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With increasing worlds energy and power demand, there is urgency needed in developing high performance and stable materials for energy applications. Supercapacitors hold great potential in future energy storage devices due to their high-energy performance, ability to have high power density, fast charge-discharge capability and long cyclability. Researchers in recent years have been shown significant progress for the improvement of supercapacitor performance and development of cost effective performing materials for energy storage applications. In this work, we have reported the synthesis of nanostructured cobalt oxide (Co3O4) converted into cobalt sulfide (Co8S9) that prepared using a facile hydrothermal method. We have analyzed the obtained nanostructured cobalt sulfide (Co8S9) electrochemically and structurally. The crystallinity and phase purity of the synthesized (Co8S9) nanostructures were evaluated using X-ray diffraction. Morphology and particle size of the synthesized (Co8S9) on nickel foam has been analyzed using scanning electron microscopy (SEM). Electrochemical investigations have carried out systematically on fabricated electrodes. The cyclic voltammograms (CV) of cobalt sulfide electrode showed redox peaks suggesting typical pseudocapacitive behavior. The electrochemical properties of cobalt oxide have been improved significantly after converting to cobalt sulfide, showing specific capacitances of 983 and 7358 mF/cm2 at 2 mA/cm2, respectively. A supercapacitor device fabricated and the performance of the device was examined at room temperature and elevated temperatures using cyclic voltammetry and galvanostatic charge-discharge. Results showed excellent flexibility and cyclic stability with the maximum specific capacitance of 1,000 mF/cm2. Charge storage capacity was increased when the temperature was increased, suggesting improvement in the electrochemical properties of the device at elevated temperatures. Our results indicate that Co8S9 under harsh conditions could be appropriate material for high performance energy storage devices.

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