过充循环对锂离子电池老化及安全性影响

Effects of Overcharge Cycling on the Aging and Safety of Lithium Ion Batteries

由于电池组的不一致性以及充电装置的故障,锂离子电池在使用过程中会出现过度充电现象。为探究过充循环对电池老化及安全性影响,基于电化学阻抗谱法对锂离子电池在过充循环下的衰退过程和老化机理进行了定性与定量研究;对新旧锂离子电池进行了过充安全性测试。结果表明:相比于正常循环,过充循环会使电池容量快速下降,进而加速电池的老化,活性锂离子损失对电池老化影响最大,活性材料损失的影响处于中等水平,而电导率损失对容量衰减的影响较小。随着老化程度的加深,电池的稳定性与安全性变差。在92%SOH后,电池内部在过充测试中出现副反应,并使电池释放的能量大幅增长;79.6%SOH的老化电池最高温度比新鲜电池增长了68%,且实验后电池无法再次使用。电池活性锂离子损失与活性材料损失衰退是引发过充测试中副反应的最相关因素。实验结果可为电池设计和电池管理系统提供参考,以提高电池对过充电的耐受性以及安全性。

Because of the inconsistency of a battery pack and the fault of a charging device,lithium ion battery will be overcharged during use.In order to explore the influences of overcharge cycling on battery aging and safety,the degradation process and aging mechanism of lithium ion battery under overcharge cycling were studied qualitatively and quantitatively based on electrochemical impedance spectroscopy.In addition,the new and aged lithium ion batteries were overcharged for safety tests.The results show that,compared with the normal cycling,the overcharge cycling will lead to a rapid decline in battery capacity,which will accelerate the battery aging.The loss of lithium inventory has the greatest impact on battery aging,the loss of active material is at a medium level,while the conductivity loss has a negligible impact on capacity fading.As the aging degree deepens,the stability and safety of the battery become worse.After 92%SOH,side reactions occur in the battery during the overcharge tests,which greatly increases the energy released by the battery.The maximum temperature of aging batteries at 79.6%SOH is 68%higher than that of fresh battery,and the aged battery can not be reused after the experiment.The loss of lithium inventory and the loss of active material in batteries are the most correlated factors to cause side effects during overcharge tests.The experimental results can provide references for battery design and battery management system,so as to improve the battery’s tolerance to overcharging and safety.