Abstract: In order to investigate the retarding effect of water mist containing a nonionic surfactant on the thermal runaway phenomenon in lithium battery，this study focuses on optimizing the cooling and fire extinguishing performance of water mist by incorporating nonionic surfactants （FS 3100, Tween 80, APG 0810） into the water mist for 18650 ternary lithium?ion battery. The effects of different additives on the maximum temperature, average heating rate, average cooling rate, and cooling time of the lithium battery were compared and analyzed. Additionally, the cooling mechanism and reasons for negative inhibition were examined from the perspectives of surface tension, contact angle, and foaming properties. The results demonstrate that the three nonionic surfactants effectively enhance the capacity of water mist to suppress thermal runaway in lithium battery: FS 3100 < Tween 80 < APG 0810. APG 0810 primarily reduces the surface tension and contact angle of water mist to enhance the wettability and heat absorption capacity of water mist towards lithium battery. The main function of Tween 80 is to enhance foaming ability. The foam generated by Tween 80 exhibits low stability and brittleness, leading to significant heat dissipation during foam bursting and making it difficult for the foam to adhere to the surface of the battery. Consequently, this effectively improves the suppression of lithium battery heating rate during thermal runaway. Therefore, in order to enhance the retarding effect of water mist on the thermal runaway of lithium battery through the addition of nonionic surfactants, it is necessary to not only reduce surface tension but also appropriately increase the foaming multiple and the brittleness of the foam.

Key words: lithium?ion battery, thermal runaway, water mist, additive, cooling mechanism