锂离子蓄电池不同循环状态的过充行为

研究了额定容量720mAh铝塑膜包装的锂离子蓄电池过充安全性和充放电循环状态的关系。循环测试表明:循环初期内阻逐渐增加,到一定次数后突然增大。过充电测试有如下结果:对1C、12V过充,循环100次后的电池在测试时呈现不安全性;而对3C、12V过充实验,电池循环25次后测试即不安全。电池不安全行为主要是由于随着循环进行LiCoO2的晶格内部应力增大导致结构变形,活性颗粒开裂粉化,同时界面阻抗增加使得电池内部的焦耳热和副反应产生的热不断积累,使得热产生速率大于热散逸速率,最终导致电池热失控,并出现起火。

Over-charge performances of lithium ion batteries after different cycles

The relationship between safety (especially for overcharge) and cycle state of lithium ion batteries packaged by la-minated aluminum film with normal capacity 720 mAh has been investigated. Cycle test revealed that inner resistance (IR) of batteries increased gradually with cycling and then suddenly increased after certain cycle. Overcharge test demonstrated that batteries caught fire after 100 cycles at 1 C 12 V and 25 cycles at 3 C 12 V, respectively. The results of SEM and XRD experiments showed that the increased inner resistance is due to the pulverization of active particle of LiCoO2 and also thickening of solid electrolyte interface film. The unsafety caused by cycling is mainly attributed to the increase of joule heat and also heat from side reaction promoted by lithium-poor Li1-xCoO2, which led to heat dissipation much less than heat generation.