Promising thin films (WO1.05S2 and WO1.35S2.2) as positive electrode materials in microbatteries

Tungsten oxysulfide thin films (WOySz) have been prepared by reactive radio-frequency magnetron sputtering using a WS2 target and a mixture of argon and oxygen gas. The composition, the texture and the structure depend on the sputtering parameters, such as the oxygen partial pressure and the total pressure (Ar+O2). For a total pressure of 1 Pa, the range of the chemical composition is wide, from WS2 when no oxygen gas is introduced in the chamber, to WO3S0.02 when the oxygen partial pressure is equal to 10−2 Pa. Two amorphous thin films (WO1.05S2 and WO1.35S2.2) have given promising electrochemical performances as positive electrode in the cell: Li/LiAsF6, 1 M EMC/WOySz with a current density up to 37 μA/cm2 between 1.6 and 3 V.