Lithium insertion in sputtered vanadium oxide film

Abstract

Vanadium oxide films have been prepared by RF-sputtering using an oxygen containing sputter gas and a V 2O 5 target. The main component of these films is orthorhombic V 2O 5 with poor crystallinity and a tendency for ordering of the crystallites with the c-direction parallel to the substrate. All films were oxygen deficient compared to V 2O 5. Films prepared in pure argon were reduced to V(4) or lower. The vanadium oxide films were tested in solid-state lithium cells. Films sputtered in oxygen showed electrochemical properties similar to crystalline V 2O 5. The main differences are a decreased capacity above 3.0 V, showing that V is partially reduced, and a broadening of the capacity peaks, showing that the crystallinity of these films is rather low. The film sputtered in argon behaved differently, discharging at a very low potential, 1.9 V versus Li, in the first cycle. In subsequent cycles the average insertion potential was increased due to a structural distortion of the host.