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EP-4738466-A1 - SILICON-CARBON NEGATIVE ELECTRODE MATERIAL, AND PREPARATION METHOD THEREFOR AND USE THEREOF

EP4738466A1EP 4738466 A1EP4738466 A1EP 4738466A1EP-4738466-A1

Abstract

A silicon-carbon negative electrode material includes a core and a shell. The core includes a porous carbon skeleton and silicon dispersed in pores of the porous carbon skeleton. Carbon nanotubes are wrapped and dispersed in the porous carbon skeleton. In the silicon-carbon negative electrode material, the content of silicon elements in the silicon-carbon negative electrode material is 25 wt% to 55 wt%. The shell includes a carbon material. In a linear scanning electron microscope and energy-dispersive X-ray spectrum of a cross section of the silicon-carbon negative electrode material, the standard deviation of content changes of the silicon elements from the center to the edge of the cross section does not exceed 200. Further provided are an electrochemical apparatus and a preparation method for a silicon-carbon negative electrode material. This application can improve electrical conductivity and reduce expansion, thereby prolonging the service life.

Inventors

  • Yi, Zheng
  • SHAO, WENLONG
  • SU, Yisong
  • XIE, YUANSEN

Assignees

  • Ningde Amperex Technology Limited

Dates

Publication Date
20260506
Application Date
20240430

Claims (10)

  1. A silicon-carbon negative electrode material, comprising a core and a shell, wherein the core comprises a porous carbon skeleton and silicon dispersed in pores of the porous carbon skeleton, and carbon nanotubes are dispersed within the porous carbon skeleton; in the silicon-carbon negative electrode material, a content of silicon elements in the silicon-carbon negative electrode material is 25 wt% to 55 wt%, and the shell includes a carbon material; and in a linear scanning electron microscope and energy-dispersive X-ray spectrum of a cross section of the silicon-carbon negative electrode material, a standard deviation of content changes of the silicon elements from a center to an edge of the cross section does not exceed 200.
  2. The silicon-carbon negative electrode material according to claim 1, wherein an electrical conductivity of the silicon-carbon negative electrode material is 9 S/cm to 30 S/cm, and/or a particle elastic modulus of the silicon-carbon negative electrode material is 4 GPa to 10 GPa.
  3. The silicon-carbon negative electrode material according to claim 1 or 2, wherein a content of the carbon nanotubes is 0.2 wt% to 7 wt%.
  4. The silicon-carbon negative electrode material according to any one of claims 1 to 3, wherein the silicon-carbon negative electrode material satisfies at least one of the following conditions: (1) an X-ray diffraction pattern of the silicon-carbon negative electrode material has a characteristic peak within a range of 20° to 30°, and a peak half width of the characteristic peak is greater than 2°; (2) a Raman spectrum of the silicon-carbon negative electrode material has a characteristic peak within a range of 450 cm -1 to 500 cm -1 ; and (3) a particle size Dv50 of the silicon-carbon negative electrode material is 3 µm to 20 µm, and a particle size Dv99 of the silicon-carbon negative electrode material is 3 µm to 20 µm.
  5. The silicon-carbon negative electrode material according to any one of claims 1 to 4, wherein a volume of pores having a diameter of greater than 2 nm in the silicon-carbon negative electrode material is greater than a volume of pores having a diameter of 2 nm or less.
  6. An electrochemical apparatus, comprising a positive electrode plate, a negative electrode plate and a separator; wherein the negative electrode plate comprises a negative current collector and a negative active layer; and the negative active layer comprises a negative active material, wherein the negative active material comprises the silicon-carbon negative electrode material according to any one of claims 1 to 5.
  7. The electrochemical apparatus according to claim 6, wherein the negative active material further comprises graphite, in the negative active material, a content of the silicon-carbon negative electrode material is 5 wt% to 40 wt%, and a content of the graphite is 95 wt% to 60 wt%.
  8. A preparation method for the silicon-carbon negative electrode material according to claim 1, comprising: mixing a resin and the carbon nanotubes to form a mixture, and curing the mixture; carbonizing the cured mixture, and then activating the mixture to obtain the porous carbon skeleton; and performing silane deposition on the porous carbon skeleton to form the core, and then forming the shell by alkane.
  9. The preparation method for the silicon-carbon negative electrode material according to claim 8, wherein carbonization conditions comprise increasing a temperature to 700°C to 1100°C and maintaining the temperature for 1 to 5 hours, and the activation is specifically implemented by means of carbon dioxide, water vapor, sodium hydroxide, potassium hydroxide or a phosphoric acid after carbonization cooling.
  10. The preparation method for the silicon-carbon negative electrode material according to claim 8 or 9, wherein a step of "performing silane deposition on the porous carbon skeleton to form a core, and then forming a shell by alkane" specifically comprises: slowly increasing a temperature of the porous carbon skeleton in an inert atmosphere to 400°C to 600°C, then maintaining the temperature, changing the atmosphere to a silane gas mixture, performing deposition for 1 to 20 hours, wherein the silane gas mixture contains, in percentage by mass, 2% to 20% of silane and 80% to 98% of inert gas; and changing the atmosphere to an alkane gas mixture at 500°C to 1000°C, holding for 10 hours to form the shell, then changing the atmosphere to the inert atmosphere, and decreasing the temperature to a room temperature, wherein the alkane gas mixture contains, in percentage by mass, 5% to 100% of alkane and 0% to 95% of inert gas.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Chinese Patent Application No. 202310786717.2, filed with the Chinese Patent Office on June 29, 2023 and entitled "SILICON-CARBON NEGATIVE ELECTRODE MATERIAL, AND PREPARATION METHOD THEREFOR AND APPLICATION THEREOF", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD This application relates to the field of electrochemical energy storage, and in particular, to a silicon-carbon negative electrode material and a preparation method therefor, a negative electrode plate applying the silicon-carbon negative electrode material, and an electrochemical apparatus applying the negative electrode plate. BACKGROUND By virtue of high volumetric and mass energy densities, environmental friendliness, high operating voltage, small size, light weight, long service life and other advantages, lithium-ion batteries are widely applied in the field of portable consumer electronics. With the high-speed development of electric vehicles and portable electronic devices in recent years, people have higher and higher demands on energy density, safety, cycle performance and the like of batteries, and expect the generation of new lithium-ion batteries with improved comprehensive performance. The energy density and the cycle performance are the key technical problems urgent to be solved. Improving active materials in electrodes is one of research directions for solving the above problems. At present, graphite is the most widely used negative electrode material, and has the advantages of high efficiency, stable charging and discharging platforms, etc. However, the performance of the current commercial graphite is almost developed to the extreme extent, and the lower capacity and the potential safety hazards of lithium dendrites hinder the further application thereof. Compared with the graphite as the negative electrode material, by virtue of the characteristics of ultrahigh theoretical specific capacity, suitable operating voltage, etc., elemental silicon is considered to be the most promising negative electrode material of lithium batteries, which can replace graphite. However, the low electrical conductivity and large volume expansion during alloying/dealloying severely restrict the large-scale application of the elemental silicon in lithium-ion batteries. SUMMARY This application provides a silicon-carbon negative electrode material which can improve electrical conductivity and reduce expansion. In addition, this application further provides a negative electrode plate applying the silicon-carbon negative electrode material, and an electrochemical apparatus applying the negative electrode plate. This application further provides a preparation method for the silicon-carbon negative electrode material. A first aspect of this application provides a silicon-carbon negative electrode material. The silicon-carbon negative electrode material includes a core and a shell. The core includes a porous carbon skeleton and silicon dispersed in pores of the porous carbon skeleton. Carbon nanotubes are wrapped and dispersed in the porous carbon skeleton. A content of silicon elements in the silicon-carbon negative electrode material is 25 wt% to 55 wt%. The shell includes a carbon material. In a linear scanning electron microscope and energy-dispersive X-ray spectrum of a cross section of the silicon-carbon negative electrode material, a standard deviation of content changes of the silicon elements from a center to an edge of the cross section does not exceed 200. As the carbon nanotubes in the silicon-carbon negative electrode material of this application have good electrical conductivity and mechanical properties, the carbon nanotubes with a specified content dispersed in the porous carbon skeleton can, on the one hand, improve the electrical conductivity of the silicon-carbon negative electrode material, and on the other hand, improve the mechanical properties of the silicon-carbon negative electrode material, and restrain the expansion of the silicon-carbon negative electrode material, thereby facilitating improvement in the structural stability. Moreover, according to the linear scanning electron microscope and energy-dispersive X-ray spectrum of the cross section of the silicon-carbon negative electrode material, it can be seen that the silicon elements in the silicon-carbon negative electrode material are distributed uniformly, thereby facilitating further improvement in the electrical conductivity and mechanical properties of the silicon-carbon negative electrode material. When the above silicon-carbon negative electrode material is applied to the negative electrode plate of the electrochemical apparatus, the electrical conductivity of the silicon-carbon negative electrode material is improved, such that the trapping possibility of lithium in the silicon-carbon negative electrode material can be improved, so as to improve the delith