EXPERIMENTAL-DETERMINATION OF EFFECTIVE CONDUCTIVITIES IN POROUS MOLTEN-CARBONATE FUEL-CELL ELECTRODES

In this work an electrochemical impedance spectroscopy method fbr the determination of the effective conductivities of the pore electrolyte and electrode matrix in porous electrodes has been used. The technique has been employed on porous nickel oxide and lithium cobaltite cathod es partly flooded with lithium-potassium carbonate melt in cathode gas environment. The experimental results show that the effective conduct ivity of the pore electrolyte of a porous nickel oxide cathode is 0.9- 2.2 Omega(-1) m(-1) at the most. If data are approximately corrected f or the faradaic reaction the effective conductivity becomes 0.1-0.7 Om ega(-1) m(-1). For the lithium cobaltite cathode the measured conducti vity of the solid phase is similar to the data measured ex-situ. The e ffective conductivity of the pore electrolyte is 0.8 Omega(-1) m(-1), i.e. close to the results found for nickel oxide cathodes. The effecti ve conductivity of the pore electrolyte calculated by means of a theor etical model is 0.5-3.5 Omega(-1) m(-1). (C) 1998 Published by Elsevie r Science Ltd. All rights reserved.