Crystal Structure of Garnet-Related Li-Ion Conductor Li7-3xGaxLa3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

Reinhard Wagner, Günther J. Redhammer, Daniel Rettenwander, Anatoliy Senyshyn, Walter Schmidt, Martin Wilkening, Georg Amthauer

Research output: Contribution to journalArticleResearchpeer-review

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 group Ia-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 Li7-3xGaxLa3Zr2O12 with x > 0.07 crystallizes in the acentric cubic space group I-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 group I-43d compared to space group Ia-3d. Despite all efforts undertaken to reveal structure-property relationships for this class of materials, this study highlights the potential for new discoveries.

Original languageEnglish
Pages (from-to)1861-1871
Number of pages11
JournalChemistry of Materials
Volume28
Issue number6
DOIs
Publication statusPublished - 22 Mar 2016

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ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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