Application of precursor with ultra-small particle size and uniform particle distribution for ultra-high nickel single-crystal cathode materials by coprecipitation method

Ultra-high nickel single-crystal cathode materials have become the most promising for lithium-ion batteries. However, the preparation of ultra-high nickel single-crystal precursors by a continuous coprecipitation method has the disadvantages of large particle size, wide distribution, poor morphology. The extent of the inhomogeneous reactions can be more severe in single-crystal cathodes with larger particle size. Herein, the coprecipitation method with a solid concentrator was adopted, and citrate sodium was used as a complexing agent to improve the physical properties of precursors and electrochemical performance of single-crystal cathode materials. By analyzing the morphology and agglomeration mechanism of the precursor nucleuses under different pH values, it was found that hexagonal nanosheets grew along the 101 direction, and the primary particles showed thicker at pH of 11.4. The hexagonal nanosheets grew along the 001 direction, and the primary particles showed finer at pH of 12.2. The morphology and particle size uniformity of the secondary particles formed by agglomeration at these two pH values showed poor. However, hexagonal nanosheets grew synergistically along the 001 and 101 directions at pH of 11.8, so the primary particles with uniform particle size gradually agglomerated, and then the secondary particles with ultra-small particle size and uniform distribution obtained. Compared to materials prepared by the traditional continuous coprecipitation method, the precursor displays a smaller particle size(D