title: Crystal Structure of Garnet-Related Li-Ion Conductor Li7-3xGaxLa3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?
abstract: Li-oxide garnets such as Li7La3Zr2O12(LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space groupIa-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga3+shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characterization of Ga-stabilized LLZO is performed by means of single-crystal X-ray diffraction. Coarse-grained samples with crystal sizes of several hundred micrometers are obtained by solid-state reaction. Single-crystal X-ray diffraction results show that Li7-3xGaxLa3Zr2O12withx> 0.07 crystallizes in the acentric cubic space groupI-43d. This is the first definite record of this cubic modification for LLZO materials and might explain the superior electrochemical performance of Ga-stabilized LLZO compared to its Al-stabilized counterpart. The phase transition seems to be caused by the site preference of Ga3+.7Li NMR spectroscopy indicates an additional Li-ion diffusion process for LLZO with space groupI-43dcompared to space groupIa-3d. Despite all efforts undertaken to reveal structure-property relationships for this class of materials, this study highlights the potential for new discoveries.
authors.affiliation: Department of Chemistry and Physics of Materials, University of Salzburg , Hellbrunnerstrasse 34, 5020 Salzburg, Austria.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Wagner
authors.affiliation: Department of Chemistry and Physics of Materials, University of Salzburg , Hellbrunnerstrasse 34, 5020 Salzburg, Austria.
authors.forename: Günther J
authors.initials: GJ
authors.lastname: Redhammer
authors.affiliation: Department of Chemistry and Physics of Materials, University of Salzburg , Hellbrunnerstrasse 34, 5020 Salzburg, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rettenwander
authors.affiliation: Heinz Maier-Leibnitz Zentrum, Technische Universität München , Lichtenbergstrasse 1, 85748 Garching b. München, Germany.
authors.forename: Anatoliy
authors.initials: A
authors.lastname: Senyshyn
authors.affiliation: Institute for Chemistry and Technology of Materials, Graz University of Technology , Stremayrgasse 9, 8010 Graz, Austria.
authors.forename: Walter
authors.initials: W
authors.lastname: Schmidt
authors.affiliation: Institute for Chemistry and Technology of Materials, Graz University of Technology , Stremayrgasse 9, 8010 Graz, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Wilkening
authors.affiliation: Department of Chemistry and Physics of Materials, University of Salzburg , Hellbrunnerstrasse 34, 5020 Salzburg, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Amthauer