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

An impedance model for the electrochemical dissolution of lithium in alkaline solutions is presented. The construction technique of the impedance function depends on calibration to steady-state properties, described in Part II of this series. The model, which is based on the point defect model for the growth and breakdown of passive films, is used to identify effects of various electrolyte solutes on the properties of the lithium film. The high frequency experimental impedance data are explained by the existence of a capacitance that is voltage and frequency dependent, a property that is theoretically rationalized. It is concluded that electrolyte solutes influence the rate of water transport through the outer layer, rate constants, the polarization of the barrier layer/outer layer interface, and the porosity of the outer layer. Based on the shape of predicted impedance signatures, it is suggested that the derived impedance equation may be applicable to other systems. (C) 2001 The Electrochemical Society.