Thermal propagation model and numerical simulation of high-specific energy lithium-ion battery packs induced by the spatio-temporal dispersion of multiple heat sources

Abstract

Thermal abuse serve as a direct trigger for thermal runaway in lithium-ion batteries. In this paper, we propose a numerical model of thermal propagation that incorporates partial differential equations for heat transfer, ordinary differential equations, fluid heat transfer and thermal radiation. A high-specific-energy battery pack comprising square lithium-ion cells is established, and the thermal runaway propagation process within this pack is explored using the finite element method. To simulate the thermal runaway propagation phenomenon induced by spatio-temporal dispersive heat sources, a thermal propagation model is constructed. Compared to the convection-only model, the proposed model exhibits a difference of 40 K in peak temperature and 65 s in thermal spreading time. Similarly, when compared to the thermal radiation-only model, the differences are 120 K and 60 s, respectively. Furthermore, the thermal propagation characteristics of the battery module under three different gaps are analyzed, revealing that increasing the battery gap slows down the thermal propagation time and peak thermal runaway temperature of the cell but reduces the energy density of the battery pack. A multi-indicator comprehensive evaluation system is established based on this model to assess the thermal runaway propagation hazard index. This study provides practical guidance for the design of battery thermal management systems.