Atomic scale imaging of structural changes in solid electrolyte lanthanum lithium niobate upon annealing

作者：Hu Xiaobing; Fisher Craig A J; Kobayashi Shunsuke; Ikuhara Yumi H; Fujiwara Yasuyuki; Hoshikawa Keigo; Moriwake Hiroki; Kohama Keiichi; Iba Hideki; Ikuhara Yuichi

来源：Acta Materialia, 2017, 127: 211-219.

DOI：10.1016/j.actamat.2017.01.028

• Solid-state Li-ion battery
• Solid electrolyte
• Aberration corrected scanning transmission
• electron microscopy
• Structure characterization
• Layered perovskite

La(1-x)/3LixNbO3 (LLNbO) is a promising electrolyte material for solid-state lithium-ion batteries because it is stable in contact with Li metal and contains a high concentration of intrinsic Li-ion vacancies. One strategy for improving its ionic conductivity and making it more competitive with other solid-state Li-ion electrolytes is to disorder the Li-ion vacancies by appropriate post-synthesis heat treatment, e.g., annealing. In this study, we examine the effects of annealing on single crystals of LLNbO with Li contents x = 0.07 and 0.13 based on simultaneous atomic resolution high angle annular dark field and annular bright field imaging methods using state-of-the-art aberration corrected scanning transmission electron microscopes. It is found that La modulation within Al layers of the cation-deficient layered perovskite structure becomes more diffuse after annealing. In addition, some La atoms move to A-site positions and 04 window positions in the nominally vacant A2 layer, while O atom columns in this layer become rumpled in the [001](p) direction, indicating that the NbO6 octahedra are more heavily distorted after annealing. The observed crystal structure differences between as-prepared and annealed single crystals explain the drop in Li-ion conductivities of LLNbO single crystals after heat treatment.

• 出版日期2017-4-1