Long-Term Stability and Charging Capacity of VOx Films Formed by Pulsed Laser Deposition

The long term stability and lithium ion charging capacities of vanadium oxide thin films prepared by pulsed laser deposition (PLD) are reported in this paper. PLD films were prepared at various temperatures and atmospheres from a sintered target of V6O13 stoichiometry. Vanadium oxide films prepared by thermal evaporation were also evaluated. For PLD films, the charging capacity depended stronglyon the substrate deposition temperature; the best films were grown at 200.degree.C in vacuum. These films exhibit a capacity of .apprx.1.5 lithium per vanadium when cycled at a current density of 0.02 mA/Cm2. The capacity dropped to 1.2 lithium per vanadium when cycled at a current density of 0.1 mA/cm2. The capacity loss in these films is less than 2% after 100 cycles. Although thermallyevaporated films exhibited similar initial capacity under the same charging conditions, they lost more than 17% of charging capacity after 100 cycels. The improved cycle stability can be partially attributed to the improved morphology of the PLD films.