Development of Detailed Model and Simplified Model of Lithium-Ion Battery Module under Mechanical Abuse

In order to obtain a good understanding of mechanical behaviors of lithium-ion battery modules in electric vehicles, comprehensive experimental and numerical investigations were performed in the study. Mechanical indentation tests with different indentation heads, different loading directions and different impact speeds were performed on battery modules with prismatic cells. To mitigate thermal runaway, only fully discharged battery modules were used. The force-displacement responses and open circuit voltage were recorded and compared. It was found that the battery modules experienced different failure modes when subjected to mechanical abuse. Besides internal short circuit of cells, external short circuit from bus bar and vapor leakage of electrolyte were also found to deteriorate the mechanical and electrical integrity of the tested modules. Mechanical anisotropy and dynamic effect were found on the battery module. Calibration of main components in the battery module were then conducted and a detailed finite element model was developed accordingly with LS-DYNA. Mechanical anisotropy, strain-rate effect and failure criteria were all considered in this detailed module model. This model is capable of predicting the mechanical responses of the tested module at varied load cases. Furthermore, we also documented the homogenization approach for a simplified module model from the developed detailed module model, to meet the requirement of fast prediction in larger scale simulation such as battery pack or vehicle crash. Multiple components of the battery cell were homogenized as one block. The simplified module model is also capable of predicting the mechanical responses of the tested module at varied load cases with lower computational cost.