Nanowire-assembled CoO@NiS core-shell hierarchical with enhanced electrochemical performance for asymmetric supercapacitors.

In this study, a three-dimensional (3D) hierarchical CoO@NiS core-shell heterostructure supported on nickel foam (NF) has been constructed. This CoO@NiS/NF can directly serve as a binder-free electrode for a pseudocapacitor, which could achieve a high specific capacitance of 1395.3 F g at a current density of 1 A g in 6 M KOH electrolyte, and an ideal rate capability of 711 F g at a current density of 10 A g. Additionally, the electrode has a high capacitance retention of 89.9% after 5000 cycles. The asymmetric supercapacitor exhibits the maximum energy density of 61.34 W h kg at a power density of 800 W kg, as well as an excellent cycling life of 89.3% capacitance retention. The enhanced electrochemical performance can be mainly ascribed to the special 3D core-shell nanowire arrays nanostructure with great conductivity, enlarged surface area, abundant accessible active sites and intrinsic stability. We anticipate that the present CoO@NiS/NF could be a promising electrode material for energy storage applications.