Direct Imaging of the Passivating Film and Microstructure of Nanometer-Scale SnO Anodes in Lithium Rechargeable Batteries

Abstract

The microstructure of nanometer‐scale anode materials used in lithium rechargeable batteries has been investigated using high‐resolution transmission electron microscopy (HRTEM) at deep discharge states of a cell. A passivating film formed by an irreversible electrolyte decomposition reaction on the surfaces of particles was observed. The composition of the film was analyzed by Fourier transform infrared spectroscopy and determined to consist of and . In the core regions of the particles, many crystallites dispersed in an amorphous matrix, were observed and identified to be a mixture of alloy and lithium metal by HRTEM. This provides direct evidence for the so‐called two‐step reaction mechanism for tin oxide anodes in lithium rechargeable batteries. ©1998 The Electrochemical Society