Performance Study of Nickel Covered by Lithium Cobaltite Cathode for Molten Carbonate Fuel Cells: A Comparison in Li/K and Li/Na Carbonate Melts

Abstract

The slow dissolution of the lithiated NiO cathode represents one of the main causes of performance degradation in molten carbonate fuel cells. Two main approaches are usually investigated to overcome this problem: modifying the electrolyte composition and studying innovative cathode. In this work, the production of an alternative material as well as a study in different carbonate melt mixtures (62/38 mol % Li/K and 52/48 mol % Li/Na) of this innovative cathode have been taken into account. The issue of cathode surface protection was attained covering a nickel substrate with a thin layer of lithium cobaltite doped with magnesium (LiMg0.05Co0.95O2); a sol impregnation technique was used to deposit gel precursors on the porous surface of the substrate. Chemical analysis, electrical conductivity measurements and scanning electron microscopy were used to characterize the cathodes before and after in-cell tests. The cathodic performance was tested in two 3 cm2 area cells assembled with the following electrolyte compositions: Li/K=62/38 mol % and Li/Na=52/48 mol % in order to investigate the cathode behavior in different carbonate melt environments. Polarization curves and electrochemical impedance spectroscopy measurements were carried out during cell lifetime (about 850 h). Finally, different compositions of the cathodic gas were used to study the influence of oxygen and carbon dioxide on the electrode kinetics.