Study On Fire Characteristics Of Typical Lithium Batteries

In recent years,new energy vehicle fires have occurred frequently.Among the new energy vehicles,battery electric vehicles have the highest number of possessions.As the core component of battery electric vehicles,lithium-ion battery is an important cause of fire.In order to deeply explore the fire hazard of lithium-ion batteries and grasp their fire characteristics,three common lithium-ion batteries on the market:ternary lithium-ion batteries,mixed Li Mn₂O₄ batteries and Li Fe PO₄（LFP）batteries were selected as the research objects.Experiments have conducts through the self-designed lithium-ion battery combustion experimental platform.The main research results were as follows:First,research on the law of combustion characteristics of lithium-ion batteries.The four aspects of combustion phenomenon,flame height,surface temperature when the battery is sprayed,and temperature above the vertical line were studied.It was found that the ternary lithium-ion battery had the most highest fire risk,and the LFP battery had the lowest fire risk.The higher the thermal radiation intensity,the greater the SOC and the capacity,the more violent the combustion phenomenon.The surface temperature of the ternary lithium-ion battery and the mixed Li Mn₂O₄battery was basically greater than 200°C when sprayed,and has a positive correlation with SOC and capacity.The temperature change above the vertical line of the battery was greatly affected by the flame.Second,research on the quality change law of lithium-ion battery.The three aspects of the mass before and after fire,the proportion of mass loss,and the mass change curve during the heating process of the three lithium-ion batteries were studied.It was found that the proportion of mass loss of lithium-ion batteries with different reaction severities was quite different,and the mass loss was affected by SOC,capacity and thermal radiation intensity.When the battery reacted violently,its mass change curve could divided into three distinct sections,and when the battery only released smoke,its mass change curve was more gentle.Third,research on the law of smoke concentration changes of lithium-ion batteries.The concentration changes of CO,CO₂,SO₂ and HF were studied respectively,and the concentration increment ratio of CO₂ and CO under different working conditions were discussed.It was found that the gas concentration released by the ternary lithium-ion batteries was the largest.Most batteries have two concentration peaks of HF.The change of gas concentration was affected by SOC,capacity and thermal radiation intensity,showing a positive correlation.The concentration increment ratio of CO₂ and CO was affected by thermal radiation intensity,and had a positive correlation with thermal radiation intensity.The fire characteristics of three typical lithium-ion batteries are obtained by experimental means,which can provide a reference for the research of battery electric vehicles fire and has important practical value.70 figures,37 tables,and 92 references.