Engineering firecracker-like beta-manganese dioxides@spinel nickel cobaltates nanostructures for high-performance supercapacitors

Abstract An effective and rational strategy is developed for large-scale growth of firecracker-like Ni-substituted Co3O4 (NiCo2O4) nanosheets on β-MnO2 nanowires (NWs) with robust adhesion as high-performance electrode for electrochemical capacitors. The NiCo2O4–MnO2 nanostructures display much higher specific capacitance (343 F g−1 at current density of 0.5 A g−1), better rate capability (75.3% capacitance retention from 0.5 A g−1 to 8 A g−1) and excellent cycle stability (5% capacitance loss after 3000 cycles) than Co3O4–MnO2 nanostructures. Moreover, an asymmetric supercapacitor based on NiCo2O4–MnO2 NWs as the positive electrode and activated graphenes (AG) as the negative electrode achieves an energy density of 9.4 Wh kg−1 and a maximum power density of 2.5 kW kg−1. These attractive findings suggest this novel core–shell nanostructure promising for electrochemical applications as an efficient supercapacitive electrode.