In situ extinguishing mechanism and performance of self-portable microcapsule fire extinguishing agent for lithium-ion batteries

The thermal runaway of lithium-ion batteries is characterized by high temperature rising rate and heat release rate, leading to rapid and violent development of battery fire disasters. External untimely firefighting measures can hardly deal with the rapidly evolving lithium-ion battery fire. The widely used cell-module-pack combination packaging system further exacerbates the risk of thermal runaway propagation, as the external extinguishing agent cannot effectively reach the fire area due to the barrier of the packaging structure. To address these challenges, an in situ extinguishing strategy based on self-portable microcapsule fire extinguishing agent for lithium-ion batteries has been proposed. Microcapsule is a new type of fire extinguishing agent with ureaformaldehyde resin as shell, dodecafluoro-2-methylpentan-3-one (C6F12O) and 1,1,1,2,2,3,3,4,4-nonafluoro-4methoxybutane (C5H3F9O) as composite core, directly coated on the outer surface of the battery. During the thermal runaway process, a large amount of heat leads to increased internal pressure of microcapsule, resulting in the cracking of the polymer shell and released fire extinguishing agents for in situ fire suppression and cooling. It was found that this in-situ fire-suppressing technology can effectively inhibit the flame of the ternary Li-ion battery (NCM18650) and control the temperature below 130 degrees C. Moreover, this in-situ fire-extinguishing strategy can automatically detect and response at the early stage of battery thermal runaway, directly acting on the faulty cell inside the packaging and effectively inhibit the formation and propagation of thermal runaway. These findings provide a novel solution to the safety problems caused by large-scale application of lithium-ion batteries.