Towards Quantification of Relations Between Electrode Polarisation and Microstructure

The total cell resistances of three Riso DTU solid oxide fuel cells (SOFCs) were broken down into individual contributions, by the combined use of electrochemical impedance spectroscopy (EIS), and complex non-linear least squares fitting (CNLS). Information on the number of contributing processes, frequency regions, and thermal behaviour, was obtained from symmetric cell studies of individual electrodes. The frequency regions dominated by electrode specific processes in the full cells were assessed by systematic changes of temperature and/or partial pressure of reactant gases on both electrodes. Based on the combined information, an equivalent circuit consisting of a series resistance (R-s) and five (RQ) elements was found suitable to describe the polarisation resistance of all tested cells. The breakdown process also allowed the assessment of limitations, and possible simplifications. The proposed electrochemical analysis correlated well with the exhibited microstructural features of the cells, which were produced with different compositions and/or production parameters. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3587113] All rights reserved.