ELECTROCHEMICAL CAPACITOR

"A device that stores electrical energy using electrochemical cells. Two large-surface-area electrodes are used resulting in large double layer capacitance, and much of the storage capacity is due to the charging/discharging of the double layers. Some surface oxidation/reduction also occurs, but in contrast to reactions occurring in batteries, this is limited to a monolayer or two on the electrode surfaces. Consequently, the device behaves more like a capacitor than a battery (see pseudocapacitance). It is also called ""supercapacitor,"" ""ultracapacitor,"" or ""double-layer capacitor."" It is not to be confused with electrolytic capacitors. See also an Encyclopedia Article. Electrochemical capacitors typically have much larger power density but much smaller energy density than batteries. "