Controlled-Synthesis of Hierarchical NiCo2O4 Anchored on Carbon Nanofibers Mat for Free-Standing and Highly-Performance Supercapacitors

Abstract In this work, a versatile one-step hydrothermal technique was used to produce a hybrid standalone electrode of NiCo2O4 hierarchical nanostructures anchored on CNFs mat for highly-performance and substrate-free supercapacitors. The CNFs mat was working as a conductive and a three-dimensional template for hierarchical NiCo2O4 nanostructures deposition at the same time. The morphological and structural data analysis revealed a pure spinel NiCo2O4 nanostructures with a unique surface morphology comprising interconnected ultrathin nanoneedles and nanoflowers were successfully anchored to the CNFs mat. Real supercapacitors consist of two-symmetrical hybrid electrodes with different NiCo2O4 loading ratios were assembled and tested. The electrochemical performances of the assembled devices in terms of specific capacitance, energy, and power densities were systematically evaluated. Increasing the NiCo2O4 loading on the CNFs mat had shown a positive impact on improving the overall electrochemical performance of the assembled supercapacitors. A hybrid electrode loaded with NiCo2O4 twice as much as CNFs possess a specific capacitance value of 540 F g−1 along with an energy density of 30 Wh kg−1 at a power density of 515.6 W kg−1. In addition, the device showed excellent cycling stability and high capacitance retention against 6000 charge-discharge cycles at a charging current of 1.0 A g−1.