Towards the realization of powerful and energetic electrochemical double layer capacitors

Abstract

In the last years, electrochemical double layer capacitors (EDLCs) have attracted a lot of interest because of their promising performances in terms of energy storage and power supply. Their ability of providing much higher power output in comparison to other devices (e.g. batteries) makes this technology suitable for many applications. Within the framework of this dissertation, the influence of the active material, the electrode preparation and the electrode mass ratio on the performances of an EDLC has been investigated in depth. A completely solvent-free electrode preparation route has been developed. The manufacturing parameters have been proved to be essential for obtaining electrodes with low equivalent series resistance (ESR) and diffusion resistance. The optimized hot-pressing condition has been found as 200 °C and 10 bar. Study on electrode recipe has shown that adding carbon black as conductive additive is unnecessary if the new solvent-free preparation method is employed. Furthermore, the PTFE binder content can be decreased as low as 5 %. Moreover, the optimized mass ratio between the positive and negative electrodes has been found to be m+/m- =1.086. In the second part, six carbonaceous materials have been tested as electrode active materials in order to obtain better understanding of the correlation between physical properties of the carbons and their electrochemical performances. The carbon types SV and S0 have the highest gravimetric and volumetric capacitance, respectively. They are considered as suitable candidates for high energy applications. On the other hand, the carbon type CB possesses the lowest total resistance and is considered as a good choice for high power applications.