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

- A simple low temperature solution method was used for preparing NC-EEG.
- Graphene sheets were obtained by electrochemically exfoliation process.
- A high capacity of NC-EEG in a three-electrode system, as high as 649 C g−1, was recorded.
- Asymmetric supercapacitor based on NC-EEG exhibited excellent energy density and power density.

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 6 M KOH electrolyte. The NC-EEG nanocomposites exhibited a high capacity value of 649 C g−1 at a current density of 1.0 A g−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 86 Wh kg−1 and a maximum power density of 16.5 kW kg−1. It is believed that our 3D nano-architectured composites with excellent electrochemical performances would be promising candidates for supercapacitor materials.

The paper reported the Ni-Co oxide/electrochemically exfoliated graphene nanocomposites with 3D porous nano-architectures (NC-EEG) using a simple low temperature solution method combined with a thermal annealing treatment. 3D porous architectures provide large surface areas and shorten electron diffusion pathways for high performance asymmetric supercapacitors.125