Inkjet Printing for Low-Temperature Solid Oxide Fuel Cells: Comparative Fabrication Techniques and Microstructural Investigations

Solid oxide fuel cells (SOFCs) are emerging as a promising technology for clean energy generation, yet their market penetration is hampered by du-rability and stability challenges. This thesis addresses these challenges by focusing on new fabrication methods for SOFC components and their microstructure. It employs advanced basic materials in the manufacturing process, enabling much lower operating temperatures than traditional materials, which could potentially improve the longevity of the cells. The thesis introduces a unique inkjet printing technique, a mask-free, accurate, and contactless method for fabricating high-performance materials with customized microstructures. This is particularly beneficial for cathodes, where oxygen reduction reactions contribute to activation loss in SOFCs. The research involved developing and optimizing three distinct ink formulations: La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), CuFe2O4, and CuFe2O4 – Gd:CeO2 (GDC) nanocomposite. These formulations were compared with other low-viscosity inks used in drop casting and spin coating. The created inks have undergone extensive evaluation, which includes particle size analysis, rheological characteristics, and thermal analysis, as well as microstructural investigations and electrochemical performance measurement. All inks demonstrated excellent jetting performance, with Z parameters indicating their suitability for the inkjet printing process. For instance, fresh LSCF ink and CuFe2O4 – GDC nanocomposite ink showed Z parameters of 2.77 and 5.5, respectively, at their printing temperature. Electrochemical performance analysis revealed improvements compared to drop casting and spin coating techniques with the same ink. Inkjet print-ing reduced the ohmic resistance of the LSCF symmetric cell from 1.05 Ω cm² to 0.37 Ω cm² at 550°C in an air atmosphere and decreased the mass diffusion resistance by 4.25 times compared to a drop-casted cell. Further comparisons using Electrochemical Impedance Spectroscopy (EIS) showed that inkjet printing could lower the area-specific resistance (ASR) of a 100-layer cell significantly from 19.59 Ω cm² to 5.99 Ω cm² under similar conditions. For the CuFe2O4 – GDC nanocomposite ink – Samba cartridge case at 650°C under H2 and air atmospheres, the best inkjet-printed complete fuel cell gave a Rohm and ASR of 0.96 and 1.12 Ω cm², respectively, using just 2.16 mg of deposited ink (1.63 mg cm-2). In contrast, a spin-coated cell with the same ink amount exhibited higher Rohm (3.2 Ω cm²) and ASR (37.82 Ω cm²). The drop-cast cell with 6.2 times more deposited ink showed even higher values (Rohm = 8.84 Ω cm² and ASR = 15.96 Ω cm²). These findings highlight the potential of inkjet printing for morphological control, improving gas transport, lowering ion transport losses, and speed-ing up charge transfer reactions. This resulted in improved electrochemical performance, emphasizing the potential of inkjet printing in tailoring cathode morphology for the development of high-performance materials in electrochemical energy conversion.