Berlin 2012 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 32: Functional Materials IV

MM 32.2: Vortrag

Mittwoch, 28. März 2012, 11:45–12:00, H 0106

TEM on electrochemically cycled thin film electrodes — •Tobias Gallasch, Frank Berkemeier, and Guido Schmitz — Institut für Materialphysik, Westfälische Wilhlems-Universität, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany

Thin film electrodes (150 nm) of well known Li intercalation materials, such as LiCoO₂ and V₂O₅ are prepared by ion beam sputtering. XRD, analytical TEM (TEM/EELS) and conductivity measurements were employed to carefully optimize the sputter parameters. The functional efficiency of the thin films as battery material was verified in detailed Cyclic Voltammetry and Chrono-Potentiometry studies. In the case of V₂O₅ thin films high capacities (300 mAh/g after 25 voltammetric cycles) and high cycling stabilities (250 mAh/g at constant current, 1C) are found which are in the range of the theoretical capacity (400 mAh/g).

In contrast to conventional capacity studies at bulk material, we provide a model system with defined geometry which allows investigating fundamental Li transport and electrode aging processes on smallest length scales. Special focus is therefore dedicated to electron energy loss-spectroscopy (EELS) which is demonstrated to be sensitive to even minor changes in composition. V₂O₅ thin films show a crystalline to amorphous transition during cycling which is studied in detail by analytical and high resolution TEM. The goal of this work is the combination of both, electrochemical and structural data to obtain information about Li transport mechanisms which are of fundamental interest in this field.