Coelectrodeposition of NiSe/ZnSe Hybrid Nanostructures as a Battery-Type Electrode for an Asymmetric Supercapacitor

A NiSe/ZnSe (NZSe) hybrid nanostructure was fabricated via the coelectrodeposition method on nickel foam substrate as a binder-free electrode for asymmetric supercapacitors. The Ni/Zn ratio has a great impact on the morphologies and electrochemical properties of NZSe composites. Under an optimal Ni/Zn ratio, the resultant NZSe hybrid electrode exhibits excellent electrochemical performance with a high specific capacity of 651.5 mAh g–1 at 1 A g–1, which is noteworthy higher than that of pure NiSe (267.5 mAh g–1) and ZnSe (211.1 mAh g–1) at the same current density. Moreover, the NZSe electrode exhibits a satisfying cyclic stability of 2000 cycles (97.6% retention of its initial capacity value). The noticeable performance improvement is attributable to the synergetic effect of NiSe and ZnSe, and the unique hierarchical nanostructure of NZSe also plays an essential role in providing high conductivity, rich redox reactions, short ion diffusion, and efficient charge transport. An asymmetric supercapacitor assembled by utilizing the NZSe hybrid electrode as a positive electrode and active carbon (AC) electrode as the negative electrode delivers a high specific energy of 44.4 Wh kg–1 and superior cycling stability (98.7% capacitance retention after 10 000 cycles).