Elucidating reaction resistances in electrode-supported solid oxide cells using a nonlinear least-square model

To understand the physical meaning of each resistance in an electrode-supported solid oxide cell (ECS), a complex nonlinear least-square (CNLS) equivalent circuit was developed. The commercial type of ECS measured their electrochemical properties in various gas compositions (oxygen, hydrogen, and water vapor) and temperature. The obtained impedance spectra were analyzed using the distribution of relaxation times (DRT) method to deconvolute the resistance of the cell. Subsequently, the developed CNLS equivalent circuit was used to provide the physical meaning of each resistance. R-CPE was used to analyze gas conversion resistance, Warburg impedance was used to analyze gas diffusion at a very-low-frequency region, and Gerischer impedance was used to analyze electrode resistance. Finally, the model was validated by comparing the transport properties of the electrode obtained from the model with the reported data. Thus, the developed model could aid in understanding the physical meaning of each resistance of the cell.