Development of energy storage devices with high energy performance, power density, fast charge-discharge capability and long cyclability is needed to meet the increasing demand for energy, power and environmental protection in our daily life. Supercapacitors have great potential in future energy storage devices with magnificent properties. Recently, researchers have shown great progress for the improvement of supercapacitor performance by fabrication of nanostructured transition metal chalcogenides materials. One of the main objectives of this thesis is to synthesize nanostructured cobalt oxide and then converte them to cobalt sulfide using a facile hydrothermal method. The synthesized cobalt oxide and cobalt sulfide were structurally and electrochemically characterized. The structural characterizations were performed using X-ray diffraction and scanning electron microscopy. The electrochemical properties were studied using a standard three-electrode cell containing a platinum wire as a counter electrode, saturated calomel electrode as a reference electrode, and synthesized materials as a working electrode. The energy storage capacity was investigated using cyclic voltammetry (CV) and galvanostatic charge-discharge techniques. Cobalt oxide and cobalt sulfide showed specific capacitances of 983 and 7358 mF/cm2 at 2 mA/cm2, 5 respectively. The electrochemical properties of cobalt oxide have been improved significantly after converting to cobalt sulfide. Moreover, the effect of temperature on the electrochemical properties of the supercapacitor device fabricated using cobalt sulfide was studied. It was observed that the charge storage capacity of the device increased with increase in the temperature, which could be due to decrease in series resistance of the device. Our results suggest that cobalt sulfide could be used as an advanced material for energy storage applications
