抄録
Thermal behavior and symmetry change were clarified for delithiated LiNiO2 with different sample compositions which were characterized by X-ray diffraction measurement. On heat treatment, the DTA exothermic peak was observed at 200°C which corresponds to the phase transition temperature of non-stoichiometric Li1-x-yNi1+xO2 (0.07<x) from hexagonal to cubic phase. In contrast, exothermic and endothermic process was observed at 200°C of nearly stoichiometric Li1-x-yNi1+xO2 (x=0.01). For both samples, weight loss was observed near 200°C on the TG curves. The weight loss is explained as oxygen release from LiNiO2. The amount of released oxygen is higher in nearly stoichiometric samples, for the endothermic peak is caused by decomposition which contributes more to oxygen loss. Symmetry change was examined with different sample compositions in high pressure oxygen. Symmetry change from hexagonal at 200°C was not observed for non-stoichiometry sample.
