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

Abstract

Novel CoS_x/functionalized multi-walled carbon nanotube (CoS_x/fMWCNTs) shell/core composites are successfully prepared via a simple hydrothermal route. The CoS_x 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 CoS_x/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 CoS_x, CoS_x/CNTs, and CoS_x/graphene. Even at a higher current density of 50 A g⁻¹, the CoS_x/fMWCNTs composites still could deliver a relatively high specific capacitance of 796 F g⁻¹. The CoS_x/fMWCNTs composite electrodes show improved cyclic properties which show about 13% decay in available specific capacity after 2000 cycles. The facile synthesis of the CoS_x/fMWCNTs shell/core composites with superior electrochemical performance may provide a new candidate for energy storage devices with high efficiency.