磷酸铁锂和三元锂电池外部过热条件下的热失控特性

Thermal runaway characteristics of LiFePO_(4) and ternary lithium batteries with external overheating

锂离子电池已广泛应用于储能和电动汽车中,但由于其易燃性,存在火灾和爆炸的风险。本文以单体40 A·h三元锂和72 A·h磷酸铁锂电池为对象,采用不同位置外部过热研究其热失控特性。实验结果表明磷酸铁锂电池在外部过热条件下不会引燃,而三元锂电池会自发引燃和喷射;侧面加热比底部加热能更早进入热失控;通过传热分析得到40 A·h三元锂电池热失控所需的单位受热面积导热量为1650~3788.76 kJ/m^(2),72 A·h磷酸铁锂离子热失控所需的单位受热面积导热量为3264.84~7856.67 kJ/m^(2)。以720 A·h磷酸铁锂电池组为对象,研究电池组燃烧蔓延特性,实验结果表明外部引燃后,若热源一直存在会蔓延至周围电池,持续发生喷射现象;通过传热分析得到相邻电池间的传热量为39.7~43 kJ。本研究结果可对储能电站火灾风险评估和锂电池火灾防护提供理论指导意义。

Lithium-ion batteries have been widely used in energy storage and electric vehicles,but there are risks of fire and explosion due to their flammability.This paper studied the thermal runaway characteristics of 40 A·h ternary lithium and 72 A·h LiFePO_(4) batteries by external overheating at different positions.The experimental results showed that the LiFePO_(4) battery does not ignite under the external overheating condition,but the ternary lithium battery ignited and sprayed spontaneously.The side heating can enter the thermal runaway faster than the bottom heating.From the heat transfer analysis,the heat conduction per unit heating area required for 40 A·h ternary lithium battery thermal runaway is 1650-3788.76 kJ/m^(2).The heat conduction per unit heating area of 72 A·h LiFePO_(4) battery is 3264.84-7856.67 kJ/m^(2).In addition,the combustion spread characteristics of the battery pack were studied,taking a 720 A·h LiFePO_(4) battery pack as the research object.The experimental results showed that if the heat source is in place till,after the external ignition,it spreads to the nearby battery and continues to spray.The heat transfer value of 39.7-43 kJ between the adjacent batteries is obtained from the heat transfer analysis.The results of this study can provide theoretical guidance for fire risk assessment of energy storage power stations and lithium battery fire protection.