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 La0.62Li0.16TiO3 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.

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In the charge process of a fluoride-ion battery, LaNi5 as the cathode material is decomposed into LaF3 and Ni. The decomposition forms nano-scale networks of F−-ion and electron conduction paths, which helps to exploit a large amount of Ni.

The mixed-anion fluorosulfide Yb3F4S2 was examined as a solid electrolyte for all-solid-state fluoride-ion batteries. The synthesized Yb3F4S2 compound by solid-state reaction under vacuum contained Yb2O2S impurities, which originated from the starting materials. The conduction properties of Yb3F4S2 are discussed herein based on the electrochemical impedance and DC blocking measurements, which indicate mixed ionic and electrical conduction of Yb3F4S2. Yb L3-edge X-ray absorption measurements demonstrate the mixed valence state of ytterbium ion.