Investigation on a ionic liquid matrix for decreasing MCFC working temperature

Molten Carbonate Fuel Cells (MCFCs) are characterized by high working temperatures (600-700°C). They have high efficiencies. The primary problem of MCFCs is durability; high temperatures and the typical used electrolyte accelerate the cell components breakdown and corrosion; thus, the cell life may be not satisfactory for stationary use. An original patented small size MCFC was proposed and tested in previous works [1-4]. The proposed cylindrical geometry allowed to obtain benefits with respect to the traditional MCFCs in terms of construction time and costs, thermal dispersion minimization, global efficiency; minimization of gases tight problems, compression strain uniformity on the contact surface. The present paper regards an investigation on using ionic liquids as electrolyte support in the aforesaid MCFC instead of a lithium aluminate porous element. In the traditional cylindrical MCFC, carbonate liquefaction is needed in the carbonates-glycerine mixture starting at 500°C. This phase may be avoided by using ionic liquids, which are low melting point (<100°C), thermally stable (up to 200°C) salts which represent a new class of non-molecular, ionic solvents. They are able to solvate a broad spectrum of both organic and inorganic compounds, have low vapour pressure, are recyclable and easily handled [5-6]. Thus, ionic liquids may help the charge separation at temperatures lower than 150-200°C. They may support the carbonate ion production and passage through the matrix; thus, they may be suitable as matrix support. The advantage is to reduce the MCFC working temperature; thus, a low temperature MCFC (LTMCFC) may be obtained. The LTMCFC life may be significantly longer than a traditional MCFC one. A single LTMCFC experimental facility was built and used for preliminary tests. Different kinds of ionic liquids were tested. Electrolytic solutions were made by ionic liquids (solvent) and lithium-potassium carbonates (solute). Tests were led at temperatures lower than 200°C in order to verify the proposed solution at temperatures very low with respect to traditional MCFC ones. Tests were made by supplying the proposed facility with hydrogen. The produced voltage and current were evaluated for each kind of ionic liquid matrix by varying the applied load and temperature. Preliminary tests allowed to verify the suitability of the proposed solution and may be useful to individuate possible other adjustment for performances improving.