Micro-structure tuning and evolution of hydroxide precursor with radially oriented grains during industrial-scale continuous precipitation process

Abstract

Constructing hydroxide precursors with radially oriented primary grains is the key factor for fabricating Ni-rich cathodes with sufficient cycle life. Herein, hydroxide precursors with composition of Ni0.92Co0.04Mn0.04(OH)2 were synthesized to study the effects of pH and ammonia concentration on the phase, morphology, and orientation of grains, as well as the evolution of primary grains and secondary particles during industrial-scale continuous precipitation process. Results show that the preferential growth of primary grains varies significantly with change of pH, ammonia concentration and the growth of secondary particles. Meanwhile, the variation of grain size along direction parallel to [001] is more obvious than that perpendicular to [001] after decreasing pH or increasing ammonia concentration. Moreover, the size distribution of secondary particle varies with the increase of feeding time or the change of reaction condition in a regular manner. Although a steady state could be reached for continuous precipitation, the different residence times endow the size of secondary particles with normal distribution. The results disclosed in this work may provide a guiding significance for designing precipitation procedure for hydroxide precursor of high-end Ni-rich cathodes.