Comparison of Graphene Materials for Supercapacitor Electrodes

Abstract

Research into graphene supercapacitors is currently undergoing a large increase in growth due to its beneficial chemical and mechanical properties. However, reports on ‘graphene’ supercapacitors use graphene materials produced through various methods. Currently, there has been no investigation into the effect the production method has upon the capacitance of the system, meaning direct comparison of the literature is not possible. In this work we compared several ‘types’ of graphene. These include “pure” graphene samples which include liquid phase exfoliated graphene, graphene nanoribbons, anodically exfoliated electrochemically graphene in aqueous system and cathodically exfoliated electrochemically exfoliated graphene in an organic system. Also included were “modified” graphene samples which included graphene oxide and reduced graphene oxide. It was observed that graphene oxide exhibited the highest specific capacitance of 164 F/g (5-10 times higher) , measured at a current density of 0.5 A/g, due to the oxygen containing functional groups giving an additional pseudocapacitance response as well as preventing restacking of the material. The graphene oxide also showed similar or superior cyclability when compared to the other pure and modified graphene materials. However, due to its intrinsically high resistance the addition of a conductive additive is required to achieve high rate capability. The higher capacitance and less energy demanding processing indicate that graphene oxide may be a better choice for high energy supercapacitor applications than “pure” graphene which will be suitable for high power applications.