(Invited) A Novel, Ultra-Fast Fabrication of SOFCs By Flash Light Sintering Process

Abstract

Solid oxide fuel cells (SOFCs) have strong potential for next-generation energy conversion systems because of their high energy conversion efficiency, fuel flexibility and low emission of pollutant. In the last decades, the SOFC technology has rapid progress in terms of performance and durability aspect, expanding its application ranges from stationary system to portable devices. In the fabrication of SOFCs, a simple and mass productive fabrication process such as screen-printing, tape casting and sol-gel method are widely used in the industry because it is easy, scalable and economical process. However, a high temperature post heat-treatment process is required to ensure material properties of the ceramic electrolyte and electrode in these processes. In particular, to achieve a highly dense electrolyte layer, a high sintering temperature above 1300oC is usually employed in the fabrication process, which causes considerable amount of time and significant manufacturing costs. Therefore, reducing the sintering temperature and long process time is one of the major challenges to reduce the fabrication cost and facilitate the commercialization of SOFCs. To overcome this problem, many efforts have been made to demonstrate alternative sintering process to reduce the sintering temperature and process time. For example, several researchers proposed spark plasma sintering process as an alternative sintering process because of the high heating rate within a short time based on Joule heating mechanism [1, 2]. However this process has a limitation of complex vacuum system configuration and high equipment cost for commercialization. In addition, excimer laser ablation annealing and microwave sintering process have been also suggested but there are still limitations such as extremely narrow spot size and complexity of microwave interactions with materials respectively [3, 4]. On the other hand, the flash light sintering process presented here uses a white flash light generated by a xenon arc lamp discharge as a heat treatment sources and has many advantages of an extremely short process time, scalability and simple process condition as standard ambient and temperature. Most of all, because this process conducted within a few seconds, it can significantly improve the productivity and cost-effectiveness of the SOFCs. Our previous works successfully demonstrated that the solution-based YSZ thin films was annealed by flash light sintering and it showed comparable material properties to the conventional thermal sintering process [5]. Nevertheless, due to the low light absorption property and difficulty to sinter the ceramic particles, studies on the flash light sintering process for the powder-based films are still limited. In this work, we demonstrate for the first time rapid fabrication of SOFCs using a novel flash light sintering process. The ceramic electrolyte and electrode was fabricated by using mass productive screen-printing method and flash light sintering process was employed as an alternative sintering process of conventional thermal sintering method. In the sintering process, the effect of various pulse conditions on the sinterbility of the ceramic components were investigated, and the material properties such as microstructure, crystallinity and electrochemical property were analyzed. The optimized ceramic components were employed to fabricate SOFC unit cell and their cell performance and impedance behavior was evaluated to demonstrate the flash light sintering process. Reference [1] Deepash Shekhar Saini et al. “Improved conductivity of spark plasma sintered Ho-Substituted Ba-ZrO3 electrolyte ceramics for IT-SOFCs.” ACS Applied Energy Materials. 1, 7, 3469-3478 (2018)[2] Tatiana L. Simonenko et al. “Spark plasma sintering of nanopowders in the CeO2-Y2O3 system as a promising approach to the creation of nanocrystalline intermediate-temperature solid electrolytes.” Ceramics International, 44, 16, 19879-19884 (2018)[3] Hao, H., Xu, L., Huang, Y., Zhang, X. & Xie, Z. “Kinetics mechanism of microwave sintering in ceramic materials.” Science in China Series E: Technological Sciences 52, 2727–2731 (2009).[4] Bayati, R. et al. “Modifcation of properties of yttria stabilized zirconia epitaxial thin flms by excimer laser annealing.” ACS applied materials & interfaces 6, 22316–22325 (2014).[5] Park, J.S. et al. Rapid, cool sintering of wet processed yttria-stabilized zirconia ceramic electrolyte thin films. Scientific reports 7, 12458 (2017)