Quantitative imaging method of metallic lithium surface density using muonic X-rays

Takeda, Shinichiro*; Katsuragawa, Miho*; Takahashi, Tadayuki*; Watanabe, Shin*; Chiu, I.-H.; Ninomiya, Kazuhiko*; Arai, Toshihiko*; Onishi, Mitsunobu*; Tampo, Motonobu*; Shimomura, Koichiro*; Umegaki, Izumi*

Quantitative and non-destructive detection of metallic lithium (Li) deposition on Li-ion battery anodes is crucial for understanding degradation mechanisms and ensuring operational safety. Muonic X-ray spectroscopy (muXRS) is highly sensitive to light elements such as Li and enables probing of bulk materials; however, its application to practical devices has been limited by the lack of spatially resolved detection. In this study, we present an imaging system that extends muXRS by integrating a large-area silicon double-sided strip detector with a 3D-printed tungsten parallel-hole collimator. Using Li plate samples, we demonstrate quantitative two-dimensional imaging of metallic Li surface density with a spatial resolution of 5 mm. An image-processing method was developed to suppress crosstalk from carbon muonic X-rays and to correct beam non-uniformity, enabling reliable quantification. The system achieves a 1-sigma detection sensitivity of approximately 2.5 ug/mm, sufficient to detect localized Li accumulation. This approach extends muXRS from bulk-averaged analysis to spatially resolved measurement and provides a non-destructive tool for battery diagnostics.