Pseudocapacitors [1] store electrical energy faradaically by electron charge transfer between electrode and electrolyte. This is accomplished through electrosorption, reduction-oxidation reactions (redox reactions), and intercalation processes,[2] termed pseudocapacitance.
A pseudocapacitor is part of an electrochemical capacitor, and forms together with an electric double-layer capacitor (EDLC) to create a supercapacitor.
A pseudocapacitor has a chemical reaction at the electrode, unlike EDLCs where the electrical charge storage is stored electrostatically with no interaction between the electrode and the ions. An example is a redox reaction where the ion is O2+ and during charging, one electrode hosts a reduction reaction and the other an oxidation reaction. Under discharge the reactions are reversed.
Unlike batteries, in faradaic electron charge-transfer ions simply cling to the atomic structure of an electrode. This faradaic energy storage with only fast redox reactions makes charging and discharging much faster than batteries.
Double-layer capacitance and pseudocapacitance combine to produce a supercapacitor's capacitance value. Pseudocapacitance may be higher by a factor of 100 than double-layer capacitance with the same electrode surface.
References
- ^ B. E. Conway (1999), Electrochemical Supercapacitors: Scientific Fundamentals and Technological Applications, Berlin: Springer, pp. 1–8, ISBN 0306457369 See also Brian E. Conway in Electrochemistry Encyclopedia: ELECTROCHEMICAL CAPACITORS Their Nature, Function, and Applications
- ^ Marin S. Halper, James C. Ellenbogen, Supercapacitors: A Brief Overview, MITRE, March 2006 [1]