Electrochemical Capacitors (ECs)

Technology Description

Electrochemical capacitors (ECs) store electrical energy in the two series capacitors that exist in the electric double layer (EDL) at the interface of each electrode and the electrolyte solution. The distance over which the charge separation occurs is just a few angstroms. The capacitance and energy density of these devices is thousands of times larger than electrolytic capacitors.

The electrodes are often made with porous carbon material. The electrolyte is either aqueous or organic. The aqueous capacitors have a lower energy density due to a lower cell voltage but are less expensive, have a lower resistance, and work over a wider temperature range. Compared to lead-acid batteries, ECs have lower energy density but they can be cycled tens of thousands of times and are much more powerful than batteries (fast charge and discharge capability).

While small electrochemical capacitors are a fairly mature technology, the units with higher energy densities are still under development. Sometimes technologies known as asymmetrical capacitors, which use metal for one of the electrodes and which have a significantly larger energy density than the symmetric capacitors, are included in this group. An asymmetrical capacitor has been included in a lead-carbon battery and is known by the trade name ‘ultra-battery’. Information on this device is included under advanced lead-acid batteries.

April 2010

Current Developers/Suppliers

ELIT
ESMA
NESS
PowerCache (Maxwell)
PowerSystem Company
SAFT