In Situ Monitoring of the Growth of Nickel, Manganese, and Cobalt Hydroxide Precursors during Co-Precipitation Synthesis of Li-Ion Cathode Materials

The electrochemical performance of cathode materials for Li-ion batteries depends on the morphology of the material, which, in turn, depends on the synthesis conditions. Very few studies have focused on the impact of process conditions on the final morphology of the cathode particles and analyzed the growth during synthesis. In this paper, the evolution of nickel, manganese, and cobalt hydroxide precursor, Ni1/3Mn1/3Co1/3(OH)2, is investigated using a combination of in situ and ex situ techniques during the commonly-used coprecipitation process. These include in situ wide angle X-ray scattering, in-situ ultra-small angle X-ray scattering and ex situ particle size analysis. The growth rate of crystalline Ni1/3Mn1/3Co1/3(OH)2 primary particle is found to be almost constant, consistent with a mathematical analysis of process. The growth of the Ni1/3Mn1/3Co1/3(OH)2 secondary particle and its particle size distribution revealed different growth stages for samples prepared at different pH. These techniques are complimented with scanning electron microscopy and electrochemical testing to track the morphology and performance of the hydroxide particle and the subsequent calcined LiNi1/3Mn1/3Co1/3O2 cathode active material. This study presents insights into the synthesis process and provides a deeper understanding to aid in process optimization.