Fast Li-Ion-Conducting Garnet-Related Li7–3xFexLa3Zr2O12 with Uncommon I4̅3d Structure

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• 作者：Reinhard Wagner ; Günther J. Redhammer ; Daniel Rettenwander ; Gerold Tippelt ; Andreas Welzl ; Stefanie Taibl ; Jürgen Fleig ; Alexandra Franz ; Werner Lottermoser ; Georg Amthauer
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：August 23, 2016
• 年：2016
• 卷：28
• 期：16
• 页码：5943-5951
• 全文大小：507K
• 年卷期：0
• ISSN：1520-5002

文摘

Fast Li-ion-conducting Li oxide garnets receive a great deal of attention as they are suitable candidates for solid-state Li electrolytes. It was recently shown that Ga-stabilized Li₇La₃Zr₂O₁₂ crystallizes in the acentric cubic space group I4̅3d. This structure can be derived by a symmetry reduction of the garnet-type Ia3̅d structure, which is the most commonly found space group of Li oxide garnets and garnets in general. In this study, single-crystal X-ray diffraction confirms the presence of space group I4̅3d also for Li_7–3xFe_xLa₃Zr₂O₁₂. The crystal structure was characterized by X-ray powder diffraction, single-crystal X-ray diffraction, neutron powder diffraction, and Mößbauer spectroscopy. The crystal–chemical behavior of Fe³⁺ in Li₇La₃Zr₂O₁₂ is very similar to that of Ga³⁺. The symmetry reduction seems to be initiated by the ordering of Fe³⁺ onto the tetrahedral Li1 (12a) site of space group I4̅3d. Electrochemical impedance spectroscopy measurements showed a Li-ion bulk conductivity of up to 1.38 × 10^–3 S cm^–1 at room temperature, which is among the highest values reported for this group of materials.