MORPHOLOGY OF THE PASSIVE LAYER FORMED ON A LITHIUM ANODE .1. A SIMPLE THEORETICAL APPROACH

We propose a new approach for describing some aspects of the morphology of the passive layer which appears between a lithium anode and an organic solvent. We focus attention only on the structure of the overall passive layer. In this initial model, the geometry of the layer is represented by an ensemble of cylinders perpendicular to the electrode. This structure is defined by a small number of geometrical parameters (the radius of the cylinders, the porosity, etc.) which are determined by the chemical nature of the material and some physical properties such as the interfacial tension and the density of deformation energy. For a given configuration of the interface, we calculate the part of the Gibbs energy which is geometry-dependent. By a minimization procedure we can relate the geometrical parameters to the physical ones. This simple approach may describe various morphologies: cylinders isolated in a solvent or channels of solvent crossing a compact solid. Although the model represents an oversimplified view of the passive layer, it is used to analyse some experiments in various solvents. © 1990.