Effect of electrolyte concentration on the capacitive properties of NiO electrode for supercapacitors

The capacitive performances of NiO as electrode-active material in aqueous KOH electrolyte with different concentrations are systematically studied by cyclic voltammetry (CV), galvanostatic charge/discharge technique (GCD), and electrochemical impedance spectroscopy (EIS). CV and GCD data show that NiO delivers higher specific capacitance and better long-term cyclicity in 6 M KOH than in 2 or 4 M solution. EIS spectra reveal both charge transfer resistance (R (ct)) and solution resistance (R (s)) reduce with the increase of the KOH concentration, indicating the smoother charge and ion transfer pathways in both electrode and bulk electrolyte solution in the denser electrolyte.