Precursor with hydroxide coated on outer layer of single crystal and preparation method of precursor

Abstract

The preparation method comprises the following steps: carrying out acid treatment on a selected single-crystal positive electrode material to form an uneven surface, so that primary particles of the hydroxide generated in a subsequent co-precipitation reaction can be better attached to the surface of the single-crystal positive electrode material, and the surface of the single-crystal positive electrode material is more uniform; precursor particles with a core-shell structure are prepared, each particle is composed of an inner core and an outer shell layer, the inner core is a single-crystal positive electrode material, the outer shell layer of each particle is formed by aggregating nickel-containing composite hydroxide primary particles, and the structure can further improve the cycle performance, the overall packing density and the specific capacity of the material; meanwhile, according to different application fields, the primary particles of the shell layers of the particles are in a sheet shape, a block shape, a spindle shape or a needle shape, so that the tap density of the material is further improved, and meanwhile, the rate capability, the cycle performance and other electrochemical performance of the lithium ion battery are improved.

Description

technical field [0001] The invention belongs to the technical field of precursors of positive electrode materials of lithium ion batteries, in particular to a precursor of a single crystal outer layer coated with hydroxide and a preparation method thereof. Background technique [0002] At present, ternary materials are mostly synthesized by co-precipitation method, and the characteristic of co-precipitation is to rely on the aggregation of nano-scale primary particles to grow into secondary particles. During the co-precipitation process, vigorous stirring leads to the agglomeration of primary particles with disordered distribution, so there are different degrees of stress and distortion in the secondary particles. [0003] In particular, the stress accumulation of ternary materials during the cycle is the main reason for the cycle decay of ternary materials. The connection structure between the primary particles of the material during the cycle will cause the local current d...

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Problems solved by technology

On the one hand, these cracks will lead to short circuit of electrons. On the other hand, with the generation of cracks, the electrolyte will invade the inside of the NCM particles, and the fresh surface of the cracks will have more negative reactions with the electrolyte, affecting the cycle of the entire battery. performance and security issues

[0004] The stress and uneven distribution of Li inside the particles are mainly caused by the morphology of the secondary particles, so some materials with porous structure and open structure show better cycle performance, which can effectively absorb the volume change. , reduce the stress and uneven distribution of Li during the charging process, so as to achieve the effect of improving cycle performance, but this structure will cause the overall packing density to decrease, resulting in a decrease in the overall specific capacity

[0005] Doping technology is an important method to solve the poor structural stability of ternary materials. For example, Al element doping can significantly improve the structural stability of ternary materials, but Al element has no electrochemical activity. However, excessive Al element doping will cause Reversible capacity reduction in ternary materials

[0006] An effective solution to the stress accumulation problem of ternary materials during cycling has not been found in the prior art

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