Dynamic impact response of lithium-ion batteries, constitutive properties and failure model

Use of lithium-ion batteries in transportation necessitates understanding of the cell mechanical response in case of a vehicle accident. Many researchers have access to test equipment to characterize the behavior of cells at low speeds. However, testing batteries at high speeds requires special setups that are not available for many interested parties. In this research, a methodology is proposed for predicting the material response and failure patterns of lithium-ion batteries subjected to high impact based on the experimental results at lower velocities. For this purpose, a constitutive law was proposed and parameters were calibrated for two types of lithium-ion cells, pouch and elliptical. Test results at lower impact velocities (up to 0.5 m s^-1) were used for calibrating the constitutive response and the failure criteria. The test data at higher impact velocities of up to 5 m s^-1 were used for validation. A Johnson-Cook type strain rate sensitivity model could successfully capture the strain rate hardening response of both cell types. Finite element models were developed for each cell type and empirical linear relationships were found between failure strain and strain rate. For the case of pouch cells, this correlation was negative, whilst there was a positive correlation for elliptical cells. The FE models closely followed the experiments in terms of load-displacement behavior and predicted the peak load and punch displacement at the onset of short circuit with good accuracy.