Li-Rich and Halide-Deficient Argyrodite Fast Ion Conductors

Laidong Zhou; Qiang Zhang; Linda F. Nazar

doi:10.1021/acs.chemmater.2c02343

Li-Rich and Halide-Deficient Argyrodite Fast Ion Conductors

Laidong Zhou, Qiang Zhang, Linda F. Nazar

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Abstract

We report on a new family of halide-deficient and Li-rich argyrodite fast-ion conductors, Li_6+xPS_5+x(Cl/Br/I)_1-x(0 ≤ x ≤ 0.85). Exploration of the influence of aliovalent anion substitution in Li₆PS₅X (X = Cl, Br, I)─using a combination of high-resolution powder neutron diffraction and electrochemical impedance spectroscopy─reveals that aliovalent anion substitution induces higher Li-ion concentration and Li site disorder, and creates S^2-/I^-anion site disorder on the 4a site. In the series Li_6+xPS_5+xI_1-x(0 ≤ x ≤ 0.4), the resulting conductivity for Li_6.4PS_5.4I_0.6(0.13 mS·cm^-1) represents almost a 100-fold increase over that of the parent phase, Li₆PS₅I (0.0033 mS·cm^-1), and establishes one of the first fast-ion conducting argyrodite thiophosphate iodides. For Cl-argyrodites, the ionic conductivity decreases a little with lower halide-content but ionic conductivity for the Br-argyrodites is almost unchanged. Overall, all Cl/Br-argyrodites Li_6+xPS_5+x(Cl/Br)_1-x(0 ≤ x ≤ 0.75) with a low halide content exhibit surprisingly high ionic conductivities > 1 mS·cm^-1despite a very low degree of sulfur/halogen anion site disorder. Our findings highlight the importance of attaining a disordered Li-ion sublattice and sulfur/halogen anion site disorder (anionic charge homogeneity) in argyrodites, where Li ions occupy high energy sites and activate concerted ion migration that drives the ionic conductivity.

Original language	English
Pages (from-to)	9634-9643
Number of pages	10
Journal	Chemistry of Materials
Volume	34
Issue number	21
DOIs	https://doi.org/10.1021/acs.chemmater.2c02343
State	Published - Nov 8 2022

Funding

This work was supported by the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. L.F.N. also acknowledges NSERC for platform support via their Canada Research Chair and Discovery Grant programs. The neutron diffraction measurements at the POWGEN instrument at Oak Ridge National Laboratory, Spallation Neutron Source, were sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. We thank Prof. Jeff Sakamoto and Won Joon Suk (University of Michigan) for helpful discussions.

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10.1021/acs.chemmater.2c02343

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title = "Li-Rich and Halide-Deficient Argyrodite Fast Ion Conductors",

abstract = "We report on a new family of halide-deficient and Li-rich argyrodite fast-ion conductors, Li6+xPS5+x(Cl/Br/I)1-x(0 ≤ x ≤ 0.85). Exploration of the influence of aliovalent anion substitution in Li6PS5X (X = Cl, Br, I)─using a combination of high-resolution powder neutron diffraction and electrochemical impedance spectroscopy─reveals that aliovalent anion substitution induces higher Li-ion concentration and Li site disorder, and creates S2-/I-anion site disorder on the 4a site. In the series Li6+xPS5+xI1-x(0 ≤ x ≤ 0.4), the resulting conductivity for Li6.4PS5.4I0.6(0.13 mS·cm-1) represents almost a 100-fold increase over that of the parent phase, Li6PS5I (0.0033 mS·cm-1), and establishes one of the first fast-ion conducting argyrodite thiophosphate iodides. For Cl-argyrodites, the ionic conductivity decreases a little with lower halide-content but ionic conductivity for the Br-argyrodites is almost unchanged. Overall, all Cl/Br-argyrodites Li6+xPS5+x(Cl/Br)1-x(0 ≤ x ≤ 0.75) with a low halide content exhibit surprisingly high ionic conductivities > 1 mS·cm-1despite a very low degree of sulfur/halogen anion site disorder. Our findings highlight the importance of attaining a disordered Li-ion sublattice and sulfur/halogen anion site disorder (anionic charge homogeneity) in argyrodites, where Li ions occupy high energy sites and activate concerted ion migration that drives the ionic conductivity.",

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AU - Zhou, Laidong

AU - Zhang, Qiang

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N2 - We report on a new family of halide-deficient and Li-rich argyrodite fast-ion conductors, Li6+xPS5+x(Cl/Br/I)1-x(0 ≤ x ≤ 0.85). Exploration of the influence of aliovalent anion substitution in Li6PS5X (X = Cl, Br, I)─using a combination of high-resolution powder neutron diffraction and electrochemical impedance spectroscopy─reveals that aliovalent anion substitution induces higher Li-ion concentration and Li site disorder, and creates S2-/I-anion site disorder on the 4a site. In the series Li6+xPS5+xI1-x(0 ≤ x ≤ 0.4), the resulting conductivity for Li6.4PS5.4I0.6(0.13 mS·cm-1) represents almost a 100-fold increase over that of the parent phase, Li6PS5I (0.0033 mS·cm-1), and establishes one of the first fast-ion conducting argyrodite thiophosphate iodides. For Cl-argyrodites, the ionic conductivity decreases a little with lower halide-content but ionic conductivity for the Br-argyrodites is almost unchanged. Overall, all Cl/Br-argyrodites Li6+xPS5+x(Cl/Br)1-x(0 ≤ x ≤ 0.75) with a low halide content exhibit surprisingly high ionic conductivities > 1 mS·cm-1despite a very low degree of sulfur/halogen anion site disorder. Our findings highlight the importance of attaining a disordered Li-ion sublattice and sulfur/halogen anion site disorder (anionic charge homogeneity) in argyrodites, where Li ions occupy high energy sites and activate concerted ion migration that drives the ionic conductivity.

AB - We report on a new family of halide-deficient and Li-rich argyrodite fast-ion conductors, Li6+xPS5+x(Cl/Br/I)1-x(0 ≤ x ≤ 0.85). Exploration of the influence of aliovalent anion substitution in Li6PS5X (X = Cl, Br, I)─using a combination of high-resolution powder neutron diffraction and electrochemical impedance spectroscopy─reveals that aliovalent anion substitution induces higher Li-ion concentration and Li site disorder, and creates S2-/I-anion site disorder on the 4a site. In the series Li6+xPS5+xI1-x(0 ≤ x ≤ 0.4), the resulting conductivity for Li6.4PS5.4I0.6(0.13 mS·cm-1) represents almost a 100-fold increase over that of the parent phase, Li6PS5I (0.0033 mS·cm-1), and establishes one of the first fast-ion conducting argyrodite thiophosphate iodides. For Cl-argyrodites, the ionic conductivity decreases a little with lower halide-content but ionic conductivity for the Br-argyrodites is almost unchanged. Overall, all Cl/Br-argyrodites Li6+xPS5+x(Cl/Br)1-x(0 ≤ x ≤ 0.75) with a low halide content exhibit surprisingly high ionic conductivities > 1 mS·cm-1despite a very low degree of sulfur/halogen anion site disorder. Our findings highlight the importance of attaining a disordered Li-ion sublattice and sulfur/halogen anion site disorder (anionic charge homogeneity) in argyrodites, where Li ions occupy high energy sites and activate concerted ion migration that drives the ionic conductivity.

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Li-Rich and Halide-Deficient Argyrodite Fast Ion Conductors

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