Impact of Preprocessing of Graphene Additive via Ultrasonication on the Electrochemical Performance of Activated Carbon‐Based Supercapacitors

This article investigates the influence of the addition method of graphene to activated carbon (AC) on the electrochemical performance of the fabricated electric double‐layer capacitors (EDLCs). To do so, the same graphene material is introduced to the other electrode slurry materials either in the form of a powder (GP) or a suspension (GL). It is discovered that the introduction of graphene already dispersed by ultrasonic in a suspension to AC has a better effect on the electrochemical performance of the fabricated EDLCs than directly employing its powder. GL EDLC achieves the highest capacitance of 54 F g−1 at a current density of 0.05 A g−1 in an organic electrolyte, which is much better than the GP EDLC (41.9 F g−1) and about 77% more than AC EDLC. Moreover, after cycling at various current densities (2000 cycles), GL EDLC maintains 28.8 F g−1 of its capacitance with 99.4% coulombic efficiency at a current density of 1 A g−1. Finally, GL EDLC exhibits 35.8 and 21.4 Wh kg−1 energy densities at 50.2 and 1102.8 W kg−1 power densities, respectively. The better performance of GL EDLC in comparison with GP EDLC is ascribed to better graphene dispersion. The content of our discussion in this article is that graphene plates tend to stack together and agglomerate. It is better not to use graphene in powder form or not to remove the solvent after the synthesis completely. The use of dispersed graphene affects the performance of the supercapacitor.