Size effect on thermal runaway propagation in lithium-ion batteries: quantitative impact of size factor and suppression strategy

The continuous increase in the size of lithium-ion batteries significantly elevates the risk of thermal runaway propagation (TRP). Existing research has predominantly focused on specific, fixed cell formats, leaving both the mechanistic understanding of size effects on TRP incomplete and empirical mitigation strategies lacking cross-format scalability. Through combined experimental and modeling approaches, we systematically investigate the influence of battery size on TRP evolution characteristics. Furthermore, a system-level design response surface mapping the size factor ( F ) against the critical thermal insulation thickness is proposed. The results demonstrate a clear positive correlation between the F and the peak heat transfer power during TRP. Relying solely on adjusting the battery size proves insufficient for effectively inhibiting the TRP of Li(Ni x Co y Mn z )O 2 (NCM) batteries. This quantitative framework minimizes development trial-and-error costs by guiding the geometric optimization of large-capacity single cells and the a priori thermal sizing for system design.