Silicon-based negative electrode material, silicon electrode and lithium ion battery

Abstract

The application discloses a silicon-based negative electrode material, which comprises, from inside to outside, a core carbon layer, a gradient silicon-carbon composite layer, an intermediate silicon layer, a dispersed silicon layer and a boundary carbon layer; the core carbon layer is a dense carbon layer; the gradient silicon-carbon composite layer comprises a gradient porous carbon layer with gradually increasing porosity from inside to outside; silicon is deposited in the pores of the gradient porous carbon layer, and the content of the silicon gradually increases from inside to outside; the intermediate silicon layer and the dispersed silicon layer are sequentially coated on the outside of the gradient silicon-carbon composite layer; the boundary carbon layer is coated on the outside of the dispersed silicon layer; and part of the silicon particles in the dispersed silicon layer are embedded in the boundary carbon layer. The application further discloses a preparation method of the silicon-based negative electrode material and a lithium ion battery prepared from the silicon-based negative electrode material. The silicon-based negative electrode material can reduce the volume expansion of the electrode during the charging and discharging process, and improve the cycle life of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a silicon-based anode material, a silicon electrode, and a lithium-ion battery. Background Technology

[0002] With the rapid development of the new energy vehicle industry, electric vehicles require battery systems with higher specific energy density, higher charge and discharge rate capabilities, and higher safety. Silicon anodes, due to their high theoretical specific capacity (4200mAh / g), low lithium intercalation site (0.4V), abundant resources, and environmental friendliness, are considered the most promising candidate to replace graphite anode materials and become the next generation of high-performance lithium-ion battery anode materials.

[0003] During the lithium-ion insertion and extraction process, silicon anode materials undergo enormous volume expansion (~300%), leading to the fragmentation and pulverization of active particles, the continuous growth of an unstable surface solid electrolyte interphase (SEI) film, and severe electrode structure collapse. This results in rapid corrosion of the silicon anode, low electrochemical performance, and low cycle life. Furthermore, poor conductivity, low lithium diffusion rate, and high internal resistance are also key challenges faced by silicon anode electrodes.

[0004] Therefore, how to reduce the volume expansion effect of silicon-based materials during charging and discharging and improve the conductivity of silicon-based material systems remains an urgent technical problem to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a silicon-based anode material that can reduce the volume expansion of the electrode during charging and discharging, reduce side reactions with the electrolyte, and improve the cycle performance of the battery.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: The first aspect of the present invention provides a silicon-based anode material, which comprises, from the inside out, a core carbon layer, a gradient silicon-carbon composite layer, an intermediate silicon layer, a dispersed silicon layer and a boundary carbon layer. The gradient silicon-carbon composite layer includes a gradient porous carbon layer with gradually increasing porosity from the inside to the outside. Silicon is deposited in the pores of the gradient porous carbon layer, and the silicon content gradually increases from the inside to the outside to form a gradient distributed silicon layer. The intermediate silicon layer and the dispersed silicon layer are sequentially coated on the outside of the gradient silicon-carbon composite layer, and the boundary carbon layer is coated on the outside of the dispersed silicon layer, with some silicon particles in the dispersed silicon layer embedded in the boundary carbon layer.

[0007] Furthermore, the diameter of the carbon layer in the core region is 0.2~12μm; And / or, the thickness of the gradient porous carbon layer is 500~5000 nm; And / or, the thickness of the gradient-distributed silicon layer is 100~800nm; And / or, the thickness of the intermediate silicon layer is 20~500nm; And / or, the thickness of the boundary carbon layer is 15~80nm, and the thickness of the dispersed silicon layer is less than the thickness of the boundary carbon layer.

[0008] Furthermore, the carbon in the core carbon layer, the gradient porous carbon layer, and the boundary carbon layer includes at least one of graphitized carbon and amorphous carbon. And / or, the silicon in the gradient silicon-carbon composite layer, the intermediate silicon layer, and the dispersed silicon layer includes silicon oxide (SiO2). x At least one of ), ), and Si, where 0 < x < 2.

[0009] Furthermore, the core carbon layer is a non-porous carbon layer, the gradient-distributed silicon layer and the intermediate silicon layer are porous silicon layers, and the diffuse silicon layer is a non-porous silicon layer.

[0010] Furthermore, the carbon content in the silicon-based anode material is 22% to 90%. And / or, in the silicon-based anode material, the silicon content is 1-75%; And / or, the particle size D50 of the silicon-based anode material is 4.4~27μm; And / or, the tap density of the silicon-based anode material is 0.65~1.45 g / cm³. 3 ; And / or, the specific surface area of ​​the silicon-based anode material is 0.95~6.5m². 2 / g.

[0011] A second aspect of the present invention provides a method for preparing a silicon-based anode material, comprising: S1. Carbon particles are subjected to carbon dioxide vapor phase erosion under a protective atmosphere to form a porous structure on the surface of the carbon particles. S2. A silicon layer is deposited on the surface of the carbon particles using vapor deposition. S3. A carbon layer is deposited on the surface of the silicon layer using vapor deposition. S4. Heat preservation is performed to carbonize the carbon layer, thereby obtaining the silicon-based anode material.

[0012] Further, in step S1, the protective atmosphere includes at least one of nitrogen, helium, neon, argon, krypton, and xenon; And / or, the carbon particles are graphitized carbon particles; the diameter of the carbon particles is 0.1~15 μm; And / or, the temperature of the vapor phase erosion is 450~800℃; And / or, the vapor phase erosion time is 3~12 h.

[0013] Furthermore, in step S2, the gas used for vapor deposition is silane; And / or, the temperature of the vapor deposition is 700~1000℃; And / or, the vapor deposition time is 0.3~2 h; And / or, the thickness of the silicon layer is ≤1.8 μm.

[0014] Further, in step S3, the gas used for vapor deposition is a mixture of hydrogen and gas S, wherein gas S includes at least one of formaldehyde, acetaldehyde, methane, ethane, propane, acetylene, and propyne. And / or, the temperature of the vapor deposition is 400~700℃.

[0015] Furthermore, in step S3, the volume ratio of hydrogen to gas S in the mixed gas is 1:1~6.

[0016] Furthermore, in step S4, the heat preservation time is 3 to 8 hours.

[0017] A third aspect of the present invention provides a silicon electrode, comprising a negative electrode current collector and a negative electrode material layer formed on at least one side surface of the negative electrode current collector, wherein the active material in the negative electrode material layer comprises a graphite negative electrode material and the aforementioned silicon-based negative electrode material.

[0018] Furthermore, in the active material, the mass percentage of silicon-based anode material is 0.5% to 60%; And / or, in the negative electrode material layer, the mass ratio of active material, conductive agent and binder is 80~99 : 0.5~8 : 0.6~10.

[0019] A fourth aspect of the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode and the negative electrode, and the negative electrode is the aforementioned silicon electrode.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The silicon-based anode material of the present invention has a gradient silicon-carbon composite layer disposed inside, which is formed by the interlocking of a gradient porous carbon layer and a gradient distributed silicon layer. The gradient porous carbon layer includes a network structure carbon formed by pores, while the gradient distributed silicon layer contains multiple nanopores. The presence of such network structure carbon and nanopores provides a buffer space for the expansion of silicon material, reducing the volume expansion of silicon electrode during charging and discharging.

[0021] 2. The silicon-based anode material of the present invention has a boundary carbon layer covering a dispersed silicon layer, thereby providing a protective layer for the internal silicon layer. This not only effectively prevents the pulverization and shedding of silicon particles, but also prevents excessive aggregation of silicon crystal clusters, suppresses volume changes, reduces side reactions with the electrolyte, and improves the cycle performance of the battery. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of a silicon-based anode material in one embodiment of the present invention; The layers are: 1. Core carbon layer; 2. Gradient silicon-carbon composite layer; 21. Gradient porous carbon layer; 22. Gradient distributed silicon layer; 3. Intermediate silicon layer; 4. Dispersed silicon layer; 5. Boundary carbon layer. Detailed Implementation

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] Currently, the energy density of lithium-ion batteries is difficult to further improve due to the theoretical capacity of graphite materials (372 mAh / g). In contrast, silicon materials possess a higher energy density (up to 4200 mAh / g), making them the most likely candidate for the next generation of high-energy-density lithium-ion battery anode materials. However, during the lithium-ion insertion and extraction process, silicon anode materials experience significant volume expansion (~300%), leading to the fragmentation and pulverization of active particles, the continuous growth of an unstable surface solid electrolyte interphase (SEI) film, and severe electrode structure collapse. This results in rapid corrosion of the silicon anode, low electrochemical performance, and low cycle life. Furthermore, poor conductivity, low lithium diffusion rate, and high internal resistance are also key challenges facing silicon anode electrodes.

[0025] The composite of carbon and silicon is considered one of the most effective strategies for improving the electrochemical performance of silicon anode materials. Carbon materials can act as a volume buffer, thereby reducing stress concentration caused by lithium insertion. Furthermore, carbon materials possess excellent conductivity, high strength, and high flexibility, and can form a complete conductive network within the silicon anode material. However, how to synthesize carbon and silicon to obtain highly stable carbon-silicon-based anode materials remains a pressing problem to be solved.

[0026] To address this technical problem, the present invention provides a silicon-based anode material. Through a reasonable structural design, the local carbon material inside the silicon-based anode material exhibits a certain concentration gradient. The resulting silicon-based anode material not only has high strength but can also effectively buffer the volume expansion of silicon during charging and discharging.

[0027] For details, please see Figure 1 In one embodiment of the present invention, the silicon-based anode material is in the form of spherical particles, and its cross-section, from the inside out, includes a core carbon layer 1, a gradient silicon-carbon composite layer 2, an intermediate silicon layer 3, a dispersed silicon layer 4, and a boundary carbon layer 5.

[0028] In this invention, the core carbon layer is composed of pure carbon and is a dense carbon layer. The carbon material includes at least one of graphitized carbon and amorphous carbon. The diameter of the core carbon layer is preferably between 0.2 and 12 μm, for example, it can be 0.2–0.5 μm, 0.5–1 μm, 1–2 μm, 2–3 μm, 3–4 μm, 4–5 μm, 5–6 μm, 6–7 μm, 7–8 μm, 8–9 μm, 9–10 μm, 10–11 μm, 11–12 μm, or any range between these values.

[0029] The outer layer of the core carbon layer is a gradient silicon-carbon composite layer. (See also...) Figure 1 The gradient silicon-carbon composite layer is actually composed of interlocking gradient porous carbon layers and gradient-distributed silicon layers. The inner layer of the gradient porous carbon layer encapsulates the core carbon layer, with porosity gradually increasing and carbon content gradually decreasing from the inside out. The outer surface of the gradient porous carbon layer is densely covered with protrusions and pits. This special morphology with a gradient distribution structure can be obtained using vapor phase etching, which involves vapor phase etching the surface of carbon particles to form pits / pores. Because the degree of vapor phase etching is more severe on the surface and gradually decreases towards the interior, it exhibits a morphology with more pits / pores on the surface and gradually decreasing porosity and increasing carbon content towards the interior.

[0030] Gradient-distributed silicon layers are obtained by vapor deposition of silicon into the pores of a gradient porous carbon layer. Due to the gradient porosity of the gradient porous carbon layer, the silicon layer deposited within the pores also exhibits a gradient, meaning the silicon content gradually increases from the inside out. Initially, the silicon content is very low, but as the porosity increases, the silicon content gradually increases, eventually forming layers. Because the surface of the gradient porous carbon layer has pitted morphology, these pits are filled with silicon after deposition, resulting in a seamless integration between the gradient-distributed silicon layer and the gradient porous carbon layer.

[0031] The carbon in the aforementioned gradient porous carbon layer may include at least one carbon material such as graphitized carbon or amorphous carbon; the silicon in the aforementioned gradient distributed silicon layer may include silicon oxide (SiO2).x Silicon in at least one form, such as Si, where 0 < x < 2.

[0032] In this invention, the thickness of the gradient porous carbon layer is preferably 500~5000nm, for example, it can be 500~1000nm, 1000~1500nm, 1500~2000nm, 2000~2500nm, 2500~3000nm, 3000~3500nm, 3500~4000nm, 4000~4500nm, 4500~5000nm, or any range between these values.

[0033] In this invention, the thickness of the gradient-distributed silicon layer is preferably between 100 and 800 nm, for example, it can be 100-200 nm, 200-300 nm, 300-400 nm, 400-500 nm, 500-600 nm, 600-700 nm, 700-800 nm, or any range between these values.

[0034] The intermediate silicon layer is covered by a gradient-distributed silicon layer, which is a porous silicon layer. Unlike the gradient-distributed silicon layer, the silicon distribution in the intermediate silicon layer does not change gradient. The intermediate silicon layer is obtained by depositing silicon on top of the gradient-distributed silicon layer through vapor deposition, therefore there is no obvious interface between it and the gradient-distributed silicon layer.

[0035] In this invention, the thickness of the intermediate silicon layer is preferably 20~500nm, for example, it can be 20~50nm, 50~100nm, 100~200nm, 200~300nm, 300~400nm, 400~500nm, or any range between these values.

[0036] The dispersed silicon layer is located outside the intermediate silicon layer. It is formed by the diffusion of silicon from the intermediate silicon layer outward during the high-temperature heat treatment process that forms the boundary carbon layer. Unlike the intermediate silicon layer, the dispersed silicon layer is a dense silicon layer with virtually no voids. Because the dispersed silicon layer is formed by the dispersion of silicon, its outer boundary has an irregular shape, and its thickness is generally between a few nanometers and tens of nanometers.

[0037] The boundary carbon layer coats the outside of the dispersed silicon layer, and the bonding between the boundary carbon layer and the dispersed silicon layer is relatively tight, with some silicon particles from the dispersed silicon layer dispersing into the boundary carbon layer. The thickness of the boundary carbon layer is preferably 15-80 nm, for example, 15-20 nm, 20-22 nm, 22-24 nm, 24-30 nm, 30-35 nm, 35-50 nm, 50-60 nm, 60-70 nm, 70-80 nm, or any range between these values. More preferably, the thickness of the dispersed silicon layer is less than the thickness of the boundary carbon layer.

[0038] In this invention, the carbon content in the silicon-based anode material is between 22% and 90%, preferably between 40% and 85%, for example, it can be 40%, 45%, 48%, 50%, 54%, 55%, 56%, 58%, 60%, 63%, 65%, 68%, 70%, 73%, 75%, 78%, 80%, 82%, or 85%.

[0039] In this invention, the silicon content in the silicon-based anode material is between 1% and 75%, preferably between 21% and 45%, for example, it can be 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45%.

[0040] In this invention, the median particle size D50 of the silicon-based anode material is 4.4~27μm, more preferably 5.6~14μm, and more preferably 6.0~18μm. For example, it can be 6.0μm, 6.5μm, 7.0μm, 7.5μm, 8.0μm, 8.5μm, 9.0μm, 9.5μm, 10.0μm, 10.5μm, 11.0μm, 11.5μm, 12μm, 12.5μm, 13.0μm, 13.5μm, 14.0μm, 14.5μm, 15.0μm, 15.5μm, 16.0μm, 16.5μm, 17.0μm, 17.5μm, or 18.0μm.

[0041] In this invention, the tap density of the silicon-based anode material is between 0.65 and 1.45 g / cm³. 3 The preferred concentration is 0.75~1.15 g / cm³. 3 More preferably, it is 0.78~1.05 g / cm³. 3 For example, it can be 0.78 g / cm³. 3 0.79g / cm 3 0.80g / cm 3 0.85g / cm 3 0.82g / cm 3 0.85g / cm 3 0.88g / cm 3 0.90g / cm 3 0.91g / cm 3 0.93g / cm 3 0.95g / cm 3 0.97g / cm 3 0.98g / cm 3 0.99g / cm 3 1.00g / cm3 1.02g / cm 3 1.03 g / cm 3 1.04 g / cm 3 1.05g / cm 3 1.06 g / cm 3 g / cm 3 10.7g / cm 3 .

[0042] In this invention, the specific surface area (SSA) of the silicon-based anode material is between 0.95 and 6.5 m². 2 / g, with a preferred value of 1.1~55m. 2 / g, more preferably 1.5~5 m 2 / g, for example, can be 1.5 m 2 / g, 1.55m 2 / g, 1.56m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2.0m 2 / g, 2.5m 2 / g, 3.0m 2 / g, 3.5m 2 / g, 4.0m 2 / g, 4.5m 2 / g, 5.0m 2 / g.

[0043] In this invention, a gradient porous carbon layer and a gradient distributed silicon layer are intercalated. On the one hand, the carbon layer embedded in the gradient distributed silicon layer improves the electronic conductivity of the silicon layer; on the other hand, the expansion stress on the gradient porous carbon layer gradually increases during lithium intercalation, providing a layer-by-layer buffer space for silicon volume expansion. Therefore, the two layers work synergistically. The boundary carbon layer encapsulates the dispersed silicon layer, and the dispersed silicon layer contains an intermediate silicon layer. The dispersed silicon layer and the intermediate silicon layer can be completely sealed within a graphitized carbon or amorphous carbon shell. Furthermore, some silicon particles in the dispersed silicon layer are embedded in the boundary carbon layer, providing a protective layer for the volume expansion of the intermediate silicon layer and the dispersed silicon layer, effectively preventing the pulverization and peeling of silicon particles.

[0044] It should be noted that the silicon-based anode material of the present invention, after being processed by crushing, sieving, and grinding during the preparation process, can be in the form of ellipsoids, blocks, strips, sheets, or uneven surfaces, in addition to being spherical.

[0045] This invention also provides a method for preparing the above-mentioned silicon-based anode material, specifically including the following steps: S1. Carbon particles are subjected to carbon dioxide vapor phase erosion under a protective atmosphere to form a porous structure on the surface of the carbon particles. S2. A silicon layer is deposited on the surface of the carbon particles using vapor deposition. S3. A carbon layer is deposited on the surface of the silicon layer using vapor deposition. S4. Heat preservation is performed to carbonize the carbon layer, thereby obtaining the silicon-based anode material.

[0046] The entire preparation of the aforementioned silicon-based anode material is carried out in a vapor deposition tube furnace. Before carbon dioxide vapor etching, a protective gas is introduced into the tube furnace to purge any air. The protective gas includes, but is not limited to, at least one of nitrogen, helium, neon, argon, krypton, and xenon.

[0047] In step S1 of this invention, the carbon particles used are preferably graphitized carbon particles with a diameter of 0.1~15μm. During carbon dioxide vapor phase etching, carbon dioxide is introduced into the tube furnace at a concentration of 5%~50% (v / v), for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. Here, the concentration refers to the percentage of the volume of introduced CO2 to the total gas volume (protective atmosphere + CO2).

[0048] At high temperatures, the introduced CO2 reacts with the carbon material to produce CO gas, which then corrodes the carbon material. The temperature for vapor phase corrosion is 450–800℃, for example, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, etc. The time for vapor phase corrosion is 3–12 hours, for example, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc. After vapor phase corrosion, the carbon particles develop a morphology with a gradient porosity and an uneven surface.

[0049] In step S2 of this invention, after the vapor phase etching is completed, the furnace temperature of the tube furnace is raised to 700-1000°C, and a deposition gas, such as silane, is introduced into the tube furnace. At high temperature, the silane decomposes to produce silicon particles, which are first deposited in the pores within the carbon particles. As deposition proceeds, the silicon particles gradually deposit into layers and fill the pits on the surface of the carbon particles, forming a gradient-distributed silicon layer embedded in the carbon particles. Then, vapor phase deposition continues, and an intermediate silicon layer is deposited on the gradient-distributed silicon layer. In this step, the vapor phase deposition temperature can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, etc., and the total thickness of the deposited silicon layer is preferably ≤1.8 μm.

[0050] In step S3 of this invention, the tubular furnace is cooled to 400-700°C, and then a mixture of hydrogen and gas S is introduced for vapor phase deposition, thereby depositing a carbon layer on the surface of the intermediate silicon layer. The deposition temperature can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, etc. Gas S can be at least one of formaldehyde, acetaldehyde, methane, ethane, propane, acetylene, propyne, etc.

[0051] Adding a certain amount of hydrogen to the mixed gas is beneficial to increasing the carbon deposition rate. The volume ratio of hydrogen to gas S is preferably 1:1 to 6 (v / v), for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, etc. Preferably, the thickness of the deposited carbon layer is controlled to be 15 to 80 nm.

[0052] In step S4 of this invention, the temperature in the deposition furnace is maintained at 400~700℃ for 3~8 hours to further carbonize the deposited carbon layer, forming a boundary carbon layer. During the heat treatment, silicon from the intermediate silicon layer diffuses into the boundary carbon layer and partially embeds into it, forming a dispersed silicon layer. The bond between the dispersed silicon layer and the boundary carbon layer is tighter, preventing excessive aggregation of silicon clusters and suppressing volume changes. Furthermore, after the heat treatment, the deposited silicon partially transforms into amorphous silicon, which is beneficial for improving the electrochemical performance of the material.

[0053] The present invention further provides a silicon electrode, comprising a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode material layer comprises a negative electrode active material, a conductive agent, and a binder; wherein the negative electrode active material comprises a graphite negative electrode material and the aforementioned silicon-based negative electrode material. The silicon electrode can be prepared using conventional methods in the art, one illustrative preparation method being: preparing a modified silicon-based negative electrode material, binder, and conductive agent into an electrode slurry in a certain proportion, then coating it onto at least one surface of the negative electrode current collector, and after drying and pressing, obtaining the aforementioned silicon electrode.

[0054] In a preferred embodiment, the silicon electrode is prepared as follows: the negative electrode active material and conductive agent are stirred for 10-60 minutes for the first mixing; then a binder and water are added and stirred, controlling the solid content to 70-80%, and stirred again for 30-180 minutes for the second mixing; then a conductive agent, binder, and water are added, controlling the solid content to 40-55%, and a vacuum is drawn to a vacuum degree of ≤-100KPa, stirred for 60-300 minutes for the third mixing to obtain a silicon negative electrode slurry. The silicon negative electrode slurry is coated on a negative electrode current collector, dried, and pressed into a sheet to obtain the silicon electrode.

[0055] In some embodiments, the negative electrode active material, conductive agent, and binder can be mixed in mass ratios of 80–99%, 0.5–8%, and 0.6–10.0%, respectively. For example, the proportion of the negative electrode active material can vary from 80–81%, 81–82%, 82–83%, 83–84%, 84–85%, 85–86%, 86–87%, 87–88%, 88–89%, 89–90%, 90–91%, 91–92%, 92–93%, 93–94%, 94–95%, 95–96%, 96–97%, 97–98%, to 98–99%.

[0056] In this invention, the mass percentage of silicon-based anode material in the anode active material is 0.5% to 60%, for example, it can be 0.5% to 1%, 1% to 5%, 5% to 10%, 10% to 20%, 20% to 30%, 30% to 40%, 40% to 50%, 50% to 60%, or any range between these values.

[0057] In this invention, the negative electrode active material includes the aforementioned silicon-based negative electrode material and graphite negative electrode material. The graphite negative electrode material can be any graphite material commonly used in the art, including but not limited to at least one of natural graphite and artificial graphite. Graphite material is the most widely used negative electrode active material, possessing excellent conductivity, which not only enhances the conductivity of silicon materials but also contributes to capacity. Preferably, the graphite negative electrode material is one or more of the following: artificial graphite or natural graphite that has undergone surface treatments such as spheroidization or structural modification, oxidation, or etching; or doped with nitrogen, phosphorus, sulfur, iron, cobalt, nickel, aluminum, zinc, etc.; or modified by amorphous carbon layer coating.

[0058] In this invention, the negative electrode current collector may be one or more of the following: copper foil, porous copper foil, foamed nickel / copper foil, zinc-plated copper foil, nickel-plated copper foil, carbon-coated copper foil, nickel foil, titanium foil, and carbon-containing porous copper foil. Preferably, it is copper foil, zinc-plated copper foil, nickel-plated copper foil, or carbon-coated copper foil.

[0059] In this invention, the adhesive may be a monomer, polymer, or copolymer of acrylonitrile, vinylidene fluoride, vinyl alcohol, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, methacrylamide, acrylic acid, lithium acrylate, acrylamide, imide, acrylate, styrene-butadiene rubber, sodium alginate, chitosan, ethylene glycol, or guar gum.

[0060] In this invention, the conductive agent may be at least one of conductive carbon black, acetylene black, graphite, graphene, carbon micro / nanowire conductive materials, and carbon micro / nanotube conductive materials.

[0061] Furthermore, the present invention provides a lithium-ion battery, including the aforementioned silicon electrode. An illustrative preparation method is as follows: the aforementioned silicon electrode, separator, and positive electrode sheet are wound to obtain a battery cell; the battery cell is then mounted in a battery casing; and after processes such as drying, electrolyte injection, encapsulation, formation, and capacity testing, a lithium-ion battery is obtained.

[0062] In the aforementioned positive electrode sheet, the positive electrode active material may be at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, lithium iron manganese phosphate, and lithium iron phosphate.

[0063] Although the above example uses a lithium-ion battery, those skilled in the art, upon reading this application, will realize that the silicon-based anode material of this application can be used in other suitable electrochemical devices. Such electrochemical devices include any apparatus where an electrochemical reaction occurs, and specific embodiments include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0064] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0065] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available. Example 1

[0066] 1. Preparation method of silicon-based anode materials Carbon particles with a diameter of 0.61~14μm were fed into the deposition zone of a vapor deposition tubular furnace. Air was removed, and argon gas was continuously introduced. The temperature was raised to 750℃, and 10% (v / v) carbon dioxide was introduced for vapor phase erosion for 5 hours to create an uneven carbon layer surface. The temperature was then raised to a vapor phase deposition temperature of 880℃, and silane gas was introduced. The silicon layer growth time was controlled to 1 hour, with a thickness ≤1.8μm. The temperature was then lowered to 650℃, and a hydrogen:acetylene = 1:3 (v / v) mixed gas was introduced for deposition to obtain a boundary carbon layer of 15~80nm. This layer was held at this temperature for 4 hours to maintain partial silicon dispersion, resulting in a silicon-based anode material.

[0067] 2. Structure of silicon-based anode materials The silicon-based anode material prepared in this embodiment includes, from the inside out, a core carbon layer, a gradient silicon-carbon composite layer, an intermediate silicon layer, a dispersed silicon layer, and a boundary carbon layer.

[0068] The core carbon layer is dense pure carbon with uniform carbon dispersion and a diameter of 4~11μm.

[0069] The gradient porous carbon layer encapsulates a core carbon layer and is contacted by a gradient-distributed silicon layer, making it a graphitized carbon material. The carbon content gradually decreases as the gradient porous carbon layer extends outwards. The layer thickness ranges from 600 to 4800 nm, and it contains multiple nanopores, a network structure of carbon formed by the porous structure, and gradually increasing amounts of embedded silicon.

[0070] A gradient-distributed silicon layer encapsulates a gradient-porous carbon layer, which is then in contact with an intermediate silicon layer, and the two layers are intercalated. The silicon content gradually increases as the gradient-distributed silicon layer extends outward. The thickness of the gradient-distributed silicon layer is 330–740 nm, and it contains nanopores and a gradually decreasing network structure of carbon due to the pores.

[0071] The intermediate silicon layer is encapsulated with a gradient-distributed silicon layer and surrounded by a dispersed silicon layer. The silicon distribution is relatively uniform and dispersed. The thickness of the intermediate silicon layer is 40~270nm, and the intermediate silicon layer has multiple nanopores, nanopores, and a network structure of carbon formed by the pores.

[0072] The dispersed silicon layer is connected to an intermediate silicon layer and an outer boundary carbon layer, extending into the boundary carbon layer; the thickness of the dispersed silicon layer is 45~95nm. When the dispersed silicon layer is formed by high-temperature carbonization to form the boundary carbon layer, the silicon in the intermediate silicon layer disperses to form a silicon layer at high temperature.

[0073] The boundary carbon layer, which encapsulates the dispersed silicon layer of the silicon-carbon anode material, is the outermost layer of the silicon-based anode material and contains no amorphous carbon material. The thickness of the boundary carbon layer ranges from 15 to 40 nm.

[0074] 3. Silicon electrode The mixed negative electrode material and conductive agent were stirred in a mixer for 30 minutes for the first mixing. Then, a binder and deionized water were added, and the mixture was stirred to control the solid content at 71%, then stirred again for 100 minutes for the second mixing. Next, the conductive agent, binder, and deionized water were added, and the solid content was controlled at 49%. A vacuum was then applied to a vacuum level of ≤-100 kPa, and the mixture was stirred for 150 minutes for the third mixing, yielding the silicon negative electrode slurry. This silicon negative electrode slurry was coated onto a negative electrode current collector, dried, and pressed into a sheet to form the silicon electrode. The mass ratio of the mixed negative electrode material, conductive agent, and binder was 95:2:3. The mixed negative electrode material consisted of 10% silicon-based negative electrode material and 90% carbon-coated artificial graphite; the conductive agent consisted of 10% conductive carbon black and 90% carbon nanotube conductive agent; and the binder consisted of 1 / 3 styrene-butadiene rubber and 2 / 3 sodium carboxymethyl cellulose.

[0075] 4. Lithium-ion batteries A battery cell is obtained by winding a silicon electrode, a separator, and a positive electrode sheet. The battery cell is then assembled into a battery case, dried, injected with electrolyte, sealed, formed, and tested for capacity to obtain a lithium-ion battery. Example 2

[0076] 1. Preparation method of silicon-based anode material Carbon particles with a diameter of 0.61~14μm were fed into the deposition zone of a vapor deposition tubular furnace. Air was vented, and argon gas was continuously introduced. The temperature was raised to 750℃, and 35% (v / v) carbon dioxide was introduced for vapor phase erosion for 2 hours to create an uneven carbon layer surface. The temperature was then raised to 800℃ for vapor phase deposition, and silane gas was introduced. The silicon layer growth time was controlled to 2 hours, with a thickness ≤1.8μm. The temperature was then lowered to 500℃, and a hydrogen:acetylene (1:4 (v / v) mixture was introduced for deposition to obtain a boundary carbon layer of 21~55nm. This layer was held at this temperature for 8 hours to maintain partial silicon dispersion, resulting in a silicon-based anode material.

[0077] 2. Structure of silicon-based anode materials The silicon-based anode material prepared in this embodiment includes, from the inside out, a core carbon layer, a gradient silicon-carbon composite layer, an intermediate silicon layer, a dispersed silicon layer, and a boundary carbon layer.

[0078] The core carbon layer is dense pure carbon with uniform carbon dispersion and a diameter of 4~12μm.

[0079] The gradient porous carbon layer encapsulates a core carbon layer and is contacted by a gradient-distributed silicon layer, making it a graphitized carbon material. The carbon content gradually decreases as the gradient porous carbon layer extends outwards. The layer thickness ranges from 720 to 4500 nm, and it contains multiple nanopores, a network structure of carbon formed by the pores, and gradually increasing amounts of embedded silicon.

[0080] A gradient-distributed silicon layer encapsulates a gradient-porous carbon layer, which is in contact with an intermediate silicon layer on the outside, and the two layers are intercalated. The silicon content gradually increases as the gradient-distributed silicon layer extends outward. The thickness of the gradient-distributed silicon layer is 310~550nm, and it has nanopores and a gradually decreasing network structure of carbon due to the pores.

[0081] The intermediate silicon layer is encapsulated with a gradient-distributed silicon layer and surrounded by a dispersed silicon layer. The silicon distribution is relatively uniform and dispersed. The thickness of the intermediate silicon layer is 44~175nm, and the intermediate silicon layer has multiple nanopores, nanopores, and a network structure of carbon formed by the pores.

[0082] The dispersed silicon layer is connected to an intermediate silicon layer and an outer boundary carbon layer, extending into the boundary carbon layer; the thickness of the dispersed silicon layer is 20~120nm. When the dispersed silicon layer is formed by high-temperature carbonization to form the boundary carbon layer, the silicon in the intermediate silicon layer disperses to form a silicon layer at high temperature.

[0083] The boundary carbon layer, which encapsulates the dispersed silicon layer of the silicon-carbon anode material, is the outermost layer of the silicon-based anode material and contains no amorphous carbon material. The thickness of the boundary carbon layer ranges from 17 to 45 nm.

[0084] 3. Silicon electrode The mixed negative electrode material and conductive agent were stirred in a mixer for 60 minutes for the first mixing. Then, a binder and deionized water were added, and the mixture was stirred to control the solid content at 70%, then stirred again for 150 minutes for the second mixing. Next, the conductive agent, binder, and deionized water were added, and the solid content was controlled at 47%. A vacuum was then applied to a vacuum degree of ≤-100 kPa, and the mixture was stirred for 180 minutes for the third mixing, yielding the silicon negative electrode slurry. This silicon negative electrode slurry was coated onto a negative electrode current collector, dried, and pressed into a sheet to obtain the silicon electrode. The mass ratio of the mixed negative electrode material, conductive agent, and binder was 92:3:5. The mixed negative electrode material consisted of 30% silicon-based negative electrode material and 70% carbon-coated artificial graphite; the conductive agent consisted of 10% conductive carbon black and 90% carbon nanotube conductive agent; and the binder consisted of 60% styrene-butadiene rubber, 30% sodium carboxymethyl cellulose, and 10% lithium polyacrylate.

[0085] 4. Lithium-ion batteries A battery cell is obtained by winding a silicon electrode, a separator, and a positive electrode sheet. The battery cell is then assembled into a battery case, dried, injected with electrolyte, sealed, formed, and tested for capacity to obtain a lithium-ion battery. Example 3

[0086] The difference between Example 3 and Example 1 is as follows: The mixed negative electrode material and conductive agent were stirred in a mixer for 30 minutes for the first mixing. Then, a binder and deionized water were added, and the mixture was stirred to control the solid content at 70%, then stirred again for 100 minutes for the second mixing. Next, the conductive agent, binder, and deionized water were added, and the solid content was controlled at 53%. A vacuum was then applied to a vacuum degree of ≤-100 kPa, and the mixture was stirred for 150 minutes for the third mixing, yielding a silicon negative electrode slurry. This silicon negative electrode slurry was coated onto a negative electrode current collector, dried, and pressed into a sheet to form a silicon electrode. The mass ratio of the mixed negative electrode material, conductive agent, and binder was 94:2.5:3.5. The mixed negative electrode material consisted of 10% silicon-based negative electrode material and 90% carbon-coated artificial graphite; the conductive agent consisted of 10% conductive carbon black and 90% carbon nanotube conductive agent; and the binder consisted of 1 / 3 styrene-butadiene rubber and 2 / 3 sodium carboxymethyl cellulose. Example 4

[0087] The difference between Example 4 and Example 1 is as follows: The mixed negative electrode material and conductive agent were stirred in a mixer for 30 minutes for the first mixing. Then, a binder and deionized water were added, and the mixture was stirred to control the solid content at 69%, then stirred again for 100 minutes for the second mixing. Next, the conductive agent, binder, and deionized water were added, and the solid content was controlled at 48%. A vacuum was then applied to a vacuum level of ≤-100 kPa, and the mixture was stirred for 150 minutes for the third mixing, yielding the silicon negative electrode slurry. This silicon negative electrode slurry was coated onto a negative electrode current collector, dried, and pressed into a sheet to form the silicon electrode. The mass ratio of the mixed negative electrode material, conductive agent, and binder was 93:3:4. The mixed negative electrode material consisted of 10% silicon-based negative electrode material and 90% carbon-coated artificial graphite; the conductive agent consisted of 10% conductive carbon black and 90% carbon nanotube conductive agent; and the binder consisted of 1 / 3 styrene-butadiene rubber and 2 / 3 sodium carboxymethyl cellulose. Example 5

[0088] The difference between Example 5 and Example 2 is as follows: The mixed negative electrode material and conductive agent were stirred in a mixer for 45 minutes for the first mixing. Then, a binder and deionized water were added, and the mixture was stirred to control the solid content at 71%, then stirred again for 100 minutes for the second mixing. Next, the conductive agent, binder, and deionized water were added, and the solid content was controlled at 48%. A vacuum was then applied to a vacuum level of ≤-100 kPa, and the mixture was stirred for 120 minutes for the third mixing, yielding the silicon negative electrode slurry. This silicon negative electrode slurry was coated onto a negative electrode current collector, dried, and pressed into a sheet to obtain the silicon electrode. The mass ratio of the mixed negative electrode material, conductive agent, and binder was 94:2:4. The mixed negative electrode material consisted of 20% silicon-based negative electrode material and 80% carbon-coated artificial graphite; the conductive agent consisted of 10% conductive carbon black and 90% carbon nanotube conductive agent; and the binder consisted of 60% styrene-butadiene rubber, 30% sodium carboxymethyl cellulose, and 10% lithium polyacrylate. Example 6

[0089] The difference between Example 6 and Example 2 is as follows: The mixed negative electrode material and conductive agent were stirred in a mixer for 45 minutes for the first mixing. Then, a binder and deionized water were added, and the mixture was stirred to control the solid content at 70%, then stirred again for 100 minutes for the second mixing. Next, the conductive agent, binder, and deionized water were added, and the solid content was controlled at 50%. A vacuum was then applied to a vacuum level of ≤-100 kPa, and the mixture was stirred for 120 minutes for the third mixing, yielding a silicon negative electrode slurry. This silicon negative electrode slurry was coated onto a negative electrode current collector, dried, and pressed into a sheet to form a silicon electrode. The mass ratio of the mixed negative electrode material, conductive agent, and binder was 93.5:2:4.5. The mixed negative electrode material consisted of 20% silicon-based negative electrode material and 80% carbon-coated artificial graphite; the conductive agent consisted of 10% conductive carbon black and 90% carbon nanotube conductive agent; and the binder consisted of 60% styrene-butadiene rubber, 30% sodium carboxymethyl cellulose, and 10% lithium polyacrylate. Example 7

[0090] The difference between Example 7 and Example 2 is as follows: The mixed negative electrode material and conductive agent were stirred in a mixer for 60 minutes for the first mixing. Then, a binder and deionized water were added, and the mixture was stirred to control the solid content at 72%, then stirred again for 180 minutes for the second mixing. Next, the conductive agent, binder, and deionized water were added, and the solid content was controlled at 51%. A vacuum was then applied to a vacuum degree of ≤-100 kPa, and the mixture was stirred for 130 minutes for the third mixing, yielding a silicon negative electrode slurry. This silicon negative electrode slurry was coated onto a negative electrode current collector, dried, and pressed into a sheet to obtain the silicon electrode. The mass ratio of the mixed negative electrode material, conductive agent, and binder was 92:3.5:4.5. The mixed negative electrode material consisted of 30% silicon-based negative electrode material and 70% carbon-coated artificial graphite; the conductive agent consisted of 10% conductive carbon black and 90% carbon nanotube conductive agent; and the binder consisted of 60% styrene-butadiene rubber, 30% sodium carboxymethyl cellulose, and 10% lithium polyacrylate. Example 8

[0091] The difference between Example 8 and Example 2 is as follows: The mixed negative electrode material and conductive agent were stirred in a mixer for 40 minutes for the first mixing. Then, a binder and deionized water were added, and the mixture was stirred to control the solid content at 71%, then stirred again for 180 minutes for the second mixing. Next, the conductive agent, binder, and deionized water were added, and the solid content was controlled at 50%. A vacuum was then applied to a vacuum level of ≤-100 kPa, and the mixture was stirred for 125 minutes for the third mixing, yielding the silicon negative electrode slurry. This silicon negative electrode slurry was coated onto a negative electrode current collector, dried, and pressed into a sheet to form the silicon electrode. The mass ratio of the mixed negative electrode material, conductive agent, and binder was 91:3.5:5.5. The mixed negative electrode material consisted of 30% silicon-based negative electrode material and 70% carbon-coated artificial graphite; the conductive agent consisted of 10% conductive carbon black and 90% carbon nanotube conductive agent; and the binder consisted of 60% styrene-butadiene rubber, 30% sodium carboxymethyl cellulose, and 10% lithium polyacrylate. Comparative Example 1

[0092] The difference between Comparative Example 1 and Example 1 is that: carbon dioxide vapor phase etching was not used, the carbon particles did not have an uneven surface, the gradient porous carbon layer could not be formed, and the gradient distribution silicon layer could not be formed during silane gas growth. Comparative Example 2

[0093] The difference between Comparative Example 2 and Example 1 is that a hydrogen:acetylene = 1:3 (v / v) gas mixture was not used for deposition, and no boundary carbon layer was formed.

[0094] Performance testing

[0095] 1. Expansion of silicon-containing negative electrode sheets The thickness of the silicon electrode after pressing was measured using a micrometer spiral ruler; the silicon electrode was obtained by disassembling the 100% SOC of the examples and comparative examples, and the thickness of the silicon electrode at 100% SOC was measured using a micrometer spiral ruler. The expansion rate of the silicon electrode = (thickness of the battery electrode at 100% SOC - thickness of the silicon electrode after pressing) / thickness of the negative electrode after pressing * 100%.

[0096] 2. Battery electrical performance testing At 25℃, with starting and stopping voltages of 2.8 V and 4.35 V respectively, the battery was first charged at 1C to 4.35 V, then charged at a constant voltage of 4.35 V until the current decreased to 0.05 C. Next, it was discharged at 0.5C to 2.8 V, then charged again at 1C to 4.35 V, then charged at a constant voltage of 4.35 V until the current decreased to 0.05 C, and finally discharged at 0.5C to 2.8 V. This charge-discharge cycle was repeated. The initial coulombic efficiency and capacity retention of the battery during the first charge-discharge cycle were recorded.

[0097] The results of the above tests are shown in Table 1-2.

[0098] Table 1. Expansion rates of silicon-containing anode sheets in Examples 1-6 and Comparative Examples 1-2

[0099] In Table 1, the expansion rates of the silicon-containing anode sheets in Examples 1-8 were all within 47%; the expansion rates of the silicon-containing anode sheets in Comparative Examples 1-2 were 56.7% and 50.4%, respectively, with Comparative Example 1 showing the highest expansion rate. This indicates that the absence of a gradient silicon-carbon composite layer has the greatest impact on the expansion of the silicon anode material. Therefore, by utilizing the interlocking of gradient porous carbon layers and gradient distributed silicon layers, the pores between the two layers share the expansion of the internal silicon, and the boundary carbon layer coats the dispersed silicon layer, effectively mitigating the expansion of the silicon anode material during cycling.

[0100] Table 2. Capacity retention rate of batteries in Examples 1-6 and Comparative Examples 1-2 at 25°C

[0101] Please refer to Table 2. It is not difficult to find that, compared with Examples 1-8, the batteries of Comparative Examples 1 and 2 show significant capacity decay at 100, 500, and 800 cycles. This indicates that the interlocking of the gradient porous carbon layer and the gradient distributed silicon layer, with the pores between the two sharing the expansion of the internal silicon and the boundary carbon layer covering the dispersed silicon layer, can greatly improve the capacity retention rate and improve the cycle stability of the battery.

[0102] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A silicon-based anode material, characterized in that, From the inside out, it includes a core carbon layer, a gradient silicon-carbon composite layer, an intermediate silicon layer, a dispersed silicon layer, and a boundary carbon layer. The carbon layer in the core area is a dense carbon layer; The gradient silicon-carbon composite layer includes a gradient porous carbon layer with gradually increasing porosity from the inside to the outside. Silicon is deposited in the pores of the gradient porous carbon layer, and the silicon content gradually increases from the inside to the outside to form a gradient distributed silicon layer. The intermediate silicon layer and the dispersed silicon layer are sequentially coated on the outside of the gradient silicon-carbon composite layer, and the boundary carbon layer is coated on the outside of the dispersed silicon layer, with some silicon particles in the dispersed silicon layer embedded in the boundary carbon layer.

2. The silicon-based anode material according to claim 1, characterized in that, The diameter of the carbon layer in the core region is 0.2~12μm; And / or, the thickness of the gradient porous carbon layer is 500~5000 nm; And / or, the thickness of the gradient-distributed silicon layer is 100~800nm; And / or, the thickness of the intermediate silicon layer is 20~500nm; And / or, the thickness of the boundary carbon layer is 15~80nm, and the thickness of the dispersed silicon layer is less than the thickness of the boundary carbon layer.

3. The silicon-based anode material according to claim 1, characterized in that, The carbon in the core carbon layer, the gradient porous carbon layer, and the boundary carbon layer includes at least one of graphitized carbon and amorphous carbon. And / or, the silicon in the gradient silicon-carbon composite layer, the intermediate silicon layer, and the dispersed silicon layer includes SiO2. x At least one of Si, 0 < x < 2.

4. The silicon-based anode material according to claim 1, characterized in that, The gradient-distributed silicon layer and the intermediate silicon layer are porous silicon layers, while the diffuse silicon layer is a non-porous silicon layer.

5. The silicon-based anode material according to claim 1, characterized in that, The silicon-based anode material contains 22% to 90% carbon. And / or, in the silicon-based anode material, the silicon content is 1-75%; And / or, the particle size D50 of the silicon-based anode material is 4.4~27μm; And / or, the tap density of the silicon-based anode material is 0.65~1.45 g / cm³. 3 ; And / or, the specific surface area of ​​the silicon-based anode material is 0.95~6.5m². 2 / g.

6. A method for preparing a silicon-based anode material as described in any one of claims 1-5, characterized in that, include: S1. Carbon particles are subjected to carbon dioxide vapor phase erosion under a protective atmosphere to form a porous structure on the surface of the carbon particles; the temperature of the vapor phase erosion is 450~800℃. S2. A silicon layer is deposited on the surface of the carbon particles using vapor deposition. S3. A carbon layer is deposited on the surface of the silicon layer using vapor phase deposition; the gas used for vapor phase deposition is a mixture of hydrogen and gas S, wherein gas S includes at least one of formaldehyde, acetaldehyde, methane, ethane, propane, acetylene, and propyne; S4. Heat preservation is performed to carbonize the carbon layer, thereby obtaining the silicon-based anode material.

7. The method for preparing the silicon-based anode material according to claim 6, characterized in that, In step S1: the protective atmosphere includes at least one of nitrogen, helium, neon, argon, krypton, and xenon; And / or, the carbon particles are graphitized carbon particles; the diameter of the carbon particles is 0.1~15 μm; And / or, the vapor phase erosion time is 3~12 h; In step S2: the gas used for vapor deposition is silane; And / or, the temperature of the vapor deposition is 700~1000℃; And / or, the vapor deposition time is 0.3~2 h; And / or, the thickness of the silicon layer is ≤1.8 μm; In step S3: the temperature of the vapor deposition is 400~700℃; In step S4: the heat preservation time is 3~8 hours.

8. The method for preparing the silicon-based anode material according to claim 7, characterized in that, In step S3: the volume ratio of hydrogen to gas S in the mixed gas is 1:1~6.

9. A silicon electrode, comprising a negative electrode current collector and a negative electrode material layer formed on at least one surface of the negative electrode current collector, characterized in that, The active material in the negative electrode material layer includes graphite negative electrode material, silicon-based negative electrode material according to any one of claims 1 to 5, or silicon-based negative electrode material prepared by the method according to any one of claims 6 to 8.

10. The silicon electrode according to claim 9, characterized in that, In the active material, the mass percentage of silicon-based anode material is 0.5% to 60%; And / or, in the negative electrode material layer, the mass ratio of active material, conductive agent and binder is 80~99 : 0.5~8 : 0.6~10.

11. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode and the negative electrode, characterized in that, The negative electrode is the silicon electrode as described in claim 9 or 10.

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