Sodium-Doped Samarium Oxide Electrolytes for Avoiding the Lithiation-Induced Interface Degradation of Ni_0.8Co_0.15Al_0.05LiO₂ Electrode-Based Ceramic Fuel Cells

Ceramic fuel cells (CFCs) employing lithium compounds, that is, Ni0.8Co0.15Al0.05LiO2 (NCAL) as symmetrical electrodes demonstrate remarkable ionic conductivity and power density at a temperature range of 400–600 °C. However, the stability issue of this type of CFCs has not been well investigated. In this work, we have demonstrated a commercially available samarium oxide (CSM) via a sodium doping method, that is, Na-doped samarium oxide (NDS) materials as functional electrolytes for robust CFCs. Results disclose that during the fuel cell operation, CSM could in situ-react with LiOH from the NCAL anode to cause cell degradation. Doped sodium ions in NDS could confine the LiOH that forms at the grain boundaries, which can result in several benefits, for example, to make the NDS electrolyte denser to prevent gas leakage, to enhance the CFC performance, and to ensure the CFC stability without the need for high-temperature sintering. The NCAL/NDS/NCAL-based fuel cell delivers a stable open circuit voltage over 1.0 V and maximum power density around 200 mW cm–2 for 144 h at 500 °C. Moreover, the optimized cell gives a stable power density of 140 mW cm–2 for 75 h at 500 °C. This work presents a methodology for developing advanced low-temperature CFCs using commercial samarium oxide as the functional electrolyte.