The influence of Li intercalation on the electric polarisability of oxides lattices determined by XPS

X-ray photoelectron spectroscopy (XPS) is known, mainly, as a technique for surface analysis. It is especially valued for interpretation of chemical state by means of the chemical shift. This paper concerns the contribution to this shift from polarization of the ligands following core photo-ionization. Intercalation of ions such as lithium will influence the electronic polarizability of the oxygen ions and hence the value of the Auger parameter (AP). The AP is the difference in kinetic energy of the Auger peak in the spectrum and that of the principal photoelectron peak, calculated by an internationally accepted procedure. Thus, whilst obtaining the composition and chemical state of a compound one can also determine the bulk polarisability of the material. Polarizability is crucial to the dielectric properties of oxides, such as refractive index and is of value in optimizing intercalation compounds for use in opto-electronic devices. The use of this methodology will be illustrated using the system Li/Ce2O3/V2O5. An in situ cell for electrochemical intercalation from organic electrolytes will be described.