Unique nanostructure, high electrical conductivity, satisfactory energy density, and extraordinary cycling stability are important evaluation criteria for high-efficient energy storage devices. Herein, Fe3O4 nano-spheres are successfully in situ decorated on graphene nanosheets through an environmentally benign and facile solvothermal procedure. When utilized as an electrode for supercapacitor, the graphene/Fe3O4 nanocomposite exhibits a notably enhanced specific capacity (268 F.g(-1) at 2 mV.s(-1)) and remarkable cycling performance with 98.9% capacity retention after 10,000 cycles. Furthermore, the fabricated graphene/MnO2//graphene/Fe3O4 asymmetric supercapacitor device displays a desirable energy density (87.6 Wh.kg(-1)) and superior cycling stability (93.1% capacity retention after 10,000 cycles). (C) 2018 Elsevier Inc. All rights reserved.