A kind of lithium-ion battery composite cathode material and preparation method thereof

Abstract

The invention discloses a lithium ion battery composite positive electrode material, in which a magnesium-doped aluminum phosphate layer is coated on the surface of a lithium cobalt oxide material matrix. The preparation method of the present invention: dissolve easily soluble aluminum salt and easily soluble magnesium salt in the solvent to obtain solution A; dissolve easily soluble phosphate in the solvent to obtain solution B; under stirring condition, inject solution B into the solution In A, the pH value of the system during the reaction is controlled to be 4-6, and the resulting product is filtered, washed, and dried to obtain amorphous magnesium-doped aluminum phosphate particles; the amorphous magnesium-doped aluminum phosphate particles are mixed with lithium cobaltate materials homogeneous and sintered to obtain a composite positive electrode material. In the present invention, the lithium cobaltate material matrix is ​​coated with a magnesium-doped aluminum phosphate layer, and the incorporation of magnesium improves the crystallinity of the coating layer, improves the electrolyte erosion resistance of the composite positive electrode material, and can be used for a longer period of time. Keeping the isolation of the electrolyte and the active material improves the cycle performance and safety performance of the lithium-ion battery.

Description

technical field [0001] The invention belongs to the field of positive electrode materials for batteries, and in particular relates to a composite positive electrode material for a lithium ion battery and a preparation method thereof. Background technique [0002] Among lithium-ion cathode materials, lithium cobalt oxide cathode materials are widely used due to their advantages such as high working voltage, energy density, fast charge and discharge, and easy synthesis. However, after the lithium cobalt oxide cathode material is deeply charged, high-valent cobalt ions are likely to react with the electrolyte, resulting in deterioration of cycle performance and poor safety performance. [0003] In order to solve the above problems, the main method adopted at present is to dope and surface coat the substrate. By adjusting the doping stable structure of inactive elements, a layer of material is coated on the surface of the lithium cobaltate cathode material to prevent the direct...

AI Technical Summary

Problems solved by technology

But, above-mentioned first method because aluminum phosphate is insoluble in water or organic solvent, can form agglomeration when dispersing in solvent, aluminum phosphate can not be evenly distributed on the positive electrode material surface; Second method, the homogeneity of aluminum phosphate, aluminum phosphate and The tightness of the surface contact of the positive active material is improved, but the hydrolysis of the soluble aluminum salt is acidic, which causes the surface of the matrix material to be eroded by the acidic solution during the preparation of the composite material, and the surface is destroyed, resulting in the first specific capacity of the final composite. Big loss

Images