Response characteristics and sensitivity analysis of thermal runaway propagation parameters for LiFePO4 batteries under various pre-load forces

Amidst the rapid advancement of electric vehicles and energy storage systems, the thermal runaway (TR) has become a critical concern and a focal point for the industry. Although it has received significant attention and been extensively studied, the effect of pre-load force remains underexplored. This study emphasizes the impact of pre-load force by analyzing the response characteristics of key parameters during thermal runaway propagation (TRP) under various pre-load forces, and combining a quantitative assessment of pre-load sensitivity. It is found that pre-load force exacerbates thermal hazards and significantly affects the minimum rate of temperature rise and thermal accumulation, with sensitivities of 0.279 and 0.234. Conversely, it has a minor impact on the duration of TRP and total heat transfer, with sensitivities of 0.016 and 0.049, which indicates that pre-load force is not a key factor affecting the TRP process. In addition, the pre-load force can increase the gas production. However, once pre-load force exceeds 2.0 kN, a longer and more violent combustion process is triggered within the battery. This internal reaction consumes the flammable gases, resulting in a significant reduction of gas expulsion, thereby mitigating the gas hazard of TR. Furthermore, by examining the pre-load force sensitivity during TR for individual batteries, it can be deduced that with more than three batteries in the module, the impact of pre-load force for the fourth and subsequent batteries can be disregarded. This work lays a theoretical foundation for the assessment of battery performance and reliability analysis.