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CN-121983672-A - Preparation method for improving deformation of lithium ion battery with silicon-carbon negative electrode

CN121983672ACN 121983672 ACN121983672 ACN 121983672ACN-121983672-A

Abstract

The invention discloses a preparation method for improving deformation of a lithium ion battery with a silicon-carbon negative electrode. According to the method, the chemical expansion rate x of the silicon carbon material and the physical expansion rate y of the graphite material are cooperatively regulated and controlled in the negative electrode formula and process, so that the deformation coefficient Z (Z=x/y) is in an engineering optimization interval, and the probability of appearance deformation of a crescent or S shape of the square battery cell in the pressure formation and subsequent processes is obviously reduced. The method comprises the steps of preparing positive electrode slurry, coating the positive electrode slurry on an aluminum foil, preparing negative electrode slurry containing silicon carbon and graphite, and manufacturing a lithium battery, wherein Z is in a range of 2-4 by selecting silicon carbon and graphite materials in the design of a negative electrode formula, so that the appearance qualification rate and the production yield of a finished product are improved on the premise of keeping electrochemical performance.

Inventors

  • PAN DEMIAO
  • ZHANG JUAN
  • ZHAO MINGCAI
  • DUAN KANGKANG
  • MA NA

Assignees

  • 浙江载驰科技股份有限公司

Dates

Publication Date
20260505
Application Date
20251226

Claims (10)

  1. 1. A method for improving deformation of a square lithium ion battery having a silicon-carbon negative electrode, comprising: a) Preparing a positive plate, namely mixing a positive active material, a conductive agent, a binder and a solvent to form positive slurry, coating the positive slurry on a positive current collector, and drying to obtain the positive plate; B) Preparing a negative plate, namely mixing a silicon-carbon active material, a graphite active material, a conductive agent, a binder and a solvent to form negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector, and drying to obtain the negative plate; c) Assembling the positive plate and the negative plate to form a square battery cell and filling liquid for packaging; D) Performing pressure formation on the square battery cell and completing subsequent aging treatment to obtain a finished square lithium ion battery; The chemical expansion rate of the silicon-carbon active material in the negative plate is x, the physical expansion rate of the graphite active material is y, the deformation coefficient Z=x/y is defined, and the silicon-carbon active material and the graphite active material are selected to enable Z to be in a range of 2-4, so that the probability of 'crescent' or 'S' -shaped deformation of the square battery after pressure formation is reduced.
  2. 2. The method of claim 1, wherein Z = 2.0-3.0.
  3. 3. The method of claim 1, wherein the silicon carbon active material has a chemical expansion x of 10% to 35% and/or the graphite active material has a physical expansion y of 3% to 15%.
  4. 4. The method of claim 1, wherein the silicon carbon active material has a mass fraction of 2 to 20wt% and the graphite active material has a mass fraction of 80 to 98wt%, based on the total mass of the negative electrode active material; The negative electrode conductive agent comprises one or more of Super-P, acetylene black, KS-6 and carbon nano tubes, and the mass fraction of the negative electrode conductive agent is 0.5-3.0wt%; the negative electrode binder comprises one or more combinations of SBR, CMC, PAA, and the mass fraction of the negative electrode binder is 1.0-6.0wt%.
  5. 5. The method of claim 1, wherein the positive electrode active material comprises a nickel cobalt lithium manganate material, the positive electrode binder comprises PVDF, the positive electrode conductive agent comprises carbon nanotubes and/or conductive carbon black, and the mass fraction of the positive electrode conductive agent is 0.5-5.0wt%; the positive current collector is aluminum foil, and the negative current collector is copper foil.
  6. 6. The method of claim 1, wherein the positive plate has a double-sided density of 280-340g/m 2 , the negative plate has a double-sided density of 120-180g/m 2 , the positive plate has a compacted density of 3.3-3.9g/cm 3 , and the negative plate has a compacted density of 1.2-1.8g/cm 3 .
  7. 7. The method of claim 1, wherein the pressure forming is performed under conditions that apply an external confining pressure to the prismatic cell, the external confining pressure being between 0.05 MPa and 2.0MPa.
  8. 8. The method of claim 1, wherein the aging treatment comprises high temperature resting at a temperature of 35-60 ℃ and/or high temperature aging at a temperature of 60-90 ℃.
  9. 9. The square lithium ion battery is characterized by comprising a positive plate, a diaphragm and a negative plate, wherein the negative plate comprises a silicon-carbon active material and a graphite active material, the chemical expansion rate of the silicon-carbon active material is x, the physical expansion rate of the graphite active material is y, a deformation coefficient Z=x/y is defined, and the Z=2-4.
  10. 10. The prismatic lithium ion battery of claim 9, wherein Z = 2.0-3.0.

Description

Preparation method for improving deformation of lithium ion battery with silicon-carbon negative electrode Technical Field The invention relates to a preparation method for improving deformation of a lithium ion battery with a silicon-carbon negative electrode, and belongs to the technical field of lithium battery manufacturing. Background The square lithium ion battery is an important component of the lithium ion battery and is mainly applied to the fields of 3C digital codes, two-wheel vehicles and the like. Due to the increasing energy density requirements of the market, conventional battery material systems have failed to meet current market demands. The silicon carbon negative electrode material has ultrahigh theoretical specific capacity (for example, the theoretical specific capacity of a simple substance silicon is 4200 mAh.g -1) and a lower discharge platform (0.1V), but has the problems of low conductivity, poor rate capability and the like, and simultaneously, larger volume expansion can be generated in the charge and discharge process, so that the electrode material is pulverized and falls off, and the application of the electrode material in square lithium ion batteries is limited. In recent years, the technology is continuously innovated, the problems of conductivity, expansion rate and the like of the silicon carbon negative electrode material are greatly optimized, but the chemical expansion rate of the silicon carbon material is still quite different from that of the traditional graphite, the probability of deformation of the internal battery caused by larger chemical expansion in the actual use process is greatly improved, and the promotion of the silicon carbon negative electrode in the square lithium ion battery field is seriously hindered. Disclosure of Invention The invention aims to provide a preparation method for improving deformation of a square lithium ion battery with a silicon carbon negative electrode, aiming at the problems that the deformation of the battery is easy to occur when a nickel cobalt lithium manganate positive electrode is used for coupling a silicon carbon negative electrode material in the conventional square lithium ion battery. A method of manufacturing for improving the deformation of a square lithium ion battery having a silicon carbon negative electrode, comprising: a) Preparing a positive plate, namely mixing a positive active material, a conductive agent, a binder and a solvent to form positive slurry, coating the positive slurry on a positive current collector, and drying to obtain the positive plate; B) Preparing a negative plate, namely mixing a silicon-carbon active material, a graphite active material, a conductive agent, a binder and a solvent to form negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector, and drying to obtain the negative plate; c) Assembling the positive plate and the negative plate to form a square battery cell and filling liquid for packaging; D) Performing pressure formation on the square battery cell and completing subsequent aging treatment to obtain a finished square lithium ion battery; The chemical expansion rate of the silicon-carbon active material in the negative plate is x, the physical expansion rate of the graphite active material is y, the deformation coefficient Z=x/y is defined, and the silicon-carbon active material and the graphite active material are selected to enable Z to be in a range of 2-4, so that the probability of 'crescent' or 'S' -shaped deformation of the square battery after pressure formation is reduced. The z=2.0-3.0. The chemical expansion rate x of the silicon carbon active material is 10% -35%, and/or the physical expansion rate y of the graphite active material is 3% -15%. Based on the total mass of the anode active material, the mass fraction of the silicon-carbon active material is 2-20wt%, and the mass fraction of the graphite active material is 80-98wt%; The negative electrode conductive agent comprises one or more of Super-P, acetylene black, KS-6 and carbon nano tubes, and the mass fraction of the negative electrode conductive agent is 0.5-3.0wt%; the negative electrode binder comprises one or more combinations of SBR, CMC, PAA, and the mass fraction of the negative electrode binder is 1.0-6.0wt%. The positive electrode active material comprises nickel cobalt lithium manganate material, the positive electrode binder comprises PVDF, the positive electrode conductive agent comprises carbon nano tubes and/or conductive carbon black, and the mass fraction of the positive electrode conductive agent is 0.5-5.0wt%; the positive current collector is aluminum foil, and the negative current collector is copper foil. The double-sided density of the positive plate is 280-340g/m 2, the double-sided density of the negative plate is 120-180g/m 2, the compacted density of the positive plate is 3.3-3.9g/cm 3, and the compacted density of the negative pl