Model of infiltrated La1−Sr Co1−Fe O3− cathodes for intermediate temperature solid oxide fuel cells

We consider an LSCF (La 1− x Sr x Co 1− y Fe y O 3− δ ) cathode formed of straight fibers. Being LSCF a mixed ionic electronic conductor (MIEC), we consider that it features two separate charge conduction paths, one for electrons and one for oxygen-ions. Infiltrated dopant particles, adherent to the LSCF fibers, create contact points between the ionic and the electronic conductive paths, among which, otherwise, the charge transfer reaction would be negligible. Based on this picture of the doped LSCF electrode, a model is developed. The model includes the evaluation of (i) electron and oxygen-ion conduction along the LSCF fiber, and (ii) charge transfer reaction occurring at the doping particles and, possibly, at the electrode/electrolyte interface. The model is applied to infiltrated cathodes based on different LSCF scaffolds, and the results are compared to literature experimental data, demonstrating good agreement. In particular, the model captures well the improvement of performance of the doped electrodes over the undoped ones, which can be five to tenfold or even more, and can bring the 1/ R p values to the order of magnitude of 10 5  S m −2 at 1000 K. Deviations between model results and literature experimental data at high doping levels are discussed in terms of percolation and partial pore obstruction.