Silicon-carbon negative electrode material, preparation method thereof and battery
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 安徽得壹能源科技有限公司
- Filing Date
- 2025-01-03
- Publication Date
- 2026-06-23
AI Technical Summary
Silicon materials are prone to volume expansion during lithium ion insertion/extraction, leading to capacity decay and poor cycle performance.
A step-by-step method was used to prepare silicon-carbon anode materials, including depositing a nano-silicon layer and a carbon coating layer on a porous carbon substrate and forming a passivation layer on the surface. By adjusting the deposition parameters, the morphology of silicon and the coating effect of carbon were optimized, and a three-dimensional porous structure was constructed to buffer volume expansion and improve conductivity.
This improves the conductivity and structural stability of the material, reduces direct contact between silicon and the electrolyte, and decreases the occurrence of side reactions, thereby enhancing the battery's performance and cycle stability.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrode material preparation technology, specifically relating to a silicon-carbon anode material, its preparation method, and a battery. Background Technology
[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.
[0003] After half a century of development, lithium-ion batteries have seen continuous improvements in energy density, power density, and lifespan. Carbon, transition metal oxides, SnOx, tin alloys and oxides, and silicon are among the most widely studied anode materials for lithium-ion batteries. Among these materials, silicon has long been a hot topic in the research of novel high-capacity anode materials due to its superior properties, including high theoretical specific capacity, large lithium-ion storage capacity, abundant resources, and low cost. However, silicon materials are prone to volume expansion during lithium-ion insertion / extraction, leading to capacity decay and poor cycle performance.
[0004] Surface modification is often an effective strategy to alleviate the internal stress caused by silicon volume expansion. Therefore, how to effectively modify the surface of silicon-carbon materials is key to solving the above problems. Summary of the Invention
[0005] To effectively address the issue of volume expansion in silicon-carbon materials during lithium ion insertion / extraction, this invention provides a silicon-carbon anode material, its preparation method, and a battery.
[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:
[0007] In a first aspect, the present invention provides a silicon-carbon anode material, comprising a porous carbon substrate, a nano-silicon layer deposited on the surface of the porous carbon substrate, a carbon coating layer deposited on the surface of the nano-silicon layer, and a passivation layer attached to the surface of the carbon coating layer.
[0008] During the experiment, the inventors attempted to deposit gaseous silicon and carbon sources together, but encountered the following problems: First, the deposition morphology of silicon significantly affects battery capacity and lifespan. Because silicon and carbon sources are deposited together, the deposition morphology of nano-silicon is difficult to accurately adjust and optimize, thus compromising battery capacity and lifespan. Second, the carbon layer formed by the co-deposition of carbon and silicon sources is discontinuous and not dense, resulting in weak conductivity and structural stability of the negative electrode material. Furthermore, after co-depositing the carbon and silicon sources, passivation treatment was attempted on the surface of the mixed deposition layer, but it was still difficult to ensure that the passivation layer effectively isolated the internal silicon-carbon mixed deposition layer. This easily led to contact between the silicon-carbon composite deposition layer and the electrolyte, causing corrosion of the silicon-carbon composite deposition layer and affecting battery performance and lifespan.
[0009] The preparation method of this invention separates silicon deposition and carbon coating into steps, enabling precise control of both processes. By adjusting deposition parameters (such as temperature, pressure, and time), the silicon deposition morphology and carbon coating effect can be optimized, resulting in a composite material with specific structure and properties. Furthermore, the step-by-step process helps form a more uniform and dense carbon coating layer. This not only improves the material's conductivity and structural stability but also reduces direct contact between silicon and the electrolyte, minimizing side reactions and thus improving battery performance and cycle stability.
[0010] Secondly, the present invention provides a method for preparing the silicon-carbon anode material, comprising the following steps: placing the porous carbon material in an inert atmosphere, pre-treating it by heating, and removing impurities and moisture from the surface of the material;
[0011] A nano-silicon layer is vapor-deposited on the surface of a pretreated porous carbon material.
[0012] Then, a carbon coating layer is deposited on the surface of the nano-silicon layer;
[0013] The carbon coating layer is obtained by oxidizing and passivating its surface.
[0014] The prepared Si@C anode material with a three-dimensional porous surface possesses internal pore spaces that can accommodate the volume expansion of the active material, accelerating interfacial electrochemical reactions and promoting electron / ion transport. Then, a three-dimensional porous structure is constructed on the core-shell surface through further vapor deposition or a sol-gel method. This step aims to increase the specific surface area of the material, enhance the ion and electron transport rates, and buffer the volume expansion through the large and resilient three-dimensional porous structure, maintaining the integrity of the Si electrode during cycling.
[0015] Finally, an oxide passivation layer is prepared on the material surface, which can further protect the material, prevent the negative electrode material from directly contacting the electrolyte, and improve the stability of the material.
[0016] In some embodiments, the pore volume of the porous carbon material is 0.5-1 cm³. 3 / g, with an average pore size of 2-3nm and a specific surface area of 1500-2000m². 2 / g.
[0017] Preferably, the pore volume of the porous carbon material is 0.7-1 cm³. 3 / g, with an average pore size of 2-2.5nm and a specific surface area of 1700-2000m². 2 / g.
[0018] More preferably, the porous carbon material has a pore volume of 0.9 cm³. 3 / g, with an average pore size of 2.1nm and a specific surface area of 1850m². 2 / g.
[0019] In some embodiments, a nano-silicon layer is deposited using a vapor deposition method. Since the activation energy for silicon source gas to enter the pores is less than the activation energy required for deposition on the surface, silicon source gas is more easily deposited onto the porous carbon pore walls.
[0020] Preferably, the vapor-phase silicon source used in the vapor deposition method is silane or dimethylsilane.
[0021] Preferably, when vapor-phase depositing the nano-silicon layer, the deposition temperature is 500-600℃ and the deposition time is 5-10h.
[0022] In a further preferred embodiment, before introducing the silicon source gas, the process includes raising the temperature to the deposition temperature and holding it for 10 minutes to 2 hours.
[0023] In some embodiments, the carbon coating layer is prepared by vapor deposition or sol-gel method.
[0024] Preferably, when preparing the carbon coating layer using the vapor phase deposition method, the preparation environment is heated to 550-650°C in a mixed atmosphere of hydrogen and argon, and then a carbon source gas is introduced for carbon coating.
[0025] Further preferred, the carbon coating time is 3-5 hours.
[0026] Thirdly, the present invention provides a battery in which the negative electrode material on the negative electrode plate is the silicon-carbon negative electrode material.
[0027] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:
[0028] This invention constructs a three-dimensional porous structure on the surface of silicon-carbon, increasing the specific surface area of the material, improving the transport rate of ions and electrons, enhancing the conductivity and cycle stability of the material, and mitigating the volume effect of silicon.
[0029] The preparation method of this invention separates silicon deposition and carbon coating into steps, enabling precise control of both processes. By adjusting deposition parameters (such as temperature, pressure, and time), the silicon deposition morphology and carbon coating effect can be optimized, resulting in a composite material with specific structure and properties. Furthermore, the step-by-step process helps form a more uniform and dense carbon coating layer. This not only improves the material's conductivity and structural stability but also reduces direct contact between silicon and the electrolyte, minimizing side reactions and thus improving battery performance and cycle stability.
[0030] The preparation method is simple, uses low-cost raw materials, is highly operable, and is environmentally friendly, enabling lithium-ion batteries to have good rate performance and stable cycle performance. Detailed Implementation
[0031] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0032] The present invention will be further described below with reference to the embodiments.
[0033] Example 1
[0034] 1. Continuously purge nitrogen gas at a rate of 80 L / min into the reactor as a protective gas source, then add 6 kg of porous carbon (the porous carbon substrate has a pore volume of 0.9 cm³). 3 / g, with an average pore size of 2.1nm and a specific surface area of 1850m². 2 / g), heated to 550℃ at a heating rate of 5℃ / min, held for 10 min, then introduced silane gas at a flow rate of 5L / min, and held for 8 h, then cooled to room temperature.
[0035] 2. Place the silicon carbide material obtained above into a tube furnace, heat it to 600℃ at a hydrogen-argon atmosphere (volume ratio of hydrogen to argon is 5:95) at a rate of 2.5℃ / min, hold it at that temperature for 2 hours, and then introduce ethylene gas (2L / min) and hold it at that temperature for 4 hours.
[0036] 3. Cool to 300℃ and introduce a mixture of oxygen-containing gas and carrier gas into the deposition furnace. The volume fraction of oxygen in the mixture is 3%, and surface passivation treatment is performed. This step aims to form an oxide layer on the material surface to prevent the negative electrode material from directly contacting the electrolyte and improve the stability of the material.
[0037] 4. The prepared silicon-carbon anode material is subjected to post-processing steps such as washing and drying to prepare a silicon-carbon anode material with a three-dimensional porous structure on the surface.
[0038] Example 2
[0039] 1. Continuously purge the reactor with nitrogen gas at a rate of 90 L / min as a protective gas source, then add 6.5 kg of porous carbon (the porous carbon substrate has a pore volume of 0.9 cm³). 3 / g, with an average pore size of 2.1nm and a specific surface area of 1850m². 2 / g), heated to 600℃ at a heating rate of 3℃ / min, held for 10min, then introduced silane gas at a flow rate of 5L / min, and held for 8h, then cooled to room temperature.
[0040] 2. Place the silicon carbide material obtained above into a tube furnace, heat it to 600℃ at a hydrogen-argon atmosphere (volume ratio of hydrogen to argon is 5:95) at a rate of 2.5℃ / min, hold it at that temperature for 2 hours, and then introduce ethylene gas (2L / min) and hold it at that temperature for 4 hours.
[0041] 3. Cool to 250℃ and introduce a mixture of oxygen-containing gas and carrier gas into the deposition furnace. The volume concentration of oxygen in the mixture is 3%, and surface passivation treatment is performed. This step aims to form an oxide layer on the material surface to prevent direct contact between the negative electrode material and the electrolyte, thereby improving the stability of the material.
[0042] 4. The prepared silicon-carbon anode material is subjected to post-processing steps such as washing and drying to prepare a carbon-coated silicon-carbon anode material with a three-dimensional porous structure on its surface.
[0043] Example 3
[0044] 1. Continuously purge the reactor with nitrogen gas at a rate of 90 L / min as a protective gas source, then add 6.5 kg of porous carbon (the porous carbon substrate has a pore volume of 1.0 cm³). 3 / g, with an average pore size of 2.0nm and a specific surface area of 1800m². 2 / g), heated to 550℃ at a heating rate of 5℃ / min, held at this temperature for 15min, then introduced silane gas at a flow rate of 5.5L / min, and held at this temperature for another 6h, before cooling to room temperature.
[0045] 2. Place the silicon carbide material obtained above into a tube furnace, heat it to 650℃ at a hydrogen-argon atmosphere (volume ratio of hydrogen to argon is 5:95) at a rate of 2.5℃ / min, hold it at that temperature for 2 hours, and then introduce ethylene gas (2L / min) and hold it at that temperature for 4 hours.
[0046] 3. Cool to 200℃, and introduce a mixture of oxygen-containing gas and carrier gas into the deposition furnace. The volume concentration of oxygen in the mixture is 3%, for surface passivation treatment. This step aims to form an oxide layer on the material surface to prevent direct contact between the negative electrode material and the electrolyte, thereby improving the stability of the material.
[0047] 4. The prepared silicon-carbon anode material is subjected to post-processing steps such as washing and drying to prepare a silicon-carbon anode material with a three-dimensional porous structure on the surface.
[0048] Comparative Example 1
[0049] 1. Continuously purge nitrogen gas at a rate of 80 L / min into the reactor as a protective gas source, then add 6 kg of porous carbon (the porous carbon substrate has a pore volume of 0.9 cm³). 3 / g, pore size of 2.1nm, specific surface area of 1850m² 2 / g), heated to 550℃ at a heating rate of 5℃ / min, held for 10min, and then silane gas was introduced at a flow rate of 5L / min. The temperature was then maintained for 8h.
[0050] 2. Cool to 300℃ and introduce a mixture of oxygen-containing gas and carrier gas into the deposition furnace for surface passivation treatment. This step aims to form an oxide layer on the material surface to prevent direct contact between the negative electrode material and the electrolyte, thereby improving the material's stability.
[0051] 3. The prepared silicon-carbon anode material is subjected to post-processing steps such as washing and drying.
[0052] Comparative Example 2
[0053] The difference from Example 1 is that nitrogen gas at a continuous flow rate of 80 L / min is introduced into the reactor as a protective gas source, followed by the addition of 6 kg of porous carbon (the porous carbon substrate has a pore volume of 0.9 cm³). 3 / g, with an average pore size of 2.1nm and a specific surface area of 1850m². 2 / g), heated to 550℃ at a heating rate of 5℃ / min, held for 10min, and the atmosphere was replaced with hydrogen-argon (volume ratio of hydrogen to argon is 5:95). Then a mixture of silane and ethylene was introduced, with a silane flow rate of 5L / min and an ethylene flow rate of 2L / min. The mixture was held for 8h and then cooled to room temperature.
[0054] Everything else is the same as in Example 1.
[0055] Performance testing:
[0056] Batteries were prepared using the Si@C anode materials provided in Examples 1-3 and Comparative Examples 1-2. The specific steps for preparing the batteries included:
[0057] Graphite, silicon anode material, conductive agent, and binder were mixed and dissolved in a solvent at a mass ratio of 90:6:1:3, with the solid content controlled at 55%. The mixture was then coated onto a copper foil current collector and vacuum dried to produce a coin cell battery. The anode sheet, electrolyte, SK separator, lithium foil, and casing were assembled using conventional manufacturing processes. The electrolyte solvent consisted of ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1; the solute was LiPF6 with a concentration of 1 mol / L. The battery's electrical performance was tested using a battery testing system. The test conditions were: constant current charge / discharge at 0.1C at room temperature, with a charge / discharge cutoff voltage of 0.01V-1.5V. The test results are shown in Table 1.
[0058] Keeping everything else constant, we changed the charging current and tested the battery's rate retention rate. The results are shown in Table 1.
[0059] Table 1. Comparison of electrical performance of examples and comparative examples.
[0060]
[0061] As shown in Table 1, modifying the surface of silicon-carbon materials to construct a three-dimensional porous structure provides effective buffer space and transport channels for silicon particles, improving the structural stability and cycle performance of the material. Simultaneously, the uniform deposition of nano-silicon particles and the construction of the three-dimensional porous structure also increase the specific surface area and electrochemical activity of the material, thereby enhancing the energy density of the battery. This preparation method is simple, uses low-cost raw materials, is highly operable, and is environmentally friendly, enabling lithium-ion batteries to exhibit good rate performance and stable cycle performance. Furthermore, the stepwise silicon deposition and carbon coating ensure material uniformity and stability, thereby improving the battery's electrical performance and cycle stability.
[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A silicon-carbon anode material, characterized in that: It includes porous carbon materials, a nano-silicon layer deposited on the surface of the porous carbon materials, a carbon coating layer deposited on the surface of the nano-silicon layer, and a passivation layer attached to the surface of the carbon coating layer. The porous carbon material is placed in an inert atmosphere and pretreated by heating to remove impurities and moisture from the surface of the material. A nano-silicon layer is vapor-deposited on the surface of a pretreated porous carbon material. When preparing a carbon coating layer using vapor deposition, the preparation environment is heated to 550-650℃ in a mixed atmosphere of hydrogen and argon, and then a carbon source gas is introduced for carbon coating. The temperature is lowered to 200℃~300℃, and a mixture of oxygen-containing gas and carrier gas is introduced into the deposition furnace for surface passivation treatment.
2. The method for preparing the silicon-carbon anode material according to claim 1, characterized in that: The process includes the following steps: placing the porous carbon material in an inert atmosphere, heating it for pretreatment, and removing impurities and moisture from the material surface; A nano-silicon layer is vapor-deposited on the surface of a pretreated porous carbon material. Then, a carbon coating layer is deposited on the surface of the nano-silicon layer; The carbon coating layer is obtained by oxidizing and passivating its surface.
3. The method for preparing silicon-carbon anode material according to claim 2, characterized in that: The porous carbon material has a pore volume of 0.5-1 cm³. 3 / g, with an average pore size of 2-3 nm and a specific surface area of 1500-2000 m². 2 / g.
4. The method for preparing silicon-carbon anode material according to claim 2, characterized in that: The porous carbon material has a pore volume of 0.7-1 cm³. 3 / g, with an average pore size of 2-2.5 nm and a specific surface area of 1700-2000 m². 2 / g.
5. The method for preparing the silicon-carbon anode material according to claim 4, characterized in that: The porous carbon material has a pore volume of 0.9 cm³. 3 / g, with an average pore size of 2.1 nm and a specific surface area of 1850 m². 2 / g.
6. The method for preparing silicon-carbon anode material according to claim 2, characterized in that: The vapor-phase silicon source used in the vapor deposition is silane or dimethylsilane.
7. The method for preparing silicon-carbon anode material according to claim 2, characterized in that: When vapor-phase depositing nano-silicon layers, the deposition temperature is 500-600℃ and the deposition time is 5-10h.
8. The method for preparing silicon-carbon anode material according to claim 7, characterized in that: Before introducing the silicon source gas, there is also a step of raising the temperature to the deposition temperature and holding it for 10 minutes to 2 hours.
9. The method for preparing silicon-carbon anode material according to claim 2, characterized in that: Carbon coatings were prepared using vapor deposition or sol-gel methods.
10. The method for preparing silicon-carbon anode material according to claim 2, characterized in that: When preparing a carbon coating using vapor deposition, the preparation environment is heated to 550-650℃ in a mixed atmosphere of hydrogen and argon, and then a carbon source gas is introduced for carbon coating.
11. The method for preparing the silicon-carbon anode material according to claim 10, characterized in that: The carbon coating time is 3-5 hours.
12. A battery, characterized in that: The negative electrode material on the negative electrode plate of the battery is the silicon-carbon negative electrode material of claim 1 or the silicon-carbon negative electrode material prepared by any of the preparation methods of claims 2-11.