Silicon-carbon composite negative electrode material, and preparation method and application thereof

Abstract

This application relates to a silicon-carbon composite anode material, its preparation method, and its application. The silicon-carbon composite anode material has a core-shell structure, comprising, from the inside out: a core, which is a silicon-carbon composite matrix; an intermediate shell, which is a rigid tungsten nitride layer covering the outer surface of the silicon-carbon composite matrix; and an outer shell, which is a flexible conductive carbon layer covering the outer surface of the intermediate shell. This application proposes using tungsten nitride (W2N) as the inner rigid coating material to form a high-strength, conductive W2N protective layer on the surface of the silicon-carbon composite material, and further coating it with a flexible conductive carbon layer, constructing a "hard shell-soft layer" dual-layer synergistic protection structure, thereby systematically alleviating the key technical challenges of the aforementioned silicon-based anodes.

Description

Technical Field

[0001] This article relates to the field of lithium-ion batteries, specifically a silicon-carbon composite anode material, its preparation method, and its applications. Background Technology

[0002] Silicon (Si) is considered the most promising anode material for next-generation high-energy-density lithium-ion batteries due to its extremely high theoretical specific capacity (approximately 4200 mAh / g). However, it faces a fundamental challenge in practical applications: volume expansion and contraction exceeding 300% occurs during lithium insertion / extraction. This massive volume change is not an isolated problem but triggers a series of cascading, fatal technical difficulties, directly leading to a rapid decline in battery performance.

[0003] To address these challenges, various modification strategies for silicon anodes have been developed in this field, primarily including carbon coating, metal compound coating, and the introduction of flexible conductive networks. However, these existing strategies are limited by the properties of the materials themselves, and can only partially and non-systematically solve the problems, even introducing new drawbacks, ultimately leading to a performance trade-off dilemma of "pressing down one gourd only to have another float up." 1. Carbon Coating Technology: By coating a silicon surface with a carbon layer, the good toughness and conductivity of carbon can buffer volume expansion stress and improve electron conduction to a certain extent. However, carbon materials have limited mechanical modulus and are flexible buffer materials rather than rigid constraint materials. For the drastic expansion of silicon (>300%), its supporting strength is far from sufficient to prevent silicon particles from cracking and pulverizing due to repeated stress during long-term cycling. Particle pulverization further leads to the loss of connection between the active material and the conductive network, causing the electrode structure to collapse.

[0004] 2. Metal oxide / nitride coatings (e.g., Al2O3, TiO2, Si3N4): These materials possess advantages such as high hardness and high modulus, providing effective rigid confinement for silicon particles and suppressing pulverization to some extent. However, they are inherently semiconductors or insulators with extremely low electronic conductivity. Introducing such coatings severely hinders electron transport within the electrode, significantly increasing impedance and leading to a sharp decline in the battery's rate performance. Furthermore, their intrinsic lithium-ion conductivity is also poor, potentially affecting ion migration.

[0005] 3. Flexible conductive networks (such as CNTs and graphene): These networks improve the overall conductivity of the electrodes and provide porosity to accommodate volume expansion by constructing three-dimensional conductive networks. This strategy focuses on improvements at the macroscopic electrode scale but lacks direct, robust point-to-point support for the surface of individual silicon particles, failing to fundamentally address particle-level volume effects and interfacial instabilities. Furthermore, the network structure itself may experience fatigue and collapse under long-term cyclic stress.

[0006] In summary, existing technical solutions are limited by the singular properties of the coating materials, resulting in an inherent contradiction: pursuing rigid constraints sacrifices conductivity (such as metal compounds), while pursuing conductive buffering sacrifices support strength (such as carbon materials). This functional singularity at the material level prevents existing technologies from systematically solving a series of interconnected and comprehensive problems arising from volume expansion, including particle pulverization, interfacial instability (repeated SEI film rupture), limited rate performance, and electrode structure collapse.

[0007] Therefore, there is an urgent need in this field for an innovative material design approach, namely, to develop a new coating material that can simultaneously possess high mechanical strength (rigidity) and high electronic conductivity, thereby breaking the deadlock of the aforementioned performance trade-off from the source and providing a key solution for the practical application of high-performance silicon-carbon anodes. Summary of the Invention

[0008] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of this application.

[0009] To address this, this application proposes using tungsten nitride (W2N) as the inner rigid coating material to form a high-strength, conductive protective layer on the surface of the silicon-carbon composite material, and further coating it with a flexible conductive carbon layer to construct a "hard shell-soft layer" dual-layer synergistic protection structure, thereby systematically alleviating the key technical challenges of the aforementioned silicon-based anode.

[0010] Therefore, the first aspect of this application provides a silicon-carbon composite anode material, which has a core-shell structure and comprises, from the inside out: The core is a silicon-carbon composite matrix (Si / C). The intermediate shell layer is a rigid tungsten nitride (W2N) layer covering the outer surface of the silicon-carbon composite matrix; The outer shell layer is a flexible conductive carbon layer that covers the outer surface of the intermediate shell layer.

[0011] In one exemplary embodiment, the silicon-carbon composite matrix is ​​a particulate material with a particle size of 2-20 μm; preferably, the particle size is 5-20 μm, for example, 9 μm.

[0012] In one exemplary embodiment, the silicon-carbon composite matrix contains silicon in a mass fraction of 30 wt%-70 wt%, preferably 40 wt%-60 wt%, for example 40 wt%.

[0013] In one exemplary embodiment, the mass ratio of the silicon-carbon composite matrix to tungsten nitride is 95:5 to 70:30 (e.g., 10:1) to ensure that the tungsten nitride layer provides sufficient mechanical constraint and conductivity while avoiding a significant decrease in the specific capacity of the material due to an excessively high coating ratio.

[0014] In one exemplary embodiment, the thickness of the intermediate shell layer is 5-20 nm, for example, 15 nm.

[0015] In one exemplary embodiment, the thickness of the outer shell layer is 5-50 nm, for example 25 nm.

[0016] In one exemplary embodiment, the flexible conductive carbon in the outer shell layer is selected from one or more of nitrogen-doped carbon, graphitized carbon, carbon nanotubes, and graphene.

[0017] The second aspect of this application provides a method for preparing the above-mentioned silicon-carbon composite anode material, comprising: 1) Using vapor deposition, nano-silicon particles are uniformly loaded into a porous carbon matrix to obtain silicon-carbon composite matrix particles; 2) Using atomic layer deposition (ALD) or chemical vapor deposition (CVD) methods, with tungsten source and nitrogen source as precursors, a dense, continuous and uniform tungsten nitride thin film is deposited in situ on the surface of the silicon-carbon composite matrix particles. 3) By means of chemical vapor deposition (CVD), pyrolysis of carbon-containing precursors or coating of carbon nanomaterials, a flexible conductive carbon layer is introduced on the surface of the tungsten nitride film, and finally a silicon-carbon composite anode material with a multi-layer core-shell structure is obtained.

[0018] In one exemplary embodiment, the particle size of the nano-silicon particles is 50-200 nm.

[0019] In one exemplary embodiment, the porous carbon matrix has a particle size of 5-15 μm (e.g., 8 μm) and an internal pore size of 5-50 nm (e.g., 20 nm).

[0020] In one exemplary embodiment, the porous carbon matrix is ​​selected from one or more of resin porous carbon, bioporous porous carbon, petroleum-based porous carbon, and coal-based porous carbon.

[0021] In one exemplary embodiment, the tungsten source is any one or more of WF6, WCl6, and W(CO)6.

[0022] In one exemplary embodiment, the nitrogen source is any one or both of NH3, N2 / H2.

[0023] In an exemplary embodiment, step 1) specifically includes: providing the porous carbon matrix and pretreating it at 400-800°C in an inert atmosphere for 1-3 hours (e.g., 2 hours) to remove surface impurities and activate the pore structure; placing the treated porous carbon matrix in a chemical vapor deposition apparatus, introducing silicon source precursor gas at 450-650°C (e.g., 550°C), and performing decomposition deposition under the protection of an inert or reducing atmosphere, so that silicon forms uniformly dispersed nano-silicon particles on the surface and in the internal pores of the porous carbon matrix, thereby obtaining silicon-carbon composite matrix particles.

[0024] In one exemplary embodiment, in step 1), the inert atmosphere or reducing atmosphere is nitrogen, argon, or a nitrogen / hydrogen mixture, etc.

[0025] In one exemplary embodiment, in step 1), the silicon source precursor gas is a silane gas, selected from one or more of silane, ethyl silane, and silane derivatives.

[0026] In one exemplary embodiment, in step 1), the flow rate of the silicon source precursor gas is 5-100 sccm (e.g., 100 sccm), preferably 10-50 sccm; the ventilation time is 0.5-4h, preferably 1-3h (e.g., 2h).

[0027] In an exemplary embodiment, step 2) specifically includes: placing the silicon-carbon composite matrix particles obtained in step 1) in an atomic layer deposition or chemical vapor deposition reaction chamber, and alternately introducing tungsten source precursor and nitrogen source precursor at a deposition temperature of 250-450°C (e.g., 300°C) to allow them to undergo a surface confinement reaction on the surface of the silicon-carbon composite matrix, thereby allowing tungsten nitride to grow in situ on the surface of the silicon-carbon composite matrix particles and forming a continuous, dense and uniform tungsten nitride coating layer.

[0028] In one exemplary embodiment, in step 2), the flow rate of the tungsten source precursor is 5-50 sccm, preferably 10-30 sccm (e.g., 30 sccm).

[0029] In one exemplary embodiment, in step 2), the flow rate of the nitrogen source precursor is 50-500 sccm, preferably 100-300 sccm (e.g., 100 sccm).

[0030] In one exemplary embodiment, in step 2), the single introduction time of the tungsten source precursor is 0.1-5s, preferably 0.5-2s (e.g., 2s); the single introduction time of the nitrogen source precursor is 1-10s, preferably 2-6s (e.g., 5s).

[0031] In one exemplary embodiment, in step 2), the number of cycles for atomic layer deposition or chemical vapor deposition is 50-500, preferably 100-300 (e.g., 200).

[0032] In an exemplary embodiment, step 3) specifically includes: introducing the tungsten nitride-coated silicon-carbon composite particles obtained in step 2) into a carbon-containing precursor environment; using chemical vapor deposition, pyrolysis of organic carbon sources, or introduction of carbon nanomaterials followed by heat treatment (e.g., thermal decomposition) to decompose or deposit the carbon source at 600-900°C (e.g., 700°C); and forming a continuous coating layer of flexible conductive carbon on the surface of the tungsten nitride coating layer to obtain a silicon-carbon composite anode material with a multi-layer core-shell structure.

[0033] In one exemplary embodiment, in step 3), the heat treatment time is 0.5-10h, preferably 1-5h (e.g., 1.5h).

[0034] In one exemplary embodiment, in step 3), the carbon-containing precursor is acetylene.

[0035] The third aspect of this application provides a silicon-carbon composite anode material prepared by the above method.

[0036] The fourth aspect of this application provides a negative electrode sheet comprising the aforementioned silicon-carbon composite negative electrode material.

[0037] The fifth aspect of this application provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode is the aforementioned negative electrode.

[0038] Compared with the prior art, this application has the following technical effects: 1) Significantly improves structural stability: The W2N layer, as a high-strength "rigid skeleton", can effectively alleviate the severe volume expansion of Si during lithium insertion and extraction, reduce pulverization and electrode peeling, and significantly extend cycle life; 2) Improved electronic conductivity and rate performance: W2N has good metallic conductivity, and after coating, it can form a stable electron transport path. At the same time, the flexible conductive carbon layer can further construct a three-dimensional conductive network, effectively improving high-rate charge and discharge performance. 3) Enhanced interfacial stability: The W2N surface has excellent chemical inertness to the electrolyte, which can effectively inhibit electrolyte decomposition and side reactions, promote stable SEI film formation, reduce irreversible capacity loss, and improve the first coulombic efficiency.

[0039] 4) Construct a novel "hard + soft" dual-layer coating system: combine the rigid W2N layer with the flexible carbon layer to form a new coating structure that combines mechanical strength and flexibility adjustment, thereby achieving comprehensive protection of silicon-carbon anode particles and improving the long-term cycle capability and structural integrity of the material.

[0040] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the embodiments described in the description and the accompanying drawings. Attached Figure Description

[0041] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0042] Figure 1 The cycle performance of the negative electrode materials obtained in Example 1 and Comparative Example 1; Figure 2 The rate performance of the negative electrode materials obtained in Example 1 and Comparative Example 1; Figure 3 The electrochemical impedance spectroscopy (EIS) spectra of the negative electrode materials obtained in Example 1 and Comparative Example 1 are shown. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0044] The present application will be further described in detail below with reference to specific embodiments, but these embodiments should not be construed as limiting the present application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this invention.

[0045] The raw materials used in this application are all conventional products on the market.

[0046] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0047] Experimental methods not specified in the examples are generally performed under standard conditions or as recommended by the manufacturer.

[0048] Example 1 This embodiment provides a method for preparing a silicon-carbon anode material, including: 1) Provide a porous carbon matrix and pretreat it in a nitrogen atmosphere at 400-800℃ for 2h; place the pretreated porous carbon matrix in a chemical vapor deposition reactor, introduce silicon source precursor gas at a reaction temperature of 550℃, the flow rate of silicon source precursor gas is 100sccm, and decomposition deposition is carried out under nitrogen atmosphere protection for 2h to obtain silicon-carbon composite matrix particles. The porous carbon matrix is ​​a porous carbon material with an average particle size of 8 μm and an internal pore size of 20 nm; the silicon source precursor gas is silane, and the average particle size of the nano-silicon particles formed by deposition is 50 nm; the average particle size of the resulting silicon-carbon composite matrix is ​​9 μm, and the mass ratio of silicon to carbon is 4:6. 2) Place the silicon-carbon composite matrix particles obtained in step 1) into a chemical vapor deposition reaction chamber; at a deposition temperature of 300°C, alternately introduce tungsten source precursor and nitrogen source precursor to allow them to undergo a surface confinement reaction on the surface of the silicon-carbon composite matrix, so that tungsten nitride grows in situ on the surface of the silicon-carbon composite matrix particles, forming a continuous, dense and uniform tungsten nitride coating layer. The tungsten source precursor is tungsten hexachloride (WCl6), and the nitrogen source precursor is ammonia (NH3). The gas flow rate of the tungsten source precursor is 30 sccm, and the gas flow time is 2 s. The gas flow rate of the nitrogen source precursor is 100 sccm, and the gas flow time is 5 s. The deposition cycle is 200 times. 3) The tungsten nitride-coated silicon-carbon composite particles obtained in step 2) are introduced into a chemical vapor deposition reactor and carbon layer deposition is performed under nitrogen atmosphere protection. Acetylene (C2H2) is used as a carbon precursor and thermally decomposed at a deposition temperature of 700°C to deposit a flexible conductive carbon layer on the surface of the tungsten nitride coating. The deposition time is 1.5 hours, thereby forming a continuous flexible conductive carbon layer on the outside of the tungsten nitride coating, resulting in a silicon-carbon composite anode material with a multi-layer core-shell structure.

[0049] In the silicon-carbon composite anode material obtained in this embodiment, the thickness of the intermediate shell layer (tungsten nitride layer) is 15 nm; the thickness of the outer shell layer (flexible conductive carbon layer) is 25 nm; and the mass ratio of the silicon-carbon composite matrix to tungsten nitride is 10:1.

[0050] Comparative Example 1 The difference from Example 1 is that no intermediate rigid tungsten nitride coating layer was set, while the other preparation conditions were the same as in Example 1.

[0051] test: The performance parameters of the negative electrode materials in Example 1 and Comparative Example 1 were tested, and the results are shown in the figure. Figure 1-3 .in: Figure 1 The cycle performance of lithium-ion batteries containing the negative electrode materials obtained in Example 1 and Comparative Example 1 is shown. According to... Figure 1 It can be seen that after 683 cycles at a 1C rate, the capacity retention rate of Example 1 is 88%, and the capacity retention rate of Comparative Example 1 is 80%.

[0052] Figure 2 The rate performance of lithium-ion batteries containing the negative electrode materials obtained in Example 1 and Comparative Example 1 is shown. According to... Figure 2 It can be seen that at 5C, the capacity retention rate of Example 1 is 82.4%, and the capacity retention rate of Comparative Example 1 is 75%.

[0053] Figure 3 Electrochemical impedance spectroscopy (EIS) spectra of the negative electrode materials obtained in Example 1 and Comparative Example 1 are shown. The change in the diameter of the semicircle in the EIS spectra reflects the change in the interfacial charge transfer impedance. Figure 3 As can be seen, compared with Comparative Example 1, Example 1 still maintains a lower impedance after cycling, indicating that its interface stability is better.

[0054] Based on the above results, it can be seen that this application solves the following technical problems: 1) The contradiction between "high confinement" and "high conductivity": Overcoming the core defect of existing technologies where rigid coating layers (such as Al2O3) are insulating while conductive coating layers (such as carbon) are too soft, a single coating layer material (i.e. W2N layer) is provided that can both rigidly confine silicon expansion like ceramics and efficiently conduct electrons like metals.

[0055] 2) Balancing interface stability and ion transport efficiency: While applying rigid constraints, it is crucial to avoid hindering the normal insertion and extraction of lithium ions due to excessively thick coating layers or excessively low ion conductivity. This requires precise control of the W2N layer thickness and crystallinity to achieve an optimal balance between electron and ion transport and mechanical strength.

[0056] 3) The fundamental problem of long-term stability of SEI film: By utilizing the chemical inertness of W2N to electrolyte, the continuous decomposition and side reactions of electrolyte are fundamentally suppressed, solving the problem of repeated rupture and regeneration of SEI film caused by repeated exposure of silicon surface, thereby significantly improving the initial coulombic efficiency and long-term cycle life.

[0057] 4) Balancing electrode structure integrity and high rate performance: By suppressing pulverization through the W2N layer to ensure structural integrity, and utilizing its high conductivity to ensure electron transport, the silicon-carbon anode achieves a synergistic improvement in three dimensions: high specific capacity, long cycle life, and high rate performance, rather than the trade-offs and compromises of traditional solutions.

[0058] In summary, the silicon-carbon anode material in this application has the following structural features: 1) Construction of a rigid tungsten nitride (W2N) coating layer: A dense, continuous, and uniform tungsten nitride (W2N) layer is deposited in situ on the surface of silicon-carbon (Si / C) composite materials using ALD or CVD technology. This layer possesses excellent mechanical properties (high hardness, high modulus) and metallic conductivity, effectively encapsulating and supporting silicon particles, and effectively suppressing volume expansion and structural pulverization during cycling. 2) Achieve interface compatibility regulation between W2N layer and silicon-carbon composite matrix: Control the thickness of W2N layer in the range of 5-20nm to ensure that it can provide sufficient mechanical protection without significantly hindering lithium ion transport, while taking into account the chemical stability and interfacial adhesion strength with Si / C surface, which is conducive to the formation of stable and continuous SEI film. 3) Flexible conductive carbon layer composite coating structure design: A flexible conductive carbon layer (such as nitrogen-doped carbon, graphite, carbon nanotubes, etc.) is further introduced outside the W2N coating layer to form a synergistic double-layer coating structure of "rigid W2N shell + flexible conductive shell", which takes into account electron transport, stress buffering and interface stability. 4) Multi-scale synergistic regulation of structure-interface-performance relationship: Through the hierarchical design of the coating structure, a sandwich-type W2N@Si / C@Carbon structure is constructed to synergistically improve the overall performance of the electrode from multiple dimensions such as micro-stress relief, optimization of electronic / ion conduction paths, and SEI film stability.

[0059] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A silicon-carbon composite anode material, wherein the silicon-carbon composite anode material has a core-shell structure, comprising, from the inside out: The core is a silicon-carbon composite matrix; An intermediate shell layer, wherein the intermediate shell layer is a rigid tungsten nitride layer covering the outer surface of the silicon-carbon composite matrix; The outer shell layer is a flexible conductive carbon layer that covers the outer surface of the intermediate shell layer.

2. The silicon-carbon composite anode material according to claim 1, wherein, The silicon-carbon composite matrix is ​​a particulate material with a particle size of 2-20 μm; and / or In the silicon-carbon composite matrix, the mass fraction of silicon is 30wt%-70wt%.

3. The silicon-carbon composite anode material according to claim 1 or 2, wherein, The thickness of the intermediate shell is 5-20 nm; and / or The mass ratio of the silicon-carbon composite matrix to tungsten nitride is 95:5 to 70:

30.

4. The silicon-carbon composite anode material according to claim 1 or 2, wherein, The thickness of the outer shell layer is 5-50 nm; and / or The flexible conductive carbon in the outer shell layer is selected from one or more of nitrogen-doped carbon, graphitized carbon, carbon nanotubes, and graphene.

5. A method for preparing a silicon-carbon composite anode material according to any one of claims 1 to 4, comprising: 1) Using vapor deposition, nano-silicon particles are uniformly loaded into a porous carbon matrix to obtain silicon-carbon composite matrix particles; 2) Using atomic layer deposition or chemical vapor deposition, with tungsten source and nitrogen source as precursors, a dense, continuous and uniform tungsten nitride film is deposited in situ on the surface of the silicon-carbon composite matrix particles. 3) By means of chemical vapor deposition, pyrolysis of carbon-containing precursors or coating of carbon nanomaterials, a flexible conductive carbon layer is introduced on the surface of the tungsten nitride film, and finally a silicon-carbon composite anode material with a multi-layer core-shell structure is obtained. Optionally, the particle size of the silicon nanoparticles is 50-200 nm; Optionally, the porous carbon matrix has a particle size of 5-15 μm and an internal pore size of 5-50 nm; Optionally, the porous carbon matrix is ​​selected from one or more of resin porous carbon, bioporous porous carbon, petroleum-based porous carbon, and coal-based porous carbon; Optionally, the tungsten source is any one or more of WF6, WCl6, and W(CO)6; Optionally, the nitrogen source is any one or both of NH3, N2 / H2.

6. The method according to claim 5, wherein, Step 1) includes: providing the porous carbon matrix and pretreating it in an inert atmosphere at 400-800°C for 1-3 hours; placing the treated porous carbon matrix in a chemical vapor deposition reactor, introducing silicon source precursor gas at 450-650°C, and performing decomposition deposition under an inert or reducing atmosphere to obtain silicon-carbon composite matrix particles. Optionally, the inert atmosphere or reducing atmosphere is nitrogen, argon, or a nitrogen / hydrogen mixture. Optionally, the silicon source precursor gas is a silane gas, selected from one or more of silane, ethyl silane, and silane derivatives; Optionally, the flow rate of the silicon source precursor gas is 5-100 sccm, and the ventilation time is 0.5-4h.

7. The method according to claim 5 or 6, wherein, Step 2) includes: placing the silicon-carbon composite matrix particles obtained in step 1) in an atomic layer deposition or chemical vapor deposition reaction chamber, and alternately introducing tungsten source precursor and nitrogen source precursor at a deposition temperature of 250-450°C, so that they undergo a surface confinement reaction on the surface of the silicon-carbon composite matrix to form a continuous, dense and uniform tungsten nitride coating layer. Optionally, the flow rate of the tungsten source precursor is 5-50 sccm, and the flow rate of the nitrogen source precursor is 50-500 sccm; Optionally, the single introduction time of the tungsten source precursor is 0.1-5s; the single introduction time of the nitrogen source precursor is 1-10s. Optionally, the number of atomic layer deposition or chemical vapor deposition cycles is 50-500.

8. The method according to claim 5 or 6, wherein, Step 3) includes: introducing the tungsten nitride-coated silicon-carbon composite particles obtained in step 2) into a carbon-containing precursor environment; using chemical vapor deposition, pyrolysis of organic carbon source, or introduction of carbon nanomaterials and heat treatment, the carbon source is decomposed or deposited at 600-900℃ to obtain a silicon-carbon composite anode material with a multi-layer core-shell structure. Optionally, the heat treatment time is 0.5-10 hours.

9. A negative electrode sheet comprising the silicon-carbon composite negative electrode material according to any one of claims 1 to 4 or the silicon-carbon composite negative electrode material obtained by the method according to any one of claims 5 to 8.

10. A lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode is the negative electrode as described in claim 9.

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