Porous carbon material based on waste c / c composite material, silicon-carbon composite material and preparation method and application thereof

Abstract

The application discloses a kind of porous carbon material based on waste C / C composite material, silicon-carbon composite material and its preparation method and application, belong to lithium ion battery negative material technical field.The porous carbon material uses waste C / C composite material as raw material, by " smash-activation pore-forming-polymer bridging-ice template forming-high temperature carbonization " process, a kind of hierarchical porous carbon skeleton with ion transmission path, internal electron conduction network and stable structure is prepared.The matrix is PyC and CCFs derived porous carbon, with hierarchical porous channel network, rich in micro, mesoporous, matrix is firmly combined by carbonaceous connecting point.At the same time, CCFs as reinforcing phase and conductive unit.The composite negative material prepared by loading silicon on the unique skeleton has good electrochemical performance.In addition, the entire technical path takes low-cost industrial solid waste as the core raw material, has remarkable economic benefit and environmental protection value.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode material technology, specifically relating to a porous carbon material based on waste C / C composite material, a silicon-carbon composite material, its preparation method and application. Background Technology

[0002] Developing carbon matrices that can effectively adapt to the massive volume changes of silicon during charging and discharging is key to driving the practical application of silicon-carbon anodes. An ideal carbon matrix needs to simultaneously meet three key requirements: high electronic conductivity, abundant buffer porosity, and sufficient mechanical strength. However, current material development in this field faces significant bottlenecks: traditional carbon sources (such as graphite), while possessing good conductivity, have a dense intrinsic structure and lack the porosity required to buffer volume expansion; while porous carbon derived from inexpensive precursors such as biomass, although providing abundant porosity, generally suffers from poor conductivity and a fragile carbon skeleton, making it difficult to construct an ideal structure that synergizes conductivity, porosity, and strength. Although introducing advanced materials such as carbon nanotubes and graphene or employing complex vapor deposition processes can improve performance, these strategies often come with high costs, limiting their large-scale application prospects. Meanwhile, as a special type of industrial solid waste, waste carbon / carbon (C / C) composites exhibit unique advantages. Even after pulverization, the particles are not homogeneous carbon powder at the microscopic level, but rather composite units firmly bonded together by chopped carbon fibers (CCFs) and pyrolytic carbon (PyC). This structure simultaneously possesses the high conductivity and high modulus potential of carbon fibers and the good modifiability of the pyrolytic carbon matrix, offering potential for constructing ideal carbon matrices. However, current technologies mostly utilize it at the level of simple processing such as direct carbonization, failing to fully understand and utilize its "two-phase composite" microstructure characteristics, and lacking effective processes for its directional reconstruction into high-performance electrode materials.

[0003] Therefore, how to develop a controllable conversion method to make deep use of the unique two-phase structure characteristics of such waste materials, obtain a novel carbon skeleton with high conductivity, ideal pore distribution and excellent structural stability through directional reconstruction, and use it to prepare high-performance, low-cost silicon-carbon anodes has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a porous carbon material, a silicon-carbon composite material, and their preparation methods and applications based on waste C / C composite materials. The invention uses waste C / C composite powder, microscopically composed of short-cut carbon fibers and a pyrolytic carbon matrix, as the starting material. Through a synergistic process of "pulverization-activation pore formation-polymer bridging-ice template molding-high-temperature carbonization," the microstructure of the raw material is reconstructed, thereby producing a novel porous carbon material with a channel network framework featuring short-range conductive interconnections, which is then used to load silicon.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a porous carbon material based on waste C / C composite material, wherein the porous carbon material is obtained by sequentially crushing, activating and creating pores, polymer bridging, ice template molding and high temperature carbonization of waste C / C composite material; The porous carbon material has a hierarchical porous channel network, which constitutes the framework of the porous carbon material and Li. + High-speed transmission main channel; The hierarchical porous channel network consists of a PyC-derived porous carbon matrix and a CCFs-derived porous carbon matrix formed by activation pore formation, polymer bridging, and ice template molding. The PyC-derived porous carbon matrix contains the original pore structure of PyC from waste C / C composite materials. In addition, the CCFs-derived porous carbon matrix serves as a reinforcing phase and conductive unit. The PyC-derived porous carbon matrix and the CCFs-derived porous carbon matrix are firmly bonded together by carbonaceous bonding points formed by high-temperature carbonization polymers.

[0006] This invention also provides a method for preparing porous carbon materials based on waste C / C composite materials, comprising the following steps: S1, the waste C / C composite material is crushed and finely ground sequentially to obtain composite powder; S2, the composite powder from S1 is mixed with an activator and subjected to high-temperature heat treatment, followed by acid washing, cleaning, and vacuum drying to obtain the activated composite powder; S3, the activated composite powder from S2 is dispersed in a polymer solution, ultrasonically stirred and mixed evenly to obtain a slurry, the slurry is injected into a mold, frozen and then freeze-dried to obtain a green body; S4, the preform from S3 is subjected to high-temperature carbonization in an inert atmosphere to convert the polymer in the preform into carbonaceous bonding points, thereby obtaining a porous carbon material based on waste C / C composite material.

[0007] Furthermore, in S1, the particle size of the composite powder is 0.01~20 μm.

[0008] Further, in S2, the activator includes one or more of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, zinc chloride, magnesium oxide, and silicon dioxide; The mass ratio of the composite powder to the activator is 1:(1~10). The acid washing is performed using a hydrochloric acid solution with a concentration of 1~3 mol / L; The high-temperature heat treatment is performed at a temperature of 600~1000℃ for a time of 2~10 h.

[0009] Further, in S3, the solid-liquid ratio of the activated composite powder to the polymer solution is 1 g: (5~50) mL.

[0010] Further, in S3, the polymer solution is one or more of polyvinyl alcohol (PVA) solution, polyvinylpyrrolidone (PVP) solution, polyethylene oxide (PEO) solution, and carboxymethyl cellulose solution; The polymer solution has a mass concentration of 0.2 wt% to 6 wt%; the solvent used in the polymer solution is ultrapure water at 20 to 100°C.

[0011] The ultrasonic time is 10-120 min, and the stirring time is 60-360 min.

[0012] Furthermore, in S4, the high-temperature carbonization treatment is carried out at a temperature of 600~950℃, the holding time is 2~8 h, and the heating rate is 2~5°C / min.

[0013] This invention also provides a method for preparing the above-mentioned porous carbon-silicon-carbon composite material based on waste C / C composite material, comprising the following steps: Porous carbon material based on waste C / C composite material was spread on a quartz boat and placed in a CVD furnace. Silane gas was introduced, and silicon deposition was performed in an argon / hydrogen mixed gas doped with silane gas. The silane gas was then turned off, and the temperature was raised again in an argon / hydrogen mixed gas. Acetylene gas was introduced for carbon coating. After natural cooling, the material was then ground and sieved to obtain a silicon-carbon composite material.

[0014] Furthermore, the process conditions for the silicon deposition process are as follows: The deposition temperature is 380~750℃, the volume concentration of silane gas in the argon / hydrogen mixture is 1%~15%, and the deposition time is 1.5~12 h; the volume ratio of argon to hydrogen in the argon / hydrogen mixture is (1~5):(99~95). The mass fraction of silicon in the silicon-carbon composite material is between 10% and 45%. The process conditions for the carbon coating treatment are as follows: The temperature is 580~780℃, the acetylene gas flow rate is 80~1500 sccm, and the treatment time is 10~400 min.

[0015] The present invention also provides the application of the porous carbon material based on the waste C / C composite material and / or the silicon-carbon composite material prepared by the preparation method described above in the preparation of lithium-ion battery anode materials.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a porous carbon material based on waste C / C composite materials. Through a structural reconstruction process targeting waste C / C composite powder, the reactivity and porosity of its two phases (PyC and CCFs) are simultaneously enhanced by chemical activation. Then, an ice-templating method is used to fix and arrange the polymer-bridged particles. Finally, a hierarchical porous carbon framework with ion transport pathways, an internal electronic conduction network, and a stable structure is successfully prepared through carbonization welding. The hierarchical porous channels in this framework ensure rapid electrolyte wetting and efficient lithium-ion transport, and provide an ordered buffer space for silicon volume expansion. Simultaneously, the dispersed CCFs and polymer-derived carbon solder joints together construct an effective electronic conduction pathway within the framework, significantly improving the overall conductivity of the material. Furthermore, based on the unique framework constructed, through silicon loading and carbon coating processes, the high specific capacity, excellent rate performance, and cycle life of the anode material prepared by this invention are synergistically improved. Moreover, this technology uses low-cost industrial solid waste as raw material, achieving excellent electrochemical performance while also obtaining significant economic and environmental benefits. Attached Figure Description

[0017] Figure 1 This is a process preparation flow chart of an embodiment of the present invention; Figure 2 This is a SEM image of PC-1 in Embodiment 1 of the present invention; Figure 3 This is a SEM image of SiC-1 in Embodiment 1 of the present invention; Figure 4 The graphs show the charge-discharge curves of the silicon-carbon composite materials prepared in Examples 1 and 2 of this invention. Detailed Implementation

[0018] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0020] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0021] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0022] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0023] This invention provides a porous carbon material and a silicon-carbon composite material based on waste C / C composite material, as well as their preparation methods and applications. Specifically, it relates to a high-performance porous silicon-carbon composite material prepared from waste C / C composite material through a synergistic chemical and physical reconstruction process, and its preparation method and application in lithium-ion batteries.

[0024] In the first aspect, this embodiment provides a porous carbon material based on waste C / C composite material, wherein the porous carbon material is obtained by processing waste C / C composite material through a process of "crushing-activation pore-forming-polymer bridging-ice template molding-high temperature carbonization"; The matrix of the material is activated pore-forming PyC and CCFs-derived porous carbon, in which the dispersed CCFs serve as reinforcing phases and conductive units. The ice-templating method imparts a hierarchical porous channel network to the material, which constitutes the material's framework and Li. + A rapid ion transport main channel. Simultaneously, the matrix constituting the channel walls is rich in numerous micropores and mesopores generated by chemical activation, providing a high specific surface area and active sites. PyC and CCF-derived porous carbons, after polymer bridging and high-temperature carbonization, form carbonaceous bonding points that are firmly linked together. This not only endows the material with overall structural strength but also reconstructs an effective electron conduction network within the hierarchical porous channel framework.

[0025] Secondly, this embodiment provides a method for preparing a porous carbon material based on waste C / C composite material, using waste C / C composite material as a carbon source, including the following steps: S1, the waste C / C composite material is crushed and finely ground to obtain composite powder with a particle size of 0.01~20 μm. The composite powder is rich in CCF fragments derived from the raw materials.

[0026] S2 involves mixing the composite powder with an activator and then activating it, followed by acid washing, cleaning, and vacuum drying to obtain the activated composite powder. This step aims to simultaneously improve the reactivity and porosity of the CCFs and PyC phases.

[0027] In step S3, the activated composite powder is dispersed in a polymer solution and ultrasonically stirred to obtain a slurry. The slurry is then injected into a mold, frozen, and freeze-dried to obtain a green body with a hierarchical porous structure. In this step, the polymer acts as a binder or physical forming agent, playing a crucial role in bridging the particles and imparting initial strength to the green body. The primary function of the ice template is to solve the powder forming problem and prepare a monolithic green body suitable for subsequent processing. Furthermore, through ice crystal growth and sublimation, interconnected macroscopic channels or layered gaps are formed within the bulk material, primarily creating pathways for material penetration and transport in the subsequent "silicon deposition" process. This, in conjunction with chemical activation, then assists in constructing a richer hierarchical porous structure.

[0028] S4, the preform is subjected to high-temperature carbonization in an inert atmosphere to obtain a porous carbon material based on waste C / C composite material. In this step, the polymer is pyrolyzed into strong carbonaceous bonding points, which firmly bridge the powder particles together, thereby obtaining a porous carbon material with a stable structure and a certain conductive framework. This carbonization step not only achieves preform shaping and strengthening but also essentially preserves the hierarchical porous structure created by the ice template and activation steps.

[0029] Thirdly, the present invention provides a silicon-carbon composite material, which uses the above-mentioned porous carbon material as a skeleton, deposits silicon using conventional chemical vapor deposition (CVD), and then obtains a powder material after carbon coating and subsequent pulverization.

[0030] The specific steps are as follows: Porous carbon material based on waste C / C composite material is spread on a quartz boat, placed in a CVD furnace, and silane gas is introduced. Silicon deposition is performed in an argon / hydrogen mixed gas doped with silane gas. The silane gas is then turned off, and the temperature is raised again under an argon / hydrogen mixed gas. Acetylene gas is introduced for carbon coating. After natural cooling, the material is then ground and sieved to obtain silicon-carbon composite material.

[0031] The CVD silicon deposition process conditions are as follows: deposition temperature 380~750℃, silane (SiH4) volume concentration in argon / hydrogen mixture 1%~15%, deposition time adjusted within 1.5~12 h according to the target silicon loading, and argon to hydrogen volume ratio in argon / hydrogen mixture (1~5):(99~95).

[0032] By adjusting the deposition time, the mass fraction of silicon in the composite material can be controlled between 10% and 45%, thereby obtaining silicon-carbon composite materials with an initial discharge specific capacity in the range of 800 to 2200 mAh / g.

[0033] The carbon coating process conditions are: temperature of 580~780℃, acetylene gas flow rate of 80~1500 sccm, and processing time of 10~400 min.

[0034] Fourthly, this embodiment provides an application of porous carbon material based on waste C / C composite material and / or silicon-carbon composite material prepared by the aforementioned preparation method in the preparation of lithium-ion battery anode materials.

[0035] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0036] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0037] Example 1 This embodiment provides a method for preparing porous carbon materials based on waste C / C composite materials, including the following steps: S1: Waste C / C composite material is crushed, ball-milled, and passed through a 300-mesh standard sieve to obtain composite powder.

[0038] S2: 2 g of composite powder was mixed with 6 g of KOH and activated in an Ar atmosphere at 800 °C at a rate of 5 °C / min for 3 h. After washing with 1 M HCl until neutral, the mixture was washed with water and dried at 60 °C for 12 h to obtain the activated composite powder.

[0039] S3: The composite powder activated by S2 was dispersed in 20 mL of 2wt% PVA aqueous solution, sonicated for 30 min, and stirred for 120 min to form a uniform slurry. The slurry was injected into a polytetrafluoroethylene mold, frozen at -50-60℃ overnight, and then freeze-dried for 48 h to obtain a block precursor.

[0040] S4: The precursor is placed in a tube furnace and carbonized at 800℃ for 2 h under an Ar atmosphere by heating at 2℃ / min to obtain a porous carbon material, denoted as PC-1.

[0041] This embodiment also provides a method for preparing a silicon-carbon composite material, including the following steps: S5: Take 1g of PC-1 material and spread it evenly on a quartz boat, then place it in a CVD furnace. First, purge the furnace air with an argon / hydrogen mixed gas (argon to hydrogen volume ratio of 5:95) for 30 min, then raise the temperature to 440℃ and deposit for 5 h in an argon / hydrogen mixed gas atmosphere containing 2% SiH4 by volume. After deposition, cool in argon gas.

[0042] S6: Under an argon / hydrogen mixed atmosphere, the temperature was raised to 680℃, acetylene gas was introduced, and carbon coating was performed for 80 minutes at a flow rate of 200 sccm. After natural cooling, the resulting material was ground and passed through a 300-mesh sieve to obtain a powdered silicon-carbon composite material, denoted as SiC-1.

[0043] The experimental process flow in this embodiment is as follows: Figure 1 As shown, silicon-carbon anode materials are obtained through a process of crushing, activation and pore formation, polymer bridging, ice template forming, high-temperature carbonization, and CVD deposition.

[0044] SEM images of the PC-1 obtained through preparation are shown below. Figure 2 As shown, there are many porous structures, which provide channels for subsequent silicon deposition, mitigating volume expansion, and lithium-ion transport.

[0045] SEM images of the prepared SiC-1 are shown below. Figure 3 As shown, some pores may still exist on the particles, and the surface is relatively smooth. The charge-discharge curves obtained after half-cell testing are shown below. Figure 4 As shown, SiC-1 has a discharge specific capacity of 1882.01 mAh / g, an initial coulombic efficiency of 92.13%, and a capacity retention of 90.13% after 100 cycles at 0.1 C.

[0046] Example 2 The steps are exactly the same as in Example 1, except that the temperature of the chemical activation in step 2 is adjusted from 800°C to 900°C. The resulting porous carbon framework is denoted as PC-2, and the final silicon-carbon composite material is denoted as SiC-2.

[0047] The charge-discharge curves obtained after half-cell testing are as follows: Figure 4 As shown, SiC-1 has a discharge specific capacity of 1974.72 mAh / g, an initial efficiency of 92.26%, and a capacity retention of 88.25% after 100 cycles at 0.1 C.

[0048] Example 3 The steps were exactly the same as in Example 1, except that the CVD deposition time for step 5 was adjusted from 5 h to 3.5 h. The resulting silicon-carbon composite material was designated SiC-3.

[0049] Example 4 The steps were exactly the same as in Example 1, except that the CVD deposition time for step 5 was adjusted from 5 h to 7 h. The resulting silicon-carbon composite material was designated SiC-4.

[0050] Example 5 The steps are exactly the same as in Example 1, except that the concentration of the PVA solution in step 3 is adjusted from 2 wt% to 4 wt%. The resulting porous carbon skeleton is designated as PC-5, and the final silicon-carbon composite material is designated as SiC-5.

[0051] Comparative Example 1 Steps 1 and 2 of Example 1 were performed to obtain activated composite powder. Step 3 (PVA mixing and freeze-drying) was omitted. The activated composite powder was directly loaded into a stainless steel mold and pressed into shape under a pressure of 20 MPa. The pressed blank was subjected to the same carbonization treatment as in step 4 of Example 1 to obtain a carbon block, denoted as PC-C1.

[0052] PC-C1 was subjected to the same silicon deposition, carbon coating, and pulverization processes as in steps 5 and 6 of Example 1 to obtain a silicon-carbon composite material, denoted as SiC-C1.

[0053] test Using the powdered silicon-carbon composite materials prepared in the aforementioned embodiments and comparative examples as active materials, negative electrodes were prepared and CR2032 coin cell half-cells were assembled for testing according to the following general method. The active material, conductive agent (Super P), and polyacrylic acid (PAA) binder were mixed at a mass ratio of 8:1:1 and placed in a slurry box, then homogenized in a homogenizer to form a uniform slurry. The slurry was uniformly coated onto a copper foil current collector and dried in a vacuum drying oven at 60°C. The electrode was then cut into 14 mm diameter discs and assembled into a glove box filled with argon gas. The prepared negative electrode was used as the working electrode, lithium foil as the counter electrode, polyethylene as the separator, and 1 M LiPF6 EC / DEC / EMC as the electrolyte. After assembly, the cells were allowed to stand for 12 hours. The assembled coin cell half-cells were tested using a LAND battery testing system. The voltage window was 0.01-1.5 V (vs. Li + / Li), and constant cell tests were performed at a current density of 0.1 C.

[0054] Table 1 Key electrochemical performance data of each anode material

[0055] As shown in Table 1, the SiC-1 prepared using the complete process of this invention achieves the best balance in terms of capacity, first-efficiency, and cycle stability. Its high capacity is attributed to the optimized silicon loading, its high first-efficiency stems from the suppression of side reactions by the carbon coating layer and the stable framework, and its excellent cycle performance directly demonstrates the synergistic effect of the robust conductive network constructed by PVA-derived carbon junctions and the effective expansion buffer space provided by the mesopores of the ice template.

[0056] Examples 2-5 show that process parameters are adjustable, but deviations from optimal conditions can affect performance balance. Specifically, the SiC-3 sample had a low silicon loading and low capacity but optimal cycling performance, while the SiC-4 sample had excessively high silicon loading, leading to pore blockage, increased stress, and decreased cycling performance.

[0057] The performance of the comparative SiC-C1 was completely degraded, indicating that the bridging... The carbonization process is not optional; it is essential for maintaining the mechanical integrity of the framework and forming usable conductive pathways (electron / ion pathways). It also demonstrates that the ice-templating method is crucial for creating interconnected ion channels and achieving a high specific surface area hierarchical porous structure; without it, ion transport is hindered and silicon loading is difficult. Neither of these two steps can yield the high-performance porous carbon framework prepared in this invention. However, in contrast, SiC... Regarding performance, further increasing the PVA concentration to 4 wt% actually led to a performance decrease, indicating that there is a critical window for its effect. PVA is mainly used to provide a small amount of residual carbon for spot welding at particle contact points. Excessive amounts will block the pore throat, weaken accessible pore volume and transport channels, and introduce more oxygen-containing residual carbon interfaces, thus making Si deposition more surface-oriented and increasing interfacial side reactions. In summary, appropriate amounts of polymer bridging... Carbonization is key to building a robust electrode structure and ensuring effective electron conduction, but it must be controlled to near the minimum necessary amount.

[0058] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A porous carbon material based on waste C / C composite material, characterized in that, The porous carbon material is obtained by sequentially crushing, activating and creating pores from waste C / C composite material, polymer bridging, ice template molding, and high-temperature carbonization treatment. The porous carbon material has a hierarchical porous channel network, which constitutes the framework of the porous carbon material and Li. + High-speed transmission main channel; The hierarchical porous channel network consists of a PyC-derived porous carbon matrix and a CCFs-derived porous carbon matrix formed by activation pore formation, polymer bridging, and ice template molding. The PyC-derived porous carbon matrix contains the original pore structure of PyC from waste C / C composite materials. In addition, the CCFs-derived porous carbon matrix serves as a reinforcing phase and conductive unit. The PyC-derived porous carbon matrix and the CCFs-derived porous carbon matrix are firmly bonded together by carbonaceous bonding points formed by high-temperature carbonization polymers.

2. The method for preparing porous carbon material based on waste C / C composite material as described in claim 1, characterized in that, Includes the following steps: S1, the waste C / C composite material is crushed and finely ground sequentially to obtain composite powder; S2, the composite powder from S1 is mixed with an activator and subjected to high-temperature heat treatment, followed by acid washing, cleaning, and vacuum drying to obtain the activated composite powder; S3, the activated composite powder from S2 is dispersed in a polymer solution, ultrasonically stirred and mixed evenly to obtain a slurry, the slurry is injected into a mold, frozen and then freeze-dried to obtain a green body; S4, the preform from S3 is subjected to high-temperature carbonization in an inert atmosphere to convert the polymer in the preform into carbonaceous bonding points, thereby obtaining a porous carbon material based on waste C / C composite material.

3. A method for preparing porous carbon material based on waste C / C composite material according to claim 2, characterized in that, In S1, the particle size of the composite powder is 0.01~20 μm.

4. The method for preparing porous carbon materials based on waste C / C composite materials according to claim 2, characterized in that, In S2, the activator includes one or more of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, zinc chloride, magnesium oxide, and silicon dioxide. The mass ratio of the composite powder to the activator is 1:(1~10). The high-temperature heat treatment is performed at a temperature of 600~1000℃ for a time of 2~10 h.

5. A method for preparing porous carbon material based on waste C / C composite material according to claim 2, characterized in that, In S3, the solid-liquid ratio of the activated composite powder to the polymer solution is 1 g: (5~50) mL.

6. The method for preparing porous carbon material based on waste C / C composite material according to claim 2, characterized in that, In S3, the polymer solution is one or more of polyvinyl alcohol solution, polyvinylpyrrolidone solution, polyethylene oxide solution and carboxymethyl cellulose solution; The polymer solution has a mass concentration of 0.2 wt% to 6 wt%.

7. A method for preparing porous carbon material based on waste C / C composite material according to claim 2, characterized in that, In S4, the high-temperature carbonization treatment is carried out at a temperature of 600~950℃, the holding time is 2~8 h, and the heating rate is 2~5°C / min.

8. A method for preparing a silicon-carbon composite material, characterized in that, The process includes the following steps: using a porous carbon material based on waste C / C composite material as described in claim 1; Porous carbon material based on waste C / C composite material is laid flat on a quartz boat, placed in a CVD furnace, and silane gas is introduced. Silicon deposition is performed in an argon / hydrogen mixed gas doped with silane gas. The silane gas is then turned off, and the temperature is raised under an argon / hydrogen mixed gas. Acetylene gas is then introduced to perform carbon coating treatment. After natural cooling, the mixture is then ground and sieved to obtain a silicon-carbon composite material.

9. The method for preparing a silicon-carbon composite material according to claim 8, characterized in that, The process conditions for the silicon deposition process are as follows: The deposition temperature is 380~750℃, the volume concentration of silane gas in the argon / hydrogen mixture is 1%~15%, and the deposition time is 1.5~12 h; the volume ratio of argon to hydrogen in the argon / hydrogen mixture is (1~5):(99~95). The mass fraction of silicon in the silicon-carbon composite material is between 10% and 45%. The process conditions for the carbon coating treatment are as follows: The temperature is 580~780℃, the acetylene gas flow rate is 80~1500 sccm, and the treatment time is 10~400 min.

10. The application of a porous carbon material based on waste C / C composite material as described in claim 1 and / or a silicon-carbon composite material prepared by the preparation method as described in any one of claims 8 to 9 in the preparation of lithium-ion battery anode materials.

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