Innovative L-band electron paramagnetic resonance investigation of solid-state pouch cell batteries

Abstract. Usually, the conventional electron paramagnetic resonance (EPR) spectroscopy and imaging use a microwave cavity operating at X-band, i.e. with an excitation frequency of around 9.6 GHz, and remains the most popular mode in the magnetic characterization of lithium batteries to date. We provide here the first low-frequency EPR investigations for monitoring the metallic lithium structures in the solid-state pouch cell batteries. We show that L band, i.e. a microwave frequency of around 1.01 GHz, is an invaluable method to probe in depth the electrode components through a standard pouch cell using aluminum laminated film for packaging without opening the battery. These results offer a new approach for monitoring the nucleation of micrometric and sub-micrometric lithium particles such as dendritic lithium structures which is an important step in the development of reliable solid-state batteries.