The behavior of MCFCs using Li/K and Li/Na carbonates as the electrolyte at high pressure

High operating pressure, about 12-25 atm, is required to develop a highly e fficient molten carbonate fuel cell (MCFC) plant system combined with a gas turbine or coal gasifier system. Operation at high pressure, over 10 atm, will accelerate dissolution of the NiO cathode and shorten cell life. There fore, economical applicability as a high-pressure and high-efficiency MCFC plant system and the economical requirement of cell life time must be total ly investigated. It is very important to clarify the performance of the MCF C under such high pressures as the first step for such an investigation. We have examined the performance of several MCFC cells using Li/K and Li/Na e lectrolyte at pressures of up to 44.5 atm, avoiding possible carbon formati on in the fuel stream. The analysis method for cell performance developed b elow 7 arm pressure conditions has proved applicable for analyzing cell per formance over 10 atm. The smaller cathode polarization concerned with CO2 c oncentration and the higher conductivity of the Li/Na electrolyte enabled a higher performance than that of a Li/K cell. Application of the Li/Na elec trolyte to MCFCs seems to be an effective way of prolonging cell life with measurements of the small amount of deposited nickel. Furthermore, the Li/N a cell attained 3.3 kW/m(2) power density, and a high cell voltage (0.82 V) was obtained at 400 mA/cm(2) in 16 atm. This result shows the possibility of developing a high-efficiency MCFC plant system. (C) 1999 The Electrochem ical Society. S0013-4651(98)10-036-8. All rights reserved.