A self-supporting graphene/MnO2 composite for high-performance supercapacitors

A self-supporting graphene (SSG) was prepared by electrochemical re-intercalation of a flexible graphite sheet (FGS) in the (NH4)(2)S2O8 electrolyte. The in-situ grown SSG rooted in the unexpanded FGS substrate which acted as a current collector. A thin, homogeneous and conformal MnO2 layer was coated on the surface of SSG by microwave-assisted deposition. The obtained FGS-SSG/MnO2 electrode displayed the areal and specific capacitances as high as 2.8 F cm(-2) and 465 F g(-1) at 2 mV s. An asymmetric supercapacitor of FGS-SSG/MnO21/FGS-SSG was assembled, which exhibited a maximum energy density of 25.6 Wh kg(-1) at a power density of 1000W kg(-1). In addition, the capacitance retention ratio of FGS-SSG/MnO2//FGS-SSG reached 87% at the current density of 1 A g(-1) after 5000 charge discharge cycles. High electrochemical properties indicate that the FGS-SSG/MnO2 is a promising electrode for supercapacitors. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.