Lithium atom and A-site vacancy distributions in lanthanum lithium titanate

Xiang Gao, Craig A.J. Fisher, Teiichi Kimura, Yumi H. Ikuhara, Hiroki Moriwake, Akihide Kuwabara, Hideki Oki, Takeshi Tojigamori, Rong Huang, Yuichi Ikuhara

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54 Citations (Scopus)

Abstract

Lanthanum lithium titanate (LLTO) is one of the most promising electrolyte materials for all-solid-state lithium-ion batteries. Despite numerous studies, the detailed crystal structure is still open to conjecture because of the difficulty of identifying precisely the positions of Li atoms and the distribution of intrinsic cation vacancies. Here we use subangstrom resolution scanning transmission electron microscopy (STEM) imaging methods and spatially resolved electron energy loss spectroscopy (EELS) analysis to examine the local atomic structure of LLTO. Direct annular bright-field (ABF) observations show Li locations on O4 window positions in Li-poor phase La0.62Li 0.16TiO3 and near to A-site positions in Li-rich phase La0.56Li0.33TiO3. Local clustering of A-site vacancies results in aggregation of Li atoms, enhanced octahedral tilting and distortion, formation of O vacancies, and partial Ti4+ reduction. The results suggest local LLTO structures depend on a balance between the distribution of A-site vacancies and the need to maintain interlayer charge neutrality. The associated local clustering of A-site vacancies and aggregation of Li atoms is expected to affect the Li-ion migration pathways, which change from two-dimensional in Li-poor LLTO to three-dimensional in Li-rich LLTO. This study demonstrates how a combination of advanced STEM and EELS analysis can provide critical insights into the atomic structure and crystal chemistry of solid ionic conductors.

Original languageEnglish
Pages (from-to)1607-1614
Number of pages8
JournalChemistry of Materials
Volume25
Issue number9
DOIs
Publication statusPublished - 2013 May 14
Externally publishedYes

Keywords

  • Li-ion battery
  • ionic conductor
  • scanning transmission electron microscopy
  • solid-state electrolyte
  • structure-property relationships

ASJC Scopus subject areas

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

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  • Cite this

    Gao, X., Fisher, C. A. J., Kimura, T., Ikuhara, Y. H., Moriwake, H., Kuwabara, A., Oki, H., Tojigamori, T., Huang, R., & Ikuhara, Y. (2013). Lithium atom and A-site vacancy distributions in lanthanum lithium titanate. Chemistry of Materials, 25(9), 1607-1614. https://doi.org/10.1021/cm3041357