LITHIUM ELECTROCHEMICAL INTERCALATION IN BETA-VOSO4

A new low-temperature route for beta-VOSO4, synthesis is proposed, inv olving reduction in sulphuric acid in the presence of sulphur. Lithium intercalation has been performed on this material, both chemically an d electrochemically and the compounds have been characterized by XRD a s 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 reversibl e 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 u nits in octahedral coordination is between those observed in oxides an d in M-2(XO4)(3) (X = S, P, As) compounds, respectively. (C) 1997 Else vier Science S.A.