Multi-objective optimization of hybrid battery thermal management design with considering thermal runaway propagation prevention

Maintaining lithium-ion batteries within an ideal temperature range and mitigating the risks of thermal runaway are crucial for electric vehicles. However, few studies have addressed both aspects of battery thermal management systems simultaneously. This study proposes a novel hybrid thermal management system that combines composite phase change material (CPCM) consisting of paraffin and expanded graphite (EG) with separated mini-channel plates, and explores its performance under normal and extreme conditions. The thermal runaway propagation (TRP) model and the electrochemical-thermal coupled model are developed to investigate the influence of CPCM on TRP and the thermal management performance at discharge, respectively. The critical distribution of CPCM thickness and the EG mass fraction for TRP prevention is obtained. The results show that the critical mass fraction increases with increasing thickness; two strategies for preventing TRP are identified: a low and a high mass EG fraction. Then, the single and interaction effects of the optimization variables on the maximum temperature, temperature difference, and pressure drop are analyzed at 2C discharge. Furthermore, a multi-objective optimization framework based on the surrogate model is constructed to optimize comprehensive thermal performance while satisfying the critical safety condition. Finally, the Pareto optimal solutions satisfying the critical safety condition are obtained through the multi-objective optimization algorithm. The optimized solution shows a 4.37% reduction in maximum temperature, a 2.07% reduction in temperature difference, and a 75.13% decrease in pump energy consumption compared to the original design. This work considers two scenarios in the optimization and the optimized results satisfy both requirements.