Negative electrode interface modification material, negative electrode plate, positive electrode interface functional layer, positive electrode plate, solid-state battery and electric device

Abstract

The invention discloses a negative electrode interface modification material, a negative electrode plate, a positive electrode interface functional layer, a positive electrode plate, a solid-state battery and a power utilization device, and relates to the technical field of batteries, the negative electrode interface modification material comprises a first polymer matrix, a reinforcing filler, a conductive agent and a lithium salt, the modulus of the reinforcing filler is greater than 50 GPa. The tensile strength of the negative electrode interface modification material can be improved through the first polymer matrix, breakage of a negative electrode interface modification layer is reduced, interface impedance is reduced, meanwhile, the first polymer matrix can be matched with the expansion coefficient of a silicon-based material, and bulging of a negative electrode plate is reduced. The modulus of the reinforcing filler is greater than 50GPa, so that the modulus of the negative electrode interface modification layer can be improved, the expansion of the silicon-based active material is further inhibited, the conductive agent can relieve the problem that the flexible substrate interface of the copper foil and the negative electrode interface modification layer possibly causes unsmooth electron transmission, and the lithium salt can improve the ion conduction capability and reduce the interface impedance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to negative electrode interface modification materials, negative electrode sheets, positive electrode interface functional layers, positive electrode sheets, solid-state batteries and electrical devices. Background Technology

[0002] With the booming development of new energy vehicles, range anxiety has become a key factor restricting their further popularization. Developing a solid-state battery with high specific energy and long range is undoubtedly the key to solving this dilemma. Among the many battery material systems, the "NCM9 series high-nickel cathode material + SiOx / C carbon-coated silicon suboxide anode material" system is regarded as the ideal choice for achieving high specific energy and long range solid-state batteries, carrying the high hopes of breaking through the range bottleneck of new energy vehicles. However, the 300% volume expansion of silicon-based anodes leads to mechanical failure of traditional interface layers, while the oxygen release of high-nickel cathodes exacerbates interface side reactions, such as causing capacity decay of ≥20% / 100 cycles. These problems limit the application of solid-state batteries. Summary of the Invention

[0003] This application provides a negative electrode interface modification material, a negative electrode sheet, a positive electrode interface functional layer, a positive electrode sheet, a solid-state battery, and an electrical device to reduce the expansion and capacity decay of silicon-based solid-state batteries.

[0004] In a first aspect, this application provides a negative electrode interface modification material, comprising a first polymer matrix, a reinforcing filler, a conductive agent, and a lithium salt, wherein: The heat resistance temperature of the polymer matrix is ​​greater than 200°C; The modulus of the reinforcing filler is greater than 50 GPa.

[0005] This application utilizes a first polymer matrix to improve the tensile strength of the negative electrode interface modification material, reduce fracture of the negative electrode interface modification layer, and reduce interfacial impedance. Simultaneously, the first polymer matrix can match the expansion coefficient of the silicon-based material, reducing the bulging of the negative electrode sheet. The heat resistance temperature of the polymer matrix, exceeding 200℃, reduces the shrinkage of the negative electrode interface modification layer, improving high-temperature stability. The modulus of the reinforcing filler, exceeding 50 GPa, increases the modulus of the negative electrode interface modification layer, further suppressing the expansion of the silicon-based active material. The conductive agent alleviates the potential problem of poor electron transport at the flexible substrate interface between the copper foil and the negative electrode interface modification layer. The lithium salt improves ion conductivity and reduces interfacial impedance.

[0006] In some embodiments, the negative electrode interface modification material further includes a self-healing agent, wherein the self-healing agent comprises a polymer containing dynamic covalent bonds. The self-healing agent of the polymer containing dynamic covalent bonds can improve the self-healing capability of the negative electrode interface modification layer, reduce crack formation, and reduce the probability of ion channel breakage.

[0007] In some embodiments, the self-healing agent comprises a second polymer containing furan groups and a third polymer containing maleimide groups. The furan and maleimide groups form dynamic covalent bonds, which can crosslink the second and third polymers. This dynamic covalent bond formation is reversible, exhibiting reversible breaking and recombination characteristics at 45-60°C to achieve dynamic self-healing capability. The furan group is a diene, and the maleimide group is a dienophile; they can form dynamic covalent bonds. When the temperature is in the range of 45-60°C, the covalent bonds recombine and polymerize, crosslinking the second and third polymers. When the temperature is above 60°C, the covalent bonds break, separating the crosslinked second and third polymers. The crosslinked body formed by the dynamic covalent bonds exhibits an island-like dispersion structure, which can avoid ion channel blockage, improve ion conduction capability, and reduce interfacial impedance. The second polymer comprises at least one of polyimide, polyetheretherketone, polyphenylene sulfide, bismaleimide, polyethersulfone, and polybenzimidazole. This second polymer acts as a hard segment in the three-dimensional crosslinked network, providing mechanical support and maintaining structural integrity; and / or, The third polymer includes at least one of polyurethane, polyurethane-urea, polyether, and polyester. This third polymer acts as a soft segment in the three-dimensional cross-linked network, imparting elastic deformation capability and buffering stress; and / or, The density of dynamic covalent bonds in self-healing agents is 3 mol% to 7 mol%. Within this density range, self-healing efficiency and ion channel patency can be balanced; and / or, The mass ratio of the second polymer containing furan groups to the third polymer containing maleimide groups is 1:(3~5). Within this range, the dynamic bond crosslinking density can be optimized, thus improving repair efficiency.

[0008] In some embodiments, the mass ratio of the first polymer matrix, reinforcing filler, conductive agent, and lithium salt is (40~50):(10~25):(1~3):(5~10). This mass ratio ensures synergy between mechanical strength, ionic conductivity, and electronic conduction; and / or, The first polymer matrix includes at least one of polyimide, polyetheretherketone, polyphenylene sulfide, bismaleimide, polyethersulfone, and polybenzimidazole. Selecting the above-mentioned first polymer matrix can improve heat resistance and tensile strength; and / or, The reinforcing filler includes at least one selected from boron nitride, aluminum nitride, silicon carbide, alumina, and graphene. Selecting the above-mentioned reinforcing filler can improve modulus and chemical inertness; and / or, The conductive agent includes at least one of carbon nanotubes, carbon black, and graphene; selecting the above conductive agent can construct a three-dimensional conductive network; and / or, The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, lithium difluorooxalateborate, lithium dioxalateborate, and lithium hexafluorophosphate. Selecting at least one of the above lithium salts can improve the lithium ion transference number and thermal stability.

[0009] Secondly, this application provides a negative electrode sheet, including a negative electrode current collector, a negative electrode active material layer and a negative electrode interface modification layer sequentially disposed on at least one side of the negative electrode current collector, wherein the material of the negative electrode interface modification layer includes the negative electrode interface modification material described in the first aspect.

[0010] The first polymer matrix can improve the tensile strength of the negative electrode interface modification material, reduce the fracture of the negative electrode interface modification layer, and reduce interfacial impedance. Simultaneously, the first polymer matrix can match the expansion coefficient of the silicon-based material, reducing the bulging of the negative electrode sheet. The heat resistance temperature of the polymer matrix, greater than 200℃, can reduce the shrinkage of the negative electrode interface modification layer, improving high-temperature stability and interfacial compatibility. The modulus of the reinforcing filler, greater than 50 GPa, can increase the modulus of the negative electrode interface modification layer, further suppressing the expansion of the silicon-based active material. The conductive agent can alleviate the problem of poor electron transport at the flexible substrate interface between the copper foil and the negative electrode interface modification layer. Lithium salt can improve ion conduction capability and reduce interfacial impedance.

[0011] In some embodiments, the negative electrode interface modification layer includes a first layer, a second layer, and a third layer that gradually move away from the negative electrode active material layer, wherein: The mass proportion of the reinforcing filler in the first to third layers decreases progressively, which allows the Young's modulus of the negative electrode interface modification layer to exhibit a gradient change, matching the expansion coefficient of the silicon-based material, reducing cracking of the negative electrode interface modification layer, and simultaneously suppressing the expansion of the silicon-based negative electrode active layer; and / or, The thickness ratio of the first, second, and third layers is (3~5):(1~3):(0.5~2). Within this range, a modulus gradient transition and matching of silicon expansion stress distribution can be achieved; and / or, The thickness of the first layer is 3~5μm. Within this range, the first layer can serve as a high-modulus region; and / or, The thickness of the second layer is 1~3μm. Within this range, the second layer can serve as a transition zone; and / or, The thickness of the third layer is 0.5~2μm. Within this range, the thickness of the third layer can serve as a low-modulus region; and / or, The thickness ratio of the negative electrode interface modification layer to the negative electrode active material layer is (1:10) to (1:20). Within this range, the ratio can suppress silicon-based material expansion and self-repair cracks while reducing the encroachment on the silicon-based negative electrode active material, thus minimizing the impact on battery energy density; and / or, The thickness of the negative electrode interface modification layer is 8~12μm. Within this range, the thickness of the negative electrode interface modification layer can suppress the expansion of silicon-based materials, self-repair cracks, reduce the crowding out of silicon-based negative electrode active materials, and minimize the impact on battery energy density.

[0012] In some embodiments, the mass percentage of the reinforcing filler in the first layer is 18% to 25%. Within this range, the mass percentage of the reinforcing filler in the first layer can directly suppress silicon expansion; and / or, The reinforcing filler in the second layer comprises 10% to 18% by mass. Within this range, the reinforcing filler can buffer stress concentration; and / or, The mass percentage of the reinforcing filler in the third layer is 0-10%. Within this range, the interfacial adhesion can be improved.

[0013] Thirdly, this application provides a positive electrode interface functional layer, including a first functional layer, a second functional layer disposed on one side of the first functional layer, and a third functional layer disposed on the side of the second functional layer away from the first functional layer, wherein: The material of the first functional layer includes a crystalline sulfide electrolyte; The material of the second functional layer includes an amorphous phase sulfide electrolyte; The material of the third functional layer includes a crystalline oxide electrolyte.

[0014] In solid-state batteries, the biggest problem on the positive electrode side is interfacial impedance, which causes energy density loss. This is addressed by a first functional layer, a second functional layer located on one side of the first functional layer, and a third functional layer located on the side of the second functional layer away from the first functional layer. The first functional layer is made of a crystalline sulfide electrolyte; the second functional layer is made of an amorphous sulfide electrolyte; and the third functional layer is made of a crystalline oxide electrolyte. This allows the first functional layer to provide ion channels and reduce interfacial impedance; the second functional layer to effectively buffer the lattice mismatch stress between the first and third functional layers; and the third functional layer to suppress lattice oxygen release in the high-nickel (NCM9) positive electrode, reducing interfacial oxygen vacancy concentration and minimizing oxygen vacancies caused by lattice oxygen loss, thereby comprehensively improving the impedance of the positive electrode interface.

[0015] In some embodiments, the material of the first functional layer is further modified with a phosphorus- and sulfur-containing grain boundary modifier. The crystalline sulfide electrolyte modified with the phosphorus- and sulfur-containing grain boundary modifier can further improve the ionic conductivity of the first functional layer, enhance ion transport capability, and further reduce interfacial impedance. The phosphorus- and sulfur-containing grain boundary modifiers include at least one of lithium phosphorus-sulfur-chloride, lithium germanium-phosphorus-sulfur, lithium trilithium phosphate sulfide, and lithium heptaphosphate sulfide. Selecting the aforementioned phosphorus- and sulfur-containing grain boundary modifiers can improve the grain boundary ionic conductivity; and / or, The phosphorus- and sulfur-containing grain boundary modifier accounts for 0.1% to 1% of the mass in the first functional layer. Within this range, the phosphorus- and sulfur-containing grain boundary modifier can reduce lattice distortion and maintain structural stability.

[0016] In some embodiments, the material of the second functional layer is further treated with rare earth elements. Rare earth element doping of the second functional layer can improve the ionic conductivity of the second functional layer, reduce ion accumulation in the second functional layer, and reduce interfacial impedance. The rare earth element includes at least one of Ge, Y, and La. This rare earth element can improve the ionic conductivity of the second functional layer and possesses chemical stability, making it less prone to side reactions; and / or, The rare earth elements constitute 1.5% to 2.5% of the mass of the second functional layer material. Within this range, the rare earth elements can suppress ion accumulation in the amorphous layer and reduce interfacial impedance.

[0017] In some embodiments, the thickness of the first functional layer is 1.25~2.5 μm. A thickness within this range can increase the specific surface area of ​​the ion channels; and / or, The thickness of the second functional layer is 0.2~0.45μm. Within this range, the thickness of the second functional layer can effectively buffer the lattice mismatch stress between the first and third functional layers, balancing the stress buffering-ion conduction performance; and / or, The thickness of the third functional layer is 3.5~7.1μm. Within this range, the thickness of the third functional layer can suppress the release of lattice oxygen in the high-nickel cathode (NCM9 system), reduce the concentration of oxygen vacancies at the interface, and balance the oxygen barrier-interface impedance.

[0018] Fourthly, this application provides a positive electrode sheet, including a positive current collector, a positive active material layer and a positive interface functional layer sequentially disposed on at least one side of the positive current collector, wherein the material of the positive interface functional layer includes the positive interface functional layer described in the third aspect.

[0019] The first functional layer, the second functional layer disposed on one side of the first functional layer, and the third functional layer disposed on the side of the second functional layer away from the first functional layer, wherein the material of the first functional layer includes a crystalline sulfide electrolyte; the material of the second functional layer includes an amorphous sulfide electrolyte; and the material of the third functional layer includes a crystalline oxide electrolyte, thereby enabling the first functional layer to provide ion channels and reduce interfacial impedance, the second functional layer to buffer stress, and the third functional layer to reduce oxygen vacancies caused by lattice oxygen loss, thereby comprehensively improving the impedance of the positive electrode interface.

[0020] In some embodiments, a self-healing layer is further provided on the side of the third functional layer at the positive electrode interface away from the second functional layer. The material of the self-healing layer includes a polymer containing dynamic covalent bonds. The raw materials of the polymer containing dynamic covalent bonds include a second polymer containing furan groups and a third polymer containing maleimide groups. The furan groups and maleimide groups form dynamic covalent bonds, which can crosslink the second and third polymers. The dynamic covalent bonds formed between the furan and maleimide groups are reversible, exhibiting reversible breaking and recombination characteristics at 45-60°C to achieve dynamic self-healing capability. The furan group is a diene, and the maleimide group is a dienophile; they can form dynamic covalent bonds. When the temperature is in the range of 45-60°C, the covalent bonds recombine and polymerize, crosslinking the second and third polymers. When the temperature is in the range of >60°C, the covalent bonds break, separating the crosslinked second and third polymers. The crosslinked body formed by the dynamic covalent bonds has an island-like dispersion structure, which can avoid ion channel blockage, improve ion conduction capability, and reduce interfacial impedance. The second polymer comprises at least one of polyimide, polyetheretherketone, polyphenylene sulfide, bismaleimide, polyethersulfone, and polybenzimidazole. This second polymer acts as a hard segment in the three-dimensional crosslinked network, providing mechanical support and maintaining structural integrity; and / or, The third polymer includes at least one of polyurethane, polyurethane-urea, polyether, and polyester. This third polymer acts as a soft segment in the three-dimensional cross-linked network, imparting elastic deformation capability and buffering stress; and / or, The density of dynamic covalent bonds in self-healing agents is 3 mol% to 7 mol%. Within this density range, self-healing efficiency and ion channel patency can be balanced; and / or, The mass ratio of the second polymer containing furan groups to the third polymer containing maleimide groups is 1:(3~5). Within this range, the dynamic bond crosslinking density can be optimized, thus improving repair efficiency.

[0021] Setting a self-healing layer at the positive electrode interface can repair microcracks at the positive electrode interface and reduce oxygen release side reactions in high-nickel materials.

[0022] In some embodiments, the thickness ratio of the positive electrode active material layer, the positive electrode interface functional layer, and the self-healing layer is (50~70):(5~10):(0.5~2). This thickness ratio, within this range, can balance energy density and interface protection requirements; and / or, The thickness of the self-healing layer is 0.5~2μm. Within this range, the thickness can improve the repair coverage without blocking ion channels; and / or, The thickness of the positive electrode interface functional layer is 5~10μm. Within this range, the thickness of the positive electrode interface functional layer can provide a complete protective layer.

[0023] Fifthly, this application provides a solid-state battery, including the negative electrode sheet described in the second aspect and the positive electrode sheet described in the fourth aspect.

[0024] In some embodiments of this application, when a solid-state battery simultaneously contains a negative electrode interface modification layer formed by a first aspect of negative electrode interface modification material on the negative electrode side, a third aspect of positive electrode interface functional layer on the positive electrode side, and a fourth aspect of self-healing layer, it can simultaneously achieve mechanical adaptation (negative electrode gradient modulus substrate suppresses silicon expansion), ion conduction (positive electrode multilayer gradient thin film structure reduces interface impedance), and dynamic repair (DA bond self-healing agent repairs microcracks).

[0025] Sixthly, this application provides an electrical device including the solid-state battery described in the fifth aspect. The electrical device includes, but is not limited to, new energy vehicles, drones, and portable electronic devices. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0027] With the booming development of new energy vehicles, range anxiety has become a key factor restricting their further popularization. Developing a solid-state battery with high specific energy and long range is undoubtedly the key to solving this dilemma. Among the many battery material systems, the "NCM9 series high-nickel cathode material + SiOx / C carbon-coated silicon suboxide anode material" system is regarded as the ideal choice for achieving high specific energy and long range solid-state batteries, carrying the high hopes of breaking through the range bottleneck of new energy vehicles. However, the 300% volume expansion of silicon-based anodes leads to mechanical failure of traditional interface layers, while the oxygen release of high-nickel cathodes exacerbates interface side reactions, such as causing capacity decay of ≥20% / 100 cycles. These problems limit the application of solid-state batteries.

[0028] Conventional methods involve depositing a single LLZO lithium lanthanum zirconium oxide ceramic layer (200 nm) on the SiOx anode surface to suppress volume expansion through high mechanical strength. However, this approach suffers from several drawbacks, including mechanical mismatch between the brittle ceramic layer (Young's modulus > 150 GPa) and the silicon-based material (50-100 GPa), a 92% cracking rate after 50 cycles, a lithium-ion diffusion coefficient of only 1 × 10⁻⁸ cm² / s, and a surge in interfacial impedance > 300% at high rates.

[0029] Conventional self-repair is achieved through a polyurethane coating (10μm) containing disulfide bonds, which triggers dynamic bond recombination at 80℃. However, this method has drawbacks, such as the repair temperature exceeding the battery safety threshold (>60℃), posing a risk of thermal runaway, and the self-repair efficiency decreasing with the number of cycles (efficiency <40% after 100 cycles).

[0030] In view of this, this application provides a negative electrode interface modification material, a negative electrode sheet, a positive electrode interface functional layer, a positive electrode sheet, a solid-state battery, and an electrical device to reduce the expansion and capacity decay of silicon-based solid-state batteries.

[0031] In a first aspect, this application provides a negative electrode interface modification material, comprising a first polymer matrix, a reinforcing filler, a conductive agent, and a lithium salt, wherein: The heat resistance temperature of the polymer matrix is ​​greater than 200°C; The modulus of the reinforcing filler is greater than 50 GPa.

[0032] This application utilizes a first polymer matrix to improve the tensile strength of the negative electrode interface modification material, reduce fracture of the negative electrode interface modification layer, and reduce interfacial impedance. Simultaneously, the first polymer matrix can match the expansion coefficient of the silicon-based material, reducing the bulging of the negative electrode sheet. The heat resistance temperature of the polymer matrix, exceeding 200℃, reduces the shrinkage of the negative electrode interface modification layer, improving high-temperature stability. The modulus of the reinforcing filler, exceeding 50 GPa, increases the modulus of the negative electrode interface modification layer, further suppressing the expansion of the silicon-based active material. The conductive agent alleviates the potential problem of poor electron transport at the flexible substrate interface between the copper foil and the negative electrode interface modification layer. The lithium salt improves ion conductivity and reduces interfacial impedance.

[0033] In conjunction with the first aspect, in some embodiments provided in this application, the negative electrode interface modification material further includes a self-healing agent, wherein the self-healing agent comprises a polymer containing dynamic covalent bonds. The self-healing agent of the polymer containing dynamic covalent bonds can improve the self-healing capability of the negative electrode interface modification layer, reduce crack formation, and reduce the probability of ion channel breakage.

[0034] In conjunction with the first aspect, in some embodiments provided in this application, the self-healing agent comprises a second polymer containing furan groups and a third polymer containing maleimide groups. The furan groups and maleimide groups form dynamic covalent bonds, which can crosslink the second and third polymers. The dynamic covalent bonds formed by the furan groups and maleimide groups are reversible, exhibiting reversible breaking and recombination characteristics at 45~60℃ to achieve dynamic self-healing capability. The furan group is a diene, and the maleimide group is a dienophile. The two can form dynamic covalent bonds. When the temperature is in the range of 45~60℃, the covalent bonds recombine and polymerize, crosslinking the second and third polymers. When the temperature is in the range of >60℃, the covalent bonds break, separating the crosslinked second and third polymers. The crosslinked body formed by the dynamic covalent bonds has an island-like dispersion structure, which can avoid ion channel blockage, improve ion conduction capability, and reduce interfacial impedance.

[0035] In conjunction with the first aspect, in some embodiments provided in this application, the second polymer includes at least one of polyimide (PI), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), bismaleimide (BMI), polyethersulfone (PES), and polybenzimidazole (PBI). The second polymer acts as a hard segment in the three-dimensional cross-linked network, which can provide mechanical support and maintain structural integrity.

[0036] In conjunction with the first aspect, in some embodiments provided in this application, the third polymer includes at least one of polyurethane (PU), polyurethane-urea (PUU), polyether (PE), and polyester (PEs). The third polymer acts as a soft segment in the three-dimensional cross-linked network, which can impart elastic deformation capability and buffer stress.

[0037] In conjunction with the first aspect, in some embodiments provided in this application, the density of dynamic covalent bonds in the self-healing agent is 3 mol% to 7 mol%. The density of dynamic covalent bonds in the self-healing agent within this range can balance the self-healing efficiency and the patency of ion channels.

[0038] In conjunction with the first aspect, in some embodiments provided in this application, the mass ratio of the second polymer containing furan groups to the third polymer containing maleimide groups is 1:(3~5). This mass ratio optimizes the dynamic bond crosslinking density and improves repair efficiency.

[0039] In conjunction with the first aspect, in some embodiments provided in this application, the mass ratio of the first polymer matrix, reinforcing filler, conductive agent, and lithium salt is (40~50):(10~25):(1~3):(5~10). The mass ratio of the first polymer matrix, reinforcing filler, conductive agent, and lithium salt within this range can ensure the synergy of mechanical strength, ionic conductivity, and electronic conduction.

[0040] In conjunction with the first aspect, in some embodiments provided in this application, the first polymer matrix includes at least one of polyimide (PI), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), bismaleimide (BMI), polyether sulfone (PES), and polybenzimidazole (PBI). Selecting the above-mentioned first polymer matrix can improve heat resistance and tensile strength.

[0041] In conjunction with the first aspect, in some embodiments provided in this application, the reinforcing filler includes at least one of boron nitride, aluminum nitride, silicon carbide, alumina, and graphene. Selecting the above-mentioned reinforcing filler can improve the modulus and chemical inertness.

[0042] In conjunction with the first aspect, in some embodiments provided in this application, the conductive agent includes at least one of carbon nanotubes, carbon black, and graphene, and selecting the above-mentioned conductive agent can construct a three-dimensional conductive network.

[0043] In conjunction with the first aspect, in some embodiments provided in this application, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), and lithium hexafluorophosphate (LiPF6). Selecting at least one of the above lithium salts can improve the lithium ion transference number and thermal stability.

[0044] Secondly, this application provides a negative electrode sheet, including a negative electrode current collector, a negative electrode active material layer and a negative electrode interface modification layer sequentially disposed on at least one side of the negative electrode current collector, wherein the material of the negative electrode interface modification layer includes the negative electrode interface modification material described in the first aspect.

[0045] The first polymer matrix can improve the tensile strength of the negative electrode interface modification material, reduce the fracture of the negative electrode interface modification layer, and reduce interfacial impedance. Simultaneously, the first polymer matrix can match the expansion coefficient of the silicon-based material, reducing the bulging of the negative electrode sheet. The heat resistance temperature of the polymer matrix, greater than 200℃, can reduce the shrinkage of the negative electrode interface modification layer, improving high-temperature stability and interfacial compatibility. The modulus of the reinforcing filler, greater than 50 GPa, can increase the modulus of the negative electrode interface modification layer, further suppressing the expansion of the silicon-based active material. The conductive agent can alleviate the problem of poor electron transport at the flexible substrate interface between the copper foil and the negative electrode interface modification layer. Lithium salt can improve ion conduction capability and reduce interfacial impedance.

[0046] In conjunction with the second aspect, in some embodiments provided in this application, the negative electrode interface modification layer includes a first layer, a second layer, and a third layer that are gradually moved away from the negative electrode active material layer, wherein: the mass proportion of the reinforcing filler in the first to the third layers is set in a decreasing manner, which can make the Young's modulus of the negative electrode interface modification layer exhibit a gradient change, match the expansion coefficient of the silicon-based material, reduce the cracking of the negative electrode interface modification layer, and at the same time suppress the expansion of the silicon-based negative electrode active layer.

[0047] In conjunction with the second aspect, in some embodiments provided in this application, the thickness ratio of the first layer, the second layer and the third layer is (3~5):(1~3):(0.5~2). The thickness ratio of the first layer, the second layer and the third layer is within this range, which can achieve modulus gradient transition and match the silicon expansion stress distribution.

[0048] In conjunction with the second aspect, in some embodiments provided in this application, the thickness of the first layer is 3~5μm. Within this range, the thickness of the first layer can serve as a high modulus region.

[0049] In conjunction with the second aspect, in some embodiments provided in this application, the thickness of the second layer is 1~3μm. The thickness of the second layer within this range can serve as a transition zone.

[0050] In conjunction with the second aspect, in some embodiments provided in this application, the thickness of the third layer is 0.5~2μm. The thickness of the third layer within this range can serve as a low-modulus region.

[0051] In conjunction with the second aspect, in some embodiments provided in this application, the thickness ratio of the negative electrode interface modification layer to the thickness of the negative electrode active material layer is (1:10) to (1:20). Within this range, the thickness ratio of the negative electrode interface modification layer to the thickness of the negative electrode active material layer can suppress the expansion of silicon-based materials and self-repair cracks, while reducing the encroachment on silicon-based negative electrode active materials and reducing the impact on battery energy density.

[0052] In conjunction with the second aspect, in some embodiments provided in this application, the thickness of the negative electrode interface modification layer is 8~12μm. Within this range, the thickness of the negative electrode interface modification layer can suppress the expansion of silicon-based materials, self-repair cracks, reduce the encroachment on silicon-based negative electrode active materials, and minimize the impact on battery energy density.

[0053] In conjunction with the second aspect, in some embodiments provided in this application, the mass percentage of the reinforcing filler in the first layer is 18% to 25%. Within this range, the mass percentage of the reinforcing filler in the first layer can directly suppress silicon expansion.

[0054] In conjunction with the second aspect, in some embodiments provided in this application, the mass percentage of the reinforcing filler in the second layer is 10% to 18%. Within this range, the mass percentage of the reinforcing filler in the second layer can buffer stress concentration.

[0055] In conjunction with the second aspect, in some embodiments provided in this application, the mass percentage of the reinforcing filler in the third layer is 0-10%. Within this range, the mass percentage of the reinforcing filler in the third layer can improve the interfacial adhesion.

[0056] Thirdly, this application provides a positive electrode interface functional layer, including a first functional layer, a second functional layer disposed on one side of the first functional layer, and a third functional layer disposed on the side of the second functional layer away from the first functional layer, wherein: The material of the first functional layer includes a crystalline sulfide electrolyte; The material of the second functional layer includes an amorphous phase sulfide electrolyte; The material of the third functional layer includes a crystalline oxide electrolyte.

[0057] In solid-state batteries, the biggest problem on the positive electrode side is interfacial impedance, which causes energy density loss. This is addressed by a first functional layer, a second functional layer located on one side of the first functional layer, and a third functional layer located on the side of the second functional layer away from the first functional layer. The first functional layer is made of a crystalline sulfide electrolyte; the second functional layer is made of an amorphous sulfide electrolyte; and the third functional layer is made of a crystalline oxide electrolyte. This allows the first functional layer to provide ion channels and reduce interfacial impedance; the second functional layer to effectively buffer the lattice mismatch stress between the first and third functional layers; and the third functional layer to suppress lattice oxygen release in the high-nickel (NCM9) positive electrode, reducing interfacial oxygen vacancy concentration and minimizing oxygen vacancies caused by lattice oxygen loss, thereby comprehensively improving the impedance of the positive electrode interface.

[0058] Crystalline sulfide electrolytes include, but are not limited to, at least one of lithium thiophosphate (Li3PS4) and lithium germanium phosphate sulfide (Li10GeP2S12).

[0059] Amorphous sulfide electrolytes include, but are not limited to, germanium (Ge)-doped lithium thiophosphate (Li3PS4) and germanium-doped lithium thiophosphate (Li3.1Ge0.05PS4).

[0060] Crystalline oxide electrolytes include, but are not limited to, at least one of lithium aluminum germanium phosphate (LAGP) and lithium lanthanum zirconium oxide (LLZO).

[0061] In conjunction with the third aspect, in some embodiments provided in this application, the material of the first functional layer is further modified with a phosphorus- and sulfur-containing grain boundary modifier. The crystalline sulfide electrolyte modified with the phosphorus- and sulfur-containing grain boundary modifier can further improve the ionic conductivity of the first functional layer, enhance ion transport capability, and further reduce interface impedance. The phosphorus- and sulfur-containing grain boundary modifier includes at least one of lithium phosphorus sulfide chloride (Li6PS5Cl), lithium germanium phosphorus sulfide (Li10GeP2S12), lithium thiophosphate (Li3PS4), and lithium heptaphosphate sulfide (Li7P3S11). Selecting the above-mentioned phosphorus- and sulfur-containing grain boundary modifier can improve the ionic conductivity of the first functional layer.

[0062] In conjunction with the third aspect, in some embodiments provided in this application, the material of the first functional layer is further modified with a phosphorus- and sulfur-containing grain boundary modifier. The crystalline sulfide electrolyte modified with the phosphorus- and sulfur-containing grain boundary modifier can further improve the ionic conductivity of the first functional layer, enhance ion transport capability, and further reduce interfacial impedance. Specifically, the mass percentage of the phosphorus- and sulfur-containing grain boundary modifier in the first functional layer is 0.1% to 1%. Within this range, the mass percentage of the phosphorus- and sulfur-containing grain boundary modifier in the first functional layer can reduce lattice distortion and maintain structural stability.

[0063] In conjunction with the third aspect, in some embodiments provided in this application, the material of the second functional layer is further treated with rare earth elements. The material of the second functional layer treated with rare earth elements can improve the ionic conductivity of the second functional layer, reduce ion accumulation in the second functional layer, and reduce interfacial impedance. The rare earth elements include at least one of Ge, Y, and La. The rare earth elements can improve the ionic conductivity of the second functional layer and have chemical stability, making them less prone to side reactions.

[0064] In conjunction with the third aspect, in some embodiments provided in this application, the material of the second functional layer is further treated with rare earth elements. The rare earth element-doped material of the second functional layer can improve the ionic conductivity of the second functional layer, reduce ion accumulation in the second functional layer, and reduce interfacial impedance. Specifically, the mass percentage of the rare earth elements in the second functional layer material is 1.5% to 2.5%. Within this range, the mass percentage of rare earth elements in the second functional layer material can suppress ion accumulation in the amorphous layer and reduce impedance.

[0065] In conjunction with the third aspect, in some embodiments provided in this application, the thickness of the first functional layer is 1.25~2.5μm. Within this range, the thickness of the first functional layer can provide ion channels with high specific surface area.

[0066] In conjunction with the third aspect, in some embodiments provided in this application, the thickness of the second functional layer is 0.2~0.45μm. The thickness of the second functional layer within this range can effectively buffer the lattice mismatch stress between the first and third functional layers and balance the stress buffer-ion conduction performance.

[0067] In conjunction with the third aspect, in some embodiments provided in this application, the thickness of the third functional layer is 3.5~7.1 μm. Within this range, the thickness of the third functional layer can suppress lattice oxygen release in the high-nickel cathode (NCM9 system), reduce the concentration of oxygen vacancies at the interface, and balance oxygen barrier-interface impedance.

[0068] Fourthly, this application provides a positive electrode sheet, including a positive current collector, a positive active material layer and a positive interface functional layer sequentially disposed on at least one side of the positive current collector, wherein the material of the positive interface functional layer includes the positive interface functional layer described in the third aspect.

[0069] The first functional layer, the second functional layer disposed on one side of the first functional layer, and the third functional layer disposed on the side of the second functional layer away from the first functional layer, wherein the material of the first functional layer includes a crystalline sulfide electrolyte; the material of the second functional layer includes an amorphous sulfide electrolyte; and the material of the third functional layer includes a crystalline oxide electrolyte, thereby enabling the first functional layer to provide ion channels and reduce interfacial impedance, the second functional layer to buffer stress, and the third functional layer to reduce oxygen vacancies caused by lattice oxygen loss, thereby comprehensively improving the impedance of the positive electrode interface.

[0070] In conjunction with the fourth aspect, in some embodiments provided in this application, a self-healing layer is further provided on the side of the third functional layer at the positive electrode interface away from the second functional layer. The material of the self-healing layer includes a polymer containing dynamic covalent bonds. The raw materials of the polymer containing dynamic covalent bonds include a second polymer containing furan groups and a third polymer containing maleimide groups. The furan groups and maleimide groups form dynamic covalent bonds, which can crosslink the second and third polymers. The dynamic covalent bonds formed by the furan groups and maleimide groups are reversible, exhibiting reversible breaking and recombination characteristics at 45-60°C to achieve dynamic self-healing capability. The furan group is a diene, and the maleimide group is a dienophile; they can form dynamic covalent bonds. When the temperature is in the range of 45-60°C, the covalent bonds recombine and polymerize, crosslinking the second and third polymers. When the temperature is above 60°C, the covalent bonds break, separating the crosslinked second and third polymers. The crosslinked body formed by the dynamic covalent bonds has an island-like dispersed structure, which can avoid ion channel blockage, improve ion conduction capability, and reduce interfacial impedance. The self-healing layer, located on the side of the third functional layer away from the second functional layer, can leverage the high ion conductivity of the sulfide in the first functional layer, reduce the self-healing layer's obstruction of ion conduction, and is more conducive to photothermal curing, thus enhancing the self-healing capability.

[0071] In conjunction with the fourth aspect, in some embodiments provided in this application, the second polymer includes at least one of polyimide (PI), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), bismaleimide (BMI), polyethersulfone (PES), and polybenzimidazole (PBI). The second polymer acts as a hard segment in the three-dimensional cross-linked network, which can provide mechanical support and maintain structural integrity.

[0072] In conjunction with the fourth aspect, in some embodiments provided in this application, the third polymer includes at least one of polyurethane (PU), polyurethane-urea (PUU), polyether (PE), and polyester (PEs). The third polymer acts as a soft segment in the three-dimensional cross-linked network, which can impart elastic deformation capability and buffer stress.

[0073] In conjunction with the fourth aspect, in some embodiments provided in this application, the density of dynamic covalent bonds in the self-healing agent is 3 mol% to 7 mol%. The density of dynamic covalent bonds in the self-healing agent within this range can balance the self-healing efficiency and the patency of ion channels.

[0074] In conjunction with the fourth aspect, in some embodiments provided in this application, the mass ratio of the second polymer containing furan groups to the third polymer containing maleimide groups is 1:(3~5). This mass ratio optimizes the dynamic bond crosslinking density and improves repair efficiency.

[0075] Setting a self-healing layer at the positive electrode interface can repair microcracks at the positive electrode interface and reduce oxygen release side reactions in high-nickel materials.

[0076] In conjunction with the fourth aspect, in some embodiments provided in this application, the thickness ratio of the positive electrode active material layer, the positive electrode interface functional layer, and the self-healing layer is (50~70):(5~10):(0.5~2). The thickness ratio of the positive electrode active material layer, the positive electrode interface functional layer, and the self-healing layer within this range can balance the energy density and interface protection requirements.

[0077] In conjunction with the fourth aspect, in some embodiments provided in this application, the thickness of the self-healing layer is 0.5~2μm. The thickness of the self-healing layer within this range can improve the repair coverage without blocking the ion channels.

[0078] In conjunction with the fourth aspect, in some embodiments provided in this application, the thickness of the positive electrode interface functional layer is 5~10 μm. Within this range, the thickness of the positive electrode interface functional layer can provide a complete protective layer.

[0079] Fifthly, this application provides a solid-state battery, including the negative electrode sheet described in the second aspect and the positive electrode sheet described in the fourth aspect.

[0080] In some embodiments of this application, when a solid-state battery simultaneously contains a negative electrode interface modification layer formed by a first aspect of negative electrode interface modification material on the negative electrode side, a third aspect of positive electrode interface functional layer on the positive electrode side, and a fourth aspect of self-healing layer, it can simultaneously achieve mechanical adaptation (negative electrode gradient modulus substrate suppresses silicon expansion), ion conduction (positive electrode multilayer gradient thin film structure reduces interface impedance), and dynamic repair (DA bond self-healing agent repairs microcracks).

[0081] Sixthly, this application provides an electrical device including the solid-state battery described in the fifth aspect. The electrical device includes, but is not limited to, new energy vehicles, drones, and portable electronic devices.

[0082] The technical solutions provided in this application will be described in detail below with reference to the embodiments.

[0083] Examples 1 to 5 Embodiments 1 to 5 of this application provide a negative electrode interface modification material, comprising a first polymer matrix, reinforcing filler, conductive agent, and lithium salt, wherein: the heat resistance temperature of the first polymer matrix is ​​greater than 200℃; the modulus of the reinforcing filler is greater than 50 GPa, and its specific parameters are shown in Table 1. Table 1. Parameter settings of negative electrode interface modification materials in Examples 1 to 5

[0084] The negative electrode interface modification materials provided in Examples 1 to 5 can be prepared by the following methods: Preparation of self-healing agents: Third polymer: HDI:PTMG2000 = 3:2 (molar ratio), 80℃ / 6h, N2 protection; A third polymer containing maleimide groups (DA bond density 5 mol%), wherein the ratio of third polymer to maleimide ethanolamine is 10:1 (molar ratio). Furan-containing second polymer, second polymer: furan diamine = 1:1 (molar ratio), NMP solvent, 120℃ / 8h; Preparation of CQDs: Perylene glycol: Boric acid: Urea = 1:2:1 (mass ratio); Dry burning process: 280℃ / 2h (argon flow rate 50sccm); Purification: Dialysis (500 Da membrane, 48 h); Impregnation solution formulation: NMP 91.5wt% + self-healing agent + homemade CQDs (0.5wt%) + 0.1wt% F127 surfactant; Crosslinking process: The third polymer containing maleimide groups undergoes a Diels-Alder reaction (DA reaction) with the second polymer containing furan groups, forming a dynamic covalent network at 60℃ for 10h.

[0085] Ultrasonic dispersion: 40kHz / 30min (amplitude 50μm); Gradient curing: 60℃→25℃ / 2h, cooling rate 0.3℃ / min; Photothermal triggering: 808nm laser (power density 0.5W / cm2), irradiation for 30s, local temperature rise to 60℃; Pressure curing: 5MPa hot pressing and holding for 10 minutes.

[0086] The prepared self-healing agent is mixed with the first polymer matrix, reinforcing filler, conductive agent and lithium salt to obtain the negative electrode interface modification material.

[0087] Examples 6 to 10 Embodiments 6 to 10 of this application provide a negative electrode sheet, including a negative electrode current collector, a negative electrode active material layer and a negative electrode interface modification layer sequentially disposed on at least one side of the negative electrode current collector, the negative electrode interface modification layer including a first layer, a second layer and a third layer that gradually move away from the negative electrode active material layer, and its specific parameters are shown in Table 2: Table 2 Parameter settings for the negative electrode in Examples 6 to 10

[0088] The negative electrode sheets provided in Examples 6 to 10 can be prepared by the following methods: Current collector parameters: 10μm copper foil; Negative electrode active material layer parameters: SiOx / C (carbon-coated silicon suboxide) composite material, coated and molded (scraper gap 200μm, dried at 120℃ for 10min); The process parameters for preparing the negative electrode interface modification layer are as follows: pulping is carried out according to the formulations of Examples 1 to 5 in Table 1, electrospinning is performed with three nozzles (nozzles 1 / 2 / 3 correspond to the reinforcement filler ratio in Table 2), voltage is 30kV, receiving distance is 20cm, roller speed is 5m / min, and hot pressing is performed at 120℃ (5MPa, 10min). The slurry for preparing the negative electrode interface modification material was prepared according to the specified ratio. Three-nozzle alternating spinning was employed, with a receiving roller speed of 5 m / min and a nozzle switching interval of 10 s. The nozzle switching frequency was synchronized with the receiving roller speed to form a continuous gradient. Multi-nozzle electrospinning: Nozzle 1: Enhanced filler ratio 1 (forming a third layer); Nozzle 2: Enhanced filler ratio 2 (forming a second layer); Nozzle 3: Enhanced filler ratio 3 (forming the first layer); • Mixing parameters: Stir at 400 rpm for 2 hours, then ultrasonically disperse (40 kHz / 30 min); • Process parameters: Voltage 30kV, receiving distance: 20cm, roller speed 5m / min; • Direct composite: In-situ spinning on the negative electrode sheet, followed by hot pressing composite (120℃, 5MPa, 10min).

[0089] Examples 11 to 15 Embodiments 11 to 15 of this application provide a positive electrode interface functional layer, including a first functional layer, a second functional layer disposed on one side of the first functional layer, and a third functional layer disposed on the side of the second functional layer away from the first functional layer, wherein: the material of the first functional layer includes a crystalline sulfide electrolyte; the material of the second functional layer includes an amorphous sulfide electrolyte; and the material of the third functional layer includes a crystalline oxide electrolyte. Specific parameters are shown in Table 3. Table 3 Parameter settings of the positive electrode interface functional layer in Examples 11 to 15

[0090] Examples 11 to 15 provide a positive electrode interface functional layer that can be prepared using the following method: Substrate pretreatment: 1) Ultrasonic cleaning: ethanol / acetone 40kHz / 10min each, rinse with deionized water; 2) Plasma activation: Ar / O2 mixed plasma (power 200W, 5min) to increase surface energy. Gradient thin film deposition (multi-cavity continuous sputtering, including 3 independent sputtering cavities and 1 annealing cavity): First functional layer deposition: The first functional layer material was ball-milled for 24 hours (zirconia balls, argon protection) to form a target. Sputtering deposition in cavity 1: pulsed bias DC 4000W + RF 100W, Ar / H2S=20:0.2sccm, deposition rate 6nm / min; Second functional layer deposition: Switch target material and deposit on the surface of the first functional layer by sputtering through cavity 2: pulse bias DC400W, Ar 15sccm, deposition rate 4.5nm / min; Third functional layer deposition: Switch target material and deposit on the surface of the second functional layer by sputtering through cavity 3: pulse bias DC400W, O2 / Ar=1:10, deposition rate 18nm / min.

[0091] Post-processing: Annealing was performed in a direct-flow heating chamber at 300°C for 1 hour (Ar atmosphere), followed by nitrogen quenching (rate 50°C / s) to relieve interfacial stress. Examples 16 to 20 Embodiments 16 to 20 of this application provide a positive electrode sheet, including a positive electrode current collector, a positive electrode active material layer and a positive electrode interface modification layer sequentially disposed on at least one side of the positive electrode current collector, wherein the material of the positive electrode interface modification layer includes a first functional layer, a second functional layer, a third functional layer and a self-healing layer, wherein the first functional layer is close to the positive electrode active material layer, the third functional layer is far from the positive electrode active material layer, and the self-healing layer is on the side of the third functional layer far from the second functional layer. Specific parameters are shown in Table 4. Table 4. Parameter settings for the positive electrode plates in Examples 16 to 20

[0092] The positive electrode sheets provided in Examples 16 to 20 of this application can be prepared by the following methods: Current collector parameters: 15μm aluminum foil; Preparation of positive electrode active material layer: NCM9 (lithium nickel cobalt manganese oxide, nickel content 90%) material, micro-gravure coating, infrared drying parameters: scraper gap 250μm, drying at 100℃ for 1min; Functional layer deposition: 1) The positive electrode sheet is preheated to 80℃ (to reduce thermal stress), and Ar plasma etching is performed for 5min before sputtering (to improve adhesion); 2) The functional layer is prepared by multi-cavity continuous sputtering deposition process as described in Examples 11 to 15; Preparation of self-healing layer: The impregnation solution (NMP + self-healing agent + 0.5wt% CQDs) is sprayed according to the formula in Table 4, crosslinking is triggered by 808nm laser (0.5W / cm2, 30s), and hot pressing is performed at 60℃ (5MPa, 10min).

[0093] Examples 21 to 25 Embodiments 21 to 25 of this application provide a solid-state battery, the specific parameters of which are shown in Table 5: Table 5. Parameter settings for solid-state batteries in Examples 21 to 25

[0094] The solid-state batteries provided in Examples 21 to 25 can be prepared using the following methods: Preparation of positive electrode: 15μm aluminum foil current collector, coated with NCM9-based (lithium nickel cobalt manganese oxide, nickel content 90%) positive electrode material, with a scraper gap of 250μm, dried at 100℃ for 1min; The positive electrode sheet and the positive electrode interface modification layer (including the functional layer and the self-healing layer, the preparation process is as in Examples 16-20) are hot-pressed together (120℃, 5MPa, 10min). Preparation of the diaphragm: 20μm LLZO solid electrolyte sheet; Preparation of negative electrode: 10μm copper foil current collector, coated with SiOx / C (carbon-coated silicon suboxide) negative electrode material, with a scraper gap of 200μm, dried at 120℃ for 10min; Hot-pressing composite of negative electrode sheet and negative electrode interface modification layer (Examples 6-10) (120℃, 5MPa, 10min). Stacking sequence: positive electrode sheet - positive electrode interface functional layer - self-healing layer - separator - negative electrode interface modification layer - negative electrode sheet, liquid injection, in-situ curing (heat curing at 80℃ for 30min), heat sealing with aluminum-plastic film (180℃, 10MPa).

[0095] Comparative Example 1 Comparative Example 1 of this application provides a negative electrode interface modification material, which is similar to Example 1, except that it does not contain reinforcing fillers and self-healing agents.

[0096] Comparative Example 2 Comparative Example 2 of this application provides a negative electrode sheet, which is similar to Example 6, except that it uses the negative electrode interface modification material of Comparative Example 1.

[0097] Comparative Example 3 Comparative Example 3 of this application provides a positive electrode interface functional layer, which is similar to Example 11, except that it does not include a second functional layer or a third functional layer.

[0098] Comparative Example 4 Comparative Example 4 of this application provides a positive electrode sheet, which is similar to Example 16, except that it adopts the positive electrode interface functional layer of Comparative Example 3.

[0099] Comparative Example 5 Comparative Example 5 of this application provides a solid-state battery, similar to Example 21, except that it uses the negative electrode of Comparative Example 2.

[0100] Comparative Example 6 Comparative Example 6 of this application provides a solid-state battery, similar to Example 21, except that it uses the positive electrode of Comparative Example 4.

[0101] Comparative Example 7 Comparative Example 7 of this application provides a solid-state battery, which is similar to Example 21, except that the negative electrode does not contain a negative electrode interface modification layer and the positive electrode does not contain a positive electrode interface modification layer.

[0102] Comparative Example 8 Comparative Example 8 of this application provides a solid-state battery, specifically, the negative electrode interface modification layer is a 200nm LLZO ceramic layer.

[0103] Comparative Example 9 Comparative Example 9 of this application provides a solid-state battery, specifically, the positive electrode interface modification layer is a 10μm polyurethane coating containing disulfide bonds.

[0104] Performance testing The solid-state batteries of Examples 21 to 25 and Comparative Examples 5 to 9 were subjected to electrical performance tests, and the specific steps are as follows: Crack rate: SEM was used to observe the surface cracks of the negative electrode interface modification layer (flexible substrate) and the positive electrode interface modification layer (conductive functional layer) after cycling, and the crack area ratio was calculated.

[0105] Interface impedance: EIS test frequency 0.01Hz-1MHz, amplitude 20mV, constant temperature 25℃.

[0106] Ionic conductivity: blocked electrode method, DC polarization voltage 500mV, constant temperature 25℃.

[0107] Repair efficiency: The percentage of healed area was measured after repairing a standard crack (length × width = 10μm × 1μm) in the artificially created interface layer at 60℃ for 10min.

[0108] Energy density: 1C constant current charge and discharge (voltage range 2.7-4.2V, accuracy ±0.5%), calculate the first discharge energy.

[0109] The specific test results are shown in Table 6: Table 6 Performance of solid-state cells prepared in Examples 21 to 25 and Comparative Examples 5 to 9

[0110] As shown in Table 1, the solid-state batteries of Examples 21 to 25 have a gradient modulus substrate that matches the expansion stress of the silicon anode, with a cracking rate of <10%; the multilayer gradient thin film stacked structure provides continuous ion channels, with an ion conductivity of >0.7 mS / cm (25℃); and the DA bond has low-temperature self-healing with a repair efficiency of >85%.

[0111] Comparative Example 5 has a risk of mechanical failure because the negative electrode interface modification material does not contain reinforcing fillers and self-healing agents.

[0112] Comparative Example 6 has the risk of interfacial side reactions and dendrite penetration because the positive electrode interface functional layer does not contain a second or third functional layer.

[0113] Comparative Example 7 has a risk of direct contact failure because the negative electrode does not contain a negative electrode interface modification layer and the positive electrode does not contain a positive electrode interface modification layer.

[0114] Comparative Example 8 has a risk of mechanical mismatch and cracking due to the rigid ceramic layer.

[0115] Comparative Example 9 showed a risk of efficiency degradation due to side reactions caused by high-temperature repair.

[0116] In summary, the first polymer matrix can improve the tensile strength of the negative electrode interface modification material, reduce the fracture of the negative electrode interface modification layer, and reduce interfacial impedance. Simultaneously, the first polymer matrix can match the expansion coefficient of the silicon-based material, reducing the bulging of the negative electrode sheet. The heat resistance temperature of the polymer matrix, exceeding 200℃, can reduce the shrinkage of the negative electrode interface modification layer and improve high-temperature stability. The modulus of the reinforcing filler, exceeding 50 GPa, can increase the modulus of the negative electrode interface modification layer, further suppressing the expansion of the silicon-based active material. The conductive agent can alleviate the problem of poor electron transport at the flexible substrate interface between the copper foil and the negative electrode interface modification layer. Lithium salt can improve ion conduction capability and reduce interfacial impedance.

[0117] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0118] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0119] 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 negative electrode interface modification material, characterized in that, It includes a first polymer matrix, reinforcing fillers, conductive agents, and lithium salts, wherein: The heat resistance temperature of the first polymer matrix is ​​greater than 200℃; The modulus of the reinforcing filler is greater than 50 GPa.

2. The negative electrode interface modification material as described in claim 1, characterized in that, The negative electrode interface modification material also includes a self-healing agent, wherein the self-healing agent comprises a polymer containing dynamic covalent bonds.

3. The negative electrode interface modification material as described in claim 2, characterized in that, The self-healing agent comprises a second polymer containing furan groups and a third polymer containing maleimide groups, wherein the furan groups and maleimide groups form dynamic covalent bonds, and: The second polymer comprises at least one selected from polyimide, polyetheretherketone, polyphenylene sulfide, bismaleimide, polyethersulfone, and polybenzimidazole; and / or, The third polymer includes at least one of polyurethane, polyurethane-urea, polyether, and polyester; and / or, The density of dynamic covalent bonds in the self-healing agent is 3 mol%~7 mol%; and / or, The mass ratio of the second polymer containing furan groups to the third polymer containing maleimide groups is 1:(3~5).

4. The negative electrode interface modification material as described in claim 1, characterized in that: The mass ratio of the first polymer matrix, reinforcing filler, conductive agent, and lithium salt is (40~50):(10~25):(1~3):(5~10); and / or, The first polymer matrix includes at least one selected from polyimide, polyetheretherketone, polyphenylene sulfide, bismaleimide, polyethersulfone, and polybenzimidazole; and / or, The reinforcing filler includes at least one selected from boron nitride, aluminum nitride, silicon carbide, alumina, and graphene; and / or, The conductive agent includes at least one of carbon nanotubes, carbon black, and graphene; and / or, The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, lithium dioxalateborate, and lithium hexafluorophosphate.

5. A negative electrode sheet, characterized in that, The present invention includes a negative electrode current collector, a negative electrode active material layer and a negative electrode interface modification layer disposed sequentially on at least one side of the negative electrode current collector, wherein the material of the negative electrode interface modification layer includes the negative electrode interface modification material as described in any one of claims 1 to 4.

6. The negative electrode sheet as described in claim 5, characterized in that, The negative electrode interface modification layer includes a first layer, a second layer, and a third layer that gradually move away from the negative electrode active material layer, wherein: The mass percentage of reinforcing filler in the first to third layers is set in a decreasing order; and / or, The thickness ratio of the first, second, and third layers is (3~5):(1~3):(0.5~2); and / or, The thickness of the first layer is 3~5μm; and / or, The thickness of the second layer is 1~3μm; and / or, The thickness of the third layer is 0.5~2μm; and / or, The thickness ratio of the negative electrode interface modification layer to the thickness of the negative electrode active material layer is (1:10) to (1:20); and / or, The thickness of the negative electrode interface modification layer is 8~12μm.

7. The negative electrode sheet as described in claim 6, characterized in that, The reinforcing filler in the first layer accounts for 18% to 25% of the total mass; and / or, The reinforcing filler in the second layer accounts for 10% to 18% of the total mass; and / or, The mass percentage of the reinforcing filler in the third layer is 0-10%.

8. A positive electrode interface functional layer, characterized in that, It includes a first functional layer, a second functional layer disposed on one side of the first functional layer, and a third functional layer disposed on the side of the second functional layer away from the first functional layer, wherein: The material of the first functional layer includes a crystalline sulfide electrolyte; The material of the second functional layer includes an amorphous phase sulfide electrolyte; The material of the third functional layer includes a crystalline oxide electrolyte.

9. The positive electrode interface functional layer as described in claim 8, characterized in that, The material of the first functional layer is further modified with a phosphorus- and sulfur-containing grain boundary modifier, wherein: The phosphorus- and sulfur-containing grain boundary modifiers include at least one of lithium phosphorus-sulfur-chloride, lithium germanium-phosphorus-sulfur, lithium trilithium phosphate sulfide, and lithium heptaphosphate sulfide; and / or, The phosphorus- and sulfur-containing grain boundary modifier accounts for 0.1% to 1% of the mass in the first functional layer.

10. The positive electrode interface functional layer as described in claim 8, characterized in that, The material of the second functional layer is also treated with rare earth element doping, wherein: The rare earth element includes at least one of Ge, Y, and La; and / or, The rare earth elements account for 1.5% to 2.5% of the mass of the second functional layer material.

11. The positive electrode interface functional layer as described in claim 8, characterized in that: The thickness of the first functional layer is 1.25~2.5μm; and / or, The thickness of the second functional layer is 0.2~0.45μm; and / or, The thickness of the third functional layer is 3.5~7.1μm.

12. A positive electrode plate, characterized in that, It includes a positive current collector, a positive active material layer and a positive interface functional layer sequentially disposed on at least one side of the positive current collector, wherein the positive interface functional layer includes the positive interface functional layer according to any one of claims 8 to 11.

13. The positive electrode sheet as described in claim 12, characterized in that, A self-healing layer is further provided on the side of the third functional layer away from the second functional layer. The material of the self-healing layer comprises a polymer containing dynamic covalent bonds. The material of the self-healing layer comprises a second polymer containing furan groups and a third polymer containing maleimide groups, wherein the furan groups and maleimide groups form dynamic covalent bonds. The second polymer comprises at least one selected from polyimide, polyetheretherketone, polyphenylene sulfide, bismaleimide, polyethersulfone, and polybenzimidazole; and / or, The third polymer includes at least one of polyurethane, polyurethane-urea, polyether, and polyester; and / or, The density of dynamic covalent bonds in the self-healing agent is 3 mol%~7 mol%; and / or, The mass ratio of the second polymer containing furan groups to the third polymer containing maleimide groups is 1:(3~5).

14. The positive electrode sheet as described in claim 13, characterized in that: The thickness ratio of the positive electrode active material layer, the positive electrode interface functional layer, and the self-healing layer is (50~70):(5~10):(0.5~2); and / or, The thickness of the self-healing layer is 0.5~2μm; and / or, The thickness of the positive electrode interface functional layer is 5~10μm.

15. A solid-state battery, characterized in that, It includes the negative electrode as described in any one of claims 5 to 7, and the positive electrode as described in any one of claims 12 to 14.

16. An electrical appliance, characterized in that, Including the solid-state battery as described in claim 15.

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