Ultrafast flexible PEDOT:PSS supercapacitor with outstanding volumetric capacitance for AC line filtering

Flexible supercapacitors are among the most important power supply devices for fulfilling the energy/power demands of future flexible and wearable electronics. While significant achievements have been made in improving the energy density of the flexible supercapacitors, ultrafast flexible supercapacitors remain in their infancy. Herein, an ultrafast flexible supercapacitor with outstanding capacitance is demonstrated based on the facile, one-step electropolymerization of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). In comparison to the state-of-the-art all-solid-state ultrafast flexible supercapacitors, the as-fabricated flexible PEDOT:PSS-based supercapacitor provides the highest volumetric capacitance of 38 F cm⁻³ in the high-frequency regime (e.g., 120 Hz) while maintaining a sufficient ultrafast response speed for 60-Hz AC line filtering applications. In addition, the electropolymerized PEDOT:PSS flexible supercapacitor provides excellent mechanical flexibility, with bending radii of 4.0–0.6 mm, and durability, with an ∼ 94% capacitance retention after 1,000 bending cycles. The high processability and outstanding electrochemical/mechanical performance are expected to contribute greatly towards the further development of high-performance ultrafast flexible supercapacitors.