Solid Oxide Cell Systems Evaluation

Abstract

The focus of this activity is performance assessment of single electrode-supported cells operating in the electrolysis mode. Single-cell testing provides basic information on initial and long-term cell performance without the complications present in a stack configuration such as contact resistance interconnect corrosion, Cr migration, etc. In the fuel cell mode, anode-supported cells represent the state-of-the-art in terms of performance. Since the electrolyte generally represents the highest resistivity layer in the cell, decreasing its thickness can lead to significantly improved performance. The Ni cermet material (anode in the fuel cell mode, cathode in the electrolysis mode) has relatively high electronic conductivity and is therefore a logical choice for use as the mechanical support layer in electrode-supported cells. In an anode-supported SOFC, the anode is typically 1 to 1.5 mm thick, while the electrolyte can be as thin as 10 µm. Three types of single cells were provided during FY-11. The oxygen-side electrode material for the baseline cells is La-Sr manganite (LSM). Two other air electrode materials were also provided: modified LSM and LSCF. The air electrode layer is screen printed on the cells, with a thickness of about 90 µm. The cells were fabricated by St. Gobain High-Performance Materials, and supplied to INL via a CRADA agreement. The St. Gobain cell design has in turn been licensed from the Jülich Institute for Energy Research. Testing activities for the St. Gobain cells are limited to INL since INL does not have a subcontract with St. Gobain. A photograph of one of the single cells is provided in Figure I-1. The green layer is the unreduced Ni cermet material. After reduction, the green NiO in this layer is converted to Ni metal and the layer color changes to silver gray. Typical layer dimensions for Ceramatec electrolyte-supported cells and St. Gobain/Jülich electrode-supported cells are presented in Table I-1.