Macroscopic MXene ribbon with oriented sheet stacking for high-performance flexible supercapacitors

Abstract

Flexible and wearable fiber electrodes with high conductivity and acceptable electrochemical behavior are crucial for extending the application of next-generation portable electronics, the development of which, however, is very challenging. Two-dimensional sheets are known to be excellent units for assembling fiber entities, particularly when sheets are oriented in a stacking manner, which helps integrate their intrinsic in-plane advantages, especially those related with mechanical and electronic performances. In this study, we developed a flexible macroscopic and continuous fiber in an unusual ribbon shape composed solely of Ti3C2 sheets, a typical member of the MXene family. The ribbon morphology was realized through highly ordered stacking of Ti3C2, which imparts fibers with favorable mechanical characteristics. Based on the intrinsic metallic conductivity of Ti3C2 sheets and the oriented stacking structure, the developed macroscopic ribbon exhibited excellent conductivity for both electrons (up to 2458 S/cm) and ions. A fiber-shaped asymmetric supercapacitor using the developed macroscopic ribbon as a cathode coupled with reduced graphene oxide fibers as an anode delivered a competitive maximum volumetric energy density of 58.4 mWh/cm3 (20.0 Wh/kg) while maintaining a power level of 1679.0 mW/cm3 (581.0 W/kg) and excellent cycling stability (92.4% retention after 10 000 cycles at 10 A/g). This study highlights the excellent potential of MXene as a platform for macroscopic assembly and definitely broadens the applications of MXene materials in wearable electronics.