Cu particles induced distinct enhancements for reduced graphene oxide-based flexible supercapacitors

Abstract

Novel Cu/reduced graphene oxide (Cu/RGO) supercapacitors with excellent performance were prepared via a proposed low-temperature, binder-free, and low-cost solution route. Transmission electron microscopy analysis shows the as-synthesized Cu nanoparticles (NPs) are highly crystalline, and the associated redox reactions during charging/discharging cycles take place partially only in the exterior, leaving behind the central part as highly crystalline Cu with high conductivity. The cyclic voltammetry measurements show the Cu/RGO composites with different Cu NP sizes demonstrate distinct enhancements for energy and power densities at low and high scan rates compared with RGO. The galvanostatic charging/discharging measurements show that the capacitor with the smallest Cu NPs has a high specific capacitance of 335 F/g, energy density of 47 Wh/kg, and power density of 804 W/kg at a current density of 1 A/g. Cyclic life tests show the capacitance is increased to 125% of the initial value after 3400 cycles, and then demonstrates excellent cyclic stability to 8000 cycles without decay at a high current density of 5 A/g. The employment of metal NPs as pseudocapacitance materials in RGO-based supercapacitors opens up the opportunity to fabricate excellent flexible supercapacitors.