Application of Composite Technology for SOFCs
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Application of Composite Technology for SOFCs
Vladimir Petrovsky, Harlan U. Anderson, Tatiana Petrovsky Electronic Materials Applied Research Center, University of Missouri-Rolla, Rolla, MO 65401 ABSTRACT Composite technology is a new approach to solid oxide fuel cell (SOFC) fabrication. It is based on the net shape processing, which uses a combination of colloidal suspension and polymer precursor techniques. Different elements of SOFC can be prepared and optimized using this approach and the flexibility of the net shape processing. The goal of this research was to develop net shape procedures for different elements of SOFC, to show the real possibility preparing all these elements of SOFC and to investigate the advantages of composite technology. A nickel-YSZ composite was prepared and investigated as the prospective anode material. High electronic conductivity and stability in REDOX cycles were shown for this material. Different cathode compositions were prepared using composite technology and tested. It was shown, that these materials ensure low overpotentials and are time stable at operation temperature up to 800oC. All three SOFC designs were tested: anode, cathode and electrolyte supported SOFCs. It was possible to achieve low resistance of SOFC structure for all designs, but electrode supported SOFCs had limitation in the current connected with the gas diffusion through thick electrode substrates. The best performance was achieved on an electrolyte supported system with 100 µm YSZ electrolyte and composite anode and cathode: 0.75W/cm2 power density at 0.6 V at 800oC.
INTRODUCTION Solid oxide fuel cells (SOFCs) are one of the most important perspective energy conversion devices [1]. The main demand in the current SOFC development is lowering the operation temperature to the range of 600˚C – 800˚C. It is necessary to decrease the resistance of the electrolyte and both electrodes (cathode and anode overpotentials) in order to lower operational temperature and to increase or at least sustain performance in comparison with high temperature SOFCs. One of the ways to lower operation temperature is to decrease the thickness of the electrolyte. That is the reason why electrode supported systems is the design of choice for the most of the developers. It is not possible to deposit dense electrolyte on pre-sintered substrate (anode or cathode) by powder based technologies, so high temperature co-sintering is technology of choice [2-4]. Yttria stabilized zirconia (YSZ) is the most commonly used material as the SOFC electrolyte and several approaches have been made to develop thin film YSZ deposition techniques on either the anode or cathode. The methods include chemical and physical deposition, such as Electrochemical Vapor Deposition (EVD) [5] or magnetron sputtering [6], and liquid precursor and powder processing techniques such as polymer spin coating [7] or tape casting [8]. The detailed description of YSZ thin film fabrication techniques can be found in the review article [9]. All these techniques experienc
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