Misuse of XPS in Analyzing Solid Polymer Electrolytes for Lithium Batteries

One of the most powerful spectroscopic tools for battery analysis is X-ray photoelectron spectroscopy (XPS); however, its great power, must be accompanied by great responsibility for authenticity. Fluorine is documented to be unstable under XPS conditions, and fluorinated salts used in Li batteries show photodecomposition. As all-solid-state batteries advance, demand for surface characterization is increasing. Here, a popular solid polymer electrolyte comprising a fluorinated salt in a PEO matrix was measured by XPS. Rapid photodecomposition after few minutes produced mainly LiF, initially not found on the surface. Not being aware of such artifacts may lead to an erroneous analysis of the characterized electrochemical system.