Lithium insertion in two tetragonal tungsten bronze type phases, M8W9O47 (M=Nb and Ta)

Abstract

A study of lithium insertion in two tetragonal tungsten bronze (TTB) type phases of general formula M ₈ W ₉ O ₄₇ (M=Nb and Ta), is presented. The electrochemical insertion of up to 20 lithium atoms per formula unit in Nb ₈ W ₉ O ₄₇ (Li/ΣM=1.2) proceeds through a reversible reaction with several single phase and one two-phase domains, while in Ta8W9O47 the reversibility of lithium insertion is limited to 15 atoms (Li/Sigma;M=0.9). Structural changes on Nb ₈ W ₉ O ₄₇ as a function of the number of lithium atoms inserted have been studied by X-ray powder diffraction.