Study of the Impact of Graphite Orientation and Ion Transport on EDLC Performance

A model study of electric double layer capacitor (EDLC)-style capacitors in which the electrodes were composed of low surface area-oriented flakes of graphite that compressed to form a paper-like morphology has suggested that ion transport rates significantly impact EDLC energy and power density. Twelve capacitors were constructed, each using the same model electrode material and the same aqueous NaCl electrolyte, but differing in relative electrode orientation, degree of electrode compression, and presence/absence of an ionic transport salt bridge. All were tested with a galvanostat over a range of discharge currents. Significant differences in energy and power density and estimated series resistance were found as a function of all the factors listed, indicating that capacitor performance is not simply a function of the electrode surface area. This simple postulation was advanced and tested against data: net ion (Na+, Cl-) 'velocity' during both charge and discharge significantly impacts capacitive performance.

Automated summary

A model study of EDLC-style capacitors with low surface area-oriented flakes of graphite electrodes compressed to form a paper-like morphology suggests that ion transport rates significantly impact capacitor energy and power density. Experimental results show that the net ion velocity during charge and discharge has a significant influence on the capacitor performance, indicating that it is not solely determined by the electrode surface area.