Search

CN-121983679-A - Method for improving R angle decarburization of inner ring of high-areal-density winding lithium battery

CN121983679ACN 121983679 ACN121983679 ACN 121983679ACN-121983679-A

Abstract

The invention discloses a method for improving R angle decarburization of an inner ring of a high-surface-density wound lithium battery, which relates to the technical field of lithium ion batteries and comprises the steps of S1, preparing negative electrode slurry, S3, winding a battery core, namely, winding the negative electrode plate, a positive electrode plate and a diaphragm together to form a winding core in a winding tension decreasing mode, wherein the adhesive is compounded by adopting linear polyacrylic acid and styrene-butadiene rubber, the proportion of the adhesive in the negative electrode slurry is 1.5% -2.5%, S2, preparing a negative electrode plate, namely, coating the negative electrode slurry on a current collector, drying and rolling to prepare the negative electrode plate, the compaction density of the negative electrode plate is controlled between 1.45g/cm 3 and 1.52g/cm 3 , and the winding core is wound with the positive electrode plate and the diaphragm in a winding tension decreasing mode.

Inventors

  • ZENG PEIYUAN
  • ZOU ZEXIAN
  • WEI DANDAN
  • WANG XIAOXIAO

Assignees

  • 芜湖天弋能源科技有限公司

Dates

Publication Date
20260505
Application Date
20260127

Claims (9)

  1. 1. A method for improving R-angle decarburization of an inner ring of a high-areal-density wound lithium battery is characterized by comprising the following steps: S1, preparing negative electrode slurry, namely mixing a negative electrode active material, a conductive agent, a binder, a dispersing agent and a solvent to prepare the negative electrode slurry, wherein the binder is compounded by adopting linear polyacrylic acid and styrene-butadiene rubber, and the binder accounts for 1.5% -2.5% of the negative electrode slurry; S2, preparing a negative electrode plate, namely coating negative electrode slurry on a current collector, drying and rolling to obtain the negative electrode plate, wherein the compaction density of the negative electrode plate is controlled between 1.45g/cm 3 and 1.52g/cm 3 ; And S3, winding the battery cell, namely winding the negative electrode plate, the positive electrode plate and the diaphragm together in a winding tension decreasing mode to form a winding core.
  2. 2. The method for improving R-angle decarburization of the inner ring of a high areal density wound lithium battery according to claim 1, wherein in the step S1, the negative electrode slurry preparation method comprises the steps of: (1) Firstly, dry-mixing a negative electrode active material, a dispersing agent and a conductive agent, stirring for 30min at a low speed of 15-20rpm, and realizing preliminary uniform mixing through mechanical friction; (2) Then adding a binder and a part of solvent, controlling the solid content of the slurry to be 66% -68%, and dispersing at 20rpm for 60min to crush large particles in the powder material into small particles; (3) Adding the rest solvent, controlling the solid content of the slurry to be 49% -54%, and dispersing at high speed of 1200-1800rpm for 120min to enable the components to be fully dispersed in water to form stable suspension.
  3. 3. The method for improving R-angle decarburization of an inner ring of a high-areal-density wound lithium battery according to claim 1, wherein the ratio of the negative electrode active material, the conductive agent, the binder, the dispersant and the solvent in the negative electrode slurry is 96.8:0.5:2.2:0.5:100.
  4. 4. The method for improving R-angle decarburization of an inner ring of a high-areal-density wound lithium battery according to claim 1, wherein the ratio of linear polyacrylic acid to styrene-butadiene rubber in the adhesive is 1.7:0.5.
  5. 5. The method for improving R-angle decarburization of an inner ring of a high-areal-density wound lithium battery according to claim 1, wherein the negative electrode active material is graphite and the conductive agent is conductive carbon black.
  6. 6. The method for improving R-angle decarburization of an inner ring of a high-areal-density wound lithium battery according to claim 1, wherein the dispersing agent is sodium carboxymethyl cellulose and the solvent is deionized water.
  7. 7. The method for improving R-angle decarburization of an inner ring of a high-areal-density wound lithium battery according to claim 1, wherein in the step S2, an ultrathin electrolytic copper foil of 5-6 μm is used as a current collector.
  8. 8. The method for improving R-angle decarburization of an inner ring of a high areal density wound lithium battery according to claim 1, wherein in the step S3, the winding tension is decreased in a manner such that the winding tension is linearly decreased from an initial tension value F1 to a value between 0.3F1 and 0.5F1 when the winding is performed to the innermost ring of 5 to 10 turns.
  9. 9. A lithium ion battery prepared by the method of any one of claims 1-8.

Description

Method for improving R angle decarburization of inner ring of high-areal-density winding lithium battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a method for improving R-angle decarburization of an inner ring of a high-surface-density winding lithium battery. Background In the lithium ion battery technology, the improvement of the energy density is one of the core driving forces of the development of the lithium ion battery technology, and the increase of the surface density of the electrode active material is a direct and effective means for improving the volume energy density and the mass energy density of the battery. However, when the areal density increases to a certain critical value (for example, for LFP-C systems, the negative electrode is >195g/m 2), the battery can exhibit a new, serious failure mode in the long-term cycle, especially in the full charge (100% SOC) state, which is characterized in that after the defective cell is disassembled, the arc-shaped transition region (R angle) of the innermost ring (i.e. the winding starting end) of the winding cell can be observed, and the outer side (i.e. the side far from the winding needle) of the pole piece is subjected to large-area active material coating shedding, and for graphite negative electrodes, the phenomenon is decarburization. This problem not only results in a sharp decay in capacity, but also causes serious safety hazards due to the possibility of internal short circuits caused by exposed current collectors. The prior art generally seeks improvements from a single perspective, such as fine tuning the amount of binder, optimizing the rolling process, or adjusting the winding tension. However, through intensive research and mechanism analysis, it is found that the problem of R-angle decarburization under high areal density is caused by mismatch of mechanical properties of the pole piece and mechanical stress in the battery cell. The failure principle is that the thickness and rigidity of the pole piece are obviously increased due to the increase of the density, when the pole piece is fully charged, the graphite cathode is greatly expanded (more than 10 percent) to cause the whole winding core to generate huge radial expansion force, the expansion of the outer pole piece is inwards extruded, a bending moment for trying to prop open the innermost pole piece is generated, the curvature radius of the inner pole piece is forced to be increased, in the process, the outer side surface coating of the inner ring R angle bears extremely large circumferential tensile stress, the tensile strength of the coating and the bonding force of the coating and a current collector are exceeded in the traditional design, and finally the coating is subjected to brittle fracture or interfacial peeling, so that the method for improving the decarburization of the inner ring R angle of the high-surface-density winding lithium battery is provided. Disclosure of Invention The invention aims to solve the decarburization problem of the outer side of the R angle of the inner ring of a high-surface-density electrode during full charge, so that the energy density of a battery is effectively improved on the premise of not sacrificing the safety and the service life, and provides a method for improving the decarburization of the R angle of the inner ring of a high-surface-density wound lithium battery. A method for improving R-angle decarburization of an inner ring of a high-areal-density wound lithium battery comprises the following steps: S1, preparing negative electrode slurry, namely mixing a negative electrode active material, a conductive agent, a binder, a dispersing agent and a solvent to prepare the negative electrode slurry, wherein the binder is compounded by adopting linear polyacrylic acid and styrene-butadiene rubber, and the binder accounts for 1.5% -2.5% of the negative electrode slurry; S2, preparing a negative electrode plate, namely coating negative electrode slurry on a current collector, drying and rolling to obtain the negative electrode plate, wherein the compaction density of the negative electrode plate is controlled between 1.45g/cm 3 and 1.52g/cm 3; And S3, winding the battery cell, namely winding the negative electrode plate, the positive electrode plate and the diaphragm together in a winding tension decreasing mode to form a winding core. Preferably, in the step S1, the method for preparing the negative electrode slurry includes: (1) Firstly, dry-mixing a negative electrode active material, a dispersing agent and a conductive agent, stirring for 30min at a low speed of 15-20rpm, and realizing preliminary uniform mixing through mechanical friction; (2) Then adding a binder and a part of solvent, controlling the solid content of the slurry to be 66% -68%, and dispersing at 20rpm for 60min to crush large particles in the powder material into small particles; (3) Adding the rest solvent,