Flexible hybrid yarn-shaped supercapacitors based on porous nickel cobalt sulfide nanosheet array layers on gold metalized cotton yarns.

A high-performance yarn-shaped supercapacitor electrode material with light weight, small volume, flexibility and low cost, is highly desirable for the development of flexible energy storage devices. Herein, a cotton/Au/nickel cobalt sulfide hybrid yarn electrode was designed and synthesized by electrodepositing nickel cobalt sulfide nanosheet arrays on the Au metalized cotton yarn. The metalized cotton yarn as a conductive substrate ensures rapid electron transportation. The porous layer which constructed by CoNi2S4 nanosheet arrays significantly enlarges the interface between the electrolyte ions and electrode materials, providing large electroactive surface area for the faradic redox reactions. The hierarchically porous structure of entire yarn electrode shortens the electrolyte diffusion path. A synergistic effect caused by the unique electrode structure greatly increases the electrochemical performance. This hybrid yarn electrode exhibits high specific capacitance of 1323 F/g at 1 A/g, good electrochemical stability and high flexibility with performance well maintained under the mechanical bending condition. An assembled two-ply structured all-solid-state symmetric supercapacitor device delivers an energy density of 40.9 Wh/kg at a power density of 1.43 kW/kg.