Preparation and characterization of lithium trivanadate thin films by spray pyrolysis method for supercapacitor applications

The lithium trivanadate (LiV3O8) thin films were deposited over stainless steel (SS) substrates by spray pyrolysis method. The material deposited at an optimized substrate temperature of 350 degrees C and at an annealing temperature of 500 degrees C (LV350_500/SS) performed better in electrochemical properties. The structural and surface morpho-logical characteristics of the as deposited materials were determined using the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses. The stable V5+ state was observed for the as-prepared LiV3O8 thin film in the X-ray photoelectron (XPS) spectrum. The electrochemical performance of the thin films were characterized using a three-electrode configuration with Ag/AgCl as the reference electrode, thin film material as the working electrode, and the platinum wire as the counter electrode. The 1 M LiNO3 aqueous solution was taken to be the electrolyte. LV350_500/SS made using a Li/V molar concentration of 0.1: 0.3 displayed an initial specific discharge capacitance value of 695 Fg-1 at a current density of 0.25 Ag-1, in the voltage range of-0.4 V to 0.4 V. But, the LV350_500/SS prepared using Li/V molar concentration of (0.05: 0.15) showed a low specific capacitance value of 181 Fg-1. A symmetric supercapacitor device made with the LV350_500/SS thin film as the electrodes and poly(vinylidene fluoride-co-hexafluoropropylene)/2D Graphene Oxide (PVdF-HFP/GO) composite polymer membrane as the electrolyte showed an excellent specific discharge capacitance value of 31 Fg-1 for a current density of 0.25 Ag-1. The calculated specific energy density and specific power density values were found to be 69 Whkg-1 and 1002 Wkg-1 respectively, for the above sym-metric device.