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. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.