Detection of Metallic Li Deposition in a Laminated Li-Ion Battery Using Muonic X-rays

The nondestructive detection of metallic lithium (Li) within lithium-ion batteries (LIBs) is essential for both ensuring safety and assessing battery quality prior to reuse. In this study, we demonstrate that elemental analysis with muonic X-rays offers a quantitative approach for identifying metallic Li deposition on graphite anodes in a laminated LIB. The technique leverages the preferential capture of negative muons by metallic Li over Li intercalated in graphite, resulting in detection of metallic Li. By applying this method to laminated LIBs with varying amounts of metallic Li, we established a standard curve correlating the muonic X-ray signal intensity with the areal density of metallic Li. Our approach achieves a detection limit of 0.01 mg/cm², corresponding to a few percent of the battery's theoretical capacity─well below the threshold relevant for reuse criteria. This technique provides a powerful, nondestructive diagnostic tool for monitoring and quantifying metallic Li in LIBs, offering valuable insights into degradation mechanisms and supporting the development of safer, longer-lasting battery systems.