Biomimetic Interfacial Manipulation in Ti ₃ C ₂ T _x Fibers Toward Strengthened Interlayer Cross‐linking, Regulated Ion Diffusion and Suppressed Self‐Discharge

Abstract Simultaneous improvements in mechanical and electrochemical properties of MXene (Ti ₃ C ₂ T _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 Ti ₃ C ₂ T _x fibers. 3‐aminopropyltriethoxysilane (APTES) is employed as a reinforcer and spacer that is anchored on Ti ₃ C ₂ T _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 .