The Effect of Li-Ion Pouch Cell Shape on Electrochemical Aging during Fast Charging

High Resolution Image Download MS PowerPoint Slide Large-format pouch cells are widely used in electric vehicles (EVs), but they often exhibit electrical and thermal inhomogeneities. Previous studies have shown that these inhomogeneities are affected by the macroscopic design of the cell. However, how these inhomogeneities affect the degradation of large-format cells has yet to be investigated. This study employs a 3D coupled electrochemical, aging, and thermal model to investigate the mechanisms by which macroscopic design factors in large-format battery cells impact nonuniform degradation. Four cell designs were analyzed to assess the effects of tab location, tab width, and cell aspect ratio on degradation patterns. Simulations under a 2C fast-charging scenario at 25 °C focused on degradation from solid electrolyte interphase (SEI) formation, while simulations at −10 °C examined degradation related to lithium plating. Results indicate that designs with more significant electrical and thermal inhomogeneities experience more pronounced degradation inhomogeneities under SEI formation. Designs with higher local temperatures exhibited greater lithium loss due to the nonlinear relationship between temperature and SEI reaction rate. In terms of lithium plating, while greater temperature and electrical inhomogeneities also increased degradation nonuniformity, lithium loss patterns differed due to the complex interplay between current density, temperature, plating overpotential, and plating reaction rate. This study underscores the critical role of cell design in influencing aging mechanisms in large-format cells with implications for optimizing battery longevity and performance through advanced predictive models.