Biomimetic Interfacial Manipulation in Ti₃C₂T_x Fibers Toward Strengthened Interlayer Cross-linking, Regulated Ion Diffusion and Suppressed Self-Discharge

Simultaneous improvements in mechanical and electrochemical properties of MXene (Ti₃C₂T_x) fibers, especially tensile strength, output capacitance, and self-discharge suppression remain challenging, yet are critical important for promoting the practical applications of fiber supercapacitors (FSCs) as advanced power supplier in future wearable electronics. Inspired by a tree trunk that not only provides enough structure stability against external attacks but also plays a vital role in nutrient transportation through luxuriant micro-conduits, the strategy of interfacial engineering is proposed for designing Ti₃C₂T_x fibers. 3-aminopropyltriethoxysilane (APTES) is employed as a reinforcer and spacer that is anchored on Ti₃C₂T_x surfaces via covalent bonds for modulating stress transfer and increasing accessible active sites, while tannic acid (TA) with abundant phenolic hydroxyl groups is introduced to construct a biomimetic interface for tuning ion diffusion kinetics and further improving tensile strength. The optimized fiber exhibits a high specific capacitance of 1573 F cm⁻³ at 1 A cm⁻³ with 83.8% retained at 15 A cm⁻³ (1318 F cm⁻³), an improved tensile strength of 152 MPa, and more sustainable self-discharge time twice as long as that of bare MXene fiber. The assembled symmetric FSCs deliver a volumetric energy density of 26.8 mWh cm⁻³ at a power density of 418.7 mW cm⁻³.