Surface-modified lithium cobaltate material and preparation method thereof

Abstract

The invention discloses a surface-modified lithium cobaltate material and a preparation method thereof. The lithium cobaltate material comprises a core particle and a surface-modified layer coating the core particle, wherein the core particle is a lithium cobaltate-based positive material with a structural formula as follows: LixCo(1-y)MyO2, wherein x is greater than 1 and not greater than 1.2, y is not less than 0 and not greater than 0.1, M is a doping element; the surface-modified layer comprises a Li<+1> conducting layer and an electrolyte isolating layer; the core particle is coated by the Li<+1> conducting layer and the electrolyte isolating layer in sequence. According to the invention, by sufficiently utilizing dynamic characteristic that different substances react with residual Li salt on the surface of the lithium cobaltate, and characteristic of final reaction product performance, the lithium cobaltate material with double coating layers is prepared. The material is high in comprehensive performances, has high discharge capacity, high cycling stability and the like. The preparation method disclosed by the invention is simple in process and easily realizes industrial production.

Description

technical field [0001] The invention belongs to the field of lithium-ion battery electrode materials, and in particular relates to a surface-modified lithium cobalt oxide material and a preparation method thereof. Background technique [0002] The production process of lithium cobaltate material is simple, and it has the advantages of high voltage platform, suitable for high current charge and discharge, and high specific energy. Lithium oxide is currently the most important commercial lithium-ion battery cathode material. Although it has many advantages as a positive electrode material, the anti-overcharge ability of this material is poor. When the charge cut-off voltage is greater than 4.2V, Li + A large number of deintercalation will occur, resulting in the formation of oxygen vacancies on the surface of lithium cobalt oxide, which will eventually lead to an unstable surface structure, and the discharge specific capacity of the material will rapidly decay. [0003] In o...

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Problems solved by technology

The research results reported above show that the doping and coating modification of lithium cobaltate can stabilize the structure of lithium cobaltate materials and inhibit the side reactions between lithium cobaltate and electrolyte. Based on the above As a result of the research, battery manufacturers have developed 4.3V or even 4.35V lithium-ion batteries, but they still cannot meet the requirements of sample performance, especially cycle performance, under higher voltage (≥4.4V) conditions, because the above-mentioned doping, including The coating technology does not have a fundamental impact on the structural stability of the material, and the specific discharge capacity of the material will rapidly decay at a voltage of 4.4V or higher. At the same time, the above doping and coating technologies will not improve The discharge specific capacity and first-time efficiency of the material, etc., therefore, there are still large defects in its electrical performance, which also greatly reduces the energy density of lithium-ion batteries.

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