Lithium Atom and A-Site Vacancy Distributions in Lanthanum Lithium Titanate
Lithium Atom and A-Site Vacancy Distributions in Lanthanum Lithium Titanate
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DOI：
10.1021/cm3041357
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发表时间：
2013-05-14
影响因子：
8.6
通讯作者：
Ikuhara, Yuichi
中科院分区：
文献类型：
--
作者：
Gao, Xiang;Fisher, Craig A. J.;Ikuhara, Yuichi
钛酸镧锂（LLTO）是全固态锂离子电池最有前途的电解质材料之一。尽管有许多研究，详细的晶体结构仍然是开放的猜测，因为很难准确地确定锂原子的位置和本征阳离子空位的分布。在这里，我们使用亚埃分辨率扫描透射电子显微镜（STEM）成像方法和空间分辨电子能量损失谱（EELS）分析来研究LLTO的局部原子结构。直接环形亮场（ABF）的观察显示，锂的位置上的O 4窗口的位置在锂贫相La0.62Li0.16TiO 3和附近的A-网站的位置在锂丰富的相La0.56Li0.33TiO 3。A位空位的局部聚集导致Li原子的聚集、八面体倾斜和畸变的增强、O空位的形成和部分Ti 4+的还原。结果表明，局部LLTO结构取决于A位空位的分布和保持层间电荷中性的需要之间的平衡。预计相关的A位空位的局部聚集和Li原子的聚集将影响Li离子的迁移路径，该路径从Li-贫LLTO中的二维变为Li-富LLTO中的三维。这项研究展示了先进的STEM和EELS分析的结合如何为固体离子导体的原子结构和晶体化学提供关键的见解。
Lanthanum lithium titanate (LLTO) is one of the most promising electrolyte materials for all-solid-state lithium-ion batteries. Despite numerous studies, the detailed crystal structure is still open to conjecture because of the difficulty of identifying precisely the positions of Li atoms and the distribution of intrinsic cation vacancies. Here we use subangstrom resolution scanning transmission electron microscopy (STEM) imaging methods and spatially resolved electron energy loss spectroscopy (EELS) analysis to examine the local atomic structure of LLTO. Direct annular bright-field (ABF) observations show Li locations on O4 window positions in Li-poor phase La0.62Li0.16TiO3 and near to A-site positions in Li-rich phase La0.56Li0.33TiO3. Local clustering of A-site vacancies results in aggregation of Li atoms, enhanced octahedral tilting and distortion, formation of O vacancies, and partial Ti4+ reduction. The results suggest local LLTO structures depend on a balance between the distribution of A-site vacancies and the need to maintain interlayer charge neutrality. The associated local clustering of A-site vacancies and aggregation of Li atoms is expected to affect the Li-ion migration pathways, which change from two-dimensional in Li-poor LLTO to three-dimensional in Li-rich LLTO. This study demonstrates how a combination of advanced STEM and EELS analysis can provide critical insights into the atomic structure and crystal chemistry of solid ionic conductors.