Reversible lithium intercalation in alkali metal vanadium bronzes (MxV6O13+δ, where M = K, Rb or Cs)

Thermal treatment of electrochemically prepared crystalline solid solutions of ammonium hexavanadates containing K, Rb or Cs formed adherent electrodes on a conducting substrate without the need for binders. These MxV6O13+δ bronzes where M = K, Rb or Cs belong to the ternary system V2O4---V2O5-M2O. By controlling the electrodeposition/decomposition processes, various alkali metal to vanadium ratios (0.0 to 0.65) and oxygen to vanadium ratios (2.2 to 2.5) were studied. The RbV6O13+δ bronzes have not been studied, they are reversible to lithium insertion. For maximum capacity, only small amounts of the alkali metal could be present. Voltage plateaus for small M/V ratio bronzes were similar to V2O5 for electrodes made by thermal decomposition in air, and to V6O13 when heated under a vacuum atmosphere.