Microstructural Design of 3D Intertwined Biomimetic Composite Fibers for Functional Smart Textiles in Energy Storage

Supercapacitors, renowned for their long lifespan, high power density, and rapid charge/discharge capabilities, are essential for next-generation energy storage systems. Fiber-based fabric supercapacitors present a promising solution for wearable and portable applications due to their flexibility and integrability. However, the introduction of fillers or bridging agents in fiber electrodes, along with their inherently limited dimensions, often compromises electrical conductivity and specific surface area, resulting in reduced energy density. Inspired by the hierarchical structure of the lotus stem, a biomimetic fiber electrode featuring 1) a PEDOT:PSS protective outer cortex, 2) MXene-based conductive phloem fibers, and 3) an interconnected CNT network mimicking the xylem's 3D transport architecture is fabricated. This biomimetic microstructure design significantly enhances fiber conductivity (2741.7 S cm^-1) and specific surface area, while improving electrode surface electrochemical activity. The optimized fiber electrode achieves outstanding performance: a volumetric specific capacitance of 417.8 F cm^{- 3}, an energy density of 15.3 mWh cm^{- 3}, and 89.8% capacitance retention after 10 000 cycles. The fabricated fiber-based fabric supercapacitor exhibits a wide operating potential window of 3.2 V, demonstrating practical viability by powering an LED for 15 min and sustaining a spreadsheet display for over 45 min. This study proposes a bioinspired strategy for controlling the 3D intertwined fiber structure, significantly enhancing electrode energy density and extending supercapacitor operation time. This approach addresses the critical challenge of low energy density in smart textiles, advancing the development of practical wearable electronics.