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CN-122025553-A - Negative plate and preparation method thereof

CN122025553ACN 122025553 ACN122025553 ACN 122025553ACN-122025553-A

Abstract

The application provides a negative plate and a preparation method thereof. The negative electrode sheet comprises an electrode foil. One side surface of the electrode foil is sequentially provided with a large-particle-size graphite layer, a silicon-carbon material layer and a small-particle-size graphite layer, wherein the silicon-carbon material layer at least comprises silicon-carbon particles and a tubular rod-shaped conductive agent. The tubular rod-shaped conductive agent at least partially protrudes from the silicon-carbon material layer and is embedded in the large-particle-diameter graphite layer, and the tubular rod-shaped conductive agent at least partially protrudes from the small-particle-diameter graphite layer. The negative plate can realize stable production with low surface density and expansion inhibition in battery circulation.

Inventors

  • XIONG JIAN
  • HU DALIN
  • LIAO XINGQUN

Assignees

  • 深圳市豪鹏科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260126

Claims (10)

  1. 1. The negative electrode sheet comprises an electrode foil and is characterized in that a large-particle-size graphite layer, a silicon-carbon material layer and a small-particle-size graphite layer are sequentially arranged on one side surface of the electrode foil, and the silicon-carbon material layer at least comprises silicon-carbon particles and a tubular rod-shaped conductive agent; Wherein the tubular rod-shaped conductive agent at least partially protrudes from the silicon carbon material layer and is embedded in the large-particle-diameter graphite layer, and the tubular rod-shaped conductive agent at least partially protrudes from the small-particle-diameter graphite layer.
  2. 2. The negative electrode sheet according to claim 1, wherein the tubular rod-shaped conductive agent is at least partially embedded in the large-particle-diameter graphite layer and the small-particle-diameter graphite layer protruding from the silicon carbon material layer, respectively, and, The tubular rod-shaped conductive agent at least partially protrudes from the silicon-carbon material layer and is embedded in the large-particle-size graphite layer, and the tubular rod-shaped conductive agent at least partially protrudes from the silicon-carbon material layer and is embedded in the small-particle-size graphite layer.
  3. 3. The negative electrode sheet according to claim 1, wherein the length of the tubular rod-shaped conductive agent is > twice the particle diameter D50 of the silicon carbon particles, and/or, The tubular and rod-shaped conductive agent is an array carbon nano tube and/or vapor grown carbon fiber and/or, The particle diameter D50 of the silicon carbon particles is 6-15 mu m.
  4. 4. The negative electrode sheet according to claim 1, wherein the large particle size graphite layer has an areal density of 10g/m 2 ~30g/m 2 , and/or, The areal density of the silicon carbon material layer is 5g/m 2 ~30g/m 2 , and/or, The surface density of the small-particle-size graphite layer is 15g/m 2 ~30g/m 2 .
  5. 5. The negative electrode sheet according to claim 1, wherein the large particle size graphite layer has an areal density of more than 1/2 of the areal density of the silicon carbon material layer, and/or, The surface density of the small-particle-size graphite layer is greater than 1/2 of the surface density of the silicon carbon material layer.
  6. 6. The negative electrode sheet according to claim 1, wherein the large-particle-diameter graphite layer comprises the following components in parts by mass: 80-99.8 parts of large-particle-size graphite; 0.1-10 parts of a first conductive agent; 0.1 to 10 parts of a first binder, and, The small-particle-size graphite layer comprises the following components in parts by mass: 80-99.8 parts of small-particle-size graphite; 0.1-10 parts of a second conductive agent; and 0.1-10 parts of a second binder.
  7. 7. The negative electrode sheet according to claim 6, wherein the large particle size graphite has a particle size D50 of 10 μm or more and/or, The graphitization degree of the large-particle-size graphite is more than 95 percent and/or, The particle size D50 of the small particle size graphite is less than or equal to 12 mu m, and/or, The graphitization degree of the small-particle-size graphite is less than 92 percent and/or, The large particle size graphite has a compaction density of >1.90g/cm 3 at 5T pressure, and/or, The silicon carbon particles have a compaction density of >1.00g/cm 3 at a 5T pressure, and/or, The small particle size graphite has a compaction density of <1.80g/cm 3 at 5T pressure.
  8. 8. The negative electrode sheet according to claim 6, wherein the large particle size graphite has a particle size D50> the particle size D50 of the silicon carbon particles, and/or, The particle diameter D50 of the silicon carbon particles is greater than the particle diameter D50 of the small particle diameter graphite.
  9. 9. The negative electrode sheet according to claim 6, wherein the large particle size graphite is natural graphite or calcined coke artificial graphite, and/or, The first conductive agent is at least one of carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, conductive graphite, vapor phase generated carbon fibers and graphene, and/or, The first binder is at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, styrene-butadiene rubber and polyurethane, and/or, The small-particle-size graphite is raw coke artificial graphite and/or, The second conductive agent is at least one of carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, conductive graphite, vapor phase generated carbon fibers and graphene, and/or, The second binder is at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, polyacrylate and polyacrylonitrile.
  10. 10. A method for preparing a negative electrode sheet according to any one of claims 1 to 9, characterized in that the method for preparing a negative electrode sheet comprises the steps of: Obtaining an electrode foil; Performing a first graphite coating operation on the electrode foil so that a large-particle-diameter graphite wet film layer is formed on one side surface of the electrode foil; Spraying the large-particle-size graphite wet film so that a silicon-carbon material layer is formed on one side surface, far away from the electrode foil, of the large-particle-size graphite wet film, microetching and melting are carried out between the silicon-carbon material layer and the contact surface of the large-particle-size graphite wet film, and the tubular rod-shaped conductive agent at least partially protrudes out of the silicon-carbon material layer and is embedded in the large-particle-size graphite wet film; And performing a second graphite coating operation on the silicon carbon material layer so that a small-particle-size graphite layer is formed on the silicon carbon material layer, and the tubular rod-shaped conductive agent at least partially protrudes into the small-particle-size graphite layer.

Description

Negative plate and preparation method thereof Technical Field The invention relates to the technical field of batteries, in particular to a negative plate and a preparation method thereof. Background In recent years, along with rapid development and popularization of the technology of the new generation of vapor deposition silicon carbon materials, the silicon carbon negative electrode material is applied to various consumer lithium ion batteries. However, the silicon negative electrode is accompanied by about 300% of volume expansion in the lithium intercalation process, so that the silicon carbon negative electrode still faces huge expansion in the circulation process, and meanwhile, the silicon carbon negative electrode also has the problems of low areal density coating particle scribing and the like in the negative electrode sheet manufacturing process. Therefore, in the process of popularization and application, the problem of expansion inhibition in the process of low-surface-density stable production and battery circulation is needed to be solved. Disclosure of Invention The invention aims to overcome the defects in the prior art and provide a negative plate capable of realizing stable production with low surface density and expansion inhibition in battery circulation and a preparation method thereof. The aim of the invention is realized by the following technical scheme: The negative electrode sheet comprises an electrode foil, wherein a large-grain-diameter graphite layer, a silicon-carbon material layer and a small-grain-diameter graphite layer are sequentially arranged on one side surface of the electrode foil, and the silicon-carbon material layer at least comprises silicon-carbon particles and a tubular rod-shaped conductive agent; Wherein the tubular rod-shaped conductive agent at least partially protrudes from the silicon carbon material layer and is embedded in the large-particle-diameter graphite layer, and the tubular rod-shaped conductive agent at least partially protrudes from the small-particle-diameter graphite layer. In one embodiment, the tubular rod-shaped conductive agent is at least partially embedded in the large-particle-size graphite layer and the small-particle-size graphite layer protruding from the silicon carbon material layer, respectively, and, The tubular rod-shaped conductive agent at least partially protrudes from the silicon-carbon material layer and is embedded in the large-particle-size graphite layer, and the tubular rod-shaped conductive agent at least partially protrudes from the silicon-carbon material layer and is embedded in the small-particle-size graphite layer. In one embodiment, the length of the tubular rod-shaped conductive agent is > twice the particle diameter D50 of the silicon carbon particles. In one embodiment, the tubular and rod-shaped conductive agent is an array of carbon nanotubes and/or vapor grown carbon fibers. In one embodiment, the particle diameter D50 of the silicon carbon particles is 6-15 μm. In one embodiment, the large particle size graphite layer has an areal density of 10g/m 2~30g/m2. In one embodiment, the areal density of the silicon carbon material layer is 5g/m 2~30g/m2. In one embodiment, the small particle size graphite layer has an areal density of 15g/m 2~30g/m2. In one embodiment, the areal density of the large particle size graphite layer is greater than 1/2 the areal density of the silicon carbon material layer. In one embodiment, the small particle size graphite layer has an areal density greater than 1/2 the areal density of the silicon carbon material layer. In one embodiment, the large-particle-size graphite layer comprises the following components in parts by mass: 80-99.8 parts of large-particle-size graphite; 0.1-10 parts of a first conductive agent; 0.1-10 parts of a first binder. In one embodiment, the small-particle-size graphite layer comprises the following components in parts by mass: 80-99.8 parts of small-particle-size graphite; 0.1-10 parts of a second conductive agent; and 0.1-10 parts of a second binder. In one embodiment, the particle size D50 of the large particle size graphite is not less than 10 μm. In one embodiment, the large particle size graphite has a graphitization degree of >95%. In one embodiment, the small particle size graphite has a particle size D50 of 12 μm or less. In one embodiment, the small particle size graphite has a graphitization degree of <92%. In one embodiment, the large particle size graphite has a compacted density >1.90g/cm 3 at 5T pressure. In one embodiment, the silicon carbon particles have a compaction density of >1.00g/cm 3 at 5T pressure. In one embodiment, the small particle size graphite has a compaction density of <1.80g/cm 3 at 5T pressure. In one embodiment, the particle size D50 of the large particle size graphite > the particle size D50 of the silicon carbon particles. In one embodiment, the silicon carbon particles have a particle size D50> the particle size