Studies on Formation and Decomposition of the Layered Cobaltite LixNayCoO2

Abstract

Lithium-sodium cobaltite LixNayCoO2 (x≈y≈0.5) with ordered layered structure is promising thermoelectric material. Here we report the peculiarities of this phase formation and decomposition processes studied by TG/DTA, XRD, SEM, and TEM methods. Significant weight loss resulting from oxygen liberation and endothermic effect at T≈1000°C are the main features of the LixNayCoO2 formation. Decomposition of the ordered phase is accompanied by exothermic effect at ≈940°C and the weight increase. Electron microscopic study shows that the lithium-sodium cobaltite decomposes into LiCoO2 and γ-Na0.7CoO2. Lattices of the initial phase and formed ones demonstrate mutual orientation.