Highly conductive silicon-carbon in-situ encapsulated carbon cage composite material, and preparation method and application thereof

Abstract

The application discloses a high-conductivity silicon-carbon in-situ encapsulated carbon cage composite material and a preparation method and application thereof, and belongs to the field of lithium ion battery negative electrode materials. A fluidized bed reactor is adopted, ferrocene is mixed with toluene and is sprayed through atomization, nano silicon powder is used as a matrix, under argon fluidization, temperature is raised, ethane and hydrogen are synchronously introduced, and a three-dimensional conductive carbon cage layer is induced to grow in-situ on the surface of silicon particles. The composite material obtained by the application has firm interface bonding between the carbon cage network and the silicon matrix, greatly improves the electronic conductivity, and provides an effective buffer space for the volume expansion of silicon. Meanwhile, the preparation process is continuous and controllable, and is easy to scale up, and the prepared silicon-carbon composite material has a wide application prospect in the field of lithium batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode materials, specifically relating to a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material, its preparation method, and its application. Background Technology

[0002] With the rapid development of portable electronic products and electric vehicles, the demand for high-energy-density, long-life lithium-ion batteries is becoming increasingly urgent. Commercial graphite anodes, with a theoretical capacity of only 372 mAh / g, are gradually failing to meet the requirements of next-generation energy storage systems. Silicon materials, with their ultra-high theoretical specific capacity of approximately 4200 mAh / g, have become a research hotspot. However, they experience severe volume expansion and contraction (>300%) during repeated lithium insertion and extraction, which easily leads to the pulverization of active materials, instability of electrode structure, and continuous damage to the solid electrolyte interface film, resulting in rapid capacity degradation of the battery.

[0003] To suppress the volume effect of silicon, combining silicon with carbon materials has proven to be an effective technical approach. The carbon layer can both buffer volumetric strain and enhance electronic conductivity. Existing carbon coating technologies include liquid-phase pyrolysis and vapor-phase deposition, but most methods produce dense, continuous carbon layers lacking a three-dimensional conductive network, making it difficult to provide sufficient electron channels and stress release space during rapid charge and discharge processes. Furthermore, traditional processes often require multiple steps or pre-loading of catalysts, resulting in poor interfacial bonding, uneven coating, and poor batch stability.

[0004] Therefore, further research is still needed to improve silicon-carbon composite materials prepared by existing traditional processes. Summary of the Invention

[0005] In view of the content mentioned in the background art, the purpose of this invention is to provide a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material, its preparation method and application, aiming to overcome the defects of existing silicon-carbon anode materials such as imperfect conductive network, insufficient volume expansion buffering capacity and complex preparation process, and to provide a method for in-situ construction of a three-dimensional single-walled carbon nanotube conductive cage structure on the surface of micron / nano silicon particles, so as to achieve a unity of high conductivity and high structural stability.

[0006] To achieve the above objectives, the present invention specifically adopts the following technical solution: This invention provides a method for preparing a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material, comprising the following steps: Step 1: Mix the catalyst precursor with the dispersion medium, then pass it into a fluidized bed and pressurize it to form micro-droplet spray; Step 2: Add nano-silicon powder into a fluidized bed reactor and maintain the fluidization of silicon particles under protective gas. Step 3: Heat the system to 850-950℃ and keep it at that temperature. Introduce carbon source gas and auxiliary carrier gas to perform vapor phase coating deposition on the flowing silicon particles, inducing the in-situ growth of conductive carbon cages on the silicon surface. Finally, wash and dry to obtain a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material.

[0007] Furthermore, the catalyst precursor in step one is ferrocene, and the dispersion medium is toluene.

[0008] Furthermore, in step one, the mass ratio of the catalyst precursor to toluene is 1:(10-20); the diameter of the microdroplets after atomization is controlled at 5-20 μm.

[0009] Furthermore, in step two, the particle size of the nano-silicon powder is 30-100 nm, the mass ratio of the catalyst precursor to the nano-silicon powder is 1:(4-6), and the protective gas is argon with a flow rate of 100-300 mL / min.

[0010] Traditional methods typically employ liquid / solid carbon sources such as pitch, phenolic resin, or glucose, forming a dense, continuous amorphous or low-graphitized carbon layer on the surface of silicon particles through liquid-phase coating followed by pyrolysis. However, this structure lacks a three-dimensional conductive network, has limited volume expansion buffering capacity, and usually requires high temperatures of 2300-3000℃ to achieve graphitization. Based on this, this invention utilizes fluidized bed chemical vapor deposition (FCVD) technology, using ferrocene as a catalyst precursor, ethane as a gaseous carbon source, hydrogen as a carrier gas, and argon as a protective gas. At a relatively low temperature of 850-950℃, nano-iron particles released by the pyrolysis of ferrocene catalyze the in-situ cracking of ethane, directly growing single-walled carbon nanotubes on the surface of nano-silicon through a gas-liquid-solid (VLS) or gas-solid-solid (VSS) mechanism. These carbon nanotubes intertwine to form a three-dimensional conductive carbon cage network with high porosity and high elasticity.

[0011] In the preparation system of this invention: ferrocene is decomposed in high-temperature argon gas to generate nanoscale iron active centers; the iron particles adsorb ethane molecules and promote the breaking of their CH bonds; carbon atoms dissolve and diffuse as sp... 2 Hybrid graphene layers precipitate and curl into single-walled carbon nanotubes. Simultaneously, the catalytic effect of iron significantly reduces the graphitization activation energy, allowing the graphitization process, which originally required temperatures above 2300℃, to be completed at 850-950℃. Hydrogen plays a role in inhibiting carbon deposition and regulating the size of the carbon nanotubes. Compared to traditional dense carbon layers, this in-situ carbon cage structure not only significantly improves electron conduction efficiency through a three-dimensional line contact network, but also utilizes the flexibility of the carbon nanotubes and the voids within the cage to provide an effective mechanical buffer for the volume expansion of silicon. Furthermore, the in-situ chemical bonding interfaces formed between the carbon nanotubes and the silicon surface (such as Si-C bonds or SiC transition layers) significantly enhance the interfacial bonding strength, resulting in superior conductivity, cycle stability, and process continuity compared to traditional silicon-carbon anode materials.

[0012] Furthermore, in step three, the system heating rate is 5-10℃ / min, and the holding time is 30-60 min.

[0013] Furthermore, in step three, the carbon source gas is ethane, the auxiliary carrier gas is hydrogen, and the volume ratio of ethane to hydrogen is 1:(1-3); the duration of the gas phase coating deposition reaction is 30-120 min.

[0014] In the preparation of silicon-carbon composite materials by catalytic chemical vapor deposition, the method of catalyst introduction has a decisive influence on the structural uniformity and electrochemical performance of the final product. Some existing techniques pre-mix nano-silicon with a catalyst precursor to form a suspension, which is then fed into the reactor for deposition. However, this method has the following inherent drawbacks: First, the catalyst is prone to agglomeration in the suspension, leading to uneven growth of subsequent carbon nanotubes, with localized overgrowth or undergrowth; second, the contact between the catalyst and the silicon particle surface in the suspension is random physical adsorption, lacking selectivity and resulting in low catalyst utilization; third, an additional drying step is required after liquid-phase mixing, making the process cumbersome and increasing energy consumption; furthermore, agglomerated catalyst particles can catalyze the formation of large-diameter multi-walled carbon nanotubes or even carbon fibers, instead of the single-walled carbon nanotubes required in this invention, severely affecting the quality of the conductive network construction.

[0015] This invention makes a key improvement in the catalyst introduction method: atomized spraying is used to introduce a ferrocene / toluene solution into a fluidized bed in the form of fine droplets. Compared with the method of premixing nano-silicon and catalyst into a suspension before introduction, this method has the following significant advantages: the atomized fine droplets (5~20 μm) rapidly vaporize within the fluidized bed, releasing ferrocene in a molecularly dispersed state, avoiding catalyst agglomeration due to surface tension during the liquid-phase premixing stage. In contrast, in the suspension premixing method, ferrocene easily forms localized high-concentration areas on the surface of silicon particles, leading to uneven iron nanoparticle size and thus catalyzing the formation of multi-walled carbon nanotubes of varying diameters instead of uniform single-walled carbon nanotubes. Furthermore, atomized spraying allows ferrocene vapor to dynamically contact the fluidized silicon particles in the gas phase, resulting in uniform adsorption of ferrocene molecules onto the silicon particle surface, which, after high-temperature decomposition, generates uniform (2~5 nm) iron nanoparticles in situ. In the suspension premixing method, the catalyst is already adsorbed on the silicon surface in the liquid phase. During the drying process, due to the capillary force of the liquid, the catalyst will migrate to the particle contact point, causing a ring effect. This results in the iron particles being distributed in a ring-shaped and uneven manner, which seriously affects the uniformity of carbon nanotube growth.

[0016] Furthermore, in step three, the washing process involves first acid washing with dilute hydrochloric acid, followed by washing with deionized water until neutral; the concentration of dilute hydrochloric acid is 0.5%-5%, the acid washing time is 30-120 min, and the temperature is 25-60℃; the drying process uses vacuum drying, with a temperature of 60-80℃ and a time of 6-12 h.

[0017] Another objective of this invention is to provide a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material obtained by the above preparation method.

[0018] Another objective of this invention is to provide the application of the above-mentioned highly conductive silicon-carbon in-situ encapsulated carbon cage composite material in the preparation of lithium-ion battery anode materials.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. The process of this invention introduces ferrocene / toluene solution into the gas phase after atomizing it into fine droplets, avoiding the problems of catalyst agglomeration and uneven distribution in traditional suspension premixing methods. This ensures the uniformity of iron nanoparticle size generated in situ on the silicon surface, laying the foundation for the growth of a uniform single-walled carbon nanotube network. The nano-iron particles generated by the high-temperature decomposition of ferrocene in a fluidized bed catalyze ethane cracking, directly growing single-walled carbon nanotubes on the silicon surface to form a three-dimensional carbon cage coating layer with high porosity and high conductivity, significantly improving electron migration efficiency. Furthermore, the catalyst is introduced simultaneously with the carbon source in gas phase, achieving a single-process completion of catalysis-deposition-coating. The carbon nanotube network and the silicon substrate form an in-situ chemical bonding interface, with a bonding strength far exceeding that of traditional physical mixing or post-loading methods.

[0020] 2. This invention effectively overcomes the technical defects of suspension premixing, such as the need for independent mixing and drying, long process flow, and difficulty in ensuring batch-to-batch stability. The overall process can realize continuous and quantitative supply of catalyst without additional drying process, which is suitable for industrial continuous production. Attached Figure Description

[0021] Figure 1 This is a comparison chart showing the cycle performance test of soft-pack full batteries prepared with composite material samples obtained in the embodiments and comparative examples of the present invention.

[0022] Figure 2 This is a scanning electron microscope image of the composite material obtained in Example 1 of the present invention.

[0023] Figure 3 This is a scanning electron microscope image of the composite material obtained in Example 2 of the present invention.

[0024] Figure 4 This is a scanning electron microscope image of the composite material obtained in Example 3 of the present invention.

[0025] Figure 5 This is a scanning electron microscope image of the composite material obtained in Comparative Example 1 of the present invention.

[0026] Figure 6 This is a scanning electron microscope image of the composite material obtained in Comparative Example 2 of the present invention.

[0027] Figure 7 This is a scanning electron microscope image of the composite material obtained in Comparative Example 3 of the present invention.

[0028] Figure 8 This is a scanning electron microscope image of the composite material obtained in Comparative Example 4 of the present invention.

[0029] Figure 9 The Raman spectral characterization results are shown for the composite material obtained in Example 3 of this invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] Example 1 A preparation process for a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material includes the following steps: 1. Mix and dissolve ferrocene and toluene at a mass ratio of 1:10, inject the mixture into the fluidized bed auxiliary pressurized gas path and atomize it, controlling the average droplet size to be 10 μm.

[0033] 2. Take nano-silicon powder with an average particle size of 50 nm (ferrocene to silicon powder mass ratio of 1:5) and add it to the fluidized bed reactor. Purge with 200 mL / min argon gas to maintain particle fluidization. Heat to 950℃ at a rate of 8℃ / min and maintain the temperature for 45 min.

[0034] 3. Subsequently, the two gases were introduced simultaneously at a volume ratio of ethane:hydrogen = 1:2, with a total flow rate of 3 L / min, and the reaction was continued for 60 min to form a carbon cage layer of interwoven single-walled carbon nanotubes on the surface of the silicon particles.

[0035] 4. The above-deposited product was added to a 2% (w / w) dilute hydrochloric acid solution and stirred and acid-washed for 60 min under a 40°C water bath to remove residual ferrocene catalyst particles and reaction byproducts. After acid washing, it was repeatedly washed with deionized water until the pH of the washing solution was neutral, and then placed in a vacuum drying oven and dried at 70°C for 8 h to obtain a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material.

[0036] Example 2 A preparation process for a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material includes the following steps: 1. Mix and dissolve ferrocene and toluene at a mass ratio of 1:15, inject the mixture into the fluidized bed auxiliary pressurized gas path and atomize it, controlling the average droplet size to be 10 μm.

[0037] 2. Take nano-silicon powder with an average particle size of 30 nm (ferrocene to silicon powder mass ratio of 1:5) and add it to the fluidized bed reactor. Purge with 150 mL / min argon gas to maintain particle fluidization. Heat to 950℃ at a rate of 10℃ / min and maintain the temperature for 30 min.

[0038] 3. Subsequently, the two gases were introduced simultaneously at a volume ratio of ethane to hydrogen of 1:1, with a total flow rate of 3 L / min, and the reaction was continued for 90 min to form a carbon cage layer of interwoven single-walled carbon nanotubes on the surface of the silicon particles.

[0039] 4. The above-deposited product was added to a 2% (w / w) dilute hydrochloric acid solution and stirred and acid-washed for 60 min under a 40°C water bath to remove residual ferrocene catalyst particles and reaction byproducts. After acid washing, it was repeatedly washed with deionized water until the pH of the washing solution was neutral, and then placed in a vacuum drying oven and dried at 70°C for 8 h to obtain a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material.

[0040] Example 3 A preparation process for a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material includes the following steps: 1. Mix and dissolve ferrocene and toluene at a mass ratio of 1:20, inject the mixture into the fluidized bed auxiliary pressurized gas path and atomize it, controlling the average droplet size to be 15 μm.

[0041] 2. Take nano-silicon powder with an average particle size of 80 nm (ferrocene to silicon powder mass ratio of 1:5) and add it to the fluidized bed reactor. Purge with 250 mL / min argon gas to maintain particle fluidization. Heat to 950℃ at a rate of 5℃ / min and maintain the temperature for 60 min.

[0042] 3. Subsequently, the two gases were introduced simultaneously at a volume ratio of ethane:hydrogen = 1:3, with a total flow rate of 3 L / min, and the reaction was continued for 120 min to form a carbon cage layer of interwoven single-walled carbon nanotubes on the surface of the silicon particles.

[0043] 4. The above-deposited product was added to a 2% (w / w) dilute hydrochloric acid solution and stirred and acid-washed for 60 min under a 40°C water bath to remove residual ferrocene catalyst particles and reaction byproducts. After acid washing, it was repeatedly washed with deionized water until the pH of the washing solution was neutral, and then placed in a vacuum drying oven and dried at 70°C for 8 h to obtain a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material.

[0044] Comparative Example 1 Traditional solid carbon source coating methods include the following steps: Nano-silicon powder with an average particle size of 50 nm was mixed with asphalt at a mass ratio of 1:2 and directly pyrolyzed at 2350 °C for 2 h under argon protection by heating at 10 °C / min to obtain asphalt carbon-coated silicon material.

[0045] Comparative Example 2 The traditional liquid carbon source coating method includes the following steps: 50 nm average particle size nano-silicon powder was dispersed or dissolved in glucose at a mass ratio of 1:3 in an equal mass of deionized water. After spray drying, it was pyrolyzed at 2350 °C for 2 h under an argon atmosphere at a temperature of 10 °C / min to obtain glucose carbon-coated silicon material.

[0046] Comparative Example 3 (Catalyst Mixed Suspension Method) 1. Mix ferrocene and toluene at a mass ratio of 1:10 to dissolve them, and then mix them with nano-silicon powder with an average particle size of 50 nm at a mass ratio of 1:5 (ferrocene:silicon powder). Disperse the mixture by ultrasonication for 30 min to form a catalyst-silicon powder co-dispersed suspension.

[0047] 2. The above suspension was vacuum dried at 60°C for 12 h to obtain silicon powder preloaded with catalyst.

[0048] 3. Add the preloaded silicon powder into the fluidized bed reactor, introduce 200 mL / min of argon gas to maintain fluidization, heat to 950℃ at a rate of 8℃ / min, and hold at the constant temperature for 45 min.

[0049] 4. Subsequently, ethane and hydrogen were simultaneously introduced at a volume ratio of 1:2, with a total flow rate of 3 L / min, and the reaction was continued for 60 min to achieve vapor deposition on the surface of silicon particles. Finally, the acid washing and drying steps were the same as in Example 1.

[0050] Comparative Example 4 (Catalyst Material Blending Atomization Method) 1. Mix ferrocene and toluene at a mass ratio of 1:10 to dissolve them, and then mix them with nano-silicon powder with an average particle size of 50 nm at a mass ratio of 1:5 (ferrocene:silicon powder). Disperse the mixture by ultrasonication for 30 min to form a catalyst-silicon powder co-dispersed suspension.

[0051] 2. The above suspension is directly injected into the fluidized bed auxiliary pressurization gas path, and fine droplets are formed through the atomizing nozzle (the average droplet size is controlled to be 10 μm). Argon gas is introduced at a rate of 200 mL / min to maintain fluidization, and the temperature is heated to 950℃ at a rate of 8℃ / min and held at a constant temperature for 45 min.

[0052] 3. Subsequently, ethane and hydrogen were simultaneously introduced at a volume ratio of 1:2, with a total flow rate of 3 L / min, and the reaction was continued for 60 min to achieve vapor deposition on the surface of silicon particles. Finally, the acid washing and drying steps were the same as in Example 1.

[0053] Performance testing The materials obtained in the above examples and comparative examples were assembled into button half-cells (active material: conductive carbon black: binder = 8:1:1, electrolyte: 1 M LiPF6 / EC+DMC, voltage range 0.01~1.5 V), and constant current charge-discharge tests were performed on the LAND test system. The results are shown in Table 1: Table 1

[0054] As shown in Table 1, the materials in the examples significantly outperformed Comparative Examples 1 and 2 in terms of initial specific capacity, initial efficiency, and powder resistivity. Particularly noteworthy is that although Comparative Examples 3 and 4 used the same catalyst and carbon source as the examples of this invention, the different material introduction methods resulted in uneven dispersion of silicon particles, leading to significantly lower specific capacity and initial efficiency compared to the examples of this invention. The powder resistivity data (under 10 MPa pressure) indicates that the formation of carbon nanotubes effectively improves the conductivity of the material. This fully demonstrates the technical advantages brought about by the innovative catalyst introduction method of the atomization spraying method of this invention: the uniformly dispersed catalyst ensures the integrity and uniformity of the single-walled carbon nanotube network, thereby achieving superior electrochemical performance.

[0055] Figure 1 This is a comparison chart showing the 1C cycle performance of soft-pack full batteries prepared with negative electrode materials from composite material samples obtained in the embodiments and comparative examples of the present invention. Figure 1 Cyclic curves show that the capacity decay rate of the example sample is much lower than that of the comparative sample, confirming that the carbon cage structure constructed by the atomization spraying method of this invention has a better buffering effect on volume expansion. The material structure and morphology were analyzed using scanning electron microscopy and Raman spectroscopy (see...). Figures 2-9 ). Figures 2-4 Electron micrographs clearly show that the silicon particles in the sample of the example are densely covered with carbon nanotubes, which cross-link to form a uniform three-dimensional network structure. Figures 5-8 In the comparative samples, the smooth surface of the silicon particles shows exposed areas where no carbon nanotubes have grown, or carbon fibers that have grown in local clusters but have not formed a network. Figure 9The G peak (~1580 cm⁻¹) of the sample in Example 3 in Raman spectroscopy -1 The intensity was significantly higher than that of the D peak (~1350 cm⁻¹). -1 The G / D ratio > 2 indicates a high degree of graphitization and few defects in the carbon layer, further confirming the key influence of uniform catalyst dispersion on the quality of carbon nanotubes.

[0056] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they are not intended to limit the present invention. It should be noted that various changes and modifications can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the concept and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material, characterized in that, Includes the following steps: Step 1: Mix the catalyst precursor with the dispersion medium, then pass it into a fluidized bed and pressurize it to form micro-droplet spray; Step 2: Add nano-silicon powder into a fluidized bed reactor and maintain the fluidization of silicon particles under protective gas. Step 3: Heat the system to 850-950℃ and maintain the temperature. Introduce carbon source gas and auxiliary carrier gas to perform vapor phase coating deposition on the flowing silicon particles, inducing the in-situ growth of conductive carbon cages on the silicon surface. Finally, wash and dry to obtain a highly conductive silicon-carbon in-situ encapsulated carbon cage composite material.

2. The method for preparing the highly conductive silicon-carbon in-situ encapsulated carbon cage composite material according to claim 1, characterized in that, The catalyst precursor in step one is ferrocene, and the dispersion medium is toluene.

3. The method for preparing the highly conductive silicon-carbon in-situ encapsulated carbon cage composite material according to claim 1, characterized in that, In step one, the mass ratio of the catalyst precursor to toluene is 1:(10-20); the diameter of the micro-droplets after atomization is controlled at 5-20 μm.

4. The method for preparing the highly conductive silicon-carbon in-situ encapsulated carbon cage composite material according to claim 1, characterized in that, The nano-silicon powder in step two has a particle size of 30-100 nm, and the mass ratio of catalyst precursor to nano-silicon powder is 1:(4-6); the protective gas is argon, and the flow rate is 100-300 mL / min.

5. The method for preparing the highly conductive silicon-carbon in-situ encapsulated carbon cage composite material according to claim 1, characterized in that, In step three, the system heating rate is 5-10℃ / min, and the holding time is 30-60 min.

6. The method for preparing the highly conductive silicon-carbon in-situ encapsulated carbon cage composite material according to claim 1, characterized in that, The carbon source gas in step three is ethane, and the auxiliary carrier gas is hydrogen. The volume ratio of ethane to hydrogen is 1:(1-3). The duration of the gas phase coating deposition reaction is 30-120 min.

7. The method for preparing the highly conductive silicon-carbon in-situ encapsulated carbon cage composite material according to claim 1, characterized in that, In step three, the washing process involves first acid washing with dilute hydrochloric acid, followed by washing with deionized water until neutral. The concentration of the dilute hydrochloric acid is 0.5%-5%, the acid washing time is 30-120 min, and the temperature is 25-60℃. The drying process uses vacuum drying at a temperature of 60-80℃ for 6-12 h.

8. The highly conductive silicon-carbon in-situ encapsulated carbon cage composite material obtained by the preparation method according to any one of claims 1-7.

9. The application of the highly conductive silicon-carbon in-situ encapsulated carbon cage composite material according to claim 8 in the preparation of lithium-ion battery anode materials.

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