A modeling approach for lithium-ion battery thermal runaway from the perspective of separator shrinkage characteristics

The safety concerns triggered by thermal runaway (TR) are the major obstacle to the large-scale commercialization of lithium-ion batteries (LIBs). In essence, TR is an electrical-thermal coupling process involving the interaction between internal short circuits (ISC) and exothermic reactions. Nevertheless, most existing models primarily focus on exothermic decomposition reactions and temperature prediction during TR, while overlooking the modeling of ISC behavior from a mechanistic perspective. This paper proposes a novel modeling approach that defines the ISC state of the battery through the degree of separator shrinkage. Firstly, differential scanning calorimeter (DSC) experiments are performed on the separator to ascertain its thermal shrinkage characteristics. Following this, a shrinkage function is constructed to quantitatively describe the thermal shrinkage of the separator. Subsequently, the ISC conductivity as a function of separator shrinkage degree is integrated into the electrical-thermal coupling model. Consequently, the model can quantitatively assess ISC behavior resulting from separator shrinkage or melting. The average relative error of the model for voltage and temperature prediction is 0.57 % and 1.8 %, respectively. This indicates that the model can accurately capture the electrical-thermal coupling characteristics and ISC state of LIBs. This work presents a novel perspective on the mechanism research of TR and model-based TR warning.