Evaluation of ultrasonic battery inspection techniques

Lithium metal batteries are prone to subtle defects such as internal dendrites, which can cause internal short circuits and lead to catastrophic ignition. These defects are often undetectable by battery management systems, prompting the need to advance the development of nondestructive evaluation (NDE) techniques for battery applications. Ultrasonic inspection techniques are being evaluated as a means of identifying flaws and irregular lithium plating that can be a precursor to dendrite formation and, ultimately, battery failure. Two ultrasonic approaches were compared in this study to assess their relative merits for battery inspection. The first was local ultrasonic resonance spectroscopy (LURS), which measures the local through-thickness resonances of the battery to detect changes in structure. The second technique was guided wave ultrasound, which was assessed for its potential for in situ monitoring. Guided wave testing was performed via pitch-catch testing using piezoelectric electric wafer active sensors (PWAS), as well as line scans via laser Doppler vibrometry (LDV). Both measurement modes were applied to lithium metal pouch cell batteries seeded with lithium chips emulating localized plating. The results show the ability to detect and monitor the internal structure of batteries for relatively coarse defects and highlight use cases for each of the two inspection modalities.