Phase transformation of LiNi0.75Co0.25O2

In this article, the phase transformation of cathode material, LiNi0.75Co0.25O2, prepared by sol–gel pretreatment and solid-phase formation, was studied in detail. The characteristic temperatures associated with the phase transformation of LiNi0.75Co0.25O2 were selected. Accordingly, two series of experiments at different temperatures were performed in situ and ex situ by XRD and SEM to examine the structure and morphology of the material during the phase transformation. It was found that at the temperature below 600 °C a cubic structure was formed and the nickel metal in the material was presented as Ni2+. A hexangular layer structure started to form when the temperature reached or became higher than 600 °C. The structure became better defined with the increase of temperature. The material was characteristic of R-3 m spatial structure at 725 °C.