Experimental investigation on intermittent spray cooling and toxic hazards of lithium-ion battery thermal runaway

Abstract

The fire extinguishing and cooling of lithium-ion battery thermal runaway have attracted significant research attention. In this study, an intermittent spray method for cooling lithium-ion battery during thermal runaway is proposed. The internal temperature and voltage of the battery, as well as the gases generated during thermal runaway are investigated. In addition, the extinguishing and cooling ability of the intermittent spray method at different intermittent periods (cycle consisting of a spray time and an interval time) and duty cycles (the percentage of the pulse duration occupied in a cycle) are compared and discussed. Furthermore, the toxic effects of the generated gases are evaluated. Experimental results reveal that the internal temperature of the battery is significantly higher than the surface temperature during the thermal runaway. Particularly, the internal temperature of the cell with 100% state of charge was as high as approximately 1000 ℃. In addition, the surface temperature of the cell may rebound after cooling owing to the insufficient heat transfer and a large radial temperature gradient of the battery. Furthermore, intermittent spray with more spray pulses of shorter duration performs better cooling effect. Particularly, the cooling effect initially increases, and then decreases with decreasing duty cycle. The major toxic gases produced during thermal runaway are CO and HF, whose yield increases with an increase in the state of charge, and the toxicity of these gases increases after the water spray. The findings of this study indicate that strict safety protection is needed when water spray is used to extinguish LIB fires.