Coupled Effect of Multiple Environmental Conditions on Thermal Runaway Behavior of NMC and LFP Lithium-Ion Batteries: Storage Environment Optimization Based on Cooling Efficiency and Space Utilization Rate

Abstract

This work details a methodology that enables the characterization of thermal runaway behavior of lithium-ion batteries under different environmental conditions and the optimization of battery storage environment. Two types of widely-used lithium-ion batteries (NMC and LFP) were selected in this work. The coupled chemical and physical processes involved in the thermal runaway of lithium-ion batteries were simulated using a Multiphysics numerical solver. The developed model was verified against the data collected from the copper slug battery calorimetry (CSBC) experiment. Both the simulated and experimental results showed that the NMC battery with the state of charge (SOC) of 100% had the largest amount of heat generation compared to other cases. Additional simulations were conducted on this case to further quantify the combined effect of environmental factors (heating distance-d, ambient temperature-T_amb, and wind speed-v) on the thermal runaway behavior. The synergistic effect between v and d on mitigating thermal runway was found to be more significant than that between v and T_amb based on the calculated interaction coefficients. Furthermore, the settings of battery storage environment was optimized based on the defined space utilization rate α and cooling efficiency β. It was observed that at the same heating distance d, β reduced significantly with increasing wind speed. The scenario with d = 2 mm and v = 0.2 m s⁻¹ had the highest total efficiency and thus was considered to be the optimal design. The findings of this work enable a safer design of battery thermal runaway mitigation/prevention system under different storage environmental situations.