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DS: Fachverband Dünne Schichten

DS 20: Application of thin films

DS 20.4: Vortrag

Mittwoch, 28. März 2012, 10:15–10:30, H 0111

LTO and LFP Thin Film Electrodes — •Frank Berkemeier, Wunde Fabian, Köhler Mathias, and Schmitz Guido — Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm Str. 10, 48161 Münster, Germany

Thin films of lithium titanium oxide (LTO) and lithium iron oxide (LFP) were prepared by reactive ion beam sputtering, in a thickness between 50 and 500 nm. After preparation, the structure of the layers was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). To characterize the electrochemical properties of the layers, i.e. their capability to reversibly intercalate/deintercalate lithium, cyclic voltammetry (CV) and galvanostatic intermittent titration technique (GITT) was performed. It was found that in both cases, the electrochemical performance strongly depends on the conditions during sputtering, i.e. substrate temperature and oxygen partial pressure. When using optimum deposition conditions, reversible capacities of about 88 mAh/g (LTO) and 40 mAh/g (LFP) were found. Using LTO and LFP films that match each other with respect to their capacity, the electrochemical functionality of the films was demonstrated, combining both materials in a galvanostatic cell, and performing continuous CV measurements. In addition to these performance tests, the diffusion coefficient of lithium inside the films was determined by GITT, using thin film approach. Due to the well-defined thickness of the films, this approach can be used quite reliably, and shows in case of e.g. LTO that the diffusion coefficient of lithium only slightly depends on concentration within the regime of reversible cycling.