Multi-objective optimization of side plates in a large format battery module to mitigate thermal runaway propagation

• An optimization method is employed to design side plates for a battery module. • Thermal safety and energy density of a battery module are effectively improved. • Average thermal runaway propagation time interval is prolonged by 46.0%. • Lightweight of a battery module with side plates fulfilled with a 59.6% mass decrease. • Effect of aggravating heat transfer through side plates is significantly weakened. Thermal runaway propagation in battery systems seriously hinders the rapid development of electric vehicles. Side plates are commonly employed to ensure the rigidity of the battery system, which can considerably affect the propagation behaviors. However, little attention has been focused on optimizing the design of side plates to mitigate the failure propagation from the perspective of weakening heat transfer. In this study, an orthogonal experimental design was applied to investigate the effects of the thickness, height and convective heat transfer coefficient of side plates, and the thickness of thermal insulating slices on regulating propagation behaviors. The results show that the height of the side plates is the most significant factor in the propagation process. Furthermore, a multi-objective optimization method based on a verified approximate model was proposed to design lightweight side plates with thermal safety. The Pareto frontier among the optimal objectives was obtained by using Non-dominated Sorting Genetic Algorithm II. The average propagation time interval is effectively prolonged by 46.0% after multi-objective optimization. Moreover, the mass of the side plates is decreased by 59.6%, resulting in a lightweight battery module. The local hot pot (battery failure point) first reaching the triggering temperature of the thermal runaway moves from both sides of the battery module to the center of the batteries. This study creatively presents the multi-objective optimization of side plates in a battery module to mitigate thermal runaway propagation. The results can provide valuable guidelines for the safety design of battery modules.