Urea Homogeneous Precipitation Of Monodispersed Cobalt Oxide Powder

With the development of lithium-ion batteries, the demand of Co₃O₄, which is the key materials for positive electrode material of LiCoO₂, has increased greatly in recent years. Since the Co₃O₄ prepared by conventional methods can hardly meet the requirement of the electronic grade Co₃O₄, the present work utilized homogenous precipitation to prepare the precursor powders of Co₃O₄ in the solution with high concentration of Co²⁺, and the products of Co₃O₄ was produced by the thermal decomposition of the precursor, aiming to prepare Co₃O₄ powders of good quality simply and apply the technique for the industry practice.In this work the precursor powders of Co₃O₄ were prepared byhomogenous precipitation in open and close containers respectively, and the effects of the factors such as concentration of Co²⁺, molar ratio of urea and Co²⁺, pH value of the initial solution, reactive time and temperature on the rate of cobalt precipitation, particle size and morphology were investigated, according to which the optimum technical conditions for the combined precipitation were determined. The analyses and detection indicated that the chemical composition of the precipitates produced in open container was well-crystallized Co_x(OH)_yCl_z, which showed the morphology as stacked chip with excellent Crystallization, uniform size distribution between 1～2μm and no agglomerates. The chemical composition of the precipitates produced in close container was amorphous Co_x(OH)_y(CO₃)_z, which showed various morphology(such as acicular, polyhedron and aggregate spheroids) with various conditions, and the uniform size distribution.With the reference of the differential thermal analyses data in the thermal decomposition, the precursor powders produced in open and close containers respectively, were treated in tubular furnace and thermal insulated for 3～5h at 300℃and 900℃. The result showed that after the thermal insulation for 3h at 450℃, the content of cobalt in the precursor produced in open containers, is similar to the theoretical content of cobalt in Co₃O₄ (73.43%), and the particle size ranges between 3μm and 4μm. The morphology of the particle was polyhedron or spheroid.The present work was carried out in the solution with high concentration of Co²⁺, aiming to the industry practice. The study indicated that Co₃O₄ powders, of which the particle size and morphology accord with the requirement, can be prepared by homogenous precipitation with urea as precipitant.