Zimmermann Benjamin, Fuchs Till, Westphal Johannes, Janek Jürgen, Lepple Maren
Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, Giessen 35392, Germany.
Institute of Physical Chemistry, Justus Liebig University Giessen, Giessen 35392, Germany.
ACS Org Inorg Au. 2025 Apr 30;5(3):211-220. doi: 10.1021/acsorginorgau.5c00021. eCollection 2025 Jun 4.
Lithium garnets offer promising structural and electrochemical properties and could be used in all solid-state lithium batteries replacing liquid electrolytes. They can operate in a wide electrochemical voltage window and show high ionic conductivities (>10 S cm). The best-studied lithium garnet is LiLaZrO (LLZO), which is known to undergo a transition from an ordered, tetragonal form to a disordered cubic modification at elevated temperatures. This is crucial, as the cubic modification offers about 2 orders of magnitude higher ionic conductivities. Applying the high-entropy concept to this material facilitates the stabilization of the cubic structure at ambient conditions. In this work, four different lithium garnet compositions based on LiLaZrNbTaHfO have been synthesized by mixing Zr, Nb, Ta, and Hf by Sn, respectively, using two different solid-state approaches. They have been characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, and impedance spectroscopy to analyze the influence of synthesis parameters and composition on phase purity, elemental distribution, and ionic conductivity. It was found that combining calcination and sintering into one process yields a higher density and ionic conductivity than splitting it into two with intermediate regrinding of the material. Impedance data indicate an increase in ionic conductivity when substituting pentavalent ions for tetravalent ones due to the resulting higher concentration of mobile charge carriers in the structure, compared to LiLaZrNbTaHfO.
锂石榴石具有良好的结构和电化学性能，可用于替代液体电解质的全固态锂电池。它们能在较宽的电化学电压窗口内工作，并表现出高离子电导率（>10 S cm）。研究最多的锂石榴石是LiLaZrO（LLZO），已知其在高温下会从有序的四方相转变为无序的立方相。这一点至关重要，因为立方相的离子电导率高出约两个数量级。将高熵概念应用于这种材料有助于在环境条件下稳定立方结构。在这项工作中，通过分别使用两种不同的固态方法，将Zr、Nb、Ta和Hf与Sn混合，合成了四种基于LiLaZrNbTaHfO的不同锂石榴石组合物。通过X射线衍射、能量色散X射线光谱和阻抗光谱对它们进行了表征，以分析合成参数和组成对相纯度、元素分布和离子电导率的影响。结果发现，与将煅烧和烧结分为两步并对材料进行中间再研磨相比，将煅烧和烧结合并为一个过程可获得更高的密度和离子电导率。阻抗数据表明，用五价离子取代四价离子时，离子电导率会增加，这是因为与LiLaZrNbTaHfO相比，结构中移动电荷载流子的浓度更高。
