Carbon nanotubes/cobalt sulfide composites as potential high-rate and high-efficiency supercapacitors

► The annealed CNT/CoS composites provide 2140 ± 90 F g−1 for specific capacitance. ► CNT/CoS composites yield high-power density at a current density of 217.4 A g−1. ► CNT/CoS supercapacitors demonstrate great potential as energy storage devices.