Comprehensive modeling of lithium-ion batteries at the system level to minimize experimental lifetime testing effort

The operating conditions of lithium-ion batteries substantially influence their aging behavior. In interconnected systems, these conditions differ from one cell to another, and hence, analyzing aging solely at the cell level is inadequate. System-level lifetime tests are costly and require significant time because of their inherent complexity. This study introduces a comprehensive approach for the modeling of batteries at the cell and system levels to reduce the need for extensive experimental testing. The system model incorporates an equivalent circuit electrical and a lumped thermal cell model, along with four integrated semi-empirical aging models to consider the degradation of the capacity and all three resistances. A parameterization for each model, requiring minimal experimental testing effort, is included. The electro-thermal system model is validated using commercial cells and self-assembled modules with each 16 cells in series, parallel, and series-parallel connection. A simulation-based sensitivity analysis shows that pronounced variations in the cell capacity within interconnected battery systems significantly impact the degradation process due to their influence on the aging stress factors. • Framework including electrical, thermal, and aging models at the system level • Usage of four aging models to account for degradation of dynamic cell properties • Validated using modules with series, parallel, and series-parallel configuration • Cell-to-cell capacity variations benefit system lifetime by increasing temperatures