Properties of a new type of cathode for molten carbonate fuel cells

The solubility of a nickel oxide cathode in molten carbonate fuel cell (MCFC) electrolyte is one of the major technical obstacles to the commercialization of such fuel cells. Lithium cobalt oxide, LiCoO₂, has been selected as a candidate material for MCFC cathodes because its solubility is small and the rate of dissolution into the melt is slower than that for nickel oxide. On the other hand, the electrical conductivity of LiCoO₂ is lower than that of nickel oxide. Thus, nickel oxide has been coated with stable LiCoO₂ in carbonate by a PVA-assisted sol-gel method to give a LiCoO₂-coated NiO (LC-NiO) cathode. Raman spectra show that the structure of LC-NiO is different from that of nickel oxide, and that a LiCo_1-yNi_yO₂ phase is formed during heat-treatment of the LC-NiO cathode. The coating of LiCoO₂ on NiO electrode increases with increase in the dipping and heating times. The performance of unit cells show that the mean voltage of the cells is 0.80 V using a NiO cathode and 0.85 V with a LC-NiO cathode at a current density of 150 mA cm^-2. The solubility of the LC-NiO cathode in molten carbonate electrolyte is half that of NiO cathode after 300 h at 650°C.