Design and fabrication of segmented-in-series cells

This paper describes design calculations for and experimental fabrication of patterned series-connected solid oxide fuel cells (SOFCs), i.e. the "segmented-in-series" configuration. Losses due to cell resistances, electrode ohmic resistances, interconnect resistance, and shunting by a weakly-conductive support material were considered in the calculation. For any given set of cell dimensions and characteristics, power density was maximized at an optimal cell length. Assuming typical SOFC materials and screen printed layer geometries, optimal cell lengths typically ranged from 1 to 3 mm. Shunting currents increased with decreasing cell lengths, but were found to have little effect on power density assuming partially-stabilized zirconia supports and temperatures ≤ 800°C. Screen printed 4-cell arrays with ceramic interconnects and active cell lengths of 1.1 mm were fabricated, and produced > 0.6 W/cm² at 800°C. However, OCV values were only ≈ 0.7 V/cell due to porosity in the interconnect; this must be improved to realize good device performance.