Controlled Growth of CoSx Nanostrip Arrays (CoSx-NSA) on Nickel Foam for Asymmetric Supercapacitors

A high-energy-density asymmetric supercapacitor based on cobalt sulfide nanostrip arrays (CoSx-NSA) as the cathode and reduced graphene oxide as the anode has been prepared; the CoSx-NSA was synthesized on three-dimensional (3D) nickel (Ni) foam by using a simple and scalable chemical bath deposition (CBD) method. The reduced graphene oxide sheets were deposited on the Ni foam by hydrothermal treatment of the foam in a graphene oxide solution. Novel and unique nanostructured architectures of the CoSx electrode provide a large effective surface area. In addition, both of the electrode materials are directly grown on the substrate without any conductive additives or binders, avoiding unnecessary materials. The asymmetric supercapacitor device operates in a wider potential window, achieving a remarkably high energy density, excellent rate capability, and long-term cycling stability. These attractive results make CoSx-NSA a promising material for asymmetric supercapacitors of high energy and power density, utilizing an aqueous electrolyte solution.