A semi theoretical approach of the second plateau appearing during the discharge of aged nickel oxyhydroxide electrodes

A semi theoretical explanation of the appearance of a second plateau during the discharge of overcharged nickel oxyhydroxide electrodes (NOHE) is prop osed, based on transmission line models of the charge-discharge processes o f the active matter. The model takes into account the double electronic and protonic conduction involved in nickel II alpha and beta or nickel III bet a and gamma phases: electrons and protons reach the transformation front in side the matter through the less resistive paths. The secondary plateau may occur when a resistive layer of beta(II) isolates the transformation front from the nickel electron sink. (C) 2000 Elsevier Science S.A. All rights r eserved.