▎ 摘　　要

High theoretical capacitance of MnO2 nanoparticles were successfully electrodeposited on the conductive graphene/activated carbon (GN/AC) composite film, and the urchin type MnO2 microspheres were controlled by adjusting the electro-deposition reaction times. The GN/AC/MnO2-1200s composite electrodes exhibited a maximum specific capacitance of 1231 mF/cm(2) (MnO2 loading mass of 7.65 mg/ cm(2) and the mass specific capacitance of 123 F/g) at a current density of 0.5 mA/cm(2). The assembled flexible solid-state symmetric supercapacitor had a good mechanical flexibility (about 88.6% of its original capacitance after 500 bending times) and prominent cycling stability (about 82.8% retention in capacitance over 10000 cycles). More importantly, the device could possess a maximum energy density of 0.27 mW h/cm(3) and a maximum power density of 0.02 W/cm(3). These results well demonstrate a great potential for applications of GN/AC/MnO2 composite electrodes in flexible energy storage devices.