This thesis introduces (i) amendments to basic electrochemical measurement techniques in the time and frequency domain suitable for electrochemical energy conversion systems like fuel cells and batteries, which enable shorter measurement times and improved precision in both measurement and parameter identification, and (ii) a modeling approach that is able to simulate a technically relevant system just by information gained through static and impedance measurements of laboratory size cells.

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This work deals with microstructural characterisation, modelling and simulation of SOFC electrodes with the goal of optimizing the electrode microstructures. Methods for a detailed electrode analysis based on focused ion beam (FIB) tomography are presented. A 3D FEM model able to perform simulations of LSCF cathodes based on 3D tomography data is shown. A model generating realistic, yet synthetic microstructures is presented that enables the optimization of microstructural characteristics.

Solid oxide fuel cells offer great prospects for the sustainable, clean and safe conversion of various fuels into electrical energy. In this thesis, the performance-determining loss processes for the cell operation on reformate fuels are elucidated via electrochemical impedance spectroscopy. Model-based analyses reveal the electrochemical fuel oxidation mechanism, the coupling of fuel gas transport and reforming chemistry and the impact of fuel impurities on the degradation of each loss process.

In this book, a new procedure to analyze lithium-ion cells is introduced. The cells are disassembled to analyze their components in experimental cell housings. Then, Electrochemical Impedance Spectroscopy, time domain measurements and the Distribution function of Relaxation Times are applied to obtain a deep understanding of the relevant loss processes. This procedure yields a notable surplus of information about the electrode contributions to the overall internal resistance of the cell.

Mixed ionic-electronic conducting (MIEC) ceramics as oxygen transport membranes (OTMs) can provide high oxygen permeation rates at comparably low energy demands. For this purpose, Ba?.?Sr?.?Co?.?Fe?.?O??? (BSCF) shows the best performance under ideal operating conditions. Thermal and chemical stability investigations, electrical behavior ?(T,pO?,t), and oxygen exchange parameter extraction by means of electrical conductivity relaxation resulted in a far better understanding of the BSCF system.