Ni3S2@CoS core-shell nano-triangular pyramid arrays on Ni foam for high-performance supercapacitors.

In this study, we demonstrate a facile method to fabricate novel Ni3S2 nano-triangular pyramid (NTP) arrays on Ni foam through a hydrothermal process and build unique Ni3S2@CoS core-shell NTP arrays by electro-deposition. The obtained Ni3S2@CoS material displays twice the specific capacitance of the pure Ni3S2 material in both a three-electrode system (4.89 F cm(-2) at 4 mA cm(-2)) and asymmetric supercapacitor device (0.69 F cm(-2) at 1.43 mA cm(-2)). In addition, the asymmetric supercapacitor demonstrates the outstanding energy density of 28.24 W h kg(-1) at a power density of 134.46 W kg(-1), with a stable cycle life (98.83% retained after 2000 cycles). The unique structure of the Ni3S2@CoS core-shell NTP arrays, which provides an ultra-thin CoS shell to enlarge efficient areas, introduces good conductivity, and short transportation lengths for both ions and electrons, contributes most to its excellent performance. Moreover, the bare Ni3S2 NTP arrays can be used as a new template to build other potential electrode materials.