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O: Oberflächenphysik
O 11: Elektronische Struktur I
O 11.2: Vortrag
Freitag, 4. März 2005, 16:00–16:15, TU EB420
Electronic structure of alkaliated transition metal oxides used as battery cathodes — •Andreas Thißen1, Francisco Javier Fernandez Madrigal1, Qi-Hui Wu2, Stefan Laubach3, Peter C. Schmidt3, and Wolfram Jaegermann1 — 1FB Material- und Geowissenschaften, FG Oberflächenforschung, TU Darmstadt, Petersenstr. 23, D-64287 Darmstadt — 2Lehrstuhl für Physikalische Chemie I, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum — 3FB Physikalische Chemie, FG Festkörpertheorie, TU Darmstadt, Petersenstr. 20, D-64287 Darmstadt
Electronic structure of (Li, Na)xV2O5 and (Li, Na)xCu2.33V4O11 has been studied by XPS, UPS, ResPES and XAS. V2O5 thin films have been prepared by PVD and RF magnetron sputtering. From ResPES partial valence band density of states has been derived, giving a V3d-admixture to the valence band of 12 percent, comparing well to recent DFT calculations. From that value real oxidation numbers are calculated to V+2.5 and O-1. Adsorption of lithium and sodium at room temperature leads to spontaneous intercalation until alkali saturation concentrations of Li2.4V2O5 and Na2V2O5 are reached. O.32 electrons per lithium and 0.42 electrons per sodium atom are transferred to V3d states, reducing the formal oxidation state of the V-ion from 5+ to 4+. The Fermi-level is shifted upwards due to the charge transfer and the V3d states are stabilized by localization indicating the breakdown of the rigid band model. A model is shown, to correlate the electronic structure to battery voltages against Li/Li+ from electrochemical measurements. This work is funded by DFG(SFB595), EU(INTERCALNET) and BMBF.