Computational Investigation on Radiation Induced Li-Ion Battery Thermal Runaway

With the global trend of electrification and the fast expansion of electrical vehicle market, research and development of Li-ion battery as main energy storage medium has attracted extensive interest. One of the key issues that need to be resolved is thermal runaway and its propagation, where side reactions can occur when the battery is exposed to heat and other abuse conditions. Thermal runaway reactions are largely exothermic and can lead to subsequent fire and explosions when thermal runaway propagates to adjacent cells. In the current work, we focus on the effect of radiation on thermal runaway, which is especially relevant when a battery is exposed to adjacent heat and fire sources. To validate the numerical simulation, calculated radiation heat flux is compared with analytical solutions of radiation heat flux based on view factor expressions obtained in simple 2D cylinder-to-cylinder geometries. Very good agreement has justified the validity of the radiation calculation. Furthermore, radiation induced thermal runaway is evaluated between two cylindrical 18650 batteries. It has shown that depending on the temperature of the triggering cell, thermal runaway can either be triggered in the region close to the cell surface or internal domain within the cell, with different roles of the pre-runaway chemistry. Integrated radiation heat flux is calculated under a wide range of triggering temperatures, showing different limits under low and high temperature conditions. By analyzing the pre-runaway chemical heat release, it is further seen that radiation plays a dominant role under higher temperature conditions, while its significance gradually decreases under lower temperature conditions. Results from this work evaluate the role of radiation in thermal runaway propagation and provide useful insights into the thermal runaway control.