Characterization of electrode/electrolyte interface for lithium batteries using in situ synchrotron X-ray reflectometry -: A new experimental technique for LiCoO2 model electrode

A new experimental technique was developed for detecting structure changes at electrode/electrolyte interface of lithium cell using X-ray reflectometry and two-dimensional model electrodes with a restricted lattice-plane. The electrodes were constructed with an epitaxial film of LiCoO2, synthesized by pulsed laser deposition method. The orientation of the epitaxial film depends on the substrate plane; the 2D layer of LiCoO2, is parallel to the SrTiO3 (1 1 1) substrate ((0 0 3)(LiCoO2/)//(1 1 1)(SrTiO3)), while the 2D layer is perpendicular to the SrTiO3 (1 1 0) substrate ((1 1 0)(LiCoO2)//(1 1 0)(SrTiO3)). The anisotropic properties were confirmed by electrochemical measurements. Ex situ X-ray reflectivity measurements indicated that the impurity layer existed on the as-grown LiCoO2 was dissolved and a new SEI layer with lower density was formed after soaking into the electrolyte. In situ X-ray reflectivity measurements indicated that the surface roughness of the intercalation (1 1 0) plane increased with applying voltages, while no significant changes in surface morphology were observed for the intercalation non-active (0 0 3) plane during the pristine stage of the charge-discharge process. (C) 2007 Elsevier B.V. All rights reserved.