Preparation method of graphene / silicon-carbon composite negative electrode material
Carbon-coated silicon materials were constructed by hydrothermal method and magnesothermic reduction reaction, and then combined with graphene to solve the problems of volume expansion and agglomeration of silicon-based anode materials, thereby improving the conductivity and cycle stability of the materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2025-12-29
- Publication Date
- 2026-05-26
AI Technical Summary
Existing silicon-based anode materials suffer from structural pulverization and rapid capacity decay due to massive volume expansion during cycling. Traditional composite methods also suffer from uneven carbon layer coating, easy agglomeration of silicon particles, and insufficient conductive network and mechanical stability of the material.
A carbon-coated silicon dioxide precursor was constructed using a hydrothermal method, which was then combined with a magnesothermic reduction reaction to form a carbon-coated silicon material. This material was then combined with graphene through a secondary hydrothermal process to form a multi-level graphene/silicon-carbon composite anode material.
This achieved uniform carbon coating and stable distribution of silicon particles, enhancing the material's conductivity and cycle stability, buffering volume expansion, and improving the overall performance of the material.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery anode material technology, specifically to a method for preparing a graphene / silicon-carbon composite anode material. Background Technology
[0002] With the widespread application of lithium-ion batteries in electric vehicles, portable electronic devices, and large-scale energy storage systems, the market demands increasingly higher energy density, cycle life, and safety performance. As a core component of batteries, the performance of the anode material directly impacts the overall battery performance. Silicon, due to its extremely high theoretical specific capacity (approximately 4200 mAh / g), suitable lithium intercalation potential, and abundant reserves, is considered one of the most promising anode materials for next-generation high-energy-density lithium-ion batteries. However, silicon undergoes dramatic volume expansion and contraction (up to 300% or more) during charge and discharge, leading to active material pulverization, repeated rupture and reconstruction of the solid electrolyte interface film, and electrical contact failure, resulting in rapid capacity decay and poor cycle stability. Furthermore, silicon's inherently poor conductivity limits its rate performance.
[0003] To overcome these shortcomings, researchers typically address the issue through structural design and composite modification. Constructing carbon-coated silicon structures is an effective strategy, as the carbon layer can improve the material's conductivity and, to some extent, buffer volume changes and inhibit particle aggregation. However, the mechanical strength of a single carbon layer is limited, and it may still crack during long-term cycling; simultaneously, silicon particles are prone to agglomeration and growth at high temperatures during fabrication, weakening the protective effect of the carbon layer.
[0004] In recent years, combining silicon-carbon composites with two-dimensional conductive networks (such as graphene) to construct multi-level coating structures has become a research hotspot for further improving the performance of silicon-based anodes. Graphene, with its excellent conductivity, high mechanical strength, and flexibility, can provide a stable conductive network and volume expansion space for silicon particles. However, achieving a uniform and robust composite of graphene and silicon-carbon core-shell structures, and precisely controlling the size and distribution of silicon nanoparticles, remains a technical challenge in preparing high-performance composite anode materials. Existing methods often suffer from complex processes, easy agglomeration of silicon particles, and uneven or weak bonding of coating layers. Therefore, developing a controllable preparation method that effectively restricts silicon particle growth and achieves synergistic coating of multiple carbon layers is of great significance for promoting the practical application of silicon-based anode materials. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing graphene / silicon-carbon composite anode materials, in order to solve the problems of structural pulverization and rapid capacity decay caused by huge volume expansion during cycling of existing silicon-based anode materials, as well as uneven carbon layer coating, easy agglomeration of silicon particles, and insufficient overall conductive network and mechanical stability of materials in traditional composite methods.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a graphene / silicon-carbon composite anode material includes the following steps: S1. Add carbon source and ammonia to deionized water and stir until dissolved. Then add silicon source and continue stirring to obtain a mixed solution. Place the mixed solution in a reaction vessel for hydrothermal reaction. Wash and dry the obtained product to obtain carbon-coated silica precursor. S2. The carbon-coated silicon dioxide precursor, magnesium powder and sodium chloride are mixed and subjected to a magnesium thermal reduction reaction. After the reaction is completed, the reaction product is acid-washed, washed and dried in sequence to obtain carbon-coated silicon material. S3. Add graphene oxide to deionized water, disperse it by ultrasound, add the carbon-coated silicon material and polyvinylpyrrolidone and stir evenly. Then place the resulting mixed solution in a reaction vessel for hydrothermal reaction. After the reaction is completed, filter the solution and wash the product with deionized water. Then freeze-dry the product to obtain powder. Finally, calcine the powder to obtain graphene / silicon-carbon composite anode material.
[0007] Further, in step S1, the carbon source is one or more of glucose, sucrose, and fructose, and the silicon source is one or more of tetraethyl orthosilicate, methyl orthosilicate, and n-octyltriethoxysilane.
[0008] Furthermore, in step S1, the temperature of the hydrothermal reaction is 150~200℃, and the reaction time is 6~12h.
[0009] Furthermore, in step S2, the mass ratio of the carbon-coated silica precursor, magnesium powder, and sodium chloride is 1:1:(10~20).
[0010] Further, in step S2, the magnesium thermal reduction reaction is carried out under a protective atmosphere, with a heating rate of 1~10℃ / min, a target temperature of 600~800℃, and a holding time of 6~12h; the protective atmosphere is a mixture of argon and hydrogen.
[0011] Furthermore, in step S3, the temperature of the hydrothermal reaction is 150~180℃, and the reaction time is 10~12h.
[0012] Furthermore, in step S3, the calcination is carried out under an argon atmosphere, with a heating rate of 1~10℃ / min, a target temperature of 600~800℃, and a holding time of 3~6h.
[0013] The present invention has the following beneficial effects: 1. This invention constructs a carbon-coated silicon dioxide precursor under hydrothermal conditions, achieving uniform coating of the carbon layer on the surface of the silicon source. Subsequently, the silicon dioxide is converted into silicon by the magnesothermic reduction method. At the same time, sodium chloride is used to effectively inhibit the agglomeration and excessive growth of silicon particles, so that the carbon-coated silicon material has both complete carbon shell protection and suitable silicon core size.
[0014] 2. This invention combines graphene with carbon-coated silicon through a secondary hydrothermal process, followed by calcination to form a conductive graphene network. This multi-level structure not only enhances the overall conductivity of the electrode material, but also the flexible coating of graphene and the synergistic effect of the internal carbon layers effectively buffer the volume expansion of silicon during charging and discharging, thereby significantly improving the cycle stability and structural integrity of the material. Detailed Implementation
[0015] The present invention will be further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0016] Example 1: S1. Add 2g of glucose and 1.5mL of ammonia to 20mL of deionized water and stir until dissolved. Then add 1mL of tetraethyl orthosilicate and continue stirring to obtain a mixed solution. Transfer the solution to a reaction vessel and hydrothermally react at 160℃ for 12h. After the reaction is complete, centrifuge and wash the product, and then dry it in a 60℃ oven for 12h to obtain a carbon-coated silica precursor.
[0017] S2. Mix and grind 0.5g of carbon-coated silica precursor, 0.5g of magnesium powder and 5g of sodium chloride evenly. Then place the mixture in a tube furnace and heat it to 650℃ at 2℃ / min under an argon-hydrogen mixed atmosphere, and keep it at that temperature for 10h. After the reaction is completed, add the reaction product to 1mol / L hydrochloric acid and stir for 4h to remove byproducts. Then centrifuge and wash with anhydrous ethanol and dry in an oven at 80℃ for 12h to obtain carbon-coated silicon material.
[0018] S3. Graphene oxide is added to deionized water and dispersed by ultrasonication. Then, the carbon-coated silicon material and polyvinylpyrrolidone are added and stirred evenly. The resulting mixed solution is then placed in a reaction vessel and hydrothermally reacted at 180°C for 12 hours. After the reaction is completed, the product is centrifuged and washed, and then freeze-dried to obtain powder. The powder is then transferred to a tube furnace and heated to 650°C at 2°C / min under an argon atmosphere and held for 5 hours. After naturally cooling to room temperature, the graphene / silicon-carbon composite anode material is obtained.
[0019] Example 2: S1. Add 2g of glucose and 1.5mL of ammonia to 20mL of deionized water and stir until dissolved. Then add 1mL of tetraethyl orthosilicate and continue stirring to obtain a mixed solution. Transfer the solution to a reaction vessel and hydrothermally react at 160℃ for 12h. After the reaction is complete, centrifuge and wash the product, and then dry it in a 60℃ oven for 12h to obtain a carbon-coated silica precursor.
[0020] S2. Mix and grind 0.5g of carbon-coated silica precursor, 0.5g of magnesium powder and 5g of sodium chloride evenly. Then place the mixture in a tube furnace and heat it to 700℃ at 2℃ / min under an argon-hydrogen mixed atmosphere, and keep it at that temperature for 10h. After the reaction is completed, add the reaction product to 1mol / L hydrochloric acid and stir for 4h to remove byproducts. Then centrifuge and wash with anhydrous ethanol and dry in an oven at 80℃ for 12h to obtain carbon-coated silicon material.
[0021] S3. Graphene oxide is added to deionized water and dispersed by ultrasonication. Then, the carbon-coated silicon material and polyvinylpyrrolidone are added and stirred evenly. The resulting mixed solution is then placed in a reaction vessel and hydrothermally reacted at 180°C for 12 hours. After the reaction is completed, the product is centrifuged and washed, and then freeze-dried to obtain powder. The powder is then transferred to a tube furnace and heated to 650°C at 2°C / min under an argon atmosphere and held for 5 hours. After naturally cooling to room temperature, the graphene / silicon-carbon composite anode material is obtained.
[0022] Comparative example: To investigate the role of the final graphene composite step, this comparative example only proceeded to magnesothermic reduction to prepare a control sample that did not include the graphene composite step.
[0023] S1. Add 2g of glucose and 1.5mL of ammonia to 20mL of deionized water and stir until dissolved. Then add 1mL of tetraethyl orthosilicate and continue stirring to obtain a mixed solution. Transfer the solution to a reaction vessel and hydrothermally react at 160℃ for 12h. After the reaction is complete, centrifuge and wash the product, and then dry it in an oven at 60℃ for 12h to obtain a carbon-coated silica precursor. S2. Mix 0.5g of carbon-coated silica precursor, 0.5g of magnesium powder and 5g of sodium chloride and grind them evenly. Then, put the mixture into a tube furnace, introduce an argon-hydrogen mixture, and heat it to 650℃ at a rate of 2℃ / min and hold it at that temperature for 10h. After the reaction is completed, add the reaction product to 1mol / L hydrochloric acid and stir for 4h to remove byproducts. Then, centrifuge and wash with anhydrous ethanol and dry in an oven at 80℃ for 12h to obtain carbon-coated silicon material.
[0024] The silicon-carbon composite materials prepared in the examples and comparative examples were used as negative electrode materials for lithium-ion batteries. Constant current charge-discharge was performed in half-cells, and the performance of each sample was compared at a current density of 0.1 A / g: Table 1
[0025] The above-described embodiments are preferred embodiments of the present invention and are only used to facilitate the illustration of the present invention. They are not intended to limit the present invention in any way. Any person skilled in the art who makes local modifications or alterations to the technical content disclosed in the present invention without departing from the scope of the technical features of the present invention shall still fall within the scope of the technical features of the present invention.
Claims
1. A method for preparing a graphene / silicon-carbon composite anode material, characterized in that, Includes the following steps: S1. Add carbon source and ammonia to deionized water and stir until dissolved. Then add silicon source and continue stirring to obtain a mixed solution. Place the mixed solution in a reaction vessel for hydrothermal reaction. Wash and dry the obtained product to obtain carbon-coated silica precursor. S2. The carbon-coated silicon dioxide precursor, magnesium powder and sodium chloride are mixed and subjected to a magnesium thermal reduction reaction. After the reaction is completed, the reaction product is acid-washed, washed and dried in sequence to obtain carbon-coated silicon material. S3. Add graphene oxide to deionized water, disperse it by ultrasound, add the carbon-coated silicon material and polyvinylpyrrolidone and stir evenly. Then place the resulting mixed solution in a reaction vessel for hydrothermal reaction. After the reaction is completed, filter the solution and wash the product with deionized water. Then freeze-dry the product to obtain powder. Finally, calcine the powder to obtain graphene / silicon-carbon composite anode material.
2. The preparation method according to claim 1, characterized in that, In step S1, the carbon source is one or more of glucose, sucrose, and fructose; the silicon source is one or more of tetraethyl orthosilicate, methyl orthosilicate, and n-octyltriethoxysilane.
3. The preparation method according to claim 1, characterized in that, In step S1, the temperature of the hydrothermal reaction is 150~200℃, and the reaction time is 6~12h.
4. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of the carbon-coated silica precursor, magnesium powder, and sodium chloride is 1:1:(10~20).
5. The preparation method according to claim 1, characterized in that, In step S2, the magnesothermic reduction reaction is carried out under a protective atmosphere, with a heating rate of 1~10℃ / min, a target temperature of 600~800℃, and a holding time of 6~12h; the protective atmosphere is a mixture of argon and hydrogen.
6. The preparation method according to claim 1, characterized in that, In step S3, the temperature of the hydrothermal reaction is 150~180℃, and the reaction time is 10~12h.
7. The preparation method according to claim 1, characterized in that, In step S3, the calcination is carried out under an argon atmosphere, with a heating rate of 1~10℃ / min, a target temperature of 600~800℃, and a holding time of 3~6h.