Study On Thermal Runaway And Propagation Characteristics Of Lithium Ion Battery After Seawater Immersion

With the popularization and rapid development of new energy vehicles,as one of the cores of new energy vehicles,the safety issue of power batteries has become a hot topic in the society.In the power battery safety test standard,seawater immersion is one of the important items of power battery safety test.Based on the immersion test,this paper conducted an experimental study on the thermal runaway and propagation characteristics of 18650 lithium-ion batteries（Samsung,ICR 18650–26 FM）after immersion for different times.The results are summarized as follows:The thermal runaway characteristics of the single battery after immersion different time indicate that the safety valve plays a key role in the safety of the battery.For 100%SOC and 50%SOC,when the immersion time exceeds 3 h,the safety valve will be corroded,the ignition time of the battery is shortened,the peak heat release rate and the total combustion heat increase,but as the immersion time further increases,the ignition time gradually increases.The heat release rate peak and total heat release of the 100%SOC reached the maximum when the immersion time is 3 h,while the total mass loss,CO and SO₂ during thermal runaway gradually decreased with the increase of the immersion time.All batteries of 0%SOC fail to be ignited.The thermal runaway propagation characteristics of the battery will be influenced seriously by the immersion time.For 100%SOC,the average propagation time of thermal runaway increases first and then stabilizes with the increase of immersion time,and reaches the maximum value when the immersion time is 3 h.The experimental results show that the average propagation time of thermal runaway is mainly related to the proportion of temperature rise caused by fire propagation,which depends on the heating efficiency of the flame.The total mass loss during thermal runaway propagation remained basically constant when the immersion time exceeds 3h,and the heat release rate show little correlation with the thermal runaway propagation rate.