Supercapacitive properties of symmetry and the asymmetry two electrode coin type supercapacitor cells made from MWCNTS/Nickel oxide nanocomposite

Supercapacitive properties of synthesised nickel oxides (NiO) nanoparticles integrated with multi-walled carbon nanotubes (MWCNT) in a two-electrode coin cell type supercapacitor were investigated. Successful formation of the MWCNT-NiO nanocomposite was confirmed with techniques such as transmission electron microscopy (TEM), scan electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The supercapacitance behaviour of both the symmetry and the asymmetry MWCNT-NiO based supercapacitor in 1 M H₂SO₄ and 1 M Na₂SO₄ electrolytes was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic constant current charge-discharge (CD) techniques. There was a good correlation between the CV and the CD specific capacitance (SC) values for the asymmetry supercapacitor. Asymmetry supercapacitor (MWCNT-NiO|H₂SO₄|MWCNT) gave the highest SC value of 925.9 mFcm^-2 (53.9 F g^-1). High SC values which are higher than most of those reported in literature were obtained. The electrodes demonstrated high stabilities with no significant changes in SC values over 1000 cycles.