Regensburg 2010 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 57: Topical Session Battery Materials III
MM 57.5: Talk
Thursday, March 25, 2010, 15:15–15:30, H6
Valence states and surface/interface reactions in Li-ion battery cathodes — •Gennady Cherkashinin1, David Ensling1, Stefan Schmid1, Jie Song1, Susanne Jacke1, Renè Hausbrand1, Kristian Nikolowski2, Helmut Ehrenberg2, and Wolfram Jaegermann1 — 1Department of Materials Science, Surface Science Institute, Darmstadt University of Technology, Darmstadt 64283, Germany — 2IFW Dresden, Institute for Complex Materials, Germany
Surface electronic properties of promising Li-Ion cathode materials such as LiMO2 (Ni, Co, Mn) as well as evolution of electrolyte-cathode interfaces formed after contact to the electrolyte, due to electrochemical charging and after cycling were systematically studied using XPS, UPS and synchrotron photoelectron spectroscopy (SXPS, XAS). To study fundamental surface properties of the oxides we investigated both thin film cathodes in-situ, whose surfaces are not contaminated by impurities, and synthesized powder cathodes used in industry. For LiMO2 (Ni, Co, Mn) cathodes, we have found that contact of the cathodes to the electrolyte results in the loss of lattice lithium and in the formation of a solid electrolyte interface (SEI) layer consisting of Li2CO3, LixOy, LiF (if LiPF6-electrolyte is used) and other species. For oxides containing Ni3+, we observe a Ni3+ to Ni2+ reduction. Charging of Lix(M)O2 (M=Co,Ni) does not only lead to Co3+ to Co4+ oxidation but also to oxygen deficiency. We detect no oxygen site participation in the charge compensation at the initial stage of the Li-de-intercalation.