储存后锂离子电池的性能研究

Study on the performance of lithium ion battery after storage

以不同温度、不同荷电态对锂离子电池进行储存实验,通过X射线衍射光谱法(XRD)和场发射扫描电子显微镜(FESEM)等手段研究了储存前后电极活性物质结构和表面形貌的变化;并对储存前后的电池进行测试,研究了储存对锂离子电池的容量、循环稳定性和安全性等综合性能的影响。结果发现,经不同荷电态高温储存后,锂离子电池正负极活性物质的体相结构没有发生变化,但其正极材料的微晶尺度和微应力随储存时荷电态的升高而减小;储存后,正极表面出现较明显的钝化膜,负极表面的固体电解质相界面(SEI)膜增厚。经高荷电态储存后,锂离子电池的交流内阻和厚度变大,1C容量发生衰减,电极充放电极化增大,电池的1C循环性能下降,安全性能下降;放电态储存后,电池的综合性能无明显变化。说明,放电态储存对于锂离子电池是一种较好的储存条件,有利于储存后电池综合性能的保持。

Lithium ion batteries were stored at elevated temperature in different state of charge（SOC）. The structure and morphology of the electrode materials were investigated by means of XRD and FESEM, and the general performances of the batteries before and after storage were tested. The experimental results revealed that after storage at elevated temperature, the microcrystal and microstress of cathode material reduced as the storing SOC of batteries going up, though the bulk structures did not change. Meanwhile, during storage there deposited a passivation film on the surface of cathode as the SEI （solid electrolyte interface） film on the anode getting thicker. After stored in high SOC,the general performance of the batteries changed more obviously, including the fading of 1 C capacity, the deterioration of 1 C cycling performance, the degradation of safety performance and so on. However, the performance of the lithium ion batteries that were stored in low SOC condition didn＇t degrade. Therefore, it can be concluded that storage at low SOC condition is propitious to keep original general performance of lithium ion battery.