Numerical investigation on thermal runaway propagation and prevention in cell-to-chassis lithium-ion battery system

The recently emerged cell-to-chassis (CTC) technology tremendously raises the energy density of the battery pack by directly integrating lithium-ion batteries into the chassis fame, while it also brings more safety concerns involving thermal runaway propagation (TRP). However, the TRP behavior and the relevant prevention measures for the CTC battery system have not been comprehensively studied yet. In this work, a three-dimensional model was developed within the framework of OpenFOAM to investigate the TRP behavior in CTC battery packs. The heat generation was described by the electrochemistry reaction kinetics fitted in stages and the heat balance was used to address the propagation of TR. This model captures the evolution process of TRP in CTC system and five typical heat transfer modes between the TR and normal cells are identified according to simulation results. The subsequent numerical study indicates that enhancing heat dissipation can reduce the demand on critical thickness of the thermal insulation layers to inhibit TRP. However, local failure of thermal insulation can initially lead to small-scale TR and further contribute to a larger heat accumulation, putting forward higher standards for critical parameters to cease TRP. As the thickness of insulting layers increases to 2 mm, TRP can be completely ceased even when local failure of insulation occurs. This work enhances the understanding of TRP mechanism and its prevention, which can serve as new guidelines for the safety protection of rapidly developing non-module battery pack technologies.

Automated summary

This study developed a three-dimensional model to investigate the thermal runaway propagation (TRP) behavior in cell-to-chassis (CTC) battery packs. It identified five typical heat transfer modes between the thermal runaway (TR) and normal cells and found that enhancing heat dissipation can reduce the thickness requirement of thermal insulation layers to inhibit TRP. However, local failure of insulation can lead to larger heat accumulation, requiring higher standards for critical parameters.