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CN-119315005-B - Negative electrode active material, negative electrode sheet, and battery

CN119315005BCN 119315005 BCN119315005 BCN 119315005BCN-119315005-B

Abstract

The invention relates to the technical field of batteries, in particular to a negative electrode active material, a negative electrode plate comprising the negative electrode active material and a battery. The anode active material comprises silicon-carbon composite particles, wherein the silicon-carbon composite particles are provided with closed pores, the volume ratio of the closed pores is 4% -50%, the silicon-carbon composite particles are provided with a core-shell structure, the shell thickness of the core-shell structure is t,0<t is less than or equal to 10nm, the cross section of each silicon-carbon composite particle is provided with a first area and a second area, the content of silicon element in the first area is c1, the content of silicon element in the second area is c2, c2/c1 is less than or equal to 0.15 and less than or equal to 1.4, the size of a perpendicular line of a tangent line of any point on the edge of the cross section is L, on the perpendicular line, the area which is 0.001L-0.1L away from the edge of the cross section forms the first area, and the area which is 0.1L-0.5L away from the edge of the cross section forms the second area. The battery provided by the invention can be used for achieving higher energy density, first coulombic efficiency, multiplying power performance and cycle stability.

Inventors

  • WANG HUI
  • XUE JIACHEN
  • LIU CHUNYANG
  • LI SULI

Assignees

  • 珠海冠宇电池股份有限公司

Dates

Publication Date
20260512
Application Date
20240926

Claims (20)

  1. 1. A negative electrode active material, characterized in that the negative electrode active material comprises silicon-carbon composite particles; the silicon-carbon composite particles are provided with closed pores, and the volume ratio of the closed pores is 4% -50%; the silicon-carbon composite particles are of a core-shell structure, wherein a shell of the core-shell structure comprises carbon elements, and the thickness of the shell is t, 0<t-10 nm; The core of the core-shell structure comprises carbon element and silicon element, and the core consists of porous carbon and silicon material positioned in the pores of the porous carbon; the cross section of the silicon-carbon composite particle is provided with a first area and a second area, the mass content of silicon element in the first area is c1, the mass content of silicon element in the second area is c2, c2/c1 is 0.23< 0.76, the size of a perpendicular line of a tangent line of any point on the edge of the cross section on the cross section is L, on the perpendicular line, an area which is 0.001L-0.1L away from the edge of the cross section forms the first area, and an area which is 0.1L-0.5L away from the edge of the cross section forms the second area.
  2. 2. The anode active material according to claim 1, wherein the volume ratio of the closed cells is 5% to 49%; And/or, t is more than or equal to 0.2nm and less than or equal to 10nm.
  3. 3. The anode active material according to claim 2, wherein the volume ratio of the closed cells is 11% to 35%; and/or, t is more than or equal to 1nm and less than or equal to 8nm.
  4. 4. The anode active material according to claim 1 or 2, wherein the mass content of silicon element in the silicon-carbon composite particles is 20% to 65%; And/or the mass content c1 of the silicon element in the first region is 30% -75%; And/or the mass content c2 of the silicon element in the second region is 5-60%.
  5. 5. The anode active material according to claim 4, wherein the mass content of silicon element in the silicon-carbon composite particles is 21% to 64%; and/or the mass content c1 of the silicon element in the first region is 31% -71%; and/or the mass content c2 of the silicon element in the second region is 6% -55%.
  6. 6. The anode active material according to claim 5, wherein the mass content of silicon element in the silicon-carbon composite particles is 25% to 60%; and/or the mass content c1 of the silicon element in the first region is 38% -66%; and/or, the mass content c2 of the silicon element in the second region is 9% -50%.
  7. 7. The anode active material according to claim 1 or 2, wherein the outer shell comprises amorphous carbon.
  8. 8. The anode active material according to claim 1 or 2, wherein the silicon-carbon composite particles include at least one of nitrogen element, phosphorus element, and sulfur element.
  9. 9. The anode active material according to claim 8, wherein the silicon-carbon composite particles include nitrogen element, phosphorus element, and sulfur element.
  10. 10. The anode active material according to claim 9, wherein a sum of mass contents of nitrogen element, phosphorus element, and sulfur element in the silicon carbon composite particles is 15ppm to 1000ppm.
  11. 11. The anode active material according to claim 10, wherein a sum of mass contents of nitrogen element, phosphorus element, and sulfur element in the silicon carbon composite particles is 30ppm to 500ppm.
  12. 12. The anode active material according to claim 1 or 2, wherein particle diameters Dv90 and Dv10 of the silicon-carbon composite particles satisfy 5 μm ∈dv90-Dv10 ∈25 μm; And/or Dv10 is 1 μm to 6 μm; and/or, dv90 is 10 μm to 30 μm.
  13. 13. The anode active material according to claim 12, wherein 7 μm or less Dv90-Dv10 or less 24 μm; And/or Dv10 is2 μm to 5 μm; And/or, dv90 is 12 μm to 20 μm.
  14. 14. The negative electrode active material according to claim 13, wherein 7 μm or less Dv90-Dv10 or less 18 μm.
  15. 15. The anode active material according to claim 1 or 2, wherein the silicon carbon composite particles have an oil absorption value of 10ml/100g-100ml/100g.
  16. 16. The anode active material according to claim 15, wherein the silicon carbon composite particles have an oil absorption value of 31ml/100g-79ml/100g.
  17. 17. The anode active material according to claim 1 or 2, wherein the silicon-carbon composite particles include lithium element.
  18. 18. The anode active material according to claim 17, wherein the mass content of lithium element in the silicon carbon composite particles is 0.1% to 20%.
  19. 19. The anode active material according to claim 18, wherein the mass content of lithium element in the silicon carbon composite particles is 1% to 5%.
  20. 20. The anode active material according to claim 1 or 2, wherein a weight gain peak exists at 600 ℃ to 800 ℃ in a thermogravimetric curve of the silicon-carbon composite particles under an air atmosphere.

Description

Negative electrode active material, negative electrode sheet, and battery Technical Field The invention relates to the technical field of batteries, in particular to a negative electrode active material, a negative electrode plate comprising the negative electrode active material and a battery comprising the negative electrode active material. Background The lithium ion battery is widely applied to the fields of consumer electronics equipment, electric automobiles, energy storage power stations and the like according to the characteristics of small volume, light weight, no memory effect and the like. In the current commercial lithium ion battery, the cathode material is mainly graphite material, but the actual gram capacity of the existing graphite material is lower (only about 360 mAh/g) and is close to the theoretical limit (372 mAh/g), and the development space is limited. The silicon-based material has ultrahigh theoretical specific capacity (4200 mAh/g), and is one of ideal materials for further improving the energy density of the lithium ion battery. However, the existing silicon-based material has large volume expansion in the process of charging and discharging the battery, and the problems of rapid battery cycle attenuation and large volume change rate are easily caused. Meanwhile, the lithium ion diffusion coefficient of the silicon-based material is low, and the quick charging capability of the silicon-containing lithium ion battery is limited. Disclosure of Invention The present invention has been made to overcome the above-mentioned problems occurring in the prior art with silicon-based materials, and an object of the present invention is to provide a negative electrode active material, a negative electrode sheet including the negative electrode active material, and a battery including the negative electrode active material. The negative electrode active material has good ionic conductivity and electronic conductivity and high structural stability while ensuring high gram capacity. The battery comprising the negative electrode active material provided by the invention can achieve higher energy density, first coulombic efficiency, rate capability and cycle stability. In the related art, the silicon-based material has the problems of large volume expansion and low lithium ion diffusion coefficient. The inventor of the present invention has found through a great deal of research that the silicon and carbon are made into a composite material, and by controlling the relation of the silicon content in a specific region of the silicon-carbon composite particles, the volume ratio of closed pores and the thickness of the shell, the negative electrode active material can have higher ionic conductivity and electronic conductivity while ensuring higher gram capacity, and has better structural stability, so that the volume expansion is smaller in the battery cycle process. The reasons for this may be: First, since the generation of closed cell structures in the silicon carbon composite particles is related to the deposition of silicon during the preparation thereof, the volume of closed cells is related to the silicon content in the silicon carbon composite particles. The silicon content in the silicon-carbon composite particles directly influences the volume expansion of the silicon-carbon composite particles, and the larger the silicon content is, the larger the volume expansion of the silicon-carbon composite particles is within a certain range. And the volume of the closed pores can provide a certain buffer space for the expansion of silicon, so that the volume expansion of the silicon-carbon composite particles can be improved by regulating the volume occupation ratio of the closed pores. Second, the shell containing carbon element is arranged on the surface of the inner core of the silicon-carbon composite particle, so that the electronic conductivity and the ionic conductivity of the silicon-carbon composite particle can be remarkably improved. However, since the theoretical gram capacity of the carbon material is low relative to the silicon material, it is necessary to control the thickness of the shell so that the silicon-carbon composite particles can achieve both gram capacity and ionic and electronic conductivity. Third, only controlling the volume ratio of the closed pores and the thickness of the shell has limited performance improvement on the silicon-carbon composite particles, because the coating layer is arranged on the surface of the inner core of the silicon-carbon composite particles, the improvement effect on the electronic conductivity and the ionic conductivity of the outer side of the silicon-carbon composite particles is better than that of the inner side of the silicon-carbon composite particles, and the transmission rates of electrons and ions in the inner side and the outer side of the silicon-carbon composite particles are not matched, so that the ionic conductivity, the electr