Thermal behavior of Li_1-yNiO₂ and the decomposition mechanism

We report the thermal behavior of Li_1-yNiO₂ up to 300°C which we investigated using thermogravimetry (TG) and differential scanning calorimetry (DSC). The decomposition mechanism was studied using the X-ray diffraction data obtained for the thermally decomposed products. At about 200°C Li_1-yNiO₂ turned into Li(_1-y)/(_2-y)Ni1/(_2-y)O which has a rock-salt structure. This was accompanied by oxygen evolution. A significant exothermic process was observed for compounds with y ≥ 0.7 and this resulted in products with disordered rock-salt structures. Using these results, we propose a mechanism in which the exothermic behavior is caused by random cation mixing.