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Research Papers

Performance Study of Nickel Covered by Lithium Cobaltite Cathode for Molten Carbonate Fuel Cells: A Comparison in Li/K and Li/Na Carbonate Melts

[+] Author and Article Information
C. Paoletti

 ENEA C.R. Casaccia TER, Via Anguillarese 301, Rome 00123, Italyclaudia.paoletti@enea.it

F. Zaza, M. Carewska, R. Lo Presti, E. Simonetti

 ENEA C.R. Casaccia TER, Via Anguillarese 301, Rome 00123, Italy

J. Fuel Cell Sci. Technol 7(2), 021008 (Jan 06, 2010) (5 pages) doi:10.1115/1.3176402 History: Received February 21, 2008; Revised March 26, 2009; Published January 06, 2010; Online January 06, 2010

The slow dissolution of the lithiated NiO cathode represents one of the main causes of performance degradation in molten carbonate fuel cells. Two main approaches are usually investigated to overcome this problem: modifying the electrolyte composition and studying innovative cathode. In this work, the production of an alternative material as well as a study in different carbonate melt mixtures (62/38mol% Li/K and 52/48mol% Li/Na) of this innovative cathode have been taken into account. The issue of cathode surface protection was attained covering a nickel substrate with a thin layer of lithium cobaltite doped with magnesium (LiMg0.05Co0.95O2); a sol impregnation technique was used to deposit gel precursors on the porous surface of the substrate. Chemical analysis, electrical conductivity measurements and scanning electron microscopy were used to characterize the cathodes before and after in-cell tests. The cathodic performance was tested in two 3cm2 area cells assembled with the following electrolyte compositions: Li/K=62/38mol% and Li/Na=52/48mol% in order to investigate the cathode behavior in different carbonate melt environments. Polarization curves and electrochemical impedance spectroscopy measurements were carried out during cell lifetime (about 850 h). Finally, different compositions of the cathodic gas were used to study the influence of oxygen and carbon dioxide on the electrode kinetics.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Cathode development approach in ENEA laboratories: schematic sequence followed for the optimization of the alternative cathode preparation process

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Figure 2

(a) Ni and Ni/Co-acetates TGA curves in nitrogen atmosphere and (b) TGA and DTG curves of Ni and Ni/Co-acetates in air

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Figure 3

Ni/Co-acetates cathode SEM images (2000 times): (a) before and (b) after heat treatment at 650°C for 10 h

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Figure 4

Electrical resistance of Ni/Co-acetates cathode as a function of the time and gas composition

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Figure 5

(a) Polarization and (b) power density plots with and without correction of IR loss (RΩ=0.5 Ω) (Li/K electrolyte cell)

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Figure 6

Cell Voltage at different current densities and two different anodic gas compositions (Li/K electrolyte cell)

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Figure 7

Cell voltage at 104.2 mA cm−2 current density as a function of cell lifetimes (Li/K electrolyte cell)

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Figure 8

Open circuit voltage and cell voltage at different current densities and cell lifetimes: a comparison between Li/K and Li/Na electrolytes

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Figure 10

Dependency of cell power from pO2 and pCO2: (a) in Li/K and (b) in Li/Na electrolytes

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Figure 11

Cross section of electrodes-electrolyte assembly: (a) Li/K and (b) Li/Na. SEM-EDS analysis of electrodes-electrolyte assembly: the two images below present a Nickel map of the cross section.

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Figure 9

Nyquist impedance spectra for Ni/Co-acetates in (a) Li/K and (b) Li/Na electrolytes as a function of cell lifetimes: A, B, C, D, and E are referred to different cell lifetimes

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