Bio-Inspired Interfacial Engineering of MXene Fibers Toward Synergistic Improvement in Mechanical Strength and Electrochemical Performance

High-performance fibrous materials urgently desired for fabricating energy storage devices to power wearable textile electronics are expected excellent mechanical properties, improved output capacitance, and rapid charge/discharge capability; nevertheless, their contradictory requirements in material design impose immense challenges. Inspired by the robust structure of higher plants that evolve over millions of years, herein, an interfacial engineering strategy is proposed for synergizing the mechanical strength and electrochemical performance of Ti₃C₂T_X MXene fibers by selecting aramid (Kevlar) nanofibers and borate ions (B) as the enhancers. The intercalation of Kevlar nanofibers endows the nascent wet-spun MXene gel fibers with a high stretchable ratio through physical interaction (hydrogen bonds), greatly aligning the orientation of MXene nanosheets. B-cross-links introduce covalent bonds between MXene nanosheets, which together with hydrogen bonds significantly enhance fiber strength. More importantly, optimal ion transport kinetics is achieved by synergizing the inverse impacts of Kevlar nanofibers and B-cross-link on interlayer spacing, guaranteeing excellent electrochemical performances. Benefiting from their excellent mechanical, electrical, and electrochemical performances, borate (B)-cross-linked MXene/Kevlar fibers (MKB) are simultaneously adopted as fibrous electrodes and receiving antennae for asymmetric supercapacitors with wireless charging functions. The proposed strategy provides an avenue for designing high-performance functional fibers for future wearable applications.