LiFeO2-LiCoO2-NiO cathodes for molten carbonate fuel cells

Dissolution of the state-of-the-art lithiated nickel oxide cathode is a major obstacle for the development of molten carbonate fuel cell (MCFC) technology. LiFeO2 and LiCoO2 were reported earlier as the most promising alternative materials; however, they do not satisfactorily substitute for the state-of-the-art cathode material. A solid solution consisting of LiFeO2, LiCoO2, and NiO is expected to posses some desirable properties of these three materials. Powder compositions in the LiFeO2-NiO binary system and a ternary subsystem with a constant 50:50 molar ratio of LiFeO2:NiO were prepared by the Pechini method. After preliminary powder characterizations, the feasibility of new materials for MCFC cathode application was studied. Electrical conductivity and microstructural characteristics were investigated, first in the form of bulk pellets and then in ex situ sintered porous gas diffusion cathodes. Finally, the electrochemical performance of selected cathodes was evaluated by short-time laboratory scale cell operations. The electrical conductivity of the ternary compositions with 50:50 molar ratio of LiFeO2:NiO increases significantly with increasing LiCoO2 content up to about 25 mol %. Further increase of LiCoO2 content decreases conductivity. The cell study indicates the possibility of preparing cathodes suitable for MCFC application with a considerably high LiFeO2 content. (C) 2003 The Electrochemical Society.