Impact of an interrupted mechanical deformation on the electrical behavior of commercial lithium-ion pouch cells with varied aging histories for battery qualification

Abstract

This study investigates the influence of non-critical mechanical deformations, i.e., without internal short circuit (ISC), on lithium-ion batteries and examines their correlation with changes in electrical parameters. Nine commercial 50 Ah NMC111/Graphite pouch cells with diverse aging histories were electrochemically cycled before and after a controlled mechanical deformation. The results revealed consistent alterations in electrical parameters after deformation, including state of health (SOH) upon discharging, Coulombic efficiency, constant current discharge time (CCDT), voltage relaxation profile (VRP) voltage, VRP slope, and Area VdQ. Morphological changes due to deformation affected the overall electrical cell behavior. The deformation-induced effects are attributed to electrolyte shifting and electrode cracking which leads to loss of active material (LAM), whereas the morphological changes directly contributed to increased internal resistance (IRI) and an increase in the heterogeneity of the current distribution over the electrode surface. Distinct effects were observed in different-aged cells, with non-electrically aged cells being more affected by the electrode cracking and the current imbalances increase. The study underscores the high importance of early detection of non-critical mechanical deformations for ensuring battery safety and makes valuable contributions to battery qualification and the assessment of second-life batteries.