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

Abstract

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 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 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.