Metal oxides (like MnO2, Fe2O3, and Co3O4, etc) based supercapacitors have disadvantages, such as low volumetric capacitance for thick-film electrodes, or short cycling life because a Faradaic process involves chemical changes of state of the reactant species. In the present work, we report that supercapacitors based on reduced graphene oxide and maghemite (gamma-Fe2O3) composites (G gamma M) exhibit superior performance. G gamma M electrodes with average electrode thickness up to similar to 60 mu m have a high volumetric capacitance of 230 F cm(-3), together with an outstanding electrode package density of 1.44 g cm(-3). Particularly, the GgM electrodes have excellent cycling performance of similar to 90% capacitance retention over 100,000 galvanostatic charge-discharge cycles or voltage floating at 0.9 V for 300 h. No detectable change in phase and an effective inhibition of gamma-Fe2O3 refinement after cycle-life test are confirmed by X-ray diffraction and transmission electron microscopy. (C) 2015 Elsevier Ltd. All rights reserved.