Asymmetric Supercapacitors based on Hybrid CuO@Reduced Graphene Oxide@Sponge versus Reduced Graphene Oxide@Sponge Electrodes

An asymmetric supercapacitor was fabricated by using CuO@reduced graphene oxide@sponge (CuO@rGO@SP) composites as the positive electrode and rGO@SP as the negative electrode in Na2SO4 aqueous electrolyte. Macroporous and low-costing sponges were explored as skeletons to construct a homogeneous 3D interconnected network of rGO. Initially, rGO was deposited on the sponge by the dip-and-dry method. Subsequently, a CuO nanosheet cluster was deposited by using the chemical bath deposition method on the rGO-coated sponge substrate. The CuO@rGO@SP electrodes could be operated even under a high scan rate of 200mVs(-1) and exhibited a maximum specific capacitance of 519Fg(-1). An asymmetric supercapacitor device based on CuO@rGO@SP//rGO@SP could be cycled in the high voltage range of 1.7V and displayed high specific capacitance of 77.84Fg(-1) and a high energy density of 31.24Wh(-1)kg(-1). Impressively, this asymmetric device exhibited an excellent long cycle life and 83% of the specific capacitance was retained after 2000cycles.