Details
| Original language | English |
|---|---|
| Pages (from-to) | 28350-28360 |
| Number of pages | 11 |
| Journal | Journal of Physical Chemistry C |
| Volume | 118 |
| Issue number | 49 |
| Publication status | Published - 11 Dec 2014 |
Abstract
A comprehensive picture of the rather complex Li ion dynamics in the binary silicide Li12Si7 is presented. Long-range Li dynamics is probed by field gradient NMR methods. The obtained macroscopic tracer-diffusion coefficients are in good agreement with a jump process characterized by an activation energy of approximately 0.2 eV which was previously measured in 7Li NMR relaxometry-a microscopic method which probes ion dynamics on an atomic scale. From high-resolution magic-angle spinning (MAS) NMR, it can be concluded that 9 of the 13 crystallographically independent sites take part in this fast diffusion process. Li ions on the residual four sites are bound more tightly to the silicide Zintl anions with activation barriers ranging from 0.32 to 0.55 eV. Accordingly, the mean residence times of Li ions on these sites are considerably longer, which makes it possible to test their dynamics with 1D/2D MAS exchange NMR methods. We present a series of mixing-time-dependent 2D MAS exchange NMR measurements. The extracted Li jump rates are in very good agreement with those of dynamic processes investigated by NMR relaxometry. The data is interpreted in relation to the results of two recently published NMR studies on Li12Si7 and structural assignments based on one- and two-dimensional 29Si{7Li} heteronuclear correlation spectroscopy. These experiments assist in attributing different ionic mobilities to the different crystallographic lithium sites, suggesting preferred ion conduction pathways. Combining all these methods and their respective results, a consistent picture of the Li ion dynamics in Li12Si7 is obtained. Overall lithium species in the vicinity of the Si4 star unit tend to be more mobile than lithium species interacting with the Si5 ring units of the silicon framework structure.
ASJC Scopus subject areas
- Materials Science(all)
- Electronic, Optical and Magnetic Materials
- Energy(all)
- General Energy
- Chemistry(all)
- Physical and Theoretical Chemistry
- Materials Science(all)
- Surfaces, Coatings and Films
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In: Journal of Physical Chemistry C, Vol. 118, No. 49, 11.12.2014, p. 28350-28360.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Insight into the Li ion dynamics in Li12Si7
T2 - Combining Field gradient nuclear magnetic resonance, one- and two-dimensional magic-angle spinning nuclear magnetic resonance, and nuclear magnetic resonance relaxometry
AU - Kuhn, Alexander
AU - Dupke, Sven
AU - Kunze, Miriam
AU - Puravankara, Sreeraj
AU - Langer, Thorsten
AU - Pöttgen, Rainer
AU - Winter, Martin
AU - Wiemhöfer, Hans Dieter
AU - Eckert, Hellmut
AU - Heitjans, Paul
N1 - Publisher Copyright: © 2014 American Chemical Society.
PY - 2014/12/11
Y1 - 2014/12/11
N2 - A comprehensive picture of the rather complex Li ion dynamics in the binary silicide Li12Si7 is presented. Long-range Li dynamics is probed by field gradient NMR methods. The obtained macroscopic tracer-diffusion coefficients are in good agreement with a jump process characterized by an activation energy of approximately 0.2 eV which was previously measured in 7Li NMR relaxometry-a microscopic method which probes ion dynamics on an atomic scale. From high-resolution magic-angle spinning (MAS) NMR, it can be concluded that 9 of the 13 crystallographically independent sites take part in this fast diffusion process. Li ions on the residual four sites are bound more tightly to the silicide Zintl anions with activation barriers ranging from 0.32 to 0.55 eV. Accordingly, the mean residence times of Li ions on these sites are considerably longer, which makes it possible to test their dynamics with 1D/2D MAS exchange NMR methods. We present a series of mixing-time-dependent 2D MAS exchange NMR measurements. The extracted Li jump rates are in very good agreement with those of dynamic processes investigated by NMR relaxometry. The data is interpreted in relation to the results of two recently published NMR studies on Li12Si7 and structural assignments based on one- and two-dimensional 29Si{7Li} heteronuclear correlation spectroscopy. These experiments assist in attributing different ionic mobilities to the different crystallographic lithium sites, suggesting preferred ion conduction pathways. Combining all these methods and their respective results, a consistent picture of the Li ion dynamics in Li12Si7 is obtained. Overall lithium species in the vicinity of the Si4 star unit tend to be more mobile than lithium species interacting with the Si5 ring units of the silicon framework structure.
AB - A comprehensive picture of the rather complex Li ion dynamics in the binary silicide Li12Si7 is presented. Long-range Li dynamics is probed by field gradient NMR methods. The obtained macroscopic tracer-diffusion coefficients are in good agreement with a jump process characterized by an activation energy of approximately 0.2 eV which was previously measured in 7Li NMR relaxometry-a microscopic method which probes ion dynamics on an atomic scale. From high-resolution magic-angle spinning (MAS) NMR, it can be concluded that 9 of the 13 crystallographically independent sites take part in this fast diffusion process. Li ions on the residual four sites are bound more tightly to the silicide Zintl anions with activation barriers ranging from 0.32 to 0.55 eV. Accordingly, the mean residence times of Li ions on these sites are considerably longer, which makes it possible to test their dynamics with 1D/2D MAS exchange NMR methods. We present a series of mixing-time-dependent 2D MAS exchange NMR measurements. The extracted Li jump rates are in very good agreement with those of dynamic processes investigated by NMR relaxometry. The data is interpreted in relation to the results of two recently published NMR studies on Li12Si7 and structural assignments based on one- and two-dimensional 29Si{7Li} heteronuclear correlation spectroscopy. These experiments assist in attributing different ionic mobilities to the different crystallographic lithium sites, suggesting preferred ion conduction pathways. Combining all these methods and their respective results, a consistent picture of the Li ion dynamics in Li12Si7 is obtained. Overall lithium species in the vicinity of the Si4 star unit tend to be more mobile than lithium species interacting with the Si5 ring units of the silicon framework structure.
UR - http://www.scopus.com/inward/record.url?scp=84949117491&partnerID=8YFLogxK
U2 - 10.1021/jp505386u
DO - 10.1021/jp505386u
M3 - Article
AN - SCOPUS:84949117491
VL - 118
SP - 28350
EP - 28360
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 49
ER -