Synthetic optimization of spherical LiCoO2 and precursor via uniform-phase precipitation

LiCoO₂ had been successfully prepared from spherical basic cobalt carbonate via a simple uniform-phase precipitation method at normal pressure, using cobalt sulfate and urea as the reactants. The preparation of spherical basic cobalt carbonate was significantly dependant on synthetic condition, such as the reactant concentration, reaction temperature and impeller speed, etc. The optimized condition resulted in spherical basic cobalt carbonate with uniform particle size distribution, as observed by scanning electron microscopy. Calcination of the uniform basic cobalt carbonate with lithium carbonate at high temperature led to a well-ordered layer-structured LiCoO₂ without shape change, as confirmed by X-ray diffraction. Due to the homogeneity of the basic cobalt carbonate, the final product, LiCoO₂, was also significantly uniform, i.e., the average particle size was of about 10 μm in diameter and the distribution was relatively narrow. As a result, the corresponding tap-density was also high approximately 2.60 g cm⁻³, of which the value is higher than that of commercialized LiCoO₂ of Hunan Ruixing, co. In the voltage range 2.8–4.2, 2.8–4.3, and 2.8–4.4 V, the discharge capacities of LiCoO₂ electrode were 153, 159, and 168 mAh g⁻¹, respectively, with better cyclability.