Amorphous CoSx nanoparticles anchoring onto N-doped carbon nanotubes as high-performance electrodes for hybrid supercapacitors

Highlights: • Amorphous CoS_x nanoparticles are anchored onto N-CNTs to form nanocomposites. • A diffusion-controlled charge storage behavior prevails in CoS_x/N-CNTs electrodes. • CoS_x/N-CNTs nanocomposites exhibit enhanced rate capabilities and cyclic stability. • Amorphous CoS_x and N-CNTs work together to improve the energy storage property. -- Abstract: Cobalt sulfide has been considered as one kind of promising battery-type electrode material (BTEM) for hybrid supercapacitors (HSCs). However, unsatisfactory rate capability and cyclic stability still hinder its further practical application in high-performance HSCs. Here, amorphous CoS_x nanoparticles are anchored onto N-doped carbon nanotubes (N-CNTs) to form CoS_x/N-CNTs nanocomposites by a chemical bath deposition (CBD) and subsequent sulfurization reaction. Originating from the synergistic effect of amorphous CoS_x nanoparticles and flexible N-CNTs conductive backbones in the nanocomposites, the prepared CoS_x/N-CNTs nanocomposites exhibit enhanced specific capacities (899 C g⁻¹ at 3 A g⁻¹ and 611 C g⁻¹ at 20 A g⁻¹) and long-term cyclic stability (initial capacity retention of 94% after 5000 cycles at 10 A g⁻¹) compared with CoS_x and N-CNTs electrodes. In addition, a HSC device is fabricated using CoS_x/N-CNTs and N-CNTs as the positive and negative electrodes, respectively, which can deliver an energy density of 51.9 Wh kg⁻¹ at a power density of 800 W kg⁻¹. Therefore, the constructed CoS_x/N-CNTs nanocomposites hold promise for designing high-performance cobalt sulfide-based electrode materials for further practical application in HSCs.