastic polyurethane, or polycaprolactone.

[0030] Optionally, the thickness of the shell material is 40 nm to 60 nm.

[0031] Optionally, the core material comprises one or a combination of at least two of acrylate or polyether oligomers, wherein the molecular weight of the acrylate or polyether oligomer is 300 Da to 500 Da.

[0032] Optionally, the core material includes the following performance parameters: viscosity ≤100 mPa·s, and the Li formed after curing. + The conductivity of the conductive network at 25℃ is ≥1×10 -4 S / cm.

[0033] Optionally, the particle size of the thermally responsive microcapsules is 200 nm to 500 nm, and / or,

[0034] The mass of the thermally responsive microcapsule is 1% to 5% of the total mass of the composite layer.

[0035] Optionally, the thermally responsive microcapsules include the following performance parameters: crack filling rate ≥90%, and electrical conductivity restored to 85% of the initial value after repair.

[0036] Thirdly, this application provides a method for preparing the gradient composite solid electrolyte according to any embodiment of the first aspect, comprising:

[0037] Nanoporous layers were prepared using the sol-gel method;

[0038] A slurry for depositing a composite layer on the nanoporous layer by electrospinning is used. The slurry of the composite layer contains an inorganic electrolyte, a polymer matrix and a lithium salt.

[0039] A slurry for depositing a flexible polymer layer on the composite layer is prepared by electrospinning. The slurry for the flexible polymer layer comprises a copolymer matrix material, a reinforcing material, an elastomer, and a lithium salt.

[0040] Optionally, the mass fraction of solute in the slurry of the flexible polymer layer is 10% to 20%; and the mass fraction of solids in the slurry of the composite layer is 35% to 45%.

[0041] Optionally, thermally responsive microcapsules can be embedded in the slurry of the composite layer via ultrasonic dispersion, and / or,

[0042] An aminosilane coupling agent is introduced onto the surface of the nanoporous layer for interface modification to enhance the bonding force between the nanoporous layer and the composite layer.

[0043] The technical solutions provided in this application have the following advantages compared with the prior art:

[0044] This application provides a gradient composite solid electrolyte comprising: a flexible polymer layer composed of a copolymer matrix material, a reinforcing material, an elastomer, and a lithium salt; a composite layer composed of an inorganic electrolyte, a polymer matrix, and a lithium salt; and a nanoporous layer composed of a nanoporous material. The composite layer is located between the flexible polymer layer and the nanoporous layer, and the Young's modulus of the flexible polymer layer, the composite layer, and the nanoporous layer increases in a gradient. Firstly, the gradient increasing Young's modulus design of the flexible layer, the composite layer, and the nanoporous layer achieves matching with the thermal expansion coefficients of the silicon anode and the high-nickel cathode, thereby improving the cycle stress dispersion efficiency and suppressing the propagation of interfacial cracks. Simultaneously, the elastomer absorbs the expansion stress of the silicon anode, preventing mechanical failure and ensuring the stability of the interfacial impedance after cycling. Secondly, the synergistic effect of the inorganic electrolyte and the polymer matrix forms a continuous conductive network with high overall conductivity, supporting high-rate charge and discharge. Meanwhile, the compatibility of the fluoropolymer with the NCM9-based cathode inhibits the dissolution of transition metals; furthermore, the nanoporous material possesses high porosity and high thermal decomposition temperature, exhibiting non-combustible and non-explosive properties in needle penetration tests. Simultaneously, the excellent high-temperature stability of the lithium salt inhibits excessive SEI film growth, and its high ion transference number effectively suppresses dendrite penetration; finally, the polymer matrix wets inorganic particles, reducing grain boundary impedance and improving ion transport efficiency. Additionally, the top-layer fluoropolymer exhibits antioxidant properties, the bottom-layer SiO2 is compatible with the silicon anode, and the intermediate LLZO / PEO interface is passivated, suppressing side reactions. This design effectively solves the problem of "NCM9-based high-nickel cathode + SiO2 + silicon anode ... x The interface failure problem of dynamic stress mismatch between the composite solid electrolyte and the electrode in the " / C silicon-based anode system" semi-solid / solid-liquid hybrid battery. Attached Figure Description

[0045] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the structure of a gradient composite solid electrolyte provided in an embodiment of this application;

[0048] Figure 2 A schematic flowchart illustrating a method for preparing a gradient composite solid electrolyte provided in this application embodiment;

[0049] Figure label:

[0050] 1-Flexible polymer layer, 2-Composite layer, 3-Nanoporous layer, 4-Thermoresponsive microcapsule, 41-Shell material, 42-Core material. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0052] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1 to 6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "comprise" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0053] The gradient composite solid electrolyte of this application possesses advantages such as gradient modulus matching electrode expansion coefficient, high ionic conductivity and electrochemical compatibility, thermal stability and safety, and material synergy and functional complementarity. The in-situ interface repair structure offers advantages including precise thermal triggering and active repair mechanisms, efficient crack repair and conductivity recovery, synergistic design of materials and structure, process adaptability and industrialization potential, and dual improvements in safety and economy. The preparation method demonstrates significant advantages in the precise preparation of nanoporous layers, enhancement of interfacial bonding, optimized design of composite layers, reinforcement effect of flexible polymer layers, precise control of process parameters, and improved safety.

[0054] Figure 1 This is a schematic diagram of the structure of a gradient composite solid electrolyte provided in an embodiment of this application.

[0055] like Figure 1 As shown, this application provides a gradient composite solid electrolyte, comprising:

[0056] The flexible polymer layer 1, the composite layer 2, and the nanoporous layer 3 contain nanoporous materials;

[0057] The composite layer 2 is located between the flexible polymer layer 1 and the nanoporous layer 3, and the Young's modulus of the flexible polymer layer 1, the composite layer 2 and the nanoporous layer 3 increase in a gradient.

[0058] In some embodiments, the flexible polymer layer 1 is made of a copolymer matrix material, a reinforcing material, an elastomer, and a lithium salt; and / or,

[0059] The composite layer 2 is made of an inorganic electrolyte, a polymer matrix, and a lithium salt; and / or,

[0060] The material of the nanoporous layer 3 includes nanoporous materials.

[0061] In some embodiments, the matrix material includes a fluoropolymer or a high-pressure-resistant polymer, and / or,

[0062] The reinforcing material includes fluorinated elastomers or hydrogenated styrene-based elastomers, and / or,

[0063] The elastomer includes hydrogenated styrene elastomers, fluorinated elastomers, or acrylate rubbers.

[0064] It should be noted that fluoropolymers (such as PTFE, FEP, and PVDF) are resistant to chemical corrosion (strong acids, strong alkalis, and organic solvents), have high temperature resistance (200℃~260℃), low coefficient of friction, and excellent electrical insulation. High-pressure polymers (such as PEEK, PI, and PPS) have high strength, creep resistance, fatigue resistance, and good stability under high-pressure environments (>50MPa).

[0065] In some embodiments, the inorganic electrolyte comprises one or a combination of at least two of lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, or lithium phosphorus sulfur chloride, and / or,

[0066] The polymer matrix comprises one or a combination of at least two of polyethylene oxide, polypropylene oxide, or polycaprolactone, and / or,

[0067] The lithium salt includes one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, or lithium dioxalateborate.

[0068] Among inorganic electrolytes, lithium aluminum titanium phosphate (LATP) has an ionic conductivity of 0.1 mS / cm to 1 mS / cm (25℃) and oxidation stability > 4.5 V, making it suitable for high-voltage cathodes, but direct contact with lithium metal should be avoided. Lithium lanthanum zirconium oxide (LLZO) has a cubic phase structure with an ionic conductivity > 1 mS / cm and thermal stability > 800℃. Lithium phosphorus sulfide chloride (Li6PS5Cl) is a sulfide electrolyte with an ionic conductivity > 3 mS / cm at room temperature.

[0069] In polymer matrices, polyethylene oxide (PEO) has a low glass transition temperature (Tg) (-60℃) and strong chain segment mobility. Polypropylene oxide (PPO) has a thermal decomposition temperature >300℃ and better oxidation resistance than PEO. Polycaprolactone (PCL) is a biodegradable material with good flexibility, making it suitable for flexible composite layers.

[0070] Among lithium salts, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) exhibits high dissociation (ion pair concentration < 20%) and a thermal decomposition temperature > 300℃, making it suitable for polymer matrices. Lithium bis(fluorosulfonyl)imide (LiFSI) has an ion transference number > 0.5, significantly inhibiting lithium dendrite formation, but its hygroscopicity needs to be controlled. Lithium difluorooxalate borate (LiDFOB) demonstrates excellent high-temperature stability (decomposition temperature > 250℃), is compatible with silicon anodes, and inhibits excessive SEI film growth.

[0071] In some embodiments, the nanoporous material includes one or a combination of at least two of SiO2, Al2O3, or ZrO2.

[0072] In nanoporous materials, SiO2 has a porosity >60%, is chemically inert, adsorbs electrolyte decomposition products (such as Li2O), and suppresses interfacial side reactions. Al3O3 has a high specific surface area (>200 m²). 2 ZrO2 has a thermal decomposition temperature >1000℃, which can improve interfacial thermal stability. It also exhibits strong acid corrosion resistance, making it suitable for sulfide electrolyte systems and preventing interfacial sulfide decomposition.

[0073] In some embodiments, the fluoropolymer includes one or a combination of at least two of polyvinylidene fluoride, perfluoroethylene propylene, or polytetrafluoroethylene.

[0074] It should be noted that among fluoropolymers, polyvinylidene fluoride (PVDF) has high crystallinity and excellent mechanical strength, but it needs to be copolymerized with HFP (PVDF-HFP) to improve flexibility and ionic conductivity, making it suitable for flexible polymer layer matrices. Perfluoroethylene propylene (PFA) has excellent chemical resistance, with an oxidation potential >5.0V, and is compatible with NCM9-based cathodes, making it suitable for high-voltage applications. Polytetrafluoroethylene (PTFE) has strong chemical inertness and a thermal decomposition temperature >400℃, and is used to enhance interfacial stability.

[0075] In some embodiments, the high-pressure-resistant polymer includes one or a combination of at least two of polyarylether sulfone or polyimide.

[0076] Among high-pressure polymers, polyarylether sulfone (PES) has a glass transition temperature (Tg) > 220℃, exhibiting high temperature resistance and high mechanical strength, making it suitable for high-voltage cathode requirements. Polyimide (PI) has a thermal decomposition temperature > 500℃, excellent creep resistance, and is suitable for long-term cycling in high-temperature environments.

[0077] In some embodiments, the fluorinated elastomer includes one or a combination of at least two of polyvinylidene fluoride, hexafluoropropylene, and fluorosilicone rubber.

[0078] Among fluorinated elastomers, polyvinylidene fluoride (PVDF) combines flexibility and chemical resistance, with an elastic modulus of 50 MPa to 200 MPa, and is used to absorb the expansion stress of silicon anodes. Fluorosilicone rubber (FKM) can withstand high temperatures (decomposition temperature > 300℃) and inhibits the propagation of interfacial cracks.

[0079] In some embodiments, the hydrogenated styrene-based elastomer includes one or a combination of at least two of the following: hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, and hydrogenated styrene-butadiene-isoprene-styrene block copolymer.

[0080] Among hydrogenated styrene elastomers, SEBS (styrene-ethylene-butene-styrene) exhibits excellent aging resistance after hydrogenation due to double bond saturation, with an elastic modulus of 50 MPa to 200 MPa, making it suitable for stress buffering requirements in flexible layers. SEPS (styrene-ethylene-propylene-styrene) offers superior flexibility (Tg < -50℃), suppressing low-temperature brittleness. The multi-block structure of SEEPS balances mechanical strength and elasticity, making it suitable for complex stress environments.

[0081] This gradient composite solid electrolyte solves the dynamic stress mismatch problem of the "NCM9 + SiOx / C" system through the synergistic design of modulus and functional gradients. The parameter ranges of each layer (such as Young's modulus, thickness, and porosity) have been thermodynamically and electrochemically verified, optimizing stress buffering, ion transport, and interfacial stability, providing an innovative solution for the industrialization of high-energy-density power batteries. Specifically, the functions of each layer are as follows:

[0082] The flexible polymer layer comprises a copolymer matrix material, reinforcing materials, an elastomer, and a lithium salt. The copolymer matrix material and reinforcing materials can be copolymers. Fluoropolymers (such as PVDF-HFP) have a CF bond oxidation potential >5.0V, are compatible with NCM9-based high-voltage cathodes, and suppress transition metal dissolution. Simultaneously, solution casting can form a uniform thin film (4-6μm), reducing interfacial impedance. The reinforcing materials (fluorinated elastomers / hydrogenated styrene-based elastomers) have an elastic modulus of 50MPa–200MPa, absorbing the expansion stress of the silicon anode and preventing crack propagation. Furthermore, their thermal decomposition temperature is >300℃, ensuring high-temperature cycling stability. The lithium salt (such as LiFSI / LiTFSI) has an anion dissociation degree >80%, increasing ion mobility. The lithium salt (LiFSI) forms a continuous ion channel with the polymer matrix, and its ionic conductivity at 25℃ is 0.5 × 10⁻⁶. -3 S / cm~1.5×10 -3 S / cm, meeting basic requirements.

[0083] The composite layer comprises an inorganic electrolyte, a polymer matrix, and a lithium salt. The inorganic electrolyte (e.g., LLZO / LATP / Li6PS5Cl) forms a continuous fast ion channel with LATP. Simultaneously, its Young's modulus of 4 GPa–6 GPa matches the expansion stress of the silicon anode, preventing abrupt modulus changes. The polymer matrix (e.g., PEO / PPO / PCL) has a Tg < room temperature, wets the inorganic particles (contact angle < 30°), and reduces grain boundary resistance. The lithium salt (e.g., LiFSI / LiDFOB) synergistically enhances ion migration efficiency with the inorganic electrolyte, achieving a dissociation degree > 80%.

[0084] Composite layer: The inorganic electrolyte provides high ionic conductivity, and the polymer matrix wets the inorganic particle interface, forming a continuous conductive network. The Young's modulus of 4 GPa to 6 GPa is between that of the flexible layer and the nanoporous layer, avoiding stress concentration caused by abrupt changes in modulus, while also dispersing the residual stress caused by the expansion of the silicon anode.

[0085] The nanoporous layer comprises nanoporous materials. These materials (such as SiO2 / Al2O3 / ZrO2) have a porosity ≥60%, which disperses residual stress through capillary action, reducing the risk of interfacial cracking. Simultaneously, the rigid structure of the nanoporous materials (Young's modulus 7 GPa–9 GPa) inhibits lithium dendrite penetration. Furthermore, the thermal decomposition temperature of SiO2 is ≥1000℃, preventing thermal runaway.

[0086] Nanoporous layer: High porosity (≥60%) nanoporous materials disperse residual stress through their pore structure while blocking lithium plating / dendritic penetration from the silicon anode. Thermal decomposition temperature ≥1000℃, preventing interface collapse under thermal runaway.

[0087] Interlayer synergistic mechanism: The modulus gradient of the top layer (e.g., 0.3 GPa) → middle layer (e.g., 5 GPa) → bottom layer (e.g., 8 GPa) and the electrode thermal expansion coefficient (e.g., 1.5 × 10⁻⁶ for the positive electrode) are related to the electrode thermal expansion coefficient. -5 / ℃, negative electrode 2×10 -5 The thermal-mechanical matching is achieved at / ℃, reducing interfacial stress accumulation during cycling. Simultaneously, the expansion stress of the silicon anode is absorbed by the elastic deformation of the flexible layer; the rigid support of the intermediate layer disperses residual stress; and the porous structure of the bottom layer adsorbs residual stress. A "low-high-resistance" gradient is formed from the flexible layer (low conductivity) to the intermediate layer (high conductivity) to the bottom layer (insulating), preferentially guiding ions through the fast channels of the intermediate layer and reducing overall impedance. Furthermore, the dissociation degree of the LiFSI lithium salt in the intermediate layer is >80%, significantly increasing the ion transport number. In addition, the PEO matrix (Tg < room temperature) in the intermediate layer wets inorganic particles (such as LLZO), reducing grain boundary impedance (contact angle <30°) and improving ion transport efficiency. Meanwhile, the oxidation resistance (>5.0V) of the top-layer fluoropolymer protects the positive electrode interface, and the EIS shows stable interfacial impedance after cycling; the bottom SiO2 has no side reactions with the SiOx / C anode, inhibiting excessive SEI film growth.

[0088] In some embodiments, the Young's modulus of the flexible polymer layer is 0.2 GPa to 0.4 GPa, and / or,

[0089] The composite layer has a Young's modulus of 4 GPa to 6 GPa, and / or,

[0090] The Young's modulus of the nanoporous layer is 7 GPa to 9 GPa.

[0091] It should be noted that Young's modulus is a physical quantity that characterizes a material's tensile or compressive strength within its elastic limit, and it depends solely on the material's inherent physical properties. The magnitude of Young's modulus indicates the material's rigidity; the larger the Young's modulus, the less prone it is to deformation.

[0092] The Young's modulus of the flexible polymer layer is limited to 0.2 GPa to 0.4 GPa. This modulus range is lower than the expansion stress of the silicon anode, allowing it to absorb more than 50% of the dynamic stress through elastic deformation, thus preventing crack propagation. It also balances the requirements for flexibility and mechanical support. The Young's modulus of the composite layer lies between that of the flexible layer and the rigid nanoporous layer, avoiding stress concentration caused by abrupt modulus changes. The modulus of inorganic electrolytes (such as LLZO) is typically 100 GPa to 200 GPa, but the overall modulus decreases after compositing with polymers, matching the expansion characteristics of the silicon anode. The high modulus of the nanoporous layer provides rigid support, preventing structural collapse caused by the expansion of the silicon anode. The modulus of nanoporous materials (such as SiO2) can reach 70 GPa, but a porosity ≥60% will reduce the actual modulus to 7 GPa to 9 GPa, balancing stress absorption and rigidity requirements. For example, the Young's modulus of the flexible polymer layer can be 0.2 GPa, 0.25 GPa, 0.3 GPa, 0.35 GPa, 0.4 GPa, etc., the Young's modulus of the composite layer can be 4 GPa, 4.5 GPa, 5 GPa, 5.5 GPa, 6 GPa, etc., and the Young's modulus of the nanoporous layer can be 7 GPa, 7.5 GPa, 8 GPa, 8.5 GPa, 9 GPa, etc.

[0093] Thus, the flexible polymer layer absorbs the expansion stress of the silicon anode, the composite layer disperses the residual stress, and the nanoporous layer provides rigid support, in conjunction with the positive electrode (e.g., 1.5 × 10⁻⁶). -5 / ℃) and negative electrode (e.g., 2×10) -5 ( / ℃) Thermal expansion coefficient matching.

[0094] In some embodiments, the thickness of the flexible polymer layer is 4 μm to 6 μm, and / or,

[0095] The thickness of the composite layer is 12μm to 18μm, and / or,

[0096] The thickness of the nanoporous layer is 8 μm to 12 μm.

[0097] The thickness of the flexible polymer layer is limited to 4μm to 6μm. A thinner layer reduces the ion transport path length, and a porosity of 5% to 10% balances ionic conductivity and mechanical strength. If the flexible polymer layer is too thick (>6μm), it increases internal resistance; if it is too thin (<4μm), it is prone to stress cracking. For example, the thickness of the flexible polymer layer can be 4μm, 4.5μm, 5μm, 5.5μm, 6μm, etc., and the porosity can be 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0098] The thickness of the composite layer is limited to 12 μm to 18 μm. A thicker layer ensures a high loading of the inorganic electrolyte and maintains high ionic conductivity. The porosity is limited to 9% to 11%, which optimizes the inorganic / polymer interface contact and reduces grain boundary resistance. For example, the thickness of the composite layer can be 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, etc., and the porosity can be 9%, 9.5%, 10%, 10.5%, 11%, etc.

[0099] The thickness of the nanoporous layer is limited to 8 μm to 12 μm, with a porosity ≥60%. High porosity allows for the adsorption of residual stress through capillary action; for every 10% increase in porosity, the stress dispersion efficiency improves by 15%. Simultaneously, the thickness design reduces the volume fraction, avoiding excessively long ion transport paths. For example, the thickness of the nanoporous layer can be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc., and the porosity can be 60%, 61%, 62%, 63%, 64%, 65%, etc.

[0100] In some embodiments, the flexible polymer layer includes the following performance parameters: an ionic conductivity of 0.5 × 10⁻⁶ at 25°C. -3 S / cm~1.5×10 -3 S / cm, porosity 5%–10%, thermal decomposition temperature 310℃–330℃, and / or,

[0101] The composite layer has the following performance parameters: an ionic conductivity of 1.5 × 10⁻⁶ at 25°C. -3 S / cm~2.5×10 - 3 S / cm, porosity 9%–11%, thermal decomposition temperature 330℃–450℃, and / or,

[0102] The nanoporous layer has the following performance parameters: porosity ≥60%, thermal decomposition temperature ≥1000℃.

[0103] It should be noted that ionic conductivity represents a material's ability to conduct ions under a unit electric field strength, and its unit is Siemens per centimeter (S / cm). Its value depends on the concentration of mobile ions in the material, their migration rate, and the connectivity of carrier migration paths.

[0104] Porosity refers to the percentage of pore volume in a material to its total volume, reflecting whether the material is dense or has an open structure.

[0105] Thermal decomposition temperature is the temperature at which a material begins to decompose irreversibly due to the breaking of chemical bonds during heating, and it is usually determined by thermogravimetric analysis.

[0106] The thermal decomposition temperature of the flexible polymer layer is limited to 310℃~330℃, which matches the operating temperature of NCM9-based cathodes and avoids high-temperature decomposition. Fluoropolymers (such as PVDF-HFP) have higher thermal stability than ordinary polymers (such as PEO). The thermal decomposition temperature of the composite layer is limited to >400℃, and the thermal stability of the inorganic electrolyte (such as LLZO, LATP) is >800℃, resulting in improved overall temperature resistance after composite formation and preventing high-temperature interface failure. The thermal decomposition temperature of the nanoporous layer is limited to ≥1000℃, and materials such as SiO2 and Al2O3 exhibit excellent high-temperature resistance, preventing interface collapse under thermal runaway. For example, the thermal decomposition temperature of the flexible polymer layer can be 310℃, 315℃, 320℃, 325℃, 330℃, etc., the thermal decomposition temperature of the composite layer can be 330℃, 340℃, 350℃, 380℃, 400℃, 420℃, 450℃, etc., and the thermal decomposition temperature of the nanoporous layer can be 1000℃, 1020℃, 1050℃, 1080℃, 1100℃, 1150℃, etc.

[0107] The high dissociation degree of the LiFSI composite layer enhances the ion transference number, while the adsorption of byproducts by the nanoporous layer reduces interfacial side reactions, forming a "low-high-resistance" gradient conduction pathway. Simultaneously, the fluoropolymer in the flexible polymer layer provides antioxidant protection, the SiO2 nanoporous layer is compatible with the silicon anode, and the LLZO / PEO composite layer wets the interface, forming a chemically stable closed loop. For example, the ionic conductivity of the flexible polymer layer at 25°C can be 0.5 × 10⁻⁶. -3 S / cm, 0.7×10 -3 S / cm, 0.9×10 -3 S / cm, 1.1×10 - 3 S / cm, 1.3×10 -3 S / cm, 1.5×10 -3 The ionic conductivity of the composite layer at 25℃ is 1.5 × 10⁻⁶ S / cm. -3 S / cm, 1.8×10 -3 S / cm, 2.0×10 -3 S / cm, 2.2×10 -3 S / cm, 2.4×10 -3 S / cm, 2.5×10 -3 S / cm, etc.

[0108] Therefore, the gradient composite solid electrolyte provided in this application has the following advantages:

[0109] (1) Dynamic stress adaptation and interface stability: By increasing the Young's modulus gradient of flexible layers (e.g., 0.2 GPa to 0.4 GPa), composite layers (e.g., 4 GPa to 6 GPa), and nanoporous layers (e.g., 7 GPa to 9 GPa), the silicon anode (e.g., 2 × 10⁻⁶ GPa) is matched with the interface stability.-5 / ℃) and high-nickel cathode (e.g., 1.5×10 -5 The coefficient of thermal expansion (°C) is improved, and the cyclic stress dispersion efficiency is increased by more than 70%, suppressing the propagation of interfacial cracks. At the same time, elastomers such as SEBS / FKM absorb the expansion stress of the silicon anode, preventing mechanical failure, and the interfacial impedance remains stable after cycling.

[0110] (2) High ionic conductivity and electrochemical compatibility: The LLZO / LATP inorganic electrolyte (ionic conductivity > 1 mS / cm) and the PEO matrix (Tg < room temperature) synergistically form a continuous conduction network, with an overall conductivity of 1.5–2.5 × 10⁻³ S / cm, supporting high-rate charge and discharge. Simultaneously, the oxidation potential of the fluoropolymer (such as PVDF-HFP) is > 5.0 V, making it compatible with the NCM9-based cathode and inhibiting transition metal dissolution.

[0111] (3) Thermal stability and safety: SiO2 / Al2O3 porosity ≥60%, thermal decomposition temperature ≥1000℃, UL9540A certified, does not ignite or explode during needle penetration test. At the same time, LiDFOB has excellent high-temperature stability (decomposition temperature >250℃), inhibiting excessive growth of SEI film; LiFSI ion transference number >0.5, inhibiting dendrite penetration.

[0112] (4) Material synergy and functional complementarity: The PEO matrix wets the LLZO particles (contact angle <30°), reducing the grain boundary impedance to 0.25eV and improving ion transport efficiency. At the same time, the top layer of fluoropolymer is anti-oxidant, the bottom layer of SiO2 is compatible with the silicon anode, and the middle layer of LLZO / PEO interface is passivated to suppress side reactions.

[0113] Based on a general inventive concept, this application provides an in-situ interface repair structure comprising thermally responsive microcapsules, wherein the thermally responsive microcapsules are embedded in the composite layer of the gradient composite solid electrolyte described in any of the above embodiments.

[0114] It should be noted that thermally responsive microcapsules are core-shell structured materials with temperature-triggered release capabilities, consisting of a shell material and a core material. Their core function is: when the internal temperature of the battery reaches a preset threshold, the shell ruptures, releasing the core material, which then fills the interface cracks and solidifies to form Li. + Conductive network enables in-situ self-healing.

[0115] In some embodiments, the thermally responsive microcapsule comprises a shell material and a core material, and the thermal response temperature of the thermally responsive microcapsule is 60°C to 80°C.

[0116] The thermal response temperature is limited to 60℃~80℃. This range matches the early warning temperatures of battery thermal runaway (such as localized overheating or micro-short circuits), occurring earlier than the critical thermal runaway temperature (>100℃), thus enabling active repair. Simultaneously, it is higher than the normal operating temperature of the battery (<60℃) to prevent premature rupture of the microcapsules during normal cycling. For example, the thermal response temperature of the thermally responsive microcapsules can be 60℃, 65℃, 70℃, 75℃, 80℃, etc.

[0117] In some embodiments, the shell material is one or a combination of at least two of polydopamine, thermoplastic polyurethane, or polycaprolactone.

[0118] In some embodiments, the thickness of the shell material is 40 nm to 60 nm.

[0119] The shell material is polydopamine / TPU / PCL. Polydopamine (PDA) has high chemical stability, TPU has an adjustable Tg (60℃~80℃), and PCL (Tg≈60℃) provides a low-temperature response option. The shell material thickness is limited to 40nm~60nm to provide mechanical protection, and this thickness balances structural strength and thermal conductivity. For example, the shell material thickness can be 40nm, 45nm, 50nm, 55nm, 60nm, etc.

[0120] In some embodiments, the core material comprises one or a combination of at least two of acrylate or polyether oligomers, wherein the molecular weight of the acrylate or the polyether oligomer is 300 Da to 500 Da.

[0121] In some embodiments, the acrylates include one or a combination of at least two of PEGDA or polyethylene glycol methyl ether acrylate, wherein the polyether oligomer is polyethylene glycol diglycidyl ether.

[0122] In some embodiments, the core material includes the following performance parameters: viscosity ≤100 mPa·s, and the Li formed after curing. + The conductivity of the conductive network at 25℃ is ≥1×10 -4 S / cm.

[0123] The molecular weights of acrylates (such as PEGDA) and polyether oligomers (such as PEGDGE) are controlled between 300 and 500 Da, ensuring a viscosity ≤100 mPa·s. This guarantees that the core material can flow rapidly and fill cracks after microcapsule rupture. Simultaneously, acrylates form a three-dimensional cross-linked network under free radical initiation, while polyethers undergo ring-opening polymerization and curing via epoxy groups. After doping with lithium salts (such as LiTFSI), Li is formed. +The transmission channel improves conductivity at 25°C. Furthermore, acrylate and polyether materials exhibit no side reactions with inorganic electrolytes (such as LLZO) and polymer matrices (PEO), and the cured network is insoluble in the electrolyte, preventing secondary decomposition.

[0124] The core material is limited to a molecular weight of 300 Da to 500 Da and a viscosity of ≤100 mPa·s. Lower molecular weight reduces viscosity to ensure crack filling speed. Acrylic esters (such as PEGDA) form a cross-linked network after curing, and Li... + Electrical conductivity ≥1×10 -4 The S / cm (25℃) value is approximately 6.7% of the initial value of the composite layer (1.5×10⁻³ S / cm). For example, the molecular weight of the core material can be 300 Da, 350 Da, 380 Da, 400 Da, 450 Da, 480 Da, 500 Da, etc., and the viscosity can be 50 mPa·s, 60 mPa·s, 700 mPa·s, 800 mPa·s, 900 mPa·s, 100 mPa·s, etc.

[0125] In some embodiments, the particle size of the thermally responsive microcapsules is 200 nm to 500 nm, and / or,

[0126] The mass of the thermally responsive microcapsule is 1% to 5% of the total mass of the composite layer.

[0127] The particle size of the microcapsules is limited to 200–500 nm to ensure uniform distribution within the composite layer. The mass of the thermally responsive microcapsules is limited to 1%–5% of the total mass of the composite layer, balancing repair needs with electrolyte performance. For example, the particle size of the thermally responsive microcapsules can be 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc., and the mass of the thermally responsive microcapsules can be 1%, 2%, 3%, 4%, 5%, etc., of the total mass of the composite layer.

[0128] In some embodiments, the thermally responsive microcapsules include the following performance parameters: crack filling rate ≥90%, and electrical conductivity restored to 85% of the initial value after repair.

[0129] In this embodiment, the in-situ interface repair structure, through precise parameter design of thermally responsive microcapsules, achieves a thermal triggering mechanism at 60℃–80℃ before thermal runaway, eliminating the need for external circuit control. Simultaneously, the low-viscosity core material rapidly fills the cracks, and after curing, the conductivity recovers to 85%, extending battery life. Furthermore, the microcapsules synergize with the gradient composite solid electrolyte (LLZO / PEO), resulting in an interface impedance increase of less than 10% after repair. The microcapsules can be embedded into the composite layer via a solution mixing process, adapting to existing production lines. This design provides a material-level self-healing solution for interface failure problems in high-nickel silicon-based batteries, combining safety and economy.

[0130] Therefore, the in-situ interface repair structure provided in this application has the following advantages:

[0131] (1) Precise thermal triggering and active repair mechanism: The thermal response temperature is set at 60℃~80℃ to match the early signs of thermal runaway in the battery (such as local overheating or micro-short circuit), earlier than the critical temperature for thermal runaway (>100℃), to achieve active early warning and repair, and avoid the risk of explosion. Pure material response mechanism, no external circuit control required, reducing system complexity.

[0132] (2) High-efficiency crack repair and conductivity restoration: With a core material viscosity ≤100 mPa·s (e.g., PEGDA viscosity ≈ 50 mPa·s), it can fill 10 μm-level cracks within 5 seconds. After curing, Li... + Electrical conductivity ≥1×10 -4 S / cm, the overall conductivity of the composite layer recovered to 85% of the initial value.

[0133] (3) Co-design of materials and structure: Polydopamine (PDA) has high chemical stability and a thickness of 40-60 nm, balancing mechanical strength and thermal response efficiency. The Tg of TPU / PCL is adjustable (60-80℃) to meet the needs of different thermal runaway scenarios. Acrylic ester / polyether oligomers have a molecular weight of 300-500 Da, low viscosity to ensure flowability, and are compatible with LLZO / PEO electrolytes after curing.

[0134] (4) Process adaptability and industrialization potential: The microcapsule particle size is 200-500 nm and the mass ratio is 1%-5%, which ensures uniform dispersion and does not block ion channels. It can be embedded into the composite layer through solution mixing process, which is compatible with the existing solid-state battery manufacturing process.

[0135] (5) Enhanced safety and economy: The increased interfacial impedance after repair is <10%, and the nanoporous layer with a thermal decomposition temperature ≥1000℃ provides secondary protection. Microcapsule materials (such as PEGDA and TPU) are low in cost, with an addition amount of only 1% to 5%, resulting in an overall cost increase of <3%.

[0136] Figure 2 This is a schematic flowchart illustrating a method for preparing a gradient composite solid electrolyte according to an embodiment of this application.

[0137] like Figure 2 As shown, this application provides a method for preparing the gradient composite solid electrolyte according to any of the above embodiments, comprising:

[0138] S1. Nanoporous layers were prepared by the sol-gel method;

[0139] It should be noted that the sol-gel method is a technique for preparing nanoporous materials by hydrolyzing and condensing a liquid precursor (such as a metal alkoxide) to form a gel, followed by drying and sintering. Its advantages lie in the uniform and controllable composition, making it suitable for the preparation of oxide films and porous structures.

[0140] The sol-gel method in this application involves hydrolysis and condensation reactions to form a three-dimensional network structure, ultimately generating a nanoporous layer. This layer possesses a high specific surface area and uniform pore size, which can improve ion transport efficiency and provide structural support for subsequent layers.

[0141] Specifically, step S1 may include:

[0142] S101. Using tetraethyl orthosilicate as a precursor, silica sol is generated by hydrolysis under acidic conditions.

[0143] S102. The silica sol is coated on the substrate to form a wet gel film, and aged at 60°C for 12h to 24h to carry out a polycondensation reaction. Then, it is heat-treated at 120°C to form a porous structure layer with a pore size of 10nm to 20nm.

[0144] S103. An aminosilane coupling agent (KH-550) is introduced onto the surface of the porous structure layer to form hydrogen bonds with the ether oxygen bond of the composite layer, thereby obtaining a nanoporous layer.

[0145] It should be noted that aminosilane coupling agents are amino-containing silane compounds (such as KH550), which improve the interfacial bonding between inorganic materials and organic polymers through chemical bonding.

[0146] The precursor is hydrolyzed in an acidic environment, which can control the hydrolysis rate and generate a uniform silica sol, providing a basis for subsequent polycondensation reactions. The aging treatment enhances the strength of the gel network and reduces cracks caused by drying stress. At the same time, it forms a nanoporous structure with uniform pore size distribution through self-assembly. The heat treatment temperature is 120℃, which can stabilize the pore size through the dehydroxylation reaction (Si-OH→Si-O-Si), thereby improving the thermal stability and mechanical strength of the porous layer. The introduction of the coupling agent modifies the surface hydroxyl groups (Si-OH) to amino groups (—NH2) through chemical bonding. The amino groups form hydrogen bonds with the intermediate layer (such as polymer P containing ether oxygen bonds), which improves the interfacial chemical compatibility.

[0147] S2. A slurry for depositing a composite layer on the nanoporous layer by electrospinning, wherein the slurry of the composite layer contains an inorganic electrolyte, a polymer matrix and a lithium salt.

[0148] It should be noted that electrospinning is a technique that uses a high-voltage electric field to stretch polymer solutions or melts into nanofibers. In electrolyte preparation, it can form a high-porosity fiber network, enhancing ion transport pathways and mechanical strength.

[0149] Following electrospinning, the composite layer slurry is directly deposited onto the surface of the modified nanoporous layer, allowing the polymer matrix molecular chains to penetrate into the pores of the nanoporous layer (SEM images show a seamless interface). By depositing the composite layer on the nanoporous layer via electrospinning, the high ionic conductivity of the inorganic electrolyte and the flexibility of the polymer matrix are combined to form an intermediate layer possessing both ion transport and mechanical strength. Lithium salts further optimize ion migration capabilities.

[0150] In some embodiments, the slurry of the composite layer further includes a solvent, which includes one or a combination of methanol or ethanol.

[0151] In some embodiments, the composite layer slurry, after electrospinning, needs to be vacuum dried at 80°C for 12 hours to completely evaporate the low-boiling-point solvent and avoid contact with the silicon anode. Simultaneously, the selected solvent is above the operating potential of the silicon anode, preventing reduction reactions from occurring on the anode surface. Furthermore, the lithium salt is stable in alcohol solvents, and after drying, the lithium salt forms a composite phase with the polymer matrix / inorganic electrolyte, without releasing free solvent molecules. Therefore, it is indicated that the solvent in the lithium salt solution of the composite layer does not affect the silicon anode.

[0152] S3. A slurry for depositing a flexible polymer layer on the composite layer by electrospinning, wherein the slurry for the flexible polymer layer comprises a copolymer matrix material, a reinforcing material, an elastomer, and a lithium salt.

[0153] A flexible polymer layer, primarily composed of copolymer matrix and elastomer, is deposited via electrospinning to enhance the mechanical toughness and interfacial stability of the electrolyte and suppress lithium dendrite penetration. The reinforcing material can construct a porous structure, increasing the contact area between the electrolyte and the electrode.

[0154] In some embodiments, thermally responsive microcapsules are embedded in the slurry of the composite layer by ultrasonic dispersion, and / or,

[0155] An aminosilane coupling agent is introduced onto the surface of the nanoporous layer for interface modification to enhance the bonding force between the nanoporous layer and the composite layer.

[0156] By embedding thermally responsive microcapsules into the composite layer using ultrasonic dispersion, the microcapsules can release flame-retardant or self-healing substances under abnormal temperature conditions, improving battery safety. Introducing an aminosilane coupling agent onto the surface of the nanoporous layer enhances interfacial bonding through chemical bonding (such as the reaction of -NH2 with hydroxyl groups on the inorganic layer surface), reducing the risk of delamination.

[0157] In some embodiments, the mass fraction of solute in the slurry of the flexible polymer layer is 10% to 20%; and the mass fraction of solids in the slurry of the composite layer is 35% to 45%.

[0158] Limiting the solid content of the slurry for the composite layer to 35%–45% by mass ensures moderate viscosity, facilitating the formation of a continuous fiber structure, while reducing drying shrinkage and preventing cracking. Limiting the solute content of the slurry for the flexible polymer layer to 10%–20% promotes the formation of an ultrafine fiber network, reduces porosity, and enhances flexibility; it also avoids spinning blockage caused by high concentrations. For example, the solute content in the slurry for the flexible polymer layer can be 10%, 12%, 15%, 17%, 19%, 20%, etc., and the solid content of the slurry for the composite layer can be 35%, 37%, 39%, 40%, 42%, 44%, 45%, etc.

[0159] In some embodiments, the parameters of the electrospinning method are: voltage 18kV, receiving distance 10cm, flow rate 0.8mL / h, temperature 25℃, and humidity <30%.

[0160] The electrospinning voltage is limited to 18kV. A high-voltage electric field drives the polymer jet to stretch, forming nanoscale fibers. Excessive voltage may cause fiber breakage, while insufficient voltage results in uneven fiber diameter. A receiving distance of 10cm is limited to control solvent evaporation and fiber stretching during jet flight. Too short a distance can lead to fiber adhesion, while too long a distance reduces deposition efficiency. A flow rate of 0.8mL / h ensures a stable slurry supply, preventing droplet ejection or fiber breakage, and matches the electric field stretching rate. The electrospinning temperature is limited to 25℃, with humidity <30%. A moderate solvent evaporation rate at room temperature prevents excessively rapid drying of the fiber surface, which could lead to structural defects.

[0161] The product prepared by the method of preparing gradient composite solid electrolyte is the gradient composite solid electrolyte described above. The chemical composition and microstructure of the gradient composite solid electrolyte prepared by the method of preparing gradient composite solid electrolyte can be referred to the above embodiments. Since the method of preparing gradient composite solid electrolyte adopts some or all of the technical solutions of the gradient composite solid electrolyte embodiments, it has at least all the beneficial effects brought about by the technical solutions of the gradient composite solid electrolyte embodiments, which will not be elaborated here.

[0162] Therefore, the method for preparing a gradient composite solid electrolyte provided in this application has the following advantages:

[0163] (1) Precise preparation of nanoporous layers: A sol-gel method was used to form a three-dimensional network structure through hydrolysis and condensation reactions, which enabled precise control of the pore size (10nm~20nm) and pore distribution of the nanoporous layers, thereby providing high specific surface area and uniform ion transport channels. At the same time, the hydrolysis rate of the precursor under acidic conditions was controllable, which was conducive to the formation of uniform silica sol, laying the foundation for subsequent polycondensation reactions and self-assembly processes. In addition, aging and heat treatment steps further enhanced the strength of the gel network, reduced cracks caused by drying stress, stabilized the pore size, and improved the thermal stability and mechanical strength of the porous layer.

[0164] (2) Significantly enhanced interfacial bonding: Introducing an aminosilane coupling agent (such as KH550) onto the surface of the nanoporous layer, and modifying the surface hydroxyl groups to amino groups through chemical bonding, forms hydrogen bonds with the ether oxygen bonds of the composite layer, significantly improving the interfacial chemical compatibility and bonding strength. This interfacial modification not only enhances the bonding between the nanoporous layer and the composite layer, but also reduces the risk of delamination, and improves the stability and reliability of the overall structure.

[0165] (3) Optimized design of the composite layer: A composite layer slurry was deposited on the nanoporous layer using electrospinning to form a high-porosity fiber network, enhancing ion transport pathways and mechanical strength. Simultaneously, the composite layer slurry contains inorganic electrolyte, polymer matrix, and lithium salt, combining the high ionic conductivity of the inorganic electrolyte with the flexibility of the polymer matrix to form an intermediate layer that possesses both ion transport and mechanical strength. Furthermore, the selection of solvent and optimization of drying conditions ensured the compatibility of the composite layer with the silicon anode, avoiding the influence of free solvent molecules on the anode.

[0166] (4) Reinforcing effect of flexible polymer layer: The flexible polymer layer, mainly composed of copolymer matrix and elastomer, was deposited by electrospinning, which significantly enhanced the mechanical toughness and interfacial stability of the electrolyte and effectively suppressed the penetration of lithium dendrites. At the same time, the introduction of reinforcing materials constructed a porous structure, increased the contact area between the electrolyte and the electrode, and further optimized the ion transport performance.

[0167] (5) Precise control of process parameters: The parameters of electrospinning (voltage, receiving distance, flow rate, temperature) are precisely set to ensure the uniformity and continuity of the fibers and avoid the generation of structural defects. At the same time, the limitation of sizing concentration ensures the stability of the spinning process and the quality of the fibers, while optimizing the flexibility and mechanical properties of the electrolyte.

[0168] (6) Enhanced safety: By embedding thermally responsive microcapsules into the composite layer through ultrasonic dispersion, the microcapsules can release flame-retardant or self-healing substances when the temperature is abnormal, which effectively improves the safety of the battery.

[0169] In summary, this gradient composite solid electrolyte preparation method demonstrates significant advantages in terms of precise preparation of nanoporous layers, improvement of interfacial bonding, optimized design of composite layers, enhancement of flexible polymer layers, precise control of process parameters, and improved safety, providing strong support for the research and development of high-performance solid-state batteries.

[0170] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0171] Examples 1 through 8 provide gradient composite solid electrolytes with different parameters and compositions, and their preparation methods, as detailed below for specific parameters and performance. Examples 6 and 7 also involve specific preparation methods for thermally responsive microcapsules.

[0172] Example 1

[0173] This embodiment provides a gradient composite solid electrolyte, comprising:

[0174] The flexible polymer layer comprises a copolymer matrix material, reinforcing materials, an elastomer, and a lithium salt;

[0175] The copolymer matrix material and the reinforcing material are copolymers, and the mass ratio of the copolymer matrix material and the reinforcing material copolymer, the elastomer and the lithium salt is 85:10:5.

[0176] The copolymer matrix material and the reinforcing material are copolymers of polyvinylidene fluoride and hexafluoropropylene (PVDF-HFP, CAS No. 9011-17-0, chemical formula (-CH2CF2-)x[-CF2CF(CF3)-]). y Elastomer: Acrylic rubber (ACM, CAS No. 67254-76-6), Lithium salt: Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI);

[0177] Performance parameters: Young's modulus: 0.3 GPa, thickness: 5 μm, ionic conductivity (25℃): 1.2 × 10⁻⁶ -3 S / cm, porosity: 8%, thermal decomposition temperature: 320℃.

[0178] The composite layer comprises an inorganic electrolyte, a polymer matrix, and a lithium salt;

[0179] The mass ratio of inorganic electrolyte, polymer matrix and lithium salt is 85:10:5.

[0180] Inorganic electrolyte: lithium aluminum titanium phosphate (LATP), polymer matrix: polyethylene oxide (PEO, CAS No. 68441-17-8), lithium salt: LiTFSI;

[0181] Performance parameters: Young's modulus: 5 GPa, thickness: 15 μm, ionic conductivity (25℃): 2.0 × 10⁻⁶ -3 S / cm, porosity: 10%, thermal decomposition temperature: 380℃.

[0182] Nanoporous layer, containing nanoporous materials;

[0183] Among them, the nanoporous material is silicon dioxide;

[0184] Performance parameters: Young's modulus: 8 GPa, thickness: 10 μm, porosity: 65%, thermal decomposition temperature: 1000℃.

[0185] The composite layer is located between the flexible polymer layer and the nanoporous layer.

[0186] Based on the above-described gradient composite solid electrolyte, this embodiment also provides a method for preparing a gradient composite solid electrolyte, which may include the following steps:

[0187] S11. Using tetraethyl orthosilicate as a precursor, silica sol is generated by hydrolysis under acidic conditions; the silica sol is coated onto a substrate to form a wet gel film, and aged at 60°C for 12 hours to carry out a polycondensation reaction, followed by heat treatment at 120°C to form a porous structure layer with a pore size of 10nm to 20nm; an aminosilane coupling agent is introduced onto the surface of the porous structure layer to form hydrogen bonds with the ether oxygen bonds of the composite layer to obtain a nanoporous layer;

[0188] S2. A slurry for depositing a composite layer on the nanoporous layer by electrospinning, wherein the slurry of the composite layer contains an inorganic electrolyte, a polymer matrix and a lithium salt.

[0189] The solid content of the slurry in the composite layer is 40%.

[0190] S3. A slurry for depositing a flexible polymer layer on the composite layer by electrospinning, wherein the slurry for the flexible polymer layer comprises a copolymer matrix material, a reinforcing material, an elastomer, and a lithium salt.

[0191] The slurry concentration of the flexible polymer layer is 15%.

[0192] The parameters for the electrospinning method are: voltage 18kV, receiving distance 10cm, flow rate 0.8mL / h, temperature 25℃, and humidity <30%.

[0193] Example 2

[0194] Compared to Example 1, the differences in this example are as follows, while the rest are the same:

[0195] The inorganic electrolyte, polymer matrix, and lithium salt in the composite layer have a mass ratio of 90:5:5, which increases the conductivity to 3×10⁻⁶. -3 S / cm (25℃).

[0196] The nanoporous layer has a porosity of 85% and a thickness of 8 μm.

[0197] Example 3

[0198] Compared to Example 1, the differences in this example are as follows, while the rest are the same:

[0199] The copolymer matrix material and the reinforcing material are copolymers: PVDF-HFP, elastomer: hydrogenated styrene-ethylene-propylene block copolymer (SEP), and lithium salt: LiFSI;

[0200] Inorganic electrolyte: LLZO cubic phase; polymer matrix: polypropylene oxide (PPO); lithium salt: LiDFOB.

[0201] The nanoporous material is silicon dioxide.

[0202] Example 4

[0203] Compared to Example 1, the differences in this example are as follows, while the rest are the same:

[0204] Copolymer matrix material and reinforcing material copolymer: perfluoroethylene propylene (FEP), elastomer: fluorosilicone rubber (FVMQ), lithium salt: LiBOB;

[0205] Inorganic electrolyte: sulfide-germanium ore type Li6PS5Cl, polymer matrix: polycaprolactone PCL, lithium salt: LiTFSI;

[0206] The nanoporous material is silicon dioxide.

[0207] Example 5

[0208] Compared to Example 1, the differences in this example are as follows, while the rest are the same:

[0209] Copolymer matrix material and reinforcing material copolymer: polyimide PI, elastomer: acrylate rubber ACM, lithium salt: LiTFSI;

[0210] Inorganic electrolyte: LATP, polymer matrix: PEO, lithium salt: LiFSI;

[0211] The nanoporous material is silicon dioxide.

[0212] Example 6

[0213] Compared to Example 1, the differences in this example are as follows, while the rest are the same:

[0214] Thermally responsive microcapsules were embedded in the composite layer of the gradient composite solid electrolyte described in Example 1. During embedding, the microcapsules were mixed with the composite layer slurry and then ultrasonically dispersed (200W, 40kHz, 20min).

[0215] The thermally responsive microcapsule comprises a shell material and a core material, and the thermal response temperature of the thermally responsive microcapsule is 60-70°C.

[0216] The shell material is polydopamine.

[0217] The shell material has an average thickness of 50 nm.

[0218] The core material is polyethylene glycol diacrylate (CAS No. 26570-48-9).

[0219] The core material includes the following performance parameters: viscosity of 80 mPa·s, and Li after curing. + The conductivity of the conductive network at 25℃ is 1.05 × 10⁻⁶. -4 S / cm.

[0220] The thermally responsive microcapsules have an average particle size of 300 nm, and / or,

[0221] The mass of the thermally responsive microcapsule is 3% of the total mass of the composite layer.

[0222] This embodiment also provides a specific method for preparing thermally responsive microcapsules, including the following steps:

[0223] Polyethylene glycol diacrylate (PEGDA), 2-hydroxy-2-methylphenylacetone (HMPP, 1 wt%), and deionized water were mixed in proportion and ultrasonically dispersed until completely dissolved. The concentration was adjusted to 20% (w / v) to obtain the core material solution. Dopamine was dissolved in Tris buffer to a final concentration of 2 mg / mL to obtain the core material solution.

[0224] Using a microfluidic chip, the core material solution (PEGDA) is encapsulated by the shell precursor solution (dopamine) to form a double emulsion droplet (W / O / W structure), which is then dispersed in the oil phase. By adjusting the flow rate ratio (core material: shell: oil phase = 1:4:20), the average droplet size is controlled at 300 nm, resulting in an emulsion.

[0225] The emulsion was transferred to a constant temperature reactor (25°C) and stirred continuously (200 rpm) for 12 hours to allow dopamine to oxidize and self-polymerize at the droplet interface, forming a homogeneous shell with an average thickness of nm.

[0226] Expose the emulsion to a UV light source (wavelength 365nm, intensity 10mW / cm²). 2 Irradiation for 15 min initiated PEGDA crosslinking and curing. Hexane (twice the volume of the oil phase) was added, and the microcapsules were separated by centrifugation (5000 rpm, 10 min). The microcapsules were washed three times alternately with ethanol and deionized water to remove residual oil phase and unreacted monomers. The microcapsule powder was obtained by freeze-drying (-50℃, 24 h).

[0227] Example 7

[0228] Compared to Example 6, the differences in this example are as follows, while the rest are the same:

[0229] The shell material is thermoplastic polyurethane (CAS No. 1211-14-9).

[0230] The core material is polyethylene glycol methyl ether acrylate (CAS No. 32171-39-4), and its electrical conductivity increases to 1.2×10-4 S / cm (25℃) after curing.

[0231] The thermal response temperature of the microcapsules was adjusted to 70–80℃.

[0232] Example 8

[0233] Compared to Example 6, the differences in this example are as follows, while the rest are the same:

[0234] The thermally responsive microcapsules have a particle size of 450 nm.

[0235] The mass of the thermally responsive microcapsule is 5% of the total mass of the composite layer.

[0236] Comparative Examples 1 to 4 were modified from Example 1, lacking the flexible polymer layer, composite layer, nanoporous layer, or using a gradient-free structure. Their performance was reduced compared to the Example, as detailed in the following data.

[0237] Comparative Example 1

[0238] This comparative example is based on Example 1, with the following specific adjustments:

[0239] A gradient composite solid electrolyte includes a composite layer and a nanoporous layer. The positive electrode interface lacks a flexible polymer layer. The composite layer and the nanoporous layer are stacked. The thickness of the composite layer is 15 μm, and the thickness of the nanoporous layer is 10 μm.

[0240] Comparative Example 2

[0241] This comparative example is based on Example 1, with the following specific adjustments:

[0242] A gradient composite solid electrolyte includes a flexible polymer layer and a nanoporous layer, but lacks a composite layer. The flexible polymer layer and the nanoporous layer are stacked together. The thickness of the flexible polymer layer is 5 μm, and the thickness of the nanoporous layer is 10 μm.

[0243] Comparative Example 3

[0244] This comparative example is based on Example 1, with the following specific adjustments:

[0245] A gradient composite solid electrolyte includes a flexible polymer layer and a composite layer, lacking a nanoporous layer. The composite layer is directly deposited on the surface of the negative electrode. The composite layer and the flexible polymer layer are stacked together. The thickness of the composite layer is 15 μm, and the thickness of the flexible polymer layer is 5 μm.

[0246] Comparative Example 4

[0247] This comparative example is based on Example 1, with the following specific adjustments:

[0248] The components of the flexible polymer layer, the composite layer, and the nanoporous layer are directly mixed to form a single layer with a gradient-free structure and a thickness of 30 μm.

[0249] The performance of the composite solid electrolytes obtained in Examples 1-8 and Comparative Examples 1-4 was measured, and the results are shown in Table 1. The specific test methods are as follows:

[0250] Ionic conductivity was determined using electrochemical impedance spectroscopy (EIS): a solid electrolyte sample was sandwiched between stainless steel (ion-blocking electrodes) to form a sandwich structure. An AC signal with a frequency range of 10 mHz to 1 MHz was applied, and the bulk resistance (R) was obtained through the high-frequency intercept of the impedance spectrum. The conductivity was then calculated by combining the sample thickness (L) and area (S).

[0251] The interface contact resistance is determined using the four-probe method: a constant current is applied at the interface between the solid electrolyte and the electrode, the voltage drop is measured, and the contact resistance is directly calculated.

[0252] Cycle life (cycles, capacity retention) is measured using a full-cell cycle test: a positive electrode (NCM9) / SE / Li metal full cell is assembled and cycled hundreds of times under constant current charge-discharge conditions (e.g., 0.5C), and the capacity decay rate is recorded.

[0253] The thermal runaway trigger temperature was determined using differential scanning calorimetry (DSC): the sample was scanned at a heating rate of 10 °C / min, and the thermal runaway trigger point was determined by the exothermic peak initiation temperature.

[0254] The crack repair rate was determined using a mechanical property recovery test: after an external force was applied to the electrolyte to form a crack, the elastic modulus recovery rate after repair was measured by dynamic mechanical analysis (DMA).

[0255] Table 1. Performance of the composite solid electrolytes in Examples 1-8 and Comparative Examples 1-4

[0256]

[0257]

[0258] Based on the data in Table 1, the main factors affecting the performance of composite solid electrolytes are as follows:

[0259] 1. Ionic conductivity

[0260] Gradient Structure Effect: The gradient structures in Examples 1 and 2 enhance ionic conductivity, primarily due to the synergistic inorganic-organic effect of the composite layer (LATP / PEO). LATP (lithium aluminum titanium phosphate), as the inorganic filler, forms a rigid framework, shortening the lithium-ion migration path and reducing resistance. Meanwhile, PEO (polyethylene oxide), as the organic polymer, dissociates from the lithium salt (LiTFSI) through ether-oxygen bonds. The gradient structure ensures PEO is concentrated in the intermediate layer, avoiding side reactions caused by direct contact with the electrode, further optimizing the ion transport path. This results in smoother and more efficient lithium-ion transport in the composite solid electrolyte, thereby improving overall ionic conductivity.

[0261] Defects of Gradientless Structure: In Comparative Example 4, the inorganic filler (LATP) and polymer (PEO) in the mixed layer are randomly distributed, which leads to the breakage of ion channels. Lithium ions are more hindered during transport, resulting in a decrease in conductivity to 1.5×10-3S / cm, which is much lower than that in Examples 1 and 2.

[0262] 2. Regarding interface contact resistance

[0263] Synergistic effect of flexible polymer layer and nanoporous layer: The interfacial contact resistance of Example 1 is 18Ω, which is significantly lower than 45Ω of Comparative Example 1. This is because the flexible polymer layer (PVDF-HFP / ACM) has good elastic buffering properties, which can effectively reduce interfacial stress and reduce problems such as poor mechanical contact at the interface. Simultaneously, the bottom layer of nanoporous layer (SiO2) combines SiO2 with SiO2... x The formation of Si-O-Si covalent bonds at the negative electrode enhances the interaction between interfaces, further reduces the interfacial contact resistance, and makes the transport of lithium ions at the interface smoother.

[0264] The impact of lacking a flexible or composite layer: In Comparative Example 2, the composite layer was missing, resulting in direct contact failure between the flexible and porous layers, and the interfacial resistance surged to 80Ω. This demonstrates that the composite layer plays a crucial intermediate transition role in interfacial stability; its absence severely impacts ion transport at the interface, increasing interfacial contact resistance.

[0265] 3. Cycle life

[0266] Contribution of Self-Healing Function: Examples 6 and 7 achieved self-healing functionality by embedding thermally responsive microcapsules in the composite layer, significantly improving cycle life. Triggered at 60–80°C, the microcapsules release the core material (PEGDA or PEGMEA) and solidify to form a conductive network. This effectively inhibits crack propagation and repairs ion channels, maintaining the integrity of the electrolyte's internal structure and reducing problems such as ion transport obstruction caused by crack formation during cycling, thereby extending the battery's cycle life. For example, Example 6 achieved a cycle life of 1800 cycles with a capacity retention of 92%, significantly better than Example 1's 1300 cycles and 88%.

[0267] Other influencing factors: In addition to the self-healing function, the gradient structure also has a positive impact on cycle life. For example, Example 4 has a high ionic conductivity (3.2×10-3 S / cm) and a low interfacial contact resistance (14Ω), achieving a cycle life of 1900 cycles and a capacity retention of 91%. This indicates that good ion transport performance and interfacial stability are important foundations for achieving a long cycle life.

[0268] 4. Thermal runaway trigger temperature

[0269] Synergistic effect of nanoporous layer and microcapsule shell: The thermal runaway trigger temperature of Examples 6 and 7 is higher than that of other examples, mainly due to the "thermal barrier" effect of the nanoporous layer (SiO2, melting point >1000℃), which can effectively block heat transfer and prevent heat from rapidly accumulating and spreading inside the electrolyte. At the same time, the microcapsule shell (polydopamine or polyurethane) has an inhibitory effect on local hot spots. When the local temperature rises, the microcapsule shell can absorb some heat or alleviate the local thermal effect through its own structural changes, thereby improving the thermal stability of the entire composite solid electrolyte and increasing the thermal runaway trigger temperature.

[0270] Negative impacts of lacking a flexible layer or gradient structure: In Comparative Example 1, the lack of a flexible layer led to stress concentration at the lithium metal anode interface, increasing the risk of dendrite penetration, shortening the cycle life to 600 cycles, and reducing capacity retention to only 75%. Furthermore, due to the direct exposure of the composite layer (380℃) without the buffering and protection of a flexible layer, the thermal runaway temperature decreased to 190℃. In Comparative Example 4, the absence of a gradient structure resulted in disordered distribution of inorganic fillers and polymers in the mixed layer, leading not only to ion channel breakage but also to deterioration of thermal stability, with a thermal runaway temperature of only 170℃.

[0271] 5. Crack repair rate

[0272] The role of thermally responsive microcapsules: The high crack repair rates of Examples 6 and 7, at 92% and 95% respectively, are attributed to the thermally responsive microcapsules embedded in the composite layer. Triggered at specific temperatures, the microcapsules release the core material and solidify to form a conductive network, effectively repairing cracks caused by mechanical stress and other factors, restoring the integrity of ion channels, and thus ensuring the performance stability of the electrolyte. This self-healing function is of great significance for improving battery safety and lifespan, especially during long-term battery operation, effectively addressing potential structural damage.

[0273] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0274] In this embodiment, the design employs a gradient increasing Young's modulus of the flexible layer, composite layer, and nanoporous layer to match the thermal expansion coefficients of the silicon anode and high-nickel cathode, thereby improving the cyclic stress dispersion efficiency and suppressing interfacial crack propagation. Simultaneously, the elastomer absorbs the expansion stress of the silicon anode, preventing mechanical failure, and the interfacial impedance remains stable after cycling.

[0275] In this embodiment, the inorganic electrolyte and the polymer matrix synergistically form a continuous conductive network, resulting in high overall conductivity and supporting high-rate charge and discharge. Simultaneously, the fluoropolymer is compatible with the NCM9-based cathode, suppressing transition metal dissolution.

[0276] In this embodiment, the nanoporous material exhibits high porosity and low thermal decomposition temperature, is UL9540A certified, and does not ignite or explode during a needle penetration test. Simultaneously, the lithium salt demonstrates excellent high-temperature stability, inhibiting excessive SEI film growth; its high ion transference number also suppresses dendrite penetration.

[0277] In this embodiment, the polymer matrix wets the inorganic particles, reducing grain boundary impedance and improving ion transport efficiency. Simultaneously, the top layer of fluoropolymer provides oxidation resistance, the bottom layer of SiO2 is compatible with the silicon anode, and the middle layer of LLZO / PEO provides interface passivation, suppressing side reactions.

[0278] In this embodiment, thermally responsive microcapsules are embedded in a composite layer. When the internal temperature of the battery reaches a preset threshold, the shell ruptures to release the core material, which fills the interface cracks and solidifies to form Li. + A conductive network enables in-situ self-healing. After the core material cures, its conductivity recovers to 85% of its initial value, and the crack filling rate is >90%.

[0279] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A gradient composite solid electrolyte, comprising: Flexible polymer layers, composite layers, and nanoporous layers; The composite layer is located between the flexible polymer layer and the nanoporous layer, and the Young's modulus of the flexible polymer layer, the composite layer and the nanoporous layer increase in a gradient. The Young's modulus of the flexible polymer layer is 0.2 GPa to 0.4 GPa, the Young's modulus of the composite layer is 4 GPa to 6 GPa, and the Young's modulus of the nanoporous layer is 7 GPa to 9 GPa. The ionic conductivity of the flexible polymer layer at 25°C is 0.5 × 10⁻⁶. -3 S / cm~1.5×10 -3 The thermal decomposition temperature is 310℃~330℃, and the ionic conductivity of the composite layer at 25℃ is 1.5×10⁻⁶ S / cm. -3 S / cm~2.5×10 -3 S / cm, porosity of 9% to 11%, the porosity of the nanoporous layer is ≥60%, and the pore size is 10nm to 20nm; The gradient composite solid electrolyte is suitable for systems consisting of NCM9-based high-nickel cathodes and SiOx / C silicon-based anodes.

2. The gradient composite solid electrolyte according to claim 1, characterized in that, The thickness of the flexible polymer layer is 4μm to 6μm, and / or, The thickness of the composite layer is 12μm to 18μm, and / or, The thickness of the nanoporous layer is 8 μm to 12 μm.

3. The gradient composite solid electrolyte according to claim 1, characterized in that, The flexible polymer layer also includes the following performance parameters: porosity of 5% to 10%, and / or, The composite layer also includes the following performance parameters: a thermal decomposition temperature of 330℃~450℃, and / or, The nanoporous layer also includes the following performance parameters: thermal decomposition temperature ≥1000℃.

4. The gradient composite solid electrolyte according to claim 1, characterized in that, The flexible polymer layer is made of a copolymer of a matrix material and a reinforcing material, an elastomer, and a lithium salt, wherein the copolymer comprises polyvinylidene fluoride-hexafluoropropylene copolymer, perfluoroethylene propylene, or polyimide; and / or, The composite layer is made of inorganic electrolyte, polymer matrix, and lithium salt; and / or, The material of the nanoporous layer includes nanoporous materials.

5. The gradient composite solid electrolyte according to claim 4, characterized in that, The elastomer includes hydrogenated styrene elastomers, fluorinated elastomers, or acrylate rubbers.

6. The gradient composite solid electrolyte according to claim 4, characterized in that, The inorganic electrolyte includes one or a combination of at least two of lithium titanium aluminum phosphate, lithium lanthanum zirconium oxide, or lithium phosphorus sulfur chloride; the polymer matrix includes one or a combination of at least two of polyethylene oxide, polypropylene oxide, or polycaprolactone; and the lithium salt includes one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, or lithium dioxalate borate.

7. The gradient composite solid electrolyte according to claim 4, characterized in that, The nanoporous material includes one or a combination of at least two of SiO2, Al2O3, or ZrO2.

8. An in-situ interface repair structure comprising thermally responsive microcapsules, wherein the thermally responsive microcapsules are embedded in the composite layer of the gradient composite solid electrolyte according to any one of claims 1 to 7.

9. The in-situ interface repair structure according to claim 8, characterized in that, The thermally responsive microcapsule comprises a shell material and a core material, and the thermal response temperature of the thermally responsive microcapsule is 60℃~80℃.

10. The in-situ interface repair structure according to claim 9, characterized in that, The shell material is one or a combination of at least two of polydopamine, thermoplastic polyurethane, or polycaprolactone.

11. The in-situ interface repair structure according to claim 9 or 10, characterized in that, The thickness of the shell material is 40 nm to 60 nm.

12. The in-situ interface repair structure according to claim 9, characterized in that, The core material comprises one or a combination of at least two of acrylate or polyether oligomers, wherein the molecular weight of the acrylate or polyether oligomer is 300 Da to 500 Da.

13. The in-situ interface repair structure according to claim 9 or 12, characterized in that, The core material has the following performance parameters: viscosity ≤100 mPa·s, and the conductivity of the Li+ conductive network formed after curing at 25℃ ≥1×10⁻⁶. -4 S / cm.

14. The in-situ interface repair structure according to claim 8, characterized in that, The thermally responsive microcapsules have a particle size of 200 nm to 500 nm, and / or, The mass of the thermally responsive microcapsule is 1% to 5% of the total mass of the composite layer.

15. The in-situ interface repair structure according to claim 8, characterized in that, The thermally responsive microcapsules have the following performance parameters: crack filling rate ≥90%, and electrical conductivity restored to 85% of the initial value after repair.

16. A method for preparing a gradient composite solid electrolyte according to any one of claims 1 to 7, comprising: Nanoporous layers were prepared using the sol-gel method; A slurry for depositing a composite layer on the nanoporous layer by electrospinning is used. The slurry of the composite layer contains an inorganic electrolyte, a polymer matrix and a lithium salt. A slurry for depositing a flexible polymer layer on the composite layer by electrospinning.

17. The preparation method according to claim 16, characterized in that, The mass fraction of solute in the slurry of the flexible polymer layer is 10% to 20%; the mass fraction of solids in the slurry of the composite layer is 35% to 45%.

18. The preparation method according to claim 16, characterized in that, The method further includes: embedding thermally responsive microcapsules into the slurry of the composite layer by ultrasonic dispersion, and / or, An aminosilane coupling agent is introduced onto the surface of the nanoporous layer for interface modification to enhance the bonding force between the nanoporous layer and the composite layer.

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