Utilization of Supercapacitor Electrode Materials

Devices for electrochemical energy converters which are capable of storing and delivering electric energy (i.e. secondary batteries/accumulators and supercapacitors) contain two electrodes (positive and negative one) with a mass and accordingly thickness governing the amount of stored energy ( volumetric and gravimetric energy density).

The particular construction of the electrode (porosity, thickness) control the possible current den­sities (rate of charge/discharge) and thus the volumetric/gravimetric power density. For a given cell and consequently the built-in electrodes the amount of stored energy usually falls rapidly with increasing current density. From the resulting display of power density and en­ergy density Ragone plots can be constructed. For obvious reasons thin electrodes and large surface areas provide highest power/power density. For equally obvious reason this cannot be a guideline for cell construction because a thin electrode has a relatively higher fraction of in­active material (current collector, mechanical support) than a thick electrode. The utilization of the electrode material, i.e. the fraction of active mass that is actually converted in the electrode reaction, may be much smaller than the total mass at a high current density, whereas at a lower current density more of the mass may be util­ized. In our research supercapacitor electrodes of different chemical composition prepared according to two different methodologies will be examined at widely varied current densities.