Wrinkled Flower-Like Reduced Graphene Oxide for High-Performance Supercapacitors

The preparation of reduced graphene oxide (rGO) by an oxidation-reduction chemical reaction is very extensive. However, during the oxidation process, the obtained graphene oxide (GO) is usually not uniform in size and contains some incompletely oxidized graphite particles. To obtain uniformly small-sized GO and remove impurities, we put forward here a simple suction filtration process, that is, when GO passes through the filter, it is preferentially selected. In this way, we provide a facile but effective method for the screening of GO and then obtain wrinkled flower-like rGO (WF rGO) with excellent electrochemical performance. We also perform a design of experiments to optimize the reduction procedure. It is found that such factors as the reaction time, temperature, reductant and KOH content all affect the microstructure and electrochemical properties of rGO. With the optimized reduction procedure used, the specific capacitance of rGO can reach 231 F/g at the current density of 0.5 A/g. Furthermore, through the suction filtration along with the optimization of reduction, the WF rGO shows a much higher specific capacitance of 272 F/g. On this basis, the energy density of a symmetric rGO//rGO capacitor device arrives at 10.9 Wh/kg at a power density of 0.5 kW/kg and 8.2 Wh/kg at 12.6 kW/kg, and the capacitance keeps 91.5 % after 10,000 cycles. Moreover, the WF rGO//WF rGO device possesses a significantly higher energy density of 12.1 Wh/kg at a power density of 0.5 kW/kg and 9.7 Wh/kg at 24.2 kW/kg, and the capacity perfectly remains 94 % of its initial value after 10,000 cycles.