Electrochemically Exfoliated Graphene/Manganese Dioxide Nanowire Composites as Electrode Materials for Flexible Supercapacitors

Flexible supercapacitors are of great significance for the development of intelligent electronic products and wearable devices. Herein, through reasonable design, self-supporting flexible film composites that can be used as supercapacitor electrodes, are synthesised by vacuum filtration. The composites are composed of electrochemically exfoliated graphene nanosheets and MnO2 nanowires, in which the graphene nanosheets mainly play the role of skeleton support, enhance conductivity, and provide electric double-layer capacitance, while the MnO2 nanowires mainly provide pseudocapacitance. Results show that the sample with 20 % MnO2 possesses the best electrochemical performance due to the mass ratio which can give full play to the pseudocapacitive properties of MnO2 and the conductivity of graphene. The maximum mass specific capacitance reaches 106.2 F g−1 at 0.5 A g−1, and the areal specific capacitance is 767.0 mF cm−2 at 1 mA cm−2. The electrode also maintains 86.7 % of the initial capacitance after 10000 cycles, indicating good cyclic stability. Furthermore, an asymmetric solid supercapacitor based on flexible thin films is assembled. The energy density is 20.7 W h kg−1, the power density is 1000 W kg−1, and the capacitance remains 84.2 % after 3000 cycles at 5.0 A g−1. These results suggest that the as-prepared self-supporting material has the potential to be used to construct flexible supercapacitors for wearable equipment.