Soft carbon and hard carbon co-coated nano-silicon negative electrode material and preparation method thereof
By using a method of co-coating nano-silicon anode materials with soft and hard carbon, the problems of pulverization and low conductivity of silicon-based anode materials during charge and discharge were solved, achieving high initial efficiency and excellent cycle stability, thus improving the overall performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANHUI QINGZHI TECH DEV CO LTD
- Filing Date
- 2025-08-29
- Publication Date
- 2026-05-12
AI Technical Summary
Existing silicon-based anode materials pulverize due to volume effects during charge and discharge, which affects their commercialization. Furthermore, nano-silicon, nano-hollow silicon, and porous silicon have problems such as small particle size, large specific surface area, and low conductivity. Single carbon coating cannot simultaneously improve the initial charge and discharge efficiency and cycle stability.
A method for preparing nano-silicon anode materials using soft and hard carbon co-coating is adopted. Through mixed modification of carboxylated pitch, graphene oxide and polyvinylpyrrolidone, soft and hard carbon precursors are formed. Combined with silicon anode materials, a network structure is formed after carbonization, which improves lithium-ion transport and pore structure, and balances first-efficiency and cycle stability.
It achieves high initial charge-discharge efficiency and excellent cycle stability, improving the overall performance of the material, especially the rate performance of lithium-ion batteries.
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery anode material technology, and in particular to a soft carbon and hard carbon co-coated nano-silicon anode material and its preparation method. Background Technology
[0002] Silicon-based anode materials possess a theoretical specific capacity of 4200 mAh / g, which is 10 times that of currently commercially available graphite anode materials. However, due to the significant volume effect (>300%) during charge and discharge, the material pulverizes, severely hindering its commercialization. Common solutions include silicon nano-sizing, hollowing, or porousization. However, nano-silicon, nano-hollow silicon, and porous silicon all suffer from small particle size, large specific surface area, and low conductivity, necessitating carbon coating to increase conductivity, adjust particle size distribution, and reduce specific surface area, thereby improving the material's electrochemical performance. Conventional carbon coating often employs single soft or hard carbon coatings. Soft carbon offers high initial efficiency but poor cycle stability, while hard carbon offers good cycle stability but relatively low initial efficiency. Therefore, it is necessary to develop novel silicon-carbon anode materials to meet the comprehensive requirements of lithium-ion battery materials for initial charge-discharge efficiency, specific capacity, and cycle performance. Summary of the Invention
[0003] Based on the technical problems existing in the background technology, the present invention proposes a soft carbon and hard carbon co-coated nano-silicon anode material and its preparation method.
[0004] This invention proposes a method for preparing a soft carbon and hard carbon co-coated nano-silicon anode material, comprising the following steps:
[0005] S1. Carboxylated asphalt is heated at 100~200℃ until it melts, glyceryl monostearate and graphene oxide are added, and the mixture is stirred thoroughly while maintaining the temperature. Then, polyvinylpyrrolidone is added and stirred thoroughly while maintaining the temperature to obtain a mixture of soft carbon and hard carbon precursors. The mass ratio of carboxylated asphalt, glyceryl monostearate, graphene oxide and polyvinylpyrrolidone is 10:0.1~0.2:0.01~0.05:1~10.
[0006] S2. Add silicon anode material to the soft carbon and hard carbon precursor mixture and stir thoroughly at 250~400°C to obtain silicon-carbon composite precursor.
[0007] S3. The silicon-carbon composite precursor is heated and carbonized, then cooled, ground, and sieved to obtain a soft carbon and hard carbon co-coated nano-silicon anode material.
[0008] This invention involves melting carboxylated asphalt, then adding graphene oxide and glyceryl monostearate for modification. The resulting modified asphalt is used as a soft carbon precursor and mixed with a specific hard carbon precursor, polyvinylpyrrolidone, as a carbon precursor to coat silicon anode materials. The mixture is then heated and carbonized to obtain a soft-carbon and hard-carbon co-coated nano-silicon anode material. On one hand, the combination of soft and hard carbon as the coating carbon layer can balance the first-efficiency performance and cycle stability of the silicon anode material. On the other hand, the carboxylated asphalt has more chemical bonds, resulting in stronger adhesion to the silicon anode and improving the stability of the coating carbon layer. Simultaneously, the carboxyl groups in the asphalt can hydrogen-bond with the amide groups in the hard carbon precursor polyvinylpyrrolidone, forming an intercalation structure with graphene oxide modification, thus achieving a synergistic effect. The use of carbonization of dual carbon sources can form a network structure, which can promote lithium-ion transport and improve the internal pore structure of the carbon layer, thereby improving the first-efficiency and rate performance. However, the carboxylation modification of asphalt makes it more prone to aggregation, and the fluidity and dispersibility become worse, which is not conducive to the uniformity and stability of the coated carbon layer. Therefore, adding an appropriate amount of glyceryl monostearate during the modification of asphalt can improve the fluidity and dispersibility of the system after the asphalt and polyvinylpyrrolidone are mixed, thereby improving the uniformity and structural stability of the coated carbon layer. It can also further improve the interfacial wettability between asphalt and silicon anode, thereby further improving the stability of the coated carbon layer. Thus, the resulting soft carbon and hard carbon co-coated nano-silicon anode material has both excellent cycle stability and high first-efficiency and excellent rate performance.
[0009] Preferably, the method for preparing the carboxylated asphalt includes: adding asphalt and succinic anhydride to a solvent, stirring until dissolved, then adding triethylamine dropwise, heating under reflux to react, removing the solvent after the reaction is complete, adding water to the reaction product, filtering, collecting the solid, washing, and drying to obtain the product.
[0010] Preferably, the ratio of asphalt, succinic anhydride and triethylamine is 1g:2~4g:3~5mL.
[0011] In this invention, the asphalt is selected from coal tar pitch, petroleum asphalt, or a combination thereof.
[0012] Preferably, in S1, after adding glyceryl monostearate and graphene oxide, the mixture is stirred at a speed of 2000~4000 r / min for 30~60 min under heat preservation.
[0013] Preferably, in step S1, after adding polyvinylpyrrolidone, the mixture is stirred at a speed of 500-2000 r / min for 10-30 min under heat preservation.
[0014] Preferably, the average molecular weight of the polyvinylpyrrolidone is 40,000 to 1,300,000.
[0015] Preferably, the mass ratio of the soft carbon and hard carbon precursor mixture to the silicon anode material is 1:0.3~2.
[0016] In this invention, the silicon anode material includes one or a combination of several of nano-silicon, nano-hollow silicon, and porous silicon.
[0017] Preferably, in step S2, the stirring speed is 1000~2000 r / min and the stirring time is 10~30 min.
[0018] Preferably, in S3, the heating and carbonization temperature is 800~1100℃, and the time is 12~24h.
[0019] In this invention, steps S1 and S2 are performed in a protective atmosphere.
[0020] In this invention, the heating and carbonization in step S3 is carried out in a protective atmosphere.
[0021] The protective atmosphere refers to an atmosphere formed by one or more of nitrogen, inert gases (such as argon).
[0022] This invention also proposes a soft carbon and hard carbon co-coated nano-silicon anode material, which is prepared by the aforementioned method.
[0023] The beneficial effects of this invention are as follows:
[0024] This invention involves melting carboxylated asphalt, then adding graphene oxide and glyceryl monostearate for modification. The resulting modified asphalt is used as a soft carbon precursor and mixed with a specific hard carbon precursor, polyvinylpyrrolidone, as a carbon precursor to coat silicon anode materials. The mixture is then heated and carbonized to obtain a soft-carbon and hard-carbon co-coated nano-silicon anode material. On one hand, the combination of soft and hard carbon as the coating carbon layer can balance the first-efficiency performance and cycle stability of the silicon anode material. On the other hand, the carboxylated asphalt has more chemical bonds, resulting in stronger adhesion to the silicon anode and improving the stability of the coating carbon layer. Simultaneously, the carboxyl groups in the asphalt can hydrogen-bond with the amide groups in the hard carbon precursor polyvinylpyrrolidone, forming an intercalation structure with graphene oxide-modified asphalt, resulting in a synergistic effect. This allows the dual carbon source to achieve optimal performance after carbonization. To form a network structure, it can promote lithium-ion transport and improve the internal pore structure of the carbon layer, thereby improving the first-efficiency and rate performance. However, after carboxylation modification of asphalt, it is more prone to aggregation, and the fluidity and dispersibility become worse, which is not conducive to the uniformity and stability of the coated carbon layer. Therefore, adding an appropriate amount of glyceryl monostearate during the modification of asphalt can improve the fluidity and dispersibility of the system after the asphalt and polyvinylpyrrolidone are mixed, thereby improving the uniformity and structural stability of the coated carbon layer. It can also further improve the interfacial wettability between asphalt and silicon anode, thereby further improving the stability of the coated carbon layer. Thus, the resulting soft carbon and hard carbon co-coated nano-silicon anode material has both excellent cycle stability, high first-efficiency and excellent rate performance, and is a silicon-carbon composite material with excellent comprehensive performance. Detailed Implementation
[0025] The technical solution of the present invention will now be described in detail through specific embodiments.
[0026] In the following examples and comparative examples, the average molecular weight of polyvinylpyrrolidone is 1,300,000, the particle size of the nano-hollow silicon is 100-200 nm, and the wall thickness is 5-30 nm.
[0027] Example 1
[0028] Preparation of carboxylated bitumen:
[0029] Add 10g of asphalt and 20g of succinic anhydride to 500mL of chloroform and stir at room temperature until dissolved. Then add 30mL of triethylamine and heat under reflux. After the reaction is complete, remove the chloroform by rotary evaporation. Add 1L of deionized water to the reaction product, filter, collect the solid, wash with deionized water, and dry at 60℃ to obtain the final product.
[0030] Preparation of soft carbon and hard carbon co-coated nano-silicon anode materials:
[0031] S1. In a nitrogen atmosphere, 10g of carboxylated asphalt was heated at 160℃ until it melted. 0.15g of glyceryl monostearate and 0.03g of graphene oxide were added. The mixture was stirred at 3000r / min for 40min while maintaining the temperature. Then, 3g of polyvinylpyrrolidone was added. The mixture was stirred at 1000r / min for 20min while maintaining the temperature to obtain a mixture of soft carbon and hard carbon precursors.
[0032] S2. Add 15g of nano-hollow silicon to the above soft carbon and hard carbon precursor mixture, and stir at 1500r / min for 20min at 300℃ in a nitrogen atmosphere to obtain silicon-carbon composite precursor.
[0033] S3. The silicon-carbon composite precursor was heated and carbonized at 1000℃ for 12 hours in a nitrogen atmosphere. After cooling, it was ground and sieved to obtain soft carbon and hard carbon co-coated nano-silicon anode material.
[0034] Example 2
[0035] Preparation of soft carbon and hard carbon co-coated nano-silicon anode materials:
[0036] S1. In a nitrogen atmosphere, 10g of carboxylated asphalt is heated at 140℃ until it melts, 0.1g of glyceryl monostearate and 0.01g of graphene oxide are added, and the mixture is stirred at 2000r / min for 30min while maintaining the temperature. Then, 1g of polyvinylpyrrolidone is added, and the mixture is stirred at 500r / min for 10min while maintaining the temperature to obtain a mixture of soft carbon and hard carbon precursors.
[0037] S2. Add 12g of nano-hollow silicon to the above soft carbon and hard carbon precursor mixture, and stir at 1000r / min for 10min at 250℃ in a nitrogen atmosphere to obtain silicon-carbon composite precursor.
[0038] S3. The silicon-carbon composite precursor was heated and carbonized at 800°C for 18 hours in a nitrogen atmosphere. After cooling, it was ground and sieved to obtain soft carbon and hard carbon co-coated nano-silicon anode material.
[0039] The preparation method of carboxylated asphalt is the same as in Example 1.
[0040] Example 3
[0041] Preparation of soft carbon and hard carbon co-coated nano-silicon anode materials:
[0042] S1. In a nitrogen atmosphere, 10g of carboxylated asphalt was heated at 180℃ until it melted. 0.2g of glyceryl monostearate and 0.05g of graphene oxide were added. The mixture was stirred at 4000r / min for 60min while maintaining the temperature. Then, 5g of polyvinylpyrrolidone was added. The mixture was stirred at 2000r / min for 30min while maintaining the temperature to obtain a mixture of soft carbon and hard carbon precursors.
[0043] S2. Add 20g of nano-hollow silicon to the above soft carbon and hard carbon precursor mixture, and stir at 2000r / min for 30min at 400℃ in a nitrogen atmosphere to obtain silicon-carbon composite precursor.
[0044] S3. The silicon-carbon composite precursor was heated and carbonized at 1100℃ for 24 hours in a nitrogen atmosphere. After cooling, it was ground and sieved to obtain soft carbon and hard carbon co-coated nano-silicon anode material.
[0045] The preparation method of carboxylated asphalt is the same as in Example 1.
[0046] Comparative Example 1
[0047] Preparation of soft carbon and hard carbon co-coated nano-silicon anode materials:
[0048] S1. In a nitrogen atmosphere, 10g of asphalt is heated at 160℃ until it melts, and then 3g of polyvinylpyrrolidone is added. The mixture is stirred at 1000r / min for 20min while maintaining the temperature to obtain a soft carbon and hard carbon precursor mixture.
[0049] S2. Add 15g of nano-hollow silicon to the above soft carbon and hard carbon precursor mixture, and stir at 1500r / min for 20min at 300℃ in a nitrogen atmosphere to obtain silicon-carbon composite precursor.
[0050] S3. The silicon-carbon composite precursor was heated and carbonized at 1000℃ for 12 hours in a nitrogen atmosphere. After cooling, it was ground and sieved to obtain soft carbon and hard carbon co-coated nano-silicon anode material.
[0051] Comparative Example 2
[0052] Preparation of soft carbon and hard carbon co-coated nano-silicon anode materials:
[0053] S1. In a nitrogen atmosphere, 10g of asphalt is heated at 160℃ until it melts, 0.15g of glyceryl monostearate and 0.03g of graphene oxide are added, and the mixture is stirred at 3000r / min for 40min while maintaining the temperature. Then, 3g of polyvinylpyrrolidone is added, and the mixture is stirred at 1000r / min for 20min while maintaining the temperature to obtain a mixture of soft carbon and hard carbon precursors.
[0054] S2. Add 15g of nano-hollow silicon to the above soft carbon and hard carbon precursor mixture, and stir at 1500r / min for 20min at 300℃ in a nitrogen atmosphere to obtain silicon-carbon composite precursor.
[0055] S3. The silicon-carbon composite precursor was heated and carbonized at 1000℃ for 12 hours in a nitrogen atmosphere. After cooling, it was ground and sieved to obtain soft carbon and hard carbon co-coated nano-silicon anode material.
[0056] Comparative Example 3
[0057] Preparation of soft carbon and hard carbon co-coated nano-silicon anode materials:
[0058] S1. In a nitrogen atmosphere, 10g of carboxylated asphalt was heated at 160℃ until it melted, 0.03g of graphene oxide was added, and the mixture was stirred at 3000r / min for 40min while maintaining the temperature. Then, 3g of polyvinylpyrrolidone was added, and the mixture was stirred at 1000r / min for 20min while maintaining the temperature to obtain a mixture of soft carbon and hard carbon precursors.
[0059] S2. Add 15g of nano-hollow silicon to the above soft carbon and hard carbon precursor mixture, and stir at 1500r / min for 20min at 300℃ in a nitrogen atmosphere to obtain silicon-carbon composite precursor.
[0060] S3. The silicon-carbon composite precursor was heated and carbonized at 1000℃ for 12 hours in a nitrogen atmosphere. After cooling, it was ground and sieved to obtain soft carbon and hard carbon co-coated nano-silicon anode material.
[0061] The preparation method of carboxylated asphalt is the same as in Example 1.
[0062] Comparative Example 4
[0063] Preparation of soft carbon and hard carbon co-coated nano-silicon anode materials:
[0064] S1. In a nitrogen atmosphere, 10g of carboxylated asphalt was heated at 160℃ until it melted, 0.15g of glyceryl monostearate was added, and the mixture was stirred at 3000r / min for 40min while maintaining the temperature. Then, 3g of polyvinylpyrrolidone was added, and the mixture was stirred at 1000r / min for 20min while maintaining the temperature to obtain a mixture of soft carbon and hard carbon precursors.
[0065] S2. Add 15g of nano-hollow silicon to the above soft carbon and hard carbon precursor mixture, and stir at 1500r / min for 20min at 300℃ in a nitrogen atmosphere to obtain silicon-carbon composite precursor.
[0066] S3. The silicon-carbon composite precursor was heated and carbonized at 1000℃ for 12 hours in a nitrogen atmosphere. After cooling, it was ground and sieved to obtain soft carbon and hard carbon co-coated nano-silicon anode material.
[0067] The preparation method of carboxylated asphalt is the same as in Example 1.
[0068] Test case
[0069] Negative electrode sheets were prepared using soft carbon and hard carbon co-coated nano-silicon negative electrode materials prepared in the examples and comparative examples, respectively. They were then assembled into lithium-ion batteries, and constant current charge-discharge tests were conducted on each group of batteries at 25°C with a voltage range of 0.005~1.5V. The test results are shown in Table 1.
[0070] The preparation methods of the negative electrode sheet and lithium-ion battery are as follows:
[0071] The negative electrode material, conductive agent (single-walled carbon nanotubes), and binder (lithium polyacrylate, PAALi) were mixed uniformly at a mass ratio of 96:0.2:3.8, and an appropriate amount of high-purity water was added to obtain the negative electrode slurry. The negative electrode slurry was coated onto copper foil and dried at 110°C for 10 hours in a vacuum drying oven. After rolling and punching, the negative electrode sheet was obtained. Using a lithium sheet as the counter electrode and lithium hexafluorophosphate electrolyte as the electrolyte, a 2025 coin cell was assembled in a glove box under an argon atmosphere. The lithium hexafluorophosphate electrolyte consisted of lithium hexafluorophosphate, organic solvent, and additive FEC (fluoroethylene carbonate), wherein the concentration of lithium hexafluorophosphate was 1 mol / L, the mass of FEC accounted for 5% of the total mass of the electrolyte, and the organic solvent consisted of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1.
[0072] Table 1
[0073] Specific capacity (mAh / g) First-time Coulomb efficiency (%) Capacity retention rate after 100 cycles (%) Example 1 1904 92.1 96.4 Example 2 1892 90.6 95.8 Example 3 1923 91.2 96.1 Comparative Example 1 1876 85.7 86.4 Comparative Example 2 1895 86.3 90.9 Comparative Example 3 1882 89.5 85.5 Comparative Example 4 1877 86.8 89.6
[0074] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for preparing a soft carbon and hard carbon co-coated nano-silicon anode material, characterized in that, Includes the following steps: S1. Carboxylated asphalt is heated at 100~200℃ until it melts, glyceryl monostearate and graphene oxide are added, and the mixture is stirred thoroughly while maintaining the temperature. Then, polyvinylpyrrolidone is added and stirred thoroughly while maintaining the temperature to obtain a mixture of soft carbon and hard carbon precursors. The mass ratio of carboxylated asphalt, glyceryl monostearate, graphene oxide and polyvinylpyrrolidone is 10:0.1~0.2:0.01~0.05:1~10. The method for preparing the carboxylated asphalt includes: adding asphalt and succinic anhydride to a solvent, stirring until dissolved, then adding triethylamine dropwise, heating under reflux to react, removing the solvent after the reaction is complete, adding water to the reaction product, filtering, collecting the solid, washing, and drying to obtain the product; S2. Add silicon anode material to the soft carbon and hard carbon precursor mixture and stir thoroughly at 250~400°C to obtain silicon-carbon composite precursor. S3. The silicon-carbon composite precursor is heated and carbonized, then cooled, ground, and sieved to obtain a soft carbon and hard carbon co-coated nano-silicon anode material.
2. The method for preparing the soft carbon and hard carbon co-coated nano-silicon anode material according to claim 1, characterized in that, The ratio of asphalt, succinic anhydride and triethylamine is 1g:2~4g:3~5mL.
3. The method for preparing the soft carbon and hard carbon co-coated nano-silicon anode material according to claim 1, characterized in that, In S1, after adding glyceryl monostearate and graphene oxide, stir at a speed of 2000~4000 r / min for 30~60 min under heat preservation.
4. The method for preparing the soft carbon and hard carbon co-coated nano-silicon anode material according to claim 1, characterized in that, After adding polyvinylpyrrolidone to S1, stir at a speed of 500~2000 r / min for 10~30 min while keeping warm.
5. The method for preparing the soft carbon and hard carbon co-coated nano-silicon anode material according to claim 1, characterized in that, The average molecular weight of the polyvinylpyrrolidone is 40,000 to 1,300,000.
6. The method for preparing the soft carbon and hard carbon co-coated nano-silicon anode material according to claim 1, characterized in that, The mass ratio of the soft carbon and hard carbon precursor mixture to the silicon anode material is 1:0.3~2.
7. The method for preparing the soft carbon and hard carbon co-coated nano-silicon anode material according to claim 1, characterized in that, In S2, the stirring speed is 1000~2000 r / min, and the time is 10~30 min.
8. The method for preparing the soft carbon and hard carbon co-coated nano-silicon anode material according to claim 1, characterized in that, In S3, the heating and carbonization temperature is 800~1100℃, and the time is 12~24h.
9. A soft carbon and hard carbon co-coated nano-silicon anode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.