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Abstract The correlation between lattice chemistry and cation migration in high‐entropy Li+conductors is not fully understood due to challenges in characterizing anion disorder. To address this issue, argyrodite family of Li+conductors, which enables structural engineering of the anion lattice, is investigated. Specifically, new argyrodites, Li5.3PS4.3Cl1.7−xBrx(0 ≤x≤ 1.7), with varying anion entropy are synthesized and X‐ray diffraction, neutron scattering, and multinuclear high‐resolution solid‐state nuclear magnetic resonance (NMR) are used to determine the resulting structures. Ion and lattice dynamics are determined using variable‐temperature multinuclear NMR relaxometry and maximum entropy method analysis of neutron scattering, aided by constrained ab initio molecular dynamics calculations. 15 atomic configurations of anion arrangements are identified, producing a wide range of local lattice dynamics. High entropy in the lattice structure, composition, and dynamics stabilize otherwise metastable Li‐deficient structures and flatten the energy landscape for cation migration. This resulted in the highest room‐temperature ionic conductivity of 26 mS cm−1and a low activation energy of 0.155 eV realized in Li5.3PS4.3Cl0.7Br, where anion disorder is maximized. This study sheds light on the complex structure–property relationships of high‐entropy superionic conductors, highlighting the significance of heterogeneity in lattice dynamics.
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Thermal and electronic transport properties of A Cr X 2 superionic conductors (A=Cu, Ag and X=S, Se)
Abstract Superionic conductors, includingACrX2(A=Ag, Cu; X = S, Se) compounds, have attracted attention due to their low lattice thermal conductivity and high ionic conductivity. These properties are driven by structural characteristics such as anharmonicity, soft bonding, and disorder, which enhance both fast ion transport and thermal resistance. In the present study, we investigate the impact of various factors (e.g.A-site disorder, microstructure, speed of sound and chemical composition) on the thermal conductivity of the compounds CuCrS2, CuCrSe2, AgCrS2and AgCrSe2. The samples were synthesized using solid state reaction, ball milling and subsequent spark plasma sintering, and thermal diffusivity, electrical resistivity, Hall coefficients and Seebeck coefficients were measured as a function of temperature. The selenides were found to behave as degenerate semiconductors, with reasonable thermoelectric figure of merit (up to 0.79 in CuCrSe2), while the sulfides behaved as non-degenerate semiconductors with high electrical resistivity. At room temperature, all samples are in the ordered phase and show low lattice thermal conductivity ranging from 0.60 W m−1-K in AgCrSe2to 1.1 W m−1-K in CuCrSe2. Little reduction in lattice thermal conductivity was observed in the high-temperature phase, despite the increased disorder on the cation site and the onset of superionic conductivity. This suggests that the low lattice thermal conductivity inACrX2compounds is an inherent property of the crystal structure, caused by anharmonic bonding and diffuson dominated transport.
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- Award ID(s):
- 2118463
- PAR ID:
- 10601038
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Journal of Physics: Energy
- Volume:
- 7
- Issue:
- 3
- ISSN:
- 2515-7655
- Format(s):
- Medium: X Size: Article No. 035016
- Size(s):
- Article No. 035016
- Sponsoring Org:
- National Science Foundation
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