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

We have prepared carbon nanotube (CNT)/cobalt sulfide (CoS) composites from cobalt nitrate, thioacetamide, and CNTs in the presence of poly(vinylpyrrolidone). CNT/CoS composites are deposited onto fluorine-doped tin oxide glass substrates and then subjected to simple annealing at 300 °C for 0.5 h to fabricate CNT/CoS electrodes. Data collected from Raman spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and d-spacing reveal the changes in the CoS structures and crystalline lattices after annealing. Cyclic voltammetry results reveal that the annealed CNT/CoS composite electrodes yield values of 2140 ± 90 and 1370 ± 50 F g ^-1 for specific capacitance at scan rates of 10 and 100 mV s ^-1, respectively. To the best of our knowledge, the annealed CNT/CoS composite electrodes provide higher specific capacitance relative to other reported ones at a scan rate of 100 mV s ^-1. CNT/CoS composite electrodes yield a power density of 62.4 kW kg ^-1 at a constant discharge current density of 217.4 A g ^-1. With such a high-rate capacity and power density, CNT/CoS composite supercapacitors demonstrate great potential as efficient energy storage devices.