In Situ Synthesis of Trifluoroacetic Acid-Doped Polyaniline/Reduced Graphene Oxide Composites for High-Performance All-Solid-State Supercapacitors

Trifluoroacetic acid (TFA) is used for the first time as dopant in the synthesis of the graphene oxide/polyaniline (GO/PANI) composite. The composite was prepared through fast in situ polymerization of aniline (ANI) on GO sheets. After filtration and freeze-drying, the GO/PANI was reacted with hydrazine hydrate to produce reduced graphene/polyaniline (rGO/PANI). In the rGO/PANI, the morphology of PANI can be easily controlled by adjusting the mass ratio of GO to ANI. Oriented PANI was evenly and tightly attached on the rGO backbone to form a hierarchical composite for use as an electrode material in a flexible all-solid-state supercapacitor (ASSSC) with symmetric structure. At the optimal ratio of GO to ANI, the rGO/PANI on carbon cloth attained a high specific capacitance of 810 F g–1 at a current density of 1 A g–1 in a three-electrode system. The energy storage mechanism of the rGO/PANI was found to be mainly controlled by the surface redox reaction process. The rGO/PANI-based symmetric ASSSC displayed considerable capacitance retention of 91.3% after 2000 cycles. Furthermore, the device exhibited a maximum energy density of 62.2 Wh kg–1 at a power density of 0.8 kW kg–1. These favorable properties are primarily attributed to the enhanced interaction between rGO and PANI after the introducing of TFA, which accelerates the electron/ion transfer during charging and discharging by the synergistic effects of double-layer capacitance and pseudocapacitance.