Solid oxide fuel cells with zirconia/ceria bilayer electrolytes via roll calendering process

Solid oxide fuel cell (SOFC) with yttria-stabilized zirconia (YSZ)/gadolinium-doped ceria (GDC) bilayer electrolytes has been considered one of representative types of high-performance intermediate-temperature SOFCs, because it enables to apply highly active cathode materials. However, the processing of fully dense bilayer electrolytes with good interfacial structure, which are essential for high-performance and secure operation, has not yet been successfully achieved. Here, we present a simple and cost-effective roll calendering process for fabrication of SOFCs with YSZ/GDC bilayer electrolytes. From understanding on the correlation between processing conditions of roll calendering and microstructure of bilayer electrolytes, the roll calendering process is optimized, and in turn, the bilayer electrolytes with overall thickness of 8.0 μm, relative density above 98%, and enhanced interfacial connectivity of 69% is obtained by co-sintering at reduced temperature of 1250 °C. This excellent structural enhancement in comparison with conventional uniaxial pressing process is explained by a shear force applied during roll calendering process, which presumably facilitates particle rearrangement within bilayer electrolytes. The optimized cell yields promising electrochemical performance of 1.45 W/cm² at current density of 2 A/cm² and low ohmic resistance of 0.046 Ω cm² at 800 °C.