Differential impedance study of solid oxide fuel cell composite cathodes

A comparative impedance study of pure LSM (La1-xSrx)yMnO3-? with x = 0.25 and y = 0.95) and composite LSM/Y5Z (ZrO2-8 mol.% Y2O3) cathode materials for SOFC is performed. The technique of the Differential Impedance Analysis (DIA), which ensures structural identification without any preliminary hypothesis, is applied to the data analysis. It identifies three steps, determines quantitatively their participation and thus recognizes the rate-limiting step. It is found that the main contribution to the polarization resistance is due to transport limitations. The results obtained by DIA show that the improvement of the LSM/YSZ material for low temperature applications should concern both the ionic and the electronic conductivity.