A numerical model for simulating thermal runaway propagation between lithium-ion battery cells with detailed heat transfer analysis

Numerical modeling has played a critical role on understanding and mitigating thermal runaway propagation (TRP) of Lithium-ion batteries (LIBs). However, computational cost for simulating this multi-physics process limits the scalability of the model. To help address this, in this study, a numerical model with a detailed Computational Fluid Dynamics (CFD) and a semi-empirical solid battery model is developed to investigate heat transfer and TRP in LIBs. The model development is based on thermal abuse tests of 18650 cylindrical cells using a previous test setup. The mass flow rate, compositions of vent gas, and pseudo-properties of the cell are obtained experimentally and implemented in the model as input parameters. This removes the need to simulate internal electrochemical reactions during thermal runaway, enabling a more general and cost-effective model. The model is used to simulate TRP between two adjacent cells with different spacings ( s = 0–4 mm). The results of 0 and 2 mm spacing cases are successfully validated against experimental data. Temperature profiles, cell surface heat fluxes, and heat transfer mechanisms are compared between different cases. The simulation results show that the dominant heat transfer mode varies with different stages of the event. For s > 0, heat transfer increases as the spacing decreases. However, radiation and convection alone are insufficient to trigger TRP. Only when s reduces to 0, cell-to-cell conduction is enabled and TRP occurs, consistent with experimental observation. A simplified thermal model is also developed to further understand the influence of spacings on convection and radiation. The numerical model developed in this study, with the potential to scale up and simulate more complex LIB TRP processes (including fires), can provide insights to inform design guidelines and support the development of safer LIB systems.