基于气体特性的锂离子电池热失控在线预警方法

Thermal Runaway Online Warning Method for Lithium-ion Battery Based on Gas Characteristics

热失控是锂离子电池最严重的故障,尚缺乏有效的在线预警方法。热失控触发前,锂离子电池析出多种气体,依据气体的析出特性对热失控实现在线预警。首先,分析了锂离子电池热失控析气机理,以确定析出气体的种类。然后,搭建平台开展实验,研究了不同荷电状态(state of charge,SOC)锂离子电池气体在热失控触发前的析出特性。进一步地,基于挥发性有机物(volatile organic compounds,VOC),提出了适用于不同SOC锂离子电池的热失控在线预警方法。最后,实验验证了所提方法的正确性,结果证明所提方法预警的快速性显著优于常规方法。热失控触发前的气体特性研究表明:不同SOC下,二氧化碳(CO_(2))、一氧化碳(CO)、甲烷(CH_(4))、氟乙烷(C_(2)H_(5)F)和VOC均有析出,当SOC高于10%时,氢气(H_(2))才会析出;随着SOC增大,VOC和H_(2)体积分数不断增加,而CO体积分数先增加后降低,此外CH_(4)和C_(2)H_(5)F体积分数没有表现出明显变化;相比于CO_(2)、CO、H_(2)、CH_(4)和C_(2)H_(5)F,VOC析出时间最早,体积分数仅次于CO_(2)。该文成果可为锂离子电池热失控预警技术研究提供重要参考。

Thermal runaway is the most serious faults of lithium-ion battery,and there is still no effective method for on-line warning.Before the occurrence of the thermal runaway,a variety of gases of lithium-ion battery will separate out.According to the gas characteristics,the online warning of thermal runaway can be achieved.Firstly,the gas mechanism of the thermal runaway of lithium-ion battery is analyzed,thus the species of gas is determined.Subsequently,experiments are carried out based on the established platform to study the gas characteristics of the lithium-ion battery with different state-of-charge(SOC)before thermal runaway.Furthermore,based on volatile organic compounds(VOC),an online warning thermal runaway method is proposed for the lithium-ion battery with different SOC.Finally,the correctness of the proposed method is verified experimentally,and the results show that the warning quickness of the proposed method is significantly superior to that of conventional method.The studies on the gas characteristics before thermal runaway occurrence show that:(1)Carbon dioxide CO_(2),carbon monoxide CO,methane CH_(4),ethyl fluoride C_(2)H_(5)F and VOC are released at different SOC,while hydrogen H_(2)is released when the SOC is higher than 10%;(2)With the increase of SOC,the volume fractions of VOC and H_(2)continuously increase,while the volume fractions of CO first increases and then decreases,moreover,the volume fractions of CH_(4)and C_(2)H_(5)F show no obvious changes;(3)Compared with CO_(2),CO,H_(2),CH_(4)and C_(2)H_(5)F,VOC have the earliest releasedand the relatively high volume fractions are second to the fraction of CO_(2).This work can provide important references for the research on the thermal runaway warning technology of lithium-ion battery.