Composite anode material for lithium battery, and preparation method of composite anode material

Abstract

The invention discloses a composite anode material for a lithium battery, which is characterized in that the surface of a lithium cobalt oxide material substrate is coated with a magnesium-doped aluminum phosphate layer. A preparation method of the composite anode material comprises the following steps: dissolving a soluble aluminum salt and a soluble magnesium salt in a solvent to obtain a solution A; dissolving a soluble phosphate in the solvent to obtain a solution B; injecting the solution B into the solution A under stirring conditions, controlling the pH value in a system during reactionto range from 4 to 6, and carrying out filtering, washing and drying on an obtained product to obtain amorphous magnesium-doped aluminum phosphate particles; and uniformly mixing the amorphous magnesium-doped aluminum phosphate particles with a lithium cobalt oxide material, and carrying out sintering to obtain the composite anode material. The composite anode material and the preparation methodof the composite anode material have the advantages that the lithium cobalt oxide material substrate is coated with the magnesium-doped aluminum phosphate layer for modification, so that the crystallinity of the coating layer can be improved through doping of the magnesium element, higher electrolyte erosion resistance of the composite anode material can be achieved, an electrolyte can be isolatedfrom active substances for a longer time, and the cycling performance and the safety performance of the lithium battery can be further improved.

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...

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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

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