Composite negative electrode material of all-solid-state lithium ion battery, preparation method thereof and all-solid-state lithium ion battery

Abstract

This invention discloses a composite anode material for an all-solid-state lithium-ion battery, its preparation method, and the all-solid-state lithium-ion battery itself, relating to the field of all-solid-state lithium-ion battery technology. The composite anode material comprises a silicon skeleton and multiple functional coating layers sequentially covering the outer surface of the silicon skeleton. The pore size and porosity of the silicon skeleton gradually increase from the inside out. The multiple functional coating layers, from the inside out, sequentially include a carbon layer, an ion-conducting layer, and an interface protection layer, wherein the ion-conducting layer is a composite material of a sulfide solid electrolyte and a lithium-containing compound. The silicon skeleton of this invention has a non-uniform pore distribution. This pore distribution structure allows the loose outer layer of the skeleton to effectively absorb stress, thereby more effectively protecting the structural integrity of the core region. This application achieves a synergistic effect of stress buffering, ion transport, and interface stabilization through multiple functional coating layers, suppressing the possibility of silicon anode failure and effectively extending the cycle life of the battery.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state lithium-ion battery technology, and more specifically, to a composite negative electrode material for all-solid-state lithium-ion batteries, its preparation method, and an all-solid-state lithium-ion battery. Background Technology

[0002] All-solid-state lithium-ion batteries are considered a promising next-generation high-energy-density rechargeable battery due to their high theoretical specific capacity. Silicon-based anodes, with a theoretical specific capacity reaching 4200 mAh / g, surpass the level of lithium metal anode materials (3860 mAh / g). Furthermore, silicon anode materials possess the natural property of suppressing lithium dendrite growth due to their moderate operating potential (approximately 0.1-0.5 V vs. Li+ / Li), and exhibit a higher critical current density compared to lithium-indium alloys. These inherent safety advantages and excellent electrochemical performance fully demonstrate the development potential of silicon-based solid-state batteries in the energy field. However, the massive volume expansion (approximately 300%) of pure silicon during cycling can lead to interfacial failure and electrode cracking, resulting in rapid capacity decay. Additionally, the interfacial side reactions between pure silicon and sulfide electrolytes can generate a high-resistivity interfacial phase. Therefore, solving these problems has become a key technical challenge for the development of pure silicon anodes.

[0003] Current technologies typically employ core-shell structured silicon-based composite anode materials. These materials feature a silicon-based core surrounded by a composite shell composed of a sulfide solid electrolyte and an electronically conductive agent. This design effectively mitigates volume expansion stress during charging and discharging through the mechanical buffering effect of the core-shell structure. Alternatively, current technologies utilize micron-sized silicon raw materials, preparing nano-silicon particles via liquid-phase milling, and constructing an electron-ion dual-conductivity polymer solid electrolyte coating layer on their surface. This composite coating layer comprises a polymer matrix, lithium salt, and conductive carbon material.

[0004] However, current technology has the following drawbacks: (1) Limitations of the buffering mechanism: The current core-shell structure mainly relies on the elastic deformation capability of the shell material to buffer the volume expansion of silicon, and its buffering capacity has a physical upper limit. When silicon material undergoes drastic volume expansion, the shell is prone to structural damage, leading to interfacial contact failure. Although silicon oxide (SiOx) can provide chemical buffering, it will significantly reduce the specific capacity of the material, making it difficult to balance high capacity and structural stability.

[0005] (2) Interface stability issues: Existing technologies generally adopt sulfide electrolyte coating schemes, but during cycling, repeated volume changes of silicon material can lead to stress concentration in the coating layer, which in turn can form microcracks. This interface defect can cause two problems: ① Sulfide electrolytes and silicon come into direct contact and produce side reactions; ② The natural oxide layer on the silicon surface decomposes with the sulfide electrolyte, and both generate high-resistivity interface phases, which severely hinder ion transport and accelerate capacity decay.

[0006] (3) Energy density constraint: The scheme of dispersing silicon particles with carbon-based framework has inherent defects. The mass ratio of carbon material in the electrode is too high (usually more than 30%), which significantly reduces the energy density per unit volume and per unit mass of the electrode, making it difficult to meet the design requirements of high energy density batteries.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The purpose of this invention is to provide a composite negative electrode material for an all-solid-state lithium-ion battery, a method for preparing the same, and an all-solid-state lithium-ion battery.

[0009] This invention is implemented as follows: In a first aspect, the present invention provides a composite negative electrode material for an all-solid-state lithium-ion battery, comprising a silicon skeleton and a multilayer functional coating layer sequentially covering the outer surface of the silicon skeleton. The pore size of the silicon skeleton gradually increases from the inside to the outside, and the porosity of the silicon skeleton gradually increases from the inside to the outside. The multilayer functional coating layer comprises, from the inside out, a carbon layer, an ion-conducting layer, and an interface protection layer, wherein the ion-conducting layer is a composite material of a sulfide solid electrolyte and a lithium-containing compound.

[0010] In an optional embodiment, the silicon skeleton has a particle size of 5-30 μm, a pore size of 5-20 nm extending outward from the center of the silicon skeleton to a radius of 1 / 3, and a pore size of 50-200 nm extending outward from a radius of 1 / 3 to the surface; and / or, the overall porosity of the silicon skeleton is 50%-70%.

[0011] In an optional embodiment, the coating thickness of the carbon layer is 2-10 nm; And / or, the raw material for the carbon layer is acetylene or methane.

[0012] In an optional embodiment, the coating thickness of the ion-conducting layer is 10-50 nm; And / or, based on a mass percentage of 100%, the sulfide solid electrolyte comprises 60%-90%, and the lithium-containing compound comprises 10%-40%; And / or, the sulfide solid electrolyte is Li6PS5Cl or Li 10 GeP2S 12 ; And / or, the lithium-containing compound is at least one of Li3N, Li3PO4, Li2ZrO3, LiTaO3 and LiAlO2.

[0013] In an optional embodiment, the coating thickness of the interface protective layer is 5-20 nm; And / or, the components of the interface protective layer include LiNbO3, LiTaO3, Li2ZrO3, and Li4Ti5O. 12 At least one of Li2CO3.

[0014] In a second aspect, the present invention provides a method for preparing a composite negative electrode material for an all-solid-state lithium-ion battery as described in any of the foregoing embodiments, wherein nano-silicon powder and a block copolymer template agent are dispersed in a first organic solvent to obtain a uniformly mixed slurry, and the mixed slurry is dried, ground, and then subjected to a first heat treatment to obtain the silicon skeleton; The carbon layer is coated on the outer surface of the silicon skeleton to obtain a carbon-coated silicon skeleton; The ion-conducting layer is formed on the outer surface of the carbon-coated silicon framework to obtain a double-coated silicon framework. An interface protective layer is formed on the outer surface of the double-layered silicon skeleton to obtain the composite anode material of the all-solid-state lithium-ion battery.

[0015] In an optional embodiment, the mass ratio of the nano-silica powder to the block copolymer template agent is 1:(0.5~2). And / or, the particle size of the nano-silicon powder is 30~100nm; And / or, the block copolymer template agent is a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer with a molecular weight of 2000~10000; And / or, the first organic solvent is selected from at least one of ethanol and isopropanol; And / or, the dispersion is performed by ultrasonic dispersion for a time of 30-60 min; And / or, the drying includes drying at 60~100°C for 10~12 hours; And / or, the grinding process yields micron-sized spherical composite precursor particles with a particle size of 5~30μm; And / or, the first heat treatment includes being carried out under a protective atmosphere, wherein the temperature is first held at 300~400℃ for 1~2 h; then the temperature is raised to 500~600℃ and held for 1~2 h; finally, the temperature is raised to 700~850℃ at a heating rate of 2~5℃ / min for 2~4 h, so that a three-dimensional interconnected porous framework is formed between the silicon particles, and then the silicon framework is naturally cooled to room temperature to obtain the silicon framework.

[0016] In optional embodiments, the method of coating the carbon layer includes chemical vapor deposition and liquid phase coating. Preferably, the chemical vapor deposition method is performed at a temperature of 500~700℃ for a time of 30~90 min.

[0017] In an optional embodiment, the ion-conducting layer is formed by a liquid-phase coating method, which includes: dissolving the sulfide solid electrolyte and the lithium-containing compound in a second organic solvent to prepare a precursor solution; immersing the carbon-coated silicon framework in the precursor solution; ultrasonically dispersing and stirring the mixture; and then performing a second heat treatment.

[0018] In an optional embodiment, the second organic solvent is anhydrous acetonitrile; And / or, the total concentration of the precursor solution is 0.1~0.5 mol / L; And / or, the ultrasonic dispersion time is 30~60 min; And / or, the temperature of the stirring reaction is 60~80℃, and the reaction time is 2~6 h; And / or, the second heat treatment includes heat treatment in argon at 150~250°C for 2~4 h.

[0019] In an optional embodiment, the interface protective layer is formed by a hydrothermal method, which includes mixing the metal elements in the components of the interface protective layer with ethanol to form a metal ethanol salt precursor solution, immersing the double-layered silicon skeleton in the metal ethanol salt precursor solution, performing a hydrothermal reaction, washing and drying after the reaction is completed, and performing a third heat treatment. Preferably, the metal element in the composition of the interface protective layer includes at least one of Li, Nb, Ta, Zr and Ti, and when the metal ethanol salt precursor solution contains multiple metal elements, the molar ratio between any two metal ethanol salts is 1:(1~1.2). Preferably, the hydrothermal reaction temperature is 100~180℃ and the reaction time is 1~4 h; Preferably, the temperature of the third heat treatment is 400~600℃, and the heat treatment time is 2~3h.

[0020] Thirdly, the present invention provides an all-solid-state lithium-ion battery, comprising a composite negative electrode material of an all-solid-state lithium-ion battery as described in any of the above embodiments, or a composite negative electrode material of an all-solid-state lithium-ion battery prepared by a method for preparing the composite negative electrode material of an all-solid-state lithium-ion battery as described in any of the above embodiments.

[0021] The present invention has the following beneficial effects: The composite anode material for all-solid-state lithium-ion batteries provided by this invention defines a silicon framework, giving it a three-dimensional porous structure with pore sizes that gradually increase from the inside out. The porosity of the silicon framework also gradually increases from the inside out, forming a non-uniform pore distribution. This pore distribution structure allows the loose outer layer of the framework to effectively absorb stress, thus more effectively protecting the structural integrity of the core area. Specifically, the region near the center of the silicon framework exhibits small pore sizes and low porosity, resulting in a high specific surface area, which is beneficial for improving lithium-ion insertion / extraction efficiency and capacity utilization. Conversely, the region near the outer surface of the silicon framework exhibits large pore sizes and high porosity, which can act as a physical buffer during silicon volume expansion, effectively accommodating the volume expansion stress during lithium insertion. This invention does not contain carbon frameworks or capacity-diluting components such as SiO2; it uses only a silicon framework, with carbon used only as a sub-nanometer thin film (2-10 nm) as a coating layer, maximizing the preservation of the high capacity characteristics of pure silicon. This invention also defines a multi-layered functional coating layer composed of a carbon layer, an ion-conducting layer, and an interface protection layer. The carbon layer enhances conductivity, buffers stress, and prevents direct contact between silicon and other coating layers. Unlike existing technologies that use only a single sulfide solid electrolyte, this application uses a sulfide electrolyte and a lithium-containing compound to form a nanocomposite material. Utilizing the high interfacial stability and wide electrochemical window of the lithium-containing compound, it synergistically improves interfacial compatibility and cycle stability. By constructing the ion-conducting layer, this application achieves a high ion conductivity channel with good compatibility with the silicon interface. The interface protection layer prevents direct contact between silicon and the sulfide solid electrolyte. This structure effectively reduces interfacial impedance and suppresses interfacial side reactions. This application achieves a synergistic effect of stress buffering, ion transport, and interface stability through a multi-layered functional coating layer, suppressing the possibility of silicon anode failure and effectively extending the battery's cycle life. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the composite anode material for an all-solid-state lithium-ion battery. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0025] Please see Figure 1 This invention provides a composite negative electrode material for an all-solid-state lithium-ion battery, comprising a silicon skeleton and a multilayer functional coating layer sequentially covering the outer surface of the silicon skeleton; the pore size of the silicon skeleton gradually increases from the inside to the outside, and the porosity of the silicon skeleton gradually increases from the inside to the outside; the multilayer functional coating layer comprises a carbon layer, an ion-conducting layer and an interface protection layer sequentially from the inside to the outside, wherein the ion-conducting layer is a composite material of a sulfide solid electrolyte and a lithium-containing compound.

[0026] This invention defines a silicon framework, giving it a three-dimensional porous structure with pore sizes that gradually increase from the inside out, and the porosity of the silicon framework also gradually increases from the inside out, forming a non-uniform pore distribution. This pore distribution structure allows the loose outer layer of the framework to effectively absorb stress, thereby more effectively protecting the structural integrity of the core area. Specifically, the region near the center of the silicon framework exhibits small pore sizes and low porosity, with a porosity of 20-60 μm. 2 The high specific surface area of ​​ / g is beneficial for improving the lithium-ion insertion / extraction efficiency and capacity utilization. The outer surface region near the silicon framework exhibits large pore size and high porosity, which can act as a physical buffer during silicon volume expansion, effectively accommodating the volume expansion stress during lithium insertion. Furthermore, this invention defines a multi-layered functional coating layer composed of a carbon layer, an ion-conducting layer, and an interface protection layer. The carbon layer enhances conductivity, buffers stress, and prevents direct contact between silicon and other coating layers. Unlike existing technologies that use only a single sulfide solid electrolyte coating, this application uses a sulfide electrolyte and a lithium-containing compound to form a nanocomposite material. Utilizing the high interfacial stability and wide electrochemical window of the lithium-containing compound, it synergistically improves interfacial compatibility and cycle stability. This application achieves a high ion conductivity and a conductive channel with good silicon interface compatibility by constructing an ion-conducting layer. The interface protection layer prevents direct contact between silicon and the sulfide solid electrolyte. This structure effectively reduces interfacial impedance and suppresses interfacial side reactions. This application suppresses the possibility of silicon anode failure through the synergistic effect of multiple functional coating layers, and can effectively extend the cycle life of the battery.

[0027] Next, the present invention will describe the silicon framework, carbon layer, ion conduction layer and interface protection layer in sequence.

[0028] (1) Silicon skeleton.

[0029] In this invention, the silicon skeleton has a particle size of 5-30 μm, the pore size in the range extending outward from the center of the silicon skeleton to 1 / 3 of the radius (i.e., near the center of the skeleton) is 5-20 nm, and the pore size in the range extending outward from 1 / 3 of the radius of the silicon skeleton to the surface (i.e., near the outer surface of the skeleton) is 50-200 nm; the overall porosity of the silicon skeleton is 50%-70%.

[0030] By limiting the pore size and porosity, this invention can effectively buffer the huge volume expansion of silicon, regulate solid-solid interface contact, construct continuous ion / electron pathways, reduce stacking pressure, and improve cycle stability.

[0031] The pores near the center of the framework have a diameter of 5-20 nm, which are micropores, while the pores near the outer surface of the framework have a diameter of 50-200 nm, which are mesopores and macropores. This application provides a physical buffer space for the volume expansion of silicon during the lithium intercalation process through the structural design of a three-dimensional porous silicon framework, with the characteristic of gradually increasing pore diameter from the inside to the outside. This can effectively absorb the stress generated by the volume expansion of silicon and avoid the breakage of the electrode material. In this invention, the large outer pore diameter is beneficial to providing more lithium intercalation space and can absorb expansion stress.

[0032] (2) Carbon layer.

[0033] The three-dimensional porous framework of the present invention is composed of pure silicon, with carbon existing only in the form of a thin film, and the coating thickness of the carbon layer is 2-10 nm; it does not occupy the volume of the main framework, thus maximizing the preservation of the high capacity characteristics of pure silicon.

[0034] This invention effectively enhances conductivity, buffers stress, and prevents direct contact between silicon and other coating layers by coating the surface of the silicon skeleton with a carbon layer.

[0035] The raw material for the carbon layer is acetylene or methane. The selection of this raw material is based on the use of chemical vapor deposition for the carbon layer in this invention. When other methods are used to coat the carbon layer, the raw material of the carbon layer can be adjusted accordingly.

[0036] (3) Ion conduction layer.

[0037] In this invention, the ion conduction layer is a composite material of sulfide solid electrolyte and lithium-containing compound. The ion conduction layer consists of 60%-90% sulfide solid electrolyte and 10%-40% lithium-containing compound by mass percentage. By combining sulfide solid electrolyte and lithium-containing compound, this invention can effectively utilize the high interfacial stability and wide electrochemical window of lithium-containing compound, thereby synergistically improving interfacial compatibility and cycle stability.

[0038] The sulfide solid electrolyte is Li6PS5Cl or Li 10 GeP2S 12 The lithium-containing compound is at least one of Li3N, Li3PO4, Li2ZrO3, LiTaO3 and LiAlO2.

[0039] Li6PS5Cl and Li 10 GeP2S 12 These are two high-performance sulfide solid electrolytes used in all-solid-state lithium batteries. Li6PS5Cl (also known as "argyrodite" electrolyte): contains no heavy metals, has a room-temperature ionic conductivity typically >3 mS / cm (approximately 0.003 S / cm), exhibits good stability to lithium metal anodes, but has moderate air stability. Li 10 GeP2S 12 (LGPS, Lithium Germanium Phosphate Sulfate): It has a highly symmetrical tetragonal structure and an ionic conductivity of 12-20 mS / cm at room temperature, but it contains the rare metal Ge, resulting in high cost and easy reduction by lithium, and it is also sensitive to air. Both are thiophosphate solid electrolytes.

[0040] Li3N and Li3PO4 are lithium salts, while Li2ZrO3, LiTaO3, and LiAlO2 are lithium-containing oxides. Li3N (lithium nitride) exhibits excellent high room-temperature ionic conductivity and effectively acts as an interface stabilizer, stabilizing the lithium metal anode, reducing interfacial impedance, suppressing dendrite formation, and pre-lithiation for lithium replenishment. Li3PO4 (lithium phosphate) can also serve as a highly stable interfacial layer in solid-state batteries, offering chemical stability, a wide electrochemical window, and suppression of interfacial interdiffusion. Li2ZrO3 (lithium zirconate), LiTaO3 (lithium tantalate), and LiAlO2 (lithium aluminate) are all highly stable, medium-to-low conductivity, and interface-friendly oxides in solid-state batteries. This invention, by combining a sulfide solid electrolyte with lithium-containing compounds, significantly improves interfacial compatibility and cycle stability.

[0041] The ion-conducting layer has a coating thickness of 10-50 nm, which enables a conductive channel with high ion conductivity and good compatibility with the silicon interface. The interface protection layer prevents direct contact between silicon and the sulfide solid electrolyte. This structure effectively reduces interfacial impedance and suppresses interfacial side reactions.

[0042] (4) Interface protective layer The interface protection layer can protect the interface between the negative electrode material and the electrolyte, achieve physical / chemical isolation, stabilize the structure, regulate ion / charge transport, and suppress harmful side reactions or failure mechanisms.

[0043] In this invention, the coating thickness of the interface protective layer is 5-20nm. When the coating thickness is too low, there will be insufficient protection, while when the coating thickness is too large, the function will be suppressed. The coating thickness (5-20nm) in this invention balances the defects of insufficient protection and functional suppression.

[0044] The raw materials for the interface protective layer include, but are not limited to, LiNbO3 (lithium niobate), LiTaO3 (lithium tantalate), Li2ZrO3 (lithium zirconate), and Li4Ti5O. 12 At least one of lithium titanate and lithium carbonate (Li2CO3). All of the above materials can effectively protect the interface.

[0045] Furthermore, the present invention also provides a method for preparing the composite anode material of the above-mentioned all-solid-state lithium-ion battery, which includes the following steps: S1. Disperse nano-silicon powder and block copolymer template agent in a first organic solvent to obtain a uniformly mixed slurry. After drying and grinding the mixed slurry, perform a first heat treatment to obtain a silicon skeleton.

[0046] The mass ratio of nano-silica powder to block copolymer template is 1:(0.5~2); the particle size of nano-silica powder is 30~100nm; the block copolymer template is polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (PEO-PPO-PEO) with a molecular weight of 2000~10000.

[0047] In this invention, nano-silicon powder and a block copolymer template agent are combined. The block copolymer template agent acts as a soft template, which self-assembles in a solvent to form micelles, vesicles, or ordered mesoscopic structures, thereby guiding the silicon source to arrange itself in an orderly manner according to its morphology, thus synthesizing a directing agent for mesoporous materials. The "soft template method" of this invention differs from hard templates (such as SiO2 nanospheres and anodic aluminum oxide) and has advantages such as tunable structure, controllable self-assembly, and a wide pore size range.

[0048] In this invention, by limiting the mass ratio of nano-silicon powder and block copolymer template agent, the template agent can fully coat the silicon particles and form a gradient distribution. Furthermore, by selecting nano-silicon powder with a particle size of 30~100nm as the raw material, nanoscale pore size can be guaranteed.

[0049] In this invention, the first organic solvent is selected from at least one of ethanol and isopropanol; the first organic solvent can effectively disperse the nano-silica powder and the block copolymer template agent. During the dispersion process, ultrasonic dispersion is used, and the dispersion time is 30-60 minutes. The ultrasonic conditions are conventional ultrasonic dispersion conditions, such as ultrasonic power of 100-300W. Those skilled in the art can also adjust the ultrasonic conditions according to actual conditions, as long as the uniform dispersion of the nano-silica powder and the block copolymer template agent is achieved.

[0050] After ultrasonic dispersion, the mixture is dried at 60–100 °C for 10–12 h. Drying removes the first organic solvent, causing microphase separation of the different blocks of the block copolymer template agent, spontaneously forming spherical nanostructures. Subsequent grinding refines these spherical nanostructures, yielding micron-sized spherical composite precursor particles with a particle size of 5–30 μm.

[0051] The subsequent first heat treatment effectively removes the block copolymer template agent, thereby forming a porous structure. Specifically, the first heat treatment is carried out under a protective atmosphere, wherein the temperature is first held at 300~400℃ for 1~2 h to form an initial porous structure; then the temperature is raised to 500~600℃ and held for 1~2 h to completely remove the block copolymer template agent; finally, the temperature is raised to 700~850℃ at a heating rate of 2~5℃ / min for 2~4 h to form a three-dimensional interconnected porous framework between silicon particles, and then naturally cooled to room temperature to obtain the silicon framework.

[0052] The silicon framework exhibits a structure characterized by a gradual increase in pore size and porosity from the inside out. The formation mechanism is as follows: During the drying process, the block copolymer template agent undergoes microphase separation when the solvent evaporates. Due to the influence of the solvent evaporation rate and micelle self-assembly kinetics, the micelle size increases in a gradient from the inside of the particle to the surface. During high-temperature heat treatment, the template agent decomposes, leaving pores. The silicon particles sinter at high temperature to form a three-dimensional interconnected framework, thereby replicating this gradient pore structure and achieving a gradual increase in pore size and porosity from the inside out.

[0053] S2. A carbon layer is coated on the outer surface of the silicon skeleton to obtain a carbon-coated silicon skeleton.

[0054] There are various methods for coating carbon layers, including but not limited to chemical vapor deposition and liquid phase coating. It should be noted that chemical vapor deposition and liquid phase coating are conventional coating methods in this field, and the parameters used can be found in the conventional parameters section.

[0055] In some typical but not limiting examples, chemical vapor deposition is performed at temperatures of 500–700 °C for 30–90 min.

[0056] In some typical but not limiting examples, when using a liquid-phase coating method, the silicon framework is immersed in an ethanol solution of glucose or sucrose, dried, and then heat-treated under an inert atmosphere to obtain a carbon layer. The thickness of the carbon layer can be adjusted according to the number of coating cycles and the solution concentration.

[0057] S3. An ion-conducting layer is formed on the outer surface of the carbon-coated silicon framework to obtain a double-coated silicon framework.

[0058] There are various ways to form an ion-conducting layer. This invention provides a typical but non-limiting example of forming an ion-conducting layer using a liquid-phase coating method. The liquid-phase coating method includes: dissolving a sulfide solid electrolyte and a lithium-containing compound in a second organic solvent to prepare a precursor solution; immersing a carbon-coated silicon framework in the precursor solution; ultrasonically dispersing and stirring the reaction; and then performing a second heat treatment.

[0059] The ion-conducting layer, by mass percentage (100%), comprises 60%-90% sulfide solid electrolyte and 10%-40% lithium-containing compound; the sulfide solid electrolyte is Li6PS5Cl or Li 10 GeP2S 12 The lithium-containing compound is at least one selected from Li3N, Li3PO4, Li2ZrO3, LiTaO3, and LiAlO2. The second organic solvent is anhydrous acetonitrile. The precursor solution is mixed according to the above proportions and the total concentration of the precursor solution is controlled to be 0.1~0.5 mol / L.

[0060] By immersing the carbon-coated silicon framework in a precursor solution and ultrasonically dispersing it for 30–60 min, the carbon-coated silicon framework can be effectively and uniformly dispersed in the precursor solution. The sulfide solid electrolyte and lithium-containing compounds in the precursor solution can also be uniformly dispersed. Subsequently, the reaction is stirred at 60–80 °C for 2–6 h. This stirring reaction allows the sulfide solid electrolyte and lithium-containing compounds in the precursor solution to crystallize on the carbon-coated silicon framework and uniformly coat its surface. The coating is uniform, and the thickness is controllable at the nanometer level. The reaction is mild and at low temperature; the equipment is simple and low-cost; it easily forms a core-shell structure and has good modification effects.

[0061] Subsequently, the shell is obtained by heat treatment in argon at 150~250℃ for 2~4 hours. The second heat treatment can evaporate the moisture of the coating and retain the core components, sulfide solid electrolyte and lithium-containing compounds.

[0062] S4. An interface protective layer is formed on the outer surface of the double-layer coated silicon skeleton to obtain a composite negative electrode material for all-solid-state lithium-ion batteries.

[0063] There are many methods for forming an interface protective layer. The present invention provides a typical but non-limiting example of the hydrothermal method, which includes mixing the raw materials of the interface protective layer with ethanol to form a metal ethanol salt precursor solution, immersing the double-layer coated silicon skeleton in the metal ethanol salt precursor solution, carrying out a hydrothermal reaction, washing and drying after the reaction is completed, and then carrying out a third heat treatment. The components of the interface protective layer include, but are not limited to, LiNbO3 (lithium niobate), LiTaO3 (lithium tantalate), Li2ZrO3 (lithium zirconate), and Li4Ti5O. 12 At least one of lithium titanate and lithium carbonate (Li₂CO₃). All of the above raw materials can effectively provide interfacial protection. The metal element in the interfacial protective layer includes at least one of Li, Nb, Ta, Zr, and Ti. When the metal ethanol salt precursor solution contains multiple metal elements, the molar ratio between any two metal ethanol salts is 1:(1~1.2). Subsequently, a hydrothermal reaction is carried out at 100~180℃ for 1~4 h. After washing and drying, a third heat treatment is performed at 400~600℃ for 2~3 h to obtain a composite anode material for all-solid-state lithium-ion batteries with an interfacial protective layer.

[0064] In this invention, the metal elements in the interface protective layer include at least two selected from Li, Nb, Ta, Zr, and Ti. By controlling the molar ratio between any two metal ethanol salts within the range of 1:(1~1.2) when the metal ethanol salt precursor solution contains multiple metal elements, the resulting interface protective layer can be guaranteed to have an accurate stoichiometric ratio and a uniform composition. A hydrothermal reaction allows the metal ethanol salt precursor solution to crystallize on the surface of the double-layered silicon framework. Subsequent heat treatment, at a temperature lower than the thermal decomposition temperature of the raw materials for the interface protective layer, ensures complete stability and prevents decomposition. Heat treatment dehydrates the raw materials of the surface-loaded interface protective layer, achieving grain sintering and densification, effectively forming the interface protective layer.

[0065] In addition, the present invention also provides an all-solid-state lithium-ion battery, which includes the composite anode material of the all-solid-state lithium-ion battery described above or the composite anode material of the all-solid-state lithium-ion battery prepared by the preparation method of the composite anode material of the all-solid-state lithium-ion battery described above.

[0066] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0067] Example 1 This embodiment provides a composite anode material for an all-solid-state lithium-ion battery, the preparation method of which includes the following steps: S1. Preparation of three-dimensional porous silicon framework.

[0068] 50 g of nano-silica powder (average particle size 50 nm, purity 99.9%) and 30 g of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymer template agent (molecular weight ≈ 5800, purchased from Wecklin) were dispersed in 500 mL of anhydrous ethanol and ultrasonically dispersed at room temperature (power 200 W) for 45 min to obtain a uniformly mixed slurry. The obtained mixed slurry was dried at 80 °C for 12 h, and then ground into fine powder in an agate mortar to obtain micron-sized spherical composite precursor particles (particle size 10~25 μm). Spherical composite precursor particles were placed in a tube furnace and calcined in stages under argon protection: first, they were held at 350℃ for 1.5 h to form an initial porous structure; then, the temperature was raised to 550℃ and held for 1.5 h to completely remove the template agent; finally, the temperature was raised to 800℃ at a rate of 3℃ / min for 3 h to form a three-dimensional interconnected porous framework between the silicon particles. After natural cooling to room temperature, a three-dimensional porous silicon framework with a particle size of 15 μm was obtained. At this point, the average pore size extending from the center of the silicon framework to one-third of its radius is about 10 nm, and the average pore size extending from one-third of the radius of the silicon framework to the surface is about 100 nm; the overall porosity of the silicon framework is 60%.

[0069] S2, Preparation of the carbon layer: The three-dimensional porous silicon framework obtained in step S1 was placed in a chemical vapor deposition reactor, and acetylene (C2H2) was used as the carbon source gas. The deposition was carried out at 600°C for 60 min to obtain a uniform carbon layer with a thickness of about 5 nm on the surface of the silicon framework.

[0070] S3. Preparation of the ion-conducting layer: 9.28 g of Li6PS5Cl, 1.16 g of Li3N, and 1.16 g of Li3PO4 were dissolved in 500 mL of anhydrous acetonitrile to prepare a precursor solution. The carbon-coated silicon framework obtained in step S2 was immersed in the precursor solution and dispersed by ultrasonication (200 W) for 45 min, followed by stirring at 70 °C for 4 h. The mixture was filtered and washed three times with anhydrous acetonitrile. The resulting product was placed in a tube furnace and heat-treated at 200 °C for 3 h under argon protection to form an ion-conducting layer with a thickness of approximately 15–30 nm on the surface of the carbon coating.

[0071] S4. Preparation of the interface protective layer: Preparation of niobium ethanol (C 10 H 25A mixed solution of LiNbO5 and lithium ethoxide (C2H5OLi) (molar ratio 1:1, concentrations 0.05 mol / L and 0.05 mol / L, respectively) was prepared. The material obtained in step 3 was immersed in the solution and transferred to a 100 mL high-pressure reactor. Hydrothermal reaction was carried out at 150 °C for 2 h. After cooling and filtration, the material was washed three times with anhydrous ethanol, vacuum dried at 60 °C for 6 h, and then heat-treated in a muffle furnace at 500 °C for 2.5 h to obtain a LiNbO3 interfacial protective layer with a thickness of approximately 10 nm, thus obtaining the composite anode material of this embodiment.

[0072] Example 2 This embodiment is basically the same as Embodiment 1, with the main difference being: In step S1, the average particle size of the nano-silicon powder is 80 nm, the amount of PEO-PPO-PEO template agent is 50 g (the mass ratio of PEO-PPO-PEO to nano-silicon powder is 1:1), and the drying temperature is 100℃. The segmented heat treatment conditions are: 400℃ for 2 h, 600℃ for 1 h, and 820℃ for 2 h.

[0073] In step S3, the amount of Li3N in the ion-conducting layer was adjusted to 2.32 g, the amount of Li3PO4 was adjusted to 0.58 g, and the other conditions remained unchanged.

[0074] Example 3 This embodiment is basically the same as Embodiment 1, with the main difference being: In step S4, the interface protective outer layer was replaced with LiTaO3 instead of LiNbO3. The hydrothermal reaction was carried out at 160℃ for 3 h, and the heat treatment was carried out at 550℃ for 2 h, resulting in a LiTaO3 interface protective layer with a thickness of approximately 12 nm.

[0075] Example 4 This embodiment provides a composite anode material for an all-solid-state lithium-ion battery, the preparation method of which includes the following steps: S1. Preparation of three-dimensional porous silicon framework.

[0076] 50 g of nano-silica powder (average particle size 50 nm, purity 99.9%) and 25 g of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymer template agent (molecular weight ≈ 5800, purchased from Wecklin) were dispersed in 500 mL of anhydrous ethanol and ultrasonically dispersed at room temperature (power 200W) for 30 min to obtain a uniformly mixed slurry. The obtained mixed slurry was dried at 60℃ for 12 h, and then ground into fine powder in an agate mortar to obtain micron-sized spherical composite precursor particles (particle size 10~25 μm). Spherical composite precursor particles were placed in a tube furnace and calcined in stages under argon protection: first, they were held at 300℃ for 2 h to form an initial porous structure; then, the temperature was raised to 500℃ and held for 2 h to completely remove the template agent; finally, the temperature was raised to 700℃ at a rate of 2℃ / min for 4 h to form a three-dimensional interconnected porous framework between the silicon particles. After natural cooling to room temperature, a three-dimensional porous silicon framework with a particle size of 12 μm was obtained. At this point, the average pore size extending from the center of the silicon framework to one-third of its radius is about 12 nm, and the average pore size extending from one-third of the radius of the silicon framework to its surface is about 90 nm; the overall porosity of the silicon framework is 58%.

[0077] S2, Preparation of the carbon layer: The three-dimensional porous silicon framework obtained in step S1 was placed in a chemical vapor deposition reactor, and methane was used as the carbon source gas. The deposition was carried out at 500°C for 90 min to obtain a uniform carbon layer with a thickness of about 2 nm on the surface of the silicon framework.

[0078] S3. Preparation of the ion-conducting layer: 9.28 g of Li6PS5Cl, 1.16 g of Li3N, and 1.16 g of Li3PO4 were dissolved in 500 mL of anhydrous acetonitrile to prepare a precursor solution. The carbon-coated silicon framework obtained in step S2 was immersed in the precursor solution and dispersed by ultrasonication (200 W) for 30 min, followed by stirring at 60 °C for 6 h. The mixture was filtered and washed three times with anhydrous acetonitrile. The resulting product was placed in a tube furnace and heat-treated at 150 °C for 4 h under argon protection to form an ion-conducting layer with a thickness of approximately 20 nm on the surface of the carbon coating.

[0079] S4. Preparation of the interface protective layer: Preparation of niobium ethanol (C 10 H 25A mixed solution of LiNbO5 and lithium ethoxide (C2H5OLi) (molar ratio 1:1, concentrations 0.05 mol / L and 0.05 mol / L, respectively) was prepared. The material obtained in step 3 was immersed in the solution and transferred to a 100 mL high-pressure reactor. Hydrothermal reaction was carried out at 100 °C for 4 h. After cooling and filtration, the material was washed three times with anhydrous ethanol, vacuum dried at 60 °C for 6 h, and then heat-treated in a muffle furnace at 400 °C for 3 h to obtain a LiNbO3 interfacial protective layer with a thickness of approximately 5 nm, thus obtaining the composite anode material of this embodiment.

[0080] Example 5 This embodiment provides a composite anode material for an all-solid-state lithium-ion battery, the preparation method of which includes the following steps: S1. Preparation of three-dimensional porous silicon framework.

[0081] 50 g of nano-silica powder (average particle size 50 nm, purity 99.9%) and 200 g of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymer template agent (molecular weight ≈ 5800, purchased from Wecklin) were dispersed in 500 mL of anhydrous ethanol and ultrasonically dispersed at room temperature (power 200 W) for 60 min to obtain a uniformly mixed slurry. The obtained mixed slurry was dried at 120℃ for 10 h, and then ground into fine powder in an agate mortar to obtain micron-sized spherical composite precursor particles (particle size 10~25 μm). Spherical composite precursor particles were placed in a tube furnace and calcined in stages under argon protection: first, they were held at 400℃ for 1 h to form an initial porous structure; then, the temperature was raised to 600℃ and held for 1 h to completely remove the template agent; finally, the temperature was raised to 850℃ at a rate of 5℃ / min for 2 h to form a three-dimensional interconnected porous framework between the silicon particles. After natural cooling to room temperature, a three-dimensional porous silicon framework with a particle size of 20 μm was obtained. At this point, the average pore size extending from the center of the silicon framework to one-third of its radius was about 15 nm, and the average pore size extending from one-third of the radius of the silicon framework to its surface was about 150 nm; the overall porosity of the silicon framework was 68%.

[0082] S2, Preparation of the carbon layer: The three-dimensional porous silicon framework obtained in step S1 was placed in a chemical vapor deposition reactor, and acetylene (C2H2) was used as the carbon source gas. The deposition was carried out at 700°C for 30 min to obtain a uniform carbon layer with a thickness of about 8 nm on the surface of the silicon framework.

[0083] S3. Preparation of the ion-conducting layer: 9.28 g of Li6PS5Cl, 1.16 g of Li3N, and 1.16 g of Li3PO4 were dissolved in 500 mL of anhydrous acetonitrile to prepare a precursor solution. The carbon-coated silicon framework obtained in step S2 was immersed in the precursor solution and dispersed by ultrasonication (200 W) for 60 min, followed by stirring at 80 °C for 2 h. The mixture was filtered and washed three times with anhydrous acetonitrile. The resulting product was placed in a tube furnace and heat-treated at 250 °C for 2 h under argon protection to form an ion-conducting layer with a thickness of approximately 40 nm on the surface of the carbon coating.

[0084] S4. Preparation of the interface protective layer: Preparation of niobium ethanol (C 10 H 25 A mixed solution of LiNbO5 and lithium ethoxide (C2H5OLi) (molar ratio 1:1, concentrations 0.05 mol / L and 0.05 mol / L, respectively) was prepared. The material obtained in step 3 was immersed in the solution and transferred to a 100 mL high-pressure reactor. Hydrothermal reaction was carried out at 180 °C for 1 h. After cooling and filtration, the material was washed three times with anhydrous ethanol, vacuum dried at 60 °C for 6 h, and then heat-treated in a muffle furnace at 600 °C for 2 h to obtain a LiNbO3 interfacial protective layer with a thickness of approximately 20 nm, thus obtaining the composite anode material of this embodiment.

[0085] Comparative Example 1 Take commercially available porous carbon material (specific surface area 1500 m²) 2 The silicon was mixed with nano-silicon particles (50 nm in diameter) at a mass ratio of 1:2 and loaded into the porous carbon pores by high-temperature melting.

[0086] Comparative Example 2 Nano-sized silicon particles (100 nm in diameter) were mixed with Li6PS5Cl sulfide solid electrolyte and conductive carbon black by ball milling (mass ratio of silicon:electrolyte:conductive carbon black = 80:15:5) and ball milled in argon for 3 h to obtain a surface-coated composite powder.

[0087] Comparative Example 3 This comparative example is basically the same as Example 1, except that the silicon framework in this comparative example has a uniform pore size and porosity. The preparation method of the silicon framework in this comparative example includes using a hard template method, mixing the same mass ratio of nano-silicon powder as in Example 1 with monodisperse SiO2 nanospheres (100 nm in diameter), pressing them into shape, sintering them at 800 °C for 3 h in argon, and then etching away the SiO2 template with 10% HF solution to obtain a silicon framework with a uniform pore size (about 80 nm). The remaining coating steps are the same as in Example 1.

[0088] Comparative Example 4 This comparative example is basically the same as Example 1, except that the pore size and porosity of the silicon skeleton in this comparative example gradually decrease from the inside to the outside. The preparation method of the silicon skeleton in this comparative example includes using an inverse gradient template, that is, controlling the solvent evaporation rate (rapid evaporation) during the drying process to make the micelle size gradually decrease from the inside to the outside. The remaining heat treatment conditions are the same as in Example 1, thereby obtaining a gradient pore structure with a large inner size and a small outer size.

[0089] Comparative Example 5 This comparative example is basically the same as Example 1, except that in this comparative example, only Li6PS5Cl is used for coating in step S3, omitting Li3N and Li3PO4, and the amount of Li6PS5Cl used is the total amount of Li6PS5Cl, Li3N and Li3PO4 used in Example 1.

[0090] Comparative Example 6 This comparative example is basically the same as Example 1, except that in this comparative example, the mass ratio of Li6PS5Cl, Li3N and Li3PO4 in step S3 is 5:2.5:2.5, and the total weight is the same as in Example 1.

[0091] Comparative Example 7 This comparative example is basically the same as Example 1. The main difference is that steps S2-S4 are omitted in this comparative example. The silicon skeleton with three-dimensional gradient pores obtained in step S1 of Example 1 is directly used as the negative electrode active material (without carbon layer, ion conduction layer and interface protection layer coating treatment).

[0092] Comparative Example 8 This comparative example is basically the same as Example 1. The main difference is that steps S3-S4 are omitted in this comparative example. The silicon skeleton with carbon layer prepared in step S2 of Example 1 is directly used as the negative electrode active material (without ion conduction layer and interface protection layer coating treatment).

[0093] Comparative Example 9 This comparative example is basically the same as Example 1. The main difference is that steps S2 and S4 are omitted in this comparative example. Instead, the silicon skeleton with three-dimensional gradient pores obtained in step S1 of Example 1 is directly coated with the ion conduction layer in step S3 (without carbon layer and interface protection layer coating treatment).

[0094] Comparative Example 10 This comparative example is basically the same as Example 1. The main difference is that steps S2 and S3 are omitted in this comparative example. Instead, the silicon skeleton with three-dimensional gradient pores obtained in step S1 of Example 1 is directly coated with the interface protective layer in step S4 (without carbon layer and ion conduction layer coating treatment).

[0095] Comparative Example 11 This comparative example is basically the same as Example 1. The main difference is that step S2 is omitted in this comparative example. Instead, the silicon skeleton with three-dimensional gradient pores obtained in step S1 of Example 1 is coated with the ion conduction layer in step S3 and the interface protection layer in step S4 (without carbon layer coating treatment).

[0096] Comparative Example 12 This comparative example is basically the same as Example 1. The main difference is that step S3 is omitted in this comparative example. Instead, the silicon skeleton with three-dimensional gradient pores obtained in step S1 of Example 1 is subjected to carbon layer coating in step S2 and interface protective layer coating in step S4 (without ion conduction layer coating treatment).

[0097] Comparative Example 13 This comparative example is basically the same as Example 1. The main difference is that step S4 is omitted in this comparative example. Instead, the silicon skeleton with three-dimensional gradient pores obtained in step S1 of Example 1 is coated with carbon layer in step S2, ion conduction layer in step S3, and interface protection layer in step S4 (without interface protection layer coating treatment).

[0098] Experimental Example 1 The negative electrode materials prepared in the above examples and comparative examples were subjected to performance testing. The testing items included particle size, specific surface area, porosity, and conductivity. Particle size was measured using a laser particle size analyzer (Malvern Mastersizer 3000); specific surface area was measured using the BET nitrogen adsorption method (Micromeritics ASAP 2460); porosity was measured using the mercury porosimetry method (AutoPore IV 9500); and conductivity was measured using an electrochemical workstation (Princeton).

[0099] Please refer to Table 1 for the test results: Table 1. Performance test statistics of anode materials for different examples

[0100] As can be seen from the table above, in Examples 1-5, the greater the amount of template agent used, the higher the porosity and the larger the specific surface area (Example 5 had the most template agent, reaching 72 m² / g; Example 4 had the least template agent, only 45 m² / g). 2 / g). Comparative Example 1 is porous carbon with an extremely high specific surface area (850 m). 2 / g). Carbon coating significantly improves conductivity (Examples 1-5: 3.0 × 10⁻⁶ g). -2 ~3.8×10 -2 S / cm); the conductivity of uncoated comparative examples 7 / 9 / 10 is only 10. -3 The conductivity is in the S / cm range. Comparative example 1, with its carbon-based framework, exhibits the highest conductivity (2.5 × 10⁻⁶). -1S / cm).

[0101] Experimental Example 2 The negative electrode materials obtained in the above examples and comparative examples were used to prepare electrode sheets. Ternary materials were used as the positive electrode, and LPSC sulfide was used as the electrolyte. A molded full cell was assembled under a pressure of 1 ton. The testing items included impedance, first-cycle coulombic efficiency, discharge specific capacity, cycle stability, rate performance, and impedance measurement. Impedance was measured using an electrochemical workstation (Princeton). Other tests were performed using charge-discharge equipment (Yuaneng Technology).

[0102] Please refer to Table 2 for the test results: Table 2. Statistical table of performance test results for batteries of different examples

[0103] As can be seen from the table above, the impedance of Examples 1-5 of the present invention is significantly lower than that of Comparative Examples 1-13, and the first-cycle efficiency, discharge specific capacity, capacity retention rate after 100 cycles at 0.5C, and 1C / 0.1C rate performance are all significantly better than those of Comparative Examples 1-13. Among them, Example 1 has a complete ion-conducting layer (containing Li3N / Li3PO4) and an interface protective layer, which can effectively reduce the interface impedance (Example 1 is only 45Ω).

[0104] Comparative Example 1 uses a mixture of commercially available porous carbon material and nano-silicon particles. Due to the high carbon content, its impedance is significantly increased, the first-cycle efficiency is reduced, the capacity is only 1800 mAh / g, and the capacity retention rate after 100 cycles at 0.5C and the rate performance at 1C / 0.1C are also significantly reduced.

[0105] Comparative Example 2 only underwent simple mixed coating, and its effect was significantly worse than that of Examples 1-5 of this application.

[0106] In Comparative Example 3, the silicon skeleton has a uniform pore size and porosity. In Comparative Example 4, the pore size and porosity of the silicon skeleton gradually decrease from the inside to the outside. Neither of these two silicon skeleton structures can achieve the effect of Example 1, proving that the pore size and porosity of the silicon skeleton have a significant impact on the performance of the battery.

[0107] Comparative Examples 5-6 show that omitting lithium-containing compounds or increasing their proportion leads to a significant decrease in performance compared to Example 1, and the interfacial impedance increases to 110Ω when only a single sulfide is used for coating (Comparative Example 5).

[0108] Comparative Examples 7-13 show that the performance of any single-layer and any double-layer structures is significantly lower than that of the three-layer structure in Example 1, demonstrating a synergistic effect among the three coating layers. The more complete the multilayer coating, the higher the initial efficiency. Example 1 (88.0%) has the best initial efficiency due to its complete three-layer coating and gradient pore structure. The uncoated Comparative Example 7 has an initial efficiency of only 55%, with a large amount of lithium ions consumed by irreversible side reactions; the higher the silicon content, the higher the capacity. Examples 1-5 and Comparative Examples 7-13, which have no carbon framework (silicon only), have high capacities (2400-3400 mAh / g). It is worth noting that although the uncoated Comparative Examples 7-10 have high initial capacity, the capacity decays very quickly, and the capacity drops significantly after 100 cycles, with the actual effective capacity being far lower than that of the examples; Example 1 (92.5%) has the best capacity retention rate, attributed to the synergistic protection of gradient pore buffer stress and the three functional coating layers. Omitting any coating layer significantly reduced retention (only 12% in Comparative Example 7); the carbon layer improved electronic conductivity, and the gradient pores promoted ion diffusion, resulting in the best rate performance in Example 1 (82.3%). The rate of return was significantly reduced when no coating layer or a key layer was missing.

[0109] In summary, the composite anode material for all-solid-state lithium-ion batteries provided by this invention, by constraining the silicon framework, gives it a three-dimensional porous structure with pore sizes that gradually increase from the inside out, and the porosity of the silicon framework also gradually increases from the inside out, forming a non-uniform pore distribution. This pore distribution structure allows the loose outer layer of the framework to effectively absorb stress, thereby more effectively protecting the structural integrity of the core area. Specifically, the region near the center of the silicon framework exhibits small pore sizes and low porosity, resulting in a high specific surface area, which is beneficial for improving lithium-ion insertion / extraction efficiency and capacity utilization. Conversely, the region near the outer surface of the silicon framework exhibits large pore sizes and high porosity, which can act as a physical buffer during silicon volume expansion, effectively adapting to the volume expansion stress of silicon during lithium insertion. Furthermore, this invention does not contain carbon frameworks or capacity-diluting components such as SiO2; it uses only a silicon framework, with carbon only used as a sub-nanometer thin film (2~10 nm) as a coating layer, maximizing the preservation of the high capacity characteristics of pure silicon. This invention also defines a multi-layered functional coating layer composed of a carbon layer, an ion-conducting layer, and an interface protection layer. The carbon layer enhances conductivity, buffers stress, and prevents direct contact between silicon and other coating layers. Unlike existing technologies that use only a single sulfide solid electrolyte, this application uses a sulfide electrolyte and a lithium-containing compound to form a nanocomposite material. Utilizing the high interfacial stability and wide electrochemical window of the lithium-containing compound, it synergistically improves interfacial compatibility and cycle stability. By constructing the ion-conducting layer, this application achieves a high ion conductivity channel with good compatibility with the silicon interface. The interface protection layer prevents direct contact between silicon and the sulfide solid electrolyte. This structure effectively reduces interfacial impedance and suppresses interfacial side reactions. This application achieves a synergistic effect of stress buffering, ion transport, and interface stability through a multi-layered functional coating layer, suppressing the possibility of silicon anode failure and effectively extending the battery's cycle life.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite anode material for an all-solid-state lithium-ion battery, characterized in that, It includes a silicon skeleton and multiple functional coating layers sequentially covering the outer surface of the silicon skeleton; The pore size of the silicon skeleton gradually increases from the inside to the outside, and the porosity of the silicon skeleton gradually increases from the inside to the outside. The multilayer functional coating layer comprises, from the inside out, a carbon layer, an ion-conducting layer, and an interface protection layer, wherein the ion-conducting layer is a composite material of a sulfide solid electrolyte and a lithium-containing compound.

2. The composite negative electrode material for an all-solid-state lithium-ion battery according to claim 1, characterized in that, The silicon skeleton has a particle size of 5-30 μm, the pore size extending from the center of the silicon skeleton outward to a radius of 1 / 3 is 5-20 nm, and the pore size extending from a radius of 1 / 3 of the silicon skeleton outward to the surface is 50-200 nm. And / or, the overall porosity of the silicon framework is 50% to 70%.

3. The composite negative electrode material for an all-solid-state lithium-ion battery according to claim 1, characterized in that, The thickness of the carbon layer is 2-10 nm; And / or, the raw material for the carbon layer is acetylene or methane; And / or, the coating thickness of the ion-conducting layer is 10-50 nm; And / or, based on a mass percentage of 100%, the sulfide solid electrolyte comprises 60%-90%, and the lithium-containing compound comprises 10%-40%; And / or, the sulfide solid electrolyte is Li6PS5Cl or Li 10 GeP2S 12 ; And / or, the lithium-containing compound is at least one of Li3N, Li3PO4, Li2ZrO3, LiTaO3 and LiAlO2; And / or, the coating thickness of the interface protective layer is 5-20 nm; And / or, the composition of the interface protective layer includes LiNbO3, LiTaO3, Li2ZrO3, Li4Ti5O 12 At least one of Li2CO3.

4. A method for preparing a composite negative electrode material for an all-solid-state lithium-ion battery as described in any one of claims 1-3, characterized in that, Nano-silicon powder and block copolymer template agent are dispersed in a first organic solvent to obtain a uniformly mixed slurry. The mixed slurry is dried, ground, and then subjected to a first heat treatment to obtain the silicon skeleton. The carbon layer is coated on the outer surface of the silicon skeleton to obtain a carbon-coated silicon skeleton; The ion-conducting layer is formed on the outer surface of the carbon-coated silicon framework to obtain a double-coated silicon framework. An interface protective layer is formed on the outer surface of the double-layered silicon skeleton to obtain the composite anode material of the all-solid-state lithium-ion battery.

5. The method for preparing the composite negative electrode material of the all-solid-state lithium-ion battery according to claim 4, characterized in that, The mass ratio of the nano-silicon powder to the block copolymer template agent is 1:(0.5~2). And / or, the particle size of the nano-silicon powder is 30~100nm; And / or, the block copolymer template agent is a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer with a molecular weight of 2000~10000; And / or, the first organic solvent is selected from at least one of ethanol and isopropanol; And / or, the dispersion is performed by ultrasonic dispersion for a time of 30-60 min; And / or, the drying includes drying at 60~100°C for 10~12 hours; And / or, the grinding process yields micron-sized spherical composite precursor particles with a particle size of 5~30μm; And / or, the first heat treatment includes being carried out under a protective atmosphere, wherein the temperature is first held at 300~400℃ for 1~2 h; then the temperature is raised to 500~600℃ and held for 1~2 h; finally, the temperature is raised to 700~850℃ at a heating rate of 2~5℃ / min for 2~4 h to form a three-dimensional interconnected porous framework between silicon particles, and then naturally cooled to room temperature to obtain the silicon framework.

6. The method for preparing the composite negative electrode material of the all-solid-state lithium-ion battery according to claim 4, characterized in that, Methods for coating the carbon layer include chemical vapor deposition or liquid phase coating. The chemical vapor deposition method is used when the deposition temperature is 500~700℃ and the deposition time is 30~90 min.

7. The method for preparing the composite negative electrode material of the all-solid-state lithium-ion battery according to claim 4, characterized in that, The ion-conducting layer is formed by a liquid-phase coating method, which includes: dissolving the sulfide solid electrolyte and the lithium-containing compound in a second organic solvent to prepare a precursor solution; immersing the carbon-coated silicon framework in the precursor solution; ultrasonically dispersing and stirring the mixture; and then performing a second heat treatment.

8. The method for preparing the composite negative electrode material of the all-solid-state lithium-ion battery according to claim 7, characterized in that, The second organic solvent is anhydrous acetonitrile; And / or, the total concentration of the precursor solution is 0.1~0.5 mol / L; And / or, the ultrasonic dispersion time is 30~60 min; And / or, the temperature of the stirring reaction is 60~80℃, and the reaction time is 2~6 h; And / or, the second heat treatment includes heat treatment in argon at 150~250°C for 2~4 h.

9. The method for preparing the composite negative electrode material of the all-solid-state lithium-ion battery according to claim 6, characterized in that, The interface protective layer is formed by a hydrothermal method, which includes mixing the metal elements in the components of the interface protective layer with ethanol to form a metal ethanol salt precursor solution, immersing the double-layered silicon framework in the metal ethanol salt precursor solution, carrying out a hydrothermal reaction, washing and drying after the reaction is completed, and then performing a third heat treatment. Preferably, the metal element in the composition of the interface protective layer includes at least one of Li, Nb, Ta, Zr and Ti, and when the metal ethanol salt precursor solution contains multiple metal elements, the molar ratio between any two metal ethanol salts is 1:(1~1.2). Preferably, the hydrothermal reaction temperature is 100~180℃ and the reaction time is 1~4 h; Preferably, the temperature of the third heat treatment is 400~600℃, and the heat treatment time is 2~3h.

10. A fully solid-state lithium-ion battery, characterized in that, It includes composite anode materials for all-solid-state lithium-ion batteries prepared by the preparation method of composite anode materials for all-solid-state lithium-ion batteries as described in any one of claims 1-3 or as described in any one of claims 4-9.

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