Rui Shi,Yan’an Li,Jiutao Gao,Ziyang Chen,Xin Zhang,Shanlin Zhang,Zaheer Ud Din Babar,Chengxin Li
This study focused on meeting the stringent stability requirements of tubular segmented-in-series solid oxide fuel cells (SOFCs) in reducing and oxidizing atmospheres. To address this challenge, a bi-layer perovskite ceramic interconnect was designed by controlling the oxygen partial pressure, because of the strong correlation between the conductivity of strontium-doped lanthanum titanate (LST) and the oxygen partial pressure. The LST powder was prepared using solid-phase and sol-gel methods, and their influence on particle size and sintering behavior was compared. LST/lanthanum strontium manganite (LSM) bi-layer ceramic interconnects with varying thicknesses were fabricated through screen printing and co-sintering. The results demonstrate favorable interfacial bonding and excellent chemical compatibility between the ceramic layers. The conductivity of the bi-layer interconnect exhibits a temperature-dependent behavior, peaking at 550 °C. Simulation calculations and research findings validate that the conductivity of the bi-layer interconnect is determined by the thickness of the LSM layer and the oxygen partial pressure at the interconnect interface. Optimal conductivity is achieved with a bi-layer interconnect consisting of approximately 15 μm of LST and 4 μm of LSM. This can be attributed to the efficient regulation of oxygen partial pressure at the interface, effectively mitigating LSM decomposition caused by low oxygen partial pressure and the subsequent reduction in conductivity. These results provide valuable fundamental data and methodology for the development of high-performance interconnects for tubular segmented-in-series SOFCs.
Juan Xie,Fang-Ze Han,Jing-Hui Zhang,Sheng Liu,Yu-Hua Tang,Cheng-Xin Li,Shan-Lin Zhang
La-doped SrTiO 3 (La x Sr 1−x TiO 3 , LST), as the promising ceramic-based interconnect material, usually needs to be sintered in reductive atmosphere at a temperature ≥ 1450 °C, such sintering condition is not friendly to cell fabrication and application. To reduce the sintering temperature of air-sintered LST, seven sintering additives, Bi 2 O 3 , Fe 2 O 3 , Li 2 O, MnO 2 , NiO, V 2 O 5 , and Co 3 O 4 , are added to the LST in this work. The results show that only Co 3 O 4 is conductive to remarkable sintering at the temperatures of 1250 °C. The relative density of LST-3%Co 3 O 4 reaches 92%, while that of the pure LST is only 48%. Moreover, the conductivity of LST-3%Co 3 O 4 achieves 8.2 S/cm at 800 °C in humidified hydrogen, which exceed 5.5 times that of the pure LST. Interestingly, LST-3%Co 3 O 4 exhibits an average TEC of 11.5 × 10 −6 K −1 between 400 and 900 °C, which is very close to that of other components of SOCs .
Ruyan Chen,Yanan Li,Jiahong Li,Changqing Liu,Cheng-Xin Li
The relatively poor sintering ability of lanthanum-doped strontium titanate (LST) interconnects presents a challenge for co-sintering with cell green bodies. This issue needs to be addressed to advance the development of flat-tubular segmented-in-series solid oxide fuel cells (FT-SIS-SOFCs). This work achieved low-temperature fabrication of industrial-sized FT-SIS-SOFCs by establishing a microstructural engineering approach to overcome the intrinsic low sinterability of perovskite-type LST interconnects via Co3O4 modification. The results show that the modification of Co3O4 had a significant promotion effect on the densification of LST by reducing the sintering activation energy and can achieve high density at 1350 °C and excellent structural stability. The modification of Co3O4 can enhance conductivity of LST under an air atmosphere by substitution of Co3+ ions for Ti4+, while it causes a decrease in conductivity under a hydrogen atmosphere due to the reduced concentration of Ti3+. Moreover, the prepared five-cell FT-SIS-SOFCs with a size of 75.8 × 59.5 mm exhibited a high voltage of 5.33 V, peak power density of about 85 mW/cm2 at 800 °C, and excellent long-term stability. Ultimately, 14-cell FT-SIS-SOFCs measuring 151.5 × 59.5 mm were successfully fabricated for the first time, demonstrating excellent output performance and stability as well, with a power density of 96 mW/cm2 at 800 °C.
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