Free-standing NiCoSe₂ nanostructure on Ni foam via electrodeposition as high-performance asymmetric supercapacitor...

Designing a high-energy-density and power-density electrode for supercapacitors has become an increasingly important concept in the energy storage community. In this article, NiCoSe₂ nanostructures were electrodeposited on nickel (Ni) foam and directly used as electrodes for supercapacitors. The effect on the morphology and electrochemical performance of NiCoSe₂ prepared under different scan rates was measured through scanning electron microscopy and various electrochemical measurements. The resultant NiCoSe₂ prepared with 5 mV s^-1 exhibits a cross-linked porous nanostructure and a high specific capacitance of 2185 F g^-1 at a current density of 1 A g^-1. Taking advantage of these features, an ASC is constructed by using NiCoSe₂ on Ni foam as the positive electrode and an active carbon electrode as the negative electrode with 3 M KOH as the electrolyte. The ASC displays a high-energy density of 41.8 Wh kg^-1, an ultrahigh power output of 8 kW kg^-1, as well as a long cycling life (91.4% capacity retention after 10 000 cycles). The excellent electrochemical performance makes the porous NiCoSe₂ nanostructures a promising alternative in energy storage devices.