Coupled Model for Heat Generation and Venting Gas in Lithium-ion Batteries during Thermal Runaway and Propagation

During the thermal runaway propagation of lithium-ion batteries, the coupling effects of substantial heat and gas generation significantly exacerbate thermal hazards. However, existing models mainly focus on internal heat generation within cells and overlook the influence of venting gas on thermal propagation, leading to limitations in evaluating thermal runaway at the battery pack level. This study develops a coupled model integrating heat generation dynamics with three-dimensional compressible venting gas flow to predict thermal runaway propagation in lithium-ion batteries. The model synchronizes a zero-dimensional thermal source term derived from adiabatic calorimetry data and mass flow rate from constant volume tank testing with high-fidelity gas dynamics simulations, resolving bidirectional thermal coupling between heat generation and ejected gas trajectories. Experimental validation through side heating of single cell at two different heating temperature confirms the model’s accuracy. Results demonstrate that increased heating temperature accelerates thermal runaway onset by approximately 400 s and increases gas production by 20%, with carbon monoxide, hydrogen, and carbon dioxide dominating vented gas composition. Simulations achieve less than 1% error in predicting failure timing and under 3% deviation in surface temperatures at directly heated zones. Then, single-cell model was extended to simulate a three-cell module subjected to side heating under both open and closed environmental conditions. Spatial confinement suppresses convective heat dissipation by 61% to 76% in downstream cells, shortening propagation intervals by 9.4% through accumulated high-temperature gas feedback. Comparing the energy flow in open and closed system, the high-temperature venting gas in closed system causes the environment temperature to rise quickly, suppressing the heat dissipation of subsequent batteries, and finally leading to the acceleration of thermal runaway propagation. This work establishes a validated tool for quantifying the propagation risks induced by confinement and optimizing venting strategies in battery safety design.