J. Kim, A. Rivas, S. Wu, V. Martinez, F. Contreras, J. Castro, E. Botello, T. Kidd, S. Dobbs, Z. Yu
California State Polytechnic University, Pomona,
Keywords: graphene, supercapacitor, power storage
Summary:Supercapacitors are getting significant attention in recent years due to their quick charge/discharge capabilities, long cycle lives and are environmentally friendly. Supercapacitors can provide necessary power in short bursts. Aiming to reduce the weight and volume of traditional lithium-ion batteries, supercapacitors are already being used in hybrid vehicles, laptops, airplanes, electric trains, and anywhere a sudden burst of power is need in a very short time [1-7]. Supercapacitors store and release energy by the interactions between the electrical double layer of electrolyte ions on the surface of conductive electrodes and the charge accumulated at the active electrode during the charge/discharge process. Currently, students and faculty from Electrical & Computer Engineering and Chemistry & Biochemistry departments are collaborating to use different methods to improve the performance of supercapacitors, and enable electric unmanned aerial vehicles (UAVs) for long endurance flights [8-9]. Supercapacitor electrodes are made of a porous material with an extraordinarily high specific surface area, such as activated carbon, or graphene applied to a conductive metallic current collector. Electrodes must have good conductivity, high temperature stability, long term chemical stability, high corrosion resistance and high surface area. Other requirements include environmental friendliness and low cost for mass production. Aluminum or steel foil as a potential electrode material can be widely used in a supercapacitor due to its inexpensive, lightweight, easily accessible and good conductive characteristics. Also, the capacitor structural properties are being investigated to see if the capacitor materials could replace some of the UAV load bearing structural materials to reduce the power system’s parasitic weight. In this work, we report how a change in electrolyte from polyvinyl acetate (PVA/ ) to sulfuric acid ( and phosphoric acid ( ) can affect specific capacitance, resistance, charge/discharge capabilities and cycle lives. Figure 1 shows the schematics and the as-fabricated graphene supercapacitor for using in the UAVs power storage system. In conclusion, the fabricated electric storage devices provided the operating voltage about 1.9V with a capacitance of 0.827µF and a good cycling performance.