Different models of homogeneous, composite, and stratified surface layers have been investigated for the interpretation of impedance measurements of lithium electrodes in organic electrolytes. The surface layers are assumed to consist of organic and inorganic compounds with the properties of solid and polymer electrolytes. Comparison of predicted impedance spectra with those measured for surface layers formed in a molar solution of lithium percholate in propylene carbonate shows that with the use of assumed film properties two interphase models provide thicknesses of surface layers which agree with previous ellipsometer measurements: In a compact-stratified layer (CSL) model, the surface layer is assumed to consist of two sublayers of solid and polymer electrolytes; in a solid-polymer layer (SPL) model, the surface layer is assumed to consist of a mixture of solid and polymer electrolytes. the impedance behavior of the lithium electrode covered * Electrochemical Society Active Member.

The improvement of the lithium cycling efficiency obtained by substituting an aluminum substrate for a lithium substrate is explained by means of morphological and kinetic studies of the electrodes in the molar solution LiClO4‐normalpropylene carbonate . SEM observations show that the insertion rate of the lithium deposit into aluminum can be sufficiently high so as to avoid dendritic growth; ESCA analysis reveals that propylene carbonate leads to a chemical formation of a polymeric membrane on the electrodes, which is less important on the aluminum than on the lithium substrate. Electrochemical impedance measurements associated with polarization curve data point out that most of the surface is active, giving rise to an exchange current density of about 17 mA/cm2; these studies also demonstrate that diffusion processes in the passivating layer and in the bulk of the electrode are responsible for the limited lithium cycling performances with the aluminum substrate.

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