石墨/LiFePO_4电池储存性能的XRD研究  

Study of storage performance of a graphite/LiFePO_4 cell by XRD

作　　者：李佳[1,2] 廖文俊[1] 曾乐才[1] 夏保佳[2] 

机构地区：[1]上海电气集团股份有限公司中央研究院,上海200070 [2]中国科学院上海微系统与信息技术研究所,上海200050

出　　处：《电源技术》2013年第11期1909-1913,共5页Chinese Journal of Power Sources

基　　金：国家自然科学基金(20773157);中国科学院院地合作项目(DBSH-2011-009)

摘　　要：通过充放电测试和X射线衍射分析等方法。研究了石墨／LiFePO4电池高温储存后的性能变化规律和机理。结果表明，以25％，75％SOC储存过程中，电池的容量表现出一个先略有增加后衰减的过程；为了研究其机理，首次采用泽温的无标样法定量计算研究储存前后LiFePO4脱嵌锂过程的结构变化，发现，储存前，LiFePOJFePO4相变过程存在明显的滞后现象；储存后这一滞后减小。其原因可能在于，LiFePO4以脱锂态储存时，材料颗粒中LiFePO4和FePO4两相共存。由于两相问的体积差。两相界面上存在内应力，使两相晶粒沿着界面方向分裂。从而产生新鲜界面，同时。这也达到减小颗粒粒度的效果。因此储存后充放电过程中LiFePO4材料的LiFePO4/FePO4相变的滞后性减小，电池的容量提高。The performance variations and the mechanisms of a graphite/ LiFePO, cell after storage at elevated temperature were studied by charge-discharge tests and X-ray diffraction （XRD）. It indicates that during stored in 25%-75% SOC, the capacity of the cell first increases and then decreases. The structure variations of LiFePO4 during lithiation/de-lithiation process before and after storage were studied by the Zevon＇s quantitative calculation method without standard sample for the first time. It is revealed that before storage LiFePO4/FePO, phase transition shows an obvious hysteresis, but it turns inconspicuous after storage. The reason could be as follows. LiFePO, and FePO4 coexisted in the de-lithiated LiFePO, electrode. Their volume difference caused the internal stress, which made them split along the phase surface. Not only the fresh surface augmented, but also it achieved the effect as same as reducing particle size. As the result, the hysteresis of LiFePO,JFePO4 phase transition decreased and the capacity of the cell increased.

关 键 词：锂离子电池 磷酸铁锂 储存 晶胞体积 

分 类 号：TM912.9[电气工程—电力电子与电力传动]