A New Layered Vanadium Oxide Prepared by Electrochemical Transformation of a Solid Precursor

Abstract
The new vanadium oxide, with the composition Ca0.13K0.38V2.5IVV0.5VO7.57⋅4⋅3H2O,Ca0.13K0.38V2.5IVV0.5VO7.57⋅4⋅3H2O, has been prepared by electrochemical oxidation of the solid precursor CaV3O7CaV3O7 in aqueous KClO4KClO4 solution. The reaction mechanism is a two-phase transformation involving simultaneously calcium extraction, oxygen insertion, and Ca2+/K+Ca2+/K+ ion exchange. This poorly crystallized compound has a layered structure, with interlayer Ca2+,Ca2+, K+,K+, and H2O,H2O, related to that of V2O5V2O5 xerogels and electrolytic V2O5.V2O5. The anhydrous Ca0.13K0.38V3O7.57Ca0.13K0.38V3O7.57 compound reversibly intercalates 2.3 Li per formula unit (210 mAh g−1)mAh g−1) at a slow rate in the 1.5-4 V range, whereas the CaV3O7CaV3O7 precursor does not intercalate any lithium under similar conditions. Preliminary cycling data indicate that the capacity depends on the cycling rate and decreases during cycling. © 2001 The Electrochemical Society. All rights reserved.