Ionic Pathways in Li13Si4 investigated by (6)Li and (7)Li solid state NMR experiments

Sven Dupke; Thorsten Langer; Florian Winter; Rainer Pöttgen; Martin Winter; Hellmut Eckert

doi:10.1016/j.ssnmr.2014.11.003

Ionic Pathways in Li13Si4 investigated by (6)Li and (7)Li solid state NMR experiments

Solid State Nucl Magn Reson. 2015 Feb:65:99-106. doi: 10.1016/j.ssnmr.2014.11.003. Epub 2014 Nov 29.

Authors

Sven Dupke¹, Thorsten Langer², Florian Winter², Rainer Pöttgen², Martin Winter¹, Hellmut Eckert³

Affiliations

¹ Institut für Physikalische Chemie, Universität Münster, Corrensstrasse 30, 48149 Münster, Germany.
² Institut für Anorganische und Analytische Chemie, Universität Münster, Corrensstrasse 30, 48149 Münster, Germany.
³ Institut für Physikalische Chemie, Universität Münster, Corrensstrasse 30, 48149 Münster, Germany; Institute of Physics in São Carlos, University of São Paulo, Av. Trabalhador Sãocarlense 400, 13590 São Carlos, SP, Brazil. Electronic address: eckerth@uni-muenster.de.

PMID: 25524128
DOI: 10.1016/j.ssnmr.2014.11.003

Abstract

Local environments and dynamics of lithium ions in the binary lithium silicide Li13Si4 have been studied by (6)Li MAS-NMR, (7)Li spin-lattice relaxation time and site-resolved (7)Li 2D exchange NMR measurements as a function of mixing time. Variable temperature experiments result in distinct differences in activation energies characterizing the transfer rates between the different lithium sites. Based on this information, a comprehensive picture of the preferred ionic transfer pathways in this silicide has been developed. With respect to local mobility, the results of the present study suggests the ordering Li6/Li7>Li5>Li1>Li4 >Li2/Li3. Mobility within the z=0.5 plane is distinctly higher than within the z=0 plane, and the ionic transfer between the planes is most facile via Li1/Li5 exchange. The lithium ionic mobility can be rationalized on the basis of the type of the coordinating silicide anions and the lithium-lithium distances within the structure. Lithium ions strongly interacting with the isolated Si(4-) anions have distinctly lower mobility than those the coordination of which is dominated by Si2(6-) dumbbells.

Keywords: 2D-exchange NMR; Li ion batteries; Li silicides; Spin-lattice relaxation; lithium ion conductors.

Publication types

Research Support, Non-U.S. Gov't