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O: Oberflächenphysik

O 48: Oxide und Isolatoren II

O 48.7: Vortrag

Dienstag, 8. März 2005, 17:15–17:30, TU EB107

On the electronic structure of LiCoO2 and related compounds used as battery cathodes — •Thißen Andreas¹, David Ensling¹, Qi-Hui Wu², Francisco Javier Fernandez Madrigal¹, Stefan Laubach¹, Peter C. Schmidt¹, and Wolfram Jaegermann¹ — ¹FB Material- und Geowissenschaften, Fachgebiet Oberflächenforschung, TU Darmstadt, Petersenstr. 23, D-64287 Darmstadt — ²Lehrstuhl für Physikalische Chemie I, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum

Electronic structure of transition metal oxides is often discussed in terms of ionic bonding in a rigid band model. In this approach the introduction of electrons by alkaliation leads to filling of metal 3d states. In most cases those two approximations are too simple, because of polar-covalent bonding, electron correlation, localization, polaron formation and structural influences, like Madelung-potentials, ligand-field effects and Jahn-Teller-distortion. Stoichiometric, polycrystalline LiCoO2 thin films in the high temperature modification have been prepared by RF magnetron sputtering. From XPS data it has been shown, that the Co-ions are in the formal 3+ low-spin oxidation state. The interpretation of the ResPES data is complicated, because of ligand-hole screening effects. At the Co3p-3d threshold an anti-resonance occurs, from that the O2p and Co3d PVBDOS have been derived, showing good agreement with DFT calculations. Via the preparation of an all solid state micro-battery a route to in-situ measurements of the electronic structure as a function of the lithium content in parallel to electrochemical measurements is presented. This work is funded by DFG (SFB595) and BMBF.