Transport at Nanoscale Interfaces Laboratory

Safe and reliable laser ablation assisted disassembly methodology for cylindrical battery cells for post-mortem analysis

Aeppli, D., Gartmann, J., Schneider, R., Hack, E., Kretschmer, S., Nguyen, T. T. D., & Held, M.

Journal of Energy Storage, 83, 110571 (12 pp.). (2024).

Until today, disassembling cylindrical 18650 cells commonly involved using a pipe cutter and pliers, with a risk of short-circuiting and mechanical damage to the electrode materials. This study presents a novel laser ablation assisted disassembly method with X-ray and optical validation for opening cylindrical battery cells without damaging the jelly roll. The objective is to develop a safe, efficient, and reproducible approach for cell disassembly enabling post-mortem analysis of failure mechanisms and investigation of aging effects. X-ray and tube micrometer measurements are used to estimate the cell wall thickness, with good agreement between the two methods. Laser ablation is calibrated to determine the optimal number of laser cycles for achieving the desired ablation depth. In situ temperature measurements are conducted. Various cooling parameters are investigated, maintaining the cell temperature within a safe range of 17 °C to 35 °C during operation. The temperature remains significantly below the reported onset temperature of 57 °C for solid electrolyte interphase (SEI) decomposition. Depth analysis and surface morphology are conducted using confocal microscopy with interferometry and a fully automated digital microscope system. The cells are disassembled within an inert argon atmosphere. Challenges such as redeposition of ablated material and side trench formation are addressed. Overall, this method offers a safe, reproducible and efficient approach for opening cylindrical battery cells. This innovative approach fills a gap in the literature and contributes to advancements in failure analysis and degradation research for the benefit of cell producers, testing laboratories and research institutes.