Improving electrochemical properties of LiCoO 2 by enhancing thermal decomposition of Cobalt and Lithium carbonates to synthesize ultrafine powders

Ultrafine LiCoO2 powders were directly synthesized by enhancing thermal decomposition of Cobalt and Lithium carbonates through a mechanochemical activation treatment to intensify the solid state diffusion reaction. Effects of activation treatment time on particle size and structure of the LiCoO2 compound were investigated. In the present study, the optimum mechano-chemical activation time was found to be 10 h. In this study, the ultrafine LiCoO2 powders (particle size in the range from 200 nm to 400 nm) show good structural stability and higher structural integrity. X-ray photoelectron spectroscopy (XPS) results indicate that most of Co cations exist as Co3+, which contributes to the improvement of the electrochemical performance. Cyclic voltammetry (CV) curves of different cycles display almost a complete overlap, which can be regarded as another evidence of the excellent cycle performance. The LiCoO2 powders exhibit a high initial discharge specific capacity of 175.2 mAh/g at 0.1 C (274 mA/g at 1 C) and a remarkable cycle stability from 167.5 mAh/g to 146.2 mAh/g at 0.5 C and from 147.5 mAh/g to 115.2 mAh/g at 3 C after 100 cycles in the range of 3.3–4.3 V. The apparent activation energy and the frequency factor of the decomposition of CoCO3 are 69.83 kJ/mol and 1.369×106, respectively, indicating that the ultrafine in-process product of Co3O4 can be quickly prepared at a low temperature.