Electrode Stack Geometry Changes during Gas Evolution in Pouch-Cell-Type Lithium Ion Batteries

Safety remains a significant concern for the lithium-ion battery industry, despite over twenty five years of development since their commercial introduction [R. Spotnitz and J. Franklin, J. Power Sources, 113, 81, (2003)]. Many abusive conditions (such as overheating, overcharge, overdischarge, and electrical short) can give rise to gas evolution in lithium ion batteries, which causes increased pressure and/or expansion of the cell leading to changes in the electrode geometry that can lead to significantly different electrochemical performance and safety characteristics [Y. Qi, S. S. J. Harris, J. Electrochem. Soc., 157, A741 (2010)]. In order to characterize the cell-level changes that occur during gas evolution, a non-destructive technique is required that can image the internal components of the cell at high spatial resolution without perturbing the electrode assembly itself. This paper demonstrates the use of synchrotron-based computed tomography to characterize the changes in electrode geometry that occur during gas evolution in a commercial aluminum pouch cell.