Study on thermal runaway and cascade propagation characteristics of lithium iron phosphate batteries

ZHU Guoqing; CUI Shaoqi; HU Xiangyu; WANG Xinyu; WANG Wei

doi:10.13247/j.cnki.jcumt.20250316

Abstract：Thermal runaway and the cascading propagation pose a core challenge limiting the large-scale safe application of lithium-ion batteries.Focused on 100 Ah LiFePO4 batteries,their thermal runaway evolution and kinetic propagation characteristics was systematically investigated by con-structing a multi-cell module experimental platform.The results show that the thermal runaway process is divided into four stages:self-heating with battery micro-expansion,pressure accumula-tion and activation of the safety valve,thermal runaway explosion and recession.Notably,the mu-tation point of expansion force precedes the earliest detectable temperature signal by up to 476 s,providing a critical criterion for ultra-early warning.Furthermore,thermal runaway propagation ex-hibits a hierarchical"thermal hysteresis-burst"characteristic.The first three batteries form the ba-sic propagation unit,while the third cell acts as the initial propagation barrier due to accumulated thermal resistance.The fourth cell transforms into an energy hub through preheating and transient thermal shock,driving the reconstruction of propagation pathways.Based on this mechanism,a graded blocking strategy is proposed:A material cooling layer can be installed between the second and third cells to reinforce the thermal resistance barrier,with an integrated liquid cooling structure between the third and fourth cells to mitigate the acceleration effect of the energy hub.This study reveals the nonlinear dynamics of thermal runaway propagation,providing theoretical and technical foundations for inherent safety design in electric vehicles and energy storage systems.