Spinel versus layered structures for lithium cobalt oxide synthesised at 400°C

Rietveld refinements of X-ray data of LiCoO2 prepared at 400°C and a chemically-delithiated product Li0.5CoO2 using space group symmetries R3̄m and Fd3m are reported. Refinements in both R3̄m (layered-type structure) and Fd3m (spinel-type structure) give comparable fits to the data. This structural anomaly is discussed in terms of the refinements and electrochemical data obtained when lithium is extracted from LiCoO2 in non-aqueous cells at room temperature. A spinel-related model for LixCoO2 (0.5⩽x⩽1) is preferred.