Hydrophilicity Improvement of Graphene Fibers for High-Performance Flexible Supercapacitor

Super flexible graphene fibers (GFs) have great potential for yarn supercapacitors (YSCs) used in wearable devices. The performance of YSCs can be improved by increasing both the specific surface area and the hydrophilicity of GFs. Here, we report the continuous fabrication of hydrophilic GF by the wet spinning technique. The hydrothermal treatment of GF in KOH aqueous solution is the crucial step for the hydrophilicity improvement. The synthesized K-GF possesses a porous ruffle structure, excellent hydrophilicity, and good conductivity. The K-GF-based YSC shows good flexibility while folding from 0 to 180° and exhibits a capacitance of 145.6 mF/cm² at an energy density of 3.23 μW h/cm² and power density of 0.017 mW/cm².