Aqueous asymmetric supercapacitors based on ZnCo2O4 nanoparticles via facile combustion method

ZnCo2O4 (ZCO) nanoparticles are synthesized via a facile, fast and cost-effective combustion method. The effect of calcination temperature is studied on the morphology, crystallite size and electrochemical properties of the ZCO. Scanning electron microscope observation reveals that the calcination temperature strongly influences the morphology of the prepared ZCO. At the calcination temperatures of 300, 400 and 600 degrees C, the ZCO samples show the specific capacitance values of 202, 668 and 843 F g(-1), respectively with the current density of 1 A g(-1). Furthermore, higher calcination temperature (800 degrees C) leads to rapid increment of particle size, low specific capacitance (432 F g(-1) at 1 A g(-1)) and inferior rate capability of ZCO, which may be related to the severe micro-strain and crack formation upon repeated electrolytic ions during charging-discharging process. Owing to the excellent specific capacitance of the ZCO (prepared at 600 SC), its performance is further investigated in asymmetric supercapacitor (ASC) device and a high energy density of 26.28 W h kg(-1) is obtained at the power density of 716 W kg(-1) under the current density of 1 A g(-1). Parallel-connected 14 light-emitting diodes are lit up from series-connected two ASCs. In addition, a motor fan is powered by the two ASCs. In the light of the above results, the ZCO nanoparticles may be expected to be a prospective viable electrode material for high-performance supercapacitors. (C) 2019 Elsevier B.V. All rights reserved.