In-situ deposition of amorphous Tungsten(VI) oxide thin-film for solid-state symmetric supercapacitor

Abstract

Amorphous tungsten (VI) trioxide thin films were deposited on rigid Ni-foam and flexible PET substrates using RF magnetron sputtering technique. The impacts of sputtering RF power on microstructure, morphology, compositional and electrochemical properties of the deposited thin films were investigated by using Raman, FE-SEM, XPS and electrochemical techniques. The thicknesses of the deposited films were increased from 70 to 105 μm as a function of RF power. The films contain uniform nanoparticles and the observed sizes are in the range of 25–70 nm. The films of WO 3 @Ni and WO 3 @PET deposited at an optimum RF power of 100 W exhibited the high areal capacitance of 22.01 mF/cm 2 and 9.76 mF/cm 2 with good cyclic retention of 81.03% and 69.53% after 5000 cycles respectively. Further, two solid-state symmetric supercapacitor (SSC) devices were assembled which shows pseudocapacitive behaviour. The devices delivered moderate energy densities of 0.48 μWh/cm 2 and 0.20 μWh/cm 2 and power densities of 312 μW/cm 2 and 150 μW/cm 2 for rigid Ni foam and flexible PET based devices respectively. This result demonstrated that the binder free in-situ deposition of WO 3 films deposited at an optimum RF power of 100 W is more suitable to fabricate supercapacitor devices.