Analysis of the Cathode Electrical Contact in SOFC Stacks

Abstract

The cathode contact layer is a critical component in solid oxide fuel cell stacks and one possible cause of degradation. Even though this layer and its interfaces are responsible for a large proportion of the ohmic resistance, it is generally difficult to identify the degradation without carrying out an autopsy of the stack. As a non-destructive method, electrochemical impedance spectroscopy is used in this work to investigate in-depth the cathode contact and its evolution with the support of distribution of relaxation time and differences in impedance spectra analyses between 650 • C and 800 • C. By purposefully building a stack with a reduced cathode contact area, the electrochemical resistance of the contact is evaluated and its frequency response identified. Through measurements at various operating conditions the different peaks of the distribution of relaxation time analysis are identified and related to physical phenomena within the cell. These findings are then applied to a stack with a standard contact area in order to explain the degradation behavior observed upon dismounting from the test bench.

Reaction Mechanisms of La2NiO4+δ Oxygen Electrodes Operated in Electrolysis and Fuel Cell Mode

“…Moreover, this effect can be exacerbated by a low electronic conductivity of the electrode material [67]. It is worth noting that the frequency distribution in the impedance diagram should not be strongly impacted by the inhomogeneous distribution of current in the electrode.…”

Start-Up of a Solid Oxide Fuel Cell System with a View to Materials Science-Related Aspects, Control and Thermo-Mechanical Stresses

“…Potential degradation mechanisms for SOFC are numerous, complex, and often mutually dependent. For example, the system design determines to some extent which mechanisms will be dominant [72], also the actual dimensions of parts [73]. Materials the process components and parts are made of are other design criteria with a strong effect on performance and duarability [41].…”

A Facile Combustion Synthesis Route for Performance Enhancement of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF6428) as a Robust Cathode Material for IT-SOFC

“…In contrast, the low-frequency impedance spectra of the fuel cell could be associated with several relaxation processes including adsorption-desorption, gas/ionic diffusion, and electrochemical reactions with multiple intermediate steps for fuel oxidation and oxygen reduction. [37][38] Compared with the fuel cell with commercial LSCF (Fig. 7(a)), the low-frequency impedance spectra of the fuel cell with synthesized LSCF air electrode ( Fig.…”