Significant impact of the current collection material and method on the performance of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ electrodes in solid oxide fuel cells

Abstract

The effects of the current collection material and method on the performance of SOFCs with Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ (BSCF) cathodes are investigated. Ag paste and LaCoO 3 (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 + SDC|SDC|BSCF and NiO + YSZ|YSZ|SDC|BSCF. 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 Ω cm 2) and polarization resistance (0.1 Ω cm 2). 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.