Browsing by Author "C.K. Ranaweera"

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High per formance and flexible supercapacitors based on carbonized bamboo fibers for wide temperature applications
(Nature Publishing Group, 2016) Camila Zequine; C.K. Ranaweera; Z. Wang; Sweta Singh; Prashant Tripathi; O.N. Srivastava; Bipin Kumar Gupta; K. Ramasamy; P.K. Kahol; P.R. Dvornic; Ram K. Gupta
High performance carbonized bamboo fibers were synthesized for a wide range of temperature dependent energy storage applications. The structural and electrochemical properties of the carbonized bamboo fibers were studied for flexible supercapacitor applications. The galvanostatic charge-discharge studies on carbonized fibers exhibited specific capacity of ∼510F/g at 0.4 A/g with energy density of 54 Wh/kg. Interestingly, the carbonized bamboo fibers displayed excellent charge storage stability without any appreciable degradation in charge storage capacity over 5,000 charge-discharge cycles. The symmetrical supercapacitor device fabricated using these carbonized bamboo fibers exhibited an areal capacitance of ∼1.55 F/cm 2 at room temperature. In addition to high charge storage capacity and cyclic stability, the device showed excellent flexibility without any degradation to charge storage capacity on bending the electrode. The performance of the supercapacitor device exhibited ∼65% improvement at 70 °C compare to that at 10 °C. Our studies suggest that carbonized bamboo fibers are promising candidates for stable, high performance and flexible supercapacitor devices. © The Author(s) 2016.
High-Performance Flexible Supercapacitors obtained via Recycled Jute: Bio-Waste to Energy Storage Approach
(Nature Publishing Group, 2017) Camila Zequine; C.K. Ranaweera; Z. Wang; Petar R. Dvornic; P.K. Kahol; Sweta Singh; Prashant Tripathi; O.N. Srivastava; Satbir Singh; Bipin Kumar Gupta; Gautam Gupta; Ram K. Gupta
In search of affordable, flexible, lightweight, efficient and stable supercapacitors, metal oxides have been shown to provide high charge storage capacity but with poor cyclic stability due to structural damage occurring during the redox process. Here, we develop an efficient flexible supercapacitor obtained by carbonizing abundantly available and recyclable jute. The active material was synthesized from jute by a facile hydrothermal method and its electrochemical performance was further enhanced by chemical activation. Specific capacitance of 408 F/g at 1 mV/s using CV and 185 F/g at 500 mA/g using charge-discharge measurements with excellent flexibility (∼100% retention in charge storage capacity on bending) were observed. The cyclic stability test confirmed no loss in the charge storage capacity of the electrode even after 5,000 charge-discharge measurements. In addition, a supercapacitor device fabricated using this carbonized jute showed promising specific capacitance of about 51 F/g, and improvement of over 60% in the charge storage capacity on increasing temperature from 5 to 75 °C. Based on these results, we propose that recycled jute should be considered for fabrication of high-performance flexible energy storage devices at extremely low cost. © 2017 The Author(s).
Nanostructured cobalt oxide and cobalt sulfide for flexible, high performance and durable supercapacitors
(Elsevier B.V., 2017) S. Aloqayli; C.K. Ranaweera; Z. Wang; K. Siam; P.K. Kahol; P. Tripathi; O.N. Srivastava; Bipin Kumar Gupta; S.R. Mishra; Felio Perez; X. Shen; Ram K. Gupta
Transition metal oxides and sulfides have great potential for energy storage devices due to their large theoretical energy storage capacities. A facile technique was used for the synthesis of nanostructured and phase pure cobalt oxide (Co3O4) and subsequently converting it to cobalt sulfide (Co9S8). The effect of sulfurization on energy storage capacity of the cobalt oxide was explored. Microstructural characterizations using X-ray diffraction and scanning electron microscopic reveal formation of phase pure and nanostructured Co3O4 and Co9S8. It was observed that the areal capacitance of Co3O4 (983 mF/cm2) improved significantly after converting to Co9S8 (7358 mF/cm2). The CV curves of the Co9S8 electrode on bending showed outstanding stability with no change in energy storage properties. New insights into the better performance of Co9S8 over Co3O4 based on electrochemical investigations are presented. The performance of the Co9S8 as an electrode material for energy storage applications was further investigated by fabricating a supercapacitor device. The supercapacitor device showed outstanding stability up to 5000 cycles of charge-discharge study. The performance of the supercapacitor was observed to be improving with temperature. The supercapacitor displayed ~100% enhancement in energy storage property on increasing temperature from 10 to 70 °C. Our results suggest that hydrothermally grown Co9S8 on nickel foam can be utilized for high capacity, flexible and binder free electrode for energy storage applications. © 2017 Elsevier B.V.