Double-layer cobalt selenide/nickel selenide with web-like nanostructures as a high-performance electrode material for supercapacitors

In this study, we report the development of a double-layer CoSe2/NiSe2 film as a high-performance electrode material for supercapacitors. CoSe2/NiSe2 film with a distinctive web-like morphology and large surface area was prepared via two-step sequential electrodeposition of CoSe2 and NiSe2 on a nickel foam. The web-like nanostructure provided interconnected pathways that facilitated charge transport and improved ion-diffusion kinetics near the electrode surface. The favorable morphology and combined redox reactions of CoSe2 and NiSe2 in the double-layer CoSe2/NiSe2 electrode resulted in a synergistically enhanced performance in supercapacitors than those of single-layer CoSe2 and NiSe2, exhibiting a high specific capacity of 646 C g−1 at an operation current of 1 A g−1, outstanding rate capability (68.1% capacity retention at 40-times faster charge/discharge), and decent cycling stability (80.1% capacity retention after 5000 cycles at 40 A g−1). The two-electrode hybrid supercapacitors of CoSe2/NiSe2//activated carbon exhibited maximum energy density (27.8 Wh kg−1) at a power density of 750 W kg−1.