Charging Capacity and Cycling Stability of VOx Films Prepared by Pulsed Laser Deposition

The lithium ion charging capacity and cycling stability of vanadium oxide thin-films prepared by pulsed laser deposition (PLD) are reported. PLD films were prepared at various temperatures and atmospheres from a V₆O₁₃ target. The charging capacity of these films depended strongly on the substrate deposition temperature and atmosphere. The best crystalline films were grown at 200°C. Crystalline oriented V₂O₅ films were prepared by PLD at 200°C in an oxygen environment. These films can be cycled in the voltage range between 4.1 and 2.0 V for more than 100 cycles with very little capacity loss. The specific charge capacity of the films was 340 Ah/kg when the discharge current density was 0.1 mA/cm², which corresponds to 1.2 lithium atoms per vanadium atom. The capacity increased to 1.5 lithium atoms per vanadium atom when cycled at a current density of 0.02 mA/cm². Amorphous vanadium oxide films with similar specific capacities were prepared by PLD in vacuum at 200°C. The capacity loss in these films was less than 2% after 100 cycles. Although thermally evaporated vanadium oxide films had similar initial capacities under the same charging conditions, they lost more than 17% of their charging capacity after 100 cycles. The improved cycle stability in the amorphous vanadium oxide films may be partially attributed to the improved surface morphology of the PLD films.