Crashworthiness of large format prismatic Lithium-ion cells

Sammanfattning

With the growing adoption of lithium-ion batteries in transportation, understanding how they will behave under the complex loading scenarios of a crash has become critical. Moving batteries, such as the ones found in electric vehicles, are exposed to working conditions that include changing speeds, accelerations, and temperatures. While advanced mechanical models predicting the response of these batteries under these conditions exist for other cell formats, large prismatic cells have yet to be exhaustively characterized. This thesis addresses this gap by building a model used for finite element simulation methods based on the analysis of experimental data which captures the effects of temperature and strain rate. The results reveal a strong dependence of mechanical response on both strain rate and temperature. Notably, under extreme conditions, the maximum load prior to short-circuit decreases by 40% and stiffness is also reduced by about 33% when compared to the room temperature-static scenario. These findings highlight the limitations of using a quasi-static room-temperature constitutive model and the need for a more robust model able to capture this behavior better. A constitutive model based on the Deshpande-Fleck yield surface has been developed and calibrated using experimental data through finite element method simulations. This model has been verified comparing the results of said simulations to experimental results. This model yields strong agreement with experimental load-displacement curves, validating its suitability for crashworthiness simulations of prismatic cells.