Solid oxide cells (SOCs) are a promising technology for energy storage and conversion due to their 
high efficiency. However, their commercialization is hindered by insufficient performance and long￾term durability. While material development is active, elucidating the precise mechanisms of electrode 
degradation remains a critical challenge. This study proposes a polarization modeling approach that 
simultaneously fits current-voltage (I-V) curves and electrochemical impedance spectroscopy (EIS)
data. This method allows for the in-situ diagnosis of electrode degradation during operation, avoiding 
the limitations of post-mortem analysis. The method was validated through actual cell operation during 
long-term electrolysis galvanostatic operation (-1A/cm2) for 506 hours. At 207 hours, fuel cell (FC) 
performance improvement was attributed to air electrode activation (increase in air electrode exchange 
current density,