All‐Solid‐State Flexible Fiber‐Based MXene Supercapacitors

Abstract Flexible fiber‐shaped supercapacitors are promising energy‐storage devices in wearable smart electronics. Exploring the knittable fiber‐type electrode with high capacitance would promote the wide‐scale application of such capacitors. Herein, a solution‐processed methodology to fabricate all‐solid‐state, flexible, and fiber‐based supercapacitors employing Ti 3 C 2 T x MXene is proposed. Commercially available silver‐plated nylon fibers are chosen as fibrous structural support for the first time. Through mildly baking the surfactant‐free Ti 3 C 2 T x flakes suspension loaded on the silver‐plated nylon fibers, a uniform and adhesive film consisting of Ti 3 C 2 T x nanometer‐thick flakes is well established in a parallel manner on the highly conductive fibrous support. It is emphasized that the chemically cross‐linked polyvinyl alcohol–H 2 SO 4 hydrogel is served as a solid‐state electrolyte that guarantees the structural integrity and mechanical strength of the assembled capacitor. The fabricated capacitor exhibits a high areal capacitance of 328 mF cm −2 with excellent cyclability and flexibility, capacitance retention remaining at least above 80% under various deformation modes including bending, twisting, and knotting. The device based on the all‐solid‐state, fiber‐type capacitors can drive a light‐emitting diode. This work proposes a feasible strategy, offering a platform for rational designs of flexible electronics employing a large family of MXenes and their heterostructures as well.