Nakayama Masanobu, Wakihara Masataka, Kobayashi Yo, Miyashiro Hajime
Department of Applied Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8552, Japan.
J Phys Chem B. 2005 Aug 4;109(30):14648-53. doi: 10.1021/jp052142r.
The relationship between the Li arrangement and the electrochemical behavior has been examined as a function of composition x in electrochemically lithiated A-site deficient perovskite, Li(x)()La(1/3)NbO(3). The cell potential diagram and powder X-ray diffraction (XRD) study indicated that the Li ions are inserted into the vacant Perovskite A-site with an electrochemical reaction. In addition, the derivatives of the cell potential diagram showed three cathodic peaks, indicating a stepwise Li insertion mechanism takes place. Such a stepwise behavior would be ascribed to the changes in arrangement of inserted Li ions in the Perovskite lattice, since the XRD patterns of pristine La(1/3)NbO(3) showed that the La arrangement in La(1/3)NbO(3) was ordered along the c-axis, causing two kinds of A-site vacancies. To reveal the changes in the arrangement of Li ions, the entropy measurement of the reaction was performed by both the electrochemical and the calorimetric techniques. Moreover, the formation energy of the Perovskite structure with various Li arrangements was compared by using an ab initio calculation. The results of experiment and computation suggested that the electrochemical reaction proceeded via two kinds of superstructures of Li(1/6)La(1/3)NbO(3) and Li(1/2)La(1/3)NbO(3) due to the ordered arrangement of Li ions.
在电化学锂化的 A 位缺陷钙钛矿 Li(x)()La(1/3)NbO(3)中，研究了锂排列与电化学行为之间随组成 x 的关系。电池电势图和粉末 X 射线衍射（XRD）研究表明，锂离子通过电化学反应插入到钙钛矿的空 A 位中。此外，电池电势图的导数显示出三个阴极峰，表明发生了逐步的锂插入机制。这种逐步行为归因于钙钛矿晶格中插入锂离子排列的变化，因为原始 La(1/3)NbO(3)的 XRD 图谱表明 La(1/3)NbO(3)中 La 的排列沿 c 轴有序，导致两种 A 位空位。为了揭示锂离子排列的变化，通过电化学和量热技术对反应的熵进行了测量。此外，使用从头算计算比较了具有各种锂排列的钙钛矿结构的形成能。实验和计算结果表明，由于锂离子的有序排列，电化学反应通过 Li(1/6)La(1/3)NbO(3)和 Li(1/2)La(1/3)NbO(3)两种超结构进行。
