锂离子电池过充行为实验研究

Study on overcharge behavior of Li-ion batteries by experiment

过充电是造成锂离子电池系统热失控的主要原因之一,研究锂离子电池过充前后的性能参数变化规律是实现电池热失控及时预警的基础。以方壳磷酸铁锂(LFP/GC)电池为研究对象,研究了电池过充至不同截止电压后的外特性参数变化规律,并定性评估其热失控风险。结果表明,锂离子电池过充后电化学极化内阻变化明显,与电池过充程度紧密关联,过充至4.5 V时急剧增大至初始值6倍,同时电池内部压力也随过充而增加。电池过充后,检测到电池直流内阻分量和膨胀压力的明显变化,可以将其作为判断过充是否严重的重要依据,研究成果可以为电池管理系统(BMS)和能量管理系统(EMS)特征参数的选取提供参考,作为电池系统风险预警和安全监控的重要依据。

Overcharging is a main factor causing the thermal runaway of lithium ion battery(LIB).In order to develop an early warning strategy of thermal runaway,it’s crucial to study the variation law of performance parameters of lithium-ion battery before and after overcharge.The square aluminum shell LIBs with lithium iron phosphate(LFP)cathodes were overcharged to different voltages,the variation of battery parameters was experimentally investigated,and the thermal runaway behaviors were also qualitatively analyzed.The results show that the electrochemical polarization resistance changes remarkably after overcharging,while the overcharge voltage reaches to 4.5 V,the electrochemical polarization resistance shapely increases to sixfold of the initial value,and the pressure inside the shell accumulates quickly due to the side reactions.The direct current resistance and expansion pressure after overcharge change remarkably,which can be used as key characteristic parameters for indicating the overcharge behavior.The results can provide references for the selection of characteristic parameters of battery manage system(BMS)or energy manage system(EMS),and be used as important basis for risk warning and safety monitoring of LFP batteries.