Search

CN-122025834-A - Secondary battery, separator and electricity utilization device

CN122025834ACN 122025834 ACN122025834 ACN 122025834ACN-122025834-A

Abstract

The application relates to the technical field of batteries, in particular to a secondary battery, a diaphragm and an electric device. The secondary battery comprises a positive electrode plate, a negative electrode plate and a diaphragm, wherein the diaphragm comprises a base film, a surface coating is arranged on one side of the base film facing the negative electrode plate, and a gap is formed on the surface of one side of the surface coating facing the negative electrode plate. The diaphragm comprises the base film, a surface coating is arranged on one side of the base film facing the negative electrode plate, a gap is formed on one side surface of the surface coating facing the negative electrode plate, the gap provides a space for deposition of metal on the negative electrode side, the risk of cell expansion caused by deposition of active ions on the negative electrode is reduced, and the cycle performance of the battery is improved.

Inventors

  • PAN JIANFU
  • XU XIAOFU
  • LI XIAO
  • YE YONGHUANG

Assignees

  • 宁德时代新能源科技股份有限公司

Dates

Publication Date
20260512
Application Date
20241111

Claims (20)

  1. 1. A secondary battery, characterized in that the secondary battery comprises a positive electrode piece, a negative electrode piece and a diaphragm; The diaphragm comprises a base film, a surface coating is arranged on one side of the base film, facing the negative electrode plate, and a gap is formed in the surface of one side of the surface coating, facing the negative electrode plate.
  2. 2. The secondary battery according to claim 1, wherein the particles in the topcoat layer have a particle diameter Dv50 of 13 μm to 30 μm.
  3. 3. The secondary battery according to claim 1 or 2, wherein the particles in the topcoat have a particle diameter Dv50 of d in μm; The positive electrode plate comprises a positive electrode current collector and a positive electrode coating arranged on at least one surface of the positive electrode current collector, wherein the capacity of a positive electrode active material per unit area of one surface of the positive electrode coating is Q, and the unit is Ah/m 2 ; d and Q are 0.6Q-d-1.9Q.
  4. 4. The secondary battery according to any one of claims 1 to 3, wherein the morphology of the particles in the topcoat comprises at least one of spheres, spheroids, islands, pillars.
  5. 5. The secondary battery according to any one of claims 1 to 4, wherein the material of the particles in the topcoat layer comprises an organic polymer and/or an inorganic material.
  6. 6. The secondary battery according to any one of claims 1 to 5, wherein the particles in the topcoat are a binder.
  7. 7. The secondary battery according to claim 6, wherein the mass of the binder per unit area in the topcoat is 0.4g/m 2 to 1.8g/m 2 ; and/or the material of the binder comprises at least one of polyvinylidene fluoride, polyethylene, styrene-butadiene rubber, polymethyl acrylate, sodium carboxymethyl cellulose and polyacrylic acid.
  8. 8. The secondary battery according to any one of claims 1 to 7, wherein an undercoat layer is further provided between the base film and the topcoat layer.
  9. 9. The secondary battery according to claim 8, wherein the primer layer includes ceramic particles therein; And/or, the primer layer includes binder particles therein.
  10. 10. The secondary battery according to claim 8 or 9, wherein the mass percentage of the ceramic particles in the undercoat layer is 30% to 70% based on the total mass of the undercoat layer; And/or the particles in the undercoat layer have a particle diameter Dv50 of 0.01 μm to 2.0 μm; And/or the material of the ceramic particles comprises at least one of aluminum oxide, boehmite, silicon dioxide, titanium dioxide and zirconium dioxide; And/or, the primer layer has a single-sided thickness of 0.5 μm to 3.0 μm.
  11. 11. The secondary battery according to any one of claims 1 to 10, wherein the compression ratio of the separator is T1, satisfying 12% to T1 to 22%.
  12. 12. The secondary battery according to any one of claims 1 to 11, wherein the initial thickness of the base film is H, satisfying 6 μm≤h≤25 μm.
  13. 13. The secondary battery according to any one of claims 1 to 12, wherein an initial thickness H of the base film, a compression ratio T1 of the separator, and a capacity Q of a positive electrode active material per unit area of one surface of the positive electrode coating layer in the positive electrode sheet satisfy 0.6 Q≤H2xT1≤1.9Q.
  14. 14. The secondary battery according to any one of claims 1 to 13, wherein the material of the base film includes at least one of polyethylene, polypropylene, nonwoven fabric, and polyimide; And/or the porosity of the base film is 30% to 70%.
  15. 15. The secondary battery according to any one of claims 1 to 14, wherein the secondary battery is a metal battery.
  16. 16. The secondary battery of claim 15, wherein the metal battery comprises a lithium metal battery, a sodium metal battery, an aluminum metal battery, a zinc metal battery; And/or the secondary battery comprises a laminated battery, a square battery, a cylindrical battery and a soft package battery.
  17. 17. A separator, characterized in that the separator comprises a base film, at least one side of the base film is provided with a surface coating, and the surface of the surface coating is provided with gaps.
  18. 18. The separator of claim 17, wherein the particles in the topcoat have a particle size Dv50 of 13 μm to 30 μm.
  19. 19. The separator of claim 17 or 18, wherein the morphology of the particles in the topcoat comprises at least one of spheres, spheroids, islands, columns; and/or, the particles in the surface coating are binders.
  20. 20. The separator of claim 19, wherein the mass of binder per unit area in the topcoat is from 0.4g/m 2 to 1.8g/m 2 ; and/or the material of the binder comprises at least one of polyvinylidene fluoride, polyethylene, styrene-butadiene rubber, polymethyl acrylate, sodium carboxymethyl cellulose and polyacrylic acid.

Description

Secondary battery, separator and electricity utilization device Technical Field The invention relates to the technical field of batteries, in particular to a secondary battery, a diaphragm and an electric device. Background Secondary batteries, such as lithium ion batteries, have been attracting attention due to their high specific energy, long cycle life, low self-discharge, good safety, etc., and currently, lithium ion battery applications have been in progress in everyday life, such as cameras, notebook computers, electric vehicles, etc. In some cases, the secondary battery may undergo a phenomenon of volume expansion during the cycle, thus degrading the cycle performance of the battery. Disclosure of Invention The main object of the present application is to provide a secondary battery, which aims to improve the cycle performance of the secondary battery. In order to achieve the above object, the present application provides a secondary battery, which includes a positive electrode tab, a negative electrode tab, and a separator; The diaphragm comprises a base film, a surface coating is arranged on one side of the base film, facing the negative electrode plate, and a gap is formed in the surface of one side of the surface coating, facing the negative electrode plate. The diaphragm comprises the base film, a surface coating is arranged on one side of the base film facing the negative electrode plate, a gap is formed on one side surface of the surface coating facing the negative electrode plate, the gap provides a space for deposition of metal on the negative electrode side, the risk of cell expansion caused by deposition of active ions on the negative electrode is reduced, and the cycle performance of the battery is improved. It can be understood that the metal on the negative side needs space for growth during the deposition process, if the deposition space is insufficient, the deposited metal can cause expansion of the battery, for example, the metal on the negative side can form a deposition layer between the negative electrode and the diaphragm to squeeze the diaphragm due to insufficient deposition space, the metal dendrite in the deposition layer can easily cause the risk of puncturing the diaphragm to generate positive and negative short circuit due to the extrusion force on the diaphragm, or the deposition layer can generate larger extrusion stress on the diaphragm, so that the diaphragm transits and extrudes, the permeability of active ions in the diaphragm is reduced, the internal resistance of the battery is increased, the cycle performance of the battery is further influenced, in order to alleviate the problems, a surface coating layer is arranged on the side of the base film facing the negative electrode plate, and the surface of the surface coating layer facing the negative electrode plate is provided with a gap for metal deposition, so that the risk of expanding the battery core caused by deposition of active ions on the negative electrode is reduced, and the cycle performance of the battery is improved. Alternatively, the particles in the topcoat have a particle size Dv50 of 13 μm to 30 μm. It is understood that gaps exist between particles, and as the size of the particles increases, the gaps between the particles also increase, and the particle size of the particles in the surface coating layer is arranged on the surface of the surface coating layer to form gaps, so that the particle size of the particles can influence the size of the gaps. The particle size of the particles in the surface coating meets the range, which is beneficial to providing more gaps for the growth of metal on the negative electrode side and is beneficial to the uniform deposition of metal. It will be appreciated that non-uniform deposition of the metal on the negative side will more likely cause the growth of longer dendrites and thus the risk of shorting by the separator being pierced, and that the appropriate particle size in the topcoat of the present application will reduce the risk of shorting of the battery. Optionally, the particles in the topcoat have a particle size Dv50 d in μm; the positive electrode plate comprises a positive electrode current collector and a positive electrode coating arranged on at least one surface of the positive electrode current collector, wherein the capacity of a positive electrode active material per unit area of one surface of the positive electrode coating is Q, and the unit is mAh/m 2; d and Q are 0.6Q-d-1.9Q. It will be appreciated that the capacity of the positive electrode side determines the space in which the metal on the negative electrode side grows, for example, under certain conditions, the more active ions are provided on the positive electrode side, the more metal is deposited on the negative electrode side, and at the same time, the particle size in the coating layer influences the size of the gap for metal growth, that is, the particle size Dv50 of the particles