Full Parametric Characterization of LSM/LSM-YSZ Cathodes by Electrochemical Impedance Spectroscopy

The contributions of the individual process steps of the cathode resistance were determined experimentally, directly from impedance spectra obtained from symmetrical cells. The symmetrical cells have architecture/structure consisting of YSZ electrolyte and a double layer cathode LSM-LSM/YSZ. The investigations were carried out in the temperature interval from 650 to 900(omicron)C. The cathode processes steps activation energies obtained were 1.16 eV, 1.1 eV, and 0.09 eV (diffusion), respectively, which is in relatively good agreement with literature values. To understand the role of layer cathode thickness on electrochemical performance, electrical impedance spectra from symmetric LSM/YSZ/LSM cells were deconvoluted to obtain the key electrochemical components of electrode performance, namely ohmic resistance (R-Omega), two low frequency processes related with chemical adsorption and dissociative reaction of O-2 (R-p1 and R-p2), and bulk gas diffusion (W, finite warburg) through the electrode pores. The model used has Voight structure with three times constant. These parameters were then related to features, such as contact layer thickness, function layer thickness, and temperature. It was found that polarization resistance is highly dependent on the thickness of the contact layer (R-p1 and R-p2). All deconvoluted parameters are validated by using the appropriate physicochemical model.