Influence of State of Charge on Deformation Induced Mechanical Failure in Li-Ion Cells

Evaluation of crashworthiness safety of lithium ion batteries is of growing importance due to their usage in battery packs for EV applications. Crash event may lead to deformation of cells in the battery pack causing short circuits or contact of cathode and anode due to separator damage. This leads to hot spots and subsequent electrolyte decomposition, heat and vent gas generation and hazardous thermal runaway events. Battery state of charge (SoC) is an important factor while evaluating the mechanical response of cell to deformation and the short circuit and thermal runaway behavior. In this research, quasi static deformation tests are performed on 18650 battery cells with different SoC values to understand the SoC dependent mechanical behavior and short circuit of Lithium ion Batteries. The structural and electrical response of the Lithium Ion battery (LiB) under loading is assessed. The failure stresses and buckling loads are computed for compression and bending tests respectively. Results show that mechanical and electrical behavior of LiB is highly dependent on SoC. The results shed light on the failure behavior of the Lithium Ion batteries and aid in enhancing crash safety of LiBs and design of related systems.