Abstract: This paper uses a self-built fire extinguishing experimental platform to select expandable vermiculite powder and vermiculite powder modified with MgCl2 and NaHCO3 for lithium-ion battery fire extinguishing experiments. And compared with ABC dry powder under the same working conditions, the fire extinguishing time, temperature rise suppression efficiency, reignition situation, and toxicity suppression of different fire extinguishing agents were analyzed. Fire extinguishing tests have shown that compared with ABC dry powder fire extinguishing agent, vermiculite powder can quickly reduce the surface temperature of the battery and effectively extinguish open flames, providing more uniform coverage and cooling effect. It has been confirmed that vermiculite powder can be used as a new type of fire extinguishing medium in lithium-ion battery fires, but the effectiveness of vermiculite powder is limited as it can reignite after extinguishing open flames. Compared with vermiculite powder, further modification treatment enhances the thermal stability and flame retardancy of modified vermiculite powder, reducing the possibility of reignition significantly. Especially, the MgCl2 vermiculite powder extinguishes the open flames and prevents reignition, which has a good fire extinguishing effect on ternary lithium-ion batteries.

Key words: vermiculite powder, modification, lithium-ion battery, thermal runaway, fire extinguishing effect