Thermal runaway characteristics and failure criticality of massive ternary Li-ion battery piles in low-pressure storage and transport

Thermal runaway is a major safety concern for Lithium-ion batteries in manufacture, storage, and transport. Facing the frequent incidents in the air transport of massive batteries, more reliable fire prediction and protection strategies under low-pressures conditions are urgently needed. Herein, thermal runaway criticality of the open-circuit cylindrical battery piles (up to 9 cells with 30% SOC) under a hot boundary is investigated inside a novel low-pressure chamber (20–100 kPa). Characteristics battery temperatures for the safety venting and thermal runaway are measured to analyze the influences of pressure and cell number on battery failures. Results indicate that lowering the pressure could promote an earlier and stronger safety venting and weaken the intensity of the exothermic reactions inside cells, which is verified by the surface morphology of the electrodes. The overall fire risk is higher with higher pressure and larger battery-pile size, as indicated by the lower minimum boundary temperature for thermal runaway (255 °C~385 °C). Moreover, a simplified heat transfer model is established to explain the trend of thermal-runaway criteria and the influence of the low-pressure environment. This work delivers new insights into the effects of pressure and pile size on battery thermal runaway, which can help to improve the safe storage and transport of large-scale lithium-ion battery piles under varied pressure conditions.