Additive Manufacturing of Solid Oxide Electrochemical Cells and Components

Solid oxide cells (SOCs) are exceptionally efficient electrochemical energy conversion devices, featuring reversibility between fuel cell (SOFC) and electrolysis (SOEC) modes. It is an important renewable energy technology with great potential to play a key role in future power grid supply systems and strategies for managing excess electricity. However, the complexity of manufacturing and integrating SOC stacks, coupled with the challenge of corrosion in metal components during long-term operation, has constrained the further development and application of SOC technology. Besides the intrinsic properties of the materials used, the performance and stability of SOCs are strongly influenced by the structural characteristics of the SOC system or its components. Consequently, optimizing the structure of SOCs is an effective way to enhance their performance and stability. However, conventional SOC manufacturing techniques, such as tape casting and screen printing, are primarily suited for creating flat structural components and pose significant challenges in producing complex 3D structures, substantially constraining the possibilities for design optimization of SOC structures. This has resulted in the structure of commercial SOCs being predominantly confined to flat plate configurations over the past several decades, with virtually no advancement in the design of their components.

Additive manufacturing technology, also known as 3D printing, boasts a high degree of freedom and precision in shaping complex 3D structural components, surpassing the capabilities of conventional manufacturing methods. Over the past decade, this technology has seen rapid advancements, with successful applications in metals, ceramics, and polymers. It has now become an integral part of modern industrial manufacturing, impacting sectors such as aerospace, automotive, maritime, medical devices, and so on.

Leveraging the robust manufacturing capabilities of 3D printing technology for complex 3D structures opens up vast imaginative possibilities for the redesign of SOC structures. This paper systematically explores the feasibility of employing 3D printing technology in the manufacturing of SOCs or their components:

(1) We design a monolithic self-supported SOC based-on a gyroid electrolyte. The ceramic electrolyte, sealing components, and support structures are seamlessly integrated into a unified form, fabricated using DLP-based VAT photopolymerization (VPP) 3D printing technology. The fuel electrolyte and oxygen electrode are applied to the opposing surfaces of the electrolyte using a self-designed air jet-assisted wet coating method, and after undergoing a co-sintering process, they form a functioning SOC. The sealed glass and metal interconnects for conventional SOC stacks are no longer required for our design. Moreover, switching from 2D (planar) to 3D (gyroid) electrolytes has maximized spatial utilization. Our design markedly enhances the lightness and compactness of SOCs. Compared to conventional planar SOC stacks, 3D monolithic SOCs (3D SOCs) demonstrate a tenfold improvement in electrochemical performance, both in terms of mass and volume indices. Meanwhile, 3D SOCs exhibit electrochemical stability and microstructural stability compatible with conventional SOCs. This design successfully transitions SOC technology from a 2D to a 3D concept, resulting in an ultra-lightweight and ultra-compact 3D SOC that avoids degradation from metal components, thereby significantly expanding the application prospects of SOCs.

(2) We employ laser powder bed fusion (LPBF) 3D printing technology to design a metal support featuring low-tortuosity gas channels for third-generation SOCs. LPBF technology, based on melting metal powder and rapid solidification forming, diverges from conventional powder sintering techniques. This divergence circumvents the formation of sintering necks among powder particles in porous supports, which are susceptible to rapid oxidation/corrosion and subsequent loss of conductivity. Consequently, optimizing this structure enhances the stability of electron conduction of metal supports. We have additionally developed a multi-coating method that combines electrophoretic deposition (EPD) and infiltration to create high-quality oxidation-resistant coatings on metal supports. The metal supports, featuring simplified straight gas channels, enable the uniform formation of coatings on their surface through EPD techniques. The subsequent infiltration process further enhances the quality of the interface between the metal support and the ceramic coating, as well as the density of the coating, thereby endowing the metal support with excellent high-temperature oxidation/corrosion resistance.

This work substantially boosts performance by pioneering the optimization of SOC component structures, demonstrating the potential of additive manufacturing technology in SOCs. This thesis also thoroughly analyzes the applications of additive manufacturing for SOCs, anticipating future developments and strategies for scale-up.