Ideal asymmetric supercapacitors consisting of polyaniline nanofibers and graphene nanosheets with proper complementary potential windows

Polyaniline (PANI) nanofibers are synthesized via a chemical method of rapid mixing for the application of asymmetric supercapacitors. The diameter and aspect ratio of PANI nanofibers is found to be controllable by varying the aniline/oxidant concentration ratio. The ideal capacitive responses of PANI nanofibers between 0.2 and 0.7 V (vs. Ag/AgCl) in concentrated acidic media are demonstrated by cyclic voltammetric (CV) and electrochemical impedance spectroscopic (EIS) analyses coupled with a schematic equivalent-circuit model. The morphologies and textures of nanofibers are examined by scanning electron microscopic (SEM), transmission electron microscopic (TEM) and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopic analyses. An aqueous asymmetric supercapacitor, consisting of a PANI nanofiber cathode and a graphene anode, with proper complementary potential windows is demonstrated in this work, which shows the device energy and power densities of 4.86 Wh kg−1 and 8.75 kW kg−1, respectively.