中温固体氧化物燃料电池LSCF阴极衰减机理及提高稳定性研究

Solid oxide fuel cell (SOFC) is a clean energy conversion device that converts energy in a highly efficient way. However，the performance degradation becomes one of the most important issues hampering applications of SOFC cathodes. In this study, variations of the electrochemical impedance spectra and the overpotential of LaxSr1-xCoyFe1-yO3-δ (LSCF) cathodes will be measured to investigate the performance degradation. Degradation mechanisms under the condition of different temperature, current density and oxygen partial pressure will be studied by comparing the differences of phases, microstructure and element compositions of LSCF cathodes before and after operations. The method of stability enhancement will be developed after the reveal of degradation reasons. LaNi0.6Fe0.4O3 (LNF) or Ba2CoMo0.5Nb0.5O6-δ (BCMN) will be introduced into LSCF cathodes by impregnation. Solid state membranes of the introduced phases with homogeneous small particles will be formed on the surface of LSCF cathodes after quick sintering. These can suppress the performance degradation and enhance the stability of cathodes. This study has contribution to reveal the essence of performance degradation of LSCF cathodes and develop the method of degradation suppression, which gives supports to the stability enhancement of SOFC devices.

固体氧化物燃料电池（SOFC）是一种高效、清洁的能量转化装置。阴极材料的性能衰减是阻碍SOFC得到广泛应用的重要原因。本项目拟利用电化学方法测试LaxSr1-xCoyFe1-yO3-δ（LSCF）阴极的电化学阻抗谱和过电位的变化，研究阴极性能发生衰减的规律。通过分析工作一定时间前后LSCF阴极相组成、微观结构、元素分布的变化，对其在不同温度、电流密度和氧分压条件下的衰减机理进行研究。在此基础上，重点对提高阴极稳定性措施进行探索，采用溶液浸渍法引入高稳定性的LaNi0.6Fe0.4O3（LNF）或者Ba2CoMo0.5Nb0.5O6-δ（BCMN）相到LSCF阴极中，配合使用快速烧结工艺在阴极表面引入颗粒小，分布均匀的固态薄膜层，以有效抑制阴极衰减，提高阴极稳定性。项目的实施有利于剖析阴极性能发生衰减的本质原因，并提出抑制性能衰减的措施，为得到高稳定性的SOFC装置提供理论支持。

本项目研究了固体氧化物燃料电池LaxSr1-xCoyFe1-yO3-δ（LSCF）阴极在工作条件下的性能衰减机理，并对抑制衰减措施进行了探索。已完成的主要工作有（1）研究了LSCF阴极在不同温度和不同极化电流密度下的稳定性，重点研究了Sr析出对电极稳定性的影响。热作用会导致阴极性能持续衰减，并且温度越高，发生衰减的速度越快，阴极电流极化抑制了Sr在LSCF表面的析出，长时间的电流极化会使阴极性能持续衰减；（2）研究了氧分压对溶液浸渍法制备的LSCF-SDC阴极的稳定性的影响规律，结果表明降低氧分压会抑制SrO的析出过程，导致阴极的衰减变慢；（3）采用掺杂法提高LSCF阴极性能。Nb掺杂有利于提高LSCF阴极在工作条件下的性能稳定性。本研究剖析阴极性能发生衰减的本质原因，对SOFC相关研究有重要贡献。