Solubility and electrochemical studies of LiFeO2–LiCoO2–NiO materials for the MCFC cathode application

The dissolution of the state-of-the-art lithiated NiO is still considered as one of the main obstacles to the commercialisation of the molten carbonate fuel cell (MCFC). Development of alternative cathode materials has been considered as a main strategy for solving this problem. Ternary compositions of LiFeO2, LiCoO2 and NiO are expected to decrease the cathode solubility while ensuring a good electrical conductivity and electrochemical activity towards the oxygen reduction. In this work, new material compositions in the LiFeO2–LiCoO2–NiO ternary system were synthesised using Pechini method and investigating their electrical conductivity by the DC four probe method. Then the influence of the cobalt content in the composition was determined in terms of AC impedance analysis and solubility measurements after 200 h of immersion in Li2CO3–Na2CO3 at 650 °C. The DC electrical conductivity study reveals the ability of improving the electrical conductivity, adequate for MCFC cathode application, by controlling the Co content of the composition. A special attention was given to the evolution of the open circuit potential as a function of time and to the impedance spectroscopy characterization related to microstructure modifications. Taking into account solubility, electrical conductivity, as well as electrochemical performance in the fuel cell, this study reveals the possibility of using LiFeO2–LiCoO2–NiO ternary materials for MCFC cathode.