Hassle-free solvothermal synthesis of NiO nanoflakes for supercapacitor application

Highlights: • Simple solvothermal synthesis of NiO nanoflakes. • Use of unique mixed solvent system for the solvothermal synthesis. • Nanomaterial exhibits good specific capacitance and coulombic efficiency. • NiO nanoflakes show high rate capability and high cyclic stability. A mixed solvent solvothermal approach was employed for the synthesis of NiO (NO) nanostructures under a low temperature route. The nanoflakes when studied for its electrochemical performance in a 3-electrode method in aqueous 2 M KOH revealed a high capacitance value of 305.0 F g⁻¹ at a scan rate of 5 mV s⁻¹ apart from good rate capability, cyclic stability and coulombic efficiency. The fabricated symmetrical supercapacitor device also showed good electrochemical performance of pseudocapacitive nature with a high power density of 8000.0 W kg⁻¹. The extent of surface sites taking part in the electrochemical processes reveals the enhanced performance is due to the high surface area of NO with a mesoporous structure. The enhanced conductivity of the nanoflakes also provided an unhindered path way for the ionic transport. The promising results reveal that the synthetic technique employed could be extended to other oxides as well.