Minafra Nicolò, Kraft Marvin A, Bernges Tim, Li Cheng, Schlem Roman, Morgan Benjamin J, Zeier Wolfgang G
Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany.
Center for Materials Research (LaMa), Justus-Liebig-University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany.
Inorg Chem. 2020 Aug 3;59(15):11009-11019. doi: 10.1021/acs.inorgchem.0c01504. Epub 2020 Jul 16.
The lithium argyrodites LiPSX (X = Cl, Br, I) exhibit high lithium-ion conductivities, making them promising candidates for use in solid-state batteries. These solid electrolytes can show considerable substitutional X/S anion disorder, typically correlated with higher lithium-ion conductivities. The atomic-scale effects of this anion site disorder within the host lattice-in particular how lattice disorder modulates the lithium substructure-are not well understood. Here, we characterize the lithium substructure in LiPSX as a function of temperature and anion site disorder, using Rietveld refinements against temperature-dependent neutron diffraction data. Analysis of these high-resolution diffraction data reveals an additional lithium position previously unreported for LiPSX argyrodites, suggesting that the lithium conduction pathway in these materials differs from the most common model proposed in earlier studies. An analysis of the Li positions and their radial distributions reveals that greater inhomogeneity of the local anionic charge, due to X/S site disorder, is associated with more spatially diffuse lithium distributions. This observed coupling of site disorder and lithium distribution provides a possible explanation for the enhanced lithium transport in anion-disordered lithium argyrodites and highlights the complex interplay between the anion configuration and lithium substructure in this family of superionic conductors.
锂硫银锗矿LiPSX（X = Cl、Br、I）具有高锂离子电导率，使其成为固态电池的有前景的候选材料。这些固体电解质会表现出相当程度的X/S阴离子替代无序，通常与较高的锂离子电导率相关。主体晶格内这种阴离子位点无序的原子尺度效应，特别是晶格无序如何调节锂子结构，目前还不太清楚。在这里，我们利用对温度相关的中子衍射数据进行的Rietveld精修，将LiPSX中的锂子结构表征为温度和阴离子位点无序的函数。对这些高分辨率衍射数据的分析揭示了一个先前未报道过的LiPSX硫银锗矿的额外锂位置，这表明这些材料中的锂传导途径与早期研究中提出的最常见模型不同。对锂位置及其径向分布的分析表明，由于X/S位点无序导致的局部阴离子电荷的更大不均匀性与更空间弥散的锂分布相关。观察到的位点无序与锂分布的这种耦合为阴离子无序锂硫银锗矿中锂传输增强提供了一种可能的解释，并突出了该超离子导体家族中阴离子构型与锂子结构之间复杂的相互作用。
