Scalable preparation of high performance fibrous electrodes with bio-inspired compact core-fluffy sheath structure for wearable supercapacitors

Thanks to their light-weight, wearing comfort, and amenability to be woven into textiles, solid-state fiber supercapacitors (FSCs) have been considered as promising energy storage devices for wearable electronics. Carbon fibers (CFs) have the merits of both superior mechanical strength and conductivity, excellent flexibility, doped by heteroatoms, good knittability/weavability, and most importantly have already been produced in ton-scale in form of continuous tows; however, their applications in FSCs are limited to current collectors or conductive scaffolds as a result of the inert surface composed of highly compacted and well-aligned graphitic sheath. Inspired by Cattail's unique compact core-fluffy sheath structure, herein, we develop an electrochemical method to directly transform CFs into high performance electrode by controllably swelling the well-aligned graphitic sheath without disturbing the core fiber of interlinked randomly-orientated carbon nanocrystals. Compared to pristine CFs, the obtained fiber electrode delivers more than two-order improved capacitance (87.2 F cm⁻³ at 1.0 A cm⁻³) with excellent rate capability and cycling stability, enabling the as-fabricated solid-state supercapacitor much enhanced energy density. The scalability of our method is demonstrated, which is believed to be compatible with the state-of-art commercial processing techniques, thus holds great promise for future development of electronic-textiles.