CATHODE MATERIALS FOR MOLTEN CARBONATE FUEL CELLS

摘要

The Molten Carbonate Fuel Cells (MCFC) technology is developing in order to reach the target of a lifetime of 40,000 h, and the bottle neck is represented by cathode stability. The state of art cathode is a presintered porous nickel tape, in-situ oxidized and lithiated. This material (Li-NiO) offers good electrochemical activity, but it is subjected to a low and continuous dissolution process when it is in contact with the carbonates electrolyte. To solve this problem, significant research have been carried out to develop alternative cathode materials with performances close to Li-NiO and lower solubility in molten carbonates. Attention has been focused on the following materials: lithium ferrite (LiFeO_2), lithium manganite (Li_2MnO_3), perovskite (La_xSr_(1-x)CoO_3), lithium cobaltite (LiCoO_2) and mixed oxides (LiFeO_2-LiCoO_2-NiO). LiCoO_2 is the much promising material because it shows a cathodic performance close or higher than Li-NiO, and a solubility an order of magnitude lower, also if in high pressure operation the superiority of LiCoO_2 becomes smaller. The conductivity and electrochemical performances of lithium cobaltite increase considerably by the doping it. To overcome the low mechanical strength, the LiCoO_2 have been deposited, by solution-gel technique, on the inner surface of porous Ni.