Polyaniline—Graphene Electrodes Prepared by Electropolymerization for High-Performance Capacitive Electrodes: A Brief Review

Both polyaniline (PANI) and graphene are widely studied for their application as capacitive electrodes in energy storage devices. However, although PANI can be easy synthesized, is of low cost and has a higher specific capacitance than graphene, pristine PANI electrodes do not present long-term stability due to their large volume changes during release/doping of the electrolyte ions and surface area reduction with charge-discharge cycling. That is why a combination of PANI with carbonaceous materials, especially conductive and high-surface-area graphene as well as more widely used reduced graphene oxide (rGO), provides an effective approach to solve these problems. At the same time, the electropolymerization process is one of the possible methods for synthesis of PANI composites with G or rGO as freestanding electrodes. Therefore, no binders or additives such as carbon black or active carbon need to be used to obtain PANI/rGO electrodes by electrochemical polymerization (EP), in contrast to similar electrodes prepared by the chemical oxidative polymerization method. Thus, in this paper, we review recent advances in EP synthesis of PANI/rGO nanocomposites as high-performance capacitive electrode materials, combining the advantages of both electrical double-layer capacitance of rGO and pseudocapacitance of PANI, which hence exhibit long cycle life and high specific energy.