Impedance analysis of thin YSZ electrolyte for low-temperature solid oxide fuel cells

Solid oxide fuel cells based on yttria-stabilized zirconia materials have demonstrated a higher level of technology maturity compared to newer materials actively researched to lower the operating temperature. Yttria-stabilized zirconia-based cells can operate around 600 °C and achieve competitive power densities provided the electrolyte can be fabricated relatively thin. In this work, a 2.5-μm thick yttria-stabilized zirconia electrolyte, commercially available, anode-supported solid oxide fuel cell is systematically investigated under various electrochemical conditions, and area of improvements with the electrochemical performance are identified. The cell consists of a Ni-YSZ bulk and functional layer anode, YSZ electrolyte, GDC barrier layer, and LSCF cathode. Using humidified hydrogen, the peak power densities are determined to be 0.31, 0.58, 0.96, 1.41, and 1.78 W/cm2 at 600, 650, 700, 750, and 800 °C, respectively. It is found that the ceria barrier layer is porous; thus, it is not effective to avoid the formation of strontium zirconate. It is therefore expected that the performance can be improved further if a denser ceria barrier layer can be deposited. In addition, energy dispersive spectroscopy analysis revealed significant Ce/Zr interdiffusion between the barrier layer and the electrolyte.