High performance supercapacitor electrodes from electrospun nickel oxide nanowires

Electrochemical energy storage using pseudocapacitive mode is under intense research owing to their potential in fabricating high performance renewable energy devices at a lower cost. In this paper we characterize nickel oxide (NiO) nanowires developed by electrospinning an aqueous polymeric solution containing nickel precursor for its application as a pseudocapacitors electrode. The wires are of diameter ∼50-70 nm containing densely packed cuboidal grains (∼10-20 nm) with less degree of crystal defects. Electrochemical properties of the electrodes fabricated on a nickel foam substrates are evaluated by cyclic voltammetry (CV) and charge-discharge cycling (CDC), and electrochemical impedance spectroscopy (EIS) techniques. The best performing electrode showed a specific capacitance (CS) of ∼670 Fg−1 with high cycling stability (∼100%) for over 1000 cycles and Coulombic efficiency ∼98%. Lower electrochemical equivalent resistance (∼0.76 Ω), charge transfer resistance (∼0.45 Ω), and charge relaxation time (43 ms) are observed which are attributed to the defect free nanowire morphology that give rise to the superior performance.