Excellent rate capability supercapacitor based on a free-standing PEDOT:PSS film enabled by the hydrothermal method

For the first time, herein, the hydrothermal method with H₂SO₄ as the solvent is introduced to enhance the rate capability of free-standing pristine PEDOT:PSS films. The film with a record conductivity of 3188 S cm^-1 displays a rectangular characteristic at an ultrahigh scan rate of 1300 mV s^-1 and a stable specific capacitance of 110 F cm^-3 from 0.1 to 100 A cm^-3, with a capacitance retention of up to 94.8%. The flexible supercapacitor based on the films delivers a comparable energy density of 2.96 mW h cm^-3 even at a high power density of 36 685 mW cm^-3. This study provides an effective method to prepare PEDOT:PSS films with outstanding electrochemical properties and potentially expand its applications in flexible devices.