Simultaneous stirring and microwave assisted synthesis of nanoflakes MnO2/rGO composite electrode material for symmetric supercapacitor with enhanced electrochemical performance

Nanoflakes MnO2/reduced graphene oxide (NMG) composite and MnO2 nanoflakes (MN) were successfully synthesized through a modified method in which periodic repetition of stirring and microwave irradiation simultaneously were done for 21 cycles. The as-synthesized samples were characterized using X-ray diffraction, Fourier transformed infrared spectroscopy, Scanning electron microscopy, Energy-dispersive X-ray spectroscopy and Brunauer-Emmett-Teller analysis. Symmetric supercapacitors were fabricated using prepared MN and NMG composite as electrode materials. The NMG symmetric supercapacitor exhibited higher specific capacitance (140.3 Fg(-1) at 1 mA) and specific capacitance retention (91%) than MN symmetric supercapacitor. At the same time, the NMG symmetric supercapacitor also delivered a maximum energy density of 19.5 Wh kg(-1) at a power density of 633.7 W kg(-1) and remained 17 Wh kg(-1) at 1864.3 W kg(-1). Moreover, the efficiency of this composite symmetric supercapacitor is 99.4% retained even after 5000 charge/discharge cycles at 2 mA current.