Model experiments with Auger electron and X-ray photoelectron spectroscopy at lithiated graphite material: Surface changes related to ion- and electron-beam effects

Abstract

Li-based batteries as a key element for green energy economy should be permanently improved in their performance. Therefore, the complex electrochemical processes in such batteries have to be understood in detail. For their characterization beside (electro-)chemical methods also electron spectroscopic methods such as X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) are used to get more insight into the chemical processes at the surfaces. One crucial point is stability of the solid electrolyte interface (SEI) upon measurements, especially at the (graphite-)anodes. In this paper, we use highly oriented pyrolytic graphite (HOPG) as a model anode material, which was lithiated in a molten metal intercalation process. Strong beam damage effects at the lithiated HOPG under electron and ion beam radiation are observed and described. These effects are important for using of local electron beam investigations and sputter depth profiling, often applied also for SEI characterization.