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CN-122025584-A - Silicon-based composite material, preparation method thereof, negative plate and battery

CN122025584ACN 122025584 ACN122025584 ACN 122025584ACN-122025584-A

Abstract

The embodiment of the application provides a silicon-based composite material, a preparation method thereof, a negative plate and a battery. The coating layer comprises an amorphous carbon material, and the interlayer spacing of the amorphous carbon material is 0.305nm-0.325nm. According to the application, the coating layer containing the amorphous carbon material with the specific interlayer spacing is formed on the surface of the silicon-containing core body, so that the damage of silicon to the electrode material in the cyclic charge-discharge process is relieved, and the structural stability and electrochemical performance of the silicon-based composite material are improved.

Inventors

  • WANG RUOMING
  • FENG DAOYAN
  • WANG SHUYA

Assignees

  • 宁波容百新能源科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260205

Claims (10)

  1. 1. A silicon-based composite material is characterized by comprising a silicon-containing core body and a coating layer coated on at least part of the surface of the silicon-containing core body; the coating layer comprises an amorphous carbon material, and the interlayer spacing of the amorphous carbon material is 0.305nm-0.325nm.
  2. 2. The silicon-based composite material of claim 1, wherein the silicon-containing core has a chemical formula of Li x Si y , wherein 0.03 ∈x ∈y ∈0.6; And/or, the interlayer spacing of the amorphous carbon material is 0.310nm-0.315nm; And/or, the amorphous carbon material comprises an N element and an S element; And/or, the amorphous carbon material includes C-N bonds and C-S bonds.
  3. 3. The silicon-based composite material of claim 1 or 2, wherein the silicon-containing core comprises a first active material comprising a lithium silicon alloy and a second active material comprising silicon; and/or, in the lithium silicon alloy, the molar ratio of the lithium element to the silicon element is (1-4.4): 1, preferably (3.75-4.4): 1; and/or the mass ratio of the lithium silicon alloy to the silicon is (0.05-0.3): 1.
  4. 4. The silicon-based composite material of claim 3 wherein the lithium silicon alloy comprises at least one of Li 4.4 Si、Li 3.75 Si.
  5. 5. The silicon-based composite material according to any one of claims 1-4, wherein the D50 particle size of the silicon-based composite material is 2-5 μm; and/or the thickness of the coating layer is 3 nm-10 nm; and/or the amorphous carbon material accounts for 2% -6% of the silicon-based composite material by mass, and preferably 2% -4%.
  6. 6. A method of preparing a silicon-based composite material according to any one of claims 1 to 5, comprising: mixing lithium silicon alloy and silicon, and then placing the mixture in a first inert atmosphere for first ball milling to obtain a silicon-containing nucleus; Placing the silicon-containing nuclear body and the coating agent in a second inert atmosphere, and performing second ball milling at a rotating speed of 300rpm-700rpm to obtain a silicon-based composite material precursor; and carrying out vacuum sintering on the precursor of the silicon-based composite material for 1-3 h at the temperature of more than 273 ℃ to obtain the silicon-based composite material.
  7. 7. The method of producing a silicon-based composite material according to claim 6, wherein the D50 particle size of the silicon is 0.1 μm to 4 μm, preferably 0.8 μm to 2 μm; And/or the D50 particle size of the lithium silicon alloy is 0.1-4 mu m, preferably 0.8-2 mu m; And/or the D50 particle size of the lithium silicon alloy is less than or equal to the D50 particle size of the silicon; and/or the ball-to-material ratio of the first ball mill is (15-50): 1; and/or the ball milling rotating speed of the first ball milling is 500-600 rpm, and the ball milling time is 3-5 h; and/or the ball milling ratio of the second ball milling is (15-50): 1; the ball milling time of ball milling is 6-10 h.
  8. 8. The method of preparing a silicon-based composite material according to claim 6 or 7, wherein the coating agent comprises at least one of a sulfur-containing amino acid, a borate polymer, preferably a sulfur-containing amino acid; And/or the mixing mass ratio of the silicon-containing core body to the coating agent is (10-20): 1.
  9. 9. A negative electrode sheet comprising the silicon-based composite material according to any one of claims 1 to 5 or a silicon-based composite material produced by the production method according to any one of claims 6 to 8.
  10. 10. A battery comprising the silicon-based composite material according to any one of claims 1 to 5 or the silicon-based composite material produced by the production method according to any one of claims 6 to 8 or the negative electrode sheet according to claim 9.

Description

Silicon-based composite material, preparation method thereof, negative plate and battery Technical Field The application relates to the field of battery materials, in particular to a silicon-based composite material, a preparation method thereof, a negative plate and a battery. Background Silicon, a typical semiconductor, has a low electron conductivity (1.56×10 -3 S/cm) and a high Li + diffusion coefficient (10 -14~10-13cm2/S), and has a great potential for manufacturing high energy density batteries. Research shows that the highest theoretical specific capacity of the silicon-based negative electrode material can reach 3579mAh/g, and the silicon-based negative electrode material can be used in the field of lithium battery materials in the future or is a power battery negative electrode material which is of great concern. The silicon-based negative electrode material has the advantages of good quick charge performance, strong endurance capability and good safety performance, but has the problems that the volume of the silicon material can expand by 300% in the charge and discharge process of a lithium battery, the repeated volume expansion can cause the silicon-based negative electrode material to generate cracks until pulverization, the continuously generated SEI film in the process can also excessively consume Li +, the battery cycle performance is poor, and in addition, the silicon-based material has the problem of low initial coulombic efficiency. Therefore, it is needed to research a silicon-based anode material with good volume stability, so that the battery has high energy density and excellent cycle performance and first effect. Disclosure of Invention The embodiment of the application provides a silicon-based composite material, a preparation method thereof, a negative electrode plate and a battery, which are used for relieving the damage of silicon to an electrode material in the cyclic charge and discharge process and improving the structural stability and electrochemical performance of the silicon-based negative electrode material. In a first aspect, embodiments of the present application provide a silicon-based composite material comprising a silicon-containing core and a cladding layer coating at least a portion of a surface of the silicon-containing core; the coating layer comprises an amorphous carbon material, and the interlayer spacing of the amorphous carbon material is 0.305nm-0.325nm. In one possible embodiment, the silicon-containing core has the formula Li xSiy, wherein 0.03≤x≤y≤0.6; And/or the interlayer spacing of the amorphous carbon material is 0.310 nm-0.315 nm; And/or, the amorphous carbon material comprises an N element and an S element; And/or, the amorphous carbon material includes C-N bonds and C-S bonds. In one possible embodiment, the silicon-containing core comprises a first active material and a second active material; the first active material comprises a lithium silicon alloy, and the second active material comprises silicon; and/or, in the lithium silicon alloy, the molar ratio of the lithium element to the silicon element is (1-4.4): 1, preferably (3.75-4.4): 1; and/or the mass ratio of the lithium silicon alloy to the silicon is (0.05-0.3): 1. In one possible embodiment, the lithium silicon alloy includes at least one of Li 4.4Si、Li3.75 Si. In one possible embodiment, the silicon-based composite material has a D50 particle size of 2 μm to 5 μm; and/or the thickness of the coating layer is 3 nm-10 nm; And/or the amorphous carbon material accounts for 2% -6% of the silicon-based composite material by mass, and preferably 2% -4%. In a second aspect, an embodiment of the present application provides a method for preparing the silicon-based composite material, including mixing a lithium silicon alloy with silicon, and then performing a first ball milling in a first inert atmosphere to obtain a silicon-containing nucleus; Placing the silicon-containing nuclear body and a coating agent in a second inert atmosphere, and performing second ball milling at a rotating speed of less than or equal to 1000rpm to obtain a silicon-based composite material precursor; And carrying out vacuum sintering on the precursor of the silicon-based composite material for 1-3 hours at the temperature of more than 273 ℃ to obtain the silicon-based composite material. In one possible embodiment, the D50 particle size of the silicon is 0.1 μm to 4 μm, preferably 0.8 μm to 2 μm; and/or the D50 particle size of the lithium silicon alloy is 0.1-4 mu m, preferably 0.8-2 mu m; And/or the D50 particle size of the lithium silicon alloy is less than or equal to the D50 particle size of the silicon; and/or the ball-to-material ratio of the first ball mill is (15-50): 1; And/or the ball milling rotating speed of the first ball milling is 500-600 rpm, and the ball milling time is 3-5 h; and/or the ball milling ratio of the second ball milling is (15-50): 1; and/or the ball milling time of the second ball mil