A deeper understanding of the relationships among composition‒structure‒transport properties in inorganic solid ionic conductors is of paramount importance to develop highly conductive phases for future employment in solid‒state Li‒ion battery applications. In order to shed light on the mechanisms that regulate these relationships, in this work we perform a “two-dimensional” substitution series in the thio-LISICON family Li4Ge1‒xSnxS4‒ySey. The structural modifications brought up by the elemental substitutions were investigated via Rietveld refinements against high‒resolution neutron diffraction data that allowed a precise characterization of the anionic framework and the lithium substructure. The analyses show that the anionic and cationic substitutions influence the polyhedral and unit cell volumes in different fashions and that the size of the polyanionic groups alone is not enough to describe lattice expansion in these materials. Moreover, we show that the lithium disorder that is crucial to achieve fast ionic mobility may be correlated to the lithium polyhedral volumes. The correlation of these structural modifications with the transport properties, investigated via electrochemical impedance spectroscopy and 7Li nuclear magnetic resonance spin-lattice relaxation measurements, shows a non-monotonic behavior of the ionic conductivity and activation energy against the lithium polyhedral volumes, hinting to an optimal size of the conduction pathways for the ionic diffusion. Ultimately, the results obtained in this work will help to establish new guidelines for the optimization of solid electrolytes and to gain a more profound understanding of the influence of the substituents on the structure and transport properties of Li‒ion conductors

中文翻译：

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二维替代：更好地理解锂-超离子硫-LISICON中的结构-运输相关性。

深入了解无机固体离子导体中组成-结构-传输性质之间的关系对于开发高导电性相，以供将来在固态锂离子电池应用中使用至关重要。为了阐明调节这些关系的机制，在这项工作中，我们在硫代-LISICON家族Li4Ge1‒xSnxS4‒ySey中执行了“二维”置换系列。通过Rietveld改进方法对高分辨率中子衍射数据进行了研究，研究了元素取代引起的结构修饰，高分辨率中子衍射数据可精确表征阴离子骨架和锂亚结构。分析表明，阴离子和阳离子取代以不同的方式影响多面体和晶胞的体积，仅聚阴离子基团的大小不足以描述这些材料中的晶格膨胀。此外，我们表明对实现快速离子迁移至关重要的锂无序现象可能与锂多面体体积有关。通过电化学阻抗谱和7Li核磁共振自旋晶格弛豫测量研究了这些结构修饰与输运性质的相关性，显示出离子电导率和活化能对锂多面体体积的非单调性，暗示了最佳离子扩散的传导路径的大小。最终，