CN-122000288-A - Negative plate, preparation method and battery

CN122000288ACN 122000288 ACN122000288 ACN 122000288ACN-122000288-A

Abstract

The invention provides a negative plate, a preparation method and a battery, wherein the negative plate comprises a negative current collector, an active material layer is arranged on the surface of the negative current collector, the active material layer comprises a negative active material, a conductive agent, a binder and a conductive polymer layer, the conductive polymer layer is formed on the surfaces of the negative active material and the conductive agent and forms a continuous surface, the conductive polymer layer comprises 3, 4-ethylenedioxythiophene and sodium polystyrene sulfonate, the conductive polymer layer can effectively stabilize the interface between the negative electrode and electrolyte, inhibit side reaction of the electrolyte or growth of metal dendrites, prolong the cycle life of the battery, and the sodium polystyrene sulfonate is water-soluble, so that a 3, 4-ethylenedioxythiophene and sodium polystyrene sulfonate compound can be stably dispersed in water and effectively deposited on the surfaces of the adjacent negative active material and the conductive agent, and the conductive polymer layer is constructed on the negative electrode of the battery, so that the electrochemical performance and the cycle stability can be remarkably improved.

Inventors

Pu Hushan
XIAO FENG
HU DALIN
LIAO XINGQUN

Assignees

深圳市豪鹏科技股份有限公司

Dates

Publication Date: 20260508
Application Date: 20251231

Claims (14)

1. A negative electrode sheet comprising A negative electrode current collector; The active material layer is arranged on the surface of the negative electrode current collector, the active material layer comprises a negative electrode active material, a conductive agent, a binder and a conductive polymer layer, the negative electrode active material comprises a silicon-containing material, the negative electrode active material and the conductive agent are mutually mixed and mutually bonded through the binder, the conductive polymer layer is formed on the surfaces of the adjacent negative electrode active material and the conductive agent and forms a continuous surface, polymerization monomers of the conductive polymer layer comprise 3, 4-ethylenedioxythiophene and sodium polystyrene sulfonate, and the conductive polymer layer is polymerized by a constant current method.
2. The negative electrode sheet according to claim 1, wherein the thickness of the conductive polymer layer is 0.5 to 2 μm.
3. The negative electrode sheet according to claim 1, wherein the molar ratio of the 3, 4-ethylenedioxythiophene to the sodium polystyrene sulfonate is (1-5): 1-5.
4. The negative electrode sheet according to claim 1, wherein the negative electrode active material is 90.5 to 93.5% by mass, the binder is 6 to 9% by mass, and the conductive agent is 0.3 to 0.5% by mass, based on 100% by mass of the total of the negative electrode active material, the binder, and the conductive agent.
5. The negative electrode tab of claim 1, wherein the silicon-containing material comprises one or more of silicon particles, silicon oxide, and silicon carbon material.
6. The negative electrode sheet according to claim 5, wherein the silicon-containing material is selected from silicon-carbon materials, and the mass content of silicon in the silicon-carbon materials is 40% -60%.
7. The method for producing a negative electrode sheet according to any one of claims 1 to 6, comprising the steps of: mixing a negative electrode active material, a conductive agent and a binder to form slurry, and coating the slurry on the surface of the negative electrode current collector; And depositing a polyelectrolyte on the surfaces of the adjacent anode active material and the conductive agent by a constant current method to form a conductive polymer layer, wherein the polyelectrolyte comprises 3, 4-ethylenedioxythiophene and sodium polystyrene sulfonate.
8. The method for producing a negative electrode sheet according to claim 7, wherein the concentration of the 3, 4-ethylenedioxythiophene in the polyelectrolyte is 0.01 to 0.1Mol/L; And/or, in the polyelectrolyte solution, the concentration of the sodium polystyrene sulfonate is 0.01-0.1Mol/L.
9. The method for producing a negative electrode sheet according to claim 7, wherein the polymer electrolyte further comprises lithium perchlorate, and the concentration of the lithium perchlorate in the polymer electrolyte is 0.05 to 0.5Mol/L.
10. The method for producing a negative electrode sheet according to claim 7, wherein the polyelectrolyte solution further comprises a pH adjuster including one or more of hydrochloric acid, perchloric acid, sulfuric acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid.
11. The method for producing a negative electrode sheet according to claim 7, wherein the pH of the polyelectrolyte is 0.1 to 2.
12. The method according to claim 7, wherein an Ag/AgCl electrode is used as a reference electrode in the constant current process, and/or a Pt electrode is used as a counter electrode in the constant current process.
13. The method according to claim 7, wherein the constant current method is performed with a current of 0.2-10mA/cm 2 and/or a deposition time of 10-600s.
14. A battery, comprising a positive plate, a negative plate and a diaphragm, wherein the negative plate is the negative plate according to any one of claims 1 to 6 or the negative plate prepared by the preparation method of the negative plate according to any one of claims 7 to 13.

Description

Negative plate, preparation method and battery Technical Field The invention relates to the technical field of batteries, in particular to a negative plate, a preparation method and a battery. Background In the field of lithium ion batteries, especially in applications facing high energy density requirements (e.g. electric vehicles, consumer electronics), silicon-containing materials are considered as important candidates for next generation negative electrodes due to their high theoretical specific capacities (e.g. pure silicon up to about 4200 mAh/g). However, silicon-containing materials have severe volume expansion (up to 300% or more) during charge and discharge, resulting in pulverization of particles, collapse of electrode structures, repeated rupture and regeneration of Solid Electrolyte Interface (SEI) films, thereby causing rapid capacity decay and shortened cycle life. In order to alleviate the above problems, the prior art generally adopts a silicon-carbon composite material as a negative electrode active material, and a conductive additive (such as carbon black, conductive graphite, carbon nanotube CNT or graphene) is directly mixed into the slurry to improve the overall conductivity of the electrode. The typical process flow comprises mixing silicon-containing material, conductive agent and binder proportionally, pulping, coating on copper foil current collector, drying, and rolling to obtain the negative plate. However, the conventional scheme has the remarkable disadvantages that the conductive agent is unevenly dispersed to form a local dead zone, the conductive agent (particularly nano-scale materials such as CNTs) is extremely easy to agglomerate, uniform dispersion is difficult to realize in the slurry, partial active particles are not effectively connected, an electron transmission dead zone is formed, and the material utilization rate is reduced. Even if the conductive agent is distributed perfectly, the conductive agent and the active particles are still mainly in point-to-point contact, the contact area is small, the interface resistance is high, and the contact failure is easy to occur under the condition of high current or long circulation, so that how to overcome the technical problems and defects is the important problem to be solved. Disclosure of Invention Aiming at the problem that negative electrode active particles in the existing silicon negative electrode plate are not effectively connected, the invention provides a negative electrode plate, a preparation method and a battery. The technical scheme adopted by the invention for solving the technical problems is as follows: the first aspect of the present invention provides a negative electrode sheet comprising A negative electrode current collector; the negative electrode active material comprises a silicon-containing material, the negative electrode active material and the conductive agent are mutually mixed and mutually adhered through the adhesive, the conductive polymer layer is formed on the surfaces of the adjacent negative electrode active material and the conductive agent and forms a continuous surface, and polymerization monomers of the conductive polymer layer comprise 3, 4-ethylenedioxythiophene and sodium polystyrene sulfonate. Optionally, the conductive polymer layer is polymerized by a constant current method. Optionally, the thickness of the conductive polymer layer is 0.5-2 μm. Optionally, the molar ratio of the 3, 4-ethylenedioxythiophene to the sodium polystyrene sulfonate is (1-5): 1-5. Optionally, the total mass of the anode active material, the binder and the conductive agent is 100%, the mass percentage of the anode active material is 90.5% -93.5%, the mass percentage of the binder is 6% -9%, and the mass percentage of the conductive agent is 0.3% -0.5%. Optionally, the silicon-containing material includes one or more of silicon particles, silicon oxide, and silicon carbon material. Optionally, the silicon-containing particles are selected from silicon-carbon materials, and the mass content of silicon in the silicon-carbon materials is 40% -60%. The second aspect of the invention provides a preparation method of a negative plate, comprising the following steps: mixing a negative electrode active material, a conductive agent and a binder to form slurry, and coating the slurry on the surface of the negative electrode current collector; And depositing a polyelectrolyte on the surfaces of the adjacent anode active material and the conductive agent by a constant current method to form a conductive polymer layer, wherein the polyelectrolyte comprises 3, 4-ethylenedioxythiophene and sodium polystyrene sulfonate. Optionally, in the polyelectrolyte, the concentration of the 3, 4-ethylenedioxythiophene is 0.01-0.1Mol/L; And/or, in the polyelectrolyte solution, the concentration of the sodium polystyrene sulfonate is 0.01-0.1Mol/L. Optionally, the polyelectrolyte solution further comprises lithium perchlorate, and