A highly electronic conductive cobalt nickel sulphide dendrite/quasi-spherical nanocomposite for a supercapacitor electrode with ultrahigh areal specific capacitance

Abstract

In this study, a spinel binary transition metal sulphide Co1.5Ni1.5S4 dendrite/quasi-spherical nanocomposite with high electronic conductivity and a suitable porous structure was synthesized via a facile hydrothermal process. The morphology and structure of the Co1.5Ni1.5S4 nanocomposite were easily manipulated by tuning the hydrothermal reaction time. To the best of our knowledge, due to its good electronic conductivity and suitable structure for the electrochemical redox reaction, the Co1.5Ni1.5S4 electrode exhibited the highest areal specific capacitance of 41.0 F cm−2. The electrochemical impedance spectroscopy (EIS) results demonstrate that Co1.5Ni1.5S4 possesses a higher electronic conductivity and faster charge transfer than single-component sulphides (CoS and NiS) or cobalt-nickel hydroxides and oxides. These characteristics contribute to the high specific capacitance of the Co1.5Ni1.5S4 electrode even at high material loading, corresponding to an ultrahigh areal specific capacitance. An asymmetric supercapacitor, which was assembled with Co1.5Ni1.5S4 as the positive electrode active material and HNO3-treated activated carbon as the negative electrode active material, exhibited a superior energy density of 32.4 Wh kg−1 at a power density of 103.4 W kg−1 and 25.0 Wh kg−1 at a high power density of 5.5 kW kg−1.