A new layered vanadium oxide prepared by electrochemical transformation ofa solid precursor

The new vanadium oxide, with the composition (Ca0.13K0.38V2.5V0.5O7.57)-V-I V-O-V.4.3H(2)O, has been prepared by electrochemical oxidation of the solid precursor CaV3O7 in aqueous KClO4 solution. The reaction mechanism is a tw o-phase transformation involving simultaneously calcium extraction, oxygen insertion, and Ca2+/K+ ion exchange. This poorly crystallized compound has a layered structure, with interlayer Ca2+, K+, and H2O, related to that of V2O5 xerogels and electrolytic V2O5 The anhydrous Ca0.13K0.38V3O7.57 compou nd reversibly intercalates 2.3 Li per formula unit (210 mAh g(-1)) at a slo w rate in the 1.5-4 V range, whereas the CaV3O7 precursor does not intercal ate any lithium under similar conditions. Preliminary cycling data indicate that the capacity depends on the cycling rate and decreases during cycling . (C) 2001 The Electrochemical Society. All rights reserved.