LIFETIME-LIMITING FACTORS FOR A MOLTEN-CARBONATE FUEL-CELL

Commercialization of molten carbonate fuel cells (MCFCs) requires a li fetime of 40,000 h. In order to achieve this goal, the main decay mech anisms must be understood and controlled. Limiting factors affecting t he lifetime of MCFC monocells have been investigated in endurance test s totaling more than 15,000 h using an automated monocell test facilit y installed at CNR-TAE. The cells were assembled with tape-casted Ni-C r anodes and NiO cathodes separated by LiAlO2 matrices impregnated wit h a mixture of Li2CO3 and K2CO3. The tests have been carried out at te mperatures ranging from 873 to 923K. The results of these investigatio ns have indicated that the main limiting factors for long-term operati ons must be correlated with an insufficient carbonate inventory in the tile and with the electrolyte redistribution amongst the active cell components. In operating cells, the electrolyte losses occur through f our basic mechanisms: lithiation of the anode and cathode, hardware co rrosion, volatilization and electrolyte migration (creepage). Post-mor tem analysis by atomic adsorption spectroscopy, scanning electron micr oscopy and Hg-intrusion porosimetry has been employed to study these p henomena. Particularly, it has been observed that the tile structure c hanged drastically. A further problem was the dissolution of the catho de, that is the effect of the small solubility of the NiO in the elect rolyte. The decay effects appear more drastic in the high-temperature test, probably due to the faster kinetics of the parasitic reactions.