Highly Reliable Yarn-Type Supercapacitor Using Conductive Silk Yarns with Multilayered Active Materials

Abstract

ABSTRACT The fibrous supercapacitor is a promising candidate for wearable energy-storage systems due to excellent mechanical reliability under deformation. In this study, a mechanically reliable fibrous supercapacitor with high volumetric power density and energy density was developed using fiber electrodes composed of multilayered active materials coated on silk yarns. The conductive silk yarn electrodes are fabricated via a sequential dip-coating process of silver nanowires, multi-walled carbon nanotubes (MWCNT, three to seven walls), and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The composite-coated silk yarn electrodes were stable under cyclic bending as well as under washing in water. Due to the synergetic effect of the three conducting materials, an excellent electrochemical performance was obtained resulting in high volumetric energy and power densities of 8–13 mWh cm−3 and 8–19 W cm−3, respectively. A yarn-type supercapacitor was demonstrated by integrating composite-coated silk yarn electrodes with a hydrogel electrolyte, showing a promising stability as evidenced by the retention of over 94% and 93% of the specific capacitance after 90-degree bending and stretching.