Lithium insertion into pyrochlore WO 3

Abstract

The chemical and electrochemical insertion of lithium into pyrochlore WO 3 at room temperature was studied. Li x WO 3 bronzes were found to maintain their structure upon lithium insertion, lithium occupying the 8b positions of the space group Fd3m that define the centres of the tunnels. Lithium insertion into crystalline phase is a reversible process that results in an increased deterioration to the crystallinity of the phase with increasing lithium content. Values of x close to unity resulted in complete amorphization. Additional information on the thermal behaviour of hydrated pyrochlore WO 3 is also reported. IR data recorded under vacuum showed the presence of molecular water in the channels at temperatures above 300°C. Under these conditions, pyrochlore polymorph is transformed into the orthorhombic phase probably as a consequence of a reduction process undergone by a small number of tungsten atoms.