新型类钙钛矿混合导体材料的结构调控及电化学性能的多重响应机理研究

To design and prepare A2BO4 perovskite-like structure materials with higher electrochemical performance is one of the key to developing cathod materials for intermediate temperature solid oxide fuel cells (IT-SOFCs), which has wide study foreground. Doping method is the most effective solution to improve the performance of A2BO4 materials. The electroconductibility, electrochemical performance, and stability of A2BO4 materials changed after doping; the different mechanisms towards conductivity were presented by doping for both A and B sites; the A2BO4 materials electrochemical performance changed due to the differnt functional mechanisms induced by dopant and defect after doping. Based on these key problems as reported above, the A2BO4 materials structure will be directionally regulated, the changes of materials structure characteristics, and the change regularity of multiple response mechanism for both electrochemical performance and their structural control will be investigated, and those different mechanisms will be discussed. The change of electrochemical performance related to the A2BO4 materials structure and composition will be further realized by means of the combination of density functional theory (DFT) calculation and experimental research. The effect of A2BO4 materials structure on the electron transfer, oxygen ion transmission, and surface adsorption oxygen ability will illuminated via the control of their structure. The electrochemical performance match for both cathod materials and conventional eletrolyte will be comprehensively analyzed, and the optimized performance of materials will obtained, which presents theoretical basis for the development of new cathod materials.

设计、制备具有良好电化学性能的A2BO4型材料是满足中温SOFC阴极材料发展的关键之一，具有良好的研究前景。将A2BO4型材料进行掺杂改性是一种最有效的调控材料性能的方法。针对A2BO4型材料掺杂改性后引起的导电性、电化学性能和稳定性的变化，多元复合掺杂后引起的不同导电机理，掺杂离子及缺陷的不同作用机理引起材料电化学性能变化等关键问题，本研究将通过有针对性的定向调控材料结构，研究掺杂前后材料结构特征的变化规律与电化学等性能的多重响应变化规律，探讨出其差别机制。密度泛函理论计算与实验研究相结合，更进一步认识A2BO4型材料结构、组成与导电性能关联变化规律。通过调控A2BO4型材料的结构，阐明材料结构对电子迁移能力、氧离子传输能力、表面吸附氧气能力的影响机制。综合分析阴极材料与常规中低温电解质之间的电化学活性匹配规律，可获得性能优化的材料，为发展新型阴极材料提供理论基础。

K2NiF4(或A2BO4)型类钙钛矿化合物具有离子-电子混合导体(MIEC)特性，可用作中温固体氧化物燃料电池（IT-SOFCs）阴极材料，具有良好的研究前景。本项目通过溶胶-凝胶法、掺杂改性和电化学性能测试技术，结合晶体结构精修方法、第一性原理方法计算重点对PrSrCoO4、Nd2FeO4、A2(A=Sm, Eu)B(B=Cu, Fe)O4系列阴极材料进行了详细研究。首先，通过建立有效的A2BO4型类钙钛矿材料的合成方法与制备工艺，考察了柠檬酸‒硝酸盐法制备PrSrCoO4材料过程中多种常见因素对材料的物相、形貌等的影响，优化了制备工艺。继而成功制备了一系列具有A2BO4结构的类钙钛矿材料。其次，利用复合掺杂方法分别对Pr2-xSrxCo0.9Fe0.1O4、Sm1.9K0.1Cu1-yFeyO4、PrSr1-xNaxCoO4结构进行有针对性的调控，获得了结构稳定的电极材料，建立了易于实施、高效的调变A2BO4材料结构、性质的方法。再次，通过分析PrSrCoO4、PrCaCoO4晶体中非化学计量氧δ值、间隙氧缺陷，结合DFT计算获得材料的能带结构、电子结构等，认识了金属与氧原子之间的化学键的共价性强弱相关性。最后，系统测试了Nd2-xNaxFeO4、Nd2-xCaxFeO4、Nd2Fe1-xCoxO4、Pr2-xSrxCo0.9Fe0.1O4、PrSr1-xNaxCoO4等系列的类钙钛矿材料的电化学性能，获得了具有良好化学稳定性、相容性与电化学性能的电极材料组成与结构，从而进一步认识了掺杂的元素种类、比例、掺杂位置对材料电化学性能的影响机制，并在很大程度上解决了掺杂电极材料与电解质之间的热膨胀系数不匹配的问题，提高了电极材料的循环稳定性能。综合上述结果，本研究为探讨新型A2BO4型类钙钛矿材料的结构调控对物化性质的影响机制奠定了坚实的工作基础。同时对于认识A2BO4型材料结构、组成与导电性能关联变化规律提供了重要的启示性线索。