Electrochemical behavior of lithium in alkaline aqueous electrolytes - III. Impedance model

An impedance model for the electrochemical dissolution of lithium in alkali ne solutions is presented. The construction technique of the impedance func tion depends on calibration to steady-state properties, described in Part I I of this series. The model, which is based on the point defect model for t he growth and breakdown of passive films, is used to identify effects of va rious electrolyte solutes on the properties of the lithium film. The high f requency experimental impedance data are explained by the existence of a ca pacitance that is voltage and frequency dependent, a property that is theor etically rationalized. It is concluded that electrolyte solutes influence t he rate of water transport through the outer layer, rate constants, the pol arization of the barrier layer/outer layer interface, and the porosity of t he outer layer. Based on the shape of predicted impedance signatures, it is suggested that the derived impedance equation may be applicable to other s ystems. (C) 2001 The Electrochemical Society.