掺氮碳纤维负载三维多孔Fe/N/C自支撑空气电极可控构筑及其锂空气电池性能

Lithium-air batteries are considered to be one of the most promising candidates in energy-storage for high energy density and environmental friendliness. However, the practical application of lithium-air batteries is hindered by several issues such as high overpotential and poor cycling performance. This project focuses on designing and synthesizing the 3D porous Fe/N/C catalysts anchored N-doped hollow carbon fiber core-shell composites, and constructing a freestanding oxygen-electrode. The N-doped hollow carbon fibers are prepared via liquid phase self-template method and polymer modification technology. Iron-based metal-organic frameworks (MOF) are first self-assembly anchored on the surfaces of carbon fibers through in-situ growing process, and then the 3D porous Fe/N/C catalysts anchored N-doped hollow carbon fiber composites are obtained with the subsequent one-step heating treatment process. The final freestanding oxygen-electrodes without binder are achieved through the vacuum filtering process. The study aims to illustrate the inner link between synthesis process conditions and material physical and chemical properties, establishing a theory model for the liquid growth of hollow carbon fibers, revealing the self-assembled mechanism of MOF in-situ growing on the carbon fiber substrate and its evolution law in the heating treatment process, clarifying the formation mechanism of Fe/N/C catalyst’s porous structure and the distribution of Fe and N elements. Based on the experiment and analysis, the influences of composition, structure, morphology and interfacial properties of the electrode materials on the electrochemical performance are investigated, and the relationship between the composition and distribution of Fe/N/C catalytic activity sites and its ORR and OER performance are investigated. The effect of the catalytic on the products during the charge and discharge process can be obtained. The catalytic mechanism can be clearly revealed. Then the establishment of kinetics model is to be realized and energy storage mechanism of the oxygen-cathode can be revealed. The project would provide supports for the application and development of lithium-air batteries by achieving their high capacity, high stability and favorable ORR and OER catalytic performance.

锂空气电池能量密度高、环境友好，前景广阔，但存在过电位高及循环性能差等问题。本项目设计并制备掺氮中空碳纤维负载三维多孔Fe/N/C复合材料，并构筑自支撑空气电极。拟借助液相自模板法和聚合物修饰制备掺氮中空碳纤维，在其表面自组装生长铁基金属有机框架(MOF)，一步热处理制备碳纤维负载三维多孔Fe/N/C复合材料，真空抽滤成型实现自支撑空气电极。阐明合成工艺条件与材料理化性能之间的联系，建立中空碳纤维液相生长模型，揭示MOF在碳纤维上生长的自组装机制及热处理过程中的演变规律，阐明Fe/N/C多孔结构及元素均匀分布的形成机制。研究材料、界面特性与电化学性能的关系，揭示Fe/N/C活性点位组成、分布与ORR和OER的关联，研究催化剂对充放电产物种类、形貌和结构的影响，探究其催化机理，阐明空气电极动力学过程和储能机理，实现空气电极的高容量、高稳定性以及良好催化效能，为锂空气电池应用和开发提供支撑。

锂空气电池具有能量密度高、环境友好等优点，应用前景广阔，但存在过电位高及循环性能差等问题。金属/氮/碳是一类以多孔碳材料作为支撑骨架，过渡金属及氮原子分布在碳材料中的催化剂材料，极具发展前景。.本项目设计并制备三维多孔Fe/N/C复合材料，以含铁MOF的材料为基础，经过水热和高温热处理工艺制备出负载Fe颗粒的三维多孔氮掺杂碳纳米管材料。在此基础上，合成一种镍铁合金/氮/碳复合材料Fe-36Ni/NCNTS。对其合成条件、合成机制和电化学性能进行了系统研究。探究了热处理工艺对其形貌与结构的影响规律，阐明了Fe/N/C多孔结构及Fe、N元素分布的形成机制。研究了作为锂空气电池催化剂时电池的电化学性能，在电流密度为0.1 mA cm-2时，Fe-36Ni/NCNTS电极有高达6550 mAh g-1放电比容量，电池可以稳定循环67次。.同时，通过溶胶凝胶法制备了含镍凝胶前驱体，不同温度下热解制备Ni-N-C复合材料，该材料由高度分散的镍纳米颗粒紧密镶嵌于氮掺杂多孔碳骨架上。另外，以壳聚糖作为原料，通过冷冻干燥结合高温热处理工艺制备了负载Ni颗粒的三维层次孔氮掺杂碳材料。探究了不同合成条件下Ni-N-C复合材料的物相及形貌结构特征，考察其锂空气电池性能，研究了催化剂对充放电产物种类、形貌和结构的影响规律。该Ni-N-C复合材料电极充放电循环达23圈，其首次放电容量为4980 mA h g-1。.在此基础上，合成了ZIF材料和普鲁士蓝前驱体，通过不同温度条件下热解得到两种Co-N-C复合材料。揭示了材料、界面性质与电化学性能的关系，研究了催化剂对放电产物种类、形貌和结构的影响规律，实验研究结合理论计算分析，说明制备的Co-N-C材料具有丰富的活性位点，提升了锂空气电池的催化性能，并对其放电产物进行了分析表征，阐明了空气电极动力学过程和储能机理。 .项目了实现以金属有价框架材料为基础衍生出丰富活性位点的金属/N/C材料，并开展了锂空气电池的催化性能研究，为开发MOF衍生材料在锂空气电池催化剂中的应用提供了借鉴。发表相关论文9篇，授权发明专利5项，培养博士研究生1名、硕士研究生4名。