Significant impact of the current collection material and method on the performance of Ba0.5Sr0.5Co0.8Fe 0.2O3-d electrodes in solid oxide fuel cells

Abstract

The effects of the current collection material and method on the performance of SOFCs with Ba0.5Sr0.5Co 0.8Fe0.2O3-d (BSCF) cathodes are investigated. Ag paste and LaCoO3 (LC) oxide are studied as current collection materials, and five different current collecting techniques are attempted. Cell performances are evaluated using a current-voltage test and electrochemical impedance spectra (EIS) based on two types of anode-supported fuel cells, i.e., NiO + SDCSDCBSCF and NiO + YSZYSZSDCBSCF. The cell with diluted Ag paste as the current collector exhibits the highest peak power density, nearly 16 times that of a similar cell without current collector. The electrochemical characteristics of the BSCF cathode with different current collectors are further determined by EIS at 600 °C using symmetrical cells. The cell with diluted Ag paste as the current collector displays the lowest ohmic resistance (1.4 O cm2) and polarization resistance (0.1 O cm2). Meanwhile, the surface conductivities of various current collectors are measured by a four-probe DC conductivity technique. The surface conductivity of diluted Ag paste is 2-3 orders of magnitude higher than that of LC or BSCF. The outstanding surface conductivity of silver may reduce the contact resistance at the current collector/electrode interface and, thus, contributes to better electrode performance. © 2011 Elsevier B.V. All rights reserved.