Synthesis of Core–Shell Particles of Nickel–Manganese–Cobalt Hydroxides in a Continuous Couette-Taylor Crystallizer

A Taylor vortex flow was used as an effective continuous process for synthesizing uniform and spherical core–shell particles of nickel–manganese-cobalt hydroxides, consisting of a (Ni0.90Mn0.05Co0.05)(OH)2 (Ni-rich hydroxide) core and (Ni0.475Co0.05Mn0.475)(OH)2 (half–half hydroxide) shell. Tiny half–half hydroxide particles (primary particles) were initially precipitated and then adhered to core particles of the Ni-rich hydroxide to form core–shell particles via collision and agglomeration between the primary particles and the core particles. pH 10 was determined as the optimum condition for maximizing the interaction between the primary particles and the core particles. The shell-layer formation depended strongly on the operating parameters of the Couette-Taylor (CT) crystallizer, including the inner cylinder rotation speed, reactant concentration, and mean residence time. Using those parameters, the shell-layer thickness was controlled from 0.4 mm to 2.0 mm. Plus, a narrow size distribution (coefficient of variation) of 0.16 and high tap density of core–shell particles of 2.06 g/cm3 were obtained. When compared with a continuous mix suspension mixed product removal (MSMPR) crystallizer, the toroidal Taylor vortex flow in the CT crystallizer was over 10 times more effective for the core–shell particle synthesis than the random turbulent eddy flow in the MSMPR crystallizer.