Superionic lithium conductor with a cubic argyrodite-type structure in the Li–Al–Si–S system

Huang, Wenze; Yoshino, Kazuhiro; Hori, Shingo; Suzuki, Kota; Yonemura, Masao; Hirayama, Masaaki; Kanno, Ryoji

doi:10.1016/j.jssc.2018.12.015

Cited by 43 publications

(36 citation statements)

References 33 publications

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“…Topological analysis of the connectivity between tetrahedral interstices within the argyrodite lattice, 38,42 as well as experimental data for Li6+xSb1-xMxS5I (M = Si, Ge), Li6.15Mʹ1.5S6 and the related oxysulfide Li6.15Mʹ1.5S5.4O0.6 (Mʹ = Al0.1Si0.9), 33,47,48 and the recent theoretical predictions for Li6PS5X (X = I, Cl), 42 all highlight the possible occupation of non-type 5 sites in the Li6PS5X lithium argyrodites. While these non-type 5 sites must play a role in long-ranged Li diffusion in all argyrodites, to our knowledge, no previous experimental evidence exists for non-negligible occupation in Li6PS5X (X= Cl, Br, I).…”

Section: Resultsmentioning

confidence: 99%

Local Charge Inhomogeneity and Lithium Distribution in the Superionic Argyrodites Li₆PS₅X (X = Cl, Br, I)

et al. 2020

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The lithium-argyrodites Li 6 PS 5 X (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 2− anion-disorder, with greater 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 Li 6 PS 5 X (X = Cl, Br, I) 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 Li 6 PS 5 Xargyrodites, suggesting that the lithium conduction pathway in these materials differs from the most common model proposed in earlier studies. Analysis of the Li + positions and their radial distributions reveals that greater inhomogeneityof the local anionic charge, due to X − /S 2− 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 anion configuration and lithium substructure in this family of superionic conductors. File list (2) download file view on ChemRxiv revised manuscript.pdf (2.52 MiB) download file view on ChemRxiv Revised Supporting Information.pdf (1.35 MiB)

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Section: Resultsmentioning

confidence: 99%

Local Charge Inhomogeneity and Lithium Distribution in the Superionic Argyrodites Li₆PS₅X (X = Cl, Br, I)

et al. 2020

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Section: Resultsmentioning

confidence: 99%

On the Local Charge Inhomogeneity and Lithium Distribution in the Superionic Argyrodites Li6PS5X (X = Cl, Br, I)

Minafra¹,

Kraft²,

Bernges³

et al. 2020

Preprint

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The lithium-argyrodites Li6PS5X (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−/S2− anion-disorder, with greater 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 Li6PS5X (X = Cl, Br, I) 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 Li6PS5Xargyrodites, suggesting that the lithium conduction pathway in these materials differs from the most common model proposed in earlier studies. Analysis of the Li+ positions and their radial distributions reveals that greater inhomogeneityof the local anionic charge, due to X−/S2− 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 anion configuration and lithium substructure in this family of superionic conductors.

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“…Some computational evidence for the role of non-type 5 tetrahedra in lithium diffusion in Li 6 PS 5 X argyrodites comes from previous bond-valence calculations, which predict three distinct lithium sites [26,27,29]. Non-type 5 sites have also been identified in recent neutron diffraction studies of Li 6 PS 5 Br and Li 6 PS 5 Cl [46,47], as well as in lithiumargyrodites with lithium stoichiometries x(Li) > 6 [48][49][50]. A general mechanistic description of lithium conduction in lithium-argyrodites that describes the role of different lithium sites and that can explain the relationship between substitutional anion disorder and fast lithium transport, however, is currently lacking.…”

Section: Structural Considerationsmentioning

confidence: 92%

Mechanistic Origin of Superionic Lithium Diffusion in Anion-Disordered Li6PS5X Argyrodites

Morgan

2021

Preprint

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The rational development of fast–ion-conducting solid electrolytes for all-solid-state lithium-ion batteries requires understanding the key structural and chemical principles that give some materials their exceptional ionic conductivities. For the lithium argyrodites Li6PS5X (X = Cl,Br,I), the choice of the halide, X, strongly affects the ionic conductivity, with room-temperature ionic conductivities for X = {Cl, Br} ×103 higher than for X = I. This variation has been attributed to differing degrees of S/X anion disorder. For X = {Cl, Br} the S/X anions are substitutionally disordered, while for X = I the anion sublattice is fully ordered. To better understand the role of substitutional anion disorder in enabling fast lithium-ion transport, we have performed a first-principles molecular dynamics study of Li6PS5I and Li6PS5Cl, with varying amounts of S/X anion-site disorder. Considering the S/X substructure as a tetrahedrally close-packed lattice, we identify three partially occupied lithium sites that form a contiguous three-dimensional network of face-sharing tetrahedra. The active lithium-ion diffusion pathways within this network, however, depend on the S/X anion configuration. For anion-disordered systems, the active site–site pathways give a percolating three-dimensional diffusion network; whereas for anion-ordered systems, critical site–site pathways are inactive, giving a disconnected diffusion network with lithium motion restricted to local orbits around S positions. Analysis of the lithium substructure and dynamics in terms of the lithium coordination around each sulfur site shows a mechanistic link between substitutional anion disorder and lithium disorder, which enables fast lithium diffusion. In anion-ordered systems the Li-ions are pseudo-ordered, with preferential 6-fold coordination of sulfur sites. Long-ranged lithium diffusion disrupts this SLi6 pseudo-ordering, and is therefore disfavoured. In anion-disordered systems, a uniform 6-fold S–Li coordination is frustrated due to Li–Li Coulombic repulsion. Lithium positions become disordered, giving a range of S–Li coordination environments. Long-ranged Li diffusion is now possible with no net change in S–Li coordination numbers. This gives rise to superionic lithium transport in the anion-disordered systems, which is effected by a concerted string-like diffusion mechanism.

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Superionic lithium conductor with a cubic argyrodite-type structure in the Li–Al–Si–S system

Cited by 43 publications

References 33 publications

Local Charge Inhomogeneity and Lithium Distribution in the Superionic Argyrodites Li₆PS₅X (X = Cl, Br, I)

Local Charge Inhomogeneity and Lithium Distribution in the Superionic Argyrodites Li₆PS₅X (X = Cl, Br, I)

On the Local Charge Inhomogeneity and Lithium Distribution in the Superionic Argyrodites Li6PS5X (X = Cl, Br, I)

Mechanistic Origin of Superionic Lithium Diffusion in Anion-Disordered Li6PS5X Argyrodites

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