Enhancing extinguishing efficiency for lithium-ion battery fire: Investigating the extinguishing mechanism and surface/interfacial activity of F-500 microcapsule extinguishing agent

Due to the high flammability and combustion enthalpy, electrolyte solvents such as dimethyl carbonate (DMC) are regarded as the main fuel in combustion reactions for lithium-ion batteries (LIBs). Herein, to understand the combustion reaction kinetics of LIB fires and explore the efficient extinguishing agent, the chemical oxidation kinetics of DMC at 740–1160 K are studied through a jet-stirred reactor system coupled to the synchrotron vacuum ultraviolet photoionization mass spectrometry and GC. The major consumption path of DMC is the H-abstraction reaction of OH∙ and H∙ radicals. CH3∙ radicals produce to CH4, C2H4 and other common alkane gases in LIB fires through H-abstraction reactions and compound reaction. On this basis, the extinguishing mechanism of F-500 extinguishing agent for LIB fires is studied. The hydrophilic (-[CH2-CH2-O]5) and oleophilic ([C16H33]-) groups give F-500 molecules the amphiphilic characteristics of adsorbing on the solution surface and associating inside the solution to form micelles. Based on the results of dynamic light scattering and cryo-electron microscopy, the size and number of micelles continue to increase and the structure of micelles gradually changes from spherical to rod-shaped, which enhance the solubilization effect. F-500 can strengthen the extinguishing effectiveness of water mist by capturing and encapsulating the DMC inside the water to form "DMC-F-500-Water" microcapsule. DMC is dispersed in the water, which leads to the heat loss and the reduction of concentration and flammability. Moreover, the adsorption of F-500 molecules along the solid-liquid-gas three-phase contact line can reduce the interfacial tension of water and promote wetting process, which leads to the larger spreading area and speed of evaporation. During the application of the extinguishing agent, F-500 agent can improve the cooling efficiency of water. This work provides a reference for the design and development of novel extinguishing agent for LIB fires.