Studies on Formation and Decomposition of the Layered Cobaltite LixNayCoO2

Abstract

Lithium-sodium cobaltite Li x Na y CoO 2 (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 Li x Na y CoO 2 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 LiCoO 2 and γ-Na 0.7 CoO 2 . Lattices of the initial phase and formed ones demonstrate mutual orientation.