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EP-4742321-A1 - SILICON-CARBON NEGATIVE ELECTRODE MATERIAL AND PREPARATION METHOD THEREFOR

EP4742321A1EP 4742321 A1EP4742321 A1EP 4742321A1EP-4742321-A1

Abstract

A silicon-carbon negative electrode material and a preparation method therefor are provided. the silicon-carbon negative electrode material includes a carbon skeleton having a pore structure and a silicon-based material arranged in the pore structure, where in a region formed by extending from a surface of the silicon-carbon negative electrode material inward by 10 nm away from the surface, a content of high-valence silicon is less than 25% relative to a total amount of low-valence silicon and the high-valence silicon, where the low-valence silicon is silicon with a valence of 0 to 2, and the high-valence silicon is silicon with a valence of 3 to 4. For the silicon-carbon negative electrode material, the specific delithiated capacity and the initial coulombic efficiency of the silicon-carbon negative electrode material can be improved, and the specific discharge capacity and the initial coulombic efficiency of a secondary battery can be enhanced.

Inventors

  • XIE, Shuai
  • WANG, Jiazheng
  • LIU, LIANGBIN
  • LYU, Zijian
  • CHEN, WENQIANG
  • DENG, Jingxian
  • GUO, XIAOXIN
  • SU, Yingwei

Assignees

  • Contemporary Amperex Technology Co., Limited

Dates

Publication Date
20260513
Application Date
20240524

Claims (18)

  1. A silicon-carbon negative electrode material, wherein the silicon-carbon negative electrode material comprises a carbon skeleton having a pore structure and a silicon-based material arranged in the pore structure, wherein in a region formed by extending from a surface of the silicon-carbon negative electrode material inward by 10 nm away from the surface, a content of high-valence silicon is less than 25% relative to a total amount of low-valence silicon and the high-valence silicon, wherein the low-valence silicon is silicon with a valence of 0 to 2, and the high-valence silicon is silicon with a valence of 3 to 4.
  2. The silicon-carbon negative electrode material according to claim 1, wherein in the region formed by extending from the surface of the silicon-carbon negative electrode material inward by 10 nm away from the surface, the content of the high-valence silicon is less than or equal to 20% relative to the total amount of the low-valence silicon and the high-valence silicon.
  3. The silicon-carbon negative electrode material according to claim 1 or 2, wherein in a region formed from a distance of 10 nm away from the surface of the silicon-carbon negative electrode material to a distance of 20 nm away from the surface of the silicon-carbon negative electrode material, the content of the high-valence silicon is less than or equal to 20% relative to the total amount of the low-valence silicon and the high-valence silicon, and optionally, less than or equal to 10%.
  4. The silicon-carbon negative electrode material according to any one of claims 1 to 3, wherein in a region formed from a distance of 20 nm away from the surface of the silicon-carbon negative electrode material to a distance of 30 nm away from the surface of the silicon-carbon negative electrode material, the content of the high-valence silicon is less than or equal to 10% relative to the total amount of the low-valence silicon and the high-valence silicon, and optionally, less than or equal to 5%.
  5. The silicon-carbon negative electrode material according to any one of claims 1 to 4, wherein the silicon-carbon negative electrode material satisfies at least one of the following conditions: (1) a volume distribution particle size Dv50 of the silicon-carbon negative electrode material is 5 µm to 10 µm, and optionally, Dv50 is 6 µm to 9 µm; (2) a specific surface area of the silicon-carbon negative electrode material is less than or equal to 5 m 2 /g, and optionally, less than or equal to 2 m 2 /g; (3) a powder compacted density of the silicon-carbon negative electrode material under a pressure of 3000 N is 0.8 g/cm 3 to 1.2 g/cm 3 , and optionally, 0.9 g/cm 3 to 1.2 g/cm 3 ; (4) a tapped density of the silicon-carbon negative electrode material is 0.9 g/cm 3 to 1.1 g/cm 3 , and optionally, 1.0 g/cm 3 to 1.1 g/cm 3 ; and (5) a specific delithiated capacity of the silicon-carbon negative electrode material is 800 mAh/g to 2500 mAh/g, and optionally, 1000 mAh/g to 2000 mAh/g.
  6. The silicon-carbon negative electrode material according to any one of claims 1 to 5, wherein a pore volume of the carbon skeleton is 0.4 cm 3 /g to 1.5 cm 3 /g, optionally 0.6 cm 3 /g to 1.2 cm 3 /g; and/or a volume proportion of micropores whose pore diameters are less than 2 nm relative to the pore volume is greater than or equal to 60%, and optionally, greater than or equal to 80%.
  7. The silicon-carbon negative electrode material according to any one of claims 1 to 6, wherein the surface of the silicon-carbon negative electrode material has a coating layer; and optionally, the coating layer is a carbon coating layer.
  8. A preparation method for the silicon-carbon negative electrode material according to any one of claims 1 to 7, comprising the following steps: a step of forming silicon-carbon particles, wherein the carbon skeleton having the pore structure is allowed to react with a silicon source gas to form silicon-carbon particles having the silicon-based material in the pore structure; and a step of treating the silicon-carbon particles, wherein a mixed gas comprising a carbon source gas and an inert gas is fed to the silicon-carbon particles at a gas feeding amount greater than 0 L/min and less than or equal to 10 L/min under a condition that a temperature is 500 °C to 700 °C and a pressure is 0 kpa to 1 kpa, and the carbon source gas is selected from at least one of ethane, ethylene, acetylene, and methane.
  9. The preparation method according to claim 8, wherein in the step of treating the silicon-carbon particles, the mixed gas is fed to the silicon-carbon particles at the gas feeding amount of 0.5 L/min to 4 L/min under the condition that the temperature is 550 °C to 650 °C and the pressure is 0 kpa to 0.5 kpa.
  10. The preparation method according to claim 8 or 9, wherein the mixed gas comprises 10% by volume to 70% by volume of acetylene, 0% by volume to 20% by volume of methane, and 10% by volume to 90% by volume of inert gas; and and optionally, the mixed gas comprises 15% by volume to 60% by volume of acetylene, 5% by volume to 10% by volume of methane, and 30% by volume to 80% by volume of inert gas.
  11. The preparation method according to any one of claims 8 to 10, wherein the step of forming the silicon-carbon particles comprises the following step: vacuumizing a reaction apparatus, and then feeding the inert gas.
  12. The preparation method according to any one of claims 8 to 11, wherein the step of forming the silicon-carbon particles comprises the following step: heating the carbon skeleton having the pore structure to 400 °C to 550 °C in the reaction apparatus, to exclude oxygen gas from the carbon skeleton.
  13. The preparation method according to any one of claims 8 to 12, wherein the step of forming the silicon-carbon particles comprises the following step: feeding a mixed gas of the silicon source gas and the inert gas into the reaction apparatus, and performing deposition at a temperature of 400 °C to 550 °C for 2 hours to 10 hours, to form the silicon-carbon particles.
  14. The preparation method according to any one of claims 8 to 13, wherein the silicon source gas is selected from one or more of silane, disilane, dichlorosilane, and trichlorosilane; and optionally, the silicon source gas is silane.
  15. The preparation method according to any one of claims 8 to 14, wherein the inert gas is argon gas.
  16. A negative electrode plate, comprising the silicon-carbon negative electrode material according to any one of claims 1 to 7 or a silicon-carbon negative electrode material prepared by using the preparation method according to any one of claims 8 to 15.
  17. A secondary battery, comprising the negative electrode plate according to claim 16.
  18. A power consuming apparatus, comprising the secondary battery according to claim 17.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present disclosure is proposed based on Chinese Patent Application No. 202311619241.X, filed on November 28, 2023 and entitled "SILICON-CARBON NEGATIVE ELECTRODE MATERIAL AND PREPARATION METHOD THEREFOR", which is incorporated herein by reference in its entirety, and claims priority to the Chinese Patent Application. TECHNICAL FIELD The present disclosure relates to the field of battery technologies, and in particular, to a silicon-carbon negative electrode material and a preparation method therefor. BACKGROUND With continuous improvement of power of power consuming devices such as a mobile phone, a computer, an electric tool, and an electric vehicle, requirements of people on an energy density of a secondary battery also increase accordingly. A silicon-based negative electrode material has a relatively high specific capacity. Currently, the industry already starts to improve the energy density of a secondary battery by adding a silicon-based negative electrode material to a negative electrode plate. However, a volume expansion rate of the silicon-based negative electrode material increases after lithiation, which may cause cracking of the negative electrode plate. To resolve the problem that the volume expansion rate of the silicon-based negative electrode material is high, currently, a silicon-carbon negative electrode material formed by depositing silicon inside porous carbon is mostly used, and expansion of the silicon-based material is reduced by using voids inside the porous carbon. However, because the silicon in the silicon-carbon negative electrode material is converted into high-valence silicon, the specific capacity of the silicon-carbon negative electrode material decreases, and the initial coulombic efficiency of the secondary battery is affected. SUMMARY The present disclosure is provided in view of the foregoing subject. An objective of the present disclosure is to provide a silicon-carbon negative electrode material and a preparation method therefor. The specific delithiated capacity and the initial coulombic efficiency of the silicon-carbon negative electrode material are high, and then the specific discharge capacity and the initial coulombic efficiency of a secondary battery can be enhanced. To achieve the foregoing objective, a first aspect of the present disclosure provides a silicon-carbon negative electrode material, where the silicon-carbon negative electrode material includes a carbon skeleton having a pore structure and a silicon-based material arranged in the pore structure, where in a region formed by extending from a surface of the silicon-carbon negative electrode material inward by 10 nm away from the surface, a content of high-valence silicon is less than 25% relative to a total amount of low-valence silicon and the high-valence silicon, where the low-valence silicon is silicon with a valence of 0 to 2, and the high-valence silicon is silicon with a valence of 3 to 4. In the silicon-carbon negative electrode material of the present disclosure, the content of high-valence silicon is suppressed to a low level, so that the content of low-valence silicon is high, thereby improving the specific delithiated capacity and the initial coulombic efficiency of the negative electrode material, and effectively improving the specific discharge capacity and the initial coulombic efficiency of a secondary battery. In some implementations, in the region formed by extending from the surface of the silicon-carbon negative electrode material inward by 10 nm away from the surface, the content of the high-valence silicon is less than or equal to 20% relative to the total amount of the low-valence silicon and the high-valence silicon. Therefore, the negative electrode material has higher specific delithiated capacity and initial coulombic efficiency, and the obtained secondary battery has better specific discharge capacity and initial coulombic efficiency. In some implementations, in a region formed from a distance of 10 nm away from the surface of the silicon-carbon negative electrode material to a distance of 20 nm away from the surface of the silicon-carbon negative electrode material, the content of the high-valence silicon is less than or equal to 20% relative to the total amount of the low-valence silicon and the high-valence silicon, and optionally, less than or equal to 10%. Therefore, in the silicon-carbon negative electrode material of the present disclosure, the content of high-valence silicon is further suppressed to a low level, which is more beneficial to improving specific delithiated capacity and initial coulombic efficiency of the negative electrode material. In some implementations, in a region formed from a distance of 20 nm away from the surface of the silicon-carbon negative electrode material to a distance of 30 nm away from the surface of the silicon-carbon negative electrode material, the content of the high-valence silicon is less