Experimental Study on Microemulsion and Deionized Water for 4S4P Lithium-Ion Battery Pack Fires

Thermal runaway of lithium-ion batteries has always been a safety hazard in the field of electric vehicle and energy storage systems. An effective and feasible method is urgently needed to prevent or mitigate the risks caused by battery thermal runaway. Water mist is an effective means to suppress the thermal runaway of lithium ion batteries. This work studies and compares the suppression of deionized water mist and microemulsion water mist on the thermal runaway fire of lithium ion batteries. By adjusting the different positions of the nozzle, the fire extinguishing and cooling capacity of two fire extinguishing agents were revealed and compared. The results indicate that the position of the nozzle has a significant impact on battery pack fires. Under the condition that the extinguishing agent can completely cover the battery, the microemulsion extinguishing agent can quickly cool and extinguish the fire. Its cooling capacity is about 2.5 times that of deionized water, and the extinguishing time is only 1/10 of that of deionized water. The low surface tension of the microemulsion allows the liquid to be released with small droplets under high pressure, forming a dense barrier to isolate external oxygen and better penetrate into the battery pack. The additives in the microemulsion can effectively combine with the free radicals in the fire to quickly extinguish the flame.