X-Ray Photoelectron Spectroscopy (XPS) finds wide applications in the characterization of battery materials, due to its chemical sensitivity, capability to detect lithium and discriminate its presence in different chemical species. Traditionally XPS has been used for chemical analysis. However, this technique can provide additional valuable information, going beyond the mere identification of the chemical species present on the surface of the electrodes, to give a deeper understanding of their distribution and evolution as a function of number of cycles.
In this seminar, I will provide a prospective on the application of X-ray Photoelectron Spectroscopy for the characterization of battery materials. Using Si-anode as model electrode, I will discuss the use of Angular Resolve (AR)-XPS to study the formation of the Solid Electrolyte Interface in its early stage and to provide insights into its chemical instability. In the second part of the talk, I will show how quantitative analysis of the SEI components as a function of state of charge can help understanding the so-called “breathing effect”, i.e. the variation of SEI thickness upon state of charge. This study represents an example of how XPS can be used to understand the electrolyte decomposition reactions and to identify the root-cause of the poor first cycle Coulombic efficiency.