Fe doped NiCo2O4@rGO nanosheets network boost electrochemical kinetics for high energy density and stable asymmetric coin cell supercapacitor

Doping in transition metal oxides open an opportunity to tailor their properties for energy storage application. In this work, Fe doped NiCo2O4@rGO (Fe-NiCo2O4@rGO) nanosheets network were prepared and investigated as electrode for supercapacitor. It is found that Fe doping generates rich oxygen vacancies while addition of rGO increases the surface area. Moreover, DFT calculations show the improved conductivity as well as increase in active sites leading to improved reaction kinetics. These features make Fe-NiCo2O4@rGO nanosheets an exceptional candidate as an electrode material for supercapacitors. It has been revealed that Fe-NiCo2O4@rGO electrode delivered higher specific capacitance of 1252 F g- 1 at a current density of 1 A g- 1 in 1.0 M neutral Na2SO4 solution, as compared to Fe-NiCo2O4 (950 F g- 1) and NiCo2O4 (610 F g- 1) electrodes. Interestingly, the assembled asymmetric coin cell supercapacitor (Fe-NiCo2O4@rGO//AC) delivers superb specific capacitance of 182 F g- 1 at 1 A g- 1 and achieved an outstanding energy density of 57.1 Wh kg- 1 at a power density of 670.5 W kg- 1. Moreover, the device retains its stability for 10,000 cycles at 4 A g- 1 with a capacitance retention of 94.3 %. These results suggest that Fe-NiCo2O4@rGO nanosheets network could be an emerging electrode material with high feasibility value for future energy storage systems, especially supercapacitors.