Realizing ultrahigh areal capacitance and cycle stability of polyaniline nanofiber network grown on graphene–modified carbon cloth with the addition of trivalent iron ions in electrolyte

Abstract

One kind of polyaniline (PANi)–based flexible electrodes for all–solid–state supercapacitor with ultrahigh areal capacitance and cycle stability is fabricated through electrochemical polymerization. The oriented growth of PANi nanofibers is efficiently promoted when graphene shell is firstly coated on carbon fiber. Then ferric sulfate is introduced into the electrolytes for further enhancing the pseudocapacitance contribution, and the best charge storage ability of the composite electrode is achieved at 15 mol. % Fe3+ ion content. The assembled supercapacitor possesses a maximum areal capacitance of 1.90 F cm−2 at the current density of 5 mA cm−2. At 30 mA cm−2, the device retained 74.7% of the maximum capacitance. It showed a maximum energy density of 264 μWh cm−2 at a power density of 2.5 mW cm−2 and a capacitance retention of up to 93.1% after 3000 cycles at 10 mA cm−2. These results can be attributed to high efficient pathway for ion diffusion and electron transport constructed between PANi nanofiber array and graphene shell on the CC, as well as the redox reaction in electrolyte and metal ion–doping effects of PANi caused by trivalent iron ions. Such device with the desirable characteristics has a promising application prospect in wearable power supply system.