Electrochemical impedance spectroscopy of LSM|YSZ|LSM symmetric cells with varying geometric conditions

Abstract Electrochemical impedance spectroscopy (EIS) is a powerful tool for understanding the oxygen reduction reaction in solid oxide fuel cell cathodes. The cathodic impedance response is strongly affected by experimental variables such as geometric and thermal conditions. The impedance behavior of La 0.8 Sr 0.2 MnO 3-δ (LSM)|yttria-stabilized zirconia (YSZ)|LSM symmetric cells was investigated with electrode diameter and thickness, electrolyte thickness, and reference electrode (RE) configuration. When the electrode diameter increased from 5 mm to 15 mm, the average polarization resistance changed from 12.8056 to 12.6822 Ω cm 2 , while the standard deviation decreased from 0.3877 to 0.1734, suggesting that electrode area mismatch may have influenced the measurement consistency. For the electrode thickness, the most stable impedance response was observed at 20 μm (average: 12.6822 Ω cm 2 ; standard deviation: 0.1734), compared to 30 μm (average: 15.4541 Ω cm 2 ; standard deviation: 1.6038) and 10 μm (average: 14.3421 Ω cm 2 ; standard deviation: 0.7406). These variations are attributed to a decrease in open porosity at higher thickness and structural discontinuity or poor interfacial adhesion at lower thickness. Electrolyte thickness and RE configuration also affected the impedance behavior. The validity of the impedance measurements was confirmed through interlaboratory testing (ILT) with the optimized conditions.