High-capacity silicon-carbon negative electrode material and preparation process thereof

Abstract

The invention relates to the field of lithium battery negative electrode materials, and particularly discloses a high-capacity silicon-carbon negative electrode material and a preparation process thereof. The preparation process comprises the following steps: preparing biomass activated carbon with the total pore volume of 1.0-1.3 cm < 3 > / g and the compressive strength of 20-40 Mpa; depositing silicon nanoparticles in pores and on the surface of the porous carbon matrix by adopting a fluidized bed chemical vapor deposition process to obtain a silicon-carbon core material; depositing a thin carbon layer on the surface of the silicon-carbon core material by taking acetylene as a carbon source; and carrying out secondary carbon coating by adopting a rotary furnace to form the silicon-carbon negative electrode material. According to the silicon-carbon negative electrode material prepared by the process, the mechanical stability and the cycling stability of the material are improved; meanwhile, the large-pore-volume porous activated carbon provides sufficient deposition space for the silicon nanoparticles, the reversible capacity is effectively improved, and volume expansion of silicon in the circulation process can be remarkably inhibited.

Description

Technical Field

[0001] The present application relates to the field of lithium battery negative electrode materials, and more specifically, to a high-capacity silicon-carbon negative electrode material and a preparation process thereof. Background Art

[0002] As an important part of modern energy storage technology, lithium-ion batteries have developed rapidly in recent years. Especially in the fields of new energy vehicles and portable electronic devices, their high energy density and long cycle life make them the mainstream choice. As a key component of lithium-ion batteries, negative electrode materials directly affect the overall performance of the battery. At present, silicon-based negative electrode materials have attracted much attention because their theoretical specific capacity is much higher than that of traditional graphite materials, and have become one of the research hotspots. However, in practical applications, silicon-based negative electrode materials still face many challenges, especially the cracking problem caused by volume expansion during the cycle and the need to increase the reversible capacity. These problems have put forward higher requirements for the research and development of silicon-based negative electrode materials.

[0003] In order to solve the volume expansion problem of silicon-based negative electrode materials during the cycle, the currently commonly used technical means include: reducing the impact of volume change by nano-sizing silicon particles; combining silicon and carbon materials in the form of composite materials to improve overall stability; and surface coating of silicon materials to enhance the mechanical properties of the materials. In addition, there are also means to improve the interface characteristics and conductive properties of the materials by optimizing the preparation process, such as chemical vapor deposition or sol-gel method.

[0004] However, although these methods have alleviated the volume expansion problem of silicon-based negative electrode materials to a certain extent, the reversible capacity of silicon-based negative electrode materials still needs to be improved. Summary of the invention

[0005] In order to solve the above technical problems, the present application provides a high-capacity silicon-carbon negative electrode material and a preparation process thereof.

[0006] This application adopts the following technical solutions: In a first aspect, the present application provides a process for preparing a high-capacity silicon-carbon negative electrode material, which comprises: (1) Preparation of total pore volume of 1.0-1.3cm 3 / g, biomass activated carbon with a compressive strength of 20-40 Mpa; (2) placing the biomass activated carbon into a fluidized bed, using a fluidized bed chemical vapor deposition process, using silane as a silicon source, depositing silicon nanoparticles in the pores and on the surface of the biomass activated carbon to obtain a silicon-carbon core material; and then using acetylene as a carbon source to deposit a thin carbon layer on the surface of the silicon-carbon core material; (3) The silicon-carbon core material with a thin carbon layer is guided out of the fluidized bed, and acetylene is used as the carbon source, and a rotary kiln is used for secondary carbon coating to form a silicon-carbon negative electrode material.

[0007] By adopting the above technical solution, the high-capacity silicon-carbon negative electrode material prepared has significantly improved reversible capacity and cycle stability. The specific effects are as follows: By preparing biomass activated carbon with a total pore volume of 1.0-1.3cm³ / g and a compressive strength greater than 20Mpa, the problem of high pore volume and mechanical strength being difficult to balance is effectively solved, thereby improving the overall stability and capacity of the material. Silicon nanoparticles are deposited in the pores and on the surface of the porous carbon matrix using a fluidized bed chemical vapor deposition process, which can effectively inhibit the volume expansion of silicon during the charge and discharge cycle, reduce the generation of cracks, and significantly improve the cycle stability of the material. A thin carbon layer is deposited on the surface of the silicon-carbon core material and then a secondary carbon coating is performed, which further enhances the conductivity and structural stability of the material, while reducing the direct contact between silicon and the electrolyte, thereby improving the cycle life and overall performance of the material.

[0008] Furthermore, in a preferred embodiment, the specific surface area of ​​the biomass activated carbon is ≥ 2150m 2 / g, the micropore volume accounts for more than 62%, and the mesopore volume accounts for less than 38%.

[0009] Preferably, in a preferred embodiment, the specific surface area of ​​the biomass activated carbon is ≥ 2350m 2 / g, the micropore volume accounts for more than 80%, and the mesopore volume accounts for less than 20%.

[0010] By adopting the above technical solutions, the multi-level pore structure design effectively improves the silicon loading capacity of the material, while ensuring the rapid transmission of lithium ions, thereby significantly improving the reversible capacity of the silicon-carbon negative electrode material. In addition, the optimized pore structure enhances the mechanical stability of the material, which helps to alleviate the volume expansion problem of silicon during the cycle.

[0011] Furthermore, in a preferred embodiment, the method for preparing the biomass activated carbon comprises: Select hard-shelled plant raw materials and pre-treat them to obtain biomass raw materials; The biomass raw material is heat-treated in a carbonization furnace for 1.5-2.5 hours to obtain a carbonized material; The carbonized material is mixed with an inorganic base at an alkali-carbon ratio of 1.5-2.5:1, the mixed material is put into an activation furnace, and activated at 800-850° C. for 0.8-2 h to obtain an activated material; The activated material is crushed, acid-washed, filtered and air-flow-pulverized to obtain biomass activated carbon.

[0012] By adopting the above technical solution, biomass activated carbon that can take into account both mechanical strength and high pore volume characteristics is prepared. Specifically as follows: Select hard-shelled plant raw materials and perform pretreatment. Since its fiber content is high, it helps to obtain activated carbon materials with high pore volume; heat-treat the biomass raw materials in a carbonization furnace to obtain carbonized materials. This process helps to form a stable carbon skeleton structure and improve the mechanical strength of the materials; mix the carbonized materials with inorganic alkali and then put them into an activation furnace for activation. By controlling the alkali-carbon ratio and activation temperature, porous carbon with high pore volume and appropriate pore size distribution is obtained; post-treatment steps are used to further optimize the pore structure and surface characteristics of the porous carbon.

[0013] Further, in a preferred embodiment, before putting the mixed materials into the activation furnace for activation, it further includes: Heat-treat the mixed materials at 450 - 550 °C for 1.5 - 2.5 h for curing; then heat-treat at 800 - 850 °C for 0.8 - 1.2 h for activation.

[0014] By adopting the above technical solution, first, heat-treating the mixed materials at 450 - 550 °C for curing can effectively enhance the mechanical strength of the biomass activated carbon, avoid the collapse of the structure during the subsequent activation process, and thus ensure the high pore volume characteristics of the materials. Subsequently, short-time activation at 800 - 850 °C can further increase the porosity and specific surface area of the materials without damaging the cured structure, provide sufficient space for the deposition of silicon, and thus effectively improve the reversible capacity of the anode material and inhibit the adverse effects brought by volume expansion.

[0015] Further, in a preferred embodiment, after mixing the carbonized materials with inorganic alkali to obtain mixed materials, it further includes: adding 8 - 15 vol% of ethanol solution as a dispersant to the mixed materials.

[0016] By adopting the above technical solution, the measure of adding a dispersant makes the mixing of the inorganic alkali and the carbonized materials more sufficient, thus forming a more uniform pore structure during the subsequent activation process.

[0017] Further, in a preferred embodiment, when preparing the carbonized materials, the heat-treatment process is a programmed temperature rise process, including: The carbonization furnace is heated to 200 °C at a rate of 4 - 6 °C / min and held for 20 - 40 min; then heated to 400 °C at a rate of 4 - 6 °C / min and held for 20 - 40 min; finally, heated to 600 - 650 °C at a rate of 4 - 6 °C / min and held for 2 h.

[0018] By adopting the above technical solution, the programmed temperature rising process can effectively control the pyrolysis reaction of the biomass raw material, ensuring the structural stability and pore uniformity of the carbonized material. Specifically, the staged heating and heat preservation treatments help to gradually remove the volatile components in the biomass raw material, while avoiding excessive decomposition or coking of the raw material at high temperatures, thereby obtaining biomass activated carbon with high pore volume and excellent mechanical strength.

[0019] Further, in a preferred embodiment, in step (2), the flow rate ratio of the silane to the carrier gas is 1:7 - 8, the temperature is 440 - 460 °C, and the treatment time is 7 - 8 h; the flow rate ratio of the acetylene to the carrier gas is 1:6 - 7, the coating temperature is 580 - 600 °C, and the coating time is 5 - 6 h.

[0020] By adopting the above technical solution, by controlling the flow rate ratio, temperature, and treatment time of the silane to the carrier gas, the deposition amount and distribution uniformity of the silicon nanoparticles can be precisely adjusted, so that the silicon content is stably within the range of 40 - 50 wt%, avoiding particle agglomeration and cracking phenomena, and ensuring the structural stability and electrochemical performance of the material. At the same time, a thin carbon layer (specific surface area of 30 - 50 m 2 / g) can be very conveniently formed on the surface of the silicon-carbon core material obtained in step (2) by using a fluidized bed, thereby isolating the oxidation of the active sites on the silicon surface.

[0021] Further, in a preferred embodiment, in step (3), the flow rate ratio of the acetylene to the carrier gas is 1:2 - 3, the coating temperature is 560 - 580 °C, and the coating time is 4 - 6 h.

[0022] By adopting the above technical solution, by controlling the flow rate ratio, temperature, and treatment time of the acetylene to the carrier gas, a dense and uniform carbon layer (specific surface area ≤ 5 m 2 / g) is coated on the surface of the thin carbon layer by using a rotary furnace chemical vapor deposition technique, finally forming a gradient double-layer carbon protection layer with a dense outer layer and a loose inner layer, further suppressing the volume effect and reducing the interfacial side reactions.

[0023] In a second aspect, the present application provides a high-capacity silicon-carbon negative electrode material prepared by the above preparation process, and the reversible capacity of the silicon-carbon negative electrode material is ≥ 2000 mAh / g.

[0024] In summary, the present application has the following beneficial effects: 1. By using biomass activated carbon with a total pore volume of 1.0 - 1.3 cm³ / g and a compressive strength greater than 20 Mpa as the matrix, the mechanical stability and cycle stability of the material are improved; at the same time, the porous activated carbon with a large pore volume provides sufficient deposition space for the silicon nanoparticles, the reversible capacity of the material is effectively improved, and the volume expansion of silicon during cycling can be significantly inhibited.

[0025] 2. By using the fluidized bed chemical vapor deposition process to deposit silicon nanoparticles in the pores and on the surface of the porous carbon matrix, and forming a protective layer through two carbon coating processes, the problem of easy cracking of single-layer carbon coating can be effectively alleviated. The inner thin carbon layer can prevent the silicon-carbon material in the core from being oxidized during the fluidized bed transfer process, and the outer carbon coating enhances the effect of isolating the electrolyte, further enhancing the conductivity and structural stability of the material. At the same time, the direct contact between silicon and the electrolyte is reduced, improving the cycle life and overall performance of the material.

[0026] 3. In the preferred embodiment, by optimizing the preparation process of biomass activated carbon, on the premise that the mechanical strength of the activated carbon can meet the requirements of the fluidized bed process and the overall mechanical stability of the material, through the design of a hierarchical pore structure, the proportion of micropore pore volume is increased to more than 60%, further enhancing the loading capacity of silicon nanoparticles, effectively suppressing the negative impact of volume expansion, and improving the reversible capacity of the material. Specific Embodiments

[0027] The following will describe the implementation embodiments of the present invention in detail in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. The specific conditions not specified in the examples are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not specified in the production manufacturer are all conventional products that can be obtained through commercial purchase.

[0028] The following will detail the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention. For the convenience of recording, the following rules are adopted to name the prepared samples:

[0029] D2-I 1 / 1 II 1 / 1 -(t-n)-T-m Wherein: D2 indicates that the raw material is coconut shell; I indicates that the activator is KOH, II indicates that the activator is NaOH, and the subscript indicates the alkali-carbon ratio; t indicates the curing temperature, n indicates the curing time; T indicates the activation temperature, and m indicates the activation time.

[0030] Preparation Example 1 This preparation example provides a method for preparing biomass activated carbon, including: Using coconut shell as the raw material, after pickling and washing to neutral, drying and then heat-treating at 300 °C for 1 h for pre-oxidation, and then air-flow pulverizing to D50 = 150 μm to obtain the biomass raw material; The biomass raw material is put into a rotary kiln for heat treatment. The rotary kiln is heated to 200 °C at a rate of 5 °C / min and held for 30 min; then it is heated to 400 °C at a rate of 5 °C / min and held for 30 min; finally, it is heated to 650 °C at a rate of 5 °C / min and held for 2 h. The whole process is protected by nitrogen (flow rate is 40 L / min), and the rotation speed is 25 Hz to obtain carbonized material.

[0031] The carbonized material is mixed with inorganic base KOH, and the alkali-carbon ratio is 2:1. During the mixing process, the inorganic base is added to the carbonized material in three batches, and each batch is mixed for 20 min to obtain a mixed material.

[0032] The mixed material is put into a tubular activation furnace and heat-treated at 800 °C for 60 min to obtain activated material; After the activated material is crushed, it is soaked in acid solution (0.5 M HCl) overnight, washed until neutral, dried, and airflow pulverized to D50 = 15 μm to obtain biomass activated carbon, denoted as D2-I 2 / 1 -800-60.

[0033] Preparation Example 2 The difference between this preparation example and Preparation Example 1 is that: the inorganic base is KOH and NaOH, and the alkali-carbon ratio is KOH:NaOH:carbonized material = 1:1.5:1; the activation temperature is 850, and the treatment time is 60 min. The obtained activated carbon is denoted as D2-I 1 / 1 Ⅱ 1.5 / 1 -850-60.

[0034] Preparation Example 3 The difference between this preparation example and Preparation Example 1 in the mixing step (1) is that: the inorganic base is KOH and NaOH, and the alkali-carbon ratio is KOH:NaOH:carbonized material = 1:1.5:1. The activation temperature is 800, and the treatment time is 60 min. The obtained activated carbon is denoted as D2-I 1 / 1 Ⅱ 1.5 / 1 -800-60.

[0035] Preparation Example 4 The difference between this preparation example and Preparation Example 1 is that: the inorganic base is KOH, and the alkali-carbon ratio is KOH:carbonized material = 2.5:1. The activation step is: the mixed material is put into a tubular activation furnace and heat-treated at 500 °C for 2 h for curing; then it is heat-treated at 800 °C for 50 min for activation. The obtained activated carbon is denoted as D2-I 2.5 / 1 -500-120-800-50.

[0036] Preparation Example 5 The difference between this preparation example and Preparation Example 1 is as follows: the inorganic base is KOH, and the alkali-to-carbon ratio is KOH: carbonized material = 2.5:1. Meanwhile, 10 vol% of ethanol solution is added as a dispersant (the mass ratio of the dispersant to the carbonized material is 0.05:1). The activation steps are as follows: the mixed material is put into a tubular activation furnace, heat-treated at 500 °C for 2 h for curing; then heat-treated at 800 °C for 50 min for activation. The obtained activated carbon is denoted as D2-I 2.5 / 1、0.05 / 1 -500-120-800-50。

[0037] Preparation Example 6 The difference between this preparation example and Preparation Example 1 is as follows: the inorganic base is KOH, and the alkali-to-carbon ratio is KOH: carbonized material = 2.5:1. The activation steps are as follows: the mixed material is put into a tubular activation furnace, heat-treated at 500 °C for 2 h for curing; then heat-treated at 800 °C for 50 min for activation. The obtained activated carbon is denoted as D2-I 2.5 / 1 -500-120-800-50。

[0038] Comparative Preparation Example 1 The difference between this preparation example and Preparation Example 1 is as follows: the inorganic base is KOH, and the alkali-to-carbon ratio is KOH: carbonized material = 1.5:1. The activation step is: the activation temperature is 850, and the treatment time is 90 min. The obtained activated carbon is denoted as D2-I 1.5 / 1 -850-90。

[0039] Comparative Preparation Example 2 The difference between this preparation example and Preparation Example 1 is as follows: the inorganic bases are KOH and NaOH, and the alkali-to-carbon ratio is KOH: NaOH: carbonized material = 1:1:1.5. The activation step is: the activation temperature is 800, and the treatment time is 60 min. The obtained activated carbon is denoted as D2-I 1 / 1.5 Ⅱ 1 / 1.5 -800-60。

[0040] Comparative Preparation Example 3 The difference between this preparation example and Preparation Example 1 is as follows: the inorganic bases are KOH and NaOH, and the alkali-to-carbon ratio is KOH: NaOH: carbonized material = 1:1.5:1. The activation step is: the activation temperature is 750, and the treatment time is 90 min. The obtained activated carbon is denoted as D2-I 1 / 1 Ⅱ 1.5 / 1 -750-90。

[0041] Comparative Preparation Example 4 The difference between this preparation example and Preparation Example 1 is as follows: the inorganic base is KOH, and the alkali-to-carbon ratio is KOH: carbonized material = 1.5:1. The activation steps are as follows: the mixed material is put into a tubular activation furnace, heat-treated at 500 °C for 60 min for curing; then heat-treated at 850 °C for 50 min for activation. The obtained activated carbon is denoted as D2-I1.5 / 1 -500-60-850-50。

[0042] Comparative Preparation Example 5 The difference between this preparation example and Preparation Example 1 is that the inorganic base is KOH, and the alkali-carbon ratio is KOH: carbonized material = 1.8:1. The activation step is as follows: put the mixture into a tube-type activation furnace, heat-treat at 750 °C for 40 min; then heat-treat at 850 °C for 50 min for activation. The obtained activated carbon is denoted as D2-I 1.8 / 1 -750-40-850-50。

[0043] Perform performance index tests on the activated carbon samples provided in the above preparation examples, and use commercially available activated carbon as a comparison. The specific test methods are as follows: Specific surface area: Physical adsorption and desorption test (BET) Pore volume: Physical adsorption and desorption test (BET) Average pore diameter: Physical adsorption and desorption test (BET) Mechanical strength: Particle crushing instrument.

[0044] The results are shown in Table 1: Table 1.

[0046] As can be seen from Table 1, in the preparation process of biomass activated carbon, the alkali-carbon ratio, curing temperature / time parameters, and activation temperature / time parameters will all affect the pore volume and mechanical strength of biomass activated carbon. When the alkali-carbon ratio is 2 - 2.5:1, curing can be omitted and the activation process can be directly carried out. And when the inorganic bases are KOH and NaOH (the ratio of the two is 1:1.5), the obtained activated carbon has the largest pore volume (1.3 cm 3 / g), and at the same time, the mechanical strength can still be maintained at 23 Mpa, achieving the optimal pore volume / strength (refer to Preparation Example 2). When the alkali-carbon ratio is 1.5 - 1.8:1, it is necessary to cure at a specific temperature for a certain time to obtain activated carbon with the best pore volume / strength parameters (refer to Preparation Example 6 and Comparative Examples 1, 4, 5). At the same time, even with the same ratio of carbon-carbon ratio, the curing temperature and time parameters will further affect the properties of activated carbon.

[0047] Example 1 This example provides a high-capacity silicon-carbon anode material, and its preparation method includes: Using the biomass activated carbon (D2-I 2 / 1 -800-1) obtained in Preparation Example 1 as the matrix; A vertical fluidized bed with a diameter of Φ500 mm and a height-to-diameter ratio of 1:4 was used for the chemical vapor deposition process. Silane was used as the silicon source, nitrogen was used as the carrier gas, the flow rate ratio was 1:7, the temperature was controlled at 450 °C, and the inlet gas time was 7 h to obtain the silicon-carbon core material.

[0048] Continue to carry out the chemical vapor deposition process in the above vertical fluidized bed. Acetylene was used as the carbon source, nitrogen was used as the carrier gas, the flow rate ratio was 1:6, the temperature was controlled at 590 °C, the coating time was 5 h, and it was cooled at a rate of 8 °C / min under nitrogen protection to form a thin carbon layer (specific surface area of 41 m 2 / g); The silicon-carbon core material with a thin carbon layer was taken out from the fluidized bed and placed in a rotary furnace. Acetylene was used as the carbon source, nitrogen was used as the carrier gas, the volume ratio was 1:2.5, the temperature was controlled at 570 °C, the coating time was 5 h, and carbon coating was carried out again on the surface of the thin carbon layer, and it was cooled at a rate of 8 °C / min under nitrogen protection to obtain the silicon-carbon composite negative electrode material (specific surface area of 3.2 m 2 / g).

[0049] Examples 2 - 6 The difference between this group of examples and Example 1 is that: The biomass activated carbon provided in Preparation Examples 2 - 6 was used as the matrix.

[0050] Comparative Examples 1 - 5 The difference between this group of comparative examples and Example 1 is that: The activated carbon provided in Comparative Preparation Examples 1 - 5 was used as the matrix.

[0051] Comparative Example 6 The difference between this comparative example and Example 1 is that only one carbon coating was carried out using a vertical fluidized bed, and no secondary carbon coating was carried out. The specific parameters are as follows: In the vertical fluidized bed, acetylene was used as the carbon source, nitrogen was used as the carrier gas, the flow rate ratio was 1:6, the temperature was controlled at 590 °C, the coating time was 10 h, and the cooling rate was 8 °C / min.

[0052] Comparative Example 7 The difference between this comparative example and Example 1 is that during the preparation of the silicon-carbon core material, silane was used as the silicon source, nitrogen was used as the carrier gas, the flow rate ratio was 1:4, the temperature was controlled at 450 °C, and the inlet gas time was 8 h.

[0053] The performance parameters of the silicon-carbon negative electrode materials obtained from the above examples and comparative examples were measured, and commercially available activated carbon was used as a control at the same time. The measurement method is as follows: Reversible capacity: The battery test system was charged and discharged in cycles, and the lithium insertion amount per unit mass of the material was calculated.

[0054] Initial efficiency: During the first charge and discharge of the battery test system, calculate the ratio of the discharge capacity to the charge capacity.

[0055] The results are shown in Table 2 as follows: Table 2.

[0056] As can be seen from Table 2, the reversible capacities of the silicon-carbon anode materials provided in Examples 1-6 are much higher than those of the commercially available activated carbon and Comparative Examples 1-5. This is mainly because the matrixes of Examples 1-6 are biomass activated carbons with larger pore volumes, which can provide a larger deposition space for silicon. At the same time, it can also ensure that the initial efficiency is within a relatively high range.

[0057] Comparing Example 1 with Comparative Examples 6 and 7, it can be seen that the flow rate ratio in the secondary coating and silicon-carbon deposition processes helps to improve the reversible capacity of the silicon-carbon anode material.

[0058] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A preparation process of a high-capacity silicon-carbon anode material, characterized in that, It includes: (1) Prepare biomass activated carbon with a total pore volume of 1.0 - 1.3 cm 3 / g and a compressive strength of 20 - 40 Mpa; (2) Put the biomass activated carbon into a fluidized bed, and use the fluidized bed chemical vapor deposition process. Using silane as the silicon source, deposit silicon nanoparticles in the pores and on the surface of the biomass activated carbon to obtain a silicon-carbon core material; then use acetylene as the carbon source to deposit a thin carbon layer on the surface of the silicon-carbon core material; (3) Export the silicon-carbon core material with a thin carbon layer from the fluidized bed, and use acetylene as the carbon source to perform secondary carbon coating in a rotary kiln to form a silicon-carbon negative electrode material.

2. The preparation process of the high-capacity silicon-carbon anode material according to claim 1, characterized in that The specific surface area of the biomass activated carbon ≥ 2150m 2 / g, the proportion of micropore volume is more than 62%, and the proportion of mesopore volume is less than 38%.

3. The preparation process of the high-capacity silicon-carbon anode material according to any one of claims 1 or 2, characterized in that, The preparation method of the biomass activated carbon includes: Select hard-shell plant raw materials and perform pretreatment to obtain biomass raw materials; Heat-treat the biomass raw materials in a carbonization furnace for 1.5 - 2.5 h to obtain carbonized materials; Mix the carbonized materials with inorganic alkali, and the alkali-carbon ratio is 1.5 - 2.5:

1. Put the mixed materials into an activation furnace and activate at 800 - 850 °C for 0.8 - 2 h to obtain activated materials; After crushing the activated materials, perform pickling, filtration, and airflow pulverization to obtain biomass activated carbon.

4. The preparation process of the high-capacity silicon-carbon anode material according to claim 3, characterized in that, Before putting the mixed materials into the activation furnace for activation, it also includes: Heat-treat the mixed materials at 450 - 550 °C for 1.5 - 2.5 h for curing; then heat-treat at 800 - 850 °C for 0.8 - 1.2 h for activation.

5. The preparation process of the high-capacity silicon-carbon anode material according to claim 4, characterized in that, After mixing the carbonized materials with inorganic alkali to obtain mixed materials, it also includes: adding an 8 - 15 vol% ethanol solution as a dispersant to the mixed materials.

6. The preparation process of the high-capacity silicon-carbon anode material according to claim 3, characterized in that, When preparing the carbonized materials, the heat treatment process is a programmed temperature rise process, including: The carbonization furnace is heated to 200 °C at a rate of 4 - 6 °C / min and held for 20 - 40 min; then heated to 380 - 420 °C at a rate of 4 - 6 °C / min and held for 20 - 40 min; finally heated to 600 - 650 °C at a rate of 4 - 6 °C / min and held for 1.5 - 2.5 h.

7. The preparation process of the high-capacity silicon-carbon anode material according to claim 1, characterized in that, In step (2), the flow rate ratio of the silane to the carrier gas is 1:7 - 8, the temperature is 440 - 460 °C, and the treatment time is 7 - 8 h; the flow rate ratio of the acetylene to the carrier gas is 1:6 - 7, the coating temperature is 580 - 600 °C, and the coating time is 5 - 6 h.

8. The preparation process of the high-capacity silicon-carbon anode material according to claim 1, characterized in that, In step (3), the flow rate ratio of the acetylene to the carrier gas is 1:2 - 3, the coating temperature is 560 - 580 °C, and the coating time is 4 - 6 h.

9. A high-capacity silicon-carbon anode material prepared by the preparation process according to any one of claims 1-8, characterized in that, The reversible capacity of the silicon-carbon negative electrode material ≥ 2000 mAh / g.

Images