Understanding the effect of cycling lithium-ion pouch cells under stress using neutron diffraction

Large volume changes of lithium-ion batteries during battery operation affect battery lifetime and performance through mechanical degradation. Therefore, understanding the coupling between mechanics and electrochemistry in these systems is crucial. In this work, we use neutron diffraction to learn how commercial lithium-ion pouch cells are affected by stack pressure during charge and discharge. We find that a change in stack pressure affects the phase transitions in electrode materials, requiring more charge to reach higher state-of-charge phases which results in effective capacity loss for the battery. Also noteworthy is that the copper current collector experiences strain during charge and discharge due to the expansion of the graphite anode, something often overlooked in these systems.