Lower Cost Stabilized Cathode

The stabilized cathode was developed to inhibit NiO dissolution which could result in cell shorting at target operational times and pressures for commercial MCFC stacks. Reduced NiO dissolution for cells operated with stabilized cathodes has been demonstrated in several atmospheric and pressurized bench-scale cell tests. The initial version of the stabilized cathode tripled the base cost of the cathode due to raw material processing requirements.

In the past two years, a stabilized cathode has been developed with a base material cost comparable to the unstabilized cathode: the lower-cost stabilized cathode has a raw material cost 6 percent lower than the current state-of-the-art unstabilized cathode, and 69% lower than the initial version of the stabilized cathode. In addition to the reduction in raw material costs, commercial-area manufacturing trials indicate that the lower cost stabilized cathode will have higher production yields than the initial version because of increased strength in the sintered state. Current results indicate further cost reductions are possible.

A 100-cm2 cell test of the lower cost stabilized cathode with the Li/Na electrolyte system completed 10,000 hours of operation, including more than a year of operation at pressurized systems conditions. The test operated with negligible decay (Figure 1), and was terminated only after repeated uncontrolled thermal cycles to 150 °C which resulted from facility power outages.

Li/Na ELECTROLYTE SYSTEM

The lithium/sodium (Li/Na) electrolyte system is being tested because of its high ionic conductivity which results in higher cell performances observed as a direct result of lower internal cell resistance. The Li/Na electrolyte was utilized in the previously mentioned 10,000 hour cell test which operated at M-C Power with negligible decay (Figure 1). Scale-up of the Li/Na electrolyte to commercial-area tape casting was completed this year and no additional costs were incurred when compared to the Li/K electrolyte. Current development focuses on lowering the electrolyte material costs and increasing manufacturing rates for commercial-area stack testing scheduled for next year.

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