The effect of PCM on mitigating thermal runaway propagation in lithium-ion battery modules

Abstract

The main safety issue of lithium-ion batteries (LIBs) is thermal runaway (TR), which has greatly hindered the application of LIBs. Phase change materials (PCM) have been used in battery modules as a thermal management method due to the heat absorption function during the phase change process. However, the role of PCM in TR propagation mitigation has not been carefully examined. In this paper, a 1D heat transfer model was developed to predict the mitigation effect of PCM on TR propagation of a battery array, which shows the superiority of high simulation speed and accuracy. The effects of thermo-physical parameters of PCM on cascading cell-to-cell thermal runaway propagation behavior were investigated. In addition, we gave an optimal range of key parameters of PCM based on safe regulations of China and the United Nations regarding to the TR in electric vehicle LIBs. It was found that the latent heat, density and heat capacity of PCM have similar effects on TR propagation behavior. With the increase of the three PCM parameters, the time duration between cell-to-cell failure propagation increases linearly, which shows a slower TR propagation rate. The optimal ranges for density, heat capacity and latent heat of PCM are over 2150 kg·m−3, over 4100 J·kg−1·K−1 and over 9 × 105 J·kg−1, respectively. What’s more, the TR propagation will exacerbate with the increase of thermal conductivity of PCM, which reminds us to notice a balance between thermal management and TR mitigation in PCM-based thermal management system. Generally, through analyzing the effect of thermal diffusivity of PCM in TR inhibition, we found higher thermal diffusivity will speed up the propagation of TR. And the TR propagation speed is more sensitive to the change of density of PCM. The thermal diffusivity of PCM should be less than 9 × 10−7 m2·s−1 to satisfy the safety standards. The PCM manifests great performance in retarding TR propagation with the phase transition temperature in the range from 318.15 to 518.15 K. Moreover, we found that there exists a critical PCM thickness over which TR propagation will not occur. As the battery thickness increases from 8.8 to 56.5 mm, the critical PCM thickness shows a non-monotonic variation trend (increasing at first and decreasing later). This study demonstrates the feasibility of using PCM as a thermal runaway mitigation strategy and provides a guideline for the optimization of physical parameters of PCM.