Process for coating lithium ion battery with slurry

Abstract

A process for coating a lithium ion battery with slurry includes preparation of aqueous slurry, in which pure water is used as a solvent of the aqueous slurry. During the preparation of aqueous slurry, addition of a binder is later than addition of a thickening agent. The process includes the steps of: (A) before addition of the thickening agent, adding polyether modified silicon oil, which accounts for 0.01-3% of total mass of the pure water; (B) after the addition of the binder, adding polyether trisiloxane, which accounts for 0.01-3% of total mass of the pure water; (C) stirring the aqueous slurry prepared in the steps (A) and (B) for 20-30 min, or stirring the slurry at the same time of doing the steps (A) and (B) respectively for 20-30 min; (D) regulating viscosity of the slurry to 2500-4000 mPa*s; and (E) filtering the slurry and coating a lithium ion battery with the slurry. In the method, surface tension of the aqueous slurry is controlled so as to reduce phenomena of pore and edge shrinkage, thus improving quality and performance of the battery and improving appearance of same.

Description

technical field [0001] The invention belongs to the field of manufacturing technology of lithium ion batteries, and in particular relates to a coating technology of aqueous slurry for lithium ion batteries. Background technique [0002] Lithium-ion battery slurry is a necessary substance for the manufacture of lithium-ion batteries. The existing lithium-ion battery slurry is divided into four major categories of main components, including: active materials, conductive agents, binders, solvents, and sometimes need to add thickeners According to different solvents, it can be divided into water-based slurry and oil-based slurry, wherein the solvent of water-based slurry is pure water, and the solvent of oil-based slurry is NMP (N-methylpyrrolidone). After the above ingredients are stirred, the slurry is finally in a liquid state with certain fluidity and cohesiveness, which can be coated on the current collector; but for the water-based slurry, due to the high surface tension o...

AI Technical Summary

Problems solved by technology

After the above ingredients are stirred, the slurry is finally in a liquid state with certain fluidity and cohesiveness, which can be coated on the current collector; but for the water-based slurry, due to the high surface tension of the water-based slurry, it is difficult to apply it to the current collector. If there is dust or foreign matter in contact with the slurry when the surface is not dry, it will cause shrinkage (depression at the position of the foreign matter) due to the difference in surface tension. figure 1 and attached figure 2 , because the coating amount at the center of the shrinkage cavity is significantly small, the current collector is easily exposed, which will affect the quality of the electrode. Some larger shrinkage cavities may cause scrapping, affect the pass rate of the product, increase the manufacturing cost, and affect the quality of the electrode. The appearance and electrical performance of the electrode may cause safety problems due to insufficient local coating at the shrinkage cavity in serious cases; at the same time, due to changes in the surface tension of the slurry during the drying process, it will cause edge shrinkage (high thickness at the edge position may cause Excessive compression during post-process rolling) see the attached figure 2

[0003] Chinese patent CN 102130338 A discloses a lithium-ion battery water-based positive electrode slurry and its preparation method, which specifically discloses adding an anionic defoamer-polysiloxane before adding a thickener in the water-based slurry preparation process. Technical solution, the technical problem to be solved by this technical solution lies in the bubble phenomenon that occurs during the stirring process, but due to the limitation of the timing of addition, the surface tension of pure water after thickening cannot be effectively reduced

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