金属有机配合物作为锂氧气电池液相催化剂的研究

One challenge for the catalyst study of Li-O2 batteries is to solve the catalyst deactivation. An unlimited and dynamic interface between soluble catalyst and Li2O2 can be established by the organic solvent, which is favorable for the promotion of catalytic reaction and improvement of battery performance. There are few researches on the development of soluble catalyst in Li-O2 batteries. Substantial challenges mainly exist on the insufficiency of selection for the electrolyte, poor stability during cell cycling, and unclear catalytic mechanism. The Li-O2 battery using metal complex with controlled structure and performance as soluble catalyst has not been reported thus far. In this work, a series of functional metal complex are designed and synthesized. The relationship between the selection of metal, the design of organic ligands and the catalytic performance of as-prepared samples will be systematically studied. In addition, the electrochemical operando synchrotron radiation-based technique will be employed for tracking the formation and decomposition of Li2O2 during cell cycling. The key factor for the catalyst kinetics of metal complex will be present by fitting and analysis of dynamic process. Furthermore, the catalytic mechanism will be proposed through the combination of physicochemical characterizations, the establishment for relationship between metal selection, ligand design and the catalyst stability and performance, and the study of catalytic kinetics. This work is expected to contribute to the electrode materials development for Li-O2 batteries, the understanding for the fundamental knowledge, and the exploration for application of synchrotron technology on the new energy field.

如何解决催化剂的失效问题一直是锂氧气电池催化剂研究的难点。液相催化剂可通过有机溶剂在其和Li2O2之间建立非受限且动态的界面，从而促进催化反应不断进行，提高电池性能。目前相关研究较少且存在适宜其溶解的电解液选择性单一、稳定性差和催化机理不明等问题。基于结构和性能可控的金属有机配合物作为液相催化剂的锂氧气电池体系还没有被报道。本课题拟通过设计合成系列化和功能化的金属有机配合物，建立中心金属、有机配体设计与催化剂性能的联系。同时，通过采用电化学原位同步辐射技术对电池循环过程中Li2O2的生成和分解进行定量地实时记录，对催化动力学过程进行拟合和分析，揭示影响动力学参数的关键因素。此外，我们将结合多种物化性质的表征手段、中心金属选择、配体设计与催化剂性能的关系以及催化动力学分析对催化机理提出合理的推断。本项目工作将为锂氧气电池电极材料的设计、基础原理的探究以及同步辐射技术在新能源领域的拓宽做出贡献

如何解决催化剂的失效问题一直是锂氧气电池催化剂研究的难点。液相催化剂的添加可将固/固界面的电荷传输转移为液/固界面的电荷传输，从而降低体系界面穿荷阻抗，促进催化反应不断进行，解决电池反应动力学缓慢的问题。然而，研究发现基于液相催化剂的体系易存在“穿梭效应”，这会造成金属锂片不断恶化，最后失效导致电池死亡。本项目从可控合成的角度出发，设计适用于锂氧气电池中的“自我防御型”有机液相催化剂，即提高锂氧气电池反应动力学的同时，实现金属锂负极表面SEI膜的原位构筑，从而提高其循环稳定性。通过整合密度泛函理论计算、电极表/界面物化表征、电化学性能评价等手段阐明影响电池性能的关键性指标、界面化学的演化过程、材料设计与动力学的内在联系等，实现了电池循环性、能量密度等指标的提升。此外，我们还设计了功能型隔膜用于减缓/抑制“穿梭效应”，保护锂负极，继而提高电池循环寿命。通过对比含有和不含有功能化隔膜的电池体系循环过程中电极表/界面组分和形貌的演变，探究反应机理，揭示抑制“穿梭效应”的关键性因素。此外，我们还对隔膜材料种类及比例的选择、可溶性催化剂在反应过程中对容量的贡献等方面做出了重要总结。同时进一步，我们还始创性地提出了锂氧气电池中促进氧化还原介质反应的催化剂设计和合成的具体思路，并对其催化机制做出了合理的推断。本项目工作为锂氧气电池电极材料的设计及基础原理的探究做出了一定的贡献。