Development of advanced electrolyte-supporting ceramic matrices for high-performance Molten Carbonate Fuel Cells (MCFCs)

Electrolyte matrix is an important component of Molten Carbonate Fuel Cells (MCFCs) being responsible for both ionic conduction and gas sealing. The matrix should be full of electrolyte and could keep electrolyte carbonate. As the electrolyte matrix is a key component for higher MCFC cell performance, the main objective of this work is to improve MCFC performance by optimizing porous structure and ionic conductivity of the electrolyte matrix. A second objective was to develop a more sustainable matrix tape casting fabrication process. Tape casting with an optimized and eco-friendly slurry formulation was employed to produce uniform thin ceramic green tapes with controlled thickness in the range 0.2–0.7 mm and novel matrix porous structure. In particular, the optimized process parameters allowed to produce a LiAlO2 with finer porosity than in conventional matrix fabrication processes. The porosity of the novel matrix was centered in the mesoporous range, which was well below the 200–300 nm pore average of conventional matrices. The novel matrix showed also high flexibility and mechanical integrity. The characteristics of the tapes were examined using Scanning Electron Microscopy (SEM) analysis, X-ray Power Diffraction technique (XRD) and Brunauer Emmett Teller (BET) analysis. Finally, four button cell tests were conducted with a 0.45 mm thick fabricated matrix, 0.5 mm, and 0.68 mm thick matrix. The testing results showed that cells had low internal resistance and significantly higher current density with respect to conventional MCFC cells indicating thus a strong ionic conductivity enhancement of the matrix, probably due to a composite electrolyte effect triggered by the mesoporous structure of the novel matrix. In definitive, the highly beneficial effect of a matrix mesoporous structure in improving MCFC cell performance beyond the state-of-the-art technology has been demonstrated in this thesis