With increasing demand for energy and environmental protection, it is essential to develop low cost, earth abundant and environment friendly materials for energy storage applications. Our work demonstrates that transition metal chalcogenides could be used for energy storage applications such as supercapacitors. Supercapacitors are different than batteries as they provide higher power density and long cycle life. In this work, we have synthesized cobalt sulfide using a facile hydrothermal method. The synthesized cobalt sulfide was structurally and electrochemically characterized for its application in flexible energy storage devices. X-ray diffraction analysis confirms the phase purity of the synthesized cobalt sulfide (Co9S8). Scanning electron microscopic analysis confirms nanostructured nature of the cobalt sulfide. Flexibility test was performed at room temperature by measuring cyclic voltammogram (CV) at various bending angles. The CV curves of the Co8S9 electrode at various bending angles were identical in shape, indicating high electrochemical bending stability. A supercapacitor device was fabricated and the performance was tested at room temperature and elevated temperatures. The CV curves of the supercapacitor at various scan rates showed decrease in specific capacitance with increase in scan rate. The maximum specific capacitance of about 1,000 mF/cm2 was observed. The long term electrochemical stability of the supercapacitor device was examined using galvanostatic charge-discharge method. The device showed outstanding cyclic stability with almost 100% capacity retention. The effect of temperature on the electrochemical properties of the device was investigated. The area under the CV curves was found to increasing with increase in temperature, indicating an improvement in the charge storage capacity of the device. In addition, the shape of the CV curves was found to be identical suggesting high electrochemical stability of the device even at elevated temperatures. The device showed about 100% improvement in charge storage capacity on increasing temperature from 10 to 70 oC. Our studies suggest that cobalt sulfide could be used as an electrode material for flexible energy storage device which could even better operate in harsh conditions.

Flexible energy storage device based on nanostructured cobalt sulfide

253rd National Meeting (2017)

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