Binder‐Free Synthesis of Mesoporous Nickel Tungstate for Aqueous Asymmetric Supercapacitor Applications: Effect of Film Thickness

Abstract

Nickel tungstate thin films of different thicknesses are synthesized using the binder‐free successive ionic layer adsorption and reaction (SILAR) method at ambient temperature and subsequent calcination at a temperature of 727 K. The physicochemical characterizations of NiWO 4 thin films are carried out using different techniques. The electrochemical performances of NiWO 4 films are evaluated in 2 m KOH electrolyte using a standard three electrode system. The specific capacitance of 1536 F g −1 at the current density of 2 A g −1 is obtained for the NiWO 4 film. The film exhibits excellent electrochemical stability of 87% after 5000 galvanostatic charge–discharge (GCD) cycles at the current density of 3 A g −1 . This study highlights use of SILAR‐deposited NiWO 4 thin films as a cathode in aqueous asymmetric supercapacitors (ASCs). The ASC device NiWO 4 /KOH/Fe 2 O 3 exhibits a specific capacitance of 115 F g −1 at 2 A g −1 and specific energy of 23Wh kg −1 at specific power of 1.2 kW kg −1 . The device shows remarkable electrochemical cycling stability (78% capacitance retention after 5000 GCD cycles). The SILAR‐deposited NiWO 4 thin films are expected to emerge as a potential candidate for supercapacitors.