Silicon / carbon composite negative electrode material with double carbon structure and preparation method thereof
By constructing a dual carbon structure consisting of a dynamic carbon framework and a static carbon layer, the conductivity and volume expansion problems of silicon-based anode materials in existing technologies have been solved, achieving silicon/carbon composite materials with high specific capacity and long cycle life, and optimizing the interface environment and electrode stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2025-12-26
- Publication Date
- 2026-06-09
AI Technical Summary
In existing technologies, silicon-based anode materials constructed from a single carbon source are insufficient in ensuring high conductivity and suppressing silicon volume expansion. The process is cumbersome and costly, making it difficult to achieve high specific capacity and long cycle life.
A dynamic carbon skeleton is formed by dynamic in-situ crosslinking of micron-sized silicon, cellulose acetate and trimethoxysilane. After mechanical ball milling with an organic carbon source, a static carbon layer is constructed, forming a silicon/carbon composite material with a dual carbon structure. The dynamic carbon skeleton adapts to changes in silicon volume, while the static carbon layer provides a stable conductive network.
It significantly improves the interface stability, rate performance, and cycle life of silicon-based materials. By using a dynamic carbon skeleton to buffer volume expansion and a static carbon layer to provide a stable conductive network and lithium-ion migration channel, it optimizes the interface environment, suppresses SEI film damage and side reactions, and achieves high specific capacity and high first coulombic efficiency.
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Figure CN122177774A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a silicon / carbon composite anode material with a dual carbon structure and its preparation method. Background Technology
[0002] Lithium-ion batteries, as highly efficient energy storage devices, have been widely used in consumer electronics and electric vehicles. With the market's increasing demands for battery energy density, the development of next-generation high-capacity anode materials is urgently needed. Silicon-based materials, especially micron-sized silicon, are particularly valuable due to their high energy density of up to 3579 mAh g⁻¹. -1 Its theoretical specific capacity is much higher than that of traditional graphite (372 mAh g). -1 Micron-sized silicon has become a highly promising alternative to nano-silicon. Compared with nano-silicon, micron-sized silicon has advantages such as lower cost, higher tap density, and better initial coulombic efficiency, making it easier to achieve commercial applications.
[0003] In existing technologies, constructing the coating layer using a "single carbon source" is one of the mainstream directions. For example, patent CN120280471A discloses a method using chitosan as a single carbon source, adding a metal chloride inducer, and then freeze-drying followed by one-step sintering to form a multi-level carbon coating structure. Patent CN118867168A uses a "conductive copolymer" as a single carbon precursor, forming a dense coating through its cross-linking network. The carbon layer structures formed by these patents are often simple and have limited functions, making it difficult to effectively restrain the volume expansion of silicon while ensuring high conductivity. Furthermore, the processes are cumbersome, costly, and lack controllability.
[0004] Therefore, in order to solve the above problems, it is urgent to develop a new method for preparing silicon-carbon composite materials that uses readily available raw materials, has a simple process, and can form an effective coating structure. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide a silicon / carbon composite anode material with a dual carbon structure and its preparation method. The invention involves forming a silicon-based precursor through dynamic in-situ crosslinking between micron-sized silicon, cellulose acetate, and trimethoxysilane. This precursor is then mechanically ball-milled with an organic carbon source and sintered in a tube furnace to obtain a silicon / carbon composite anode material with a dual carbon structure. This constructs a dual carbon structure with a synergistic effect of a "dynamic carbon skeleton and a static carbon layer." The "dynamic carbon skeleton" specifically refers to a disordered carbon layer formed by in-situ crosslinking and carbonization, tightly bonded to the silicon core through Si-OC bonds. This layer exhibits elasticity and can adaptively deform with the volume change of silicon during charging and discharging, thereby buffering internal stress and suppressing particle breakage in real time. The "static carbon layer" specifically refers to a continuous and dense carbon shell with a high degree of graphitization, formed by carbonization with an external organic carbon source, covering the dynamic carbon skeleton. This shell constructs a stable electronic conductivity network and provides channels for lithium-ion migration. This structure can significantly improve the interface stability, rate capability, and cycle life of silicon-based materials.
[0006] The specific preparation steps of this invention are as follows:
[0007] (1) Weigh a certain amount of micron-sized silicon powder and add it to NMP solvent. Stir at room temperature for 0.5-3 hours. After the powder is evenly dispersed, add a certain amount of trimethoxysilane and continue stirring for 2-6 hours. Then add a certain amount of cellulose acetate and continue stirring at room temperature for 4-6 hours. After the reaction is complete, wash the precipitated product with NMP solvent to remove unreacted substances and free components. Then vacuum dry at 60°C for 12-18 hours to obtain the Si-C crosslinked product.
[0008] (2) The Si-C crosslinking product obtained in step (1) is mechanically ball-milled with an organic carbon source at a speed of 300~400 r / min for 0.5~1 h to obtain a silicon-based precursor;
[0009] (3) The silicon-based precursor obtained in step (2) is placed in a tube furnace under the protection of argon atmosphere and heated to the target temperature at a heating rate of 2~20℃ / min. The target temperature is 200~800℃. The temperature is kept constant for 1~7h, then naturally cooled, ground and sieved to obtain the silicon / carbon composite anode material with dual carbon structure.
[0010] The beneficial effects of this invention are:
[0011] A dual carbon structure with a synergistic "dynamic carbon skeleton and static carbon layer" was successfully constructed on the surface of micron-sized silicon particles through in-situ crosslinking of cellulose acetate and trimethoxysilane and subsequent carbonization of sucrose. The inner layer forms a dynamic interface with the silicon nucleus through Si-OC chemical bonds. This interface can adaptively adjust to the volume change of silicon during charging and discharging, maintaining a firm anchor while providing elastic buffering capacity to alleviate volume expansion stress in real time and effectively suppress material pulverization. The outer layer forms a structurally stable static graphitized carbon shell through sucrose carbonization, constructing a durable and continuous conductive network. This not only greatly improves the electronic conductivity of the material but also provides more interfacial channels for the rapid migration of lithium ions. More importantly, this unique "dynamic-static" combination mechanism jointly optimizes the interfacial environment: the inner dynamic buffer reduces the damage of mechanical strain to the surface solid electrolyte interphase (SEI) film, while the outer dense carbon layer physically blocks the continuous side reactions between the electrolyte and the silicon nucleus, thereby guiding the formation of a thin and stable SEI film. Meanwhile, this mechanism can maintain the conductivity integrity of the electrode and promote the formation of a stable SEI film, thereby ensuring, at the mechanistic level, that the composite material ultimately achieves high specific capacity, high initial coulombic efficiency and cycle life, laying a solid foundation for promoting the commercial application of silicon-based anodes. Attached Figure Description
[0012] Figure 1 These are scanning electron microscope (SEM) images of the silicon-carbon materials with a dual carbon structure prepared in Examples 1, 2, and 3 of this invention.
[0013] Figure 2 These are transmission electron microscope (TEM) images of the silicon-carbon materials with a dual carbon structure prepared in Examples 2 and 3 of this invention.
[0014] Figure 3 These are charge-discharge curves of silicon-carbon materials with a dual carbon structure prepared in Examples 1, 2, and 3 of this invention.
[0015] Figure 4 This is a charge / discharge rate diagram of the silicon-carbon material with a dual carbon structure prepared in Examples 4 and 5 of this invention;
[0016] Figure 5 This is a cycle performance diagram of the silicon-carbon material with a dual carbon structure prepared in Examples 4 and 5 of this invention. Detailed Implementation
[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.
[0018] Example 1:
[0019] (1) Weigh out micron-sized silicon powder and add it to NMP solvent. Stir at room temperature for 0.5 h. After it is evenly dispersed, add trimethoxysilane and continue stirring for 2 h. Then add cellulose acetate and continue stirring at room temperature for 6 h. After the reaction is complete, wash the precipitated product with NMP solvent to remove unreacted substances and free components. Then vacuum dry at 60 °C for 12 h to obtain Si-C crosslinked product, wherein the size of micron-sized silicon particles is 5 μm, the mass ratio of micron-sized silicon to cellulose acetate is 10:1, the mass ratio of micron-sized silicon to trimethoxysilane is 1:15, and the mass concentration of micron-sized silicon powder in NMP is 20%.
[0020] (2) The Si-C crosslinking product obtained in step (1) was mechanically ball-milled with sucrose at a speed of 300 r / min for 1 h to obtain a silicon-based precursor;
[0021] (3) The powder obtained in step (2) is placed in a tube furnace under the protection of argon atmosphere and heated to 300°C at a heating rate of 5°C / min. The temperature is then kept constant at this temperature for 6 hours, and then cooled naturally. The powder is then ground and sieved to obtain the micron-sized silicon / carbon composite anode material.
[0022] Weigh 0.12g of the silicon-carbon composite anode material prepared in this example, 0.04g of acetylene black, and 0.04g of sodium alginate (SA), grind for 30min, then add 2mL of deionized water and continue grinding for 30min. Coat the viscous mixture evenly onto the copper foil, then pre-dry at 80℃ for 15min, and then dry in a vacuum oven at 80℃ for 12h. After that, roll the copper foil and cut it into round pieces with a diameter of 14mm to obtain the electrode sheet.
[0023] In an argon-filled glove box (O2 content < 1 ppm, water content < 1 ppm), the electrodes, separator, lithium foil, and nickel foam mesh were assembled into coin cells using conventional methods, and the electrochemical performance of the cells was tested on a constant current charge-discharge system.
[0024] The scanning electron microscope image of the silicon-carbon composite anode material with a dual carbon structure prepared in this embodiment is shown below. Figure 1 (a) The charge-discharge curves of the material in a lithium-ion battery are shown in Figure 1. Figure 3 .from Figure 1 (a) It can be seen that a continuous and initially dense carbon precursor coating layer has formed on the surface of the prepared composite material. From Figure 3 It can be seen from the data that the composite material prepared in this embodiment has a low initial charge-discharge efficiency, indicating that there is a large irreversible capacity loss in the first cycle.
[0025] Example 2:
[0026] (1) Weigh out micron-sized silicon powder and add it to NMP solvent. Stir at room temperature for 3 hours. After it is evenly dispersed, add trimethoxysilane and continue stirring for 6 hours. Then add cellulose acetate and continue stirring at room temperature for 4 hours. After the reaction is complete, wash the precipitated product with NMP solvent to remove unreacted substances and free components. Then vacuum dry at 60°C for 18 hours to obtain Si-C crosslinked product, wherein the size of micron-sized silicon particles is 5 μm, the mass ratio of micron-sized silicon to cellulose acetate is 10:1, the mass ratio of micron-sized silicon to trimethoxysilane is 1:15, and the mass concentration of micron-sized silicon powder in NMP is 20%.
[0027] (2) The Si-C crosslinking product obtained in step (1) was mechanically ball-milled with sucrose at a speed of 300~400 r / min for 1 h to obtain a silicon-based precursor;
[0028] (3) The powder obtained in step (2) is placed in a tube furnace under the protection of argon atmosphere and heated to 500°C at a heating rate of 5°C / min. The temperature is then kept constant for 6 hours until it is completely cooled. The powder is then taken out, ground, and sieved to obtain silicon-carbon composite anode material.
[0029] Weigh 0.12g of the silicon-carbon composite anode material prepared in this example, 0.04g of acetylene black, and 0.04g of sodium alginate (SA), grind for 30min, then add 2mL of deionized water and continue grinding for 30min. Coat the viscous mixture evenly onto the copper foil, then pre-dry at 80℃ for 15min, and then dry in a vacuum oven at 80℃ for 12h. After that, roll the copper foil and cut it into round pieces with a diameter of 14mm to obtain the electrode sheet.
[0030] In an argon-filled glove box (O2 content < 1 ppm, water content < 1 ppm), the electrodes, separator, lithium foil, and nickel foam mesh were assembled into coin cells using conventional methods, and the electrochemical performance of the cells was tested on a constant current charge-discharge system.
[0031] The scanning electron microscope and transmission electron microscope (TEM) results of the silicon-carbon composite anode material with a dual carbon structure prepared in this embodiment are shown below. Figure 1As shown in (b) and (d, e), it can be clearly observed from the figures that the overall particle dispersion is good, the surface is smooth and intact, and there is no obvious structural damage or exposed silicon phase, indicating that the coating layer is uniform and continuous. Further, high-resolution transmission electron microscopy (HRTEM) images reveal a typical double-coating structure: a well-crystallized silicon nucleus as the core, an outer layer of flexible amorphous carbon formed by carbonization of cellulose acetate, and an outer layer of dense graphitized carbon formed by carbonization of sucrose. The outer carbon layer has a uniform thickness of approximately 4-7 nm and completely coats the particle surface, forming a clear core-shell interface. This double-carbon structure effectively blocks direct contact between the electrolyte and the active silicon nucleus, suppressing side reactions and shortening the lithium-ion diffusion path. Furthermore, the Si-O-Si covalent bond interface constructed through trimethoxysilane forms a stable connection between the silicon nucleus and the inner carbon layer, further enhancing the structural integrity of the composite material during cycling, thereby significantly improving its electrochemical stability and cycle life.
[0032] The scanning electron microscope and transmission electron microscope (TEM) results of the silicon-carbon composite anode material with a dual carbon structure prepared in this embodiment are shown below. Figure 1 As shown in (b) and 2(d, e), the charge-discharge curves of the material in a lithium-ion battery are as follows: Figure 3 As clearly observed in the image, the particles are well-dispersed, with smooth and intact surfaces, and no obvious structural damage or exposed silicon phase, indicating a uniform and continuous coating layer. Further high-resolution transmission electron microscopy (HRTEM) images reveal a typical double-coating structure: a well-crystallized silicon nucleus at the core, surrounded by a flexible amorphous carbon inner layer formed by carbonization of cellulose acetate, and a dense graphitized carbon outer layer formed by carbonization of sucrose. The outer carbon layer has a uniform thickness of approximately 4-7 nm, completely coating the particle surface and forming a clear core-shell interface. This double-carbon structure effectively prevents direct contact between the electrolyte and the active silicon nucleus, suppressing side reactions and shortening the lithium-ion diffusion path. Figure 3 As can be seen from the data, the first discharge specific capacity of the composite material prepared in this embodiment is about 3250 mAhg⁻¹, and the first charge-discharge efficiency is significantly improved, indicating that the denser carbon layer formed after heat treatment effectively suppresses the irreversible side reaction and active lithium loss in the first cycle.
[0033] Example 3:
[0034] (1) Weigh out micron-sized silicon powder and add it to NMP solvent. Stir at room temperature for 2 hours. After it is evenly dispersed, add trimethoxysilane and continue stirring for 3 hours. Then add cellulose acetate and continue stirring at room temperature for 5 hours. After the reaction is complete, wash the precipitated product with NMP solvent to remove unreacted substances and free components. Then vacuum dry at 60°C for 15 hours to obtain Si-C crosslinked product, wherein the size of micron-sized silicon particles is 5 μm, the mass ratio of micron-sized silicon to cellulose acetate is 10:1, the mass ratio of micron-sized silicon to trimethoxysilane is 1:15, and the mass concentration of micron-sized silicon powder in NMP is 20%.
[0035] (2) The Si-C crosslinking product obtained in step (1) was mechanically ball-milled with sucrose at a speed of 350 r / min for 1 h to obtain a silicon-based precursor;
[0036] (3) The powder obtained in step (2) is placed in a tube furnace under the protection of argon atmosphere and heated to 700°C at a heating rate of 5°C / min. The temperature is then kept constant at this temperature for 6 hours. After complete cooling, the powder is taken out, ground, and sieved to obtain silicon-carbon composite anode material.
[0037] Weigh 0.12g of the silicon-carbon composite anode material prepared in this example, 0.04g of acetylene black, and 0.04g of sodium alginate (SA), grind for 30min, then add 2mL of deionized water and continue grinding for 30min. Coat the viscous mixture evenly onto the copper foil, then pre-dry at 80℃ for 15min, and then dry in a vacuum oven at 80℃ for 12h. After that, roll the copper foil and cut it into round pieces with a diameter of 14mm to obtain the electrode sheet.
[0038] In an argon-filled glove box (O2 content < 1 ppm, water content < 1 ppm), the electrodes, separator, lithium foil, and nickel foam mesh were assembled into coin cells using conventional methods, and the electrochemical performance of the cells was tested on a constant current charge-discharge system.
[0039] The scanning electron microscope and transmission electron microscope (TEM) results of the silicon-carbon composite anode material with a dual carbon structure prepared in this embodiment are shown below. Figure 1As shown in (c) and 2(f, g), the material as a whole still maintains its granular morphology, but significant roughening of some particle surfaces can be observed, and even signs of carbon layer cracking or peeling can be seen in local areas, indicating that the continuity and integrity of the carbon coating layer are affected at this higher temperature. Further high-magnification images reveal microcracks or pores on the carbon shell surface, and a certain degree of sintering adhesion between particles. This structural feature suggests that excessively high sintering temperatures may lead to over-graphitization of the outer carbon layer, increasing its brittleness and making it prone to defects during cooling or subsequent processing. Simultaneously, high temperatures may also cause coarsening or local agglomeration of silicon particles, affecting the uniform coating of the carbon layer. This structural defect directly leads to the electrolyte easily penetrating into the carbon layer, directly contacting the silicon nucleus and triggering continuous side reactions, thus adversely affecting the material's initial coulombic efficiency, rate performance, and long-term cycling stability.
[0040] The scanning electron microscope and transmission electron microscope (TEM) results of the silicon-carbon composite anode material with a dual carbon structure prepared in this embodiment are shown below. Figure 1 (c), 2(f, g), the charge-discharge curves of the material in the lithium-ion battery are shown in the figure. Figure 3 The material as a whole retains its granular morphology, but significant roughening of some particle surfaces is observed, with even localized areas showing signs of carbon layer cracking or peeling. This indicates that the continuity and integrity of the carbon coating layer are affected at this higher temperature. Further high-magnification images reveal microcracks or pores on the carbon shell surface, and a certain degree of sintering adhesion between particles. This structural feature suggests that excessively high sintering temperatures may lead to over-graphitization of the outer carbon layer, increasing its brittleness and making it prone to defects during cooling or subsequent processing. Simultaneously, high temperatures may also cause coarsening or localized agglomeration of silicon particles, affecting the uniform coating of the carbon layer. Figure 3 As can be seen from this embodiment, the initial discharge specific capacity of the composite material prepared in this embodiment is about 3000 mAh g⁻¹. Although the initial coulombic efficiency is high, it may exhibit faster capacity decay or higher voltage polarization in subsequent cycles.
[0041] Example 4:
[0042] (1) Weigh out micron-sized silicon powder and add it to NMP solvent. Stir at room temperature for 2 hours. After it is evenly dispersed, add trimethoxysilane and continue stirring for 4 hours. Then add cellulose acetate and continue stirring at room temperature for 4 hours. After the reaction is complete, wash the precipitated product with NMP solvent to remove unreacted substances and free components. Then vacuum dry at 60°C for 16 hours to obtain Si-C crosslinked product, wherein the size of micron-sized silicon particles is 5 μm, the mass ratio of micron-sized silicon to cellulose acetate is 10:1, the mass ratio of micron-sized silicon to trimethoxysilane is 1:15, and the mass concentration of micron-sized silicon powder in NMP is 20%.
[0043] (2) The Si-C crosslinking product obtained in step (1) was mechanically ball-milled with sucrose at a speed of 350 r / min for 1 h to obtain a silicon-based precursor;
[0044] (3) The powder obtained in step (2) is placed in a tube furnace under the protection of argon atmosphere and heated to 300°C at a heating rate of 8°C / min. The temperature is then kept constant at this temperature for 6 hours. After complete cooling, the powder is taken out, ground, and sieved to obtain silicon-carbon composite anode material.
[0045] Weigh 0.12g of the silicon-carbon composite anode material prepared in this example, 0.04g of acetylene black, and 0.04g of sodium alginate (SA), grind for 30min, then add 2mL of deionized water and continue grinding for 30min. Coat the viscous mixture evenly onto the copper foil, then pre-dry at 80℃ for 15min, and then dry in a vacuum oven at 80℃ for 12h. After that, roll the copper foil and cut it into round pieces with a diameter of 14mm to obtain the electrode sheet.
[0046] In an argon-filled glove box (O2 content < 1 ppm, water content < 1 ppm), electrodes, separators, lithium sheets, and nickel foam mesh were assembled into coin cells using conventional methods. The electrochemical performance of the cells was then tested on a constant current charge-discharge system. Rate cycling and cycle performance graphs are shown below. Figure 4 As shown in Figure 5, it can be seen from the figure that the discharge specific capacity of the silicon-carbon composite anode material with dual carbon structure prepared at current densities of 0.1, 0.2, 0.5, 1, 2 and 0.1 A / g shows a significant and continuous stepwise decrease, and the capacity decay over long cycles is quite obvious.
[0047] Example 5:
[0048] (1) Weigh out micron-sized silicon powder and add it to NMP solvent. Stir at room temperature for 2 hours. After it is evenly dispersed, add trimethoxysilane and continue stirring for 3 hours. Then add cellulose acetate and continue stirring at room temperature for 5 hours. After the reaction is complete, wash the precipitated product with NMP solvent to remove unreacted substances and free components. Then vacuum dry at 60°C for 15 hours to obtain Si-C crosslinked product, wherein the size of micron-sized silicon particles is 5 μm, the mass ratio of micron-sized silicon to cellulose acetate is 10:1, the mass ratio of micron-sized silicon to trimethoxysilane is 1:15, and the mass concentration of micron-sized silicon powder in NMP is 20%.
[0049] (2) The Si-C crosslinking product obtained in step (1) was mechanically ball-milled with sucrose at a speed of 350 r / min for 0.6 h to obtain a silicon-based precursor;
[0050] (3) The powder obtained in step (2) is placed in a tube furnace under the protection of argon atmosphere and heated to 500°C at a heating rate of 8°C / min. The temperature is then kept constant at this temperature for 6 hours. After complete cooling, the powder is taken out, ground, and sieved to obtain silicon-carbon composite anode material.
[0051] Weigh 0.12g of the silicon-carbon composite anode material prepared in this example, 0.04g of acetylene black, and 0.04g of sodium alginate (SA), grind for 30min, then add 2mL of deionized water and continue grinding for 30min. Coat the viscous mixture evenly onto the copper foil, then pre-dry at 80℃ for 15min, and then dry in a vacuum oven at 80℃ for 12h. After that, roll the copper foil and cut it into round pieces with a diameter of 14mm to obtain the electrode sheet.
[0052] In an argon-filled glove box (O2 content < 1 ppm, water content < 1 ppm), electrodes, separators, lithium sheets, and nickel foam mesh were assembled into coin cells using conventional methods. The electrochemical performance of the cells was then tested on a constant current charge-discharge system. Rate cycling and cycle performance graphs are shown below. Figure 4 As shown in Figure 5, the silicon-carbon composite anode material with a dual-carbon structure prepared at current densities of 0.1, 0.2, 0.5, 1, 2, and 0.1 A / g maintains high reversible capacity and excellent capacity recovery capability, indicating that the dual-carbon structure formed under these conditions possesses both high conductivity and fast ion migration channels. The long-cycle performance figure further confirms that the material exhibits extremely high capacity retention after 200 cycles at a current density of 1 A / g, demonstrating that its "dynamic-static" carbon layer synergy can continuously and effectively buffer volumetric stress and maintain the integrity of the electrode structure, achieving a stable combination of high specific capacity and ultra-long cycle life.
[0053] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.
Claims
1. A method for preparing a silicon / carbon composite anode material with a dual carbon structure, characterized in that: The specific steps are as follows: (1) Weigh a certain amount of micron-sized silicon powder and add it to NMP solvent. Stir at room temperature for 0.5-3 hours. After the mixture is evenly dispersed, add a certain amount of trimethoxysilane and continue stirring for 2-6 hours. Then add a certain amount of cellulose acetate and continue stirring at room temperature for 4-6 hours. After the reaction is complete, wash the precipitated product with NMP solvent to remove unreacted substances and free components. Then dry it under vacuum at 60°C for 12-18 hours to obtain the Si-C crosslinked product. (2) The Si-C crosslinking product obtained in step (1) is mechanically ball-milled with an organic carbon source at a speed of 300~400 r / min for 0.5~1 h to obtain a silicon-based precursor; (3) The silicon-based precursor obtained in step (2) is placed in a tube furnace under the protection of argon atmosphere and heated to the target temperature at a heating rate of 2~20℃ / min. The target temperature is 200~800℃. The temperature is kept constant for 1~7h, then naturally cooled, ground and sieved to obtain the silicon / carbon composite anode material with dual carbon structure.
2. The preparation method according to claim 1, characterized in that: In step (1), the size of the micron-sized silicon particles is 1~10μm, the mass ratio of micron-sized silicon to cellulose acetate is 1:1~20:1, the mass ratio of micron-sized silicon to trimethoxysilane is 1:1~1:30, and the mass concentration of micron-sized silicon powder in NMP is 10%~70%.
3. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of organic carbon source to micron-sized silicon is 1:5 to 1:20, and the types of organic carbon source include sucrose, glucose or polymer.
4. The preparation method according to claim 1, characterized in that: In step (3), the heating rate is 5~10℃ / min, the target temperature is 300~700℃, and the constant temperature holding time is 2~5h.
5. A silicon / carbon composite anode material prepared by the preparation method according to any one of claims 1-4, characterized in that: This material has a dual carbon structure.