High-energy silicon-carbon composite negative electrode material for lithium ion battery and preparation process of high-energy silicon-carbon composite negative electrode material

Abstract

The invention relates to the field of lithium battery negative electrode materials, and particularly discloses a high-energy silicon-carbon composite negative electrode material for a lithium ion battery and a preparation process of the high-energy silicon-carbon composite negative electrode material. The preparation method comprises the following steps: mixing resin-based activated carbon and biomass activated carbon with specific pore volume and compressive strength according to a mass ratio of 1: (0.2-0.3) to obtain a porous carbon matrix; depositing silicon nanoparticles on the porous carbon substrate by adopting a fluidized bed chemical vapor deposition process; 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 composite negative electrode material prepared by the process, the resin-based activated carbon is used as a main matrix, so that the influence of more impurities and non-uniform pore structure distribution of biomass activated carbon on the cycling stability and conductivity of the silicon-carbon negative electrode material is reduced, and the problems of volume expansion and conductivity of the silicon-based negative electrode material are solved.

Description

Technical Field

[0001] The present application relates to the field of lithium-ion battery anode materials, and more specifically, to a high-energy silicon-carbon composite anode material for lithium-ion batteries and its preparation process. Background Art

[0002] As a key branch of modern energy storage technology, lithium-ion batteries have achieved rapid development in recent years. As the core component of lithium-ion batteries, the anode material plays a decisive role in the overall performance of the battery. Among them, silicon-based anode materials have become the focus of current research because their theoretical specific capacity far exceeds that of traditional graphite materials. However, in practical applications, silicon-based anode materials still face many challenges, especially the crack problem caused by volume expansion during cycling and the need to improve electrical conductivity, which pose higher requirements for the research and development of silicon-based anode materials.

[0003] In the preparation of traditional lithium-ion battery anode materials, certain achievements have been made in the research of silicon-based anode materials. For example, silicon-carbon composite materials are prepared by chemical vapor deposition. When using a fluidized bed for chemical vapor deposition to prepare silicon-carbon materials with porous carbon as the matrix, extremely high requirements are placed on the mechanical strength and purity of the porous carbon. This is because the mechanical strength of porous carbon is usually negatively correlated with the pore volume, and the pore volume directly affects the deposition space of silicon and buffers the volume expansion of the silicon-carbon material during cycling. At the same time, impurities in the porous carbon directly affect the uniformity of the deposited silicon, and the insulating phases formed by some impurities in the carbon skeleton hinder electron transport and reduce the electrical conductivity of the silicon-carbon composite material.

[0004] In view of this, in order to further solve the volume expansion problem and electrical conductivity problem of silicon-based anode materials, the present application is proposed. Summary of the Invention

[0005] To solve the above problems, the present application provides a high-energy silicon-carbon composite anode material for lithium-ion batteries and its preparation process.

[0006] The present application adopts the following technical solutions: In the first aspect, the present application provides a preparation process for a high-energy silicon-carbon composite anode material for lithium-ion batteries, which includes: (1) Using phenolic resin as the raw material, preparing resin-based activated carbon with a total pore volume of 0.8 - 0.95 cm 3 / g and a compressive strength of 10 - 20 Mpa; (2) Using hard-shell plant raw materials, preparing biomass activated carbon with a total pore volume of 1.0 - 1.3 cm 3 / g and a compressive strength of 20 - 40 Mpa; (3) Mix the resin-based activated carbon and biomass activated carbon in a mass ratio of 1:0.2 - 0.3 to obtain a porous carbon matrix; (4) Put the porous carbon matrix into a fluidized bed, and use the fluidized bed chemical vapor deposition process. Using silane as the silicon source, the flow rate ratio of silane to the carrier gas is 1:7 - 8, the temperature is 440 - 460 °C, and the treatment time is 7 - 8 h 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; (5) Export the silicon-carbon core material with a thin carbon layer from the fluidized bed, use acetylene as the carbon source, and perform secondary carbon coating in a rotary kiln. The flow rate ratio is 1:2 - 3, the coating temperature is 560 - 580 °C, and the coating time is 4 - 6 h to form a silicon-carbon negative electrode material.

[0007] Furthermore, the porous carbon matrix also includes carbon nanotubes, and the mass ratio of the resin-based activated carbon to the carbon nanotubes is 1:0.05 - 0.1.

[0008] Furthermore, the preparation methods of the above-mentioned biomass activated carbon and resin-based activated carbon include: Select hard-shell plant raw materials or phenolic resin and perform pretreatment; Heat-treat the material obtained after pretreatment in a carbonization furnace for 1.5 - 2.5 h to obtain a carbonized material; Mix the carbonized material with an inorganic base, and the base-carbon ratio is 1.5 - 2.5:1. Put the mixed material into an activation furnace and activate it at 800 - 850 °C for 0.8 - 2 h to obtain an activated material; After crushing the activated material, perform pickling, filtration, and airflow pulverization to obtain biomass activated carbon or resin-based activated carbon.

[0009] Furthermore, before putting the mixed material into the activation furnace for activation, it also includes: Heat-treat the mixed material in the activation furnace at 450 - 550 °C for 1.5 - 2.5 h for curing; then heat-treat it at 800 - 850 °C for 0.8 - 1.2 h for activation.

[0010] Furthermore, the above-mentioned inorganic base is KOH and NaOH, and the mass ratio of KOH, NaOH to the carbonized material is 1:1 - 1.5:1.

[0011] Furthermore, during the preparation of the resin-based activated carbon, the heat treatment process for preparing the carbonized material is gradient programmed heating, including: The carbonization furnace is heated from 4 - 6 °C / min to 100 - 200 °C and kept warm for 1 - 2 h; then heated from 4 - 6 °C / min to 600 - 650 °C and kept warm for 1.5 - 2.5 h.

[0012] Further, in the process of preparing the biomass activated carbon, the heat treatment process for preparing the carbonized material is gradient programmed heating, 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.

[0013] Further, the content of silicon in the above silicon-carbon core material is 40 - 50 wt%; the specific surface area of the thin carbon layer is 30 - 50 m 2 / g; the specific surface area of the high-energy silicon-carbon composite negative electrode material is 3 - 5 m 2 / g.

[0014] In a second aspect, the present application provides a high-energy silicon-carbon composite negative electrode material for a lithium-ion battery prepared by the above preparation process.

[0015] In summary, the present application has the following beneficial effects: The present application uses a resin-based activated carbon prepared from phenolic resin as the matrix, doped with a small amount of biomass activated carbon prepared from hard-shell plant raw materials. The two can complement each other's advantages. On the one hand, the proportion of biomass activated carbon is reduced, reducing the influence of the large amount of impurities and uneven pore structure distribution of biomass activated carbon on the cycle stability and conductivity of the silicon-carbon negative electrode material; at the same time, the advantages of biomass activated carbon with rich pore structure, large pore volume, high mechanical strength and wide raw material sources can be utilized; on the other hand, the resin-based activated carbon is obtained by carbonizing high molecular polymers, with a more uniform void structure and higher purity. Taking it as the main matrix helps to improve the cycle stability and conductivity of the material.

[0016] After subsequent fluidized bed chemical vapor deposition of a thin carbon layer and secondary carbon coating in a rotary furnace, a double-layer functionalized carbon coating structure is formed, which can effectively alleviate the problem of easy cracking of single-layer carbon coating. The inner carbon coating provides good mechanical support, and the outer carbon coating further enhances the effect of isolating the electrolyte.

[0017] In the preferred technical solution, carbon nanotubes are added to the porous carbon matrix. As a conductive agent, carbon nanotubes can improve the conductivity of the mixed porous carbon matrix, thereby enhancing the electron transport ability inside the silicon-carbon material. When preparing the silicon-carbon negative electrode material, this mixed porous carbon matrix is beneficial to improving the cycle stability of the silicon-carbon material, alleviating the stress generated by the volume expansion of silicon during charge and discharge, inhibiting crack generation, and can also improve the conductivity of the silicon-carbon material and its overall electrochemical performance, so that the performance of the high-energy silicon-carbon composite negative electrode material for lithium-ion batteries prepared is better.

[0018] In the process of preparing the porous carbon matrix, whether it is resin-based activated carbon or biomass activated carbon, both have a large total pore volume and compressive strength, effectively balancing the high pore volume and mechanical strength, and forming a hierarchical pore structure, effectively improving the overall stability and capacity of the material. Detailed Embodiments

[0019] The following will describe the embodiments of the present invention in detail. 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 for the manufacturer can be obtained as conventional products through commercial purchase.

[0020] 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.

[0021] For the convenience of recording, the following rules are used to name the prepared samples: D 2 / 6 -Ⅰ 1 / 1 II 1 / 1 V 1 / 1 -t-n-T-m Wherein: D refers to the activated carbon matrix, where 2 refers to coconut shell as the raw material; 6 refers to phenolic resin as the raw material; I refers to KOH as the activator, II refers to NaOH as the activator, V refers to ZnCl2 as the activator, and the subscript refers to the alkali-carbon ratio; t refers to the curing temperature, n refers to the curing time; T refers to the activation temperature, and m refers to the activation time.

[0022] Preparation Example 1 This preparation example provides a method for preparing resin-based activated carbon, which includes: (1) Using phenolic resin powder as the raw material, put it into a rotary furnace, heat it to 200°C at a rate of 5°C / min, and keep it warm for 2 h; continue to heat it to 650°C at a rate of 5°C / min, and keep it warm for 2 h, with a gas flow rate of 5 L / min to obtain a carbonized material.

[0023] (2) Mix the carbonized material with an inorganic base. The inorganic base is KOH, and the alkali-carbon ratio is KOH:carbonized material = 2:1; during the mixing process, add the inorganic base to the carbonized material in three batches, and mix each batch for 20 min to obtain a mixed material.

[0024] (3) Put the mixed material into a tubular activation furnace and heat-treat it at 800°C for 60 min to obtain an activated material; (4) After crushing the activated material, soak it in an acid solution (0.5 M HCl) overnight, wash it with water until neutral, dry it, and pulverize it by air flow to D50 = 15 μm to obtain resin-based activated carbon, denoted as D6-Ⅰ2 / 1 -800 - 60

[0025] Preparation Example 2 The difference between this preparation example and Preparation Example 1 is as follows: Using phenolic resin powder as raw material, put it into a rotary kiln, heat it up to 100°C at a rate of 5°C / min and hold for 1 h; continue to heat it up to 170°C at a rate of 5°C / min and hold for 1 h; continue to heat it up to 650°C at a rate of 5°C / min and hold for 2 h, with a gas flow rate of 5 L / min to obtain carbonized material.

[0026] (2) Mix the carbonized material with inorganic bases. The inorganic bases are KOH and NaOH, and the alkali - carbon ratio is KOH:NaOH:carbonized material = 1:1:1; during the mixing process, add the inorganic bases to the carbonized material in three batches, and mix for 20 min each batch to obtain a mixed material.

[0027] The obtained resin - based activated carbon is denoted as D6 - Ⅰ 1 / 1 Ⅱ 1 / 1 -800 - 60

[0028] Preparation Example 3 The difference between this preparation example and Preparation Example 1 is as follows: (2) The inorganic bases are KOH and NaOH, and the alkali - carbon ratio is KOH:NaOH:carbonized material = 1:1:1; (3) The activation temperature is 850°C and the activation time is 60 min, The obtained resin - based activated carbon is denoted as D6 - Ⅰ 1 / 1 Ⅱ 1 / 1 -850 - 60

[0029] Preparation Example 4 The difference between this preparation example and Preparation Example 1 is as follows: (2) The inorganic bases are KOH and NaOH, and the alkali - carbon ratio is KOH:NaOH:carbonized material = 1:1:1; (3) The activation temperature is 850°C and the activation time is 90 min, The obtained resin - based activated carbon is denoted as D6 - Ⅰ 1 / 1 Ⅱ 1 / 1 -850 - 90

[0030] Preparation Example 5 The difference between this preparation example and Preparation Example 1 is as follows: (2) The inorganic base is KOH, and the alkali - carbon ratio is KOH:carbonized material = 1.5:1; (3) Activation steps: Heat - treat at 500°C for 120 min for curing; then heat - treat at 800°C for 60 min.

[0031] The obtained resin - based activated carbon is denoted as D6 - Ⅰ1.5 / 1- 500 - 120 - 800 - 60。

[0032] Preparation Example 6 The preparation method of biomass activated carbon provided by this preparation example includes: Using coconut shell as raw material, after pickling, it is washed until neutral, dried, and then heat-treated at 300 °C for 1 h for pre-oxidation. Subsequently, it is airflow pulverized to D50 = 150 μm to obtain biomass raw material; The biomass raw material is put into a rotary furnace for heat treatment. The rotary furnace is heated to 200 °C at a rate of 5 °C / min and kept at this temperature for 30 min; then it is heated to 400 °C at a rate of 5 °C / min and kept at this temperature for 30 min; finally, it is heated to 650 °C at a rate of 5 °C / min and kept at this temperature for 2 h, under nitrogen protection throughout the process (flow rate is 40 L / min), and the rotation speed is 25 Hz to obtain carbonized material.

[0033] Mix the carbonized material 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.

[0034] Put the mixed material into a tubular activation furnace and heat-treat it at 800 °C for 1 h 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.

[0035] Filter the biomass activated carbon obtained after airflow pulverization and label it as D2-I 2 / 1 -800 - 60。

[0036] Preparation Example 7 The difference between this preparation example and Preparation Example 6 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 1 h. The obtained activated carbon is labeled as D2-I 1 / 1 Ⅱ 1.5 / 1 -850 - 60。

[0037] Preparation Example 8 The difference between this preparation example and Preparation Example 6 is that: the inorganic base is KOH, and the alkali-carbon ratio is KOH:carbonized material = 1.5:1. The activation steps are: put the mixed material into a tubular activation furnace and heat-treat it at 500 °C for 2 h for curing; then heat-treat it at 800 °C for 50 min for activation. The obtained activated carbon is labeled as D2-I 1.5 / 1 -500 - 120 - 800 - 50。

[0038] Comparative Preparation Example 1 The difference between this preparation example and Preparation Example 1 is that: (2) The inorganic bases are KOH and ZnCl2, and the base-to-carbon ratio is KOH:ZnCl2:carbonized material = 1.5:0.5:1; (3) The activation temperature is 800 °C and the activation time is 60 min, The obtained resin-based activated carbon is denoted as D6-I 1.5 / 1 V 0.5 / 1 -800-60.

[0039] Comparative Preparation Example 2 The difference between this preparation example and Preparation Example 6 is: (2) The inorganic bases are KOH and NaOH, and the base-to-carbon ratio is KOH:NaOH:carbonized material = 1:1:1.5. (3) The activation step is: the activation temperature is 800, and it is treated for 60 min.

[0040] The obtained biomass activated carbon is denoted as D2-I 1 / 1.5 II 1 / 1.5 -800-60.

[0041] Comparative Preparation Example 3 The difference between this preparation example and Preparation Example 6 is: (2) The inorganic bases are KOH and NaOH, and the base-to-carbon ratio is KOH:NaOH:carbonized material = 1:1.5:1. (3) The activation step is: the activation temperature is 750, and it is treated for 90 min.

[0042] The obtained biomass activated carbon is denoted as D2-I 1 / 1 II 1.5 / 1 -750-90.

[0043] Comparative Preparation Example 4 The difference between this preparation example and Preparation Example 6 is: (2) The inorganic base is KOH, and the base-to-carbon ratio is KOH:carbonized material = 1.5:1. (3) The activation step is: heat treatment is carried out at 500 °C for 60 min for curing; subsequently, heat treatment is carried out at 850 °C for 50 min.

[0044] The obtained biomass activated carbon is denoted as D2-I 1.5 / 1 -500-60-850-50.

[0045] Comparative Preparation Example 5 The difference between this preparation example and Preparation Example 6 is: (2) The inorganic base is KOH, and the base-to-carbon ratio is KOH:carbonized material = 1.8:1. (3) The activation step is: heat treatment is carried out at 750 °C for 40 min for curing; subsequently, heat treatment is carried out at 850 °C for 50 min.

[0046] The obtained biomass activated carbon is denoted as D2-I 1.8 / 1 -750-40-850-50

[0047] The performance indexes of the activated carbon samples provided in the above preparation examples were detected, and a commercially available activated carbon was used as a comparison. The specific detection 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

[0048] The results are shown in Table 1 Table 1

[0049] As can be seen from Table 1, there are significant differences in the pore volume, pore structure, and strength between the resin-based activated carbon and the biomass activated carbon. For the resin-based activated carbon, by optimizing the process conditions, the pore volume can reach 0.82 - 0.95 cm 3 / g without significantly sacrificing the mechanical strength. For the biomass activated carbon, the pore volume can reach 1.01 - 1.3 cm 3 / g

[0050] Example 1 This example provides a high-energy silicon-carbon composite anode material for a lithium-ion battery, and its preparation process includes: (1) Mix the resin-based activated carbon and the biomass activated carbon according to a mass ratio of 1:0.2 to obtain a porous carbon matrix. Among them, the resin-based activated carbon is D6-I 2 / 1 -800-60 (provided by Preparation Example 1), and the biomass activated carbon is D2-I 2 / 1 -800-60 (provided by Preparation Example 6) (2) Use a vertical fluidized bed with a diameter of Φ500 mm and a height-to-diameter ratio of 1:4 for chemical vapor deposition process. Using silane as the silicon source and nitrogen as the carrier gas, with a flow ratio of 1:7, the temperature is controlled at 450 °C, and the inlet gas time is 7 h to obtain a silicon-carbon core material

[0051] (3) Continue to carry out the chemical vapor deposition process in the above vertical fluidized bed. Using acetylene as the carbon source and nitrogen as the carrier gas, with a flow ratio of 1:6, the temperature is controlled at 590 °C, and the coating time is 5 h. Then, it is cooled at a rate of 8 °C / min under nitrogen protection to form a thin carbon layer (specific surface area is 43 m 2 / g); (4) Export the silicon-carbon core material with a thin carbon layer from the fluidized bed and place it in a rotary furnace. Using acetylene as the carbon source and nitrogen as the carrier gas, with a volume ratio of 1:2, control the temperature at 560 °C, and the coating time is 5 h. Perform carbon coating again on the surface of the thin carbon layer, and cool it at a rate of 8 °C / min under nitrogen protection to obtain the silicon-carbon composite anode material (specific surface area is 3.5 m 2 / g).

[0052] Examples 2 - 5 The difference between this group of examples and Example 1 lies in the selection and ratio of resin-based activated carbon and biomass activated carbon, as shown in Table 2 specifically.

[0053] Example 6 The difference between this example and Example 3 is that the activated carbon matrix contains multi-walled carbon nanotubes (50 - 100 nm), and the mass ratio of resin-based activated carbon, biomass activated carbon, and multi-walled carbon nanotubes is 1: 0.2 : 0.05.

[0054] Example 7 The difference between this example and Example 3 is that the activated carbon matrix contains multi-walled carbon nanotubes (50 - 100 nm), and the mass ratio of resin-based activated carbon, biomass activated carbon, and multi-walled carbon nanotubes is 1: 0.2 : 0.1.

[0055] Comparative Examples 1 - 4 The difference between this group of comparative examples and Example 1 lies in the selection and ratio of resin-based activated carbon and biomass activated carbon, as shown in Table 2 specifically.

[0056] Comparative Example 5 The difference between this comparative example and Example 1 is that only resin-based activated carbon D6-I 1 / 1 II 1 / 1 -850 - 90 is used as the porous carbon matrix.

[0057] Comparative Example 6 The difference between this comparative example and Example 1 is that only biomass activated carbon D2-I 1 / 1 II 1.5 / 1 -850 - 60 is used as the porous carbon matrix.

[0058] Comparative Example 7 The difference between this comparative example and Example 1 is that resin-based activated carbon (D6-I 1 / 1 II 1 / 1 -850 - 90) and biomass activated carbon (D2-I 1 / 1 II 1.5 / 1 -850 - 60) are mixed in a mass ratio of 1:0.5 as the porous carbon matrix.

[0059] Comparative Example 8 The difference between this comparative example and Example 1 is that only vertical fluidized bed is used for primary carbon coating without secondary carbon coating. The specific parameters are as follows: In the vertical fluidized bed, acetylene is used as the carbon source and nitrogen is used as the carrier gas. The flow rate ratio is 1:6, the temperature is controlled at 590 °C, the coating time is 10 h, and the cooling rate is 8 °C / min.

[0060] Comparative Example 9 The difference between this comparative example and Example 1 is that in the preparation process of the silicon-carbon core material, silane is used as the silicon source, nitrogen is used as the carrier gas, the flow rate ratio is 1:4, the temperature is controlled at 450 °C, and the gas inlet time is 8 h.

[0061] The performance parameters of the silicon-carbon composite anode materials obtained in the above examples and comparative examples were measured, and commercially available activated carbon was used as a control at the same time. The measurement methods are as follows: (1) Reversible capacity: The battery test system was charged and discharged cyclically, and the lithium intercalation amount per unit mass of the material was calculated.

[0062] (2) Powder compaction resistivity: The four-probe method was used, and the resistivity was calculated by detecting the voltage drop by applying current.

[0063] The results are shown in Table 2: Table 2

[0064] As can be seen from Table 2, through the compounding of two activated carbons with different properties in Examples 1-7, the reversible capacity and conductivity of the obtained silicon-carbon anode materials are much higher than those of the anode materials using commercially available activated carbon or Comparative Examples 5-6. Specifically: When the ratio of resin-based activated carbon to bio-based activated carbon is 1:0.2, activated carbons with different pore volumes and mechanical strengths will have a significant impact on the reversible capacity and conductivity of the obtained silicon-carbon anode materials. Refer to Comparative Examples 1-4. When the addition amount of bio-based activated carbon is too much, it will affect the conductivity of the silicon-carbon anode material (see Comparative Example 7). At the same time, to further improve the conductivity, a small amount of carbon nanotubes was added in Example 6, reducing the resistivity.

[0065] Comparing Example 1 with Comparative Examples 8 and 9, it can be seen that the secondary coating and the flow rate ratio in the silicon-carbon deposition process help to improve the reversible capacity of the silicon-carbon anode material and reduce the resistivity.

[0066] This specific embodiment is only an explanation of the present application, and it does not limit the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, 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-energy silicon-carbon composite anode material for a lithium-ion battery, characterized in that, It includes: Using phenolic resin as a raw material, prepare a resin-based activated carbon with a total pore volume of 0.8 - 0.95 cm 3 / g and a compressive strength of 15 - 25 Mpa; 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 from raw materials of hard-shell plants; Mix the resin-based activated carbon and biomass activated carbon according to a mass ratio of 1:0.2 - 0.3 to obtain a porous carbon matrix; Put the porous carbon matrix into a fluidized bed, and adopt the fluidized bed chemical vapor deposition process. Using silane as the silicon source, the flow ratio of silane to the carrier gas is 1:7 - 8, the temperature is 440 - 460 °C, and the treatment time is 7 - 8 h 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; Export the silicon-carbon core material with a thin carbon layer from the fluidized bed, use acetylene as the carbon source, and perform secondary carbon coating in a rotary kiln. The flow ratio is 1:2 - 3, the coating temperature is 560 - 580 °C, and the coating time is 4 - 6 h to form a silicon-carbon negative electrode material.

2. The preparation process of the high-energy silicon-carbon composite anode material for lithium-ion batteries according to claim 1, characterized in that, The porous carbon matrix also includes carbon nanotubes, and the mass ratio of the resin-based activated carbon to the carbon nanotubes is 1:0.05 - 0.

1.

3. The preparation process of the high-energy silicon-carbon composite anode material for lithium-ion batteries according to claim 1, characterized in that, The preparation methods of the biomass activated carbon and the resin-based activated carbon include: Select hard-shell plant raw materials or phenolic resins for pretreatment; Perform heat treatment on the pretreated material in a carbonization furnace for 1.5 - 2.5 h to obtain a carbonized material; Mix the carbonized material with an inorganic base, and the alkali-carbon ratio is 1.5 - 2.5:

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

4. The preparation process of the high-energy silicon-carbon composite anode material for lithium-ion batteries according to claim 3, characterized in that, Before putting the mixed material into the activation furnace for activation, it also includes: Perform heat treatment on the mixed material in the activation furnace at 450 - 550 °C for 1.5 - 2.5 h for curing; then perform heat treatment at 800 - 850 °C for 0.8 - 1.2 h for activation.

5. The preparation process of the high-energy silicon-carbon composite anode material for lithium-ion batteries according to claim 3, characterized in that, The inorganic base is KOH and NaOH, and the mass ratio of KOH, NaOH to the carbonized material is 1:1 - 1.5:

1.

6. The preparation process of the high-energy silicon-carbon composite anode material for lithium-ion batteries according to any one of claims 3-5, characterized in that In the process of preparing the resin-based activated carbon, the heat treatment process of preparing the carbonized material is a gradient programmed temperature rise, including: The carbonization furnace is heated to 100 - 200 °C at a rate of 4 - 6 °C / min and held for 1 - 2 h; then 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-energy silicon-carbon composite anode material for lithium-ion batteries according to any one of claims 3-5, characterized in that, In the process of preparing the biomass activated carbon, the heat treatment process of preparing the carbonized material is a gradient programmed temperature rise, 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.

8. The preparation process of the high-energy silicon-carbon composite anode material for lithium-ion batteries according to claim 1, characterized in that, The content of silicon in the silicon-carbon core material is 40-50 wt%; the specific surface area of the thin carbon layer is 30-50 m 2 / g; the specific surface area of the high-energy silicon-carbon composite anode material is 3-5 m 2 / g.

9. A high-energy silicon-carbon composite anode material for a lithium-ion battery, characterized in that, The high-energy silicon-carbon composite negative electrode material is prepared by the preparation process described in any one of claims 1 - 8.

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