Development and characterization of novel cathode materials for molten carbonate fuel cell

L. Giorgi, M. Carewska, M. Patriarca, S. Scaccia, E. Simonetti, A. Di Bartolomeo

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Abstract

In the development of molten carbonate fuel cell (MCFC) technology, the corrosion of materials is a serious problem for long-term operation. Indeed, slow dissolution of lithiated-NiO cathode in molten carbonates is the main obstacle for the commercialization of MCFCs. In the search of new, more stable, cathode materials, alternative compounds such as LiFeO2, Li2MnO3, and La1-xSrxCoO3are presently under investigation to replace the currently used lithiated-NiO. The aim of the present work was to investigate the possibility to produce electrode based on LiCoO2, a promising cathode material. At first, LixCoO2power samples (0.8 < x < 1.1) were made by thermal decomposition of carbonate precursors in air. The synthesis processes were monitored by thermal analysis (TGA, DTA). The calcined and sintered power samples were characterized by X-ray diffraction (XRD) and atomic absorption spectrophotometry (F-AAS). A single phase was detected in all the samples, without any change in crystal structure as a function of lithium content. Porous sintered electrodes were prepared starting from lithium cobaltite powders mixed with different poreformers by cold pressing and sintering. A bimodal pore-size distribution with a mean pore diameter in the range of 0.15 to 8 μm, a surface area of 2 to 12 m2/g and a porosity of 10 to 65%, determined by the Hg-intrusion technique, were observed in all the materials. Conductivity measurements were carried out in the temperature range of 500-700 °C, in air. The influence of the deviations from stoichiometry on the electronic properties was determined, the conductivity value of the stoichiometric compound being the lowest. A linear relationship between the electronic conductivity and the sample porosity was found. Solubility testing of the materials was carried out to evaluate their chemical stability in the electrolyte. The sampling method (F-AAS) and square wave voltammetry (SWV) were used to determine the concentration of dissolved cobalt in carbonates metl (Li2CO3/K2CO3= 63/38 mol%, pO2= 0.33 atm, pCO2= 0.67 atm, T = 650 °C). The Co content under steady-state conditions, was 6 ppm, i.e., lower than that for Ni from NiO(Li). To test the cathodic performance of the materials, electrochemical impedance spectroscopy (EIS) measurements were carried out to investigate the porous electrode/molten carbonates interface. For this purpose a laboratory-scale MCFC with the same electrolyte as that for the solubility tests was used. The cell was assembled with two identical porous cathodes (fabricated by cold pressing) to avoid any influence from an anode and a reference electrode. With this cell it was possible to determine the influence of atmospheric composition on electrode performance and the long-term stability. © 1994.
Original languageEnglish
Pages (from-to)227 - 243
Number of pages17
JournalJournal of Power Sources
Volume49
Issue number1-3
DOIs
Publication statusPublished - 1994

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All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Physical and Theoretical Chemistry
  • Electrical and Electronic Engineering

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