Polyaniline‐Modified Hierarchical Graphene Fiber for Ultrahigh‐Performance Electrochemical Supercapacitor with Carbon Fiber in Core as Current Collector

As the demand for portable and wearable energy‐storage devices increases, fiber‐type supercapacitors have rapidly developed. Herein, a two‐step synthesis method is developed to fabricate polyaniline‐modified hierarchical graphene fibers (GFs) with carbon fiber as the core. Using these fibers as the electrode of the supercapacitor, the highly conductive graphene sheets in these fibers can accelerate the transfer of electrolyte ions and fully enhance the Faraday redox transition of polyaniline on the fiber surface, thus realizing the volume capacitance of 2053 F cm −3 . The core–shell hierarchical structures contribute to the high robustness and flexibility of the fibers, which are beneficial to their application in wearable or flexible systems. Moreover, large‐scale production of the core–shell fibers as supercapacitor electrodes without metal wires can be easily realized by a simple bonding technique, which opens up a promising opportunity for practical flexible devices.