循环对锂离子电池外部短路安全性的影响

Impact of cycle life test on external short circuit safety performance of lithium ion batteries

锂离子电池安全性作为其应用于新能源汽车的关键技术指标,成为众多标准法规关注的重点,同时吸引了大量的科研工作者的参与研究。对一款软包三元锂离子电池在不同循环次数后的外部短路安全性进行了研究,发现随着循环次数的增加,电池外部短路测试的最大电流逐步下降;在800次循环内,外部短路测试中电池表面温升逐步降低,均低于125℃,未发生起火、爆炸等热失控现象,但是950次循环后,电池外部短路测试发生了热失控,温度达到360℃以上。通过直流放电电阻测试和交流阻抗谱测试,发现随着循环的进行电池阻抗逐步增大。

Safety of lithium ion battery is one of the most important technical indicators for its application in EVs and HEVs. So many standards take the safety performance as a necessary part to evaluate the batteries, and a lot of researchers pay much attention to the research of safety of lithium ion batteries. The external short circuit safety performance of lithium ion batteries during the life cycle tests was studied. It indicates that the maximum short circuit current and the maximum temperature of the batteries surface both drop gradually with the increase of cycle number before 800 cycles, and there＇s no thermal runaway. While thermal runaway happens in the external short circuit test after 950 cycles, and the maximum temperature reaches 360 ℃. It＇ s found that the impedance of the batteries increases gradually during the cycle tests by D.C. discharge resistance test and electrochemical impedance spectroscopy （EIS）.