Polypyrrole-wrapped NiCo2S4 nanoneedles as an electrode material for supercapacitor applications.

In this study, dicobalt tetrasulfide (NiCo 2 S 4) nanoneedles were successfully synthesized by a two-step hydrothermal method on nickel foam. A layer of polypyrrole (PPy) was further wrapped on the surface of the NiCo 2 S 4 nanoneedles by in-situ polymerization. The obtained NiCo 2 S 4 @PPy composite was investigated for supercapacitor applications, which exhibited a capacitance of 1842.8 F g−1 at 1 A g−1. An asymmetric supercapacitor device fabricated with an activated carbon negative electrode and NiCo 2 S 4 @PPy positive electrodes exhibited an energy density of 41.2 Wh kg−1 at 402.2 W kg−1 with a high charge–discharge cycling stability (92.8% after 5000 cycles). These results demonstrate that NiCo 2 S 4 @PPy electrodes have broad application prospects as energy storage electrode materials. [ABSTRACT FROM AUTHOR]