钙掺杂对双钙钛矿阴极材料的性能调控和影响机制研究

112-type double perovskite oxides LnBaCo2O5+δ (Ln = rare earths) have attracted extensive attentions as promising cathode materials for SOFCs because of their faster diffusion coefficient and oxygen transport kinetics. However, there are many problems such as poor stability and high thermal expansion coefficient, which affect the electrochemical stability and commercial application. In order to decrease thermal expansion coefficient, improve durability and reduce cost, this project proposed research A-site Ca ions doped double perovskite of Ln1–xCaxBa1–yCayCo2O5+δ (0 ≤ x < 0.5, 0 ≤ y < 0.5) cathode materials.The surface properties, thermal expansion, stability, high temperature ion-electron transport mechanism and chemical compatibility of Ca ions doped double perovskite will be systematically investigated. The structure and defect types of Ca ion doped in different coordination layers of LnBaCo2O5+δ, and the effects of cathodic electrochemical catalytic activity and its internal mechanism will be investigated in theory. In this project, the low thermal expansion coefficient, excellent electrochemical performance and durability cathode materials will be obtained, with a view to the theory and performance breakthrough for design of the novel high-performance intermediate temperature SOFC cathode to provide guidance on thechnical and theoretical aspects.

112型双钙钛矿LnBaCo2O5+δ(Ln为稀土元素)因具有优异的氧扩散系数和表面交换系数，作为固体氧化物燃料电池(SOFC)阴极引起了人们的广泛关注。然而，该材料存在稳定差和热膨胀系数高等问题，影响着其电化学稳定性和商业化应用前景。从降低该材料热膨胀系数、改善稳定性和降低成本的角度出发，本项目提出研究A位Ca离子掺杂双钙钛矿结构的Ln1–xCaxBa1–yCayCo2O5+δ(0≤x<0.5, 0≤y<0.5)阴极材料。系统地研究Ca离子调控下该材料的表面性质、热膨胀、化学稳定性、高温离子电子输运机制和化学兼容性。从理论上研究在LnBaCo2O5+δ不同配位层间引入Ca离子的结构和缺陷类型，以及对阴极电化学催化活性的影响和内在联系。通过上述研究，以期从理论和性能上获得突破，获得低热膨胀系数、良好电催化性能和高稳定性的阴极材料，为研发高性能中低温SOFC新型阴极提供新的思路和理论基础。

固体氧化化物燃料电池(SOFC)作为一种高效低污染的电化学发电设备，是未来能源体系中可信赖的清洁电源技术。在SOFC中，阴极在电化学反应中扮演者十分重要的角色。本项目提出研究A位Ca离子掺杂双钙钛矿结构的Ln1–xCaxBa1–yCayCo2O5+δ（Ln为Pr、Nd和Sm；LCBC，LCBCC）和Pr1-xCaxBaCoFeO5+δ（PCBCF）阴极材料及B位缺陷的PrBaCo2/3Fe2/3MnxO5+δ（PBCFM）阴极材料。系统地研究了Ca离子调控及缺陷对材料表面性质、热膨胀、化学稳定性、高温离子电子输运机制和化学兼容性。结果表明层状钙钛矿A位掺杂钙和B位缺陷调控有利于改善材料的稳定性和电化学性能。. 采用溶胶凝胶法合成了钙于稀土位掺杂的LCBC和PCBCF阴极及钙离子稀土和B位共掺杂的PCBCC和SCBCC阴极，样品经1000-1050 °C烧结10 h均获得单相双钙钛矿结构，且样品与氧化铈基（SDC和GDC）和镓酸镧基（LSGM）电解质在1000 °C均具有良好的化学兼容性。电导率测试结果证明，样品属于跳跃的小极化子导电模式。除PCBC、PCBCF和SCBCC样品外，其余钙离子掺杂均改善了材料的电导率。钙离子掺杂均明显改善了材料的TEC和稳定性。700 °C测试温度下，最佳钙离子掺杂比例的系列阴极极化阻抗均小于0.1 Ω cm2。此外项目还到了单项双钙钛矿结构的B为缺陷阴极材料PBCFM。研究表明，Fe和Mn共掺杂，及B位引入缺陷的层状钙钛矿阴极材料具有良好的化学兼容性和热稳定性。Fe和Mn共掺杂明显的降低了材料的热膨胀系数。SDC电解质支撑的电池上，800℃时其极化阻抗和输出功率密度0.028 Ω cm2和588 mW cm–2。