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CN-121076094-B - Soft carbon and hard carbon co-coated nano silicon negative electrode material and preparation method thereof

CN121076094BCN 121076094 BCN121076094 BCN 121076094BCN-121076094-B

Abstract

The invention discloses a soft carbon and hard carbon co-coated nano silicon negative electrode material and a preparation method thereof, and relates to the technical field of lithium ion battery negative electrode materials. According to the invention, after carboxylated asphalt is melted, graphene oxide and glyceryl monostearate are added for mixing modification, the obtained modified asphalt is used as a soft carbon precursor and is mixed with specific hard carbon precursor polyvinylpyrrolidone to be used as a carbon precursor for coating a silicon negative electrode material, and then the silicon negative electrode material is heated and carbonized to obtain the soft carbon and hard carbon co-coated nano silicon negative electrode material, so that the obtained negative electrode material has excellent cycling stability, high initial efficiency and excellent multiplying power performance, and is a lithium ion battery silicon carbon negative electrode material with excellent comprehensive performance.

Inventors

  • LI WENTING
  • HUANG YONGWANG
  • KONG LU
  • CUI YUNLONG
  • GAO XIAOWEI
  • DU YUPENG
  • XIE QIWEI

Assignees

  • 安徽清致科技发展有限公司

Dates

Publication Date
20260512
Application Date
20250829

Claims (9)

  1. 1. The preparation method of the soft carbon and hard carbon co-coated nano silicon anode material is characterized by comprising the following steps of: S1, heating carboxylated asphalt at 100-200 ℃ until the carboxylated asphalt is molten, adding glycerol monostearate and graphene oxide, fully stirring the mixture under the condition of heat preservation, then adding polyvinylpyrrolidone, and fully stirring the mixture under the condition of heat preservation to obtain a soft carbon and hard carbon precursor mixture, wherein the mass ratio of the carboxylated asphalt, the glycerol monostearate, the graphene oxide and the polyvinylpyrrolidone is 10:0.1-0.2:0.01-0.05:1-10; Adding asphalt and succinic anhydride into a solvent, stirring until the asphalt and the succinic anhydride are dissolved, then dropwise adding triethylamine, heating and refluxing for reaction, removing the solvent after the reaction is finished, adding water into a reaction product, filtering, collecting solids, washing and drying to obtain the carboxylated asphalt; S2, adding a silicon anode material into the soft carbon and hard carbon precursor mixture, and fully stirring at the temperature of 250-400 ℃ to obtain a silicon carbon composite precursor; and S3, heating and carbonizing the silicon-carbon composite precursor, cooling, grinding and sieving to obtain the soft carbon and hard carbon co-coated nano silicon negative electrode material.
  2. 2. The preparation method of the soft carbon and hard carbon co-coated nano silicon anode material is characterized in that the ratio of asphalt to succinic anhydride to triethylamine is 1 g:2-4 g:3-5 mL.
  3. 3. The preparation method of the soft carbon and hard carbon co-coated nano silicon anode material according to claim 1, wherein in the step S1, after glycerol monostearate and graphene oxide are added, stirring is carried out for 30-60 min at a rotating speed of 2000-4000 r/min under the condition of heat preservation.
  4. 4. The method for preparing the soft carbon and hard carbon co-coated nano silicon negative electrode material according to claim 1, wherein in the step S1, polyvinylpyrrolidone is added and stirred at a rotation speed of 500-2000 r/min for 10-30 min under heat preservation.
  5. 5. The method for preparing the soft carbon and hard carbon co-coated nano silicon anode material according to claim 1, wherein the average molecular weight of polyvinylpyrrolidone is 40000-1300000.
  6. 6. The preparation method of the soft carbon and hard carbon co-coated nano silicon negative electrode material according to claim 1, wherein the mass ratio of the soft carbon and hard carbon precursor mixture to the silicon negative electrode material is 1:0.3-2.
  7. 7. The preparation method of the soft carbon and hard carbon co-coated nano silicon anode material according to claim 1, wherein in the step S2, the stirring speed is 1000-2000 r/min, and the stirring time is 10-30 min.
  8. 8. The preparation method of the soft carbon and hard carbon co-coated nano silicon anode material according to claim 1, wherein in the step S3, the heating carbonization temperature is 800-1100 ℃ and the heating carbonization time is 12-24 h.
  9. 9. The soft carbon and hard carbon co-coated nano silicon anode material is characterized by being prepared by the preparation method of any one of claims 1-8.

Description

Soft carbon and hard carbon co-coated nano silicon negative electrode material and preparation method thereof Technical Field The invention relates to the technical field of lithium ion battery anode materials, in particular to a soft carbon and hard carbon co-coated nano silicon anode material and a preparation method thereof. Background The silicon-based negative electrode material has a theoretical specific capacity of 4200mAh/g, and can reach 10 times of the specific capacity of the current commercial graphite negative electrode material. However, since a huge volume effect (> 300%) is generated in the charge and discharge process, the materials are pulverized, and the commercialization of the materials is seriously affected. The solutions currently in common use include silicon nanocrystallization, hollowing or porosification. However, nano silicon, nano hollow silicon and porous silicon have the defects of small particles, large specific surface area and low conductivity, and carbon coating is needed to increase conductivity, adjust particle size distribution and reduce specific surface area, so that the electrochemical performance of the material is improved. Conventional carbon coating often employs a single soft or hard carbon coating, wherein the soft carbon has a high initial efficiency but poor cycling stability, while the hard carbon has a good cycling stability but a relatively low initial efficiency. Therefore, it is necessary to develop a novel silicon-carbon negative electrode material to meet the comprehensive requirements of the lithium ion battery material on the first charge and discharge efficiency, specific capacity and cycle performance. Disclosure of Invention Based on the technical problems in the background technology, the invention provides a soft carbon and hard carbon co-coated nano silicon anode material and a preparation method thereof. The invention provides a preparation method of a soft carbon and hard carbon co-coated nano silicon anode material, which comprises the following steps: S1, heating carboxylated asphalt at 100-200 ℃ until the carboxylated asphalt is molten, adding glycerol monostearate and graphene oxide, fully stirring the mixture under the condition of heat preservation, then adding polyvinylpyrrolidone, and fully stirring the mixture under the condition of heat preservation to obtain a soft carbon and hard carbon precursor mixture, wherein the mass ratio of the carboxylated asphalt, the glycerol monostearate, the graphene oxide and the polyvinylpyrrolidone is 10:0.1-0.2:0.01-0.05:1-10; S2, adding a silicon anode material into the soft carbon and hard carbon precursor mixture, and fully stirring at the temperature of 250-400 ℃ to obtain a silicon carbon composite precursor; and S3, heating and carbonizing the silicon-carbon composite precursor, cooling, grinding and sieving to obtain the soft carbon and hard carbon co-coated nano silicon negative electrode material. According to the invention, after carboxylated asphalt is melted, graphene oxide and glycerin monostearate are added for mixing and modifying, the obtained modified asphalt is used as a soft carbon precursor and is mixed with a specific hard carbon precursor polyvinylpyrrolidone to form an intercalation structure, a synergistic effect is achieved, a network structure can be formed after carbonization of a double carbon source, the transmission of lithium ions is promoted, and the internal pore structure of a carbon layer is improved, so that the initial effect and the rate capability of the silicon negative electrode material are improved, on the one hand, the combination of soft carbon and hard carbon is used as a coated carbon layer, the initial effect and the circulation stability of the silicon negative electrode material can be considered, on the other hand, carboxylated asphalt has more chemical bonds, the bonding with the silicon negative electrode is stronger, the stability of the coated carbon layer is improved, and simultaneously, carboxyl groups in the asphalt can bond with amide groups in the hard carbon precursor polyvinylpyrrolidone by hydrogen, and then combine with the graphene oxide to modify the asphalt to form an intercalation structure, so that the network structure can be formed after carbonization of the double carbon source, the transmission of lithium ions is promoted, and the internal pore structure of the carbon layer is improved, so that the initial effect and the rate capability of the silicon negative electrode material is improved, but the carboxylated asphalt is easier to aggregate, and the dispersion is unfavorable, and the dispersion is not favorable, so that the uniformity of the modified asphalt is improved, the silicon negative electrode is better, the uniformity and the stability of the silicon negative electrode is better, the silicon negative electrode is coated, and the stability is better than the silicon carbon layer is coated by the uniform, and the carb