Abstract
Solid-state batteries offer improved safety and higher energy density compared to conventional lithium-ion systems. Among candidate solid electrolytes, lithium argyrodites stand out for their exceptional ionic conductivity and compositional flexibility. Recent studies have revealed strongly anharmonic, liquid-like ion and lattice dynamics in these materials, including the collapse of soft phonons driven by Li+ diffusion, which impacts both local vibrations and thermal transport. Yet, the connection between the local structure, phonon dynamics, and macroscopic heat transport remains unresolved. In this work, we employ post-synthesis processing to tune microstructural parameters—such as crystallite size, strain, and coherence length—in two model systems: Li5.5PS4.5Cl1.5 and Li6PS5Br. We systematically examine how mechanical treatments influence structural coherence, ion and lattice dynamics, and thermal transport. To further probe the role of structural disorder, we investigate bromide substitution in Li6PS5I. Across all compounds, thermal transport above 100 K is dominated by diffusons. At lower temperatures, however, structural disorder is significantly more effective than reduced coherence length at suppressing phonon-gas-type transport, underscoring the crucial role of the local structure. Together with a detailed analysis of lithium-ion dynamics, these results provide new insights into how structural coherence and disorder govern both transport and vibrational properties in fast ionic conductors.
| Original language | English |
|---|---|
| Pages (from-to) | 39211-39228 |
| Number of pages | 18 |
| Journal | Journal of Materials Chemistry A |
| Volume | 13 |
| Issue number | 45 |
| DOIs | |
| State | Published - Dec 7 2025 |
Funding
This study was funded by the European Union (ERC, DIONISOS, 101123802). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. The research was supported by the International Graduate School for Battery Chemistry, Characterization, Analysis, Recycling and Application (BACCARA), which is funded by the Ministry for Culture and Science of North Rhine-Westphalia, Germany. The simulations for this work were performed on the computer cluster PALMA II at the University of Münster. The authors further acknowledge funding from the Deutsche Forschungsgemeinschaft under project number 459785385. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The beam time was allocated to BASIS, ARCS, and POWGEN on proposal numbers IPTS-32496, IPTS-32542, and IPTS-34157, respectively. The authors acknowledge Institut Laue-Langevin for time on the D2B beamline under the proposal 5-22-824. Additionally, the authors thank Alexander Sobolev, Martin Lange, and Bianca Helm for assistance at Institut Laue-Langevin.