Novel synthesis of hierarchical NiGa2O4@MnO2 core-shell hetero-nanostructured nanowall arrays on carbon cloth for high-performance all-solid-state asymmetrical supercapacitors

Abstract A hierarchical NiGa2O4@MnO2 core-shell nanowall arrays have been grown on carbon cloth by stepwise design and fabrication. Ultrathin MnO2 nanoflakes are revealed to grow uniformly on the porous NiGa2O4 nanowalls with many interparticle mesopores, resulting in the formation of 3D core-shell nanowall arrays with hierarchical architecture. The as-synthesized product as a binder-free electrode possesses a high specific capacitance of 1700 F g−1 at 1 A g−1 and 90% capacitance retention after 10,000 cycles at 10 A g−1. Furthermore, an asymmetrical solid-state supercapacitor assembled by the NiGa2O4@MnO2 and N-CMK-3 exhibits an energy density of 0.59 Wh cm−3 at a power density of 48 W cm−3, and excellent cycling stability (80% of initial capacitance retention after 5000 cycles at 6 mA cm−2). The remarkable electrochemical performances can be attributed to its novel nanostructure with high surface area, convenient ion transport paths and favorable structure stability. These results display an effective method for fabrication of different core-shell nanostructure on conductive substrates, which brings new design opportunities of device configuration for next energy storage devices.