Fabrication Of Supercapacitor From Exfoliated Graphene Oxide

Abstract

Supercapacitors are charge storage devices with ultrahigh capacitance and power density. Supercapacitors can be of different types depending on the charge storage mechanism. A pseudocapacitive supercapacitor is fabricated which stores charge electrochemically via redox charge transfers at electrodes. Only adsorption and desorption of ions at electrodes take place. The pseudocapacitor is made from graphene oxide (GO) and exfoliated graphite composite material. This composite material is produced via liquid phase exfoliation of graphite in IPA. Exfoliation process is carried out by sonicating graphite powder for different durations, i.e. 24 h, 48 h and 72 h at 60 oC. The sonicated suspensions are then centrifuged which separates the suspensions into two parts i.e. top 70% clear part which has suspended graphene flakes and bottom 30% residual material part. The top 70% part of 72 h sonicated suspension has graphene flakes which are about 30 layers thick. Supercapacitor is made using the residual composite material which has some amount of graphene oxide which increases the surface area of graphite. Exfoliated graphite also increases the surface area of the material. Graphite oxide and isolated graphite flakes are also formed in the composite material. The conductivity of composite material has also improved when compared to graphite. The best results are shown by the composite material made via sonication for 48 h. A specific capacitance of 534.53 F/g and energy density 25.68 J/g is observed. Increased surface area and conductivity of the material as well as the availability of oxygen functional groups result in strong pseudocapacitive behavior and high value of specific capacitance.