Eco-friendly and sustainable supercapacitor design: Cobalt sulfide nanoparticles embedded on carbon cloth as an electrode material for asymmetric devices

Cobalt sulfide (CoS) nanoparticles were synthesized via hydrothermal reaction route and evaluated for their electrochemical performances on carbon cloth substrate. The crystalline structure, morphology and chemical state of the prepared CoS nanoparticles are examined by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Structural characterization confirmed the formation of a hexagonal phase of CoS structure with a space group of P63/mmc. Electrochemical analysis revealed pseudocapacitive behavior, as evidenced by redox peaks observed in cyclic voltammetry (CV) curves. The CoS electrode achieved a maximum specific capacitance value ~ 382.3 F.g⁻¹ at scan rate of 5 mV.s⁻¹ and ~ 285.8 Fg⁻¹ at a current density of 2 Ag⁻¹. The electrode demonstrated excellent cycling stability retaining ~ 97% of its initial specific capacitance with coulombic efficiency ~ 96% after 5000 charge–discharge cycles. An asymmetric supercapacitor CoS//AC device was fabricated in a coin cell configuration and under 2 M KOH, the device delivered a specific capacity of ~ 560 mAh.g⁻¹ at 10 mV.s⁻¹ and ~ 430 mAh.g⁻¹ at 0.1 A.g⁻¹. The device attained maximum energy density of ~ 258 Wh.kg⁻¹ at 0.1 A.g⁻¹ and maximum power density of ~ 14.8 kW.kg⁻¹ at 1.2 A.g⁻¹, with capacity retention of ~ 86% after 2000 cycles. The results demonstrate a sustainable and eco-friendly approach to designing cobalt sulfide-based asymmetric devices for energy storage applications.