Nickel cobalt lithium manganate positive electrode material with surface micro-gradient structure and preparation method thereof

Abstract

The invention discloses a nickel cobalt lithium manganate positive electrode material with a surface micro-gradient structure. The molecular formula is LiaNixCoyMnzRbO2, 1< / =a< / =1.2, 0.3< / =x< / =0.98, 0.01< / =y< / =0.6, 0.001< / =z< / =0.2, b is 4 / 3-a / 3-x-y-z, 0.00001< / =b< / =0.1, R is a doping element, and the doping element is one or a combination of more than one selected from metal elements other than Ni, Zn and Cu in an element periodic table. The invention also discloses a preparation method for the nickel cobalt lithium manganate positive electrode material with the surface micro-gradient structure. Through preparing the nickel cobalt lithium manganate positive electrode material with the surface micro-gradient structure, a thin covering layer with multiple doping elements, a stable structureand a gradient structure can be formed only on the outer surface of the material, the main body of the material is basically unchanged, a stable and uniform protective layer with electrochemical activity and high electrical conductivity can also be formed on the surface layer, and while the electrochemical capacity of the material is ensured to the maximum degree, the safety and the stability canalso be improved.

Description

technical field [0001] The invention belongs to the technical field of preparation methods of battery positive electrode materials, and in particular relates to a nickel-cobalt lithium manganese oxide positive electrode material with a surface micro-gradient structure and a preparation method thereof. Background technique [0002] Nickel cobalt manganese oxide lithium ion battery cathode material is widely used in IT products and new energy vehicles due to its high energy density and relatively simple preparation process. However, due to the poor structural stability of the nickel-cobalt-manganese acid cathode material, high-priced nickel is easy to react with the electrolyte, causing the electrolyte to decompose and release gas, which will cause great harm to the cycle life and safety of the material. It is generally used to replace nickel doped with cobalt, manganese, aluminum and other doped metal parts to improve its stability. However, due to the low cobalt reserves, w...

AI Technical Summary

Problems solved by technology

Gradient nickel cobalt manganese acid positive electrode material is a continuous change in chemical composition from the core to the surface of spherical material particles, with high content in the core, high electrochemical capacity, high content of doping elements in the surface layer, and good chemical stability, so it can be used to a certain extent While ensuring the electrochemical capacity of the material, the stability is improved. However, traditional gradient materials are generally achieved by controlling the continuous change of the metal ion content when preparing the precursor. Not only is the preparation of the precursor difficult, but also a large number of ants will be formed in the material particles after sintering. Cave-shaped micro-channels, the electrolyte can still penetrate into the nickel-rich part inside the particles through these micro-channels, affecting the stability and safety of the material

Surface coating can cover a layer of material with good stability on the surface of the material, but it is difficult to achieve uniform coating at the atomic level, and there are obvious problems of local exposure and local coating layer being too thick. The coated compounds are generally electrochemically inert, and the ionic conductivity and electronic conductivity are generally very low, which will seriously affect the rate performance and capacity of the material