Silicon negative electrode material, preparation method thereof, negative electrode sheet, and all-solid-state battery

Abstract

The application provides a silicon negative electrode material and a preparation method thereof, a negative electrode sheet and a full-solid-state battery, and relates to the technical field of batteries. The method comprises the following steps: mixing and processing a coated silicon-based material and a carbon source to obtain a coated semi-product, wherein the coated silicon-based material comprises nano-silicon particles, the carbon source is coated on the surface of the nano-silicon particles, and the mass of the carbon source is 1.0% to 2.5% of the mass of the nano-silicon particles; and then obtaining a final silicon negative electrode material based on the coated semi-product. Through the above method, the prepared silicon negative electrode material has a core-shell structure with nano-silicon particles as a core layer and a carbon source as a shell layer. The carbon coating layer can effectively inhibit the volume expansion of the nano-silicon particles during the charging and discharging process, effectively improve the structural stability, interface compatibility and electrochemical performance of the silicon negative electrode material, and thus improve the cycle life and safety of the full-solid-state battery.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a silicon anode material and its preparation method, an anode sheet, and an all-solid-state battery. Background Technology

[0002] Silicon-based anode materials are a core component of all-solid-state batteries, and their performance directly affects the energy density, cycle stability, and safety of these batteries. While nano-silicon can effectively mitigate volume expansion due to its size effect, its safety still needs improvement due to its direct contact with the electrolyte and high interfacial reactivity.

[0003] In existing technologies, the performance of nano-silicon materials is mainly improved by combining silicon with oxides or by coating silicon particles with porous carbon structures. Among them, silicon-oxygen composite materials reduce the volume expansion rate by introducing oxides, but suffer from problems such as low initial efficiency and poor cycle performance; while porous silicon-carbon composite materials provide buffer space for silicon expansion with porous carbon framework, but the preparation process requires sophisticated equipment (vacuum environment).

[0004] In summary, providing a silicon anode material with a simple preparation process that can effectively improve the cycle performance of all-solid-state batteries is an urgent technical problem to be solved. Summary of the Invention

[0005] This application provides a silicon anode material and its preparation method, anode sheet, and all-solid-state battery, which can effectively improve the structural stability, interfacial compatibility, and electrochemical performance of silicon anode material while simplifying the preparation process and reducing production costs, thereby improving the cycle life and safety of all-solid-state batteries.

[0006] In a first aspect, embodiments of this application provide a silicon anode material, including a coated silicon-based material, wherein the silicon-based material includes nano-silicon particles, and the surface of the nano-silicon particles is coated with a carbon source;

[0007] The mass of the carbon source is 1.0% to 2.5% of the mass of the nano-silicon particles.

[0008] In one possible implementation, the carbon source is coated onto the surface of the nano-silicon particles using a coating device;

[0009] And / or,

[0010] The filling volume of the nano-silicon particles is 1 / 3 to 1 / 2 of the effective volume of the coating device.

[0011] In one possible implementation, the carbon source is a resin-based carbon source or an asphalt-based carbon source.

[0012] Secondly, embodiments of this application provide a method for preparing a silicon anode material, the method comprising:

[0013] A coated silicon-based material and a carbon source are mixed in an inert gas environment to obtain a coated semi-finished product; wherein the silicon-based material comprises silicon nanoparticles, and the carbon source is coated on the surface of the silicon nanoparticles, with the mass of the carbon source being 1.0% to 2.5% of the mass of the silicon nanoparticles;

[0014] The silicon anode material is obtained from the coated semi-finished product.

[0015] In one possible implementation, the process of mixing the coated silicon-based material and the carbon source in an inert gas environment to obtain a coated semi-finished product includes:

[0016] The nano-silicon particles and carbon source are placed in a coating device and mixed in an inert gas environment to obtain the coated semi-finished product.

[0017] The filling volume of the nano-silicon particles is 1 / 3 to 1 / 2 of the effective volume of the coating device.

[0018] In one possible implementation, the carbon source is a resin-based carbon source or an asphalt-based carbon source.

[0019] In one possible implementation, obtaining the silicon anode material from the coated semi-finished product includes:

[0020] The coated semi-finished product is sintered in an inert gas environment using a sintering equipment to obtain sintered carbon-coated silicon particles.

[0021] The sintered carbon-coated silicon particles are sieved to obtain undersize and oversize particles.

[0022] The sieved material was identified as the silicon anode material;

[0023] The silicon anode material is obtained by depolymerizing the material on the sieve using a depolymerization device.

[0024] In one possible implementation, the depolymerization equipment during the depolymerization process includes at least one of a medium-sized material crusher, an air jet mill, a vertical mill, and a rod mill.

[0025] In one possible implementation, during the mixing process, the coating device includes a fusion shaping machine, and / or the mixing time is 3 min to 5 min, and / or the rotation speed of the coating device is 550 rpm to 650 rpm.

[0026] In one possible implementation, the sintering equipment is a low-temperature chamber furnace, and / or the sintering temperature is 450°C to 500°C, and / or the sintering time is 10h to 12h.

[0027] Thirdly, embodiments of this application provide a negative electrode sheet, comprising: a silicon negative electrode material as described in any of the possible methods of the first aspect above, or a silicon negative electrode material prepared by the methods described in the second aspect above and / or various possible methods of the second aspect.

[0028] Fourthly, embodiments of this application provide an all-solid-state battery, including the negative electrode sheet as described in the third aspect.

[0029] This application provides a silicon anode material, its preparation method, an anode sheet, and an all-solid-state battery. First, under inert gas protection, a coated silicon-based material is mixed with a carbon source to obtain a coated semi-finished product. The coated silicon-based material comprises silicon nanoparticles, and the carbon source coats the surface of the silicon nanoparticles, with the carbon source accounting for 1.0% to 2.5% of the mass of the silicon nanoparticles. Subsequently, the final silicon anode material is obtained based on this coated semi-finished product. The silicon anode material prepared by this method possesses a uniform and stable carbon coating layer on the surface of the silicon nanoparticles, which effectively improves the overall conductivity of the silicon anode material and buffers the large volume expansion of the silicon particles during battery cycling, inhibiting their breakage and aggregation. Ultimately, this significantly enhances the structural stability and electrochemical cycling performance of the silicon anode material, thereby improving the cycle performance, rate performance, and first-cycle coulombic efficiency of the all-solid-state battery. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0031] Figure 1 This is a schematic diagram of the structure of a silicon anode material provided in this application;

[0032] Figure 2 A flowchart illustrating a method for preparing a silicon anode material provided in this application. Figure 1 ;

[0033] Figure 3 A flowchart illustrating a method for preparing a silicon anode material provided in this application. Figure 2 .

[0034] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] The application background of this application is explained as follows:

[0037] Solid-state batteries, with their advantages of high specific energy, high operating voltage, fast charging and discharging speed, long cycle life, safety and no pollution, are gradually replacing traditional liquid lithium batteries. As the core technology of the next generation of high energy density energy storage devices, solid-state batteries are widely used in new energy vehicles, energy storage systems, aerospace and consumer electronics.

[0038] In the field of new energy vehicles, all-solid-state batteries, due to their high specific energy (>400Wh / kg) and high operating voltage (>4.5V), can significantly improve driving range and shorten charging time, while avoiding the safety hazards caused by liquid electrolyte leakage. In energy storage systems, the long cycle life (>2000 cycles) and wide temperature range adaptability (-30℃~60℃) of all-solid-state batteries make them an ideal choice for grid peak shaving and distributed energy storage.

[0039] Silicon-based anode materials, as core components of solid-state batteries, offer advantages such as high energy density and high compaction density. However, they also suffer from significant expansion, poor cycle performance, and unstable interface states. In recent years, research on high-capacity silicon anode materials has become a focal point in the development of all-solid-state batteries. Extensive market experience has demonstrated that the volume expansion (>300%) of silicon materials during charge and discharge, leading to structural pulverization, interface delamination, and increased ohmic impedance with the solid electrolyte, severely hinders the commercialization of all-solid-state batteries.

[0040] Currently, the most common commercially available silicon-based anode materials include silicon-oxygen, silicon-carbon, and nano-silicon. Silicon-oxygen was the first generation of silicon-based anode materials, primarily used to reduce volume expansion by introducing oxides into silicon. However, it suffers from low initial efficiency and poor cycle performance. Silicon-carbon optimizes the cycle performance of the silicon substrate by providing a buffer for silicon expansion through a porous carbon framework, for example, by constructing the carbon framework through chemical vapor deposition. However, this process requires sophisticated equipment (a vacuum environment is necessary), and isostatic pressing can easily damage the porous structure, leading to insufficient contact between the solid electrolyte and the anode interface and increased ohmic impedance. While nano-silicon can effectively alleviate volume expansion problems due to its size effect, its direct contact with the electrolyte results in high interfacial reactivity, necessitating further improvements in safety.

[0041] Therefore, providing a silicon anode material with a simple preparation process that can effectively improve the cycle performance of all-solid-state batteries is an urgent technical problem to be solved.

[0042] Based on the aforementioned technical problems, the inventors, during the research on the preparation of silicon-based anode materials, discovered that by mixing coated silicon-based materials (nano-silicon particles) with a carbon source under inert gas protection, a coated semi-finished product with a core-shell structure consisting of nano-silicon particles as the core layer and a carbon source as the shell layer is obtained. Subsequently, the coated semi-finished product is sintered at low temperature (≤500℃) to solidify the coating layer, followed by sieving. The material passing through the sieve is directly identified as the silicon anode material, and the material remaining on the sieve is depolymerized to obtain the silicon anode material. This silicon material preparation process is simple and can improve battery cycle life while maintaining the high capacity characteristics of silicon. Based on this, this application provides a silicon anode material, its preparation method, an anode sheet, and an all-solid-state battery.

[0043] The technical solution of this application and how it solves the above-mentioned technical problems will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0044] Figure 1 This is a schematic diagram of the structure of a silicon anode material provided in this application. The silicon anode material includes a coated silicon-based material and a carbon source.

[0045] like Figure 1 As shown, the silicon-based material comprises silicon nanoparticles, the surface of which is coated with a carbon source. The mass of the carbon source is 1.0% to 2.5% of the mass of the silicon nanoparticles.

[0046] Coated silicon-based materials refer to composite structural materials that use silicon or silicon-based compounds as the core substrate material and coat the surface of silicon-based particles with one or more layers of other functional materials through chemical or physical coating processes. These materials can effectively improve the problems of structural damage, electrode pulverization and cycle performance degradation caused by excessive volume effect during the charging and discharging process of pure silicon materials by the outer coating layer to constrain, protect and modify the internal silicon-based body. At the same time, they can also optimize the conductivity, structural stability and interface compatibility of silicon-based materials.

[0047] Silicon-based materials include nano-silicon particles, which are the core active material constituting the silicon anode material. Their particle size is typically between tens and hundreds of nanometers. Due to their extremely small size, nano-silicon exhibits greater expansion redundancy during battery charging and discharging, mitigating the structural damage caused by volume changes during lithium intercalation. It also demonstrates a higher theoretical specific capacity than traditional graphite, significantly improving the battery's energy density. Nano-silicon has a good specific surface area, providing a more sufficient contact interface when mixed with a carbon source, allowing the carbon source to more easily and uniformly adhere to the silicon particle surface, thus forming a continuous and dense coating layer.

[0048] Carbon source refers to the precursor or carbon material used to form a carbon layer on the surface of silicon nanoparticles. Its role is to enhance the electronic conductivity of silicon anode materials by forming a uniform carbon coating layer on the surface of silicon nanoparticles, while effectively buffering the volume changes of silicon during charging and discharging, thereby improving the structural stability of silicon anode materials and battery cycle performance.

[0049] In one possible implementation, the carbon source includes a resin-based carbon source or a pitch-based carbon source.

[0050] The carbon source includes liquid-phase coated carbon sources, which are carbon precursors that exist in liquid form or are soluble in solvents, allowing them to fully contact and uniformly disperse with silicon particles during the coating process. Their liquid state or solubility enables them to form a continuous and uniform coating on the silicon particle surface, which can be transformed into a dense carbon coating layer after subsequent heat treatment. In addition, carbon sources can also include solid-phase coated carbon sources, gas-phase carbon sources, etc.

[0051] Taking resin-based carbon sources as an example, they typically possess good film-forming properties, controllable structure, and high carbon residue. After dissolving or dispersing in a solvent, they can uniformly cover the surface of nano-silicon particles, forming a continuous and dense resin coating. After heat treatment and carbonization, they can be transformed into a carbon coating layer with certain flexibility and mechanical strength. Resin-based carbon sources can include phenolic resins (such as solutions of soluble phenolic resins and linear phenolic resins in solvents), epoxy resins and their prepolymers, furan resins, polyimide precursors (such as polyamic acid solutions), polyfuran methanol resins, polyacrylonitrile resin solutions soluble in organic solvents, and other carbonizable organic resins or resin solutions. These resins can undergo cross-linking, pyrolysis, and ultimately transformation into carbon materials during heat treatment, making them suitable as carbon sources for coating the surface of nano-silicon particles.

[0052] Taking asphalt-based carbon sources as an example, they typically possess high residual carbon content and good film-forming properties. During heating, they undergo stages such as softening, melting, cross-linking, and carbonization, forming a continuous and dense carbon coating layer at relatively low temperatures. Simultaneously, asphalt itself exhibits high aromaticity and a good tendency to graphitize, contributing to improved conductivity and structural stability of silicon anode materials. Asphalt-based carbon sources can include coal tar pitch, petroleum asphalt, mesophase asphalt, modified asphalt, and their solutions in solvents. During the coating process, these asphalt materials can uniformly cover the surface of nano-silicon particles through wetting, flow, and coating effects, forming an asphalt coating with a certain thickness and mechanical strength. After subsequent heat treatment and carbonization, they can be transformed into a structurally stable and highly conductive carbon coating layer, suitable as a carbon source for coating the surface of nano-silicon particles.

[0053] In one possible implementation, a carbon source is coated onto the surface of nano-silicon particles using a coating device; and / or, the loading volume of the nano-silicon particles is 1 / 3 to 1 / 2 of the effective volume of the coating device.

[0054] Coating equipment refers to devices used to uniformly coat the surface of nano-silicon particles with carbon sources. Its core function is to achieve full contact, uniform dispersion, and controllable coating between nano-silicon particles and carbon sources. Coating equipment typically includes stirred reactors, rotary kilns, fusion shaping machines, high-speed dispersers, ball mills, sand mills, spray dryers, and fluidized bed coating machines. These coating devices can use mechanical stirring, high-speed shearing, ball milling, or gas-solid-liquid multiphase flow fields to uniformly suspend nano-silicon particles in the carbon source and fully wet them with the carbon source, thereby forming a continuous coating layer.

[0055] Taking the fusion shaping machine as an example, it is a coating device that combines mechanical force and heat. Through the strong shearing force, impact force and friction force generated between the high-speed rotating rotor and stator, the nano-silicon particles are fully dispersed during the contact with the carbon source. At the same time, a uniform coating layer is formed on the surface of the nano-silicon particles. Under the combined action of mechanical force, the coating layer becomes denser, thereby achieving a high-quality coating effect.

[0056] The mass of the carbon source is 1.0% to 2.5% of the mass of the silicon nanoparticles. For example, the mass of the carbon source can be any value within the range of 1.0% to 2.5%, such as 1.0%, 1.4%, 1.6%, 2.0%, 2.3%, or 2.5% of the mass of the silicon nanoparticles. That is, when the mass fraction of the silicon nanoparticles is 1, the corresponding mass fraction of the carbon source can be 0.01, 0.014, 0.016, 0.02, 0.023, or 0.025, etc.

[0057] The filling volume of the nano-silicon particles is 1 / 3 to 1 / 2 of the effective volume of the coating equipment. The effective volume of the coating equipment refers to the effective space within its working chamber that can hold the material, generally ranging from a few liters to several hundred liters, suitable for different needs from small-scale laboratory research to large-scale industrial production. For example, the filling volume of the nano-silicon particles can be any value within the range of 1 / 3 to 1 / 2, such as 1 / 3, 2 / 5, 5 / 12, or 1 / 2 of the effective volume of the coating equipment.

[0058] The silicon anode material provided in this application includes a coated silicon-based material, comprising silicon nanoparticles coated with a carbon source. The carbon source accounts for 1.0% to 2.5% of the mass of the silicon nanoparticles. The carbon source is coated onto the surface of the silicon nanoparticles using a coating device, and the filling volume of the silicon nanoparticles is 1 / 3 to 1 / 2 of the effective volume of the coating device. This silicon anode material has a core-shell structure. The silicon nanoparticles, as the core material, undertake the main electrochemical reactions of lithium-ion insertion and extraction and provide high specific capacity. The coating layer formed by the carbon source, as the shell material, buffers the volume expansion of the silicon nanoparticles, improves electronic conductivity, and enhances interfacial compatibility with the solid electrolyte, ultimately achieving the technical effect of improving the cycle performance of the all-solid-state battery and extending its lifespan.

[0059] Figure 2 A flowchart illustrating a method for preparing a silicon anode material provided in this application. Figure 1 ,like Figure 2 As shown, the method includes:

[0060] S201: The coated silicon-based material and the carbon source are mixed in an inert gas environment to obtain a coated semi-finished product; wherein the silicon-based material includes nano-silicon particles, the carbon source is coated on the surface of the nano-silicon particles, and the mass of the carbon source is 1.0% to 2.5% of the mass of the nano-silicon particles.

[0061] In this step, the inert gas refers to a chemically inert gas. During the mixing process, it can be used to prevent the oxidation of the silicon nanoparticles under the localized high temperature or high specific surface area exposure conditions generated by mechanical mixing. Simultaneously, it prevents unnecessary oxidation, decomposition, or cross-linking reactions of the carbon source, thereby ensuring the cleanliness of the silicon nanoparticle surface and the stability of the carbon source, and ensuring the controllability and uniformity of the subsequent coating layer formation process. For example, the inert gas can be nitrogen, argon, helium, or neon.

[0062] In one possible implementation, the carbon source is a resin-based carbon source or an asphalt-based carbon source.

[0063] Its specific types, characteristics, and encapsulation mechanisms are described above. Figure 1 The examples have been described in detail and will not be repeated here.

[0064] In one possible implementation, nano-silicon particles and a carbon source are placed in a coating device and mixed in an inert gas environment to obtain a coated semi-finished product. The filling volume of the nano-silicon particles is 1 / 3 to 1 / 2 of the effective volume of the coating device.

[0065] For example, an inert gas is introduced into the chamber of the coating device, and nano-silicon particles, accounting for 1 / 3 to 1 / 2 of the effective volume of the coating device, are filled in. Then, a carbon source, accounting for 1.0% to 2.5% of the mass of the nano-silicon particles, is added. The nano-silicon particles and the carbon source are mixed in the coating device (fusion shaping machine) by extrusion. The nano-silicon particles appropriately agglomerate to form a core, and the carbon source, due to its liquid-phase flowability, uniformly adheres to the surface of the nano-silicon particles, thereby forming a thin and uniform coating layer on the surface of the nano-silicon particles. The filling volume of the nano-silicon particles can be 1 / 3, 3 / 8, 5 / 12, 11 / 24, or 1 / 2 of the effective volume of the coating device, etc., and the mass of the carbon source can be 1.0%, 1.2%, 1.5%, 1.7%, 1.9%, 2.2%, 2.4%, or 2.5% of the mass of the nano-silicon particles, etc. This method can reduce coating costs and improve coating efficiency. The final coated semi-finished product has a uniform core-shell structure, which is beneficial to improving the conductivity, structural stability and cycle performance of silicon anode materials in all-solid-state batteries.

[0066] In one possible implementation, during the mixing process, the coating equipment includes a fusion shaping machine, and / or the mixing time is 3 min to 5 min, and / or the rotation speed of the coating equipment is 550 rpm to 650 rpm.

[0067] The fusion shaping machine, through low-speed rotation and stirring, ensures sufficient contact between nano-silicon particles and the coated carbon source under a gentle mechanical force field. This promotes the uniform spreading and adhesion of the carbon source to the surface of the nano-silicon particles, while preventing breakage of the nano-silicon particles or uneven carbon layer distribution due to high shear forces. The mixing time refers to the duration of contact, agitation, and coating between the nano-silicon particles and the carbon source in the fusion shaping machine. Its length directly affects the degree of wetting of the carbon source on the surface of the nano-silicon particles, the uniformity of spreading, and the integrity of the coating layer. The rotation speed of the coating equipment refers to the number of rotations of the cylinder or stirring structure of the coating equipment (fusion shaping machine) per unit time. It directly determines the intensity of material agitation, contact frequency, and the magnitude of the mechanical forces acting on the material inside the equipment.

[0068] For example, the mixing time can be any value within the range of 3 min to 5 min, such as 3 min, 4 min, or 5 min, to ensure that the carbon source can form a continuous and uniform coating layer on the surface of the nano-silicon particles, without insufficient coating due to too short a time or unnecessary energy consumption and production efficiency reduction due to too long a time; the rotation speed of the coating equipment can be any value within the range of 550 rpm to 650 rpm, such as 550 rpm, 560 rpm, 600 rpm, 630 rpm, or 650 rpm. This rotation speed range can provide sufficient material turning and contact opportunities while maintaining low mechanical stress, which is conducive to maintaining the structural integrity of the nano-silicon particles and allowing the carbon source to slowly flow, wet, and form a dense pre-coating layer on the particle surface.

[0069] S202: Based on the coating of the semi-finished product, silicon anode material is obtained.

[0070] In order to form a stable, continuous coating layer with certain mechanical strength on the surface of nano-silicon particles by coating carbon source, and to prevent it from falling off, agglomerating or structurally damaged during subsequent processing, the coated semi-finished product is sintered and solidified. This not only enhances the mechanical strength and density of the carbon layer, but also effectively inhibits the volume expansion and agglomeration of nano-silicon particles during subsequent processing or electrochemical cycling, and significantly improves the structural stability and electrochemical performance of silicon anode materials.

[0071] The method for preparing silicon anode material provided in this application involves mixing nano-silicon particles with a carbon source under inert gas protection using a coating device. This allows the carbon source to uniformly adhere to the surface of the nano-silicon particles, forming a preliminary core-shell structured coated semi-finished product. The filling volume of the nano-silicon particles is 1 / 3 to 1 / 2 of the effective volume of the coating device, and the mass of the carbon source is 1.0% to 2.5% of the mass of the nano-silicon particles. Subsequently, the coated semi-finished product is sintered and solidified to transform the coating layer into a stable and dense carbon layer, ultimately obtaining the silicon anode material. This method achieves uniform, thin, and complete carbon coating at a relatively low cost. The prepared silicon anode material exhibits excellent structural stability and electrochemical performance during all-solid-state battery cycling.

[0072] Figure 3 A flowchart illustrating a method for preparing a silicon anode material provided in this application. Figure 2 ,like Figure 3 As shown, based on the above embodiments, in S202: according to the coated semi-finished product, a silicon anode material is obtained, specifically including:

[0073] S301: The coated semi-finished product is sintered in an inert gas environment using sintering equipment to obtain sintered carbon-coated silicon particles.

[0074] As mentioned in S202, sintering and solidifying the coated semi-finished product can effectively enhance the mechanical strength, density and interfacial bonding of the coating layer, thereby improving the structural stability and electrochemical performance of the silicon anode material.

[0075] In one possible implementation, the sintering equipment is a low-temperature chamber furnace, and / or the sintering temperature is 450°C to 500°C, and / or the sintering time is 10h to 12h.

[0076] Understandably, sintering temperature refers to the preset heating temperature during the sintering process, and sintering time refers to the duration for which the coated semi-finished product is kept heated at the preset sintering temperature. For example, the sintering temperature can be any value within the range of 450℃ to 500℃, such as 450℃, 460℃, 470℃, 485℃, 495℃, 498℃, or 500℃; the sintering time can be any value within the range of 10h to 12h, such as 10h, 11h, 11.5h, or 12h. By rationally selecting the sintering temperature and sintering time, it is possible to ensure that the carbon source is fully solidified and forms a stable amorphous carbon layer, while effectively preventing lattice phase transformation, grain growth, or structural damage of the nano-silicon particles at high temperatures, thereby obtaining carbon-coated silicon particles with complete structure and excellent performance.

[0077] For example, unlike the sintering temperature of around 1000℃ commonly used in the industry for high-temperature carbonization furnaces, this technical solution uses a smaller, lower-temperature chamber furnace in an inert gas environment to sinter the coated semi-finished product. Specifically, the inert gas includes at least one of nitrogen, argon, and helium, with nitrogen being the most preferred, and the atmosphere flow rate can be 2.5 m³ / h. 3 / h~5.0m 3 / h; This low-temperature chamber furnace typically features a sealed furnace chamber and a uniform temperature control system, enabling stable heating within a relatively low temperature range (usually below 500℃). Compared to large high-temperature carbonization furnaces, small low-temperature chamber furnaces are smaller in size, have more controllable heating rates, and consume less energy. They can also complete the sintering or solidification of materials under relatively mild conditions, allowing the carbon source to fully solidify and form an amorphous carbon layer. Simultaneously, they avoid high temperatures causing lattice phase transitions, grain growth, or structural damage to nano-silicon particles, thus ensuring the structural integrity and electrochemical performance of the carbon-coated silicon particles.

[0078] S302: The sintered carbon-coated silicon particles are sieved to obtain undersize and oversize materials.

[0079] In this step, sieving refers to classifying the carbon-coated silicon particles by passing them through a sieve. The sieve openings of different sizes separate the carbon-coated silicon particles into undersize and oversize particles. The undersize particles typically consist of smaller, more uniformly distributed carbon-coated silicon particles, while the oversize particles may contain larger, slightly aggregated particles resulting from the curing process.

[0080] For example, the sintered carbon-coated silicon particles can be sieved using a sieve, with a mesh size of 200 mesh or similar. This sieving process can remove large agglomerates or impurities that may form during sintering, resulting in carbon-coated silicon particles with a narrower particle size distribution and more uniform morphology. This is beneficial for improving the consistency and electrochemical performance of subsequent electrode fabrication.

[0081] S303: The sieved material is identified as silicon anode material.

[0082] Understandably, the undersize material is identified as the target product, namely silicon anode material, because its particle size is smaller and its distribution is more uniform. It usually represents carbon-coated silicon particles with complete coating, stable structure, and good dispersion, which can better meet the requirements of material flowability, compaction density and electrochemical performance in the electrode preparation process.

[0083] S304: Silicon anode material is obtained by depolymerizing the material on the sieve using a depolymerization device.

[0084] Compared to the undersize, the oversize often contains larger particle agglomerates with strong internal binding forces. If used directly in electrode fabrication, these agglomerates may lead to uneven stress distribution within the electrode, longer lithium-ion diffusion paths, and difficulty in mitigating volume expansion, thereby reducing the battery's cycle stability and rate performance. Therefore, deagglomeration of the oversize is necessary. Mechanical grinding, air jet milling, ball milling, or other appropriate dispersion methods can effectively break down the agglomerate structure, restoring the particles to a more ideal size and morphology while maintaining the integrity of the carbon coating.

[0085] In one possible implementation, during the depolymerization process, the depolymerization equipment includes at least one of a medium-sized pulverizer, an air jet mill, a vertical pulverizer, and a pin mill.

[0086] Among them, medium-sized crushers typically break larger agglomerates into smaller particles through impact and shearing forces, making them suitable for dispersing materials of medium hardness; air jet mills utilize high-speed airflow to drive particles to collide and rub against each other, thereby achieving ultrafine grinding and effective deagglomeration, making them suitable for materials with high morphology requirements; vertical crushers (VC mills) achieve dispersion through high-speed stirring and shearing between particles; and pin mills effectively break up agglomerates and obtain a uniform particle size distribution through the strong impact and shearing forces between the pins and the material on the screen.

[0087] Because the size of nano-silicon particles is small and the size of the oversize material is also limited, deagglomeration treatment is only needed for the slight agglomeration after sintering (oversize material). This will not damage the coating layer, so there are many deagglomeration methods to choose from, and the requirements are broad. After deagglomeration treatment, the oversize material can be transformed into silicon anode material with performance close to that of the undersize material, thereby improving the overall raw material utilization rate and reducing production costs.

[0088] The method for preparing silicon anode materials provided in this application involves sintering the coated semi-finished product at temperatures far below industry norms (using a low-temperature chamber furnace below 500°C instead of a high-temperature furnace of approximately 1000°C), solidifying the coated carbon source into an amorphous carbon layer. Subsequently, the sintered product (the sintered carbon-coated silicon particles) is sieved. The undersize material with uniform particle size and good coating is directly used as the silicon anode material, while agglomerates in the oversize material are de-agglomerated using specialized mechanical de-agglomeration equipment to obtain the final silicon anode material, thus achieving full utilization of the material. This method ensures that the silicon anode material possesses excellent and uniform particle size distribution, good dispersibility, and a complete carbon coating layer, collectively improving the processing performance of the silicon anode material in electrode preparation and its overall electrochemical performance in all-solid-state batteries, particularly its cycle stability and structural durability.

[0089] This application also provides a negative electrode sheet, comprising: the silicon negative electrode material mentioned in the above embodiments, or a silicon negative electrode material prepared by the method mentioned in the above method embodiments, wherein the specific structure, composition, preparation method or technical effect are as described above. Figures 1 to 3 Examples are not described in detail here.

[0090] This application also provides an all-solid-state battery, including the negative electrode mentioned in the previous embodiment. This all-solid-state battery can be used in vehicles, aircraft, drones, and also in power-consuming devices such as computers, mobile phones, digital cameras, and wearable devices, providing these devices with a stable and long-lasting power source and electrical support.

[0091] The following specific embodiments will provide a detailed description of the halide solid electrolyte and its preparation method provided in this application. Unless otherwise specified, the reagents, materials, and instruments used in the following embodiments are all conventional reagents, materials, and instruments in the art, and can all be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0092] Example 1

[0093] This embodiment provides a silicon anode material, the preparation method of which includes the following steps:

[0094] 1) A fusion shaping machine was selected as the coating equipment. Nitrogen gas was introduced into the chamber of the fusion shaping machine, and nano-silicon particles, accounting for 1 / 3 of the effective volume of the fusion shaping machine, were filled in. Then, phenolic resin with a mass of 1.0% of the mass of the nano-silicon particles was added, so that the nano-silicon particles and the carbon source (phenolic resin) were mixed in the coating equipment (fusion shaping machine) in the form of extrusion (mixing time was 5 minutes, and the rotation speed of the fusion shaping machine was 600 rpm) to obtain a coated semi-finished product; wherein, the phenolic resin coated the surface of the nano-silicon particles.

[0095] 2) The coated semi-finished product is placed in a low-temperature chamber furnace filled with argon for sintering treatment (sintering time is 10h, sintering temperature is 500℃) to obtain sintered carbon-coated silicon particles.

[0096] 3) The sintered carbon-coated silicon particles are sieved through a sieve (sieve mesh size of 200 mesh) to obtain the oversize and undersize particles.

[0097] 4) The sieved material was identified as silicon anode material.

[0098] 5) The material on the sieve is deagglomerated by a vertical pulverizer (the pulverizer speed is 20Hz and the pulverization time is 30min) to obtain silicon anode material.

[0099] Example 2

[0100] This embodiment provides a silicon anode material, the preparation method of which includes the following steps:

[0101] 1) A fusion shaping machine was selected as the coating equipment. Nitrogen gas was introduced into the chamber of the fusion shaping machine, and nano-silicon particles, accounting for 2 / 5 of the effective volume of the fusion shaping machine, were filled in. Then, phenolic resin with a mass of 1.0% of the mass of the nano-silicon particles was added, so that the nano-silicon particles and the carbon source (phenolic resin) were mixed in the coating equipment (fusion shaping machine) in the form of extrusion (mixing time was 5 minutes, and the rotation speed of the fusion shaping machine was 600 rpm) to obtain a coated semi-finished product; wherein, the phenolic resin coated the surface of the nano-silicon particles.

[0102] 2) Same as step 2 in Example 1.

[0103] 3) Same as step 3 in Example 1.

[0104] 4) Same as step 4 in Example 1.

[0105] 5) The material on the sieve is deagglomerated by a medium-sized pulverizer (the pulverizer speed is 20Hz and the pulverization time is 30min) to obtain silicon anode material.

[0106] Example 3

[0107] This embodiment provides a silicon anode material, the preparation method of which includes the following steps:

[0108] 1) Select a fusion shaping machine as the coating equipment. Nitrogen gas is introduced into the chamber of the fusion shaping machine. 2 / 5 of the effective volume of the fusion shaping machine is filled with nano-silicon particles. Then, 1.5% of the mass of the nano-silicon particles is added as liquid asphalt. The nano-silicon particles and the carbon source (liquid asphalt) are mixed in the coating equipment (fusion shaping machine) by extrusion (mixing time is 5 minutes, and the rotation speed of the fusion shaping machine is 600 rpm) to obtain a coated semi-finished product. The liquid asphalt is coated on the surface of the nano-silicon particles.

[0109] 2) Same as step 2 in Example 1.

[0110] 3) Same as step 3 in Example 1.

[0111] 4) Same as step 4 in Example 1.

[0112] 5) Same as step 5 in Example 1), finally obtaining the silicon anode material.

[0113] Example 4

[0114] This embodiment provides a silicon anode material, the preparation method of which includes the following steps:

[0115] 1) Select a fusion shaping machine as the coating equipment. Nitrogen gas is introduced into the chamber of the fusion shaping machine. Half of the effective volume of the fusion shaping machine is filled with nano-silicon particles. Then, 2.0% of the mass of the nano-silicon particles is added with liquid asphalt. The nano-silicon particles and the carbon source (liquid asphalt) are mixed in the coating equipment (fusion shaping machine) by extrusion (mixing time is 5 minutes, and the rotation speed of the fusion shaping machine is 600 rpm) to obtain a coated semi-finished product. The liquid asphalt is coated on the surface of the nano-silicon particles.

[0116] 2) Same as step 2 in Example 1.

[0117] 3) Same as step 3 in Example 1.

[0118] 4) Same as step 4 in Example 1.

[0119] 5) Same as step 5 in Example 1), finally obtaining the silicon anode material.

[0120] Example 5

[0121] This embodiment provides a silicon anode material, the preparation method of which includes the following steps:

[0122] 1) Select a fusion shaping machine as the coating equipment. Nitrogen gas is introduced into the chamber of the fusion shaping machine. Half of the effective volume of the fusion shaping machine is filled with nano-silicon particles. Then, 2.5% of the mass of the nano-silicon particles is added with liquid asphalt. The nano-silicon particles and the carbon source (liquid asphalt) are mixed in the coating equipment (fusion shaping machine) by extrusion (mixing time is 5 minutes, and the rotation speed of the fusion shaping machine is 600 rpm) to obtain a coated semi-finished product. The liquid asphalt is coated on the surface of the nano-silicon particles.

[0123] 2) Same as step 2 in Example 1.

[0124] 3) Same as step 3 in Example 1.

[0125] 4) Same as step 4 in Example 1.

[0126] 5) Same as step 5 in Example 1), finally obtaining the silicon anode material.

[0127] Comparative Example 1

[0128] This embodiment provides a silicon anode material, the preparation method of which includes the following steps:

[0129] 1) Select a fusion shaping machine as the coating equipment. Nitrogen gas is introduced into the chamber of the fusion shaping machine. Half of the effective volume of the fusion shaping machine is filled with nano-silicon particles. Then, 3.0% of the mass of the nano-silicon particles is added with liquid asphalt. The nano-silicon particles and the carbon source (liquid asphalt) are mixed in the coating equipment (fusion shaping machine) by extrusion (mixing time is 5 minutes, and the rotation speed of the fusion shaping machine is 600 rpm) to obtain the coated semi-finished product. The liquid asphalt is coated on the surface of the nano-silicon particles.

[0130] 2) Same as step 2 in Example 1.

[0131] 3) Same as step 3 in Example 1.

[0132] 4) Same as step 4 in Example 1.

[0133] 5) Same as step 5 in Example 2), finally obtaining the silicon anode material.

[0134] Comparative Example 2

[0135] This embodiment provides a silicon anode material, the preparation method of which includes:

[0136] Nano-silicon particles of the same volume as those in Comparative Example 1 (without any added resin or pitch carbon source) were selected as silicon anode materials.

[0137] Test Example 1

[0138] Particle size: The silicon anode material is characterized by being fed into a particle patterner to directly obtain the particle size D of the silicon anode material. 50 Numerical value.

[0139] Test Example 2

[0140] Specific surface area: The silicon anode material is placed in a U-shaped sample tube, and a mixed gas containing a certain proportion of adsorbate is passed through the sample. The amount of adsorbate molecules (N2) adsorbed by the sample is determined based on the change in gas concentration before and after adsorption. After the amount of adsorbate gas adsorbed is determined, the specific surface area of ​​the silicon anode material to be tested is calculated based on the amount of adsorbate molecules adsorbed.

[0141] Test Example 3

[0142] Specific capacity and first-cycle efficiency: Silicon anode material is prepared as an attachment to a copper current collector to form a complete anode sheet that can be directly used for battery cell packaging; then it is sequentially stacked with a separator and a lithium metal sheet and assembled into a coin cell; using a small current of 0.05C for charging and discharging (current cutoff), the specific capacity and first-cycle efficiency can be obtained.

[0143] Understandably, first-cycle efficiency (CEE) refers to the percentage of discharge capacity to charge capacity in the first cycle of an all-solid-state battery. The calculation formula is: CEE = First charge capacity / First discharge capacity × 100%. It is used to reflect the degree of energy loss during the first cycle of the battery. The higher the CEE, the smaller the irreversible capacity loss caused by interfacial side reactions, electrolyte decomposition, etc. during the initial charge and discharge process, and the higher the energy conversion efficiency.

[0144] Test Example 4

[0145] Capacity retention rate: Silicon anode material is prepared as an attachment to a copper current collector to form a complete anode sheet that can be directly used for battery cell packaging; it is then stacked with a ternary cathode sheet and a sulfide electrolyte membrane in sequence, subjected to isostatic pressing, and encapsulated in an aluminum-plastic film to form a small soft-pack solid-state battery; the capacity retention rate is tested using a 0.1C low-current charge-discharge test.

[0146] Understandably, the 200-cycle capacity retention rate refers to the percentage of the discharge capacity on the 200th charge-discharge cycle to the initial discharge capacity after 200 charge-discharge cycles for an all-solid-state battery. The calculation formula is: 200-cycle capacity retention rate = initial discharge capacity / 200th discharge capacity × 100%. It is used to measure the cycle stability of the battery. The higher the capacity retention rate, the better the integrity of the electrode structure, the interfacial compatibility between the electrolyte and the electrode, and the utilization rate of the active materials during multiple cycles, and the more guaranteed the battery's lifespan.

[0147] Test Example 5

[0148] Needle penetration test: Select the small soft-pack solid-state battery obtained in Test Example 4, and refer to GB / T 39086-2024 "Safety Requirements for Solid-State Lithium-ion Batteries". Use a 3mm steel needle as the puncture medium and a uniform puncture speed of 20mm / s. When the temperature rise on the battery surface does not exceed 150℃, determine whether the battery catches fire or explodes.

[0149] Understandably, the nail penetration test simulates the risk of thermal runaway in all-solid-state batteries under extreme mechanical damage. If the nail penetration test is passed, it indicates that the internal materials and interface structure of the battery have higher mechanical and thermal stability. This stability can not only suppress thermal runaway and structural collapse under extreme mechanical damage such as puncture, but also effectively resist the structural stress and interface side reactions caused by repeated lithium insertion and extraction during long-term charge and discharge cycles, reduce the structural collapse of active materials and the increase of interface impedance, thereby maintaining more stable electrochemical performance during cycling.

[0150] Test Example 6

[0151] Hot box test: Select the small soft-pack solid-state battery obtained in Test Example 4, and refer to GB / T 39086-2024 "Safety Requirements for Solid Lithium-ion Batteries". Place the battery in a high temperature environment of 85℃±2℃ for 7 hours, and then observe for 1 hour to determine whether the battery catches fire, explodes or leaks.

[0152] Understandably, the hot-box test verifies the high-temperature stability of all-solid-state batteries at around 85°C, demonstrating that they do not ignite, explode, or leak. Passing the hot-box test indicates that the battery maintains structural and interface stability at around 85°C, preventing fire, explosion, or leakage. This high-temperature stability essentially reflects the battery's internal materials and interfaces' tolerance to thermal stress. During long-term charge-discharge cycles, the battery also generates heat and structural stress due to repeated lithium insertion / extraction and interface reactions. This ability to maintain stability at high temperatures effectively resists heat accumulation and structural degradation during cycling, reducing the decomposition of active materials, increased interface impedance, and exacerbated side reactions, thereby maintaining more stable electrochemical performance during cycling.

[0153] The test results for test examples 1 to 6 are shown in Table 1.

[0154] Table 1. Test results of test examples 1-6

[0155]

[0156] Based on Table 1, the following conclusions can be drawn:

[0157] The specific capacity of Examples 1 to 5 (all referring to the silicon anode materials provided in the examples / comparative examples or all-solid-state batteries containing the corresponding silicon anode materials, which will not be described again below) is higher than that of the comparative example. Among them, the silicon anode material provided in Comparative Example 2 has no carbon source coating on the surface of the nano-silicon particles. Therefore, the silicon interface is directly treated at high temperature during sintering, resulting in partial oxidation phase transition and the formation of SiO2. It cannot exhibit electrochemical specific capacity, so the overall specific capacity of the particles decreases. Particle size and specific surface area both indicate the morphology of silicon anode materials. Among them, the silicon anode material provided in Comparative Example 1 contains 3.0% of the mass of liquid asphalt of nano-silicon particles. Due to severe agglomeration, its particle size could not be measured.

[0158] Because carbon sources form a carbon layer on the surface of silicon nanoparticles, this carbon layer contains numerous active sites and microporous structures. During the initial lithium intercalation process, more lithium ions are consumed when forming the solid electrolyte interface film. In contrast, uncoated silicon nanoparticles have fewer active sites, resulting in less lithium consumption during the initial solid electrolyte interface film formation. Simultaneously, the carbon source coating process may generate a small number of defect sites on or inside the silicon nanoparticles. These sites can irreversibly complex and adsorb lithium ions, further consuming active lithium. Furthermore, some carbon materials themselves exhibit a small amount of irreversible lithium intercalation during the initial charge and discharge cycle. This leads to a significantly higher overall irreversible capacity for silicon anode materials containing carbon sources compared to those without. Since the initial battery efficiency is the ratio of the initial discharge capacity to the initial charge capacity, an increase in irreversible capacity directly reduces the proportion of the initial discharge capacity. Therefore, theoretically, silicon anode materials containing carbon sources will have a lower initial efficiency than those without.

[0159] However, the results of the first-efficiency test show that although the first-efficiency of Examples 1 to 5 is slightly lower than that of Comparative Example 2, it is basically at the same level, which further demonstrates that the silicon anode material provided in this application has a good optimization effect in terms of electrochemical performance protection and has excellent interface stability.

[0160] The 200-cycle capacity retention rate, needle penetration test results, and hot box test results of Examples 1 to 5 all showed better performance than those of Comparative Examples 1 and 2. Not only was the 200-cycle capacity retention rate significantly higher than that of the comparative examples, but the needle penetration test was also passed smoothly, and the hot box test was also basically passed. In contrast, the silicon anode material provided by Comparative Example 1 could not be made into a cell sample due to its particle size exceeding the nanometer scale, and therefore could not complete the corresponding 200-cycle capacity retention rate test, needle penetration test, and heat test. The 200-cycle capacity retention rate of Comparative Example 2 was lower than that of Examples 1 to 5, and the needle penetration test and hot box test results did not meet the standards. It should be noted that the hot box test of Example 1 failed because the pass rate of the hot box test in the safety test has a probabilistic problem. When the amount of carbon source coating is at a low level, there is a certain probability that it will not pass (because the carbon coating layer is not dense enough to protect the highly active silicon interface), but this test result does not mean that the carbon coating layer is ineffective.

[0161] In summary, the silicon anode materials provided in Examples 1 to 5 demonstrate significant advantages in improving battery cycle stability and safety. Therefore, the silicon anode materials provided in this application can effectively improve the cycle performance of all-solid-state batteries.

[0162] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A silicon anode material, characterized in that, The material includes coated silicon-based materials, wherein the silicon-based materials include nano-silicon particles, and the surface of the nano-silicon particles is coated with a carbon source. The mass of the carbon source is 1.0% to 2.5% of the mass of the nano-silicon particles.

2. The silicon anode material according to claim 1, characterized in that, The carbon source is coated onto the surface of the nano-silicon particles using a coating device; And / or, The filling volume of the nano-silicon particles is 1 / 3 to 1 / 2 of the effective volume of the coating device.

3. The silicon anode material according to claim 1 or 2, characterized in that, The carbon source is a resin-based carbon source or an asphalt-based carbon source.

4. A method for preparing a silicon anode material, characterized in that, The method includes: A coated silicon-based material and a carbon source are mixed in an inert gas environment to obtain a coated semi-finished product; wherein the silicon-based material comprises silicon nanoparticles, and the carbon source is coated on the surface of the silicon nanoparticles, with the mass of the carbon source being 1.0% to 2.5% of the mass of the silicon nanoparticles; The silicon anode material is obtained from the coated semi-finished product.

5. The method according to claim 4, characterized in that, The process of mixing the coated silicon-based material and the carbon source in an inert gas environment to obtain a coated semi-finished product includes: The nano-silicon particles and carbon source are placed in a coating device and mixed in an inert gas environment to obtain the coated semi-finished product. The filling volume of the nano-silicon particles is 1 / 3 to 1 / 2 of the effective volume of the coating device.

6. The method according to claim 4 or 5, characterized in that, The carbon source is a resin-based carbon source or an asphalt-based carbon source.

7. The method according to claim 4 or 5, characterized in that, The process of obtaining the silicon anode material based on the coated semi-finished product includes: The coated semi-finished product is sintered in an inert gas environment using a sintering equipment to obtain sintered carbon-coated silicon particles. The sintered carbon-coated silicon particles are sieved to obtain undersize and oversize particles. The sieved material was identified as the silicon anode material; The silicon anode material is obtained by depolymerizing the material on the sieve using a depolymerization device.

8. The method according to claim 7, characterized in that, During the depolymerization process, the depolymerization equipment includes at least one of a medium-sized material crusher, an air jet mill, a vertical mill, and a rod mill.

9. The method according to claim 4 or 5, characterized in that, During the mixing process, the coating equipment includes a fusion shaping machine, and / or the mixing time is 3 min to 5 min, and / or the rotation speed of the coating equipment is 550 rpm to 650 rpm.

10. The method according to claim 7, characterized in that, When performing sintering, the sintering equipment is a low-temperature chamber furnace, and / or the sintering temperature is 450℃~500℃, and / or the sintering time is 10h~12h.

11. A negative electrode sheet, characterized in that, include: The silicon anode material as described in any one of claims 1 to 3, or the silicon anode material prepared by the method described in any one of claims 4 to 10.

12. An all-solid-state battery, characterized in that, Includes the negative electrode as described in claim 11.

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