Microemulsion fire extinguishing agent for lithium ion battery: Preparation, characterization and application

Clean and efficient lithium-ion battery (LIBs) fire extinguishing agents are urgently needed for energy storage systems (ESS). In this work, a microemulsion was prepared by titration and its inhibition effect on the thermal runaway (TR) of a 52 Ah LiFePO₄ LIBs was investigated. The surfactants most suitable for use as fire extinguishing agents for LIBs were screened based on surface tension, electrical conductivity, gas absorption capacity, and cost. The effects of the surfactant/cosurfactant ratio (K_m) on the phase behavior, particle size and physical properties of the solution were investigated. Finally, the formula of microemulsion system containing maximum functional additive content was determined. The suppression effect of the fire extinguishing agent was evaluated by measuring the temperature at different measurement points of the battery, the cooling rate during the release of the fire extinguishing agent, the maximum temperature, and the absorption capacity of H₂ and CO. The results show that microemulsion can play physical and chemical roles in the suppression process, and its fire extinguishing effect is better than that of pure water mist, and the cooling rate is 1.33 times that of fine water mist. Through the synergistic action of surfactant and cosurfactant, the surface tension and droplet size of the fog field are reduced, and the heat absorption and cooling capacity of the fog field are enhanced. In addition, when extinguishing the fire, the functional additive wrapped in the liquid drop is released, capturing the H[rad] and OH[rad] free radicals released in the fire site, improving the fire extinguishing efficiency. In terms of gas absorption, the addition of surfactant improves the solubility of H₂ and CO. The preparation microemulsion provides a new reference for the safety design of LIBs.