Immersion cooling enabled thermal runaway prevention in overcharged batteries: Mechanisms and metrics

Immersion cooling (IC) is an effective thermal management strategy for batteries. However, experimentally validation of its chemical compatibility and quantitative impacts on suppressing thermal runaway (TR) in large-capacity lithium‑iron-phosphate (LFP) batteries under overcharge conditions remains limited. In this study, we designed three cooling modes: fully immersed (FI), non-immersed safety valve (NISV), and non-immersed (NI). The experimental results indicate that the FI mode significantly suppresses TR by limiting both the maximum battery temperature and temperature rise rate. In particular, TR can be completely prevented at a 1/3 charging rate (C), with the maximum temperature limited to 110.45 °C and a minimal temperature rise rate of 0.15 °C/s. Furthermore, the FI mode enhances the battery release capacity by 35 %–40 % before the occurrence of internal short circuits (ISC) under the 1/3C overcharge condition, while limiting the voltage increase. However, this capacity-enhancement effect diminishes with an increase in the overcharge rates. Thermal profiling indicates that the FI mode exhibits superior heat dissipation, with significantly lower immersion liquid temperature and temperature rise rate when compared with the NISV mode. Safety evaluation with adoptable metrics further presents hazard scores of 0.206 for FI, 0.342 for NISV, and 0.955 for NI, indicating that IC technology significantly mitigates battery hazards, albeit with a more modest impact on TR risk. Additionally, the proposed hydrocarbon-based IC demonstrated promising chemical compatibility with the battery components (e.g., electrodes, electrolytes). This study highlights the safety benefits of IC technology for LFP batteries during overcharge and presents valuable guidelines for applications in electric vehicles and grid-scale energy storage systems.