Detailed modeling investigation of thermal runaway pathways of a lithium iron phosphate battery

Abstract

This study investigates the thermal runaway (TR) pathways of a lithium iron phosphate (LFP) battery to establish important considerations for its operation and design. A multiphysics TR model was developed by accounting for several phenomena, such as the chemical reaction degradation of each component, thermodynamics, and aging. The parameters used in the model were experimentally optimized under two scenarios, and TR pathways were subsequently characterized under the electric and thermal abuse conditions. In the electric abuse condition, the onset time and peak temperature are important metrics representing TR hazards because they are strongly correlated with the TR pathways subjected to the heat balance between internal heat generation and heat exchange with the environment. The surface-to-volume ratio (S/V) was identified as the most important metric for ensuring thermal safety, as it results in delayed TR with higher S/V under the electric abuse condition and accelerated TR under the thermal abuse condition. From both operational and design perspectives, this contradiction should be carefully considered. Moreover, with regard to aging, TR pathways varied under the electric and thermal abuse conditions. Aging only affected the peak temperature of the TR pathways under the electric abuse condition, whereas it only altered the onset temperature of TR pathways under the thermal abuse condition. This difference can be attributed to the different heat sources and heat balance mechanisms. Thus, understanding the dependency of TR under the electric and thermal abuse conditions on aging and cooling is important for the optimal design of LFP cells with high thermal stability and for establishing novel thermal management strategies. This intensive investigation can contribute toward ensuring thermal stability and reliability of LFP batteries from various perspectives.