Anode-Supported Solid Oxide Fuel Cells Fabricated By Single-Step Reduced-Temperature Co-Firing

Anode-supported solid oxide fuel cells (SOFCs) consisting of NiO-Y_0.16Zr_0.92O_2-δ (YSZ) anode support layer, NiO-YSZ anode functional layer, YSZ electrolyte and (La_0.8Sr_0.2)_0.98MnO_3-δ (LSM)-YSZ cathode were successfully fabricated by single-step co-firing at 1250^oC, 150^oC lower than the usual 1400^oC, with the addition of 1mol% Fe₂O₃ as sintering aid. Two different ceramic processing strategies - tape casting and colloidal deposition - were utilized for the fabrication. For the colloidally deposited cells, open-circuit voltages (OCVs) were near theoretical values for all cells. The cell yields maximum power density of 975 mW/cm² and area specific resistance of 0.34 Wcm² at 800^oC.  For the tape casted cells, a replica technique utilizing a graphite layer was incorporated to protect the cell during lamination, which improved the cell performance with maximum power density from 325 mW/cm² to 650 mW/cm² at 800^oC. The effect of oxygen partial pressures on the cathode performance and hydrogen partial pressures on the anode performance was investigated using electrochemical impedance spectroscopy (EIS), and the results on the main limiting mechanisms will be discussed. Scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDS) showed no element transport between each layer during sintering process. The correlation between electrode microstructure and cell performance will be discussed.

Single-step firing is interesting in general to reduce the number of cell processing steps, but is also interesting for fabricating entire stack structures that can be co-fired together. Preliminary results will be presented on single-step reduced-temperature co-firing of stack structures fabricated by a combination of tape casting and direct ink write three-dimensional (3-D) printing.