Modeling and Predicting Mechanically Induced Internal Short Circuits in Lithium Ion Battery Packs 2021-01-0750

As advances in electrification continue within the vehicle industry, improving the front-end design process and managing the safety aspects of lithium-ion batteries is increasingly important. Structural damage to lithium-ion batteries can cause internal short circuit, leading to a large energy release that can lead to fire and thermal runaway that propagates throughout the battery pack. Southwest Research Institute has developed a mechanical model that can accurately predict mechanically-induced damage to lithium-ion battery cells and battery packs. This model also predicts whether the external damage will cause an internal short-circuit. This modeling process was illustrated using 21700 cylindrical cells with NCA cathode chemistry. High-speed impact tests were used to calibrate a single cell model, which was then scaled to a 12-cell battery module. This model was then used to accurately predict the outcome of an impact test on a 72-cell battery module. A pack homogenization method enables this battery model to be efficiently scaled to model large battery packs and assist in virtual validation of battery packs before proceeding to expensive testing. In this paper, the modeling process is presented along with test results delineating the steps of calibration, scaling and validation.