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In this study, three different surface-sensitive techniques, grazing incidence X-ray diffraction (GIXD), attenuated total reflectance Fourier transform infrared (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS), were employed to analyze the local structure and composition around the surface region of a lithium ion conducting solid electrolyte sheet. It was revealed that the local structure and composition changed depending on depth from the top surface of the sheet. At the very surface, there was a layer with expanded lattice and high Li composition. And with increasing the depth from the surface, lattice shrank sharply, and then expanded again gradually. The change in the lattice seemed to be accompanied by Li and Al composition. It was supposed that the change in the Li composition and structure is induced by combination of chemical reaction, segregation, and defect distribution.

Nanocomposites of a lithium ion conductor Li1.3Al 0.3Ti1.7(PO4)3 and electrode materials (TiO2 and FePO4) were prepared to investigate interfacial structure and ionic conductivity at the interface between the solid electrolyte and electrode materials. It was revealed that lithium ions in the solid electrolyte were attracted to the cathode materials with increasing electrode potential, which increases lithium vacancies in the solid electrolyte. For the FePO4 containing composites, due to the high electrode potential, lithium transfer across the interface and ionic conduction through the cathode materials was remarkable. The results suggest that severe lithium depletion occurs and interfacial resistance is large at the interface of high ionic conductors and cathode materials. The space charge layer thickness is also discussed., Solid State Ionics, 262, pp.879-882; 2014