Electrochemical Impedance Analysis and Modeling of Electrolyte Supported Solid Oxide Fuel Cells with LSM Air Electrodes

Lanthanum strontium manganite (LSM)-based air electrodes are applied in solid oxide cells for high-temperature operations (800 °C–1000 °C), offering chemical and microstructural stability despite relatively lower performance. This work focuses on impedance study of hexis electrolyte supported cells with LSM air electrodes and Nickel/Gadolinia-doped Ceria (Ni/GDC) fuel electrodes. Electrochemical impedance spectroscopy and distribution of relaxation times (DRT) were employed to analyze performance-limiting processes in single cells with a 1 cm2 active electrode area. This analysis identified losses across five frequency ranges (5 DRT peaks), with no clear correlation to operating parameters. To deconvolute the processes and isolate loss mechanisms in both air and fuel electrodes, symmetrical cells were studied across a wide range of temperatures and air/fuel compositions. These measurements allowed for the separation of air and fuel electrode processes, development of a meaningful equivalent circuit model, and extraction of the model parameters using complex non-linear least squares fitting. These parameters were applied to build a 0-dimensional nonlinear DC performance model, which showed excellent agreement with the measured current-voltage data. ... mehrThe findings revealed that, in contrast to cells with mixed-conducting LSCF air electrodes, cell performance is limited by the LSM air electrode.