Characterization of electrode/electrolyte interface with X-ray reflectometry and epitaxial-film LiMnO electrode

Hirayama, Masaaki*; Sonoyama, Noriyuki*; Ito, Masumi*; Minoura, Machiko*; Mori, Daisuke*; Yamada, Atsuo*; Tamura, Kazuhisa   ; Mizuki, Junichiro; Kanno, Ryoji*

Structural changes at electrode/electrolyte interface of a lithium cell were studied by X-ray reflectometry and two-dimensional model electrodes with a restricted lattice plane of LiMnO. The ex situ reflectometry indicated that a thin impurity layer covered the lattice plane of the as-grown film. The impurity layer was dissolved and a solid-electrolyte-interface-like phase appeared after the electrode was soaked into the electrolyte. The in situ observation clarified that the surface reactivity depended on the lattice planes of the spinel; the defect layer at the (111) plane was stable during the electrochemical reaction, whereas a slight decrease in the film thickness was observed for the (110) plane. Our surface characterization of the intercalation electrode indicated that the surface structure changes during the pristine stage of the change-discharge processes and these changes are dependent on the lattice orientation of LiMnO.