Jeffery J. Haslam

Development and Characterization of a High Performance Thin-Film Planar SOFC Stack

A planar solid oxide fuel cell (SOFC) was fabricated using a tape-cast Ni/yttria-stabilized zirconia (YSZ) anode support, a YSZ thin-film electrolyte, and a composite cathode of YSZ and (La 0 . 8 5 Sr 0 . 1 4 ) 0 . 9 8 MnO 3 (LSM). Using pure hydrogen as the fuel gas, a three-cell stack with a cross-flow design and external manifolds produced peak power densities of 0.85 and 0.41 W/cm 2 at 800 and 700°C, respectively. Using wet methane as the fuel gas, the stack produced a peak power density of 0.22 W/cm 2 at 700°C. Individual cells in the stack showed identical current-voltage characteristics. Stack lifetime was limited because of degradation of the cells from oxidation products coming from the metallic interconnect used.

Influence of Electrode Configuration on the Performance of Electrode-Supported Solid Oxide Fuel Cells

The effect of the cathode-to-anode area ratio on the normalized power density for solid oxide fuel cells was investigated. A geometrically symmetric cell having a screen printed cathode produced a power density of 0.45 W/cm 2 at 800°C. However, using a cathode with a geometric area significantly less than that of the anode can enhance the normalized power density by a factor of two. Furthermore, using a current collector with a geometric area less than that of the cathode contributes an additional enhancement that leads to an apparent power density of 1.2 W/cm 2 . This difference in cell performance is interpreted as an artifact of normalization. When the performance of the cathode is improved using optimized processing technology and careful control of electrode microstructure, the effect of the area ratio on the normalized power density enhancement is less pronounced. Only testing in a symmetric cell configuration can result in power densities that are also achievable in stacks.