Experimental study on the impact of safety valve venting pressure on thermal runaway in large-format lithium iron phosphate battery

Thermal runaway (TR) of large-format lithium iron phosphate (LFP) batteries has become a critical technical issue due to its potential to cause extensive fire incidents. The safety valve (SV) plays an important role that it enables gases generated inside the battery to release promptly, thereby delaying the onset of TR (T_TR). However, the impact of the initial setting venting pressure of the safety valve (P_sv) on the TR behavior of lithium-ion batteries (LIBs) and the severity of the associated hazards remain unclear. To address this, this study investigates the TR behavior and associated risks of LFP batteries with different P_sv under thermal abuse conditions. The results indicate that LFP batteries without SV experience combustion during TR, significantly increasing the hazard. With increasing P_sv, the maximum temperature (T_max) and peak rate of temperature rise (dT/dt)_max during TR decrease gradually. Finally, a TR assessment model is employed to evaluate the hazards of LFP batteries under different P_sv. Batteries without SV exhibit the highest TR hazards, whereas those with the P_sv of 0.35 MPa demonstrated the lowest hazards. However, higher P_sv results in the accumulation of higher peak pressures inside the battery, thereby increasing the risk of severe safety incidents. Therefore, the selection of the appropriate P_sv requires careful consideration of the battery's operational specifications and safety standards to achieve an optimal balance. This results can provide a more comprehensive theoretical and experimental basis for battery design and safety assessment by comparing battery responses under different P_sv conditions.