Impact of temperature and state-of-charge on long-term storage degradation in lithium-ion batteries: an integrated P2D-based degradation analysis

This study utilizes a Pseudo-Two-Dimensional (P2D) model to predict calendar aging in LiFePO₄/graphite lithium-ion batteries, emphasizing temperature and state-of-charge (SOC) impacts. Implemented in COMSOL Multiphysics, the P2D framework simulates solid electrolyte interphase (SEI) growth and electrolyte conductivity loss, driven by parasitic redox reactions at the electrode–electrolyte interface, modeled using Arrhenius and Tafel kinetics. Validated against experimental data across five temperature–SOC conditions, the P2D model achieves root mean square errors below 0.9. Results show synergistic degradation, with SEI thickness exceeding 300 nm and conductivity loss over 20% after 36 months at 55 °C and 90% SOC. Higher SOCs intensify SEI growth due to electrolyte instability at elevated anode potentials. This P2D-based, chemically grounded approach provides mechanistic insights into storage degradation, enabling optimized battery management and storage strategies to enhance lifespan and reliability for electric vehicles and grid applications.