Interface-engineered electrode and electrolyte for the improved energy-storing performance and stable mechanical flexibility of fibrous supercapacitors

Flexible fiber-based electronic textiles are considered to provide a future intelligent platform with a potential to expand the scope of electronic applications in wearable technology. In this respect, energy storge devices consisting of flexible fibers are a feature for the efficient powering and operation of wearable electronic textiles in the bent, knotted, and rolled states. Nevertheless, the application of fibrous supercapacitors consisting of a carbon fiber electrode and gel-electrolyte remains hindered not only by an unreliable mechanical flexibility, but also by low capacitance, poor rate-performance, and low cyclic stability due to the inefficient interface between the electrode and electrolyte. Herein, for the first time, a fibrous supercapacitor with a densely packed gel-electrolyte in the core region is obtained by an aging process that significantly increases the number of electrochemical active sites and enhances the ionic diffusion capability, leading to the improved rate performance. This strategy results in an excellent electrochemical performance, including a high energy density of 1.1 and 0.74 μWh cm⁻² at a power density of 1.3 and 15.0 μW cm⁻², which are superior than the previously-reported fibrous supercapacitors. These results highlight the potential of the fibrous supercapacitor for application in electronic textiles.