基于锂离子电池老化行为的析锂检测

Lithium Plating Identification from Degradation Behaviors of Lithium-Ion Cells

析锂会极大地影响锂离子电池的寿命和安全性,锂离子电池的析锂检测十分必要.本文根据锂离子电池的两种主要老化机理—SEI(Solid Electrolyte Interface)膜生长和析锂对老化行为上的不同影响,基于多应力作用下的锂离子电池循环老化实验结果,提出了两种检测析锂的方法,分别为内阻-容量轨迹法和阿伦尼乌斯准则法.两种方法的判定结果具有良好的一致性.之后,利用微分电压法区分了电池容量损失的不同来源,并进行了电池负极片EDS(Energy Dispersive Spectrometer)能谱分析,对析锂检测方法进行了验证.本文方法只需利用电池老化过程中可测的容量和内阻等电学量,判断方法简便,可实现非解体检测;同时,利用了单次循环的微量析锂在时间尺度上的累积,对析锂工况的辨识具有较高的敏感性.本文方法对锂离子电池的寿命加速测试、延寿使用、安全管理等具有重要意义.

Lithium plating has huge impact on the lifetime and safety of lithium-ion cells. It is, therefore, necessary to identify lithium plating. In this study, the accelerated stress tests of lithium-ion cells were conducted under different conditions with multi-stress loads. Based on the different effects of the two major aging mechanisms, namely, SEI（Solid Electrolyte Interface） layer growth and lithium plating, on the degradation behaviors, two lithium plating identification methods of resistance-capacity plot and Arrhenius plot were employed. The experimental results revealed that the two identification methods are highly consistent with each other. Furthermore, the origins of capacity loss were distinguished and the degradation mechanisms were investigated with the differential voltage analysis methods, while the cells were disassembled and the elemental compositions of the anodes were analyzed by energy dispersive spectroscopy（EDS）. The results verified the applicability of the two lithium plating identification methods. The advantages of the methods developed in this study are that the capacities and resistances of the cells at different aging cycles could be readily measured without dissembling the cell. In addition, these two methods are highly sensitive, as it allows the trace amount of plated lithium in a single cycle to be accumulated among numbers of cycles. The methods proposed in this study are of great significance to the accelerated stress test, durable use and safe operation of lithium-ion cells.