Electrode for Molten Carbonate Fuel Cells
Development and Investigation of Alternative Oxygen Electrode Material for Molten Carbonate Fuel Cells
Tech Area / Field
- NNE-BCM/Batteries and Components/Non-Nuclear Energy
3 Approved without Funding
VNIIEF, Russia, N. Novgorod reg., Sarov
- High Temperature Electrochemistry Institute, Russia, Sverdlovsk reg., Ekaterinburg
- GenCell Corporation, USA, CT, Southbury
Project summaryIn the Russian Federal Nuclear Center (RFNC-VNIIEF) and the Institute of High Temperature Electrochemistry of the Ural Department of the Russian Science Academy (IHTE UrO RAN) the works have been performing for the search and investigations of new alternative materials for molten carbonate fuel MCFC nickel-free cells.
The main field to apply energy plants on the MCFC basis is a large-scale electricity production. MCFC can operate on different kinds of natural fuel with high efficiency and minimal environmental pollution.
The advantages using power plants on the basis of electrochemical reactions have been already successfully corroborated in USA and Japan. High temperature fuel cells are one of the fuel cell (FC) kinds showing large promise. Today, due to efforts of the leading countries, - developers of fuel cell technologies, - power MCFC and SOFC plants approached to the commercialization.
The primary factors for a successful MCFC launching to the market are their production cost and lifetime. These factors are interrelated. Unfortunately, today the cost of electrochemical generators is rarely estimated taking into account the prime factor of power FC plants, - their lifetime. Tens of thousands operation hours practically unattended is the principal merit of FC.
One of the main problems restricting a fuel cell lifetime is connected with the corrosion of a cathode material – aluminized nickel oxide. NiO solubility in the carbonate melt is rather low (3*10-5 g/cm3). Nevertheless, reaching the anode, nickel ions are able to reduce to a metal, which leads to a germination of nickel dendrites and, finally, - to a short-circuit of a fuel cell.
Lifetime increase of modern NiO cathodes is possible both at the expense of change of working MCFC conditions and as a result of modification of just the cathode material with additions reducing nickel solubility in the electrolyte. As against to the methods to modify NiO cathodes the development of the cathode nickel-free material is fundamentally new.
The Project aim is to develop a production technology, on the basis of the technological processes available, for porous oxygen electrodes to apply also in the industrial production, to study new alternative cathode nickel-free materials both independently and in MCFC. New cathode materials will be used in fuel cell batteries for power MCFC plants.
Under the Project it is proposed to study oxide materials on the basis of solid solutions with a perovskite structure. Perovskites are the oxide class well studied, nevertheless, the possibility to use them in MCFC is studied poorly.
The result of the works under the Project will be the following: development of the production technology to apply also in the industrial production, development of the oxygen electrode (cathode) for batteries with molten carbonated fuel cells of the alternative nickel-free material with an increased corrosion resistance, with characteristics and cost production similar to ones of the cathode made of the conventional material (nickel oxide lithiated).
As a result of the Project implementation, an optimal oxygen electrode composition will be determined in view of the electron conduction, corrosion resistance and efficiency in the oxygen reduction including the comparison with the conventional material. The MCFC structure will be optimized establishing the contact between the electrode and separator of low resistance and the lifetime 3000-hour testing will be performed for a fuel cell with a new cathode of the laboratory scale of 100 cm2.
The preliminary testing showed that lanthanum-lithium ferrite had the electric conductivity of about 3 Ohm–1cm–1 and didn't interact with the melt carbonates. Testing of lanthanum-lithium ferrite electrodes in the laboratory MCFC breadboard constructions showed that new electrodes could provide a current density of 160–200 mA/cm2 with the polarization of 200 mV. The real power density achieved in the laboratory breadboard constructions at 0.75 mV was about 100 mW/cm2. It must be noted that comparatively low power density is accounted to a considerable extent for a deficient development of the technology production for porous cathode plates of a new material.
As a result of the Project implementation, the production technology will be developed for porous electrodes to apply also in the industrial production. It is proposed to achieve a material cost reduction at the expense of the optimization of a mole iron fraction and the use of a non-separated mixture of rare-earth elements instead of pure agents. The technical economical analysis and cost estimation for production of electrodes will be performed in a large-scale production.
The work results will be of a scientific and practical value due to the actuality of the problem for production of new environmentally conscious pure sources of electric power.
RFNC-VNIIEF and IHTE UrO RAN have got a scientific potential, material-technical base, laboratory and diagnostic equipment necessary to implement this Project.
Specialists of RFNC-VNIIEF and IHTE UrO RAN have successfully performed a number of works in MCFC under the international contracts with the Argon National Laboratory (1998 – 2000 years):
- IPP–ANL–069–RS. "Influence of Washing Gas on the Corrosion of Wet MCFC Seal";
- PP–ANL–058–RS. "Influence of Electrolyte Admixtures on the MCFC Operation".
The following works have been completed under the ISTC Projects:
- # 1273. "Development of the Anticorrosion Protection Method for Metal Structures of Molten Carbonate Fuel Cell Batteries";
- # 2281р (partner). "Development of New MCFC Materials".
The works have being performed under the Project # 1271 "Investigation of Possibility to Use Different Materials as Thickener of Matrix Plates".
By the technical approaches and methodology the works implemented are mainly similar to the tasks of the new Project.
The intensive investigations for the cathode direction have being performed in RFNC-VNIIEF and IHTE UrO RAN for about the last ten years. The work results were presented at the Russian and international conferences.
In 2001 the leading specialist of RFNC-VNIIEF Dr. S.I. Malevanny defended a thesis "Forming of cathodes of carbonate fuel cells of nickel oxide lithiated and their electrochemical activity" for a competition of the academic degree for a candidate of the chemical science.
The Project realization will allow the following:
- To provide for Russian scientists and specialists engaged in weapon production a possibility to reorient their capabilities to a peaceful activity;
- To encourage the integration of Russian scientists into the international scientific society;
- To support fundamental and applied investigations and technology development in peaceful purposes especially in the environment protection, energy production and nuclear safety;
- To encourage the solution of national and international technical problems (others, except ones noted above);
- To support a transition to a market economy meeting civil demands.
In this Project the investigations have being actually performed in concern of industrial countries developing and producing power MCFC plants (USA, Japan, Germany and others). In Russia the works on MCFC haven't being practically funded.
According to the work scope under this Project it is proposed to implement the following scope of collaboration with a foreign collaborator:
- exchange of information in the Project implementation;
- submission of comments to the technical reports (quarterly, annual, final and others), presented by the Project participants to ISTC;
- if necessary, joint use of specified test materials and samples;
- if necessary, cross checks of results obtained during the Project implementation.
The work proposed under the Project is based on the experience accumulated by the specialists of RFNC-VNIIEF and IHTE UrO RAN in the development of new MCFC materials.
The work executors have got a large experience for corrosion and electrochemical investigations, technological and engineering developments, metallographic and mass-spectral investigations.
All the Project work will be pided into two large stages. During the first work year it is proposed to design and manufacture facilities and rigging for investigations, modernize test stand, manufacture cathode samples of the alternative materials. The investigations will be performed for cathode of alternative materials being different for their chemical composition by the standard and relaxation electrochemical methods on dense fully immersed and porous gas-diffusion electrodes. By the results of the comparative analysis, the optimal material will be chosen in view of the efficiency/cost correlation.
During the second year the long-term corrosion testing will be performed for the best material in the MCFC operation. The development of the production technology will be fulfilled to apply also in the industrial production, oxygen electrode (cathode).
The main criteria to compare with the conventional material are the following: electron conductivity, electrochemical activity (exchange currents, mA/cm2); specific power in the laboratory stack (W/cm2); cost; lifetime. The pilot lot will be manufactured for cathodes of the alternative material with dimensions of 100*100 mm to deliver to the collaborator for investigations.
In the technical-economical analysis several variants will be considered to establish a production including the automated and automatic ones. The selling-price for alternative material electrodes in the large-scale production will be estimated according to the requirements of FOB, Saint Petersburg city, Russia, (in concordance with the requirements of INKOTERMS).
As the Project tasks are implemented, the publications for work results and participation in the international meetings and conferences are planned.
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