Lithium electrochemical intercalation in β-VOSO4

A new low-temperature route for beta-VOSO4, synthesis is proposed, involving reduction in sulphuric acid in the presence of sulphur. Lithium intercalation has been performed on this material, both chemically and electrochemically and the compounds have been characterized by XRD as well as IR and Raman spectroscopy. From potentio-dynamic and galvano-static electrochemical studies it is shown that intercalation occurs in two steps, firstly with a structural change at 2.84 V vs. Li metal, then in a solid solution domain. The process appears partly reversible and the system is shown to present a good cycling behavior on almost 0.6 e(-) per transition metal. From these results it appears that the energy, of redox transition metal couples involving VO2+ structural units in octahedral coordination is between those observed in oxides and in M-2(XO4)(3) (X = S, P, As) compounds, respectively. (C) 1997 Elsevier Science S.A.