2, Northwestern University, Chicago, Illinois, United States
The fabrication and assembly of solid oxide fuel cell (SOFC) components into an integrated structure, including both support and functional layers, remains one of the primary challenges preventing the widespread adoption of SOFCs as an energy conversion technology. We present an efficient and highly scalable multi-material process for fabricating SOFCs using a combination of 3D-Painting (a room-temperature, extrusion-based 3D-printing process) and dip-coating of particle-laden, liquid 3D-inks. 3D-Painting is used to sequentially and precisely deposit anode and cathode materials, allowing unprecedented control over gas channel geometries. Depositing layers thinner than 100 µm using extrusion-based 3D-printing is impractical, so these 3D-inks are repurposed for dip-coating of mechanically robust and controllably thick multi-material films for electrolyte and interconnect layers. The 3D-inks used for both 3D-printing and dip-coating are synthesized through simple, room-temperature mixing of a polymeric binder, organic solvent mixture, and SOFC material powders. The volume percentage of particles contained in the inks can be tailored between 60-90 vol% to control shrinkage and porosity during binder burn-out and sintering; optimization of the particle content to achieve uniform shrinkage between materials is critical to prevent warping, cracking, or delamination during cell co-firing and to ensure optimal performance of each component. In addition, the effects of 3D-printed object geometry, residual solvent content, and different polymeric binders on overall material shrinkage are analyzed. The microstructural and electrochemical characteristics of the fired cells are analyzed and compared with cells produced entirely using traditional tape-casting techniques. Finally, we show how these processes can be extended beyond traditional, planar SOFC architectures to geometries designed to optimize electrochemical function and device performance.