ABSTRACT
Supercapacitors, also known as electrochemical capacitors or ultracapacitors, store electrical charge in the electric double layer at an electrode-electrolyte interface, primarily in a high-surface area electrode. The high surface area and the small thickness of the double layer (in the order of angstrom) enable these devices to exhibit high specic and volumetric energy and power density with an essentially unlimited charge-discharge cycle life. The operational voltage in these devices is governed by the breakdown potential of the electrolyte and ranges usually between <1 and <3 V for aqueous and organic electrolytes, respectively.1-3
The concept behind the supercapacitor mechanism was known since the late 1800s. The rst supercapacitor device, based on double-layer charge storage (using carbon electrodes), was built in 1957 by H.I. Becker of General Electric for which he was granted a U.S. patent (No. 2,800,616).4 Figure 1.1 shows a diagrammatic representation of this device.
