Abstract: Taking 18650 ternary lithium battery as the research object, this paper explores the characteristics of thermal runaway propagation of lithium battery, and then studies the effect and mechanism of inhibition of thermal runaway propagation by applying different types of additive water mist at different disaster times. The results show that the propagation of thermal runaway in the triangle-arranged battery module can be divided into three characteristic moments: thermal runaway initiation, thermal runaway peer layer propagation and thermal runaway interlayer propagation. Due to the preheating effect of the upper layer, the thermal runaway peer layer propagation is faster than the inter-layer propagation. At different disaster times, pure water mist, 1%CAB-35 water mist and 4%APG0810 water mist were applied respectively. It was found that the effect of water mist on restraining thermal runaway propagation of lithium battery was consistent with its cooling effect on single target battery. 4% APG0810 water mist can significantly reduce the maximum thermal runaway temperature of the target battery, and has the best effect on inhibiting thermal runaway propagation, which can inhibit thermal runaway propagation in the same layer and between layers. 1%CAB-35 water mist and pure water mist with no obvious thermal runaway cooling can inhibit the thermal runaway propagation between layers, but can not inhibit the thermal runaway propagation in the same layer. Through the solution performance test of different additives, it was found that the inhibition ability of 4% APG0810 water mist was significantly better than the other two, because 4% APG0810 has the lowest surface tension and contact angle, and its foaming property and foam stability are also the best. The combined effect of these effects improves the inhibition effect of thermal runaway propagation.

Key words: lithium battery module, thermal runaway propagation, water mist, additives, inhibitory effect