VANADIUM-OXIDE XEROGELS AS ELECTRODES FOR LITHIUM BATTERIES

Vanadium oxide xerogels V2O5 . nH2O are investigated as insertion electrode materials for secondary lithium batteries. Lithium insertion into these materials is shown to be fully reversible when all the loosely bound water is removed by proper heat treatments. The disordered xerogels obtained after heat treatment at 100-degrees-C in vacuum, where the reversibly bound water is removed, are able to insert nearly 1.5 Li/V2O5. The more crystalline films obtained after heat treatment at 300-degrees-C, where most of the chemically bound water is removed, insert up to 2 Li/V2O5 at potentials above 1.5 V vs. Li, corresponding to a stoichiometric energy density of 730 Wh kg-1. Analysis of differential capacity curves show that lithium ions are accommodated at sites in the xerogel host that are different from the sites occupied in orthorhombic V2O5. It is also noted that the xerogel host is more stable towards lithium insertion, retaining its structure after repeated cycling to a depth of 2 Li/V2O5.