Prediction of thermal runaway of pouch-type lithium-ion battery cell using two-way nonlinear mechanical-electrochemical-thermal coupled analysis method

Lithium-ion batteries (LIBs) are used in a wide range of applications, from portable electronics to electric vehicles, but there have been ongoing safety concerns about thermal runaway. Thermal runaway of LIBs is caused by a cascade of interacting mechanical, electrochemical, and thermal reactions. In this study, we propose a two-way nonlinear mechanical-electrochemical-thermal coupled analysis method of a pouch-type LIB cell. This method used a detailed layer model that implemented all the 295 layers of components that compose the pouch-type LIB cell. The mechanical model considers both geometric and material nonlinearities, and to consider material nonlinearities, the hardening due to the strain-rate effect, anisotropy, was applied for the electrode and separator. The electrochemical model calculates the heat generation by connecting each layer with Randles circuits, and the thermal model calculates the temperature distribution by electrochemical heat generation. The two-way coupled method of the three models predicted well the process of mechanical deformation, internal short circuit due to breakage of the separator, and subsequent thermal runaway of the pouch-type LIB cell. Comparing the experimental results with the predicted values under spherical punch indentation conditions, the error was within 3.3% at the time of internal short circuit and peak temperature due to thermal runaway, respectively.