Exploring the synergetic electrochemical performance of cobalt sulfide/cobalt phosphate composite for high-energy and rate capability supercapattery applications

Abstract Besides the momentous outcomes in terms of specific energy and specific power, the supercapattery still craves the electrode material with splendid electrochemical performance and stability potential. Here we have synthesized cobalt sulfide and cobalt phosphate via the sonochemical approach and then their composition in binary composite was optimized. The XRD and SEM analysis depict the formation of CoS nanomaterials, Co3(PO4)2 nanoflakes, and their binary composites. Further, the three electrode assembly was employed to explore the electrochemical behavior. The composite having composition cobalt sulfide 75 % and cobalt phosphate 25 % delivers the prime charge storage performance, owning a specific capacity of 451.3 C/g at a cost of 3 mV/s and 436.9 C/g (with a specific capacitance of 728.2 F/g) while operating at 0.6 A/g. This optimized composition was further employed in an asymmetric architecture (supercapattery) as a positive electrode material along negative electrode bearing activated carbon. An outstanding specific capacity of 275 C/g was obtained by the fabricated supercapattery device at 1 A/g. The device retained 53.41 % of the maximum specific capacity even at 16 A/g. Moreover, the real device provides remarkable specific energy of 63.93 Wh/kg along with specific power of 850 W/kg at 1 A/g. The supercapattery was able to deliver a marvelous specific power of 13600 W/kg while still providing impressive specific energy of 34.68 Wh/kg for 16 A/g. Furthermore, excellent capacity preservation of 95.10 % was achieved after 5000 continuous charge discharge cycles. The supercapattery performance was also analyzed in terms of capacitive and diffusive contributions. To the best of our knowledge, this is the first approach toward the utilization of metal sulfide and phosphate in a combination that provides synergetic electrochemical performances. This leads to a new path toward the development of self-supported electrode material for potential energy storage applications.