Examining supercapacitor characteristics in order to extend supercapacitor life

The quest for alternative energy sources / storage systems has never been more intense than it is at present, and one strong contender for the energy storage market is the supercapacitor, which is similar to a battery, but stores charge like a capacitor (where there are two metal plates and positive charges are stored on one plate while negative charges are stored on the other). Unlike typical capacitors, however, supercapacitors are able to store approximately a million times more charge on the same geometric area. There has been significant recent interest in the use of supercapacitors in vehicle applications (for cold starting assistance and hybrid fuel-cell capacitor car load levelling), power line backup, and energy storage for intermittent power sources (i.e., solar panels or windmill turbines). However, one very poorly understood aspect of supercapacitor behaviour which limits their practical application is the phenomenon of self-discharge (SD), the spontaneous loss of voltage exhibited by a supercapacitor as it sits charged for long periods of time. Obviously, this is of practical importance as one would like to know that the supercapacitor is ready for use, whether it has been unused for a day or a year. This research is designed to discover, and later overcome the causes of supercapacitor SD and study the factors which change the rate of this discharge. In order to examine the SD processes, the supercapacitor will be examined before and after SD using electrochemistry (using electricity to examine a system's characteristics). These experiments will allow us to examine the effect of SD on the charge and energy storage capability of the supercapacitor. Traditionally, a variety of species have been used as supercapacitor electrodes, including carbon, electronically conducting polymers, IrO2, RuO2 and MnO2. This work will initially focus on high surface area, stable carbon electrodes, but will expand to encompass both traditional and novel supercapacitor materials. By gaining a more complete understanding of the self-discharge process it is hoped that it can be minimized or even prevented altogether, thereby extending the life of the supercapacitor.