Analysis of the Growth Mechanism of Coprecipitated Spherical and Dense Nickel, Manganese, and Cobalt-Containing Hydroxides in the Presence of Aqueous Ammonia

Spherical and dense metal hydroxides were synthesized with a coprecipitation reaction in the presence of aqueous ammonia. The growth of the particles was studied by tracking the tap density and morphology with reaction time. The dependence of pH on the tap density and morphology of the particles synthesized in the coprecipitation reaction was determined for Ni(OH)2, Ni1/2Mn1/2(OH)2, and Ni1/3Mn1/3Co1/3(OH)2 The pH range at which particle growth occurred varied for the different metal hydroxides. Solving the chemical equilibria present in the coprecipitation reaction revealed that the pH range at which spherical particle growth occurred was due to the presence of metal coordinated with ammonia. On the basis of the experiments and analysis presented here, the metal hydroxide particle growth occurs by a dissolution−recrystallization type mechanism during synthesis.