Natural fiber welded electrode yarns for knittable textile supercapacitors

Abstract

Natural fiber welded (NFW) yarns embedded with porous carbon materials are described for applications as electrodes in textile electrochemical capacitors. With this fabrication technique, many kinds of carbons can be embedded into cellulose based yarns and subsequently knitted into full fabrics on industrial knitting machines. Yarns welded with carbon and stainless steel have device capacitances as high as 37 mF cm-1, one of the highest reported values for carbon-based yarns. The versatility of this technique to weld any commercially available cellulose yarn with any micro- or nanocarbon means properties can be tuned for specific applications. Most importantly, it is found that despite having full flexibility, increased strength, and good electrochemical performance, not all of the electrode yarns are suitable for knitting. Therefore, it is recommended that all works reporting on fiber/yarn capacitors for wearables attempt processing into full fabrics. Wearable electronics are quickly evolving, finding use in the clothing industry, but they still need an integrated textile power source. Steps towards making capacitive yarns for knitted electrochemical capacitors using a technique called natural fiber welding are described. Carbon materials are embedded into cotton, linen, bamboo, and viscose yarns and are electrochemically characterized.