EDS with Low-Voltage SEM: Possibilities and limitations of lithium detection and quantification

Achieving reliable detection and quantification of lithium (Li) with high spatial resolution down to the nanometer (nm) range is a major challenge on the path to fully understanding lithium-ion batteries throughout their life span. This paper presents possible influencing factors, such as contamination, radiation damage and charging effects, on EDS analysis, as well as methods for detecting and avoiding these effects. A windowless EDS detector specialising in the detection of low-energy X-rays enables Li content analysis. Even in Li compounds with overlapping edges, the lithium content can be clarified. The systematic investigation of the detection of lithium in lithium metal and lithium compounds, lithium batteries, and the influence of sample preparation and storage is presented. The reliability and accuracy of EDS quantification on samples under non-ideal testing conditions is also investigated. A new method of quantifying lithium, 'Li by difference', is introduced, whereby the lithium content is calculated as the missing element fraction of a non-normalised EDS quantification.