Thermal runaway propagation characteristics of lithium-ion batteries with a non-uniform state of charge distribution

Alleviating and restraining thermal runaway (TR) of lithium-ion batteries is a critical issue in developing new energy vehicles. The battery state of charge (SoC) influence on TR is significant. This paper performs comprehensive modeling and analysis with the non-uniform distribution of SoCs at the module level. First, a numerical model is established and validated with experimental data to calculate the TR of the cells with different SoCs. Then, the influence of uniform and non-uniform SoC distribution on TR propagation is studied. The results show that the battery temperature, TR propagation time, and range are significantly affected by the total SoC of the battery module. When the total SoC is reduced below 30%, the energy released by the battery is significantly reduced, which is not enough to trigger the TR of all battery cells, and the TR propagation can be interrupted. Furthermore, the analysis of TR propagation in a battery model with non-uniform SoC distribution indicates that the propagation can be mitigated by reducing the SoC of two adjacent batteries on the spreading path. When the total SoC of adjacent cells is less than 55%, the TR propagation will be successfully inhibited.