Highly processible and electrochemically active graphene-doped polyacrylic acid/polyaniline allowing the preparation of defect-free thin films for solid-state supercapacitors

Abstract

In the present work, we report the preparation of graphene (G) doped polyacrylic acid/polyaniline (G-PAA/PANI) composites with excellent processibility for ensuring ultrathin, defect-free and highly flexible films, as well as high electrochemical performance. The weight content of PANI is maximized under the constraint of still allowing defect-free films, and the G content is optimized. Interestingly, we combine two steps that both, if taken in isolation as a strategy, worsen the solubility. The PANI and G contents are optimized to be 20 wt% and 1.3 wt%, respectively. The optimal G-PAA/PANI composite film has a gravimetric capacitance of 399 F g⁻¹ at 10 mV s⁻¹, which is more than twice that of pure PANI nanoparticles. Considering the film thickness of only 50 μm, its specific areal and volumetric capacitances are as high as 1.20 F cm⁻² and 240 F cm⁻³. The film still has a gravimetric capacitance of 342 F g⁻¹ at a high scan rate of 100 mV s⁻¹ (86% of that at 10 mV s⁻¹), which promises great potential for applications needing a rapid charge/discharge. An assembled all-solid-state supercapacitor using two such flexible G-PAA/PANI films provides 93 F g⁻¹; an eighteen-fold improvement over that of a previously reported similar device. The capacitor also exhibits excellent electrochemical stability under different bending angles.