Quantitative structural analysis of the transition from LT-LixCoO2 to HT-LixCoO2 using the rietveld method: correlation between structure and electrochemical performance

A quantitative phase analysis was made of LixCoO2 powders obtained by two distinct chemical methodologies at different temperatures (from 400 to 700 °C). A phase analysis was made using Rietveld refinements based on X-ray diffraction data, considering the LixCoO2 powders as a multiphase system that simultaneously contained two main phases with distinct, layered and spinel-type structures. The results showed the coexistence of both structures in LixCoO2 obtained at low temperature (400 and 500 °C), although only the layered structure was detected at higher temperatures (600 and 700 °C), regardless of the chemical powder process employed. The electrochemical performance, evaluated mainly by the cycling reversibility of LixCoO2 in the form of cathode insertion electrodes, revealed that there is a close correlation between structural features and the electrochemical response, with one of the redox processes (3.3 v/3.9 v) associated only with the presence of the spinel-type structure.