A method for preparing silicon-carbon anode material, the silicon-carbon anode material and its applications

Abstract

This invention relates to a method for preparing a silicon-carbon anode material, the silicon-carbon anode material itself, and its applications. First, a multilayer oxide monomolecular isolation layer and a multilayer oxide monomolecular functional layer are formed by cyclic deposition on the outer surface and pore walls of microporous carbon using atomic layer deposition. Then, silicon deposition and carbon coating are performed to obtain the silicon-carbon anode material. Because the multilayer oxide monomolecular isolation layer of the silicon-carbon anode material can effectively block the reaction between the carbon source and active silicon, suppressing the occurrence of silicon carbide side reactions, while the multilayer oxide monomolecular functional layer can lower the lithium-ion migration barrier and improve ionic conductivity, applying the silicon-carbon anode material of this invention to lithium-ion batteries can effectively improve the first-cycle coulombic efficiency and cycle capacity retention of lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to a method for preparing a silicon-carbon anode material, the silicon-carbon anode material itself, and its applications. Background Technology

[0002] With the rapid development of the new energy industry, lithium-ion batteries are increasingly widely used in electric vehicles, energy storage systems, and portable electronic devices. At the same time, the market is placing higher demands on battery energy density, cycle life, and intrinsic safety. As a key component of batteries, the performance of the anode material has a decisive impact on the overall battery performance; therefore, developing advanced anode materials with high specific capacity and high stability has become a research focus.

[0003] Vapor-phase silicon-carbon anode materials are considered strong candidates for next-generation lithium-ion battery anode materials due to their excellent theoretical specific capacity and cycle stability. However, a series of key issues still exist for the practical application of high-specific-capacity vapor-phase silicon-carbon anodes:

[0004] During deposition or coating, the carbon source readily reacts with active silicon to form silicon carbide. The formation of silicon carbide not only consumes active silicon, reducing the material's theoretical capacity, but also forms a dense intermediate layer with high hardness and low conductivity. Especially when its thickness is uncontrollable, this severely hinders lithium-ion diffusion paths, reduces electrode electron transport efficiency, and thus accelerates capacity decay and reduces cycle performance. Furthermore, silicon carbide formation is a strongly exothermic process. If this reaction continues under extreme conditions such as battery operation or thermal runaway, it may trigger additional heat release, increasing the risk of thermal runaway and threatening the intrinsic safety of the battery system.

[0005] Therefore, there is an urgent need to develop a pretreatment method that can effectively suppress silicon carbide side reactions and improve interface stability and thermal safety while ensuring the integrity of carbon coating and conductive network structure. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing silicon-carbon anode materials, silicon-carbon anode materials, and their applications.

[0007] This invention employs atomic layer deposition (ALD) technology to construct a stable oxide intermediate layer on the outer surface and pore wall surface of microporous carbon. This oxide intermediate layer comprises a multilayer oxide monomolecular isolation layer and a multilayer oxide monomolecular functional layer. The multilayer oxide monomolecular isolation layer forms an isolation layer between the microporous carbon and the silicon nanomaterial layer, suppressing side reactions between carbon and silicon while improving the structural stability of the microporous carbon. The multilayer oxide monomolecular functional layer can reduce the migration barrier of lithium ions and improve ionic conductivity. The two oxide monomolecular layers work synergistically to significantly improve the cycle stability and thermal stability of the silicon-carbon anode material.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a silicon-carbon anode material based on oxide layer regulation, the preparation method comprising:

[0009] Step S1: A multilayer oxide monomolecular isolation layer is deposited on the outer surface and pore wall surface of the microporous carbon by atomic layer deposition to obtain the first composite microporous carbon; wherein, the oxide in the multilayer oxide monomolecular isolation layer includes one or more of aluminum oxide, zinc oxide, and zirconium oxide.

[0010] Step S2: A multilayer oxide monomolecular functional layer is deposited on the surface of the multilayer oxide monomolecular isolation layer by atomic layer deposition to obtain the second composite microporous carbon; wherein, the oxide in the multilayer oxide monomolecular functional layer includes titanium oxide;

[0011] Step S3: Deposit silicon nanomaterials on the surface of the multilayer oxide monomolecular functional layer of the second composite microporous carbon to obtain a silicon-carbon composite precursor.

[0012] Step S4: The silicon-carbon composite precursor is subjected to carbon coating treatment to form a carbon coating layer on the outer surface of the silicon-carbon composite precursor, thereby obtaining a silicon-carbon anode material.

[0013] Preferably, the microporous carbon includes one or more of the following: microporous resin carbon, microporous biomass carbon, microporous pitch coke, or microporous petroleum coke.

[0014] The average particle size Dv50 of the micro-mesoporous carbon is 4μm to 15μm, the porosity is 40% to 85%, and the pore size is 1nm to 10nm.

[0015] The specific surface area of ​​the microporous carbon is 800 m². 2 / g~1800m 2 / g, pore volume 0.7cm 3 / g~1.5cm 3 / g.

[0016] Preferably, step S1 specifically includes: placing the microporous carbon in the reaction chamber of an atomic layer deposition apparatus, evacuating the reaction chamber to a vacuum level of 1 Pa to 20 Pa, and then introducing the gas of the first oxide precursor into the reaction chamber through a first carrier gas, so that the first oxide precursor is deposited on the outer surface and pore walls of the microporous carbon. The C on the outer surface and pore wall surface of the microporous carbon is bonded to the -OH groups of the first oxide precursor, so that the first oxide precursor is electrostatically adsorbed on the outer surface and pore wall surface of the microporous carbon to form a first oxide precursor monolayer; then, a first inert gas is introduced to remove residual gas and byproducts, and then a first oxidizing gas source is introduced into the reaction chamber through a carrier gas, so that the first oxidizing gas source reacts with the first oxide precursor monolayer to generate an oxide monolayer. The above process is repeated 5 to 10 times to deposit multiple oxide monolayers on the outer surface and pore wall surface of the microporous carbon to obtain a first composite microporous carbon.

[0017] The first oxide precursor includes one or more of trimethylaluminum, diethylzinc, and tetra(dimethylamino)zirconium; the gas flow rate of the first oxide precursor is 50 mL / min to 120 mL / min, and the introduction time is 1 min to 10 min;

[0018] The first oxidizing gas source includes one or more of H2O, O3, and H2O2; the flow rate of the first oxidizing gas source is 0.2 L / min to 1 L / min, and the introduction time is 1 min to 10 min;

[0019] The first carrier gas includes one or more of nitrogen, argon, or helium; the flow rate of the first carrier gas is 1 L / min to 50 L / min.

[0020] The first inert gas includes one or more of nitrogen, argon, or helium; the flow rate of the first inert gas is 1 L / min to 50 L / min.

[0021] Preferably, step S2 specifically includes: continuing to introduce the gas of the second oxide precursor into the reaction chamber through the second carrier gas, so that the second oxide precursor is deposited on the surface of the multilayer oxide monomolecular isolation layer; then introducing the second inert gas to remove residual gas and byproducts; then introducing the second oxidizing gas source into the reaction chamber through the carrier gas, so that the second oxidizing gas source reacts with the second oxide precursor monomolecular layer to generate an oxide monomolecular functional layer; repeating the above process 1 to 5 times to deposit a multilayer oxide monomolecular functional layer on the outer surface and pore wall surface of the microporous carbon to obtain the second composite microporous carbon;

[0022] The second oxide precursor includes: titanium tetrachloride and / or tetrabutyl titanate; the gas flow rate of the second oxide precursor is 50 mL / min to 120 mL / min, and the introduction time is 1 min to 10 min;

[0023] The second oxidizing gas source includes one or more of H2O, O3, and H2O2; the flow rate of the second oxidizing gas source is 0.2 L / min to 1 L / min, and the introduction time is 1 min to 10 min;

[0024] The second carrier gas includes one or more of nitrogen, argon, or helium; the flow rate of the second carrier gas is 1 L / min to 50 L / min.

[0025] The second inert gas includes one or more of nitrogen, argon, or helium; the flow rate of the second inert gas is 1 L / min to 50 L / min.

[0026] Preferably, in step S3, silicon nanomaterials are deposited on the surface of the multilayer oxide monolayer functional layer of the second composite microporous carbon to obtain a silicon-carbon composite precursor, specifically including:

[0027] The second composite micro-mesoporous carbon is placed in a vapor deposition apparatus and heated to 500℃~700℃ at a heating rate of 1℃ / min~5℃ / min under a protective atmosphere. A silicon source gas is introduced and the temperature is maintained for 1 hour~5 hours, so that the silicon element decomposed by the silicon source gas is deposited on the surface of the multilayer oxide monomolecular functional layer and grown into silicon nanomaterials, thus obtaining a silicon-carbon composite precursor.

[0028] The silicon source gas includes one or more of the following: silane, silane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorosilane; the flow rate of the silicon source gas is 1 L / min to 100 L / min.

[0029] The protective gas in the protective atmosphere includes nitrogen and / or argon; the flow rate of the protective gas is 1 L / min to 50 L / min.

[0030] Preferably, in step S4, the carbon coating process is gas-phase carbon coating, which includes: placing the silicon-carbon composite precursor in a coating furnace, heating it to 300°C to 1000°C under a protective atmosphere, introducing carbon source gas, and holding it at that temperature for 1 hour to 10 hours, so that the carbon elements decomposed by the carbon source gas are deposited on the surface of the silicon-carbon composite precursor to obtain a silicon-carbon anode material.

[0031] The carbon source gas includes one or more of methane, ethane, propane, acetylene, propyne, butyne, propylene, and ethylene; the protective gas of the protective atmosphere includes nitrogen and / or argon; the flow rate of the carbon source gas is 1 L / min to 50 L / min.

[0032] In a second aspect, the present invention provides a silicon-carbon anode material prepared by the preparation method described in the first aspect, the silicon-carbon anode material comprising: a silicon-carbon composite precursor, and a carbon coating layer covering the surface of the silicon-carbon composite precursor;

[0033] The silicon-carbon composite precursor comprises: microporous carbon, a multilayer oxide monomolecular isolation layer deposited on the outer surface and pore wall surface of the microporous carbon, a multilayer oxide monomolecular functional layer deposited on the surface of the multilayer oxide monomolecular isolation layer, and silicon nanomaterials deposited and grown on the surface of the multilayer oxide monomolecular functional layer.

[0034] Preferably, the oxide in the multilayer oxide monomolecular isolation layer includes one or more of aluminum oxide, zinc oxide, and zirconium oxide;

[0035] The oxides in the multilayer oxide monomolecular isolation layer include: titanium oxide;

[0036] The silicon-carbon anode material contains 35wt% to 55wt% carbon, 43wt% to 63wt% silicon, and 0.05wt% to 2wt% total oxides.

[0037] The thickness of the multilayer oxide monomolecular isolation layer is between 0.5 nm and 1 nm;

[0038] The thickness of the multilayer oxide monomolecular functional layer is between 0.1 nm and 0.5 nm;

[0039] The thickness of the carbon coating layer is 1 nm to 25 nm.

[0040] Thirdly, the present invention provides a negative electrode sheet, the negative electrode sheet comprising a silicon-carbon negative electrode material prepared by the preparation method described in the first aspect, or a silicon-carbon negative electrode material described in the second aspect.

[0041] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode sheet described in the third aspect.

[0042] This invention provides a method for preparing a silicon-carbon anode material, the silicon-carbon anode material itself, and its applications. The method involves cyclically depositing multiple layers of oxide monomolecular isolation layers and multiple layers of oxide monomolecular functional layers on the pore walls of microporous carbon using atomic layer deposition (ALD). This is followed by silicon deposition and carbon coating to obtain the silicon-carbon anode material. Compared to dry / wet processes, chemical vapor deposition (CVD), and physical vapor deposition (PVD), ALD allows for precise control of the oxide monomolecular coating thickness by controlling the number of cycles, resulting in nanoscale ultrathin coatings. Furthermore, the coating formed by this process exhibits excellent three-dimensional conformability, making it suitable for substrate materials of different shapes and specific surface areas, and offering a wide selection of coating materials.

[0043] The silicon-carbon anode material obtained by the preparation method provided in this invention has a multilayer oxide monomolecular isolation layer that can effectively block the reaction between the carbon source and active silicon, suppress the occurrence of silicon carbide side reactions, and has a controllable oxide layer thickness. It does not affect lithium-ion diffusion and can stabilize the interface and limit volume expansion, significantly improving the thermal stability of the material under high temperature conditions and reducing the risk of thermal runaway. The multilayer oxide monomolecular functional layer can reduce the migration barrier of lithium ions, improve ionic conductivity, and thus improve rate and cycle performance. Under the synergistic effect of the multilayer oxide monomolecular isolation layer and the multilayer oxide monomolecular functional layer.

[0044] When the silicon-carbon anode material provided in this embodiment is applied to lithium-ion batteries, the first-cycle coulombic efficiency and multi-cycle capacity retention can be effectively improved through the synergistic effect of the multilayer oxide monomolecular isolation layer and the multilayer oxide monomolecular functional layer. Attached Figure Description

[0045] Figure 1 A flowchart illustrating the preparation method of silicon-carbon anode material provided in an embodiment of the present invention.

[0046] Figure 2 The images are scanning electron microscope (SEM) images of the silicon-carbon composite precursors provided in Embodiment 1 and Comparative Example 1 of the present invention.

[0047] Figure 3 The images show the X-ray diffraction (XRD) patterns of the silicon-carbon composite precursors prepared in Example 1 and Comparative Example 1 of this invention after heat treatment at different temperatures. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0049] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0050] This invention provides a method for preparing silicon-carbon anode materials based on oxide layer regulation, such as... Figure 1 As shown, the specific steps include:

[0051] Step S1: A multilayer oxide monomolecular isolation layer is deposited on the outer surface and pore wall surface of the micro-mesoporous carbon by atomic layer deposition to obtain the first composite micro-mesoporous carbon.

[0052] Specifically, the process includes: placing microporous carbon in the reaction chamber of an atomic layer deposition apparatus, evacuating the reaction chamber to a vacuum level of 1 Pa to 20 Pa, and then introducing the gas of the first oxide precursor into the reaction chamber through a first carrier gas, causing the first oxide precursor to deposit on the outer surface and pore walls of the microporous carbon. The carbon on the outer surface and pore walls of the microporous carbon bonds with the -OH groups of the first oxide precursor, allowing the first oxide precursor to form a first oxide precursor monolayer through electrostatic adsorption on the outer surface and pore walls of the microporous carbon. Next, a first inert gas is introduced to remove residual gas and byproducts. Then, a first oxidizing gas source is introduced into the reaction chamber through a carrier gas, causing the first oxidizing gas source to react with the first oxide precursor monolayer to generate an oxide monolayer. This process is repeated 5 to 10 times to deposit multiple oxide monolayers on the outer surface and pore walls of the microporous carbon, resulting in a first composite microporous carbon.

[0053] The microporous carbon includes one or more of the following: microporous resin carbon, microporous biomass carbon, microporous pitch coke, or microporous petroleum coke.

[0054] The average particle size Dv50 of the microporous carbon is 4μm to 15μm, the porosity is 40% to 85%, and the pore size is 1nm to 10nm.

[0055] The specific surface area of ​​the microporous carbon is 800 m². 2 / g~1800m 2 / g, pore volume 0.7cm 3 / g~1.5cm 3 / g.

[0056] The first oxide precursor includes one or more of trimethylaluminum, diethylzinc, and tetra(dimethylamino)zirconium; the gas flow rate of the first oxide precursor is 50 mL / min to 120 mL / min, and can be any value within this range, such as 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, 100 mL / min, 110 mL / min, 120 mL / min, etc., but is not limited to the listed values, and other unlisted ratios within this range are also applicable; the gas introduction time of the first oxide precursor is 1 min to 10 min, and can be any value within this range, such as 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc., but is not limited to the listed values, and other unlisted ratios within this range are also applicable.

[0057] The first oxidizing gas source includes one or more gases selected from H2O, O3, and H2O2; the flow rate of the first oxidizing gas source is 0.2 L / min to 1 L / min, and can be any value within this range, such as 0.2 mL / min, 0.3 mL / min, 0.4 mL / min, 0.5 mL / min, 0.6 mL / min, 0.7 mL / min, 0.8 mL / min, 0.9 mL / min, 1 L / min, etc., but is not limited to the listed values, and other unlisted ratios within this range are also applicable; the introduction time of the first oxidizing gas source is 1 min to 10 min, and can be any value within this range, such as 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc., but is not limited to the listed values, and other unlisted ratios within this range are also applicable.

[0058] The first carrier gas includes one or more of nitrogen, argon, or helium; the flow rate of the first carrier gas is 1 L / min to 50 L / min.

[0059] The first inert gas includes one or more of nitrogen, argon, or helium; the flow rate of the first inert gas is 1 L / min to 50 L / min.

[0060] The deposition process in step S1 can be repeated 5, 6, 7, 8, 9, or 10 times. Each cycle produces a monolayer of oxide monomolecule isolation layer with a thickness of approximately 0.1 nm to 0.3 nm. The thickness of the oxide monomolecule isolation layer can be measured using conventional methods, such as atomic force microscopy (AFM).

[0061] The oxides in the multilayer oxide monomolecular isolator include one or more of aluminum oxide, zinc oxide, and zirconium oxide. The multilayer oxide monomolecular isolator can improve the surface state of microporous carbon and its pore walls, which is beneficial for the uniform deposition of subsequent functional layers and silicon nanomaterials. Furthermore, it isolates silicon from carbon, suppresses the formation of SiC at high temperatures, and avoids the problem of SiC formation affecting material capacity.

[0062] Step S2: A multilayer oxide monomolecular functional layer is deposited on the surface of the multilayer oxide monomolecular isolation layer by atomic layer deposition to obtain the second composite microporous carbon.

[0063] In this process, the second oxide precursor is introduced into the reaction chamber of the atomic layer deposition apparatus via a second carrier gas, causing it to deposit on the surface of a multilayer oxide monomolecular isolation layer. Then, a second inert gas is introduced to remove residual gas and byproducts. Next, a second oxidizing gas source is introduced into the reaction chamber via the carrier gas, causing it to react with the second oxide precursor monomolecular layer to generate an oxide monomolecular functional layer. This process is repeated 1 to 5 times to deposit a multilayer oxide monomolecular functional layer on the outer surface and pore wall surface of the microporous carbon, resulting in a second composite microporous carbon.

[0064] The second oxide precursor includes titanium tetrachloride and / or tetrabutyl titanate; the gas flow rate of the second oxide precursor is 50 mL / min to 120 mL / min, and can be any value within this range, such as 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, 100 mL / min, 110 mL / min, 120 mL / min, etc., but is not limited to the listed values, and other unlisted ratios within this range are also applicable; the gas introduction time of the second oxide precursor is 1 min to 10 min, and can be any value within this range, such as 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc., but is not limited to the listed values, and other unlisted ratios within this range are also applicable.

[0065] The second oxidizing gas source includes one or more gases selected from H2O, O3, and H2O2; the flow rate of the second oxidizing gas source is 0.2 L / min to 1 L / min, and can be any value within this range, such as 0.2 mL / min, 0.3 mL / min, 0.4 mL / min, 0.5 mL / min, 0.6 mL / min, 0.7 mL / min, 0.8 mL / min, 0.9 mL / min, 1 L / min, etc., but is not limited to the listed values, and other unlisted ratios within this range are also applicable; the introduction time of the second oxidizing gas source is 1 min to 10 min, and can be any value within this range, such as 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc., but is not limited to the listed values, and other unlisted ratios within this range are also applicable.

[0066] The second carrier gas includes one or more of nitrogen, argon, or helium; the flow rate of the second carrier gas is 1 L / min to 50 L / min.

[0067] The second inert gas includes one or more of nitrogen, argon, or helium; the flow rate of the second inert gas is 1 L / min to 50 L / min.

[0068] The deposition process in step S2 can be repeated 1, 3, 4, 5, 6, or 7 times. Each cycle produces a monolayer of oxide with a single molecule functional layer thickness of approximately 0.1 nm to 0.3 nm. The thickness of this oxide monolayer can be measured using conventional methods, such as atomic force microscopy (AFM).

[0069] The oxides in the multilayer oxide monolayer include titanium oxide, which can act as a good ion conductor, reduce the migration barrier of lithium ions, and improve ionic conductivity, thereby improving the rate and cycle performance of the battery.

[0070] Step S3: Deposit silicon nanomaterials on the surface of the multilayer oxide monomolecular isolation layer of the second composite micro-mesoporous carbon to obtain a silicon-carbon composite precursor.

[0071] Specifically, the second composite micro-mesoporous carbon is placed in a vapor deposition apparatus and heated to 500℃~700℃ at a heating rate of 1℃ / min~5℃ / min under a protective atmosphere. A silicon source gas is introduced and the temperature is maintained for 1 hour~5 hours, so that the silicon element decomposed by the silicon source gas is deposited on the surface of the multilayer oxide monomolecular isolation layer and grown into silicon nanomaterials, thus obtaining a silicon-carbon composite precursor.

[0072] The silicon source gas includes one or more of the following: silane, silane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorosilane; the flow rate of the silicon source gas is 1 L / min to 100 L / min.

[0073] The protective atmosphere includes nitrogen and / or argon; the flow rate of the protective gas is 1 L / min to 50 L / min.

[0074] Step S4: The silicon-carbon composite precursor is subjected to carbon coating treatment to form a carbon coating layer on the outer surface of the silicon-carbon composite precursor, thereby obtaining the silicon-carbon anode material.

[0075] Specifically, the carbon coating process is gas phase carbon coating, which includes: placing the silicon-carbon composite precursor in a coating furnace, heating it to 300℃~1000℃ under a protective atmosphere, introducing carbon source gas, and holding it at the temperature for 1 hour to 10 hours, so that the carbon elements decomposed by the carbon source gas are deposited on the surface of the silicon-carbon composite precursor to obtain silicon-carbon anode material.

[0076] The carbon source gas includes one or more of methane, ethane, propane, acetylene, propyne, butyne, propylene, and ethylene; the protective gas for the protective atmosphere includes nitrogen and / or argon; the flow rate of the carbon source gas is 1 L / min to 50 L / min.

[0077] The silicon-carbon anode material prepared by the above preparation method provided in the embodiments of the present invention includes: a silicon-carbon composite precursor, and a carbon coating layer covering the surface of the silicon-carbon composite precursor;

[0078] The silicon-carbon composite precursor includes: microporous carbon, a multilayer oxide monomolecular isolation layer deposited on the outer surface and pore wall surface of the microporous carbon, a multilayer oxide monomolecular functional layer deposited on the surface of the multilayer oxide monomolecular isolation layer, and silicon nanomaterials deposited and grown on the surface of the multilayer oxide monomolecular functional layer.

[0079] The oxides in the multilayer oxide monomolecular separator include one or more of aluminum oxide, zinc oxide, and zirconium oxide. The number of oxide monomolecular separator layers is a positive integer, ranging from 5 to 10 layers, and can be any value within this range, such as 5, 6, 7, 8, 9, 10 layers, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0080] The total thickness of the multilayer oxide monomolecular isolation layer is 0.5nm to 1nm, and can be any value within this range, such as 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1.0nm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0081] The oxides in the multilayer oxide monomolecular functional layers include titanium oxide. The number of oxide monomolecular functional layers is a positive integer, ranging from 1 to 5 layers, and can be any value within this range, such as 1, 2, 3, 4, 5 layers, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0082] The total thickness of the multilayer oxide monomolecular functional layer is 0.1 nm to 0.5 nm, and can be any value within this range, such as 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0083] Silicon nanomaterials include, but are not limited to, one or more of the following: silicon nanoparticles, silicon nanoparticles arranged in close arrangement to form silicon islands, or silicon nanowires arranged in close arrangement to form silicon nanoparticles.

[0084] The carbon content in silicon-carbon anode materials is 35wt% to 55wt%, and can be any value within this range, such as: 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0085] The silicon content in silicon-carbon anode materials ranges from 43wt% to 63wt%, and can be any value within this range, such as 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0086] The total oxide content in silicon-carbon anode materials is 0.05wt% to 2wt%, and can be any value within this range, such as: 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2.0wt%, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0087] The thickness of the multilayer oxide monomolecular isolation layer is between 5 nm and 100 nm, and can be any value within this range, such as: 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0088] The thickness of the carbon coating layer is 1nm to 25nm, and can be any value within this range, such as: 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, etc., but is not limited to the listed values. Other unlisted ratios within this range are also applicable.

[0089] In this invention, particle size Dv50 refers to the volumetric median particle size of the material, representing the particle size corresponding to 50% of the material's volume distribution, a meaning known in the art. The particle size Dv50 of the material in this invention can be determined using instruments and conventional methods known in the art. Specifically, 1g of silicon-carbon anode material is weighed and added to 20ml of deionized water, followed by 50ul of a 1% (w / w) aqueous solution of ethyl phenyl polyethylene glycol dispersant. The mixture is sonicated for 5 minutes, and then the dispersion is added to a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd. for particle size determination. The Dv50 value is then read.

[0090] In this invention, the specific surface area of ​​the silicon-carbon composite precursor and the finished silicon-carbon anode material is tested using a specific surface area analyzer (model: Micromeritics ASAP2460). The sample is first sieved using a 200-mesh sieve. Then, degassing is performed, typically by placing the sample in a vacuum and heating it at 200°C for several hours (up to 6 hours). Next, nitrogen gas is introduced under a constant low temperature (-196°C), and the nitrogen pressure is controlled to allow the sample to adsorb and desorb at different pressures, obtaining isothermal adsorption-desorption curves. Finally, the specific surface area of ​​the sample is calculated using BET fitting based on these isothermal adsorption-desorption curves.

[0091] In this invention, the carbon content testing method involves using a carbon-sulfur analyzer (model Steel Research Nake CS-2800) to test the carbon content of the material. The testing principle is to oxidize the carbon in the sample into gases such as CO and CO2 at high temperature, and then use infrared spectroscopy to detect and analyze them, calculating the carbon and sulfur content in the sample. Furthermore, samples with a carbon content of not less than 6% and samples with a carbon content of less than 6% are defined as high-carbon samples and low-carbon samples, respectively. Different mass samples are required for testing: 50mg for high-carbon samples and 100mg for low-carbon samples. 2.5g and 2.1g of a special rare earth co-solvent are added to the samples, respectively, and the mixture is placed in a crucible and tested in the carbon-sulfur analyzer to read the carbon content test data.

[0092] The silicon-carbon anode material based on oxide layer regulation provided in this invention can be used as an anode active material to prepare anode sheets.

[0093] This invention provides a method for preparing a negative electrode sheet, which is a conventional method. Specifically, it includes: mixing the aforementioned silicon-carbon negative electrode material based on oxide layer regulation, other additive materials, and solvent in a specific ratio to form a slurry; coating the slurry onto both sides of a current collector; and drying to obtain the negative electrode sheet. The other additive materials include conductive materials and binders. The conductive materials include one or more of graphite conductive agents, conductive carbon black, and graphene; the graphite conductive agents include one or more of KS-6, KS-15, SFG-6, and SFG-15; the conductive carbon black includes one or more of acetylene black, Super P, Super S, 350G, carbon fiber VGCF, carbon nanotubes (CNTs), Ketjen black, and activated carbon. The binders include one or more of polyvinylidene fluoride (PVDF), PVDF-hexafluoropropylene copolymer, carboxymethyl cellulose, sodium carboxymethyl cellulose, polymethyl methacrylate, polyacrylic acid, polyacrylonitrile, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene (PTFE), polyacrylamide, polyvinyl acetate, or polyurethane. The solvents used in the preparation of the negative electrode sheet include one or more of deionized water, ethanol, acetone, or dimethyl ethyl ketone. The current collector includes, but is not limited to, copper foil.

[0094] The negative electrode sheet containing the silicon-carbon negative electrode material based on oxide layer regulation provided in the embodiments of the present invention can be assembled with an electrolyte / solid electrolyte, a separator, and a positive electrode sheet to form a lithium-ion battery. The lithium-ion battery includes a liquid lithium-ion battery, an all-solid-state lithium battery, or a semi-solid-state lithium battery. Because the multilayer oxide monomolecular insulating layer of the silicon-carbon negative electrode material can effectively block the reaction between the carbon source and active silicon, suppressing the occurrence of silicon carbide side reactions, while the multilayer oxide monomolecular functional layer can reduce the migration barrier of lithium ions and improve ionic conductivity, thereby enhancing rate capability and cycle performance, the synergistic effect of the multilayer oxide monomolecular insulating layer and the multilayer oxide monomolecular functional layer can effectively improve the first-cycle coulombic efficiency and cycle capacity retention of the lithium-ion battery.

[0095] To better understand the technical solution provided by the present invention, the preparation process and characteristics of the silicon-carbon anode material of the present invention are illustrated below with several specific examples.

[0096] Example 1

[0097] This embodiment provides a preparation process for silicon-carbon anode materials based on oxide layer regulation, as detailed below.

[0098] (1) 3 kg of microporous carbon was placed in the reaction chamber of an atomic layer deposition apparatus. After the reaction chamber was evacuated to a set vacuum level of 10 Pa, 50 mL / min of trimethylaluminum gas was introduced into the reaction chamber through nitrogen gas with a flow rate of 50 L / min for 1 min. This allowed the C on the outer surface and pore wall of the microporous carbon to bond with the -OH groups of trimethylaluminum, so that trimethylaluminum was electrostatically adsorbed onto the outer surface and pore wall of the microporous carbon to form a trimethylaluminum monolayer. Nitrogen gas was then introduced to remove residual gas and byproducts. Then, H2O gas was introduced into the reaction chamber through nitrogen gas with a flow rate of 1 L / min, so that the H2O gas reacted with the trimethylaluminum monolayer to generate an alumina monolayer. The above deposition process was repeated for a total of 5 cycles, and five layers of alumina monolayers were deposited on the outer surface and pore wall of the microporous carbon to obtain the first composite microporous carbon. Among them, the micro-mesoporous carbon is micro-mesoporous biomass carbon with a Dv50 of 10 μm, a porosity of 85%, an average pore size of 5 nm, and a specific surface area of ​​1800 m². 2 / g.

[0099] (2) Continue to introduce 50 mL / min of titanium tetrachloride gas into the reaction chamber through nitrogen gas at a flow rate of 50 L / min for 1 min, so that titanium tetrachloride is deposited on the surface of the five-layer alumina monomolecular isolation layer to form a titanium tetrachloride monomolecular layer; then introduce nitrogen gas to remove residual gas and by-products, and then introduce H2O gas into the reaction chamber through nitrogen gas at a flow rate of 1 L / min, so that H2O gas reacts with the titanium tetrachloride monomolecular layer to generate an alumina monomolecular functional layer. Repeat the above deposition process for a total of 5 cycles, depositing a five-layer titanium oxide monomolecular functional layer on the surface of the five-layer alumina monomolecular isolation layer to obtain the second composite microporous carbon.

[0100] (3) The two composite micro-mesoporous carbons are placed in a vapor deposition apparatus and heated to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere. Silane with a flow rate of 20L / min is introduced and kept at this temperature for 5 hours. This allows the silicon elements decomposed from the silicon source gas to be deposited on the surface of the titanium dioxide monomolecular functional layer and grown into silicon nanomaterials, thus obtaining the silicon-carbon composite precursor.

[0101] (4) The silicon-carbon composite precursor is placed in a coating furnace and heated to 500°C under a nitrogen atmosphere. Acetylene with a flow rate of 1L / min is introduced and kept at the temperature for 400min. The carbon elements decomposed from the carbon source gas are deposited on the surface of the silicon-carbon composite precursor to form a carbon coating layer, thus obtaining the silicon-carbon anode material.

[0102] SEM image of the silicon-carbon composite precursor prepared in step (3) of this embodiment, as shown below. Figure 2 As shown in (a).

[0103] The silicon-carbon anode material prepared in this embodiment was used to prepare electrode sheets and assembled into coin cell half-cells for testing. The specific process is as follows.

[0104] Preparation of electrode sheets: Weigh silicon-carbon anode material, conductive agent Super P, and binder polyvinylidene fluoride in a mass ratio of 8:1:1, add an appropriate amount of deionized water and stir evenly to prepare a slurry. Coat the slurry onto a copper foil current collector and dry it in a vacuum oven at 80°C for 12 hours to remove the solvent. Then cut the dried electrode sheet into a circular electrode sheet with a diameter of 14 mm and transfer the electrode sheet into a glove box filled with argon gas for later use.

[0105] Coin cell assembly process: In an argon-filled glove box, the prepared electrodes and lithium sheets are assembled into coin cells using conventional methods. The assembled cells use lithium hexafluorophosphate (LiPF6) electrolyte with a molar concentration of 1 mol / L. The electrolyte solvent is ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), with a volume ratio of EC, DMC, and DEC of 1:1:1. A polyethylene membrane is used as the separator.

[0106] Testing procedure for coin cell half-cells: The electrochemical performance of the assembled coin cell half-cells was tested using the Blue Battery Testing System, with the voltage window set to 0.01V–2V and the discharge rate set to 0.1C. The first-cycle coulombic efficiency was calculated using the formula: First-cycle coulombic efficiency = First-cycle charge specific capacity at 2.0V / First-cycle lithium intercalation capacity × 100%. Detailed test data for the first-cycle coulombic efficiency and cycle capacity retention after 600 cycles are shown in Table 1.

[0107] Example 2

[0108] This embodiment provides a preparation process for silicon-carbon anode material based on oxide layer regulation. The difference from Embodiment 1 is that the deposition process in step (1) is repeated 8 times, while the other preparation steps are the same as in Embodiment 1.

[0109] The silicon-carbon anode material prepared in this embodiment was used to fabricate electrode sheets and assemble them into coin cell half-cells for testing. The assembly and testing process of the coin cell half-cells was the same as in Example 1. Test data are detailed in Table 1.

[0110] Example 3

[0111] This embodiment provides a preparation process for silicon-carbon anode material based on oxide layer regulation. The difference from Embodiment 1 is that the deposition process in step (1) is repeated 10 times, while the other preparation steps are the same as in Embodiment 1.

[0112] The silicon-carbon anode material prepared in this embodiment was used to fabricate electrode sheets and assemble them into coin cell half-cells for testing. The assembly and testing process of the coin cell half-cells was the same as in Example 1. Test data are detailed in Table 1.

[0113] Example 4

[0114] This embodiment provides a process for preparing silicon-carbon anode material based on oxide layer regulation. The difference from Embodiment 1 is that the carbon coating treatment temperature in step (4) is 600°C, while the other preparation steps are the same as in Embodiment 1.

[0115] The silicon-carbon anode material prepared in this embodiment was used to fabricate electrode sheets and assemble them into coin cell half-cells for testing. The assembly and testing process of the coin cell half-cells was the same as in Example 1. Test data are detailed in Table 1.

[0116] Example 5

[0117] This embodiment provides a preparation process for silicon-carbon anode material based on oxide layer regulation. The difference from Example 1 is that the oxide precursor in step (1) is tetra(dimethylamino)zirconia, and the oxide layer formed is a multilayer zirconia layer. The other preparation steps are the same as in Example 1.

[0118] The silicon-carbon anode material prepared in this embodiment was used to fabricate electrode sheets and assemble them into coin cell half-cells for testing. The assembly and testing process of the coin cell half-cells was the same as in Example 1. Test data are detailed in Table 1.

[0119] To better illustrate the effects of the embodiments of the present invention, a comparative example is provided to be made with the embodiments described above.

[0120] Comparative Example 1

[0121] This comparative example provides a conventional silicon-carbon anode material preparation process. Unlike Example 1, it does not perform the atomic layer deposition process in steps (1) and (2), and does not form a multilayer oxide monomolecular isolation layer and a multilayer oxide monomolecular functional layer. Instead, it directly performs silicon deposition and carbon coating processes on the microporous carbon used in Example 1, that is, it directly performs the steps (3) and (4) of Example 1.

[0122] SEM image of the silicon-carbon composite precursor (without carbon coating) prepared in step (3) of this comparative example, as shown in the figure. Figure 2 As shown in (b).

[0123] Electrodes were prepared using the conventional silicon-carbon anode material used in this comparative example and assembled into coin cell half-cells for testing. The assembly and testing process for the coin cell half-cells was the same as in Example 1. Detailed test data are shown in Table 1.

[0124] Comparative Example 2

[0125] This comparative example provides a traditional silicon-carbon anode material preparation process. Unlike Example 4, it does not perform the atomic layer deposition process in steps (1) and (2), does not form a multilayer oxide monomolecular isolation layer and a multilayer oxide monomolecular functional layer, and directly performs silicon deposition and carbon coating process on microporous carbon. The carbon coating process is carried out at a temperature of 600°C.

[0126] The silicon-carbon anode material prepared in this comparative example was used to fabricate electrode sheets and assemble them into coin cell half-cells for testing. The assembly and testing process of the coin cell half-cells was the same as in Example 1. Detailed test data are shown in Table 1.

[0127] Comparative Example 3

[0128] This comparative example provides a preparation process for a silicon-carbon anode material. Unlike Example 1, step (1) atomic layer deposition is omitted. Instead, a liquid-phase pretreatment process is used, where aluminum isopropoxide is dissolved in ethanol, microporous carbon is added and mixed uniformly, followed by spray drying and a single calcination treatment. This causes the aluminum isopropoxide to decompose into alumina at a specific temperature, resulting in a silicon-carbon matrix material with an oxide coating in the pores and on the surface. Specifically, the mass concentration of aluminum isopropoxide in ethanol is 10%, the spray drying frequency is 220 Hz, the inlet temperature is 180°C, and the outlet temperature is 70°C. The single calcination treatment involves placing the spray-dried material in a box furnace, heating it to 500°C, and calcining for 1 hour.

[0129] Other preparation steps were the same as in Example 1. Electrodes were fabricated using the silicon-carbon anode material prepared in this comparative example and assembled into coin cells for testing. The assembly and testing processes for the coin cells were the same as in Example 1. Detailed test data are shown in Table 1.

[0130] Comparative Example 4

[0131] This comparative example provides a preparation process for a silicon-carbon anode material. Unlike Example 1, step (2) atomic layer deposition is not performed, and a multilayer oxide monomolecular functional layer is not formed. Instead, silicon deposition and carbon coating are directly performed on the first composite microporous carbon in step (1). The other preparation processes are the same as in Example 1.

[0132] The silicon-carbon anode material prepared in this comparative example was used to fabricate electrode sheets and assemble them into coin cell half-cells for testing. The assembly and testing process of the coin cell half-cells was the same as in Example 1. Detailed test data are shown in Table 1.

[0133] The uncoated silicon-carbon composite precursors provided in Example 1 and Comparative Example 1 of this invention were heat-treated at 700℃, 800℃, and 900℃, respectively. X-ray diffraction (XRD) tests were then performed on the heat-treated samples. The XRD patterns after heat treatment at different temperatures are shown below. Figure 2 As shown, the sample of Comparative Example 1 exhibited obvious SiC characteristic diffraction peaks after heat treatment at 700℃ and 800℃, indicating that a side reaction between silicon and carbon occurred at these temperatures, forming silicon carbide. Even when heated to 900℃, the sample of Example 1 showed weaker SiC diffraction peaks, indicating that the oxide layer obtained by ALD deposition effectively suppressed the direct reaction between silicon and the carbon matrix, significantly increasing the lower limit of the silicon carbide formation temperature and inhibiting SiC formation. These results demonstrate that oxide layer pretreatment can effectively construct a stable interface, delaying or avoiding side reactions, thereby improving the thermal stability and safety of the material.

[0134] Table 1 summarizes the test data for Examples 1-5 and Comparative Examples 1-4.

[0135]

[0136]

[0137] Table 1

[0138] The test data in Table 1 show that:

[0139] In Examples 1, 2, and 3, the number of cycles for depositing oxide monomolecular isolation layers was 5, 8, and 10, respectively. The test results showed that increasing the amount of oxide deposition could effectively improve the interfacial stability of the material, thereby improving the coulombic efficiency and cycle stability. However, when the number of deposition cycles continued to increase to 10 (Example 3), the performance improvement tended to stabilize.

[0140] Examples 2 and 4 compare coating temperatures of 500°C and 600°C. Comparative Examples 1 and 2 are samples without atomic layer deposition (ALD) treatment, coated at 500°C and 600°C respectively. Comparing Examples 2 and 4 with Comparative Example 1, it can be found that the samples pretreated with ALD show better first-cycle coulombic efficiency and capacity retention at higher coating temperatures. This indicates that in the untreated samples, silicon carbide side reactions easily occur between the carbon source and silicon, leading to active material loss, increased interfacial impedance, and a significant decrease in electrochemical performance. Particularly at higher coating temperatures (Comparative Example 2), the side reactions intensify, resulting in a more significant performance decline. Constructing an oxide layer through ALD effectively blocks these side reactions, improving first-cycle efficiency and significantly enhancing cycling stability.

[0141] Comparative Example 3, which uses a liquid-phase pretreatment method to construct an oxide layer, showed lower first-week coulombic efficiency and capacity retention compared to the sample in Example 1, which used atomic layer deposition (ALD) to construct an oxide layer. This is because ALD, compared to liquid-phase treatment, allows for precise control of the coating thickness by controlling the number of cycles, resulting in nanoscale ultrathin coatings. Furthermore, ALD deposits single-atom films layer by layer onto the substrate surface, resulting in a highly uniform and dense coating with low porosity, which is more effective in preventing side reactions.

[0142] Comparative Example 4, which did not have a multilayer oxide monolayer, exhibited lower first-cycle coulombic efficiency and cycle capacity retention compared to Example 1. This is because the multilayer oxide monolayer can reduce the lithium-ion migration barrier, increase ionic conductivity, and thus improve cycle performance.

[0143] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing silicon-carbon anode materials based on oxide layer regulation, characterized in that, The preparation method includes: Step S1: A multilayer oxide monomolecular isolation layer is deposited on the outer surface and pore wall surface of the microporous carbon by atomic layer deposition to obtain the first composite microporous carbon; wherein, the oxide in the multilayer oxide monomolecular isolation layer includes one or more of aluminum oxide, zinc oxide, and zirconium oxide. Step S2: A multilayer oxide monomolecular functional layer is deposited on the surface of the multilayer oxide monomolecular isolation layer by atomic layer deposition to obtain the second composite microporous carbon; wherein, the oxide in the multilayer oxide monomolecular functional layer includes titanium oxide. Step S3: Deposit silicon nanomaterials on the surface of the multilayer oxide monomolecular functional layer of the second composite microporous carbon to obtain a silicon-carbon composite precursor. Step S4: The silicon-carbon composite precursor is subjected to carbon coating treatment to form a carbon coating layer on the outer surface of the silicon-carbon composite precursor, thereby obtaining a silicon-carbon anode material.

2. The preparation method according to claim 1, characterized in that, The microporous carbon includes one or more of the following: microporous resin carbon, microporous biomass carbon, microporous pitch coke, or microporous petroleum coke. The average particle size Dv50 of the micro-mesoporous carbon is 4μm to 15μm, the porosity is 40% to 85%, and the pore size is 1nm to 10nm. The specific surface area of ​​the microporous carbon is 800 m². 2 / g~1800m 2 / g, pore volume 0.7cm 3 / g~1.5cm 3 / g.

3. The preparation method according to claim 1, characterized in that, Step S1 specifically includes: placing microporous carbon in the reaction chamber of an atomic layer deposition apparatus, evacuating the reaction chamber to a vacuum level of 1 Pa to 20 Pa, and then introducing the gas of the first oxide precursor into the reaction chamber through a first carrier gas, so that the first oxide precursor is deposited on the outer surface and pore walls of the microporous carbon. The C on the outer surface and pore wall surface of the microporous carbon is bonded to the -OH group of the first oxide precursor, so that the first oxide precursor is electrostatically adsorbed on the outer surface and pore wall surface of the microporous carbon to form a first oxide precursor monolayer; then, a first inert gas is introduced to remove residual gas and byproducts, and then a first oxidizing gas source is introduced into the reaction chamber through a carrier gas, so that the first oxidizing gas source reacts with the first oxide precursor monolayer to generate an oxide monolayer. The above process is repeated 5 to 10 times to deposit multiple oxide monolayers on the outer surface and pore wall surface of the microporous carbon to obtain the first composite microporous carbon. The first oxide precursor includes one or more of trimethylaluminum, diethylzinc, and tetra(dimethylamino)zirconium; the gas flow rate of the first oxide precursor is 50 mL / min to 120 mL / min, and the introduction time is 1 min to 10 min; The first oxidizing gas source includes one or more of H2O, O3, and H2O2; the flow rate of the first oxidizing gas source is 0.2 L / min to 1 L / min, and the introduction time is 1 min to 10 min; The first carrier gas includes one or more of nitrogen, argon, or helium; the flow rate of the first carrier gas is 1 L / min to 50 L / min. The first inert gas includes one or more of nitrogen, argon, or helium; the flow rate of the first inert gas is 1 L / min to 50 L / min.

4. The preparation method according to claim 1, characterized in that, Step S2 specifically includes: continuing to introduce the gas of the second oxide precursor into the reaction chamber through the second carrier gas, so that the second oxide precursor is deposited on the surface of the multilayer oxide monomolecular isolation layer; then introducing the second inert gas to remove residual gas and byproducts; then introducing the second oxidizing gas source into the reaction chamber through the carrier gas, so that the second oxidizing gas source reacts with the second oxide precursor monomolecular layer to generate an oxide monomolecular functional layer; repeating the above process 1 to 5 times to deposit a multilayer oxide monomolecular functional layer on the surface of the multilayer oxide monomolecular isolation layer to obtain the second composite microporous carbon. The second oxide precursor includes: titanium tetrachloride and / or tetrabutyl titanate; the gas flow rate of the second oxide precursor is 50 mL / min to 120 mL / min, and the introduction time is 1 min to 10 min; The second oxidizing gas source includes one or more of H2O, O3, and H2O2; the flow rate of the second oxidizing gas source is 0.2 L / min to 1 L / min, and the introduction time is 1 min to 10 min; The second carrier gas includes one or more of nitrogen, argon, or helium; the flow rate of the second carrier gas is 1 L / min to 50 L / min. The second inert gas includes one or more of nitrogen, argon, or helium; the flow rate of the second inert gas is 1 L / min to 50 L / min.

5. The preparation method according to claim 1, characterized in that, In step S3, silicon nanomaterials are deposited on the surface of the multilayer oxide monolayer functional layer of the second composite microporous carbon to obtain a silicon-carbon composite precursor, specifically including: The second composite micro-mesoporous carbon is placed in a vapor deposition apparatus and heated to 500℃~700℃ at a heating rate of 1℃ / min~5℃ / min under a protective atmosphere. A silicon source gas is introduced and the temperature is maintained for 1 hour~5 hours, so that the silicon element decomposed by the silicon source gas is deposited on the surface of the multilayer oxide monomolecular functional layer of the second composite micro-mesoporous carbon and grown into silicon nanomaterials, thus obtaining a silicon-carbon composite precursor. The silicon source gas includes one or more of the following: silane, silane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorosilane; the flow rate of the silicon source gas is 1 L / min to 100 L / min. The protective gas in the protective atmosphere includes nitrogen and / or argon; the flow rate of the protective gas is 1 L / min to 50 L / min.

6. The preparation method according to claim 1, characterized in that, In step S4, the carbon coating process is gas phase carbon coating, which includes: placing the silicon-carbon composite precursor in a coating furnace, heating it to 300℃~1000℃ under a protective atmosphere, introducing carbon source gas, and holding it at the temperature for 1 hour to 10 hours, so that the carbon elements decomposed by the carbon source gas are deposited on the surface of the silicon-carbon composite precursor to obtain silicon-carbon anode material. The carbon source gas includes one or more of methane, ethane, propane, acetylene, propyne, butyne, propylene, and ethylene; the protective gas of the protective atmosphere includes nitrogen and / or argon; the flow rate of the carbon source gas is 1 L / min to 50 L / min.

7. A silicon-carbon anode material prepared by any one of the preparation methods according to claims 1-6, characterized in that, The silicon-carbon anode material includes: a silicon-carbon composite precursor, and a carbon coating layer covering the surface of the silicon-carbon composite precursor; The silicon-carbon composite precursor includes: microporous carbon, a multilayer oxide monomolecular isolation layer deposited on the outer surface and pore wall surface of the microporous carbon, a multilayer oxide monomolecular functional layer deposited on the surface of the multilayer oxide monomolecular isolation layer, and silicon nanomaterials deposited and grown on the surface of the multilayer oxide monomolecular functional layer. The oxides in the multilayer oxide monomolecular isolation layer include one or more of aluminum oxide, zinc oxide, and zirconium oxide. The oxides in the multilayer oxide monomolecular functional layer include titanium oxide.

8. The silicon-carbon anode material according to claim 7, characterized in that, The silicon-carbon anode material contains 35wt% to 55wt% carbon, 43wt% to 63wt% silicon, and 0.05wt% to 2wt% total oxides. The thickness of the multilayer oxide monomolecular isolation layer is between 0.5 nm and 1 nm; The thickness of the multilayer oxide monomolecular functional layer is between 0.1 nm and 0.5 nm; The thickness of the carbon coating layer is 1 nm to 25 nm.

9. A negative electrode sheet, characterized in that, The negative electrode sheet comprises a silicon-carbon negative electrode material prepared by any one of the preparation methods according to claims 1-6, or a silicon-carbon negative electrode material according to any one of claims 7-8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode sheet as described in claim 9.

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