Fibrous Mixed Conducting Cathode with Embedded Ionic Conducting Particles: Facile Synthesis and Their Electrochemical Properties for Solid Oxide Fuel Cells

We propose the MIEC (Sm_0.5Sr_0.5CoO_3−δ or La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ) fiber with embedded ionic conducting particles (Sm_0.2Ce_0.8O_1.9 or BaCe_0.7Zr_0.2Y_0.1O_3−δ) instead of simple external composite method. This structure is devised to strengthen the advantages of fibrous cathode; (i) suppress grain growth of the MIEC matrix by dispersed ionic conducting particles, (ii) relieve residual thermal stress within the fibers, (iii) maintain the overall porosity without filling the network pores, and (iv) simplify the composite processing compare to other process such as infiltration. The ionic conducting nanoparticles were embedded in the MIEC fiber matrix as the composite cathode for SOFCs application by electrospinning method. We compared the electrochemical performance of the fiber composite with the conventional composite cathode. As a result, we could conclude that the structural excellence of the fibrous composite cathode, i.e. promoting the charge transfer reactions by building continuous paths and maximizing the TPB sites in virtue of the dispersed ionic conducting particles within the MIEC fiber matrix. The single cell with the fiber composite cathode shows much higher performances; its maximum power densities are about 1,400 and 380.5 mW∙cm⁻² at 700 and 600 ^oC respectively, accounting for 63.1 % and 75.8 % improvements as compared to the cell with the powder composite cathode operating at the same temperatures. The performance improvement of the fiber composite cathode far surpasses that of the powder composite cathode, which is ascribed to the microstructural contribution originating from fibrous structure.