Investigation on a novel MCFC cathode material formed by a LiMg0.05Co0.95O2 thin film on porous Ni/NiO electrode

Elisabetta Simonetti, Roberto Lo Presti

Research output: Contribution to conferencePaper

Abstract

Molten carbonate fuel cell (MCFC) are one of the most promising generation systems. Dissolution of the state-of-the-art NiO cathode into the electrolyte and subsequent precipitation of Ni in the matrix is one of the major factors limiting the lifetime of MCFC. In order to solve this problem LiCoO2 doped with Mg was investigated as one of the most promising alternative cathode materials (1,2). LiMg0.05Co0.95O2 cathodes show a lower solubility than NiO but they are more expensive and fragile, so it was proposed to cover NiO cathodes with a magnesium doped lithium cobatite layer. A thin film of LiMg0.05Co0.95O2 was formed (3) on the surface of a porous nickel cathode by Complex Sol-Gel Process (CSGP). In general a NiO cathode is formed in MCFC by in situ oxidation of porous nickel during the cell start up, so two different electrodes were prepared with and without substrate preoxidation in air before dipping to investigate about the best performance. Sol-impregnation technique produced electrodes with an homogeneous layer of lithium cobaltite on the porous nickel surface as we can point out from SEM images. Lithium cobaltite particles homogeneously cover the nickel substrate and no relevant morphological differences can be evidenced between the "no preox" and "preox" electrode. Four points bend tests were carried out both on "no preox" and "preox" electrodes. Samples were taken in different positions and analysed. The Young modulus and strength values for the "no preox" and "preox" electrode are very similar. The electrical conductivity of cathodes was measured by a d.c. technique following the Van der Pauw method in the temperature range 500°C ÷ 850°C, as a function of gas composition and time. Conductivity measurements were carried out on four different electrodes: . a conventional porous nickel sheet (supplied by AFCO) partially oxidized . a bulk Mg-doped lithium cobaltite . a nickel oxide electrode coated with Mg-doped lithium cobaltite ("preox") . a nickel electrode coated with Mg-doped lithium cobaltite ("no preox") From the Arrhenius plots the activation energy values of the conducting process are pointed out . The Ni/LiMg0.05Co0.95O2 cathode was tested in a 100 cm2 electrodes fuel cell with conventional anode and tile. The cell operated for about 1100 h at 650 °C. The changes during the cell lifetime of open circuit voltage (OCV) and cell voltage at different current densities were measured. The cathode kinetic was investigated by changing the partial pressure of oxygen or carbon dioxide. Current interruption was the technique used for correcting measured cell voltage for the ohmic potential drops. The initial fast change of the cell voltage when current is applied or interrupted, is recorded by an Nl acquisition card with an acquisition rate of 2 ksamples/sec. A LabView software, compiled for this purpose, controls the acquisition card. The results of measurements carried out at different hours from cell start up, show no differences in iR (∼4 ?cm2) (4) during the time and with different applied current.
Original languageEnglish
Publication statusPublished - 2005
Externally publishedYes
Event1st European Fuel Cell Technology and Applications Conference 2005, EFC2005 - , Italy
Duration: 1 Jan 2005 → …

Conference

Conference1st European Fuel Cell Technology and Applications Conference 2005, EFC2005
CountryItaly
Period1/1/05 → …

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All Science Journal Classification (ASJC) codes

  • Engineering(all)

Cite this

Simonetti, E., & Presti, R. L. (2005). Investigation on a novel MCFC cathode material formed by a LiMg0.05Co0.95O2 thin film on porous Ni/NiO electrode. Paper presented at 1st European Fuel Cell Technology and Applications Conference 2005, EFC2005, Italy.