The formation of LiCoO₂ on a NiO cathode for a molten carbonate fuel cell using electroplating

Lithiated NiO cathode dissolution has been a major problem for the development of molten carbonate fuel cells (MCFCs). Many studies have been contributed to find new alternative cathodes; here, lithium cobalt oxide, LiCoO₂, was coated onto the commonly used NiO cathode by the electroplating method and the resulting cathode showed much reduced solubility compared with that of the common nickel oxide cathode. Thin film lithium cobalt oxide was prepared by the oxidation of Co metal deposited on a nickel plate in molten (Li,K)₂CO₃ at 650°C under a CO₂-O₂ (2:1 vol%) atmosphere. When this coated nickel plate was oxidized, the open circuit potential (OCP) decayed gradually, indicating two well-defined potential plateaux; the oxide films produced at each potential plateau were identified by X-ray diffraction methods. The surface product at the first plateau was CoO, LiCoO₂ was formed at the second OCP plateau [around -0.47 V vs. CO₂-O₂ (2:1 vol%) reference electrode]. By the same method, LiCoO₂ was coated onto a porous nickel cathode in order to produce a MCFC. For 300 h steady operation of the cells, the mean voltages of the cells were 0.80 V using a NiO cathode and 0.85 V for a LC-NiO(EP) cathode at a current density of 150 mA cm^-2. In addition to the cell efficiency improvement, the solubility of the LC-NiO(EP) cathode was much lower than that of the NiO cathode.