Characterization of the deflagration behavior of the lithium-ion battery module within a confined space under different ventilation conditions

Lithium-ion batteries (LIBs) have been widely used in the modern society, such as electric vehicle and energy storage system. The most common application scenario of LIB is in the confined space. LIBs were prone to release flammable gases (such as carbon monoxide, hydrogen, and hydrocarbons) under abuse conditions, and the gas accumulation deflagrated with catastrophic power especially in the confined space. The ventilation condition and cathode materials of the LIB influence the destructive power of deflagration. In this study, thermal runaway (TR) tests on the Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) and Li(Ni0.6Co0.2Mn0.2)O2 (NCM622) cells with different states of charge (SOCs) were conducted in a confined box under different ventilation conditions. The location of peak pressure, gas temperature, deflagration pressure, and the effects of ventilation were analyzed. Based on the measured values of the pressure at different locations, the peak pressure was generally located at the top of the confined space. The gas temperature and pressure of NCM811 batteries were generally higher than those of NCM622 batteries. NCM811 cells not only had a lower trigger temperature of thermal runaway (TR), but also a high destructive power of deflagration. The impact of ventilation condition on deflagration was studied, and the result of dimensionless analysis indicated that the deflagration pressure was influenced by opening factor, explosion gas volume, explosion heat, and explosion temperature. With the increasing of the opening angle of the window, the peak deflagration pressure firstly increased (from 30° to 60°) then decreased, indicating that there was an competitive mechanism between the combustion and pressure relief with the improvement of ventilation condition. This work helps us understand the hazards of LIB deflagration under different ventilation conditions and provides a reference for ventilation design in battery application scenarios which ensure the process safety through fire protection design.