Influence of Li+ and H+ Distribution on the Crystal Structure of Li7–xHxLa3Zr2O12 (0 ≤ x ≤ 5) Garnets

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• 作者：Alodia Orera ; Guillermo Larraz ; José Alberto Rodríguez-Velamazán ; Javier Campo ; María Luisa Sanjuán
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：February 1, 2016
• 年：2016
• 卷：55
• 期：3
• 页码：1324-1332
• 全文大小：385K
• ISSN：1520-510X

文摘

With appropriate doping or processing, Li₇La₃Zr₂O₁₂ (LLZO) is an excellent candidate to be used in Li batteries either as a solid electrolyte or as a separator between the Li anode and a liquid electrolyte. For both uses, the reactivity with water either from the air or in aqueous media is a matter of interest. We address here the structural changes undergone by LLZO as a result of H⁺/Li⁺ exchange and relate them with the amount of H content and atomic distribution. Neutron diffraction is performed to elucidate Li and H location. Two different cubic phases derive from LLZO through H⁺/Li⁺ exchange: Deep hydration up to 150 °C yields a noncentrosymmetric I4?3d phase in which octahedral Li ions are exchanged by H ions, tetrahedral Li ions split into two sites with very different occupancies, and H ions form O₄H₄ entities around the less occupied tetrahedral site. Annealing above 300 °C results in a centrosymmetric Ia3?d phase with lower H content in which Li ions occupy the usual sites of the cubic garnets and H ions occupy a split pseudooctahedral site. The centrosymmetric or noncentrosymmetric character is determined by the temperature at which exchange is performed and the H content. Both factors are not independent: at low temperature, the high H content favors H ordering around the vacant tetrahedra, while low H content and higher mobility at 350 °C lead to a disordered configuration of Li and H ions. The deeply hydrated garnets are stable up to at least 300 °C and also upon aging at room temperature.