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 LiMn2O4. The electrodes were constructed with an epitaxial film synthesized by the pulsed laser deposition method. The orientation of the film depends on the substrate plane; the (111), (110), and (100) planes of LiMn2O4 grew on the (111), (110), and (100) planes of the SrTiO3 substrates, respectively. 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. A defect layer was formed in the (111) plane, whereas no density changes were detected for the other lattice planes. 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 LiMn2O4.
The interfacial structures of Ag bilayer prepared by underpotential deposition on Au(111) (Ag(2ML)/Au(111)) were determined by ex situ scanning tunneling microscopy and in situ surface X-ray scattering measurements before and after oxidative adsorption and after reductive desorption of a self-assembled monolayer (SAM) of hexanethiol (C(6)SH) in alkaline ethanol solution. While no structural change was observed after oxidative formation of C(6)SH SAM on the Ag(2ML)/Au(111) in an ethanol solution containing 20 mM KOH and 0.1 mM C(6)SH, some of the Ag atoms in the bilayer were stripped when the SAM was reductively desorbed.
An in situ experimental technique was developed for detecting structure changes at the electrode/electrolyte interface of lithium cell using synchrotron X-ray reflectometry and two-dimensional model electrodes with a restricted lattice plane. The electrode was constructed with an epitaxial film of LiNi0.8Co0.2O2 synthesized by the pulsed laser deposition method. The orientation of the epitaxial film depends on the substrate plane; the 2D layer of LiNi0.8Co0.2O2 is parallel to the SrTiO3 (1 1 1) substrate ((0 0 3)(LiCo0.2Ni0.8O2)//(1 1 1)SrTiO3 while the 2D layer is perpendicular to the SrTiO3 (1 1 0) substrate ((1 1 0)LiCO0.2Ni0.8O2//(1 1 0)SrTiO3). These films provided an ideal reaction field suitable for detecting structure changes at the electrode/electrolyte interface during the electrochemical reaction. The X-ray reflectometry indicated a formation of a thin-film layer at the LiCO0.2Ni0.8O2 (1 1 0)/electrolyte interface during the first charge-discharge cycle, while the LiNi0.8Co0.2O2 (0 0 3) surface showed an increase in the surface roughness without forming the surface thin-film layer. The reaction mechanism at the electrode/electrolyte interface is discussed based on our new experimental technique for lithium batteries. (C) 2007 Elsevier Ltd. All rights reserved.
The fruitful and remarkable research results in materials science during the past more than ten years have been continuously obtained by the advent of synchrotron radiation (SR) sources, especially the third-generation SR source. This is easily understood by considering that the SR beams provide not only five to ten orders of magnitude brilliance more in the continuum vacuum ultraviolet and X-ray regions of the electromagnetic spectrum than conventional sources, but also natural collimation, high polarization, pulsed time structure and high stability. In this paper we present a brief history of SR sources, especially in Japan to know how the SR sources developed, and a view of the future research direction regarding the use of SR beams.
The epitaxial growth and formation mechanism of the partially La- and Nd-substituted perovskite structures, and the ferroelectric properties of bismuth lanthanoid nickel titanate [(Bi1-xLax)(Ni0.5Ti0.5)O-3; BLNT and (Bi1-xNdx)(Ni0.5Ti0.5)O-3; BNNT] based solid solution films deposited on Pt(100)/MgO(100) substrates by rf sputtering have been investigated using X-ray diffraction. transmission electron microscope, and polarization-electric field hysteresis loop measurements. BLNT samples at x >= 0.3 and BNNT samples at x >= 0.4 were confirmed to have a single-phase perovskite structure. This small difference is speculated that it is related to metal-oxygen bond dissociation energy. The sample substituted with La exhibited the best hysteresis loop at x = 0.5 with a remanent polarization of P, = 12 mu C/cm(2) and the sample substituted by Nd exhibited the best hysteresis loop at x = 0.4 with a remanent polarization Of P-r = 2 mu C/cm(2).