Bi2O3 nanosheet-coated NiCo2O4 nanoneedle arrays for high-performance supercapacitor electrodes

Supercapacitors are a promising option for next-generation clean energy storage devices, although their capacitance must still be improved through an appropriate choice of electrode material. Herein, NiCo2O4 nanoneedles coated with Bi2O3 nanosheets are successfully prepared using a two-step hydrothermal process to produce electrodes that may be used for supercapacitors. The proposed electrodes are analyzed using both a range of experimental measurement techniques and density functional theory simulations. The NiCo2O4 nanoneedles provide an ideal skeleton for improving specific surface area and present electrical active sites for the Faraday reaction, while Bi2O3 nanosheets have a great potential for use in supercapacitor applications. The proposed NiCo2O4@Bi2O3 electrode shows a high capacity of 766 F g−1 at 1 A g−1. In addition, an asymmetric supercapacitor based on a NiCo2O4@Bi2O3 positive electrode and activated carbon was produced, which provided a working voltage of 1.6 V, achieved a high energy density of 24 Wh kg−1 at 800 W kg−1, and demonstrated excellent cycling stability (capacitance retention of 82 % after 10,000 cycles at 10 A g−1). These results demonstrate that the proposed NiCo2O4@Bi2O3 heterostructure exhibits potential for application in high-performance supercapacitors.