A method for preparing nano-silicon carbide and its application
By preparing nano-silicon carbide through a low-temperature reduction combined with calcination method, the problem of controlling the size and morphology of high-temperature reactions was solved, and the efficient preparation of lithium-ion battery anode materials with excellent electrochemical performance was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUZHOU XINENG CARBON SILICON TECH CO LTD
- Filing Date
- 2024-12-12
- Publication Date
- 2026-06-30
AI Technical Summary
The carbothermal reduction method for preparing nano-silicon carbide has the disadvantage of excessively high reaction temperature (above 2500℃), and the high temperature reaction makes it difficult to control the size and morphology of silicon carbide. Furthermore, the prepared nano-silicon carbide has insufficient cycle stability when used as a negative electrode material for lithium-ion batteries.
Nano-silicon carbide was prepared by a two-step method combining low-temperature reduction and calcination. Rapid low-temperature reduction was carried out using a molten salt and hydride system at 250–300 °C to generate a silicon carbide composite. Subsequently, calcination was carried out at 1200–1600 °C to prepare 3C crystalline nano-silicon carbide with uniform size and distinct angular morphology.
By significantly reducing the reaction temperature and avoiding mechanical crushing and sieving processes, the prepared nano-silicon carbide exhibits high specific capacity, good cycle stability, and excellent electrochemical performance as a negative electrode material for lithium-ion batteries.
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Figure CN119637878B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a method for preparing and applying nano-silicon carbide. Technical Background
[0002] Silicon carbide (SiC) is an inorganic compound with stable chemical properties, high thermal conductivity, low coefficient of thermal expansion, and good wear resistance. It is primarily used in the manufacture of abrasives, wear-resistant agents, grinding tools, and advanced refractory materials. It is also used in the manufacture of fine ceramics and electronic devices, particularly in third-generation semiconductor materials, where its excellent electrical properties have garnered significant attention. Furthermore, silicon carbide materials have applications in the biomedical field; due to its bioinertness, it can be used in vivo without causing adverse reactions.
[0003] Nanoscale silicon carbide, with particle sizes ranging from 50 nm to 500 nm, possesses high specific surface area and high reactivity, leading to its wide application in various fields, including semiconductor devices, optical components, biomedical materials, environmental protection, electromagnetic shielding materials, high-performance coatings, and lithium-ion battery anode materials. The preparation methods for nanoscale silicon carbide include carbothermal reduction, laser-induced gas-phase reaction synthesis, thermochemical vapor deposition (CVD), and plasma methods. The carbothermal reduction method uses quartz and petroleum coke as silicon and carbon sources, respectively, requiring heating to above 2500℃ to reduce quartz with petroleum coke. By adjusting parameters such as the type of reactants, heating method, heating temperature, and holding time, the purity and particle size of the generated nanoscale silicon carbide can be controlled. The carbothermal reduction method is suitable for large-scale production of high-purity nanoscale silicon carbide due to its low raw material cost and simple reaction requirements. However, the carbothermal reduction method for preparing nanoscale silicon carbide suffers from excessively high reaction temperatures (above 2500℃), and the high temperature reaction makes it difficult to control the size and morphology of the silicon carbide. Often, mechanical crushing and sieving are required to obtain the ideal particle size.
[0004] Molten salts, formed as a liquid state after melting at high temperatures, are widely used as reaction media in materials synthesis, surface treatment, and metal extraction. In research on the magnesian reduction of silica to prepare elemental silicon, adding AlCl3 as a molten salt to the reaction system reduced the reaction temperature from 680℃ to 250℃. AlCl3 provides a liquid environment for the magnesian reduction reaction and reacts with silica to produce SiCl4. Therefore, the molten salt reaction system can lower the reduction temperature of silica.
[0005] With the ever-increasing demand for renewable energy, secondary batteries have ushered in new opportunities in the energy revolution. Among these, the global production and manufacturing scale of lithium-ion batteries has reached unprecedented levels, simultaneously driving in-depth research into lithium-ion battery anode materials. Silicon-based anodes, with their extremely high theoretical specific capacity (3579 mAh g⁻¹), have achieved significant advancements. -1 For Si lithiation to Li 3.75 Si, 4200mAh g -1 Si lithiumization to Li 4.4 However, lithium insertion / extraction cycling causes severe volume expansion in silicon materials, making pure silicon unsuitable for use as a standalone lithium-ion battery anode material. Silicon-carbon or silicon carbide composites are increasingly being used in lithium-ion batteries due to their low cost, simple synthesis methods, ease of availability, sustainable strategies, and improved battery performance (including capacity, cycle performance, and stability / durability). Summary of the Invention
[0006] Objective: The technical problem this invention aims to solve is the issue of excessively high reaction temperatures (above 2500℃) in the preparation of nano-silicon carbide via carbothermal reduction, which makes it difficult to control the size and morphology of the silicon carbide. Often, mechanical crushing and sieving are required to obtain the desired particle size. The prepared nano-silicon carbide, as a negative electrode for lithium-ion batteries, improves the cycle stability of lithium-ion batteries.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0008] A method for preparing nano-silicon carbide material includes the following steps:
[0009] (1) After mixing silicon-containing compounds, hydrides, molten salts and petroleum-based hydrocarbons, the mixture is added to a reaction vessel and heated in an argon atmosphere; the product obtained by the low-temperature thermal reduction reaction is washed, filtered and dried to obtain brown particles.
[0010] (2) The brown particles obtained in step (1) are calcined in an argon atmosphere, and the product is dried and simply ground to obtain the final product.
[0011] Specifically, in step (1), the selected silicon-containing compound is one of silicon dioxide, rice husk silica, methyl silicone oil, and water glass.
[0012] Specifically, in step (1), the molten salt is one or a combination of aluminum chloride, potassium chloride, calcium chloride or sodium chloride.
[0013] Specifically, in step (1), the hydride is one or a combination of sodium hydride, calcium hydride, magnesium hydride, and lithium hydride.
[0014] Specifically, in step (1), the petroleum-based hydrocarbon is one of pitch coke, coal pitch, coal tar, and paraffin.
[0015] Specifically, in step (1), the selected molten salt can be one or a combination of aluminum chloride, potassium chloride, calcium chloride, or sodium chloride. The mass ratio of nano-silica, hydride, molten salt, and petroleum-based hydrocarbon is in the range of 1:(1-4):(15-20):(1-4). The reaction is carried out in an argon atmosphere at a temperature of 250-300°C for 0.5-1 hour, with a holding time of 1-4 hours. The washing and drying process involves washing three times with distilled water and vacuum drying at 60°C for 1 hour.
[0016] Specifically, in step (2), under an argon atmosphere, the temperature is increased to 1200-1600℃ at a heating rate of 5-10℃ / min and held for 1-4 hours, and then cooled to room temperature at a cooling rate of 5-10℃ / min.
[0017] Specifically, in step (2), the powder is simply ground by hand and sieved to a particle size of less than 200 mesh.
[0018] Furthermore, the nano-silicon carbide prepared by the above preparation method is also within the scope of protection of this invention.
[0019] Furthermore, this invention also claims protection for the application of the above-prepared nano-silicon carbide as a negative electrode material for lithium-ion batteries.
[0020] Furthermore, the present invention also claims a lithium-ion battery whose negative electrode material is prepared using the nano-silicon carbide prepared as described above.
[0021] Beneficial effects:
[0022] (1) This invention prepares nano-silicon carbide through a two-step method combining low-temperature reduction and calcination. A system of molten salt and hydrides is used to achieve rapid low-temperature reduction of silicon-containing compounds (reaction temperature below 300℃, reaction time 0.5–1 hour), and to generate a carbon-silicon complex with petroleum-based hydrocarbons. Nano-silicon carbide is then generated by calcination at a lower temperature (1200–1600℃). This significantly reduces the reaction temperature compared to carbothermal reduction.
[0023] (2) The present invention prepares 3C crystalline nano silicon carbide by a two-step method of low-temperature reduction combined with calcination. The morphology is uniform, consisting of particles with obvious edges and corners, with a size of 10-20 nm. The size is uniform, avoiding the complex process of controlling the morphology and particle size of the product by changing the reaction conditions, and eliminating the need for mechanical crushing and sieving.
[0024] (3) The product of this invention, as a negative electrode material for lithium-ion batteries, has a high reversible specific capacity, good cycle stability, and excellent electrochemical performance. Attached Figure Description
[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.
[0026] Figure 1 The image shows a transmission electron microscope image of the lithium-ion battery anode material prepared in Example 1.
[0027] Figure 2 X-ray diffraction patterns of Examples 1 (SC-1500), 4 (SC-1200), 5 (SC-1300), 6 (SC-1400), and 7 (SC-1600).
[0028] Figure 3 The first ten cyclic voltammetry curves of the lithium-ion battery anode material prepared in Example 1 are shown.
[0029] Figure 4 Impedance diagrams of lithium-ion battery anode materials prepared in Examples 1 (SC-1500), 6 (SC-1400), and 7 (SC-1600) at frequencies of 100000 to 0.01 Hz after 50 charge-discharge cycles.
[0030] Figure 5 The charge-discharge curves of the lithium-ion battery anode material prepared in Example 1 are obtained after the first three charge-discharge cycles at a current density of 0.01 A / g.
[0031] Figure 6 The lithium-ion batteries prepared for Example 1 (SC-1500), Example 6 (SC-1400), and Example 7 (SC-1600) were subjected to three initial charge-discharge cycles at a current density of 0.01 A / g, followed by 200 cycles at a current density of 0.05 A / g.
[0032] Figure 7 The rate performance diagrams of the lithium-ion battery prepared in Example 1 at different current densities are shown. Detailed Implementation
[0033] The present invention can be better understood from the following embodiments.
[0034] Example 1
[0035] Take 2g of silicon dioxide, and add silicon dioxide, calcium hydride, aluminum chloride, and pitch coke to a reaction vessel in a mass ratio of 1:2:15:1. The reaction temperature is 250℃, the reaction time is 0.5 hours, and the holding time is 2.5 hours. Wash the reaction product three times with distilled water and dry it under vacuum at 60℃ for 1 hour. Place the dried product in a tube furnace, heat it to 1500℃ at a heating rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it to room temperature at a cooling rate of 10℃ / min. Remove the sample and grind it to obtain the negative electrode material for lithium-ion batteries. (SC-1500)
[0036] Example 2
[0037] Take 2g of silica and a molten salt mixture of 84% aluminum chloride, 10% sodium chloride, and 6% potassium chloride. Add silica, calcium hydride, molten salt, and pitch coke to a reaction vessel in a mass ratio of 1:2:15:1. The reaction temperature is 250℃, the reaction time is 0.5 hours, and the holding time is 2.5 hours. Wash the reaction product three times with distilled water and dry it under vacuum at 60℃ for 1 hour. Place the dried product in a tube furnace and heat it to 1500℃ at a heating rate of 10℃ / min, hold it at that temperature for 2 hours, and then cool it to room temperature at a cooling rate of 10℃ / min. Remove the sample and grind it to obtain the negative electrode material for lithium-ion batteries.
[0038] Example 3
[0039] Take 2g of silicon dioxide, and add silicon dioxide, sodium hydride, aluminum chloride, and pitch coke to a reaction vessel in a mass ratio of 1:4:15:1. The reaction temperature is 250℃, the reaction time is 0.5 hours, and the holding time is 2.5 hours. Wash the reaction product three times with distilled water and dry it under vacuum at 60℃ for 1 hour. Place the dried product in a tube furnace, heat it to 1500℃ at a heating rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it to room temperature at a cooling rate of 10℃ / min. Remove the sample and grind it to obtain the negative electrode material for lithium-ion batteries.
[0040] Example 4
[0041] Take 2g of rice husk silica, and add rice husk silica, sodium hydride, aluminum chloride, and coal tar to a reaction vessel in a mass ratio of 1:4:15:2. The reaction temperature is 250℃, the reaction time is 0.5 hours, and the holding time is 2.5 hours. Wash the reaction product three times with distilled water and dry it under vacuum at 60℃ for 1 hour. Place the dried product in a tube furnace and heat it to 1200℃ at a heating rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it to room temperature at a cooling rate of 10℃ / min. Remove the sample and grind it to obtain the negative electrode material for lithium-ion batteries. (SC-1200)
[0042] Example 5
[0043] Take 2g of silicon dioxide, and add silicon dioxide, magnesium hydride, aluminum chloride, and pitch coke to a reaction vessel in a mass ratio of 1:2:15:1. The reaction temperature is 250℃, the reaction time is 0.5 hours, and the holding time is 2.5 hours. Wash the reaction product three times with distilled water and dry it under vacuum at 60℃ for 1 hour. Place the dried product in a tube furnace, heat it to 1300℃ at a heating rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it to room temperature at a cooling rate of 10℃ / min. Remove the sample and grind it to obtain the negative electrode material for lithium-ion batteries. (SC-1300)
[0044] Example 6
[0045] Take 2g of dimethyl silicone oil, and add dimethyl silicone oil, sodium hydride, aluminum chloride, and paraffin wax to a reaction vessel in a mass ratio of 1:4:15:2. The reaction temperature is 250℃, the reaction time is 0.5 hours, and the holding time is 2.5 hours. Wash the reaction product three times with distilled water and dry it under vacuum at 60℃ for 1 hour. Place the dried product in a tube furnace and heat it to 1400℃ at a heating rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it to room temperature at a cooling rate of 10℃ / min. Remove the sample and grind it to obtain the negative electrode material for lithium-ion batteries. (SC-1400)
[0046] Example 7
[0047] Take 2g of silicon dioxide, and add silicon dioxide, calcium hydride, aluminum chloride, and pitch coke to a reaction vessel in a mass ratio of 1:2:20:1. The reaction temperature is 250℃, the reaction time is 0.5 hours, and the holding time is 2.5 hours. Wash the reaction product three times with distilled water and dry it under vacuum at 60℃ for 1 hour. Place the dried product in a tube furnace, heat it to 1600℃ at a heating rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it to room temperature at a cooling rate of 10℃ / min. Remove the sample and grind it to obtain the negative electrode material for lithium-ion batteries. (SC-1600)
[0048] Figure 1 Two transmission electron microscope images at different magnification scales show the lithium-ion battery anode material prepared in Example 1. Image a shows that the silicon carbide product is granular with distinct edges and a uniform size of 10–20 nm. Image b shows the magnified crystal structure; the crystal surface is smooth, and there is a clear silicon carbide lattice spacing d = 0.14 nm, proving the successful preparation of the silicon carbide material. Figure 2The X-ray diffraction patterns of Examples 1 (SC-1500), 4 (SC-1200), 5 (SC-1300), 6 (SC-1400), and 7 (SC-1600) show the silicon carbide formation process at different temperatures. The materials in Examples 1, 6, and 7 all have diffraction peaks at 35.6°, 41.5°, 60°, 71.8°, and 75.4°, corresponding to the (111), (200), (220), (311), and (222) crystal planes of silicon carbide. There is a small peak at around 34°, which is the stacking fault of silicon carbide. There are no impurity peaks in the image, which proves that high-purity silicon carbide material can be generated after 1400°. Figure 3 The figure shows the cyclic voltammetry curves of the lithium-ion battery anode material prepared in Example 1 for the first ten cycles. A significant SEI film degradation can be observed from the first to the second cycle. The two oxidation peaks appearing at approximately 0.2 and 1 V can be attributed to Li. + Extraction. Figure 4 The impedance diagrams of the lithium-ion battery anode materials prepared in Examples 1 (SC-1500), 6 (SC-1400), and 7 (SC-1600) at frequencies of 100,000 to 0.01 Hz after 50 charge-discharge cycles are shown in the figures. As can be seen from the comparison, the silicon carbide anode material prepared at 1500℃ has relatively better conductivity. Figure 5 As shown, the lithium-ion battery anode material prepared in Example 1 has a discharge capacity of 777.38 mAh / g and an initial coulombic efficiency of 35.8% at a current density of 0.01 A / g. Figure 6 The lithium-ion batteries prepared from the three materials in Example 1 (SC-1500), Example 6 (SC-1400), and Example 7 (SC-1600) were subjected to three initial charge-discharge cycles at a current density of 0.01 A / g, followed by 200 cycles at a current density of 0.05 A / g. It can be seen that the silicon carbide anode material prepared at 1500℃ has a relatively higher capacity, with a capacity retention rate of 104.59% at a current density of 0.05 A / g, showing a slight increase in capacity. Figure 7 The graph shows the rate performance of the lithium-ion battery prepared in Example 1 at different current densities. The tests at different current densities show that the material has high capacity retention and good rate performance.
[0049] This invention provides a method for preparing and applying nano-silicon carbide. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.
Claims
1. A method for producing nanosized silicon carbide, characterized by, The process includes the following steps: (1) Mixing silicon-containing compounds, hydrides, molten salts and petroleum-based hydrocarbons and adding them to a reaction vessel, heating to 250-300°C in an argon atmosphere; performing a low-temperature thermal reduction reaction for 0.5-1 hours, holding for 1-4 hours, and washing, filtering and drying the obtained product to obtain brown particles; (2) calcining the brown particles obtained in step (1) in an argon atmosphere, heating to 1200-1600°C at a heating rate of 1-10°C / min and holding for 1-4 hours, and then cooling to room temperature at a cooling rate of 5-10°C / min; the product is then dried and simply ground to obtain the final product. The petroleum-based hydrocarbon is one of pitch coke, coal pitch, coal tar, and paraffin. The prepared 3C crystalline silicon carbide nanoparticles have a size of 10–20 nm and are uniform in size; In step (1), the hydride is one or a combination of sodium hydride, calcium hydride, magnesium hydride and lithium hydride.
2. The method for preparing nano-silicon carbide according to claim 1, characterized in that, In step (1), the silicon-containing compound is one of silicon dioxide, methyl silicone oil, and water glass.
3. The method for preparing nano-silicon carbide according to claim 2, characterized in that, The silicon-containing compound is nano-silica, and the mass ratio of nano-silica, hydride, molten salt and petroleum-based hydrocarbon is in the range of 1:(1-4):(15-20):(1-4).
4. The method for preparing nano-silicon carbide according to claim 1, characterized in that, In step (1), the molten salt is one or a combination of aluminum chloride, potassium chloride, calcium chloride or sodium chloride.
5. The method for preparing nano-silicon carbide according to claim 1, characterized in that, In step (1), the washing and drying process involves washing with distilled water three times and vacuum drying at 60°C for one hour.
6. The nano-silicon carbide prepared by any one of the preparation methods of claims 1 to 5.
7. The application of the nano-silicon carbide as described in claim 6 as a negative electrode material for lithium-ion batteries.
8. A lithium-ion battery, characterized in that, Its negative electrode is prepared using the nano-silicon carbide described in claim 6.