Structural Investigation of Li<sub>2</sub>O–LiI Amorphous Solid Electrolytes
Yushi Fujita, Takuya Kimura, Minako Deguchi, Kota Motohashi, Atsushi Sakuda, Masahiro Tatsumisago, Hirofumi Tsukasaki, Shigeo Mori, Kazutaka Ikeda, Koji Ohara, Naoaki Kuwata, Koji Amezawa, Akitoshi Hayashi
Abstract
All-solid-state lithium-ion batteries with flame-retardant inorganic solid electrolytes are promising because of their safety. Oxide-based solid electrolytes are attractive, owing to their high chemical stability and lithium-ion conductivity. The development of new oxide-based solid electrolytes with high ionic conductivity and ductility is crucial for improving the overall performance of all-solid-state batteries. Recently, the synthesis of amorphous solid electrolytes using mechanochemical processes was explored. Among them, a Li 2 O–LiI amorphous solid electrolyte has been shown to have high ionic conductivity (10 –5 S cm –1 at 25 °C) and ductility comparable to those of sulfide solid electrolytes. However, the detailed structure and the ionic conduction mechanism of the Li 2 O–LiI electrolyte are not well understood. In this study, structural analysis of the Li 2 O–LiI electrolyte was conducted to elucidate its structure and conduction mechanism using neutron diffraction, transmission electron microscopy, 7 Li magic-angle spinning nuclear magnetic resonance, and X-ray photoelectron spectroscopy. These structural analyses suggested that the Li 2 O–LiI electrolyte was primarily composed of amorphous components, mainly iodide and oxide ions, with high ionic mobility. The results of this study are useful for the further development of oxide-based solid electrolytes.