The past decade has witnessed subst

The past decade has witnessed substantial achievements on electrochemical energy storage in employing graphene-based composites; however, of which have been usually produced on a laboratory scale with a limitedcompatibility with future industrialization. Herein a facile, cheap, and scalable sonochemical method was developed to prepare MnO2/graphene composite electrodes for supercapacitors. Petal-like MnO2 arrays weredensely grown on the surface of graphene oxide followed by annealing at 220 °C under an air atmosphere. Theas-fabricated MnO2/graphene hierarchical composite electrodes deliver 292.9 and 156.1 F/g at 5 and 100 mV/s,respectively, showing higher specific capacitance and better rate capability compared to the MnO2 electrode. Anexcellent cyclability with a capacitance retention as high as 91.5% was also achieved for the composite electrodes after running 1000 cycles. Such excellent electrochemical performances are ascribed to the robustcomposite structure and synergetic contribution from petal-like MnO2 arrays and conductive graphene sheets.