HE Yilong, WANG Yan, ZHANG Zhaozhi, DAI Feng
This study investigated the thermal runaway (TR) behavior and environmental impact of large-capacity prismatic NCM622 lithium-ion battery modules within a confined space. The experiments were performed on a module of three parallel-connected batteries (Bat01, Bat02, Bat03) in a 1.885 m3 sealed constant-volume pressure chamber, utilizing lateral heating (550 W) to trigger thermal runaway. Using multi-parameter sensors, the temperature evolution, thermal propagation, chamber environment, and mass loss were systematically characterized. The results reveal distinct thermal runaway behaviors: Bat01 and Bat02 exhibit a two-stage process, characterized by two violent ejections separated by a plateau, lasting 67 and 95 s, respectively, while Bat03 undergoes a single dominant thermal runaway process lasting 80 s. Thermal propagation rates are recorded at 1.72, 1.09, and 1.94 mm/s, with peak temperature rise rates of 94, 32.1, and 46 ℃/s, respectively. The chamber environment reaches peak parameters at approximately 260 s, with a maximum temperature of 262.8 ℃, pressure of 299.2 kPa, and total substance amount of 70.91 mol. Corresponding mass loss rates for the three batteries are 29.42%, 29.65%, and 27.13%. Energy flow decoupling analysis reveals that inter-cell contact heat conduction is the primary driver of thermal propagation, with a power contribution significantly outweighing that of convective heat transfer. During the triggering phase, external heating accounts for merely 26% of the total energy input, whereas heat transfer from preceding to subsequent cells dominates the cascading failure phase. These quantitative findings confirm that interrupting “solid-solid” thermal bridges is more critical for module safety design than enhancing environmental heat dissipation. These findings provide essential data and theoretical insights for thermal runaway warning systems, safety design, and risk assessment in battery modules.
