Revision: 21-3-10

Subject to change without notice

17

The operating principle of the super capacitor is similar to that of a battery. Pairs of

electrodes are separated by an ionic conductive, yet electrically

insulating, separator (Fig. 2). When a super capacitor is charged, electronic charge

accumulates on the electrodes (conductive carbon) and ions (from the electrolyte) of

opposite charge approach the electronic charge.

This phenomenon is coined "the double layer phenomenon".

The distance between the electronic and the ionic charges is very small, roughly 1

nanometer, yet electronic tunneling does not occur.

Between charging and discharging, ions and electrons shift locations.

In the charged state a high concentration of ions will be located along the

electronically charged carbon surface (electrodes).

As the electrons flow through an external discharge circuit, slower moving ions will

shift away from the double layer. During EDLC cycling electrons and ions constantly

move in the capacitor, yet no chemical reaction occurs.

Therefore electrochemical capacitors can undergo millions of charge and

discharge cycles. This phenomenon which occurs with carbon electrodes of very high

surface area and a three-dimensional structure, leads to incredibly high capacitance

as compared to standard capacitors.

One can envision the model of the EDLC as two capacitors formed by the solid

(carbon) liquid (electrolyte) interphase separated by a conductive ionic

membrane. An equivalent electronic model is two capacitors in a series

We conclude that the energy density of electrochemical capacitors is higher than that

of electrolytic capacitors, and therefore they have applicability for systems with lower

frequency requirements.

Fig. 2

Fig. 3

Electrochemical Capacitors

Electrochemical Capacitors

Electrochemical Capacitors

Electrochemical Capacitors

Electrochemical Capacitors

Electrochemical Capacitors

Electrochemical Capacitors

Electrochemical Capacitors

Anode

Cathode

Separator

Current Collector