The advantageous properties of (pseudo)halide argyrodite ion conductors of the formula Li6PS5X (X = Cl–, Br–, I–, CN–) have motivated extensive studies of their structure-transport relationships, particularly as they pertain to the role of atomic site disorder. The argyrodite structure can accommodate additional configurational complexity to promote ion transport via extended three-anion site mixing and the potential for orientational disorder of molecular anions. In this work, we explore a ternary anion system including the cyanide anion, expanding site disorder and introducing dipolar orientations as an additional degree of freedom. We prepared the series Li6PS5(CN)1–xBrx, in which the dipolar cyanide anions are systematically diluted with bromide. We find that anion disorder, as determined by synchrotron and neutron diffraction and quantified by configurational entropy (Sconfig), is correlated with lowered activation barriers and increased lithium ion conductivity. We propose that Sconfig describes the electrostatic heterogeneity of the Li environments, flattening the energetic landscape for ion transport. While anion substitution strongly impacts the activation barrier for transport, the temperature-independent Arrhenius prefactor does not follow the same trend. Through heat-capacity measurements of attempt frequency and deconvolution of terms within the prefactor, we rationalize the apparent decoupling of activation energy and prefactor to strong cyanide-lithium interactions that increase the entropy of migration. Together, these results expand the structure–property relationships in the argyrodite family to encompass multiple facets of disorder and the subsequent impact on lithium ion transport.
Galinat, Shelby L., Willard, Claire M., Valeti, Krishna Teja, Smaha, Rebecca W., Staerz, Anna, & Maughan, Annalise E. (2025). Expanding Configurational Complexity through Dipole Dilution in Pseudohalide Argyrodite Ion Conductors. Chemistry of Materials, 37(24). https://doi.org/10.1021/acs.chemmater.5c02236
Galinat, Shelby L., Willard, Claire M., Valeti, Krishna Teja, et al., "Expanding Configurational Complexity through Dipole Dilution in Pseudohalide Argyrodite Ion Conductors," Chemistry of Materials 37, no. 24 (2025), https://doi.org/10.1021/acs.chemmater.5c02236
@article{osti_3010480,
author = {Galinat, Shelby L. and Willard, Claire M. and Valeti, Krishna Teja and Smaha, Rebecca W. and Staerz, Anna and Maughan, Annalise E.},
title = {Expanding Configurational Complexity through Dipole Dilution in Pseudohalide Argyrodite Ion Conductors},
annote = {The advantageous properties of (pseudo)halide argyrodite ion conductors of the formula Li6PS5X (X = Cl–, Br–, I–, CN–) have motivated extensive studies of their structure-transport relationships, particularly as they pertain to the role of atomic site disorder. The argyrodite structure can accommodate additional configurational complexity to promote ion transport via extended three-anion site mixing and the potential for orientational disorder of molecular anions. In this work, we explore a ternary anion system including the cyanide anion, expanding site disorder and introducing dipolar orientations as an additional degree of freedom. We prepared the series Li6PS5(CN)1–xBrx, in which the dipolar cyanide anions are systematically diluted with bromide. We find that anion disorder, as determined by synchrotron and neutron diffraction and quantified by configurational entropy (Sconfig), is correlated with lowered activation barriers and increased lithium ion conductivity. We propose that Sconfig describes the electrostatic heterogeneity of the Li environments, flattening the energetic landscape for ion transport. While anion substitution strongly impacts the activation barrier for transport, the temperature-independent Arrhenius prefactor does not follow the same trend. Through heat-capacity measurements of attempt frequency and deconvolution of terms within the prefactor, we rationalize the apparent decoupling of activation energy and prefactor to strong cyanide-lithium interactions that increase the entropy of migration. Together, these results expand the structure–property relationships in the argyrodite family to encompass multiple facets of disorder and the subsequent impact on lithium ion transport.},
doi = {10.1021/acs.chemmater.5c02236},
url = {https://www.osti.gov/biblio/3010480},
journal = {Chemistry of Materials},
issn = {ISSN 0897-4756},
number = {24},
volume = {37},
place = {United States},
publisher = {American Chemical Society (ACS)},
year = {2025},
month = {12}}
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 379, Issue 2211https://doi.org/10.1098/rsta.2019.0458