Nanostructured NiCo2O4 embedded on biowaste derived hierarchical porous activated carbon for high performance symmetric and asymmetric supercapacitor device

Abstract

Hybrid supercapacitors have received much more limelight due to its enhanced specific capacitance and energy density without altering power density than their individual components. In present study, Nickel cobaltite nanostructures are embedded on the activated carbon using dip dry method followed by chemical bath deposition. The activated carbon was prepared from the sustainable and low cost bio waste precursor; Terminalia catappa leaves. The effect of mass ratio of activated carbon and nickel cobaltite on the electrochemical performance of Nickel cobaltite/activated carbon composite thin films has been studied successfully. An optimized NCO-C20 thin electrode showed specific capacitance of 1387.4 F/g at 1 mA/cm2 and excellent rate capability of 90 % (5 mA/cm2). It delivered energy density of 29.30 Wh/kg at a power density of 162.5 W/kg and exhibited cyclic stability of 97.6 % over 5000 cycles. Practical feasibility of NiCo2O4/activated carbon composite electrode was demonstrated by fabricating all solid state symmetric and asymmetric device. As fabricated symmetric device (NCO-C20//NCO-C20) possess specific capacitance of 112.7 F/g and energy density of 22.55 Wh/kg at a power density of 937.6 W/kg at 5 mA/cm2. The asymmetric device (NCO-C20//AC) exhibited specific capacitance of 64.16 F/g and energy density of 28.87 Wh/kg at power density of 1800 W/kg at 6 mA/cm2. Asymmetric device showed outstanding cyclic stability of 80 % after 5000 CV cycles. The results manifests that composite thin films prepared from biomass derived porous carbon and NiCo2O4 nanostructure can make it noteworthy electrode material for energy storage applications.