Electrochemical performance of 3D porous Ni-Co oxide with electrochemically exfoliated graphene for asymmetric supercapacitor applications

Abstract

Ni-Co oxide, one of the binary metal oxides, has many advantages for use in high-performance supercapacitor electrode materials due to its relatively high electronic conductivity and improved electrochemical performance. In this work, Ni-Co oxide/electrochemically exfoliated graphene nanocomposites (NC-EEG) are successfully synthesized using a simple low temperature solution method combined with a thermal annealing treatment. Graphene sheets are directly obtained by an electrochemical exfoliation process with graphite foil, which is very simple, environmentally friendly, and has a relatively short reaction time. This electrochemically exfoliated graphene (EEG) can improve the electrical conductivity of the Ni-Co oxide nanostructures. The as-prepared NC-EEG nanocomposites have 3D porous architectures that can provide large surface areas and shorten electron diffusion pathways. Electrochemical properties were performed by cyclic voltammetry and galvanostatic charge/discharge in a 6M KOH electrolyte. The NC-EEG nanocomposites exhibited a high capacity value of 649Cg−1 at a current density of 1.0Ag−1. The asymmetric supercapacitors, manufactured on the basis of NC-EEG nanocomposites as a positive electrode and activated carbon (AC) as a negative electrode, exhibited a maximum energy density of 86Whkg−1 and a maximum power density of 16.5kWkg−1. It is believed that our 3D nano-architectured composites with excellent electrochemical performances would be promising candidates for supercapacitor materials.