Advanced asymmetric supercapacitor with NiCo2O4 nanoparticles and nanowires electrodes: A comparative morphological hierarchy

In the present work, hydrothermal and wet chemical methods are adopted to fabricate NiCo2O4 nanowires (NiCo-NW) and NiCo2O4 nanoparticles (NiCo-NP) respectively. Owing to the mesoporous nature of these subunits, fast and convenient electron-ion transport and redox reaction, NiCo-NW achieves excellent electrochemical performance. Structure and microstructural characterizations of these samples are carried out by analyzing X-ray diffraction data employing the Rietveld method of structure refinement method and analyzing HRTEM, FESEM images and FTIR spectra. The low dimensional NiCo-NP is found to provide superior electrochemical performance than the NiCo-NW (similar to 13 nm) due to its smaller particle size (similar to 9 nm). This porous structure effectively helps in better transport of ions in the electrolyte. It manifests high specific capacitance 1066.03 F g(-1) and enormous areal capacitance up to 5.96 F cm(-2) whereas NiCo-NW exhibits specific capacitance up to 880.72 F g(-1) and high areal capacitance of 4.93 F cm(-2). An asymmetric supercapacitor (ASC) has been fabricated with NiCo-NP and activated carbon as positive and negative electrodes respectively in 1 M Na2SO4 electrolyte medium. This device offers maximum specific energy 59.56 Wh Kg(-1) and maximum power density 3403 W kg(-1) with a high energy density of 4.197 Wh Kg(-1) and shows excellent cyclic stability. (C) 2019 Elsevier B.V. All rights reserved.