磷酸铁锂动力电池寿命中期低温安全性能

以剩余容量84%的磷酸铁锂动力电池为样品,首先在25、0和-10℃充放电循环,然后对不同温度循环后的电池进行热安全实验(ARC实验),最后对不同温度循环后的电池进行拆解,通过X射线衍射(XRD)、扫描电子显微镜(SEM)进一步分析电池正负极材料的理化性能。实验结果表明,寿命中期的电池低温性能较差,电池在25、0和-10℃环境下,循环50周容量保持率分别为100%、93.5%和20%;寿命中期的电池低温循环后热安全性能降低,25、0和-10℃下循环后的电池热失控温度分别是165、157和108℃,低温循环使电池热失控温度提前;电池在低温循环过程中发生不可逆的电化学反应,负极极片表面产生锂枝晶,这是电池低温性能衰减和安全性能降低的主要原因。

Low-temperature safety performance of middle-life lithium iron phosphate batteries

Firstly,the lithium iron phosphate power batteries with the remaining capacity of 84％ were charged and discharged at 25,0 and-10 ℃.Second,the batteries performed the thermal safety experiment (ARC) at different temperatures.Finally,the batteries were disassembled after different temperature cycles.The physical and chemical properties of the positive and negative electrode materials were analyzed by X ray diffraction (XRD) and scanning electron microscopy (SEM).The results indicate that the low temperature performance of the batteries is poor,and the capacity retention rate is 100％,93.5％ and 20％ after 50 cycles,cycled at 25,0 and-10 ℃.Thermal safety performance of battery after low temperature cycling is reduced.The thermal incontrollable temperature of the batteries are 165,157 and 108 ℃ after 50 cycles,cycled at 25,0 and-10 ℃.In the process of low temperature cycling,the electrochemical reaction of the battery is irreversible.The surface of the cathode has the lithium dendrite,which is the main reason for the low temperature performance degradation and the safety performance degradation.