Experimental and numerical investigation on the effect of cell arrangement on thermal runaway propagation in air cooled cylindrical Li-ion battery modules

Given the increasing popularity of electric vehicles, it is crucial to deploy safe battery packs, as even minor flaws can lead to catastrophic accidents and thermal runaway (TR). In this study, the corner, center, and edge of the cylindrical (18650) surrogate cell module are the three failure positions used to experimentally investigate the cell-to-cell heat propagation in lithium-ion batteries. Subsequently, for varying cell arrangements (aligned, staggered, cross) and fault positions, the validated three-dimensional numerical model of the module is used to quantify the temperature responses of the first TR-prone cell surface sectors and the influence of different flow conditions, heat generation, and ambient temperatures on the TR initiation in terms of the rate of temperature rise and the TR onset time. The results reveal that an aligned arrangement with an edge fault position delays TR initiation under laminar flow, whereas a corner fault position delays it under turbulent flow. The staggered arrangement causes multiple TR onsets irrespective of the fault position. The aligned arrangement has the most TR initiation sites on the side of the first-TRP cell, whereas the staggered and cross arrangements have the most in front. The findings will aid electric vehicle on-board thermal safety battery module design.