Nacre-Inspired Flexible Mxene-Based Films for Multifunctional Applications in Supercapacitors and Piezoresistive Sensors

The explosive demand for flexible wearable and portable devices imposes stringent requirements on the mechanical, energy storage, and sensing properties of functional materials. Although two-dimensional (2D) transition metal carbides and nitrides (MXene) possess high conductivity and pseudocapacitance, their severe self-restacking and intrinsic brittleness restrict their practical applications. Herein, a facile vacuum filtration and hot-pressing densification strategy is proposed to fabricate nacre-inspired MXene-based films. By incorporating one-dimensional (1D) high-aspect-ratio TEMPO-oxidized cellulose nanofibrils (TOCNFs), the self-restacking of MXene is effectively suppressed. The optimal M20F5 composite film exhibits a coordinated electromechanical balance, maintaining an electrical conductivity of 1.07 × 106 S m−1 while enduring 2124 folding cycles. For energy storage, the assembled symmetric supercapacitor delivers a specific capacitance of 828.92 F g−1 at 0.5 mA cm−2 and maintains an energy density of 13.75 Wh kg−1 at a power density of 9500 W kg−1. Furthermore, acting as a piezoresistive sensor, the film achieves reliable detection, spanning from bimodal gait recognition to subtle physiological pulses. This work establishes a viable material design strategy for next-generation supercapacitors and intelligent wearable systems.