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, NiCo 2 O 4 nanoneedles coated with Bi 2 O 3 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 NiCo 2 O 4 nanoneedles provide an ideal skeleton for improving specific surface area and present electrical active sites for the Faraday reaction, while Bi 2 O 3 nanosheets have a great potential for use in supercapacitor applications. The proposed NiCo 2 O 4 @Bi 2 O 3 electrode shows a high capacity of 766 F g −1 at 1 A g −1 . In addition, an asymmetric supercapacitor based on a NiCo 2 O 4 @Bi 2 O 3 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 NiCo 2 O 4 @Bi 2 O 3 heterostructure exhibits potential for application in high-performance supercapacitors.