Graphene‐Polymer//Graphene‐Manganese Oxide Nanocomposites‐Based Asymmetric High Energy Supercapacitor with 1.8 V Cell Voltage in Aqueous Solution

Abstract

AbstractAsymmetric supercapacitor is fabricated using reduced graphene oxide‐polymer (RGO‐PEDOT.PSS) and reduced graphene‐manganese oxide (RGO‐CNF‐MnO2) nanocomposites as negative and positive electrodes, respectively. Both the RGO‐PEDOT.PSS and RGO‐CNF‐MnO2 (GCM) nanocomposite electrode were studied systematically with three electrode and asymmetric device configuration. The cyclic voltammetry (CV) and galvanostatic charge‐discharge (CD) studies revealed a maximum specific capacitance of 247 F/g at 1 A/g between −0.9 to 0.1 V (vs. SCE) for RGO‐PEDOT.PSS electrode. While the GCM nanocomposite electrode showed 145 F/g at 1 A/g between −0.1 to 0.9 V (vs. SCE). The X‐ray diffraction (XRD) studies of GCM positive electrode revealed the formation of crystalline Akhtenskite MnO2 hexagonal structure and the XRD of RGO‐PEDOT.PSS confirms the complete reduction of graphene oxide (GO). The microscopic images of GCM demonstrate the MnO2 nanowhiskers growth over the carbon support. The fabricated asymmetric supercapacitor device showed a cell voltage of 1.8 V in 1 M Na2SO4 electrolyte. The CD profile of RGO‐PEDOT.PSS//RGO‐CNF‐MnO2 shows the device capacitance of 47 F/g with a high energy density of 21 Wh/kg while the symmetric device shows 5 and 5.6 Wh/kg for negative and positive electrodes respectively. The high energy density and electrochemical stability of the prepared asymmetric device is promising for electrochemical energy storage in aqueous electrolyte.