Structural and Electronic State Changes of Spinel Oxides During Lithium Insertion and Extraction

用X射线衍射法和电子自旋共振法分析了尖晶石LiMn2O4中锂的插入和提取过程。从这些分析可以看出，LiMn2O4随着锂含量的减少而变得不稳定。为了防止这种行为，本研究开发了一种新的尖晶石化合物。一般来说，尖晶石化合物的结构有时具有阳离子有序性。这种阳离子有序为晶体结构提供了稳定性。因此，通过阳离子有序效应产生的稳定能可以克服LiMn2O4在锂离子抽提过程中的不稳定性。在本研究中，我们制备了在16d位具有阳离子有序性的Li_&lt；4/3&gt；Mn_&lt；5/3&gt；O_4。X-射线衍射法证实，在该化合物中，Li和Mn离子以规则的方式占据16d位。用X射线衍射法和电化学方法分析了该化合物的结构和电子态的变化。不同锂含量下的X射线衍射图不能区分，表明这种超结构尖晶石的结构变化是无穷小的。这种结构行为类似于锂插入和提取材料的理想结构行为。在恒流条件下，还研究了电极的电化学电位变化。在锂的插入和提取过程中，电位没有变化。通常情况下，电极电位随着锂含量的变化而逐渐变化。因此，这种超结构尖晶石的电化学行为非常有趣。Ti(Li_&lt；4/3&gt；Ti_&lt；5/3&gt；O_4)的超结构尖晶石也有相同的行为。因此，超级结构提供了一个非常独特的特征，这在任何地方都没有报道过。

An insertion and extraction of lithium into/from spinel LiMn_2O_4 were analyzed by X-ray diffraction and electron spin resonance methods. From these analyzes, it can be seen that LiMn_2O_4 become unstable with decreasing lithium content. In order to prevent such a behavior, a new spinel compound was developed in this study. In general, spinel compounds sometimes have a cation ordering in their structure. This cation ordering provides a stabilization to a crystal structure. Therefore, the unstableness of LiMn_2O_4 caused by a lithium extraction may be overcome by such a stabilization energy from the cation ordering effect. In this study, we prepared Li_<4/3>Mn_<5/3>O_4 which has a cation ordering at 16d sites. In this compound, Li and Mn ions occupied 16d sites in a regular manner, that was confirmed by X-ray diffraction method. The structural and electronic state changes of this Mn compound were analyzed by X-ray diffraction and electrochemical methods. The X-ray diffraction patterns at various lithium contents could not be distinguished, indicating that the structural change of this super structure spinel is infinitesimal. This structural behavior is like an ideal one for lithium insertion and extraction materials. The electrochemical potential change was also investigated under a galvanostatic condition. The potential did not change during the lithium insertion and extraction. Usually, the electrode potential changes gradually with changing lithium content. So, the electrochemical behavior of this super structure spinel is extremely interesting. The same behaviors were also observed for super structure spinel of Ti (Li_<4/3>Ti_<5/3>O_4) . Thus, the super structure provides a very unique characteristics which has never been reported anywhere.