Suppression of thermal runaway in lithium-ion battery modules using zonal variable flow immersion cooling

The temperature sensitivity of lithium-ion battery modules is well recognized, and the requirements under normal operation and extreme thermal runaway conditions cannot be simultaneously satisfied by conventional thermal management strategies. A baffle-assisted zonal variable-flow dynamic immersion cooling system is proposed in this study to optimize the internal flow field, eliminate low-velocity dead zones, enhance convective heat transfer, and realize demand-oriented cooling via differential inlet velocities in the upper and lower channels. A multi-physics coupling model calibrated and validated using single-cell discharge, ARC, and nail-penetration data is employed to evaluate the thermal management performance and numerically investigate thermal runaway propagation within an eight-cell module. Under 3C discharge, the module temperature difference is controlled within 2.4 °C. In the thermal runaway simulations, the average temperature of the triggered cell is maintained at approximately 270 °C, while the adjacent cells remain below 52 °C, indicating that thermal runaway propagation is suppressed under the investigated conditions. Stable thermal control is also numerically maintained during sudden thermal runaway under 2C-4C discharge, while effective thermal management is achieved under normal operating conditions. These results provide a practical reference for the design of high-safety and high-performance battery thermal management systems.