Investigation on the explosion dynamics of large-format lithium-ion pouch cells

Explosion is the most extreme case of thermal runaway of lithium-ion (Li-ion) batteries. In this study, explosion dynamics of large-format Li-ion cells are investigated experimentally and numerically. Overcharge-to-explosion tests are conducted on 40 Ah Li-ion cells with Li[Ni0.8Co0.1Mn0.1]O2 cathode. Based on the explosion physics, shockwave and detonation models are used to characterize the shock effect of the cell explosion and evaluate the explosion equivalent. Von Neumann peak is observed on the pressure curves, and the shockwave velocity is supersonic at this time; the unwrinkled spherical flame phenomenon observed in the experiment indicates that it is detonation. Additionally, a geometric model is established based on the real testing scenario, and the explosion behavior is numerically studied. The characteristics of the explosion dynamics process are interpreted and the propagation mechanism of the shockwave are revealed; the deflagration to detonation transition (DDT) phe-nomenon in this process is caused by the formation of hot spots, and the explosion of the cells eventually turns into stable combustion. This study fills the gap in the research on thermal runaway of Li-ion cells, especially in the extreme cases of fire and explosion, and provide useful guidance for battery safety.

Automated summary

This study investigates the explosion dynamics of large-format Li-ion cells through experimental and numerical research. Overcharge-to-explosion tests on 40 Ah Li-ion cells reveal the presence of Von Neumann peaks on pressure curves, indicating supersonic shockwave velocity, and the experiment confirms detonation instead of deflagration. Furthermore, a geometric model is established to study the explosion behavior numerically, revealing the propagation mechanism of the shockwave. This study fills the research gap on thermal runaway of Li-ion cells, especially in extreme cases like fire and explosion, and provides valuable guidance for battery safety.