Preparation method of silicon-carbon composite material by vacuum thermal reduction method
By converting silicon-containing biomass into silicon-carbon composite materials through vacuum thermal reduction, the problems of volume expansion and conductivity of silicon anode materials are solved, achieving an efficient and environmentally friendly preparation process and improving the performance of lithium-ion batteries.
Patent Information
- Application Number
- CN202511773972.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-28
- Publication Date
- 2026-01-23
AI Technical Summary
In existing technologies, silicon as a negative electrode material in lithium-ion batteries has problems such as large volume expansion, poor conductivity and unstable SEI. In addition, common preparation methods have shortcomings such as long reaction cycles, high costs, high energy consumption and waste liquid generation, making it difficult to apply on a large scale.
The vacuum thermal reduction method utilizes silicon-containing biomass as a precursor to convert silicon dioxide in situ into elemental silicon under high temperature and vacuum conditions, forming a tight composite structure with the carbon skeleton. This avoids the need for additional reducing agents and solution systems, and achieves rapid reaction through thermodynamic drive.
A silicon-carbon composite material with a uniform microstructure was prepared, which improved the material's conductivity and cycle stability, reduced production costs and environmental friendliness, and increased preparation efficiency.
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Figure CN121377031A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of battery materials, and particularly relates to a preparation method of silicon-carbon composite material by vacuum thermal reduction. BACKGROUND
[0002] Due to the rise of the electronic product industry, people's demand for electronic equipment and energy storage is increasing, and lithium ion batteries (LIBs) play an important role in the energy storage field due to their high energy density and excellent cycle life. The traditional graphite negative electrode capacity is only 372 mAh g -1 , which has been difficult to meet the development needs of high energy density batteries. Silicon, as a representative of the next generation of negative electrode materials, has a theoretical specific capacity of 4200 mAh g -1 and abundant resource reserves, and is considered to be one of the most potential negative electrode materials. However, silicon has problems such as large volume expansion (more than 300%) during charging and discharging, poor conductivity, and unstable solid electrolyte interface (SEI), which leads to low cycle stability and low initial coulombic efficiency, and seriously restricts the actual application.
[0003] To solve the above problems, researchers generally use silicon-carbon composite strategy to improve the conductivity, buffer volume change, and stabilize the interface structure by introducing carbon materials. However, the current common methods such as hydrothermal, sol-gel or chemical vapor deposition have the disadvantages of long reaction period, high cost, high energy consumption, waste liquid generation, and low utilization rate, which are not conducive to large-scale application.
[0004] In recent years, silicon-containing biomass (such as rice husk) as a precursor of silicon-carbon composite material is an effective way to turn waste into treasure. This kind of material naturally contains abundant silicon dioxide and carbon source, which can be directly converted into silicon-carbon composite after high temperature treatment, and has the advantages of green environmental protection and low cost. However, how to efficiently and controllably reduce the silicon dioxide in the biomass to high-activity silicon while maintaining the stability of the carbon skeleton structure is still a key technical problem to be solved. SUMMARY
[0005] The purpose of the present application is to solve the problems existing in the prior art, and a preparation method of silicon-carbon composite material by vacuum thermal reduction is proposed. The method does not need additional reducing agent and solution system, avoids waste liquid generation, and is more green and environmentally friendly. At the same time, the reaction process is completed by relying on thermodynamics, and the reduction can be achieved within a few hours to obtain silicon-carbon composite material with uniform microstructure, greatly improving the material preparation efficiency.
[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:
[0007] A preparation method of silicon-carbon composite material by vacuum thermal reduction, comprising the following steps:
[0008] S1: The silicon-containing biomass is washed with deionized water, drained, and placed in a forced air dryer to remove surface moisture; the intact silicon-containing biomass is crushed using a cell wall crusher to obtain a silicon-containing biomass powder; the powder is etched with hydrochloric acid at room temperature to remove metal impurities, and washed with deionized water by centrifugation until the pH is 7; finally, the silicon-containing biomass precursor without impurities is obtained by drying in a forced air dryer;
[0009] S2: The silicon-containing biomass precursor obtained in S1 is calcined in an inert atmosphere in a high-temperature furnace to obtain carbonized silicon-containing biomass;
[0010] S3: The carbonized silicon-containing biomass and the reducing agent in S2 are placed in two porcelain boats in a certain mass ratio, the two porcelain boats are placed in a high-temperature furnace, sealed, vacuumed, heated to a certain temperature, and calcined for a period of time, then the porcelain boats are taken out after cooling to room temperature;
[0011] S4: The calcined powder in S3 is placed in a ball mill tank filled with inert gas, and a planetary ball mill is used to prepare a silicon-carbon composite material.
[0012] Preferably, in step S1, the silicon-containing biomass includes but is not limited to any one of rice husk, bamboo, sugarcane, diatom, reed, tea leaves, and mixtures thereof; the concentration of hydrochloric acid used is 0.1-6 mmol / L.
[0013] Preferably, in step S2, the calcination conditions of the high-temperature furnace are as follows: the inert gas flow rate is controlled at 15-22 sccm, the temperature is raised to 200-1000°C at a rate of 5°C / min, and the temperature is maintained for 2-12 h before being taken out after cooling to room temperature.
[0014] Preferably, in step S3, the reducing agent used includes but is not limited to aluminum powder, magnesium powder, CaH2, etc.
[0015] Preferably, in step S3, the ratio of carbonized silicon-containing biomass to reducing agent is 10:1-1:10; the calcination conditions of the double-temperature-zone furnace are as follows: the argon flow rate is controlled at 15-22 sccm, the temperature of thermal reduction is controlled at 600-1300°C, and the temperature is maintained for 2-12 h.
[0016] Preferably, in step S3, the vacuum degree is required to be 0.1-10 4 Pa.
[0017] Preferably, in step S4, the ball-to-material ratio is 10:1-50:1, the ball milling time is 6-16 h, and the ball milling speed is 200-800 rpm.
[0018] By adopting the technical scheme, the preparation method is based on the Ellingham principle and is used for efficiently preparing the silicon-carbon composite material. Because the free energy of formation of metal oxides such as aluminum, magnesium and calcium is much lower than that of SiO2 in the Ellingham diagram, SiO2 can be spontaneously reduced to generate Si in thermodynamics. Meanwhile, the oxygen partial pressure is significantly reduced in the vacuum environment, and the secondary oxidation of the newly generated Si is avoided, so that the reaction is ensured to be unidirectional. Compared with the conventional hydrothermal or chemical reduction method, the method does not need additional reducing agent and solution system, avoids the generation of waste liquid, and is more green and environmentally friendly. Meanwhile, the reaction process is completed by relying on thermodynamics, and the silicon-carbon composite material with uniform microstructure can be obtained within a few hours, so that the material preparation efficiency is greatly improved.
[0019] The present application has the following beneficial effects:
[0020] The method of the present application uses silicon-containing biomass as a precursor, and in-situ converts silicon dioxide in the silicon-containing biomass into silicon by means of a thermal reduction reaction under vacuum and high temperature conditions, and forms a close composite structure with the carbon skeleton. The method not only makes full use of the porous skeleton advantage of biomass carbon to provide a buffer space for lithium ion transmission and volume expansion, but also effectively improves the uniform dispersion of silicon to avoid particle agglomeration. At the same time, the vacuum environment suppresses the side reaction and secondary oxidation of silicon, ensuring high purity and high activity of the material. The silicon-carbon composite material obtained ultimately has high specific capacity of silicon and conductivity and stability of carbon, and exhibits high capacity and good cycle stability in the application of lithium ion battery anodes. BRIEF DESCRIPTION OF DRAWINGS
[0021] Figure 1 The figure is a structural schematic diagram of the device in the present application;
[0022] Figure 2 The figure is an XRD diagram of the silicon-carbon composite material in Example 1 of the present application;
[0023] Figure 3 The figure is an SEM diagram of the silicon-carbon composite material in Example 1 of the present application;
[0024] Figure 4 The figure is a charge-discharge curve diagram of the silicon-carbon composite material in Example 1 of the present application;
[0025] Figure 5 The figure is a cycle diagram of the silicon-carbon composite material in Example 1 of the present application. DETAILED DESCRIPTION
[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application.
[0027] The raw materials and reagents used in the embodiments of the present application are all conventional chemical products and can be purchased through commercial channels.
[0028] Embodiment 1
[0029] A preparation method of a silicon-carbon composite material by a vacuum thermal reduction method, specifically comprising the following steps:
[0030] S1: The rice husk is cleaned with deionized water, drained of water, and placed in a forced air drying machine to completely remove surface moisture. The intact rice husk is crushed with a cell wall crusher to obtain rice husk powder. 1g of the powder is etched with 40mL of 2M HCl at room temperature for 12h to remove metal impurities, and washed with deionized water by centrifugation until the pH is 7. Finally, it is dried in a forced air drying machine to obtain an impurity-free rice husk precursor.
[0031] S2: The rice husk precursor obtained in S1 is placed in a high-temperature furnace under an Ar atmosphere, heated to 600℃ at a rate of 5℃ / min, and held for 2h to obtain carbonized rice husk.
[0032] S3: The carbonized rice husk and aluminum powder in S2 are placed in two porcelain boats in a mass ratio of 1:1, the two porcelain boats are placed in a double-temperature-zone tube furnace, vacuum sealed (0.5Pa), and the heating rate is set to 5℃ / min. The carbonized rice husk side is heated to 600℃ and held for 4h, and the aluminum powder side is heated to 800℃ and held for 4h. After cooling to room temperature, the porcelain boats are taken out.
[0033] S4: The calcined powder in S3 is placed in a ball mill tank filled with Ar gas, and ball milled with a planetary ball mill at a ball-to-material ratio of 30:1 and a rotation speed of 600rpm for 8h to obtain a silicon-carbon composite material.
[0034] Embodiment 2
[0035] A preparation method of a silicon-carbon composite material by a vacuum thermal reduction method, specifically comprising the following steps:
[0036] S1: The rice husk is cleaned with deionized water, drained of water, and placed in a forced air drying machine to completely remove surface moisture. The intact rice husk is crushed with a cell wall crusher to obtain rice husk powder. 1g of the powder is etched with 40mL of 2M HCl at room temperature for 12h to remove metal impurities, and washed with deionized water by centrifugation until the pH is 7. Finally, it is dried in a forced air drying machine to obtain an impurity-free rice husk precursor.
[0037] S2: The rice husk precursor obtained in S1 is placed in a high-temperature furnace under an Ar atmosphere, heated to 600℃ at a rate of 5℃ / min, and held for 2h to obtain carbonized rice husk.
[0038] S3: The carbonized rice husk and CaH2 in S2 were put into two porcelain boats respectively with a mass ratio of 1:1, and the two porcelain boats were put into a high-temperature furnace, sealed and vacuumized (0.5 Pa), and the temperature rising rate was set to 5°C / min, and the temperature was raised to 800°C and kept for 4h.
[0039] S4: The calcined powder in S3 was put into a ball mill tank filled with Ar gas, and a planetary ball mill was used for ball milling, the ball-to-material ratio was 30:1, the rotation speed was set to 600 rpm, and the ball milling was performed for 8h to obtain a silicon-carbon composite material.
[0040] Example 3
[0041] A preparation method of a silicon-carbon composite material by vacuum thermal reduction, specifically comprising the following steps:
[0042] S1: The rice husk was cleaned with deionized water, drained, and put into a forced air dryer to completely remove the surface moisture. The intact rice husk was crushed with a cell wall crusher to obtain rice husk powder. 1g of the powder was etched with 40mL of 2M HCl at room temperature for 12h to remove metal impurities, and then washed with deionized water by centrifugation until the pH was 7. Finally, it was dried in a forced air dryer to obtain an impurity-free rice husk precursor.
[0043] S2: The rice husk precursor obtained in S1 was taken into a high-temperature furnace, and heated to 600°C at a rate of 5°C / min under Ar atmosphere, and kept for 2h to obtain carbonized rice husk.
[0044] S3: The carbonized rice husk and aluminum powder in S2 were put into two porcelain boats respectively with a mass ratio of 3:1, and the two porcelain boats were put into a double-temperature-zone tube furnace, sealed and vacuumized (0.5 Pa), and the temperature rising rate was set to 5°C / min, the carbonized rice husk side was heated to 800°C and kept for 4h; the aluminum powder side was heated to 1000°C and kept for 4h, and then the porcelain boats were taken out after cooling to room temperature.
[0045] S4: The calcined powder in S3 was put into a ball mill tank filled with Ar gas, and a planetary ball mill was used for ball milling, the ball-to-material ratio was 10:1, the rotation speed was set to 600 rpm, and the ball milling was performed for 12h to obtain a silicon-carbon composite material.
[0046] Example 4
[0047] A preparation method of a silicon-carbon composite material by vacuum thermal reduction, specifically comprising the following steps:
[0048] S1: The diatom is washed with deionized water, drained, and placed in a forced air dryer to remove surface moisture. The intact rice husk is crushed using a cell wall crusher to obtain rice husk powder. 1g of diatom powder is etched with 40mL of 2M HCl at room temperature for 12h, and the metal impurities are removed. Centrifugal washing is performed with deionized water until the pH is 7. Finally, it is dried in a forced air dryer to obtain impurity-free rice husk precursor.
[0049] S2: The diatom precursor obtained in S1 is placed in a high-temperature furnace under an Ar atmosphere, heated to 600℃ at a rate of 5℃ / min, and held for 2h to obtain silicon carbide diatom.
[0050] S3: The carbonized diatom in S2 and magnesium powder are placed in two porcelain boats in a mass ratio of 1:1, and the two porcelain boats are placed in a high-temperature furnace, sealed, vacuumed (0.5Pa), and set to a heating rate of 5℃ / min, and heated to 1000℃, and held for 4h.
[0051] S4: The calcined powder in S3 is placed in a ball mill tank filled with Ar gas, and a planetary ball mill is used for ball milling at a ball-to-material ratio of 30:1 and a rotation speed of 600rpm for 8h to prepare a silicon-carbon composite material.
[0052] Figure 1 The entire experimental device diagram. To ensure that the vacuum tube furnace is in a water-free and oxygen-free vacuum environment, the tube furnace needs to be evacuated at least three times, and after each evacuation, argon is introduced and vacuumed again. Figure 2 The XRD pattern of Example 1. The figure fully proves that the method can reduce silicon dioxide to elemental silicon, and the corresponding XRD card is PDF#27-1402. Figure 3 The SEM image of the silicon-carbon composite material prepared in Example 1. The morphology of the material can be directly observed in the figure, which is uniform and fine particles. Figure 4 The charge-discharge curve of the silicon-carbon composite material in Example 1. The first discharge capacity of the material can reach 821.6 mAhg -1 , and the first coulombic efficiency is 56.5%. Figure 5 The cycle curve of the silicon-carbon composite material in Example 1. The material has stable cycle performance, and the capacity retention rate is 86.9%.
[0053] In summary, the method of the present application uses silicon-containing biomass as a precursor, and through a thermal reduction reaction under vacuum and high temperature conditions, the silicon dioxide in the silicon-containing biomass is converted to elemental silicon in situ, and a tight composite structure is formed with the carbon skeleton, and the process is simple and controllable.
[0054] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.
Claims
1. A method for preparing silicon-carbon composite material by vacuum thermal reduction, comprising the following steps: S1: Wash the silicon-containing biomass with deionized water, drain the water, and put it into a blower dryer to completely remove surface moisture; use a high-speed blender to crush the whole silicon-containing biomass to obtain silicon-containing biomass powder; use hydrochloric acid to etch away metal impurities at room temperature, wash the powder with deionized water by centrifugation until the pH is 7; finally, put it into a blower dryer to dry and obtain a silicon-containing biomass precursor without impurities; S2: Take the silicon-containing biomass precursor obtained in S1 and calcine it in a high-temperature furnace under an inert atmosphere to obtain carbonized silicon-containing biomass. S3: The carbonized silicon-containing biomass and reducing agent in S2 are placed into two ceramic boats in a certain mass ratio. The two ceramic boats are placed into a high-temperature furnace, sealed, and then vacuumed. They are heated to a certain temperature and fired for a period of time. Then, after cooling to room temperature, the ceramic boats are taken out. S4: The calcined powder from S3 is placed in a ball mill jar filled with inert gas and ball-milled using a planetary ball mill to prepare a silicon-carbon composite material.
2. The method for preparing a silicon-carbon composite material by vacuum thermal reduction according to claim 1, characterized in that, In step S1, the silicon-containing biomass includes any one of rice husks, bamboo, sugarcane, diatoms, reeds, tea leaves, and mixtures thereof; the concentration of hydrochloric acid used is 0.1-6 mmol / L.
3. The method for preparing a silicon-carbon composite material by vacuum thermal reduction according to claim 1, characterized in that, In step S2, the calcination conditions in the high-temperature furnace are as follows: the inert gas flow rate is controlled at 15 sccm-22 sccm, the temperature is increased to 200-1000℃ at a heating rate of 5℃ / min, held at that temperature for 2h-12h, and then removed after cooling to room temperature.
4. The method for preparing a silicon-carbon composite material by vacuum thermal reduction according to claim 1, characterized in that, In step S3, the reducing agents used include aluminum powder, magnesium powder, and CaH2.
5. The method for preparing a silicon-carbon composite material by vacuum thermal reduction according to claim 1, characterized in that, In step S3, the ratio of carbonized silicon-containing biomass to reducing agent is 10:1 to 1:10; the calcination conditions of the dual-temperature zone furnace are: argon flow rate controlled at 15 sccm-22 sccm, thermal reduction temperature controlled at 600-1300℃, and holding at the temperature for 2h-12h.
6. The method for preparing a silicon-carbon composite material by vacuum thermal reduction according to claim 1, characterized in that, In step S3, the required vacuum level is 0.1-10. 4 Pa.
7. The method for preparing a silicon-carbon composite material by vacuum thermal reduction according to claim 1, characterized in that, In step S4, the ball-to-material ratio is 10:1-50:1, the ball milling time is 6-16 h, and the ball milling speed is 200-800 rpm.