玻璃和云母复合封接SOFC电池堆性能

Sealing Properties of SOFC Stack Sealed by Mica and Glass Composite

封接技术是影响平板式固体氧化物燃料电池(SOFC)发展的关键技术之一。实验中用云母和Bi2O3-BaO-SiO2-RxOy(R=K,Zn,Al2O3,etc.)玻璃复合,将电解质(氧化钇稳定氧化锆,YSZ)支撑的电池和金属连接体(SUS430不锈钢)封接在一起,对封接后电池堆的封接性能和开路电压以及各组元热膨胀性能进行测试。结果表明:云母在室温到720℃的平均热膨胀系数为8.5×10-6 K-1,Bi2O3-BaO-SiO2-RxOy玻璃20℃到520℃的平均热膨胀系数为11.0×10-6/K,与YSZ和金属连接体匹配。云母的层状结构可以缓解因热膨胀系数不同而产生的应力,在高温状态下云母还能起到固定软化玻璃的作用。通过气密性和电性能测试,在电池堆工作状态下气密性良好,在操作温度为800～900℃下运行28小时,电池堆的开路电压(OCV)维持在1.0V以上,复合封料及其两边材料中的元素没有明显扩散。因此,云母和玻璃Bi2O3-BaO-SiO2-RxOy复合封接技术可适用于高温SOFC的封接。

Sealing has been identified as one of the key technologies for the development of planar solid oxide fuel cells（SOFCs）.In this work,mica and Bi2O3-BaO-SiO2-RxOy（R=K,Zn,Al2O3,etc.） glass were used as sealants for SOFC stack,by which cells supported by yttria-stabilized zirconia（YSZ） electrolyte were connected with interconnectors of SUS430 steel.Coefficient of thermal expansion（CTE）,seal performance and open circuit voltage（OCV） were determined by the experiments.Microstructure of the interface was studied by the scanning electron microscopy（SEM）.The average CTE of mica from room temperature to720℃ is 8.5×10-6 K-1 and the average CTE of the Bi2O3-BaO-SiO2-RxOy glass from 20℃ to 520℃ is 11.0×10-6 K-1.Thermal expansion of sealing materials was matched to the YSZ electrolyte and the steel interconnector.The layered structure of mica can relieve the stresses arising from different CTE values of the YSZ and SUS430 steel.Under high temperatures,mica also moderates the fluidity of the soft sealing glass materials.Good sealing properties have been found from gas-tightness experiments.The stack with the above sealing materials could keep OCV above 1.0V at operating temperature for 28 hours.Moreover,it was not obviously found the element diffusions in YSZ/sealant/SUS430 steel.This sealing method can therefore meet the application requirements of the SOFC stack.