In-depth study of structural, morphological and electronic changes during conversion and alloying of ITO

Abstract

The combination of good electronic conductivity and optical transparency of indium tin oxide (ITO) have made it an indispensable material for large-area electronics. Similarly, the combination of good electronic and ionic conduction properties of ITO makes it interesting for use in Li-ion batteries. Many of the applications rely on the retention of ITO's significant electronic conductivity over a large range of operating potentials. However, ITO is known to react with Li-ions through conversion and subsequent alloying reactions. Consequently, the use of ITO in Li-ion batteries depends on the properties at the potential of interest. In this work we used an ITO thin-film model system for a systematic study of how the films properties change during the lithiation and delithiation processes. A test structure was designed to measure the electronic conductivity through the film at different stages of the conversion and alloying processes. Changes in the conductivity were complemented by a meticulous physico-chemical characterization at a microscopic scale, combining an array of characterization techniques, including AFM, C-AFM, ERD, RBS, SEM, and XRD. As such, a clear picture of the link between the microscopic observations and changes in the macroscopic conductivity was established.