Facile synthesis of cobalt sulfide/carbon nanotube shell/core composites for high performance supercapacitors

Novel CoSx/functionalized multi-walled carbon nanotube (CoSx/fMWCNTs) shell/core composites are successfully prepared via a simple hydrothermal route. The CoSx nanoparticles with diameters of about 6 nm are decorated on the carbon nanotubes to form a shell. The electrochemical performance of the composites was investigated using a three-electrode system. The results show that CoSx/fMWCNTs exhibit the highest specific capacitance of 1324 F g(-1) at a current density of 10 A g(-1), better than published results for supercapacitors based on CoSx, CoSx/CNTs, and CoSx/graphene. Even at a higher current density of 50 A g(-1), the CoSx/fMWCNTs composites still could deliver a relatively high specific capacitance of 796 F g(-1). The CoSx/fMWCNTs composite electrodes show improved cyclic properties which show about 13% decay in available specific capacity after 2000 cycles. The facile synthesis of the CoSx/fMWCNTs shell/core composites with superior electrochemical performance may provide a new candidate for energy storage devices with high efficiency.