Auger and X-ray photoelectron spectroscopy on lithiated HOPG

This work deals with the investigation of lithiated graphitic anodes by Auger electron spectroscopy (AES) using highly ordered pyrolytic graphite (HOPG) as a model system. We show that the detection of intercalated lithium is very sensitive to effects during the AES measurement that are related to electron beam damage, Ar sputtering effects and the influence of the ultra-high vacuum conditions. An explanation of inconsistencies arising from different interpretations of the same system is given. We do so by comparing two different ways of surface preparation used to remove the solid electrolyte interphase on top of electrochemically charged HOPG, namely simple Ar+ sputtering, as it is commonly used in Auger depth profiles and in situ cleaving of the sample surface. A strong influence of the sputtering on the final result is evidenced by applying X-ray photoelectron spectroscopy and AES on these surfaces. Furthermore, the presence of a metallic lithium peak in AES that depends on the AES measuring parameters, the surface preparation and measuring time is presented in order to help people to avoid misinterpretation of their results. Copyright (c) 2016 John Wiley & Sons, Ltd.