Abstract
Argyrodite-type materials show very promising properties as solid electrolytes. Li6PS5X (X = Cl, Br, I) has attracted considerable interest and many groups tried to improve the already high ionic conductivity. Recent attempts explored the substitution of Phosphorus by Germanium, which allowed a higher Li-content in Li6PS5I.1 Substitution resulted in increased ionic conductivity, however, the origin of the faster ionic transport is not yet fully elucidated.
Here, we investigated ion dynamics in the substitution series Li6+xGexP1–xS5I (x = 0–0.6) by means of neutron powder diffraction and solid-state NMR. The diffraction data revealed the occupation of new Li-sites. Additional to the sites forming cage-like Li-structures in Li6PS5I, samples with a Ge-content of 30at% and 60at% accommodate also type 2 Li-sites close to the Li-cages and type 4 sites, placed in between the Li cages. The introduced site disorder is also directly sensed by high resolution 31P MAS NMR with increasing disorder for higher levels of substitution. 7Li NMR spin-lattice relaxation measurements point to correlated motion and allow the distinction of two different Li-jump processes. Experiments of 1/T1(1/T) characterized short-ranged motion with an activation energy of approximately 0.1 eV. This likely represents the intercage jumps of the Li+ ions. Complementary, spin-lock NMR experiments detecting slower dynamic processes reveal a second jump process characterized by a higher barrier, which we assign to exchange processes connecting the Li-rich cages. The corresponding rate peak is also observed for the unsubstituted Li6PS5I, however, shifted toward significantly higher temperatures. As revealed by NMR, Ge substitution clearly facilitates intercage ion dynamics that finally enable the ions to move over long distances in Li6+xGexP1–xS5I.
1. Minafra, N. et al., J. Mater. Chem. A 2018, 6, 645-651.
Here, we investigated ion dynamics in the substitution series Li6+xGexP1–xS5I (x = 0–0.6) by means of neutron powder diffraction and solid-state NMR. The diffraction data revealed the occupation of new Li-sites. Additional to the sites forming cage-like Li-structures in Li6PS5I, samples with a Ge-content of 30at% and 60at% accommodate also type 2 Li-sites close to the Li-cages and type 4 sites, placed in between the Li cages. The introduced site disorder is also directly sensed by high resolution 31P MAS NMR with increasing disorder for higher levels of substitution. 7Li NMR spin-lattice relaxation measurements point to correlated motion and allow the distinction of two different Li-jump processes. Experiments of 1/T1(1/T) characterized short-ranged motion with an activation energy of approximately 0.1 eV. This likely represents the intercage jumps of the Li+ ions. Complementary, spin-lock NMR experiments detecting slower dynamic processes reveal a second jump process characterized by a higher barrier, which we assign to exchange processes connecting the Li-rich cages. The corresponding rate peak is also observed for the unsubstituted Li6PS5I, however, shifted toward significantly higher temperatures. As revealed by NMR, Ge substitution clearly facilitates intercage ion dynamics that finally enable the ions to move over long distances in Li6+xGexP1–xS5I.
1. Minafra, N. et al., J. Mater. Chem. A 2018, 6, 645-651.
| Original language | English |
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| Publication status | Published - 15 Sept 2021 |
| Event | 2021 European Congress and Exhibition on Advanced Materials and Processes : EUROMAT 2021 - Virtuell, Virtuell, Austria Duration: 13 Sept 2021 → 17 Sept 2021 https://www.euromat2021.org/ |
Conference
| Conference | 2021 European Congress and Exhibition on Advanced Materials and Processes |
|---|---|
| Abbreviated title | EUROMAT 2021 |
| Country/Territory | Austria |
| City | Virtuell |
| Period | 13/09/21 → 17/09/21 |
| Internet address |