Cyclic voltammetry analysis of an electrochemical double layer capacitor

Abstract

Present world is heading towards a serious energy crisis due to the mismatch between the supply and the demand which is increasing at an alarming rate. Main energy supply is from fossil fuels and the endangering state of fossil fuels is now well realized. This background has set the initiation of employing renewable energy sources for energy production. In par with that, requirement for energy storage has become an essential. Though batteries and conventional capacitors have been employed as energy storage devices, the present demand cannot be fulfilled only with them. Super capacitors have been recognized as a suitable solution and also as a bridge to link the gap between batteries and conventional capacitors. There are two types of super capacitors namely electrochemical double layer capacitors (EDLCs) and redox capacitors. This report presents about such EDLC fabricated using a polymer electrolyte and graphite electrodes. Polymer electrolyte is based on a polymer, a salt and an ionic liquid. For the preparation of electrodes, Sri Lankan natural graphite was used which might indirectly add a value to one of the natural resources in Sri Lanka. A thin electrolyte film was sandwiched in between two graphite electrodes deposited on aluminium substrate. The device is eco friendly and cost effective. Performance was evaluated using cyclic voltammetry technique which is a powerful analysis tool. One electrode was used as the working electrode while the other one used as the reference and counter electrodes.The potential window as well as the scan rate play a major role in determining the specific capacitance. Charge storage takes place purely via electrostatically. At higher scan rates, charge storage mechanism does not take place completely and hence, a reduction of capacitance is observed with increasing scan rate. The durability of the EDLC for long term operation is satisfactory.