Modeling Li-ion Battery First Venting Events Before Thermal Runaway

Li-ion battery failure and thermal runaway usually follow gas venting events, which can be categorized into the first venting and thermal runaway venting. Since first venting events occur prior to thermal runaway, identifying the first venting event is essential for early detection of a battery failure. This study presents a model for CO2 gas generation at elevated temperature, which can be used to predict the occurrence of venting based on the buildup of cell internal pressure. The model considers the pressure of the generated gas and electrolyte vapor saturation pressure. To validate the model, an external short circuit (ESC) experiment is conducted for a nickel manganese cobalt (NMC) pouch cell that led to cell venting without thermal runaway. The model’s output can be used in conjunction with CO2 sensors and electro-mechanical cell measurements to detect first venting events, and hopefully estimate the probability of an upcoming thermal runaway based on the amount of CO2 released.