Investigation on combustion characteristics and suppression mechanism of thermal runaway venting gas of lithium iron phosphate batteries in discharge-heating coupling

Lithium iron phosphate (LFP) batteries are widely used in energy storage systems and commercial vehicles due to high safety, cycle life and stability. However, the LFP batteries remain susceptible to thermal runaway (TR) under extreme conditions. In this work, 25 Ah LFP cells were employed to investigate the coupled effects of discharge and external heating on TR behavior and gas generation. Furthermore, the effects of different suppressants on TR venting gas combined with electrolyte solvent combustion were analyzed using CHEMKIN. The results show that at 100% SOC, the cell exhibits the maximum temperature (361 °C) and the shortest triggering time (447 s), the highest proportion of H₂ (60.4%), indicating a most explosion risk. Among the suppressants, trimethyl phosphate (TMP) demonstrates the most effective suppression, reducing flame temperature, laminar flame velocity, and net heat production by 32.6%, 97.5%, and 99.5%, respectively. In contrast, heptafluoropropane (FM200) and perfluorohexanone (Novec-1230) show weaker inhibition and produce HF as a by-product. This study provides both theoretical and experimental insights into TR mitigation and supports the development of efficient and environmentally friendly flame extinguishing agent for LFP batteries.