(Invited) Multifunctional Mxene-Based Fibres

Abstract

Yarn-shaped supercapacitors (YSCs) once integrated into fabrics provide promising energy storage solutions to the increasing demand of wearable and portable electronics. In such device format, however, it is a challenge to achieve outstanding electrochemical performance without compromising flexibility. Metal carbides or carbonitrides called “MXene” has presented a distinct combination of very high conductivity (~10,000 S cm-1), volumetric capacitance (~1,500 F cm-3), and hydrophilic properties. To date, however, MXene-based fibers or yarns that can be used for wearable applications have been relatively unexplored. Their small sheet size (<2 µm) and weak inter-sheet interactions have made it challenging to fabricate MXene-based fibers or yarns. Here, we present strategies to achieve fibers or yarns from Ti3C2 MXene. Our works include high-performance yarn supercapacitors fabricated by coating MXene on conductive carbon fiber bundles. This device showed length capacitance of ~132 mF cm-1 higher than the literature reports (typically lower than 100 mF cm-1) even at low mass loading of 2 mg cm-1. We also used wet-spinning technique by taking advantage of the templating role of liquid crystalline (LC) graphene oxide (GO) to produce fibres with high MXene content of ~88 wt. %. These fibres demonstrate excellent flexibility and a high volumetric capacitance of ~341 F cm-3. We also employed biscrolling technique to scroll MXene nanosheets within carbon nanotube helical corridors. Here, the yarns are predominantly MXene containing up to ~98 wt.% MXene yielding an areal capacitance as high as ~3,188 mF cm−2, which exceeds the previously recorded performance for any fiber or yarn supercapacitor electrode. The supercapacitor prototype in asymmetric configuration reached a maximum energy and power densities of ~61.6 mWh cm–3 and ~5428 mW cm–3 respectively. We show that the MXene-based fibers and yarns are useful for powering small electronic devices when knitted or woven into a textile. Our works have introduced a new class of fibers that can be excellent candidates for integration within textile-based electronics and wearable devices.