Mechanical and electrochemical performance of composite cathode contact materials for solid oxide fuel cells
The feasibility of adding glass or inorganic binder to conventional SOFC cathode contact materials (CCM) in order to improve bonding to adjacent materials in the cell stack is assessed. Two glasses (SEM-COM SCZ-8 and Schott GM31107) and one inorganic binder (Aremco 644A) are mixed with LSM particles to produce composite CCM pastes. These are used to bond Mn1.5Co1.5O4-coated stainless steel mesh current collectors to anode-supported button cells. The cells are operated at 800 °C for about 1000 h. The cell with SCZ-8 addition to the CCM displays quite stable operation (3.9%/1000 h degradation), whereas the other additives lead to somewhat higher degradation rate. Bonding of the CCM to coated stainless steel coupons is also assessed. Interfacial fracture toughness is determined using a four-point bend test. The fracture toughness for LSM–Schott glass (12.3 N mm−1), LSM–SCZ-8 glass (6.8 N mm−1) and LSM–644A binder (5.4 N mm−1) are significantly improved relative to pure LSM (1.7 N mm−1). Indeed, addition of binder or glass is found to improve bonding of the CCM layer without sacrificing cell performance.