A strong and highly flexible aramid nanofibers/PEDOT:PSS film for all-solid-state supercapacitors with superior cycling stability

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is a promising electrode material for flexible supercapacitors mainly because of its pseudocapacitive nature. Nevertheless, its practical applications are still plagued by its poor electrochemical cycling stability due to its low mechanical strength. Herein, we have fabricated a strong, flexible and highly conductive aramid nanofibers/PEDOT:PSS (ANFs/PEDOT:PSS) film by vacuum filtration and subsequent solvent post-treatment. The flexible all-solid-state symmetric supercapacitor from the ANFs/PEDOT:PSS film with an operating potential window of 0-1.6 V exhibits an energy density of 4.54 W h kg^-1 and an excellent capacitance retention of 84.5% after 10 000 cycles at room temperature. Excitingly, the flexible device still displays an energy density of 3.83 W h kg^-1 with a capacitance retention of 89.5% after 5000 cycles even at -20 °C. Moreover, the flexible device is found to be electrochemically stable under bending and twisting conditions, even sand striking, which could be ascribed to strong hydrogen bonding interaction between ANFs and PEDOT:PSS. The high electrochemical performances make this electrode a promising candidate for flexible energy storage devices in practical applications even at sub-zero temperatures.