Impact of Leakage Current on Performance of Solid Oxide Fuel Cell Stacks with Gadolinia-Doped Ceria Electrolytes
The model incorporates both ionic and electronic current in the GDC electrolyte driving by the electrochemical gradient. The model employs irreversible electrodes and allows for a nonlinear potential distribution across the electrolyte to capture the distribution of oxygen defect concentrations following the work of Duncan et al3. In the current study, the model is used to analyze the relationship between leakage current and electrolyte thickness for a full stack cell wherein the conditions and effective oxygen partial pressure PO2 can vary significantly particularly in the anode channels. Figure 1 plots average ionic, electronic, and total current density as a function of cell voltage for a cell with a 20 µm GDC electrolyte operating at 600°C. OCV deviation from theoretical value due to electrode/electrolyte interfaces overpotentials and Ohmic losses contributed by the ionic and electronic current. The effect of the leakage current on stack performance and efficiency provides a basis for understanding how fuel oxidation due to the leakage current impacts the relationship between stack current and fuel utilization. Results provide guidance for designing high-performance intermediate-temperature SOFCs with GDC electrolytes.
1. S. Baron, N. Brandon, A. Atkinson, B. Steele, and R. Rudkin, Journal of Power Sources, 126(1-2), pp. 58-66 (2004).
2. T. Nakamura, T. Kobayashi, K. Yashiro, A. Kaimai, T. Otake, K. Sato, J. Mizusaki, and T. Kawada, Journal of the Electrochemical Society, 155(6), pp. B563-B569 (2008).