Synergetic and anomalous effect of CNTs in the sulphide-based binary composite for an extraordinary and asymmetric supercapacitor device

Abstract

Carbon nanotubes (CNTs) have attained great interest from researchers due to their excellent electrical conductivity, vast surface area, and good chemical stability. In this work, the sulphide-based composite Ag2S@ZnS was synthesized using the hydrothermal method and was doped with CNTs in various weight percentage ratios. The structural and morphological characteristics of the samples were evaluated by employing X-ray diffractometry (XRD), X-ray photo spectroscopy (XPS), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, and thermogravimetric analysis (TGA), while cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) were also executed for their electrochemical characterization. The performance of the Ag2S@ZnS electrode was enhanced after the doping of CNTs because of their synergistic effect. An extraordinary specific capacity (Qs) of 946.5 Cg−1 (262.91 mAh g−1) was exhibited by Ag2S@ZnS with 50% CNTs doping (Ag2S@ZnS/CNT-50%), which is significantly greater than the reference samples. Furthermore, an asymmetric supercapacitor was designed and assessed for its electrochemical properties. The specific capacity of the asymmetric supercapacitor reached 148.62 Cg−1 (41.28 mAh g−1). The device showed improved stability and retained the 87% initial capacity after 5000 cycles. The energy and power densities were found to be 33.02 Wh kg−1 at 639.98 W kg−1, respectively, with a high value of coulombic efficiency of 92%. The device succeeded in acquiring a higher power density of 3200 W kg−1 for an energy density of 4 Wh kg−1. These astonishing results provide opportunities to design high-performance electrode materials for extraordinary energy storage devices.