Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 45: Electronic structure I

O 45.6: Vortrag

Mittwoch, 24. März 2010, 11:45–12:00, H33

Cobalt/nickel mixed oxides - cathode materials for Li-Ion-Batteries — •Stephan Schmidt and Dieter Schmeisser — Brandenburgische Technische Universität Cottbus, Konrad-Wachsmann-Allee 17, 03046 Cottbus

Replacing Co by large amounts of Ni is considered to reduce costs in Li-Ion-Batteries while maintaining their performance. We are interested in whether this replacement causes changes in the valence band (VB) and conduction band (CB) states or not.
Samples were prepared as thin films from nitrate solutions on metal substrates and annealed in air and UHV. The Co to Ni ratio was varied from 50/50 over 40/60 and 30/70 up to 20/80. The results are compared to the pure Co-oxide. Experiments were carried out at the U49/2 beamline at BESSYII, Berlin.
XPS of the TM2p states reveals the existence of charge transfer ground states and different oxidation states. NEXAS at the Co2p, Ni2p and O1s edges projects the density of unoccupied states while resonant PES at these edges provides the related partial density of states (pDOS) and thus can be used to distinguish between the different contributions of TM3d and O2p states in the valence band region.
We find systematic variation of the VB structure, the valence band maximum and a shift at the O1s absorption edge while the TM2p XPS and absorption spectra do not seem to be affected by the mixing.