Details
| Original language | English |
|---|---|
| Article number | 112193 |
| Journal | Materials research bulletin |
| Volume | 162 |
| Early online date | 16 Feb 2023 |
| Publication status | Published - Jun 2023 |
Abstract
The visualization of atomic or ionic jump processes on the Ångström length scale is important to identify the preferred diffusion pathways in solid electrolytes for energy storage devices. Two-dimensional high-resolution 6Li nuclear magnetic resonance (NMR) spectroscopy is highly suited to yield unprecedented site-specific insights into local Li+ exchange processes within a single measurement. Here, the beta-modification of Li3VF6 is used as a model system for such an investigation as it provides a range of important Li+ geometric environments in one and the same crystal structure useful to elucidate qualitatively a ranking of energetic preferences of the Li+ exchange processes. In Li3VF6 the Li+ ions are subject to diffusive exchange processes among five crystallographically and magnetically inequivalent Li sites: LiFn (n = 6, 4). By using a sample with a natural concentration of the 6Li isotope, we suppressed unwanted spin-diffusion processes and visualized the various exchange processes on the ms time scale. We were able to verify the following ranking experimentally: Li+ ion jumps between face-shared polyhedra are preferred, followed by Li+ exchange between edge-shared configurations for which interstitial sites are needed to jump from site to site. Surprisingly, Li+ exchange between corner-shared polyhedra and Li+ hopping involving almost isolated LiF4 polyhedra do contribute to overall Li+ self-diffusion as well. In this sense, the current study experimentally verifies current predictions by theory but also extends our understanding of ion dynamics between corner-shared Li-bearing polyhedra.
Keywords
- Cathode materials, Exchange processes, NMR, Self-diffusion
ASJC Scopus subject areas
- Materials Science(all)
- Physics and Astronomy(all)
- Condensed Matter Physics
- Engineering(all)
- Mechanics of Materials
- Engineering(all)
- Mechanical Engineering
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In: Materials research bulletin, Vol. 162, 112193, 06.2023.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Energetically preferred Li+ ion jump processes in crystalline solids
T2 - Site-specific hopping in β-Li3VF6 as revealed by high-resolution 6Li 2D EXSY NMR
AU - Bottke, Patrick
AU - Hogrefe, Katharina
AU - Kohl, Julia
AU - Nakhal, Suliman
AU - Wilkening, Alexandra
AU - Heitjans, Paul
AU - Lerch, Martin
AU - Wilkening, H. Martin R．
N1 - Funding Information: We thank the former DFG Research Unit 1277 for financial support. Moreover, financial support by the comet project safeLIB of the FFG ( Austrian Research Promotion Agency ) is highly acknowledged.
PY - 2023/6
Y1 - 2023/6
N2 - The visualization of atomic or ionic jump processes on the Ångström length scale is important to identify the preferred diffusion pathways in solid electrolytes for energy storage devices. Two-dimensional high-resolution 6Li nuclear magnetic resonance (NMR) spectroscopy is highly suited to yield unprecedented site-specific insights into local Li+ exchange processes within a single measurement. Here, the beta-modification of Li3VF6 is used as a model system for such an investigation as it provides a range of important Li+ geometric environments in one and the same crystal structure useful to elucidate qualitatively a ranking of energetic preferences of the Li+ exchange processes. In Li3VF6 the Li+ ions are subject to diffusive exchange processes among five crystallographically and magnetically inequivalent Li sites: LiFn (n = 6, 4). By using a sample with a natural concentration of the 6Li isotope, we suppressed unwanted spin-diffusion processes and visualized the various exchange processes on the ms time scale. We were able to verify the following ranking experimentally: Li+ ion jumps between face-shared polyhedra are preferred, followed by Li+ exchange between edge-shared configurations for which interstitial sites are needed to jump from site to site. Surprisingly, Li+ exchange between corner-shared polyhedra and Li+ hopping involving almost isolated LiF4 polyhedra do contribute to overall Li+ self-diffusion as well. In this sense, the current study experimentally verifies current predictions by theory but also extends our understanding of ion dynamics between corner-shared Li-bearing polyhedra.
AB - The visualization of atomic or ionic jump processes on the Ångström length scale is important to identify the preferred diffusion pathways in solid electrolytes for energy storage devices. Two-dimensional high-resolution 6Li nuclear magnetic resonance (NMR) spectroscopy is highly suited to yield unprecedented site-specific insights into local Li+ exchange processes within a single measurement. Here, the beta-modification of Li3VF6 is used as a model system for such an investigation as it provides a range of important Li+ geometric environments in one and the same crystal structure useful to elucidate qualitatively a ranking of energetic preferences of the Li+ exchange processes. In Li3VF6 the Li+ ions are subject to diffusive exchange processes among five crystallographically and magnetically inequivalent Li sites: LiFn (n = 6, 4). By using a sample with a natural concentration of the 6Li isotope, we suppressed unwanted spin-diffusion processes and visualized the various exchange processes on the ms time scale. We were able to verify the following ranking experimentally: Li+ ion jumps between face-shared polyhedra are preferred, followed by Li+ exchange between edge-shared configurations for which interstitial sites are needed to jump from site to site. Surprisingly, Li+ exchange between corner-shared polyhedra and Li+ hopping involving almost isolated LiF4 polyhedra do contribute to overall Li+ self-diffusion as well. In this sense, the current study experimentally verifies current predictions by theory but also extends our understanding of ion dynamics between corner-shared Li-bearing polyhedra.
KW - Cathode materials
KW - Exchange processes
KW - NMR
KW - Self-diffusion
UR - http://www.scopus.com/inward/record.url?scp=85148323031&partnerID=8YFLogxK
U2 - 10.1016/j.materresbull.2023.112193
DO - 10.1016/j.materresbull.2023.112193
M3 - Article
AN - SCOPUS:85148323031
VL - 162
JO - Materials research bulletin
JF - Materials research bulletin
SN - 0025-5408
M1 - 112193
ER -