An asymmetric supercapacitor based on NiCo2O4 nanosheets as anode and partially reduced graphene oxides/carbon nanotubes as cathode

Nickel–cobalt oxide has been given more attention to being used as the supercapacitor's electrode materials due to its two-dimensional layered structure, good electron conductivity, and excellent stability. In this work, NiCo2O4 nanosheets were successfully prepared by the simple solvothermal reaction and the thermal treatment process. Under the three-electrode system, it exhibits a maximum specific capacitance of 978 F/g at 1.5 A/g and good cycle stability. Meanwhile, a freestanding of partially reduced graphene oxides/carbon nanotubes (PRGO/CNTs) film was obtained by the vacuum filter and solvothermal methods, which can provide a wide potential window of − 1 ~ 0 V and a maximum specific capacitance of 236 F/g at 0.5 A/g. Finally, an asymmetric supercapacitor of PRGO/CNTs//NiCo2O4 was assembled, which exhibits good electrochemical performance, such as specific capacitance of 82 F/g at 0.5 A/g, energy density of 18.8 Wh/kg at 0.32 kW/kg, and 99.5% of capacitance retention after 5000 cycles at 5 A/g. This test results reveal that PRGO/CNTs//NiCo2O4 ASC has great potential for practical application in energy storage systems.