Hexagonal prism-like hierarchical Co9S8@Ni(OH)2 core-shell nanotubes on carbon fibers for high-performance asymmetric supercapacitors

In this work, novel hierarchical cobalt sulfide@ nickel hydroxide [Co9S8@Ni(OH)(2)] core-shell nanotube arrays supported on carbon fibers have been designed logically and synthesized for use as supercapacitors. The one-dimensional Co9S8 nanotubes (NTs) serve as an ideal backbone to improve the electrical conductivity of Ni(OH)(2) nanosheets, whereas the ultrathin and redox active Ni(OH)(2) nanosheets electrodeposited on the Co9S8 NTs greatly enhance the surface area and provide more electroactive sites for faradaic reaction. The optimized Co9S8@Ni(OH)(2) electrode shows high specific capacitances of 149.44 mA h g(-1) at the current density of 1 A g(-1) and 75 mA h g(-1) even at 10 A g(-1). An asymmetric supercapacitor was successfully assembled with this unique hybrid nanostructure as the anode and an active carbon film as the cathode. The as-fabricated device shows high energy density (31.35 W h kg(-1) at 252.8 W kg(-1)), high power density (2500 W kg(-1) at 12.5 W h kg(-1)), as well as a long-term cycle stability (97.3% retention of its initial capacitance after 5000 cycles). The as-prepared hierarchical nanostructure shows great potential as a promising electrode material for energy storage applications.