Cobalt sulfide nanosheets decorated on polypyrrole nanowires for improved charge storage in supercapacitors

Nanostructured cobalt sulfide-based electrode materials for supercapacitors (SCs) still suffer from easy aggregation, sluggish reaction kinetics, and poor structural stability. To resolve these issues, we adopt a two-step electrochemical deposition method to fabricate CoS nanosheets decorated on polypyrrole (PPy) nanowires that grow directly on Ni foam. The PPy nanowires serve as supports for growing CoS nanosheets, which not only make the CoS nanosheets well dispersed but also reduce their size and thickness. In addition, the intensive interaction between CoS and PPy endows the nanoarchitecture with high mechanical strength. Therefore, the constructed PPy@CoS nanocomposites feature abundant electroactive sites, high charge transport and transfer efficiencies, a short ion diffusion distance, and good structural stability. As a result, the optimized PPy@CoS nanocomposites as SC electrodes demonstrate specific capacities of 860C g(-1) at 1 A g(-1) and 595C g(-1) at 20 A g(-1), as well as a 92% initial capacity retention after 5000 cycles at 10 A g(-1). Furthermore, a fabricated asymmetric supercapacitor (ASC) device with PPy@CoS nanocomposites as the positive electrode realizes a specific energy of 51.1 Wh kg 1 at 800 W kg(-1), suggesting a promising potential for their practical application in SCs. This work may provide a feasible strategy for fabricating other metal sulfide/conducting polymer nanocomposites with enhanced charge storage capabilities as SC electrodes.