不同荷电状态下三元锂离子电池针刺热失控试验研究

Experimental study on the thermal runaway of ternary lithium-ion batteries under different charge

基于锂离子电池实际存储与应用的普遍性和危险性,利用自主设计并搭建的试验平台,分别对不同荷电状态(SOC)的锂离子电池进行了针刺热失控试验。利用直径5mm的钨钢针触发圆柱形21700三元锂离子电池热失控,记录其试验现象,测定锂离子电池的温度、开路电压与质量等参数。结果表明:锂离子电池SOC越高,针刺时发生热失控的现象越剧烈,且当锂离子电池SOC高于60%时,电池各测温点的最高温度都在电池正极处,电池外表面的温度峰值均高于电池内部的温度峰值;随针刺的锂离子电池SOC增大,电池各测温点温度峰值升高,电池正极处到达峰值所需时间变短;不同荷电状态的锂离子电池在进行针刺试验后,两端开路电压掉落的时间点不同,电池SOC越高,开路电压掉落的时间越快,在发生针刺后三元锂离子电池安全阀能保护电池不发生明显热失控现象的最大SOC在60%左右;SOC越高的锂离子电池在发生热失控过程中电池损坏越严重,其质量损失率越大。

To understand the damage of acupuncture to lithiumion batteries under different charge states and the severity of thermal runaway phenomenon,this experiment used the battery extrusion acupuncture test machine to carry out acupuncture experiments on five different charge states of ternary lithium-ion batteries,and measured the parameters such as the temperature of acupuncture point of lithium-ion batteries,the temperature inside of batteries,the temperature of positive and negative poles,the open-circuit voltage,and the quality before and after the experiment.The experimental results show that the higher the SOC of the lithium-ion battery is,the more violent the phenomenon of thermal runaway occurs during acupuncture.When the SOC of the lithium-ion battery is higher than 60%,the highest temperature of each point of the battery is at the positive pole of the battery,and the temperature peaks on the outer surface of the battery are higher than the temperature peaks inside the battery.With the increase of the SOC value of the lithium-ion battery,the temperature peaks on each point of the battery increase,and the time needed to reach the peak of the positive pole of the battery is shorter;the time point of the open-circuit voltage drop at both ends of the lithium-ion battery under different charge states is different after the acupuncture experiment:the higher the SOC value of the battery is,the faster the time of open circuit voltage falling.The maximum SOC value that the safety valve of the ternary lithium-ion battery can protect the battery from obvious thermal runaway after acupuncture is about 60%;the higher the SOC is,the more severe the battery damage and the greater the mass-loss rate is.