Durable high-performance Sm_0.5Sr_0.5CoO ₃-Sm_0.2Ce_0.8O_1.9 core-shell type composite cathodes for low temperature solid oxide fuel cells

Sm_0.5Sr_0.5CoO₃ (SSC)-Sm _0.2Ce_0.8O_1.9 (SDC) core-shell composite cathodes are synthesized via a polymerizable complex method, and the durability of a cell incorporating the cathodes is examined. Nanocrystalline SSC powders have been coated onto the surfaces of SDC cores to enable the formation of a rigid backbone structure, over which the catalyst phase is effectively dispersed. A symmetrical SSC-SDC SDC SSC-SDC half-cell exhibits a polarization resistance of 0.098 Ω cm² at 650 °C. The durability and microstructure of the cathode are investigated by electrochemical impedance spectroscopy and thermo-cycle tests at temperatures in the range of 100 °C-650 °C. After 30 cycles, the polarization resistance is found to increase by 9.04 × 10^-2 Ω cm², a 3.56% rise with respect to the initial resistance. Coarsening of the SSC catalyst phase has been prevented with the use of core-shell type powders, as confirmed by a nearly constant low frequency polarization resistance and a microstructural analysis. The performance of a unit cell comprised of the core-shell type cathode exhibits 1.07 W cm^-2 at 600 °C and 0.62 W cm^-2 at 550 °C.