SOFCs with an LSC F Cathode

In addition to the LSM-type cathode cells, LSC(F)-type cells have also been developed and improved. Cells with an LSC(F)-type cathode can be used at temperatures lower than 750 °C, in contrast to the LSM-type cathode cells, which perform best above 750 °C. The decrease in the power density at lower temperatures, in particular for cells with an LSM cathode, is mainly due to overpotentials at the cathode side. Therefore, research was focused on new cathode materials with higher electrocatalytic activity than the state-of-the-art LSM perovskites. As a result, LSC(F) was chosen as the material for operating temperatures lower than 800 °C, since it possesses high electronic and ionic conductivity, which make this material an excellent candidate as an MI EC (mixed ionic and electronic conductive) cathode. 

A more systematic study of the variation of the composition of the ferrite-based perovskites was started in 2003. The materials examined were Lai-jc ySr, Coo.2Feo.803 j(x = 0.2 and 0.4 y = 0-0.05), Lao.8Sro.2Fe03 j(LSF), Lao.7 Bao.3 

A decrease in the current density for sintering temperatures above 1250 °C could be explained by the increased formation of a solid solution between the 8YSZ electrolyte and the CGO layer, whereas a decrease in power densities at sintering temperatures lower than the optimum could be explained by lower adherence of the diffusion barrier layer. Finally, cells with an optimized CGO diffusion barrier and LSC(F) cathode layer achieved current densities of about 2.3 A cm at 800 °C and 700 mV. This type of cell is denoted at FZJ as the state-of-the-art cell with an LSC(F) cathode. Table 9.3 shows the characteristics of these state-of-the-art cells with a screen-printed CGO diffusion barrier layer and with an L58SCF-type cathode. 

Functionality Production technique(s) Type Sintering temperature (C) Thickness 

Anode functional tape casting Vacuum slip casting N10/8YSZ 1400 10gm 

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Figure 9.9 Status of development of SOFCs with an LSC(F) cathode at FZJ.

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