Evaluation of Material Analysis Methods for the Determination of the Composition of Blended Cathodes in Lithium-Ion Batteries

New fields of application, such as electromobility, place ever increasing demands on lithium-ion batteries in terms of quality and safety. In-line methods currently used for assessing the quality of the electrode foils in lithium-ion cells in the manufacturing process hardly allow any statements on quality-related microstructural features and are often limited in terms of precision and spatial resolution. This is particularly true for electrodes containing several different active materials (so-called material blends or blended cathodes). Not only their layer thickness and porosity, but also the distribution of the active materials within the electrode is crucial for the quality of the electrode. The active material distribution can be determined with several methods which differ, for example, in terms of precision, required effort, and spatial resolution. This work presents and evaluates common analytical methods - light microscopy, scanning electron microscopy, and energy dispersive X-ray analysis, as well as X-ray diffraction - for the determination of phase fractions with the aid of reference samples. Alongside the precision, criteria such as the sample preparation and measurement effort or the spatial resolution are considered.