Preparation method of silicon-carbon composite material for lithium ion battery

Abstract

The invention discloses a preparation method of a silicon-carbon composite material for a lithium ion battery. The method comprises the following steps: performing acid impregnation, water washing and drying on rice hulls, and carbonizing the rice hulls in an inert atmosphere to obtain rice hull carbon; the preparation method comprises the following steps: uniformly mixing rice hull carbon and silicon dioxide, adding a small amount of metal catalyst iron powder, uniformly mixing, filling into a quartz tube wrapped with graphite paper, carrying out rapid Joule heating once or multiple times, carrying out alkali washing on the product, and carrying out suction filtration and drying to obtain the low-resistance silicon-carbon composite material. The material can be used as a negative electrode material of a lithium ion battery. The raw materials are wide in source and low in cost; the adopted rapid joule pulse heating process is simple, convenient and high in efficiency; the obtained low-resistance silicon-carbon composite material has the advantages of high initial charge-discharge coulombic efficiency, high energy density, good cycle stability and the like as a negative electrode material of a lithium ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery electrode materials, and particularly relates to a preparation method of a silicon-carbon composite material for lithium ion batteries. BACKGROUND

[0002] Graphite-based negative electrode materials are the most common and successful commercial negative electrode, however, limited by the limited theoretical capacity (372 mAh / g) of carbon-based materials, the energy density of lithium ion batteries based on graphite negative electrodes is increasingly unable to meet people's needs. The lithium-silicon alloy phase structure is Li 4.4 Si, and its maximum specific capacity can reach 4200 mAh / g. In addition, silicon is the second most abundant element in the earth's crust (~27%). Therefore, silicon-based materials are considered as one of the most promising negative electrode materials. However, in practical application, when electrochemical charging and discharging form lithium-silicon alloy, the volume of silicon material will change greatly, up to 400% (Li 22 Si5), the mechanical stress generated by the repeated volume change of silicon material will cause the electrode material to crack and even pulverize, the long cycle stability is poor, and the electrochemical performance rapidly decays. In addition, silicon is an intrinsic semiconductor material, and the electrical conductivity is poor (room temperature conductivity is only 0.00067 S cm -1 -1), which greatly limits the diffusion rate of lithium ions in the silicon matrix, seriously affecting the practical application of silicon negative electrode materials. Therefore, the severe volume change of silicon-based negative electrode materials during repeated charging and discharging cycles and the low electrical conductivity are the most fundamental reasons hindering the development of silicon-based negative electrode materials.

[0003] In recent years, researchers have improved the cycle performance of silicon-based materials to some extent by modifying silicon through nanocrystallization, carbon coating, and preparing silicon alloys. Biomass rice husk contains 17-20% silicon dioxide, and contains a large amount of carbon and silicon dioxide. After pyrolysis, C / SiO2 initial skeleton will be formed, which provides a natural three-dimensional porous network for the structure of the subsequent silicon-carbon composite material. The patent "Silicon-carbon composite material and preparation method thereof" (application number 201911259831.X) uses silicon-rich biomass rice husk as a silicon and carbon source. After pre-oxidation, activation and catalytic carbonization treatment, silicon-carbon composite materials are prepared by one-step method using metal powder to reduce biomass source silicon dioxide at low temperature. Although silicon has been successfully reduced, the specific surface area of the prepared silicon-carbon composite material is high, and magnesium metal is required during the thermal reduction process. The patent "Preparation method of lithium ion battery negative electrode material" (application number 201310556327.2) obtains a porous silicon-carbon composite material by acid washing, high-temperature pyrolysis of rice husk, and high-temperature reduction with metallic powder (magnesium, aluminum, etc.). The preparation process also requires metallic powder. The above patents show that rice husk can obtain silicon-carbon composite materials by high-temperature reduction with metallic powder, but this process has safety hazards such as flammability and explosion in actual production. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of silicon-carbon composite material for lithium ion battery.

[0005] The above-mentioned purpose of the present application is realized by the following technical scheme: The preparation method of silicon-carbon composite material for lithium ion battery comprises the following steps: 1) rice husk is immersed in acid, washed with water, dried, and carbonized to obtain rice husk carbon; 2) the rice husk carbon is mixed with silicon dioxide to obtain a mixture, then iron powder as a metal catalyst is added and mixed uniformly, and then the mixture is loaded into a quartz tube wrapped with graphite paper, and subjected to one or more rapid Joule pulse heating in an inert atmosphere to obtain a product; 3) the product is subjected to alkali washing, then filtered and dried to obtain a silicon-carbon composite material with low resistance.

[0006] Unlike traditional high-temperature thermal reduction through slow heating rates, rapid Joule heating technology directly applies direct current to the precursor, achieving ultra-rapid heating (up to 4000 °C / s) to the target temperature within seconds via Joule heating. This temperature is then briefly maintained under an inert atmosphere, resulting in efficient activation. Finally, cooling occurs at an extremely rapid rate (approximately 2 × 10³ °C / s). This invention uses rice husks as the precursor for silicon-based anode materials, adding silicon dioxide and iron powder catalysts. Utilizing rapid Joule pulse heating technology, a low-resistivity silicon-carbon composite material is formed. This material, used as the anode in lithium-ion batteries, exhibits high initial coulombic efficiency, high energy density, and good cycle stability.

[0007] Furthermore, the acid is a hydrochloric acid solution or a nitric acid solution with a concentration of 5wt% to 30wt%, and the acid immersion time is 1 to 24 hours.

[0008] Furthermore, the water washing is performed with deionized water 3 to 6 times until the pH reaches 5 to 7.

[0009] Furthermore, the carbonization is carried out under an inert atmosphere at 400°C for 30-60 minutes.

[0010] Furthermore, the mass ratio of rice husk carbon to silicon dioxide is 1:0.1~2.

[0011] Furthermore, the amount of iron powder added as the metal catalyst is 0.01% to 1% of the mass of the mixture.

[0012] Furthermore, the inert atmosphere is one of nitrogen, argon, and helium.

[0013] Furthermore, the rapid Joule pulse heating process has a heating rate of 500-1000 ℃ / s and a heating time of 1000℃~1500℃ for 1~20 seconds.

[0014] Furthermore, the number of rapid Joule pulse heating cycles is 2 to 50.

[0015] Furthermore, the alkaline washing is performed using a sodium hydroxide solution with a mass concentration of 5% to 40%, and the drying is performed at 80 to 120°C for 12 to 24 hours.

[0016] The present invention has the following beneficial effects: (1) After the biomass rice husk is pyrolyzed, it will form a C / SiO2 initial skeleton, which is a natural three-dimensional porous uniform coating network that can better coat nano-silicon and overcome the easy expansion phenomenon of silicon-carbon materials.

[0017] (2) The rapid Joule heating technology used in this invention is based on the Joule pulse heating principle. It has a fast heating rate, a short preparation process duration, and a fast cooling rate. Therefore, the preparation process is simple and efficient. Furthermore, due to the short preparation process time, the formation of silicon carbide can be effectively suppressed.

[0018] (3) In this invention, the rice husk mixture is subjected to pulsed thermal shock in a temperature range of 1000℃~1500℃. Under this process, a portion of the carbon in the rice husk thermally reduces the silicon dioxide in the rice husk to nano-silicon. The added silicon dioxide can inhibit the formation of silicon carbide, and the remaining carbon forms a carbon network structure with low resistance that tightly encapsulates the nano-silicon.

[0019] (4) The present invention adds a small amount of metallic iron powder as a catalyst, which can inhibit the formation of silicon carbide and promote the precipitation of elemental silicon.

[0020] (5) The present invention uses one or more Joule thermal pulse discharges to reduce the resistance of silicon-carbon composite materials and improve their conductivity.

[0021] (6) The silicon-carbon composite material prepared by the present invention can be used as the negative electrode of lithium-ion batteries, and has the characteristics of high initial coulombic efficiency, high energy density and good cycle stability. Attached Figure Description

[0022] Figure 1 The graph shows the electrochemical performance of the silicon-carbon composite material prepared in Example 2 of this invention after 200 cycles.

[0023] Figure 2 The graph shows the first charge-discharge electrochemical performance of the silicon-carbon composite material prepared in Example 2 of this invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments.

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention. Example 1

[0026] The preparation method of silicon-carbon composite material for lithium-ion batteries includes the following steps: 1) Soak 10g of rice husks in a 5% dilute hydrochloric acid solution for 12 hours to remove ash impurities (metal impurities, etc.) from the rice husks by acid washing. Then wash with deionized water and filter 5 times until the pH is 6.2. Dry in an oven at 105℃ for 12 hours and then carbonize in a nitrogen atmosphere at 400℃ for 1 hour to obtain rice husk carbon. 2) Mix rice husk carbon and silicon dioxide at a mass ratio of 1:1 to obtain a mixture. Then add 0.05% of the mass of the mixture of iron powder as a metal catalyst and mix evenly. Then pack the mixture into a quartz tube wrapped with graphite paper. 3) Place the rice husk carbon mixture in the quartz tube into a Joule heating device, introduce an argon atmosphere, and rapidly heat it three times with a Joule pulse. The Joule pulse process is set with a heating rate of 1000 ℃ / s and a heating time of 5 seconds at 1300℃ to obtain the product. 4) The above product was washed with 5% sodium hydroxide solution, then washed with deionized water, filtered 5 times, and dried in an oven at 90℃ for 24 hours to obtain a silicon-carbon composite material with low electrical resistance.

[0027] 5) The prepared low-resistance silicon-carbon composite material was used as the negative electrode material of lithium-ion batteries and assembled into button cells for charge-discharge performance testing: The active material (silicon-carbon composite material), conductive agent (conductive carbon black), and binder (PVDF) were mixed uniformly at a mass ratio of 8:1:1 to form an electrode sheet as the working electrode, and a lithium metal sheet as the counter electrode. The electrolyte was LiPF6 as the solute and ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1 as the solvent. Celgard 2300 was used as the separator. The cells were assembled in an argon-filled glove box to obtain the CR2025 button cell.

[0028] 6) Testing the assembled button cells: The battery system was used to test the charge-discharge cycle performance of the cells under constant current, with a charge-discharge voltage range of 0.01-3.0 V and a current density of 0.1 C.

[0029] Test results: (1) The resistance results show that the resistance of the silicon-carbon composite material obtained in Implementation Case 1 is 0.3Ω.

[0030] (2) The silicon-carbon composite material has a first charge-discharge specific capacity of 650 mAh / g and 632 mAh / g at 0.1C, respectively, and a first coulombic efficiency of 97.23%. After 100 cycles, the discharge specific capacity is 621 mAh / g with a capacity retention rate of 98.26%. After 200 cycles, the discharge specific capacity is 613 mAh / g with a capacity retention rate of 96.99%. Example 2

[0031] The preparation method of silicon-carbon composite material for lithium-ion batteries includes the following steps: 1) Soak 10g of rice husks in 8% dilute hydrochloric acid solution for 9 hours to remove ash impurities (metal impurities, etc.) from the rice husks by acid washing. Then wash with deionized water and filter 5 times until the pH is 6.0. Dry in an oven at 105℃ for 12 hours and then carbonize in a nitrogen atmosphere at 400℃ for 1 hour to obtain rice husk carbon. 2) Mix rice husk carbon and silicon dioxide at a mass ratio of 1:1.2 to obtain a mixture. Then add 0.08% of the mass of the mixture of iron powder as a metal catalyst and mix evenly. Then pack the mixture into a quartz tube wrapped with graphite paper. 3) Place the rice husk carbon mixture in the quartz tube into a Joule heating device, introduce an argon atmosphere, and rapidly pulse Joules three times. The Joule pulse process is set with a heating rate of 1000 ℃ / s and a heating time of 5 seconds at 1450 ℃ to obtain the product. 4) The above product was washed with 5% sodium hydroxide solution, then washed with deionized water, filtered 5 times, and dried in an oven at 90℃ for 24 hours to obtain a silicon-carbon composite material with low electrical resistance.

[0032] 5) The prepared low-resistance silicon-carbon composite material was used as the negative electrode material of lithium-ion batteries and assembled into button cells for charge-discharge performance testing: The active material (silicon-carbon composite material), conductive agent (conductive carbon black), and binder (PVDF) were mixed uniformly at a mass ratio of 8:1:1 to form an electrode sheet as the working electrode, and a lithium metal sheet as the counter electrode. The electrolyte was LiPF6 as the solute and ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1 as the solvent. Celgard 2300 was used as the separator. The cells were assembled in an argon-filled glove box to obtain the CR2025 button cell.

[0033] 6) Test the assembled button cells: Use a battery system to test the charge-discharge cycle performance of the cells under constant current, with a charge-discharge voltage range of 0.01-3.0 V and a current density of 0.1 C.

[0034] Test results: (1) The resistance results show that the resistance of the silicon-carbon composite material obtained in Implementation Case 2 is 0.24Ω.

[0035] (2) The silicon-carbon composite material has a first charge-discharge specific capacity of 880 mAh / g and 864 mAh / g at 0.1C, respectively, and a first coulombic efficiency of 98.18%. After 100 cycles, the discharge specific capacity is 850 mAh / g with a capacity retention rate of 98.38%. After 200 cycles, the discharge specific capacity is 841 mAh / g with a capacity retention rate of 97.34%. Example 3

[0036] The preparation method of silicon-carbon composite material for lithium-ion batteries includes the following steps: 1) Soak 10g of rice husks in a 30% dilute hydrochloric acid solution for 1 hour to remove ash impurities (metal impurities, etc.) from the rice husks by acid washing. Then wash with deionized water and filter 5 times until the pH is 6.4. Dry in an oven at 105℃ for 12 hours and then carbonize in a nitrogen atmosphere at 400℃ for 1 hour to obtain rice husk carbon. 2) Mix rice husk carbon and silicon dioxide at a mass ratio of 1:0.8 to obtain a mixture. Then add 0.06% of the mass of the mixture of iron powder, a metal catalyst, and mix evenly. Then pack the mixture into a quartz tube wrapped with graphite paper. 3) Place the rice husk carbon mixture in a quartz tube on a Joule heating device, introduce an argon atmosphere, and rapidly heat twice with a Joule pulse. The Joule pulse process is set with a heating rate of 1000 ℃ / s and a heating time of 5 seconds at 1400℃ to obtain the product. 4) The product was washed with 10% sodium hydroxide solution, then washed with deionized water, filtered 5 times, and dried in an oven at 90℃ for 24 hours to obtain a silicon-carbon composite material with low electrical resistance.

[0037] 5) The prepared low-resistance silicon-carbon composite material was used as the negative electrode material of lithium-ion batteries and assembled into button cells for charge-discharge performance testing: The active material (silicon-carbon composite material), conductive agent (conductive carbon black), and binder (PVDF) were mixed uniformly at a mass ratio of 8:1:1 to form an electrode sheet as the working electrode, and a lithium metal sheet as the counter electrode. The electrolyte was LiPF6 as the solute and ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1 as the solvent. Celgard 2300 was used as the separator. The cells were assembled in an argon-filled glove box to obtain the CR2025 button cell.

[0038] 6) Test the assembled button cells: Use a battery system to test the charge-discharge cycle performance of the cells under constant current, with a charge-discharge voltage range of 0.01-3.0 V and a current density of 0.1 C.

[0039] Test results: (1) The resistance results show that the resistance of the silicon-carbon composite material obtained in Implementation Case 3 is 0.45Ω. (2) The silicon-carbon composite material has a first charge-discharge specific capacity of 705 mAh / g and 685 mAh / g at 0.1C, respectively, and a first coulombic efficiency of 97.16%. After 100 cycles, the discharge specific capacity is 668 mAh / g with a capacity retention rate of 97.52%. After 200 cycles, the discharge specific capacity is 656 mAh / g with a capacity retention rate of 95.77%. Example 4

[0040] The preparation method of silicon-carbon composite material for lithium-ion batteries includes the following steps: 1) Soak 10g of rice husks in a 20% dilute hydrochloric acid solution for 1 hour to remove ash impurities (metal impurities, etc.) from the rice husks by acid washing. Then wash with deionized water and filter 5 times until the pH is 6.6. Dry in an oven at 105℃ for 12 hours and then carbonize in a nitrogen atmosphere at 400℃ for 1 hour to obtain rice husk carbon. 2) Mix the rice husk carbon obtained in step 1 with silicon dioxide at a mass ratio of 1:1.5 to obtain a mixture. Then add 0.08% of the mass of the mixture of iron powder as a metal catalyst and mix evenly. Then pack the mixture into a quartz tube wrapped with graphite paper. 3) Place the rice husk carbon mixture in the quartz tube on a Joule heating device, introduce an argon atmosphere, and rapidly heat it twice with a Joule pulse. The Joule pulse process is set with a heating rate of 1000 ℃ / s and a heating time of 15 seconds at 1000 ℃. 4) The obtained product was washed with 20% sodium hydroxide solution, then washed with deionized water, filtered 5 times, and dried in an oven at 90℃ for 24 hours to obtain a silicon-carbon composite material with low electrical resistance.

[0041] 5) The prepared low-resistance silicon-carbon composite material was used as the negative electrode material of lithium-ion batteries and assembled into button cells for charge-discharge performance testing: The active material (silicon-carbon composite material), conductive agent (conductive carbon black), and binder (PVDF) were mixed uniformly at a mass ratio of 8:1:1 to form an electrode sheet as the working electrode, and a lithium metal sheet as the counter electrode. The electrolyte was LiPF6 as the solute and ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1 as the solvent. Celgard 2300 was used as the separator. The cells were assembled in an argon-filled glove box to obtain the CR2025 button cell.

[0042] 6) Test the assembled button cells: Use a battery system to test the charge-discharge cycle performance of the cells under constant current, with a charge-discharge voltage range of 0.01-3.0 V and a current density of 0.1 C.

[0043] Test results: (1) The resistance results show that the resistance of the silicon-carbon composite material obtained in Implementation Case 4 is 4.2Ω.

[0044] (2) The silicon-carbon composite material has a first charge-discharge specific capacity of 480 mAh / g and 456 mAh / g at 0.1C, respectively, and a first coulombic efficiency of 95%. After 100 cycles, the discharge specific capacity is 420 mAh / g with a capacity retention rate of 92.11%. After 200 cycles, the discharge specific capacity is 402 mAh / g with a capacity retention rate of 88.16%. Example 5

[0045] The preparation method of silicon-carbon composite material for lithium-ion batteries includes the following steps: 1) Soak 10g of rice husks in a 10% dilute hydrochloric acid solution for 1 hour to remove ash impurities (metal impurities, etc.) from the rice husks by acid washing. Then wash with deionized water and filter 5 times until the pH is 6.9. Dry in an oven at 105℃ for 12 hours and then carbonize in a nitrogen atmosphere at 400℃ for 1 hour to obtain rice husk carbon. 2) Mix rice husk carbon and silicon dioxide at a mass ratio of 1:1.2 to obtain a mixture. Then add 0.08% by mass of the metal catalyst iron powder to the mixture and mix evenly. Then pack the mixture into a quartz tube wrapped with graphite paper. 3) Place the rice husk carbon mixture in the quartz tube on a Joule heating device, introduce an argon atmosphere, and rapidly pulse Joules 4 times. The Joule pulse process is set with a heating rate of 1000 ℃ / s and a heating time of 12 seconds at 1500 ℃. 4) The obtained product was washed with 5% sodium hydroxide solution, then washed with deionized water, filtered 5 times, and dried in an oven at 90℃ for 24 hours to obtain a silicon-carbon composite material with low electrical resistance.

[0046] 5) The prepared low-resistance silicon-carbon composite material was used as the negative electrode material of lithium-ion batteries and assembled into button cells for charge-discharge performance testing: The active material (silicon-carbon composite material), conductive agent (conductive carbon black), and binder (PVDF) were mixed uniformly at a mass ratio of 8:1:1 to form an electrode sheet as the working electrode, and a lithium metal sheet as the counter electrode. The electrolyte was LiPF6 as the solute and ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1 as the solvent. Celgard 2300 was used as the separator. The cells were assembled in an argon-filled glove box to obtain the CR2025 button cell.

[0047] 6) The assembled button cells were tested using a battery system to test their charge-discharge cycle performance under constant current. The charge-discharge voltage range was 0.01-3.0 V, and the current density was 0.1 C.

[0048] Test results: (1) The resistance results show that the resistance of the silicon-carbon composite material obtained in Implementation Case 5 is 0.15Ω.

[0049] (2) The silicon-carbon composite material has a first charge-discharge specific capacity of 715 mAh / g and 702 mAh / g at 0.1C, respectively, and a first coulombic efficiency of 98.18%. After 100 cycles, the discharge specific capacity is 685 mAh / g with a capacity retention rate of 97.58%. After 200 cycles, the discharge specific capacity is 682 mAh / g with a capacity retention rate of 97.15%. Example 6

[0050] The preparation method of silicon-carbon composite material for lithium-ion batteries includes the following steps: 1) Soak 10g of rice husks in a 10% dilute hydrochloric acid solution for 1 hour to remove ash impurities (metal impurities, etc.) from the rice husks by acid washing. Then wash with deionized water and filter 5 times until the pH is 6.9. Dry in an oven at 105℃ for 12 hours and then carbonize in a nitrogen atmosphere at 400℃ for 1 hour to obtain rice husk carbon. 2) Mix rice husk carbon and silicon dioxide at a mass ratio of 1:1 to obtain a mixture. Then add 0.1% of the metal catalyst iron powder to the mixture and mix well. Then put it into a quartz tube wrapped with graphite paper. 3) Place the rice husk carbon mixture in the quartz tube into a graphitization furnace, introduce an argon atmosphere, set the heating rate to 5 ℃ / s, and heat at 1500℃ for 30 seconds to obtain the product; 4) The above product was washed with 5% sodium hydroxide solution, then washed with deionized water, filtered 5 times, and dried in an oven at 90℃ for 24 hours to obtain a silicon-carbon composite material with low electrical resistance.

[0051] 5) The prepared low-resistance silicon-carbon composite material was used as the negative electrode material of lithium-ion batteries and assembled into button cells for charge-discharge performance testing: The active material (silicon-carbon composite material), conductive agent (conductive carbon black), and binder (PVDF) were mixed uniformly at a mass ratio of 8:1:1 to form an electrode sheet as the working electrode, and a lithium metal sheet as the counter electrode. The electrolyte was LiPF6 as the solute and ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1 as the solvent. Celgard 2300 was used as the separator. The cells were assembled in an argon-filled glove box to obtain the CR2025 button cell.

[0052] 6) The assembled button cells were tested using a battery system to test their charge-discharge cycle performance under constant current. The charge-discharge voltage range was 0.01-3.0 V, and the current density was 0.1 C.

[0053] Test results: (1) The resistance results show that the resistance of the silicon-carbon composite material obtained in Implementation Case 6 is 4.4Ω.

[0054] (2) The silicon-carbon composite material has a first charge-discharge specific capacity of 550 mAh / g and 528 mAh / g at 0.1C, respectively, and a first coulombic efficiency of 96.00%. After 100 cycles, the discharge specific capacity is 476 mAh / g with a capacity retention rate of 90.15%. After 200 cycles, the discharge specific capacity is 466 mAh / g with a capacity retention rate of 88.26%.

[0055] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing silicon-carbon composite materials for lithium-ion batteries, characterized in that, Includes the following steps: 1) Rice husks are acid-soaked, washed, dried, and carbonized to obtain rice husk carbon; 2) Mix rice husk carbon and silicon dioxide evenly to obtain a mixture, then add iron powder metal catalyst and mix evenly, then put it into a quartz tube wrapped with graphite paper, and heat it once or multiple times with rapid Joule pulses under an inert atmosphere to obtain the product. 3) The product was washed with alkali and then filtered and dried to obtain a silicon-carbon composite material with low electrical resistance.

2. The method for preparing silicon-carbon composite material for lithium-ion batteries according to claim 1, characterized in that, The acid is a hydrochloric acid solution or a nitric acid solution with a concentration of 5wt% to 30wt%, and the acid immersion time is 1 to 24 hours.

3. The method for preparing silicon-carbon composite material for lithium-ion batteries according to claim 1, characterized in that, The water washing involves washing with deionized water 3 to 6 times until the pH reaches 5 to 7.

4. The method for preparing silicon-carbon composite material for lithium-ion batteries according to claim 1, characterized in that, The carbonization is carried out under an inert atmosphere at 400°C for 30-60 minutes.

5. The method for preparing silicon-carbon composite material for lithium-ion batteries according to claim 1, characterized in that, The mass ratio of rice husk carbon to silicon dioxide is 1:0.1~2.

6. The method for preparing silicon-carbon composite material for lithium-ion batteries according to claim 1, characterized in that, The amount of iron powder added as the metal catalyst is 0.01% to 1% of the mass of the mixture.

7. The method for preparing silicon-carbon composite material for lithium-ion batteries according to claim 1, characterized in that, The inert atmosphere is one of nitrogen, argon, and helium.

8. The method for preparing silicon-carbon composite material for lithium-ion batteries according to claim 1, characterized in that, The rapid Joule pulse heating process is characterized by a heating rate of 500-1000 ℃ / s and heating at a temperature of 1000℃~1500℃ for 1~20 seconds.

9. The method for preparing silicon-carbon composite material for lithium-ion batteries according to claim 1, characterized in that, The number of rapid Joule pulse heating cycles is 2 to 50.

10. The method for preparing silicon-carbon composite material for lithium-ion batteries according to claim 1, characterized in that, The alkaline washing is performed using a sodium hydroxide solution with a mass concentration of 5% to 40%, and the drying is performed at 80 to 120°C for 12 to 24 hours.

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