Facial synthesis of reduced graphene oxide – Amorphous nickel tungstate composite for flexible hybrid asymmetric solid state supercapacitor application

Abstract

Supercapacitors are crucial as an additional type of energy storage device assisting various types of energy storage systems for high power requirement. Herein, using successive ionic layer adsorption and reaction (SILAR) method, thin films of reduced graphene oxide (rGO) composited with nickel tungstate (NiWO4) were synthesized with different rGO content. The synthesized material showed spherical morphology with rGO sheets and a specific surface area in the range of 85 to 107 m2 g−1. The three-electrode method was used, and the electrochemical performance of rGO-NiWO4 films was assessed in 2 M KOH electrolyte. A composite film deposited at 12 mg mL−1 concentration of rGO (CNW3) film exhibited a specific capacitance of 779 F g−1 at a current density of 2 A g−1. At a current density of 4 A g−1, CNW3 film showed outstanding electrochemical stability with 95 % capacitance retention after 5000 galvanostatic charge-discharge (GCD) cycles. This study emphasizes the usage of rGO-NiWO4 (CNW3) thin films deposited using SILAR method as a cathode in solid-state asymmetric supercapacitors (ASC). The rGO-NiWO4/PVA-KOH/AC ASC device exhibited a specific capacitance of 94.2 F g−1 at 5 A g−1, a specific energy of 33.5 Wh kg−1 and a specific power of 12.37 kW kg−1 with 83 % capacitance retention after 5000 GCD cycles. This suggests that rGO-NiWO4 thin film produced using SILAR method is a suitable candidate for supercapacitors.