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CN-119812264-B - Silicon-carbon negative electrode material, preparation method thereof, secondary battery and electric equipment

CN119812264BCN 119812264 BCN119812264 BCN 119812264BCN-119812264-B

Abstract

The application provides a silicon-carbon negative electrode material, a preparation method thereof, a secondary battery and electric equipment. The silicon-carbon anode material comprises carbon fibers and carbon-coated silicon particles positioned in the carbon fibers, wherein the carbon fibers are mutually overlapped to form a layered porous network structure, the silicon-carbon anode material meets the following relational expression that 4<a multiplied by c is less than 15, a cm ‑1 is half-width of a G peak of the silicon-carbon anode material in a Raman spectrum, b is a ratio of D peak intensity to G peak intensity in the Raman spectrum of the silicon-carbon anode material, and c is Poisson's ratio of the silicon-carbon anode material. According to the application, the structure of the silicon-carbon negative electrode is designed, after silicon is coated with carbon, the carbon fibers are embedded into the carbon fibers, and the carbon fibers are further lapped to form a layered film-shaped structure with a porous net shape, meanwhile, the parameters of the silicon-carbon negative electrode material are reasonably controlled to meet a specific relational expression, so that the volume expansion of the material can be effectively relieved, the conductivity of the material is improved, and the cycle performance and the multiplying power performance are improved.

Inventors

  • WU JIZHE

Assignees

  • 欣旺达动力科技股份有限公司

Dates

Publication Date
20260508
Application Date
20241227

Claims (8)

  1. 1. The silicon-carbon negative electrode material is characterized by comprising carbon fibers and carbon-coated silicon particles positioned in the carbon fibers, wherein the carbon fibers are mutually overlapped to form a layered porous network structure, the weight ratio of silicon is 2-15% based on the silicon-carbon negative electrode material, the weight ratio of the carbon fibers is 35-78%, the weight ratio of a carbon coating layer in the carbon-coated silicon particles is 20-50%, and the silicon-carbon negative electrode material meets the following relation: 4<a×b×c<15; acm -1 is the half-width of the G peak of the silicon-carbon anode material in a Raman spectrum, and the half-width meets the requirement of 10cm -1 ≤a≤25cm -1 ; b is the ratio of the intensity of the D peak to the intensity of the G peak in the Raman spectrum of the silicon-carbon anode material, and b is more than or equal to 0.6 and less than or equal to 1.5; c is the Poisson ratio of the silicon-carbon anode material, and 0<c is less than or equal to 0.5.
  2. 2. The silicon-carbon negative electrode material of claim 1, wherein the silicon-carbon negative electrode material has a D peak with a peak position of 1300cm -1 ~1380cm -1 in raman spectroscopy.
  3. 3. The silicon-carbon negative electrode material according to claim 1, wherein the G peak of the silicon-carbon negative electrode material has a peak-out position of 1520cm -1 ~1590cm -1 in raman spectrum.
  4. 4. A method for preparing a silicon-carbon anode material according to any one of claims 1 to 3, comprising the steps of: Uniformly mixing a silicon source and a first carbon source in a solvent, adding a second carbon source, uniformly mixing to form a colloid precursor solution, and preparing the silicon-carbon anode material after electrostatic spinning film forming and carbonization of the colloid precursor solution; The first carbon source is a polar carbon-containing macromolecule to form a carbon coating layer in the carbon-coated silicon particles, and the second carbon source is a precursor polymer for forming carbon fibers.
  5. 5. The method of claim 4, wherein the first carbon source comprises at least one of epoxy, cellulose, polyvinylidene fluoride.
  6. 6. The method of claim 4, wherein the second carbon source comprises at least one of polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylonitrile.
  7. 7. A secondary battery comprising a positive electrode sheet, an electrolyte, a separator and a negative electrode sheet, wherein the negative electrode sheet comprises the silicon-carbon negative electrode material according to any one of claims 1 to 3.
  8. 8. A powered device comprising the secondary battery of claim 7.

Description

Silicon-carbon negative electrode material, preparation method thereof, secondary battery and electric equipment Technical Field The application relates to the technical field of negative electrode materials, in particular to a silicon-carbon negative electrode material, a secondary battery and electric equipment. Background Lithium ion secondary batteries are the main energy storage devices in the new energy field today. The problem of low capacity of carbon materials as the main commercial negative electrode has limited the development of lithium ion secondary batteries. The silicon cathode has the highest theoretical specific capacity, but the volume expansion of the silicon cathode is up to 300 percent in the charge and discharge process, the intrinsic conductivity of the silicon is low, the huge volume effect in the charge and discharge process can cause the collapse of the electrode material structure and even the stripping from a current collector, so that the electrochemical performance is deteriorated, and the electrode structure of the traditional coating method comprises inert components with very large specific gravity, such as a metal current collector, a conductive agent, a binder and the like, so that the weight of the battery is improved, and the internal resistance is increased. Therefore, modification and rational design of the negative electrode material of the secondary battery are required to improve the overall properties of the secondary battery, such as conductivity, cycle performance, and rate performance. Disclosure of Invention The purpose of the present application is to provide a secondary battery that has excellent cycle performance and rate performance. In order to achieve the above object, according to a first aspect of the present application, there is provided a silicon-carbon negative electrode material comprising carbon fibers and carbon-coated silicon particles located inside the carbon fibers, wherein the carbon fibers are overlapped with each other to form a layered porous network structure, and the silicon-carbon negative electrode material satisfies the following relationship: 4<a×b×c<15; wherein, a cm -1 is half-width of a G peak of the silicon-carbon anode material in a Raman spectrum; b is the ratio of the D peak intensity to the G peak intensity in the Raman spectrum of the silicon-carbon anode material; c is the Poisson ratio of the silicon-carbon anode material. As an embodiment of the application, the peak outlet position of the D peak of the silicon-carbon anode material in the raman spectrum is 1300cm -1～1380cm-1. As an embodiment of the application, the peak position of the G peak of the silicon-carbon anode material in the raman spectrum is 1520cm -1～1590cm-1. As an embodiment of the application, the silicon carbon negative electrode material satisfies 10cm -1≤a≤25cm-1. As an embodiment of the application, the silicon-carbon anode material satisfies that b is more than or equal to 0.6 and less than or equal to 1.5. As an embodiment of the application, the silicon-carbon anode material meets 0<c less than or equal to 0.5. According to the embodiment of the application, the silicon accounts for 2-15% of the weight of the silicon-carbon anode material. According to the embodiment of the application, based on the silicon-carbon anode material, the weight ratio of the carbon fiber is 35-78%. According to the embodiment of the application, based on the silicon-carbon anode material, the weight ratio of the carbon coating layer in the carbon-coated silicon particles is 20-50%. The second aspect of the application also provides a preparation method of the silicon-carbon anode material of the first aspect of the application, which comprises the following steps: Uniformly mixing a silicon source and a first carbon source in a solvent, adding a second carbon source, uniformly mixing to form a colloid precursor solution, and preparing the silicon-carbon anode material after electrostatic spinning film forming and carbonization of the colloid precursor solution; The first carbon source is a polar carbon-containing macromolecule to form a carbon coating layer in the carbon-coated silicon particles, and the second carbon source is a precursor polymer for forming carbon fibers. As an embodiment of the present application, the first carbon source includes at least one of epoxy resin, cellulose, polyvinylidene fluoride. As an embodiment of the present application, the second carbon source includes at least one of polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylonitrile. In a third aspect of the present application, there is provided a secondary battery comprising a positive electrode tab, an electrolyte, a separator, and a negative electrode tab comprising a negative electrode current collector and a negative electrode active material layer comprising the silicon-carbon negative electrode material according to the first aspect of the present application disposed on at