An ideal polarizable electrode (also ideally polarizable electrode or ideally polarized electrode or IPE) is a hypothetical electrode characterized by an absence of net DC current between the two sides of the electrical double layer, i.e., no faradic current exists between the electrode surface and the electrolyte.  Any transient current that may be flowing is considered non-faradaic. The reason for this behavior is that the electrode reaction is infinitely slow, with zero exchange current density, and behaves electrically as a capacitor.
The concept of the ideal polarizability has been first introduced by F.O. Koenig in 1934.