A strategy to prepare activated carbon fiber membranes for flexible solid-state supercapacitor applications

The development of flexible supercapacitors is highly desired for electrode materials with good flexibility and a high specific surface area. The electrospun carbon fiber membranes (CFMs) have the possibility of being used as flexible electrodes due to their one-dimensional fiber structure. The pristine CFMs generally have poor porosity, and the activation process is of the essence. However, the conventional blending activation process will produce an uneven pore distribution and destroy the fiber membrane structure, which is not conducive to maintaining the flexibility of CFMs and hindering the application in flexible supercapacitors. Herein, by treating the electrospun CFMs with KOH impregnation activation process, we have succeeded in making the activation of CFMs more uniform and avoiding the occurrence of local over-activation. On the premise of ensuring that the fiber structure of CFMs is not damaged, the specific surface area of activated CFMs (ACFMs) was increased to 2408 m2 g−1, and the mechanical flexibility of CFMs was well maintained. As a result, the optimal ACFMs delivers a specific capacitance of 289.2 F g−1 at a current density of 0.5 A g−1 in aqueous electrolyte and an energy density of 14.8 Wh kg−1 in neutral electrolyte. In addition, the flexible solid-state symmetric supercapacitor also shows excellent electrochemical performance, making it have great potential in energy storage applications for wearable, foldable, and portable electronic devices.