Urchin-like structure and nanowire arrays of NiCo2O4/NiCoSe2 as a binder-free electrode material for high-performance supercapacitor

Hybrid structures targeted at high-performance electrochemical applications circumvent great challenges. Nanostructures with high porosity facilitating electrolyte penetration and providing fast ion and electron transfer are suitable candidates for constructing hybrid structured electrode materials. Here in, an architecture composed of nanowires and urchin-like structures of NiCo2O4 covered by NiCoSe2 nanosheets is successfully constructed on Ni foam through hydrothermal treatment in association with electrodeposition. The fabricated NiCo2O4/NiCoSe2 hybrid electrode demonstrates areal capacitance of 12.09 F cm-2 at current density of 5 mA cm-2, surpassing that of pristine NiCo2O4. Furthermore, the electrode evidences cycling stability with 87.6% capacitance retention over 3000 cycles. An asymmetric hybrid supercapacitor, assembled by the NiCo2O4/NiCoSe2 as a positive electrode and activated carbon as a negative electrode, represents areal capacitance of 3.07 F cm-2 at 5 mA cm-2. The as-fabricated device with excellent cycling stability (90.9% capacitance retention over 2000 cycles) delivers an energy density of 66.13 Wh kg-1 at a power density of 233 W kg-1. Our results convey a promising synthesis method of the core-shell structure of NiCo2O4/NiCoSe2 nanowire arrays for application in supercapacitors.