Evaluation of perovskite-type contact paste materials for reversible solid oxide fuel cell stacks

Abstract

At the electrode/interconnect interface in reversible solid oxide fuel cells (RSOFC), a contact paste is applied during stack fabrication. Careful selection of a contact paste material (CPM) is essential for improving the robustness of the RSOFC stack. For the successful industrialization of RSOFC technology, development of optimized CPM is required. Herein, three lanthanum-based perovskite compositions, LaNi0.6Fe0.2Cu0.2O3-δ (LNFCu), LaNi0.6Fe0.3Cr0.1O3-δ (LNFCr), and LaNi0.5Co0.2Cu0.3O3-δ (LNCCu) were investigated as air electrode CPMs employed in between Crofer 22 APU interconnect (IC) and La0.3Ca0.7Fe0.7Cr0.3O3-δ (LCFCr) electrode. More specifically, the three candidates were screened for thermal expansion coefficient (TEC), chemical compatibility with adjacent stack components, area specific resistance (ASR), and their performance as an air electrode CPM in a symmetrical LCFCr RSOFC. All three materials show good chemical compatibility with both the IC and LCFCr, excellent match of TEC with cell components, as well as markedly low ASR values. Most notably, from electrochemical impedance spectroscopy (EIS) study, LNFCr, and LNCCu CPMs exhibit polarization resistance values (Rp), at 800 °C, of ca. 0.83 Ω cm2, which is comparable to that of Au (0.63 Ω cm2), a material commonly regarded as the state-of-the-art. Of the three CPMs studied, it was concluded that LNFCr is the best candidate.