Electrochemical and in situ XAFS-XRD investigation of Nb2O5 for rechargeable lithium batteries
Electrochemical and in situ XAFS-XRD investigation of Nb2O5 for rechargeable lithium batteries
复制标题
DOI：
10.1149/1.2163788
复制
发表时间：
2006-01-01
影响因子：
3.9
通讯作者：
Kumagai, N
中科院分区：
文献类型：
--
作者：
Kodama, R;Terada, Y;Kumagai, N
Nb_2O_5具有多种晶系，如正交晶系(O)、四方晶系(T)和单斜晶系(M)，其中900-1000℃合成的Nb_2O_5被用作2-V锂离子电池的正极材料。电池的性能取决于Nb_2O_5的结构，在1000℃下合成的t-Nb_2O_5具有良好的循环性能，放电容量为190mAhg氧化物(-1)。考察了Nb2O5在电化学反应过程中的结构变化。原位同步辐射X射线衍射仪测试表明，o-和t-Nb2O5保持了原有的晶格结构，即使在Li嵌入后，晶胞体积也有很小的变化。O-和t-Nb_2O_5的原位X射线吸收精细结构(XAFS)分析表明，在插层过程中发生了从Nb~(5+)到Nb~(4+)的连续变化。在嵌锂的两种结构中，Nb-O八面体发生了显著的重排，同时Nb-O和Nb-Nb相互作用也发生了变化。X射线衍射和X射线光电子能谱分析表明，与o-Nb_2O_5的三维结构相比，t-Nb_2O_5的二维层状结构对于Li的嵌入似乎更灵活。这可能是由于前者作为电极材料具有更好的循环性能。(C)2006年电化学会。
Nb2O5 exhibits various crystal systems, such as orthorhombic (o), tetragonal (t), and monoclinic (m), among which Nb2O5 synthesized at 900-1000 degrees C is commercially used as a cathode material of the 2-V lithium ion battery. The battery performances depended on the structure of Nb2O5, and the t-Nb2O5 synthesized at 1000 C exhibited an excellent cycling performance with a large discharge capacity of 190 mAh (g oxide)(-1). The structural variations of Nb2O5 during electrochemical reaction were examined. The in situ synchrotron radiation-X-ray diffraction (XRD) measurement indicated that o- and t-Nb2O5 maintain their original crystal lattices, accompanying a small change in the cell volume even after the Li intercalation. The in situ X-ray absorption fine structure (XAFS) analysis of o- and t-Nb2O5 revealed that the continuous variation from Nb5+ to Nb4+ took place during the intercalation process. A significant rearrangement of the Nb-O octahedra accompanied by the change of Nb-O and Nb-Nb interactions occurred in both structures with Li intercalation. XRD and XAFS data suggests that the two-dimensional layer structure of t-Nb2O5 seems to be more flexible regarding the Li intercalation compared with the three-dimensional structure of o- Nb2O5. This may account for the better cyclic performance of the former material as the electrode material. (c) 2006 The Electrochemical Society.