Transitioning Low-Temperature GDC Socs: Lab to Commercialization Scale

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Solid oxide fuel cells (SOFCs) electrochemically convert hydrogen and oxygen into electricity, heat, and water with high efficiency (~55%) [1], while in reverse operation, water and electricity are converted to hydrogen and oxygen in solid oxide electrolysis cells (SOECs). Appropriately designed solid oxide cells (SOCs) can operate in both SOFC and SOEC mode.Conventional SOCs typically demand elevated operating temperatures (800-1000°C), resulting in higher cost and accelerated degradation issues. Lowering operating temperatures below 600°C reduces thermal stresses, shortens start-up times, and broadens applications [2].Ce1-xGdxO2-δ (GDC), due to its superior oxygen ion conductivity at reduced temperatures, has lower ohmic losses than competing electrolyte materials. Thus, our 1.2 cm diameter circular anode supported GDC cell with 0.31 cm2 active area exhibits exceptional power densities, reaching approximately 3 watt per square centimeter at 650°C. Through optimal design, these cells exhibit exceptional performances in fuel cell mode, significantly enhancing efficiency and effectiveness when operating as an electrolyzer for fuel generation. This advance in performance is a result of mitigating the leakage current issues typical of ceria-based electrolytes through precise engineering of the cathodic microstructure and surface chemistry modification [3].The transition from lab-scale to large-scale commercialization (with active areas of 16 cm² &; 81 cm²) presents significant challenges such as tailoring material properties for large-cell versus button-cell synthesis while maintaining high performance levels.In this work we explore the challenges encountered during the scaling-up process. We report on fabrication strategies employed to achieve cell flatness, maintain high efficiency, ensure cost-effectiveness, and achieve long-term stability. Specifically, we have fabricated graded anode-supported cells [4] by developing an innovative lamination strategy involving tapes oriented perpendicular to each other. This approach notably contributed to achieving superior electrolyte densification and resulted in significantly flatter (low curvature values) with respect to both horizontal and vertical axes in cartesian coordinate space. When compared to the flatness values of 10x10 cm2 commercially available cells, our cells demonstrated remarkably flatter curvatures as shown in figure 1. This characteristic has proven highly beneficial for stack assembly, minimizing issues such as cell cracking and reducing sealing-related problems. By optimizing the cathode scaffold and infiltration process on larger area cells through a spray-coating machine, scaling up challenges are effectively mitigated compared to the button cell approach, where scaffold preparation and infiltration were performed using blade coating and a hand pipette, respectively. This approach effectively tackles electronic conduction issues in ceria-based electrolytes, leading to higher Open Circuit Voltages (OCVs) in fuel cell mode and increased efficiencies in reversible mode.