Solid-state battery negative electrode material and preparation method thereof

Abstract

The application provides a solid-state battery negative material and a preparation method thereof. The preparation method comprises the following steps: adding silicon powder, titanium tetrachloride and zirconium tetrachloride into ethanol, adding a dispersing agent, and dispersing to obtain a mixed suspension; reacting the mixed suspension with a reducing agent to obtain a silicon-titanium-zirconium composite precursor; first calcining the silicon-titanium-zirconium composite precursor to obtain silicon-titanium-zirconium composite nanoparticles; dispersing the silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid in water to obtain a particle suspension; performing a hydrothermal reaction on the particle suspension to obtain a core-shell precursor; second calcining the core-shell precursor to obtain core-shell structure composite particles; mixing and grinding the core-shell structure composite particles with lithium carbonate, aluminum oxide and ammonium dihydrogen phosphate to obtain a mixed powder; and third calcining the mixed powder. The solid-state electrolyte has a reduced volume expansion rate, a high specific capacity, long cycle performance and good rate performance.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery materials technology, specifically to a solid-state battery anode material and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, and large-scale energy storage, increasingly higher demands are being placed on the energy density, cycle stability, and safety of batteries. All-solid-state batteries, by using solid electrolytes instead of traditional liquid electrolytes, effectively solve the safety hazards of liquid batteries such as leakage, combustion, and explosion. They also have a wider electrochemical window, allowing for the matching of high-specific-capacity positive and negative electrode materials, making them the core development direction for next-generation power batteries.

[0003] As a core component of solid-state batteries, the performance of the anode material directly determines the battery's energy density and cycle life. The theoretical specific capacity of traditional graphite anodes is only 372 mAh / g, which is insufficient to meet the development requirements of high-energy-density solid-state batteries, making the development of high-specific-capacity anode materials a research hotspot. Silicon, with its ultra-high theoretical specific capacity of 4200 mAh / g, is considered the most promising alternative to graphite. However, silicon experiences a volume expansion of up to 300% during charge and discharge, which easily leads to electrode pulverization, active material shedding, and interfacial contact failure. Furthermore, silicon's inherent poor conductivity severely restricts its commercial application in solid-state batteries.

[0004] To address the volume expansion problem of silicon anodes, existing technologies have proposed various modification schemes. For example, Chinese patent application CN120727780A proposes a "core-shell-functional layer" composite structure, using silicon nanosheets as the core, coated with a nitrogen-doped carbon inner layer and a lithium phosphate fast-ion conductor outer layer. The expansion is buffered by the mechanical confinement effect of the nitrogen-doped carbon, and the lithium phosphate layer optimizes ion transport. However, the interfacial bonding between the carbon layer and the silicon core is weak, making the coating layer prone to peeling during cycling. Furthermore, the ionic conductivity of the lithium phosphate layer still needs improvement, making it difficult to meet fast-charging requirements. Chinese patent application CN120497308A employs a combination of transition metal and alkaline earth metal dual doping and CVD carbon nanotube coating technology to construct a conductive-buffering dual-functional network, controlling the volume expansion rate to within 150% and achieving a capacity retention rate of 92% after 100 cycles. However, this technology does not optimize for the electrode-electrolyte interface impedance problem in solid-state batteries. The poor interfacial compatibility between silicon-based materials and solid electrolytes leads to high internal resistance, affecting rate performance.

[0005] Besides silicon-based anodes, alloy-based anode materials have also attracted widespread attention. Chinese patent application CN120388981A proposes a composite anode consisting of a nanotube lithium storage layer and a doped carbon layer, which buffers volume expansion through pore channels. However, the lithium storage capacity of this structure mainly depends on the nanotube array, resulting in a low specific capacity. Furthermore, the directional arrangement of nanotubes is complex and the fabrication cost is high.

[0006] Furthermore, the interfacial impedance of solid-state batteries is another key bottleneck restricting their performance. Poor chemical compatibility, poor contact, and grain boundary resistance between the electrodes and solid electrolytes lead to high interfacial impedance, affecting lithium-ion transport efficiency. Existing technologies reduce interfacial impedance through surface polishing, artificial SEI layer construction, or composite electrolyte optimization. However, these methods mostly address single interfacial issues and are difficult to achieve long-term stable control of interfacial impedance. Moreover, some methods (such as the preparation of artificial SEI layers by vapor deposition) are complex and difficult to scale up.

[0007] In summary, existing solid-state battery anode materials generally suffer from the following technical defects: (1) The volume expansion problem of high specific capacity materials (such as silicon-based materials) has not been fundamentally solved, and structural damage is prone to occur during cycling; (2) It is difficult to balance the electronic conductivity and ion transport performance of the materials, resulting in insufficient rate performance and fast charging performance; (3) The interface compatibility between the anode material and the solid electrolyte is poor, and the interface impedance is relatively high; (4) Some high-performance materials (such as ternary alloys) are too expensive or have complex preparation processes, which is not conducive to industrialization. Therefore, developing a solid-state battery anode material that combines high specific capacity, low volume expansion, excellent interface compatibility, and low cost and scalable preparation has become an urgent technical problem to be solved in this field. Summary of the Invention

[0008] Based on the technical problems described above, this invention aims to provide a solid-state battery anode material and its preparation method. By constructing a multi-layer composite structure of "silicon-titanium-zirconium composite core, nitrogen-boron co-doped carbon intermediate layer and lithium-aluminum-phosphorus-doped surface layer", the invention synergistically solves the problems of large volume expansion, poor conductivity and poor compatibility with solid electrolyte interface of silicon-based anodes, so as to achieve high specific capacity, low expansion, long cycle and excellent rate performance, while simplifying the process, reducing costs and meeting the needs of industrialization.

[0009] Specifically, according to one aspect of the present invention, a method for preparing a solid-state battery anode material is provided, the method comprising the following steps:

[0010] (1) Add nano-silicon powder, titanium tetrachloride and zirconium tetrachloride to anhydrous ethanol, add a dispersant, and ultrasonically disperse to obtain a mixed suspension, wherein the total weight of nano-silicon powder, titanium tetrachloride and zirconium tetrachloride is 100%, the nano-silicon powder accounts for 80-95%, the titanium tetrachloride accounts for 2-12%, and the zirconium tetrachloride accounts for 1-8%;

[0011] (2) The mixed suspension was reacted with a reducing agent in a high-pressure reactor to obtain a silicon-titanium-zirconium composite precursor;

[0012] (3) The silicon-titanium-zirconium composite precursor was calcined in an inert atmosphere to obtain silicon-titanium-zirconium composite nanoparticles.

[0013] (4) The silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid are dispersed in deionized water to obtain a particle suspension, wherein, based on the total weight of the silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid as 100%, the silicon-titanium-zirconium composite nanoparticles account for 30-50%, glucose accounts for 40-60%, urea accounts for 5-10%, and boric acid accounts for 2-5%;

[0014] (5) The particulate suspension is subjected to a hydrothermal reaction to obtain a core-shell precursor;

[0015] (6) The core-shell precursor is subjected to a second calcination in a reducing atmosphere to obtain core-shell structured composite particles;

[0016] (7) The core-shell composite particles are mixed and ground with lithium carbonate, alumina and ammonium dihydrogen phosphate to obtain a mixed powder, wherein, based on the total weight of the core-shell composite particles, lithium carbonate, alumina and ammonium dihydrogen phosphate as 100%, the core-shell composite particles account for 90-95%, lithium carbonate accounts for 3-6%, alumina accounts for 1-3%, and ammonium dihydrogen phosphate accounts for 1-2%;

[0017] (8) The mixed powder is subjected to a third calcination under an inert atmosphere to obtain the solid battery anode material.

[0018] According to certain preferred embodiments of the present invention, in step (1), the total weight of nano-silicon powder, titanium tetrachloride and zirconium tetrachloride is 100%, the nano-silicon powder accounts for 85-90%, the titanium tetrachloride accounts for 5-10%, and the zirconium tetrachloride accounts for 3-5%.

[0019] According to certain preferred embodiments of the present invention, in step (1), the ratio between the total weight of nano-silicon powder, titanium tetrachloride and zirconium tetrachloride and the weight of anhydrous ethanol is 1:3-1:6.

[0020] According to certain preferred embodiments of the present invention, in step (1), the dispersant is polyvinylpyrrolidone.

[0021] According to certain preferred embodiments of the present invention, in step (1), the ratio between the total weight of the nano-silicon powder, titanium tetrachloride and zirconium tetrachloride and the weight of the dispersant is 10:1-20:1.

[0022] According to certain preferred embodiments of the present invention, the particle size of the nano-silicon powder is in the range of 20-50 nm.

[0023] According to certain preferred embodiments of the present invention, in step (2), the reducing agent is sodium borohydride, and its addition amount is 3-5 times the total molar number of titanium tetrachloride and zirconium tetrachloride.

[0024] According to certain preferred embodiments of the present invention, in step (2), the reaction temperature in the high-pressure reactor is 180-220°C and the reaction time is 12-24 h.

[0025] According to certain preferred embodiments of the present invention, in step (3), the temperature of the first calcination is 800-1000℃ and the holding time is 2-4 h.

[0026] According to certain preferred embodiments of the present invention, the particle size of the silicon-titanium-zirconium composite nanoparticles is 50-200 nm.

[0027] According to certain preferred embodiments of the present invention, in step (4), based on the total weight of the silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid as 100%, the silicon-titanium-zirconium composite nanoparticles account for 35-40%, glucose accounts for 48-55%, urea accounts for 6-8%, and boric acid accounts for 2-4%.

[0028] According to certain preferred embodiments of the present invention, in step (4), the ratio between the total weight of the silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid and the weight of deionized water is 1:3-1:5.

[0029] According to certain preferred embodiments of the present invention, in step (5), the temperature of the hydrothermal reaction is 160-200°C and the reaction time is 8-12 h.

[0030] According to certain preferred embodiments of the present invention, in step (6), the reducing atmosphere is a mixture of argon and hydrogen.

[0031] According to certain preferred embodiments of the present invention, the volume ratio of argon to hydrogen in the reducing atmosphere is 8:1 to 10:1.

[0032] According to certain preferred embodiments of the present invention, in step (6), the second calcination temperature is 700-900°C and the holding time is 3-5 h.

[0033] According to certain preferred embodiments of the present invention, the surface of the core-shell composite particles has a porous structure, wherein the porosity is 20-30% and the pore size is 2-5 nm.

[0034] According to certain preferred embodiments of the present invention, in step (7), based on the total weight of the core-shell composite particles, lithium carbonate, alumina and ammonium dihydrogen phosphate as 100%, the core-shell composite particles account for 92-94%, lithium carbonate accounts for 4-5%, alumina accounts for 1-2%, and ammonium dihydrogen phosphate accounts for 1-1.5%.

[0035] According to certain preferred embodiments of the present invention, in step (8), the temperature of the third calcination is 500-600°C and the holding time is 1-2 h.

[0036] According to another aspect of the present invention, a solid-state battery anode material is provided, which is prepared according to the method described above.

[0037] According to certain preferred embodiments of the present invention, the particle size of the particles in the solid-state battery anode material is in the range of 80-300 nm.

[0038] According to certain preferred embodiments of the present invention, the particles in the solid-state battery anode material have, from the inside out, a silicon-titanium-zirconium composite core, a nitrogen-boron co-doped carbon intermediate layer, and a lithium-aluminum-phosphorus doped surface layer.

[0039] According to certain preferred embodiments of the present invention, the volume expansion rate of the solid-state battery anode material is not higher than 80%.

[0040] According to certain preferred embodiments of the present invention, the initial discharge specific capacity of the solid-state battery anode material is 2500-3000 mAh / g, and the initial coulombic efficiency is not less than 90%.

[0041] According to certain preferred embodiments of the present invention, the solid-state battery anode material retains a capacity of not less than 88% after 1000 cycles.

[0042] According to certain preferred embodiments of the present invention, the solid-state battery anode material exhibits a strength of no more than 50 Ω•cm in standard electrochemical tests simulating battery interface characteristics (using liquid electrolyte). 2 The low interfacial charge transfer impedance indicates that its surface has excellent stability and low reactivity, suggesting its great potential to form low-impedance interfaces with a variety of solid electrolytes.

[0043] According to certain preferred embodiments of the present invention, the solid-state battery anode material is used in all-solid-state lithium-ion batteries.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] 1. Multi-layer synergistic expansion suppression: Through a multi-layer structure of "silicon-titanium-zirconium composite core, nitrogen-boron co-doped carbon intermediate layer and lithium-aluminum-phosphorus-doped surface layer", multi-metal co-doping adjusts the lattice, porous carbon shell buffers stress, and interface layer flexibly releases strain, the volume expansion rate is controlled within 80%.

[0046] 2. Synergistic enhancement of electron and ion conduction: Nitrogen-boron co-doping significantly improves electronic conductivity (≥100 S / m), while the lithium-aluminum-phosphorus-doped surface provides high ion conductivity (≥1×10⁻⁶ S / m). -3 (S / cm) enables rapid charge transfer.

[0047] 3. Optimized interface compatibility: The interface layer has good chemical compatibility with the solid electrolyte, suppressing side reactions.

[0048] 4. Excellent overall performance: initial discharge specific capacity reaches 2500–3000 mAh / g, initial coulombic efficiency ≥90%, capacity retention rate ≥88% after 1000 cycles, and capacity retention rate ≥85% at 5C rate.

[0049] 5. Simplified process and controllable cost: It adopts mature processes such as hydrothermal and calcination, the raw materials are readily available, and there is no need for expensive equipment and rare elements, making it easy to scale up production. Attached Figure Description

[0050] The accompanying drawings are provided in this specification to more clearly explain the technical solutions of the present invention; however, the art is not limited thereto.

[0051] Figure 1 A flowchart illustrating the preparation process of a solid-state battery anode material according to the present invention is shown.

[0052] Figure 2 Transmission electron microscope (TEM) images of the products at different stages of the preparation of solid-state battery anode material in Example 1 are shown, wherein: a is a TEM image of silicon-titanium-zirconium composite nanoparticles obtained in step (3); b is a TEM image of core-shell structured composite particles obtained in step (6); and c is a TEM image of solid-state battery anode material obtained in step (8).

[0053] Figure 3 The X-ray diffraction (XRD) pattern of the solid-state battery anode material prepared in Example 1 is shown. Detailed Implementation

[0054] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It will be understood that other embodiments may be implemented without departing from the scope or spirit of the invention. Therefore, the following detailed description is non-limiting.

[0055] Unless otherwise specified, all figures used in this specification to represent characteristic dimensions, quantities, and physical properties should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters listed in the foregoing specification are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired properties using the teachings disclosed herein.

[0056] As mentioned above, silicon-based anodes suffer from significant volume expansion (up to 300%) during charging and discharging, leading to structural pulverization and active material shedding. Furthermore, the material's electronic conductivity and ion transport performance are difficult to balance, limiting rate and fast charging capabilities. Poor interface compatibility between the anode and the solid electrolyte results in high interface impedance, affecting lithium-ion transport efficiency. Additionally, some high-performance materials, such as alloy anodes, are costly and have complex manufacturing processes, hindering industrialization. This invention achieves a comprehensive improvement in high capacity, low expansion, superior interface, and low cost through multilayer composite structures and synergistic modification via elemental doping. This invention aims to solve the above problems.

[0057] Specifically, according to one aspect of the present invention, a method for preparing a solid-state battery anode material is provided, the method comprising the following steps:

[0058] (1) Add nano-silicon powder, titanium tetrachloride and zirconium tetrachloride to anhydrous ethanol, add a dispersant, and ultrasonically disperse to obtain a mixed suspension, wherein the total weight of nano-silicon powder, titanium tetrachloride and zirconium tetrachloride is 100%, the nano-silicon powder accounts for 80-95%, the titanium tetrachloride accounts for 2-12%, and the zirconium tetrachloride accounts for 1-8%;

[0059] (2) The mixed suspension was reacted with a reducing agent in a high-pressure reactor to obtain a silicon-titanium-zirconium composite precursor;

[0060] (3) The silicon-titanium-zirconium composite precursor was calcined in an inert atmosphere to obtain silicon-titanium-zirconium composite nanoparticles.

[0061] (4) The silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid are dispersed in deionized water to obtain a particle suspension, wherein, based on the total weight of the silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid as 100%, the silicon-titanium-zirconium composite nanoparticles account for 30-50%, glucose accounts for 40-60%, urea accounts for 5-10%, and boric acid accounts for 2-5%;

[0062] (5) The particulate suspension is subjected to a hydrothermal reaction to obtain a core-shell precursor;

[0063] (6) The core-shell precursor is subjected to a second calcination in a reducing atmosphere to obtain core-shell structured composite particles;

[0064] (7) The core-shell composite particles are mixed and ground with lithium carbonate, alumina and ammonium dihydrogen phosphate to obtain a mixed powder, wherein, based on the total weight of the core-shell composite particles, lithium carbonate, alumina and ammonium dihydrogen phosphate as 100%, the core-shell composite particles account for 90-95%, lithium carbonate accounts for 3-6%, alumina accounts for 1-3%, and ammonium dihydrogen phosphate accounts for 1-2%;

[0065] (8) The mixed powder is subjected to a third calcination under an inert atmosphere to obtain the solid battery anode material.

[0066] Figure 1 A flowchart illustrating the preparation process of a solid-state battery anode material according to the present invention is shown, specifically including the following steps:

[0067] S1: Add silicon powder, titanium tetrachloride and zirconium tetrachloride to ethanol, add dispersant, and disperse to obtain a mixed suspension;

[0068] S2: React the mixed suspension with a reducing agent to obtain a silicon-titanium-zirconium composite precursor;

[0069] S3: The silicon-titanium-zirconium composite precursor is first calcined to obtain silicon-titanium-zirconium composite nanoparticles;

[0070] S4: Disperse silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid in water to obtain a particle suspension;

[0071] S5: Perform a hydrothermal reaction on the particulate suspension to obtain a core-shell precursor;

[0072] S6: The core-shell precursor is subjected to a second calcination to obtain core-shell structured composite particles;

[0073] S7: Mix and grind the core-shell structured composite particles with lithium carbonate, alumina and ammonium dihydrogen phosphate to obtain a mixed powder;

[0074] S8: The mixed powder is subjected to a third calcination.

[0075] Specifically, step (1) is the initial step in constructing the silicon-titanium-zirconium composite core. The core of this step lies in achieving uniform premixing of nano-silicon, titanium source (TiCl4), and zirconium source (ZrCl4) at the molecular / nanoscale using a solution method. Nano-silicon powder (preferably with a particle size of 20-50 nm) is used as the main component, and its large specific surface area is beneficial to the subsequent formation of the silicon-titanium-zirconium composite precursor. Titanium tetrachloride and zirconium tetrachloride are added as sources of titanium and zirconium metal elements. Tetrachlorides are chosen because they have good solubility in ethanol and can rapidly hydrolyze to form active species such as Ti(OH)4 and Zr(OH)4, which are uniformly adsorbed or coated on the surface of nano-silicon particles. The nano-silicon powder accounts for 80-95%, ensuring that the material has a high theoretical capacity potential close to that of pure silicon; titanium tetrachloride accounts for 2-12%, and zirconium tetrachloride accounts for 1-8%. The introduction of titanium (Ti) aims to utilize its formation of titanium silicide (such as TiSi2) phase with silicon, which has good electronic conductivity and certain mechanical strength, helping to improve the overall conductivity of the core and partially buffer stress. The introduction of zirconium (Zr) has multiple functions: on the one hand, Zr can also form silicides with Si, but its more important role is that ZrO2 or zirconium-containing species segregate at grain boundaries during subsequent high-temperature processing, playing a "pinning" role and refining the grains. Simultaneously, Zr... 4+ The relatively large ionic radius of silicon allows its doping to induce lattice distortion, increasing the diffusion channels for lithium ions. The synergistic doping of Ti and Zr effectively modulates the lattice parameters of silicon, reducing anisotropic strain during lithium insertion / extraction and suppressing volume expansion at its source. Preferably, the nano-silicon powder comprises 85-90%, titanium tetrachloride 5-10%, and zirconium tetrachloride 3-5%. Within this preferred range, optimal conductivity enhancement and lattice modulation can be achieved while maintaining high capacity.

[0076] Anhydrous ethanol is used as the solvent because its moderate polarity allows for good dissolution and dispersion of the raw materials, and it facilitates subsequent processing. The weight ratio of the total raw materials to anhydrous ethanol is controlled between 1:3 and 1:6. A dispersant is added, preferably polyvinylpyrrolidone (PVP), whose long-chain molecules can effectively prevent the aggregation of nanoparticles through steric hindrance, ensuring the stability of the suspension. The weight ratio of the total raw materials to the dispersant is preferably between 10:1 and 20:1. This ratio ensures good dispersion while avoiding the introduction of excessive carbon impurities or pore blockage during subsequent high-temperature processing due to excessive dispersant. Ultrasonic dispersion is used to further break up soft agglomerates using the cavitation effect, obtaining a highly uniform mixed suspension, which is a prerequisite for obtaining a silicon-titanium-zirconium composite precursor with uniform composition.

[0077] Step (2) is a conversion step for preparing the silicon-titanium-zirconium composite precursor via a solvothermal reduction reaction. The homogeneous suspension obtained in step (1) is transferred to a high-pressure reactor, and a strong reducing agent is added. Sodium borohydride (NaBH4) is preferred as the reducing agent due to its strong reducing power, capable of reducing Ti under solvothermal conditions. 4+ and Zr 4+ The amount of sodium borohydride added is 3-5 times the total molar amount of titanium tetrachloride and zirconium tetrachloride. This excess factor ensures that Ti... 4+ and Zr 4+ The material is fully reduced, and the alkaline environment generated by the hydrolysis of excess NaBH4 also facilitates the reaction. The reaction temperature is controlled at 180-220℃, and the reaction time is 12-24 h. Under these mild temperatures and sufficient time, the reduction, nucleation, growth, and preliminary solid-phase diffusion processes are fully carried out, forming amorphous or low-crystallinity silicon-titanium-zirconium composite precursors with highly uniform composition and maintaining nanoscale morphology.

[0078] Step (3) involves the crystallization and densification of the silicon-titanium-zirconium composite precursor through a first calcination. The amorphous precursor obtained in step (2) is subjected to high-temperature heat treatment in an inert atmosphere (such as argon). The temperature of the first calcination is 800-1000℃, and the holding time is 2-4 h. At this high temperature, organic matter (such as residual dispersants, alcohols, etc.) in the precursor is removed by pyrolysis, and the amorphous phase crystallizes. Silicon, titanium, and zirconium atoms diffuse sufficiently to form silicon-titanium-zirconium composite nanoparticles with a specific crystal structure. By controlling the calcination temperature and time, the crystallinity, grain size, and final particle size of the silicon-titanium-zirconium composite nanoparticles can be controlled. The particle size of the silicon-titanium-zirconium composite nanoparticles is preferably 50-200 nm. This size range utilizes the short-range ion diffusion advantage of nanomaterials and avoids, to a certain extent, the severe agglomeration of excessively small nanoparticles and the side reactions caused by excessively high surface area. Compared with pure silicon nanoparticles, this core has a higher modulus and a more stable structure, providing a robust "skeleton" for the entire composite particle.

[0079] Step (4) is to prepare the reaction system for constructing a nitrogen-boron co-doped carbon intermediate layer. The silicon-titanium-zirconium composite nanoparticles obtained in step (3) are used as the "core" and dispersed together with a carbon source (glucose), a nitrogen source (urea), and a boron source (boric acid) in deionized water. Glucose serves as the main carbon source and carbonizes to form a carbon shell during subsequent hydrothermal and calcination processes. Urea serves as a nitrogen source, achieving nitrogen doping during carbonization, and its hydrolysis produces ammonia gas, which creates an alkaline environment and acts as a mild reducing agent and pore-forming agent. Boric acid provides the boron source for boron doping. The silicon-titanium-zirconium composite nanoparticles account for 30-50%, glucose for 40-60%, urea for 5-10%, and boric acid for 2-5%. This ratio ensures sufficient carbon source to form a continuous and appropriately thick coating layer, while providing adequate amounts of nitrogen and boron atoms for doping. Preferably, the silicon-titanium-zirconium composite nanoparticles account for 35-40%, glucose for 48-55%, urea for 6-8%, and boric acid for 2-4%. Within this preferred range, a carbon precursor coating layer of moderate thickness, uniform doping, and good bonding with the core can be formed. The weight ratio of the total raw material to deionized water is controlled between 1:3 and 1:5 to ensure that the system has suitable fluidity, facilitating uniform mixing and hydrothermal reaction.

[0080] Step (5) involves in-situ polymerization and coating of carbon precursors onto the core surface of silicon-titanium-zirconium composite nanoparticles via a hydrothermal reaction. The particle suspension from step (4) is placed in a high-pressure reactor and reacted at 160-200℃ for 8-12 h. Under these hydrothermal conditions, glucose undergoes dehydration and polymerization reactions, gradually forming polymeric carbon precursors (such as hydroxymethylfurfural polymers); urea decomposes to produce nitrogen-containing species (such as cyanate and ammonia); and boric acid also participates in the reaction. These species are generated in the solution system and, due to intermolecular forces or chemical bonds, are uniformly deposited and coated onto the surface of the dispersed silicon-titanium-zirconium composite nanoparticles, forming a preliminary core-shell structure precursor. The mildness and self-assembly characteristics of the hydrothermal process result in a uniform and dense coating layer with good physical or chemical bonding with the core, laying the foundation for obtaining a high-quality carbon shell.

[0081] Step (6) involves carbonizing, doping, and pore-forming the core-shell precursor through a second calcination, ultimately forming a nitrogen-boron co-doped carbon intermediate layer with a porous structure. The core-shell precursor obtained in step (5) is then heat-treated in a reducing atmosphere. The reducing atmosphere is preferably a mixture of argon and hydrogen, with a volume ratio of argon to hydrogen of 8:1 to 10:1. Hydrogen, as a mild reducing agent, can inhibit excessive graphitization of carbon materials at high temperatures (forming hard carbon), promote the formation of more defects and active sites, help remove impurity oxygen, and participate in the pore-forming process. The temperature of the second calcination is 700-900℃, and the holding time is 3-5 h. At this temperature, the carbon precursor undergoes carbonization to form a conductive carbon layer; nitrogen-containing species produced by urea decomposition and boron-containing species produced by boric acid decomposition are in situ doped into the carbon framework to form nitrogen-boron co-doped carbon. The doped nitrogen atoms (mainly pyridine nitrogen and graphitic nitrogen) and boron atoms can alter the electronic structure of the carbon layer, significantly improving its electronic conductivity and providing more adsorption / desorption active sites for lithium ions. Simultaneously, the decomposition of intermediate products formed during the hydrothermal stage and the action of hydrogen gas generate abundant nanopores within the carbon layer. The surface of the core-shell composite particles possesses a porous structure with a porosity of 20-30% and a pore size of 2-5 nm. This moderate porosity and nanoscale pore size offer multiple benefits: firstly, the pores provide a buffer space, effectively accommodating the volume expansion of the silicon-titanium-zirconium composite core during cycling, releasing stress, and preventing structural breakage; secondly, the abundant nanopores greatly increase the specific surface area and electrode / electrolyte contact area, facilitating electrolyte wetting and rapid lithium ion transport; finally, the porous structure reduces the overall material weight, contributing to improved specific capacity. The nitrogen-boron co-doped porous carbon intermediate layer formed in this step constitutes the second layer of the composite particles, possessing excellent conductivity, mechanical buffering, and ion transport capabilities.

[0082] Step (7) is the premixing step for the raw materials used to construct the lithium-aluminum-phosphorus doped surface layer. The core-shell composite particles obtained in step (6) are mechanically mixed and ground with lithium carbonate (Li2CO3), alumina (Al2O3), and ammonium dihydrogen phosphate (NH4H2PO4). The core-shell composite particles comprise 90-95%, lithium carbonate 3-6%, alumina 1-3%, and ammonium dihydrogen phosphate 1-2%. Preferably, the core-shell composite particles comprise 92-94%, lithium carbonate 4-5%, alumina 1-2%, and ammonium dihydrogen phosphate 1-1.5%. This ratio ensures that the surface modification material is sufficient to form a continuous and effective functional layer, while avoiding excessive addition that would result in a low proportion of active material in the inner layer, affecting the overall capacity. Lithium carbonate provides the lithium source, alumina provides the aluminum source, and ammonium dihydrogen phosphate provides the phosphorus and nitrogen sources. By using high-energy ball milling and other mixing and grinding methods, these powder raw materials are uniformly mixed at the nanoscale, ensuring that a full and uniform solid-phase reaction can occur during subsequent heat treatment, forming a surface modification layer with consistent composition.

[0083] Step (8) achieves in-situ synthesis and firm bonding of the surface-modified layer through a third calcination. The mixed powder obtained in step (7) is subjected to low-temperature heat treatment under an inert atmosphere (such as argon). The temperature of the third calcination is 500-600℃, and the holding time is 1-2 h. This temperature is much lower than the decomposition temperature of the carbon layer, but sufficient to initiate a solid-phase reaction between lithium carbonate and ammonium dihydrogen phosphate, which may generate lithium-phosphorus oxides, lithium phosphate, or their complexes with aluminum (such as LiAlO2, Li3PO4, AlPO4, or their symbiotic phases). At the same time, alumina nanoparticles may partially participate in the reaction or be uniformly dispersed in the generated lithium-phosphorus compound matrix. This process forms a uniform, lithium, aluminum, and phosphorus-rich doped surface layer on the outermost layer of the core-shell structured composite particles. This surface layer has multiple functions: First, its composition has a certain degree of chemical compatibility with common oxide or sulfide solid electrolytes (such as LLZO, LATP, LGPS, etc.), which can reduce interfacial side reactions; Second, the lithium-phosphorus compounds in this surface layer usually have good lithium-ion conductivity and can serve as an "artificial solid electrolyte interface (ASEI)," greatly optimizing the transport path of lithium ions from the bulk electrolyte to the interior of the negative electrode material and reducing interfacial impedance; Third, the introduction of aluminum can enhance the mechanical strength and thermal stability of this surface layer, further protecting the internal structure. This low-temperature calcination process also allows the surface layer to form certain chemical bonds or close contacts with the underlying nitrogen-boron co-doped carbon layer, forming a stable three-layer integrated structure.

[0084] In summary, through the design and synergy of the above eight steps, this invention successfully prepared a composite anode material with a unique triple structure of "silicon-titanium-zirconium composite core / nitrogen-boron co-doped porous carbon intermediate layer / lithium-aluminum-phosphorus doped surface layer". The particle size of the solid-state battery anode material is in the range of 80-300 nm, combining the kinetic advantages of nanomaterials and the structural stability of micromaterials. This material achieves a functional gradient design from the inside out: the core provides high capacity and structural stability; the intermediate layer achieves enhanced conductivity, stress buffering, and rapid ion transport; and the surface layer optimizes interface compatibility and ion conduction. The final material exhibits comprehensive performance with a volume expansion rate of no more than 80%, an initial discharge specific capacity of 2500-3000 mAh / g, an initial coulombic efficiency of no less than 90%, and a capacity retention rate of no less than 88% after 1000 cycles, making it particularly suitable for all-solid-state lithium-ion batteries with extremely high requirements for energy density, safety, and cycle life.

[0085] The present invention will now be described in more detail with reference to embodiments. It should be noted that these descriptions and embodiments are intended to facilitate understanding of the present invention and are not intended to limit the invention.

[0086] Example

[0087] In this invention, unless otherwise specified, all reagents used are commercially available products and are used directly without further purification. Furthermore, "%" refers to "weight %" and "parts" refers to "parts by weight".

[0088] Table 1 below lists specific information about the raw materials used in the embodiments and comparative examples of the present invention.

[0089]

[0090] Table 2 below lists specific information about the experimental equipment used in the embodiments and comparative examples of the present invention.

[0091]

[0092] Performance testing methods

[0093] (a) Volume expansion rate

[0094] The volume expansion rate of the negative electrode material samples prepared in the following embodiments and comparative examples was tested according to the method described below.

[0095] Referring to the national standard GB / T 44027.2-2024 "Determination of Carbon Materials - Part 2: Determination of Expansion Rate", the volume expansion rate during electrochemical cycling was tested according to the following steps: A slurry was prepared by mixing the negative electrode material sample, conductive carbon black, and polyvinylidene fluoride (PVDF) at a mass ratio of 90:5:5, and uniformly coated onto a 9 μm thick copper foil current collector. After vacuum drying at 120℃, the electrode was compacted to a set density using a roller press and then cut into 14 mm diameter discs. The thickness was measured at the center of the electrode and at four evenly distributed points using a high-precision digital micrometer (accuracy ±1 μm), and the arithmetic mean was taken as the initial thickness D0. In a glove box filled with argon gas (purity ≥99.999%), using this electrode as the working electrode and a lithium metal sheet as the counter electrode, sufficient electrolyte (1.0 mol / L LiPF6 EC / DMC / EMC solution, volume ratio 1:1:1) was injected to assemble a CR2032 coin cell. The cell was then placed in a constant temperature environment of 25.0±1.0℃ and tested at a 0.1C rate from 0.005 to 1.500 V (vs. Li). + Within the / Li) voltage range, 1000 charge-discharge cycles were performed. After the cycle, the battery was disassembled, the electrodes were cleaned with anhydrous ethanol and dried, and the thickness was measured again at the same five points. The average value was taken to obtain the post-cycle thickness D1.

[0096] The volume expansion rate (η, expressed as a percentage) is calculated using the following formula:

[0097] η = [(d1 – d0) / d0] × 100%

[0098] (ii) First discharge specific capacity

[0099] The negative electrode material samples prepared in the following embodiments and comparative examples were subjected to initial discharge specific capacity tests according to the methods described below.

[0100] Referring to the national standard GB / T 44027.1-2024 Determination of Carbon Materials - Part 1: Determination of Initial Discharge Specific Capacity, Initial Coulombic Efficiency and Capacity Retention Rate at Different Rates, the initial discharge specific capacity was tested according to the following steps: The negative electrode material sample was used as the only active material component, and it was uniformly mixed with conductive carbon black and polyvinylidene fluoride (PVDF) binder at a mass ratio of 90:5:5 (i.e., the mass ratio of active material in the electrode sheet was 90%). N-methylpyrrolidone (NMP) was added to prepare a slurry, which was coated on a copper foil current collector. After vacuum drying at 120°C for 12 hours, it was cut into circular electrode sheets with a diameter of 12 mm as working electrodes. In an argon-filled glove box (water and oxygen content both <0.1 ppm), a CR2032 coin cell was assembled using lithium metal sheets as the counter and reference electrodes, a ethylene carbonate / diethyl carbonate / methyl ethyl carbonate (volume ratio 1:1:1) solution containing 1.0 mol / L LiPF6, and a Celgard 2400 separator. The assembled cell was placed in a constant temperature chamber at 25.0 ± 0.5℃ and tested using a battery testing system (Blue Electric CT3001A) from 0.005 V to 1.500 V (vs. Li). + Within the voltage range of / Li), a constant current charge of 0.1C is applied to the upper limit voltage, followed by constant voltage charging until the current drops to 0.01C. After resting for 5 minutes, a constant current discharge is performed at the same 0.1C rate to the lower limit voltage. The initial discharge capacity is recorded and divided by the mass of the negative electrode material sample (i.e., the composite particle material prepared in the embodiments or comparative examples of this application) in the electrode sheet to obtain the initial discharge specific capacity, in mAh / g.

[0101] (III) First Coulomb Efficiency

[0102] The coulombic efficiency of the anode material samples prepared in the following embodiments and comparative examples was first tested according to the method described below.

[0103] The test was conducted in accordance with the national recommended standard GB / T 44027.1-2024, "Determination of Carbon Materials - Part 1: Determination of Initial Discharge Specific Capacity, Initial Coulombic Efficiency, and Capacity Retention Rate at Different Discharge Rates". The specific test methods and procedures are as follows: The negative electrode material sample, conductive carbon black, and polyvinylidene fluoride (PVDF) binder were uniformly mixed at a mass ratio of 90:5:5. N-methylpyrrolidone (NMP) solvent was added to prepare a slurry, which was then coated onto a clean copper foil current collector. The electrode was then dried in a vacuum oven at 120℃ for 12 hours to remove the solvent. After rolling, it was punched into a circular electrode sheet with a diameter of 12 mm to serve as the working electrode. In a glove box filled with high-purity argon gas (water and oxygen content both <0.1 ppm), using the electrode sheet as the working electrode and a lithium metal sheet as the counter and reference electrodes, an electrolyte (1.0 mol / L LiPF6 EC / DMC / EMC solution, volume ratio 1:1:1) was injected, and a polypropylene composite separator was used to assemble a CR2032 coin cell. The assembled cell was placed in a constant temperature environment of 25.0±1.0℃, and a Blue Electric CT3001A battery testing system was used to test the cells from 0.005 V to 1.500 V (relative to Li). + Within the voltage range of / Li), the first charge-discharge cycle test was performed at a constant current at a rate of 0.1C. The initial charge capacity (Q) was recorded. 充电 ) and first discharge capacity (Q 放电 The initial Coulomb efficiency (η) is calculated using the following formula:

[0104] η = (Q 放电 / Q 充电 )× 100%.

[0105] (iv) Capacity retention rate after 1000 cycles

[0106] The negative electrode material samples prepared in the following embodiments and comparative examples were subjected to a 1000-cycle capacity retention test according to the method described below.

[0107] Specifically, the test was conducted according to the relevant provisions of the national standard GB / T 37207-2018 "Methods for Testing the Electrochemical Performance of Lithium Nickel Cobalt Manganese Oxide - Discharge Platform Capacity Ratio and Cycle Life". The specific test steps are as follows: First, electrode sheets were prepared and coin cell half-cells were assembled according to the method described in "Initial Coulombic Efficiency Determination". The assembled battery was placed in a constant temperature environment of 25.0±1.0℃, and the battery testing system was used to test the battery at a voltage of 0.005 V to 1.500 V (relative to Li). +Within the voltage window of / Li), continuous constant current charge-discharge cycle tests were performed at a 1C rate. The discharge capacity was recorded in each cycle. The discharge capacity of the 3rd cycle was used as the initial capacity (C0). After 1000 consecutive charge-discharge cycles, the discharge capacity of the 1000th cycle (C0) was recorded. 1000 The capacity retention rate (R) after 1000 cycles is calculated using the following formula:

[0108] R = (C 1000 / C0) × 100%.

[0109] (v) Interface impedance

[0110] The interfacial impedance of the negative electrode material samples prepared in the following embodiments and comparative examples was tested according to the method described below.

[0111] The tests were conducted in accordance with the national recommended standard GB / T 40007-2021 General Rules for Contact Measurement of Resistivity of Nanomaterials in Nanotechnology and the general test rules for electrochemical impedance spectroscopy. The specific test steps are as follows: The negative electrode material sample was prepared as the working electrode, using the same preparation method as described in the "First Coulombic Efficiency Determination". In a glove box filled with high-purity argon (water and oxygen content both <0.1 ppm), the working electrode, lithium metal counter electrode, reference electrode, liquid electrolyte (1.0 mol / L LiPF6 EC / DMC / EMC solution), and separator were assembled into a CR2032 coin cell. The assembled cell was allowed to stand at 25.0±1.0℃ for 12 hours to achieve interface stability. Subsequently, using an electrochemical workstation (CHI760E), a sinusoidal AC voltage perturbation with a frequency range of 0.01 Hz to 1 MHz and an amplitude of 5 mV was applied under the open-circuit voltage condition of the cell, and electrochemical impedance spectroscopy was performed. The obtained Nyquist plot data was fitted using software such as ZView, employing an equivalent circuit model (R(QR)(QR) model) that represents the charge transfer process at the electrode / electrolyte interface. From the fitting results, the numerical value representing the interfacial charge transport impedance between the electrode material and the electrolyte was directly extracted and denoted as the interfacial impedance, with units of Ω•cm. 2 .

[0112] It should be noted that this test was conducted using a liquid electrolyte to assess the electrochemical stability of the negative electrode material surface and the ease of interfacial charge transfer using a standard and controllable method. This is an important indicator for characterizing the intrinsic interfacial properties of the material. The test results show that the material of this invention can form a stable electrode / electrolyte interface with low impedance. This provides an important material basis and positive reference for constructing a good interface with solid electrolytes (such as oxide-type LLZO, LATP, sulfide-type LPS, LGPS, or polymer electrolytes) in solid-state batteries. The interfacial impedance value in a specific solid-state battery system will depend on the type of solid electrolyte selected and the specific integration process, but this is beyond the scope of the characterization of the material itself in this application.

[0113] Furthermore, it should be noted that the electrochemical performance data (including specific capacity, coulombic efficiency, cycle life, and interfacial impedance) of all embodiments and comparative examples of this invention were tested in coin half-cells using a liquid electrolyte (1.0 mol / L LiPF6 EC / DMC / EMC solution). This testing system is a standard testing method commonly used in the field of lithium-ion battery material research and development (see national standard GB / T 44027.1-2024, etc.). Its purpose is to: ① eliminate interference from battery manufacturing processes (such as full-cell assembly and solid electrolyte membrane preparation) and fairly and accurately evaluate the intrinsic electrochemical performance of different materials; ② screen materials with high performance potential under controllable and comparable conditions. The electrode parameters used in this test (active material content 90%, areal loading approximately 1.0-2.0 mg / cm³) 2 The compacted density is approximately 1.0-1.2 g / cm³. 3 () is a commonly used range for laboratory evaluation of the performance of anode materials.

[0114] Example 1 (E1)

[0115] Example 1 includes the following steps:

[0116] Step (1): Preparation of mixed suspension

[0117] Weigh out 80g of nano-silicon powder, 12g of titanium tetrachloride, and 8g of zirconium tetrachloride. Add all the above raw materials together to a beaker containing 400g of anhydrous ethanol. Then, add 6g of polyvinylpyrrolidone as a dispersant to the system. Place the mixture in an ultrasonic disperser and sonicate continuously for 2 hours at a power of 300W and a water temperature of 25°C until a mixed suspension is obtained.

[0118] Step (2): Preparation of silicon-titanium-zirconium composite precursor

[0119] The mixed suspension obtained in step (1) was transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene. Based on the total molar amounts of titanium tetrachloride and zirconium tetrachloride in the system, three molar amounts of sodium borohydride (NaBH4) were calculated and weighed as a reducing agent, added to the reactor, and sealed. The reactor was placed in an oven and reacted at 180 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and washed three times alternately with anhydrous ethanol and deionized water. Finally, it was dried in a vacuum drying oven at 80 °C for 6 hours to obtain a black silicon-titanium-zirconium composite precursor.

[0120] Step (3): First calcination to prepare silicon-titanium-zirconium composite nanoparticles

[0121] The silicon-titanium-zirconium composite precursor powder obtained in step (2) was placed in an alumina boat in a tube furnace. High-purity argon gas (flow rate 200 mL / min) was continuously introduced into the furnace tube as an inert protective atmosphere. The furnace temperature was raised to 800°C at a heating rate of 5°C / min and held at this temperature for 2 hours. After calcination, the furnace was allowed to cool naturally to room temperature to obtain silicon-titanium-zirconium composite nanoparticles.

[0122] Step (4): Prepare particulate suspension

[0123] Weigh 30 grams of the silicon-titanium-zirconium composite nanoparticles obtained in step (3), 60 grams of glucose, 8 grams of urea, and 2 grams of boric acid. Add all the above materials together to a beaker containing 150 grams of deionized water. Place the beaker on a magnetic stirrer and stir continuously at 500 rpm for 4 hours to form a particle suspension.

[0124] Step (5): Hydrothermal reaction to prepare core-shell precursor

[0125] The particulate suspension obtained in step (4) was transferred to a 200 mL polytetrafluoroethylene-lined high-pressure reactor, sealed, and placed in an oven. A hydrothermal reaction was carried out at 160 °C for 12 hours. After the reaction was complete, the reactor was cooled, the reaction product was collected by centrifugation, washed three times with deionized water, and then vacuum-dried overnight at 80 °C to obtain the core-shell precursor.

[0126] Step (6): Second calcination to prepare core-shell structured composite particles

[0127] The core-shell precursor powder obtained in step (5) was placed in a tube furnace. A reducing gas mixture consisting of argon and hydrogen was introduced into the furnace tube, with a volume ratio of argon to hydrogen of 10:1 and a total flow rate of 200 mL / min. The temperature was increased to 700 °C at a rate of 3 °C / min and calcined at this temperature for 3 hours. After calcination, the mixture was cooled to room temperature under the protection of the mixed gas to obtain core-shell composite particles with a porous carbon shell. Characterization by nitrogen adsorption test showed that the carbon shell porosity was approximately 25% and the average pore size was approximately 3 nm.

[0128] Step (7): Mixing and grinding to prepare the final mixed powder

[0129] Weigh 90 grams of the core-shell composite particles obtained in step (6), and then add 6 grams of lithium carbonate, 3 grams of alumina nanoparticles, and 1 gram of ammonium dihydrogen phosphate in sequence. Place all the above powder materials together in the zirconium oxide grinding jar of a planetary ball mill, add an appropriate amount of anhydrous ethanol as the grinding medium, and ball mill at a speed of 300 rpm for 6 hours. After mixing, dry the slurry at 100°C and pass it through a 200-mesh sieve to obtain the mixed powder.

[0130] Step (8): Third calcination to obtain the negative electrode material

[0131] The mixed powder obtained in step (7) was placed in an alumina crucible and then placed in a tube furnace. High-purity argon gas (flow rate 150 mL / min) was introduced as a protective atmosphere. The mixture was heated to 500°C at a heating rate of 2°C / min and held at this temperature for 2 hours. After calcination, the mixture was cooled with the furnace, and the resulting block material was gently ground and passed through a 400-mesh sieve to obtain solid-state battery anode material 1.

[0132] The products from different stages of Example 1 were characterized by transmission electron microscopy (TEM). In addition, the solid-state battery anode material 1 prepared in Example 1 was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Figure 2 Transmission electron microscopy (TEM) images of the products at different stages are shown, where: a is a TEM image of the silicon-titanium-zirconium composite nanoparticles obtained in step (3); b is a TEM image of the core-shell structured composite particles obtained in step (6); and c is a TEM image of the solid-state battery anode material 1 with a three-layer structure (silicon-titanium-zirconium composite nanoparticle core, nitrogen-boron co-doped carbon intermediate layer, and lithium-aluminum-phosphorus-doped surface layer) obtained in step (8). Figure 3 The X-ray diffraction (XRD) pattern of the solid-state battery anode material 1 prepared in Example 1 is shown.

[0133] Furthermore, the solid-state battery anode material 1 was tested according to the methods described above for testing volume expansion rate, initial discharge specific capacity, initial coulombic efficiency, capacity retention after 1000 cycles, and interfacial impedance, and the results are shown in Table 4 below.

[0134] Examples 2-11 (E2-E11) and Comparative Examples 1-3 (CE1-CE3)

[0135] Examples 2-11 (E2-E11) and Comparative Examples 1-3 (CE1-CE3) were prepared in a manner similar to that of Example 1 to prepare solid-state battery anode materials 2-11 and comparative solid-state battery anode materials 1-3, the only difference being that the component types and ratios were changed as shown in Table 3 below.

[0136] Furthermore, the solid-state battery anode material 2-11 and the comparative solid-state battery anode material 1-3 were tested according to the methods described in detail above for testing volume expansion rate, initial discharge specific capacity, initial coulombic efficiency, capacity retention after 1000 cycles, and interfacial impedance, and the results are shown in Table 4 below.

[0137]

[0138]

[0139] As can be seen from the results in Tables 3 and 4 above, the solid-state battery anode materials obtained by the method of the present invention in Examples 1-11 (E1-E11) are significantly better than those in Comparative Examples 1-3 (CE1-CE3) that did not fully adopt the technical solution of the present invention in terms of key performance indicators such as volume expansion rate, first discharge specific capacity, first coulombic efficiency, long cycle capacity retention rate and interface impedance.

[0140] Specifically, regarding volume expansion control, the volume expansion rate of all materials in the embodiments was effectively suppressed to below 80%, with the optimal embodiment 11 reaching 60%, far lower than the typical expansion level of pure silicon anodes (such as 180% for CE1). This confirms that the "silicon-titanium-zirconium composite nanoparticle core" constructed in this invention regulates the lattice stress through multi-metal co-doping, while the "nitrogen-boron co-doped carbon intermediate layer" provides an effective buffer space. The synergistic effect of the two fundamentally alleviates the huge volume change of silicon during lithium intercalation.

[0141] In terms of electrochemical performance, the materials in the examples exhibit excellent high specific capacity characteristics, with initial discharge specific capacities generally exceeding 2500 mAh / g, reaching a maximum of 3000 mAh / g (E11), significantly higher than CE1 (1200 mAh / g) without titanium and zirconium and CE2 (1800 mAh / g) without boron co-doped carbon coating. Simultaneously, the initial coulombic efficiency of the examples is not less than 90%, indicating lower irreversible capacity loss. This is attributed to the uniform carbon coating layer and surface modification layer effectively suppressing side reactions in the electrolyte and excessive growth of the solid electrolyte interface (SEI).

[0142] Regarding long-term cycling stability, the materials in the examples all maintained a capacity retention of over 87% after 1000 charge-discharge cycles, with the best E11 reaching 97%, demonstrating excellent cycle life. In contrast, the comparative examples exhibited more rapid capacity decay. This is attributed to the unique core-shell-surface composite structure of this invention: the internal silicon-titanium-zirconium composite nanoparticle core is firmly bonded to the intermediate carbon layer, while the external lithium-aluminum-phosphorus doped surface layer has good compatibility with the solid electrolyte, jointly ensuring the integrity of the material structure and the stability of the interface during long-term cycling.

[0143] Regarding interface properties, the interfacial impedance of the materials in the examples is all below 52 Ω•cm. 2 The minimum is 30 Ω•cm 2 (E11), while the interface impedances of comparative examples CE1, CE2, and CE3 are as high as 150, 100, and 85 Ω•cm, respectively. 2 This significant difference confirms that the present invention, by introducing a lithium-aluminum-phosphorus doped surface layer, optimizes the interfacial contact and ion transport kinetics between the anode material and the solid electrolyte, thereby reducing the interfacial charge transfer resistance.

[0144] In summary, the comparison results between Examples 1-11 and Comparative Examples 1-3 demonstrate that the present invention, through a multilayer composite structure design of "silicon-titanium-zirconium composite nanoparticle core-nitrogen-boron co-doped carbon intermediate layer-lithium aluminum-phosphorus doped surface layer" and the corresponding preparation process, achieves effective suppression of volume expansion of silicon-based anodes, comprehensive improvement of electrochemical performance, and significant improvement of interfacial compatibility with solid electrolytes. The anode material provided by the present invention possesses high specific capacity, long cycle life, low interfacial impedance, and good process feasibility, with overall performance significantly superior to existing technologies, and has significant industrial application value.

[0145] Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from the spirit and scope of this disclosure. Therefore, if such modifications and variations fall within the scope of this invention, this disclosure is also intended to include such modifications and variations.

Claims

1. A method for producing a solid-state battery negative electrode material, characterized by, The preparation method includes the following steps: (1) Add nano-silicon powder, titanium tetrachloride and zirconium tetrachloride to anhydrous ethanol, add a dispersant, and ultrasonically disperse to obtain a mixed suspension, wherein the total weight of nano-silicon powder, titanium tetrachloride and zirconium tetrachloride is 100%, the nano-silicon powder accounts for 85-90%, the titanium tetrachloride accounts for 5-10%, and the zirconium tetrachloride accounts for 3-5%; (2) The mixed suspension was reacted with a reducing agent in a high-pressure reactor to obtain a silicon-titanium-zirconium composite precursor; (3) The silicon-titanium-zirconium composite precursor was calcined in an inert atmosphere to obtain silicon-titanium-zirconium composite nanoparticles. (4) The silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid are dispersed in deionized water to obtain a particle suspension, wherein, based on the total weight of the silicon-titanium-zirconium composite nanoparticles, glucose, urea and boric acid as 100%, the silicon-titanium-zirconium composite nanoparticles account for 35-40%, glucose accounts for 48-55%, urea accounts for 6-8%, and boric acid accounts for 2-4%; (5) The particulate suspension is subjected to a hydrothermal reaction to obtain a core-shell precursor; (6) The core-shell precursor is subjected to a second calcination in a reducing atmosphere to obtain core-shell structured composite particles; (7) The core-shell composite particles are mixed and ground with lithium carbonate, alumina and ammonium dihydrogen phosphate to obtain a mixed powder, wherein, based on the total weight of the core-shell composite particles, lithium carbonate, alumina and ammonium dihydrogen phosphate as 100%, the core-shell composite particles account for 92-94%, lithium carbonate accounts for 4-5%, alumina accounts for 1-2%, and ammonium dihydrogen phosphate accounts for 1-1.5%; (8) The mixed powder is subjected to a third calcination under an inert atmosphere to obtain the solid battery anode material.

2. The production method according to claim 1, characterized by, In step (2), the reaction temperature in the high-pressure reactor is 180-220℃ and the reaction time is 12-24 h.

3. The production method according to claim 1, characterized by, In step (3), the temperature of the first calcination is 800-1000℃, and the holding time is 2-4 h.

4. The production method according to claim 1, characterized by, In step (5), the temperature of the hydrothermal reaction is 160-200℃ and the reaction time is 8-12 h.

5. The production method according to claim 1, characterized by, In step (6), the second calcination temperature is 700-900℃ and the holding time is 3-5 h.

6. The production method according to claim 1, characterized by, In step (8), the temperature of the third calcination is 500-600℃, and the holding time is 1-2 h.

7. A solid-state battery anode material, characterized in that, The solid-state battery anode material is prepared by the method according to any one of claims 1-6.

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