ABSTRACT The safety of electrolytes plays a pivotal role in determining the overall performance of lithium‐ion batteries, yet current safety evaluations focus mainly on the material level, overlooking behavior under practical battery operating conditions. Despite increasing recognition that the intrinsic flame retardancy of electrolytes does not directly translate into the overall fire resistance of lithium‐ion batteries, the mechanistic origins of this non‐equivalent relationship remain insufficiently understood. To bridge this knowledge gap, we systematically evaluate the fire behavior of pouch cells incorporating three representative flame‐retardant carbonate‐based electrolytes using cone calorimetry. Notably, flame retardants that perform exceptionally well at the electrolyte scale fail to yield meaningful improvements in battery‐level fire safety, whereas electrolytes with only moderate intrinsic retardancy can endow the full cell with nonflammability. Finite element simulations further clarify the fundamental disparities in combustion pathways between isolated electrolytes and full cells. These findings reveal the underlying causes of the indirect correlation between carbonate‐based electrolyte and cell‐level safety and advocate a paradigm shift from isolated component analyses to holistic, cell‐level safety strategies as the foundation for next‐generation inherently safe batteries.
Zhang et al. (2026) studied this question.