Improvement of Plasma Sprayed LST/FeCr Metal–Ceramic Composite Interconnect for Segmented-in-Series SOFCs

In the large scale integration process of solid oxide fuel cells (SOFCs), high performance and highly stable interconnect materials have always been the focus of scholars’ attention. The low temperature stability of traditional metals and the relatively low electronic conductivity of ceramic materials compared with metal materials are the constraints on large scale integration (application). In this study, a new type of interconnect suitable for segmented-in-series SOFCs (SIS-SOFCs) has been developed and is introduced on the anode gas side (LST) of the LST/LSM dual-layer interconnect by mechanical mixing. The coating is prepared by atmospheric plasma spraying (APS), and a composite coating with high density, high electrical conductivity, and high stability that meets the requirements of SOFCs is obtained. The spraying behavior of the composite phase is systematically evaluated by means of phase analysis, in flight particle observation, etc. The ultra-high electrical conductivity of the composite coating further reduces the performance loss. The optimized SIS-SOFCs (n = 9) connected by the dual-layer interconnect has an output power of 25 W at 800 °C, and the maximum power density is 820 mW/cm² (Fuel gas: hydrogen at a flow rate of 2 L/min. Oxidant gas: oxygen at a flow rate of 2 L/min.) Compared with the maximum power density of 430 mW/cm² exhibited by the pure phase LST/LSM at 800 °C, it is increased by 90%. During the 100hrs constant current discharge (0.3A/cm²) test, the performance degradation rate of the cell with 10%SUS430 is 0%. In addition, a nonlinear relationship between the interconnect performance and the cell performance is established. These research results indicate that the composite interconnect prepared by atmospheric plasma spraying is an ideal material system for realizing the interconnect for the SIS-SOFCs.