Development of Electrolyte plate for Molten Carbonate Fuel Cell
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discuss the evaluation result of the advanced powder, the commercial y-LiA102 powder, and a-LiA10 2 under MCFC operation. On the other hand, the formation of cracks in electrolyte plate can cause gas cross leakage between fuel gas and oxidizer gas. The drop of open circuit voltage is caused by the gas cross leakage and deteriorates cell performance. In this paper the effects on the electrolyte plate reinforcement with ceramic fiber was evaluated. EXPERIMENTAL
Electrolyte plates of various types of
Organ-ic solvet
LiAlO,powder.c.e.a.ic fiber
LiA10 2 powder were analyzed after cell test. HSA10 and LSA15 (Cyprus Foote Mineral Co., Ltd.) are commercial yd LiA10 2 powder. TYPE2 (Nippon Mi Chemical Industrial Co., Ltd.) is an advanced y-LiA102 powder. As for the Slurry reinforce material, the high purity aA120 3 fiber (Mitsui Mining Material Co., ITap .asting Ltd.) was used and the rod-shaped yLiA102 (made in our laboratory) was Drying used[5]. Fig.1 shows the process of the fabrication of electrolyte plate. Either LiA1O2 powder or the mixture of LiAlO Fig.1 Process of fabrication of electrolyte powder and ceramic fiber is dispersed in the organic solvent which contains plate dispersant, binder, plasticizer to form slurry. The viscosity of the slurry is adjusted within a suitable range. Then it is cast into tape using the doctor-blade method. Many tests on a single cell with the electrode area of 100 cm 2 were carried out. Each cell was operated at 650 'C, 1 atm and the current density was 150 mA/cm 2 . The fuel gas utilization was 75% and the oxidizer gas utilization was 50%. The composition of gasses was H 2/CO 2/H 2 0=64/16/20 (Fuel) and Air/CO2=70/30 (Oxidizer). The electrolyte plate after cell test was immersed in the 1:1 solution of acetic acid and anhydrous acetic acid to remove carbonate. Then the sample was cleaned with ethanol and dried at about 100 'C. The surface area, the pore size distribution, the particle shape, and the crystalline form of LiA102 after removing carbonate were analyzed by BET type surface area measuring unit, Mercury porosimetry, scanning electron microscope (SEM), and powder X-ray diffraction, respectively. Many thermal cycling tests on a single cell with electrode area of 100 cm 2 were carried out. The temperature was 650'C during cell operation. Thermal cycling test was conducted between 650'C and below 350'C. The gas cross-leakage was determined by measuring nitrogen gas concentration in the anode outlet at a pressure difference of 100 mm H20.
RESULTS AND DISCUSSION Long term operation Figure2 shows the cell performance using the advanced LiA102 powder (TYPE2). Its initial cell voltage was about 820 mV at current density 150 mA/cm 2 . The steadiness of the open circuit voltage (OCV) suggests that the cracks were not significant in the electrolyte plate during cell operation. The cell voltage at the current density of 150 mA/cm 2 and the internal resistance (IR)-loss were very steady, the decay rate was under 0.5%/1000h. This cell performance suggests that the electrolyte-retention
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