基于空间限域生长策略的金属氧化物@碳杂化多孔纳米管的构筑及其储锂(钠)机制研究

Metal oxides have been regarded as the promising anode materials for secondary batteries due to high theoretical capacity, rich sources and easy preparation. However, most of the metal oxides have low electron and ionic conductivity. Meanwhile, the phenomenon that volume expansion/shrinkage and particle aggregation/pulverization are prone to occur in the process of extraction and insertion of Li+/Na+ greatly restricts further development of metal oxides electrodes. Construction of metal oxide@C porous hybrid nanotubes is an optimal choice for the high efficiency utilization of metal oxides electrodes. Notably, the key to the construction of this hybrid structure lies in the selection of carbon skeleton structural supports, which can ensure the metal oxides are firmly and evenly embedded in the porous carbon matrix, control the growth of metal oxides, and maintain a well tubular structure effectively. Whereas, there is no such a kind of carbon skeleton structural supports for the universal construction of well structured metal oxide@C porous hybrid nanotubes.. With all above consideration, a kind of porous CNTs with adjustable wall thickness and space in the wall of porous CNTs is developed in this proposal. The functionalized porous CNTs are used as carbon skeleton structural supports, we will cleverly design and prepare the metal oxide@C porous hybrid nanotubes with stable structure and excellent electrochemical performance through impregnated adsorption, sol-gel and pyrolysis. Based on the space limited growth strategy, the metal precursors are introduced into the wall of functionalized porous CNTs. By controlling and optimizing the preparation conditions, the ultrafine metal oxides nanoparticles are firmly and evenly embedded in wall of the porous CNTs due to the space confinement of the volume in the wall of porous CNTs. The relationship between structure, preparation methods, physical properties and energy storage performance will be studied to reveal their energy storage mechanism, which can provide a scientific and theoretical basis for the exploitation and application of novel high-efficiency anodes for secondary batteries.

金属氧化物理论容量高、来源丰富、易制备，是一类有应用前景的二次电池负极材料。但金属氧化物大多电子、离子导电率低，在脱嵌锂(钠)过程中易出现体积膨胀/收缩、颗粒聚集/粉化。构筑金属氧化物@碳杂化多孔纳米管是实现其高效利用的最优选择。然而，构建此杂化结构关键在碳结构支撑体的选择，其可有效保证金属氧化物均匀的牢牢嵌入多孔碳矩阵，控制金属氧化物生长，使材料维持良好的管状结构。本项目拟开发一种管壁厚度、管壁中空间体积可调的新型多孔CNTs，以此功能化的CNTs为结构支撑体，基于空间限域生成策略，通过浸渍吸附、溶胶凝胶等方法，将金属前驱体引入CNTs管壁中释放的空间体积，进行简单热处理，控制、优化制备条件，以普适的方法构建几类结构稳定、性能优异的杂化结构电极材料，研究其结构、制备途径、物性与储能性能之间的关系，揭示其储能机制，为新型高效二次电池负极材料的研究、开发及应用提供科学依据和理论基础。

金属氧化物理论容量高、来源丰富、易制备、安全可靠，相比于其他二次电池负极材料，是一类有望取代碳材料并可广泛应用的电极材料，但其电子、离子导电率低，在电化学反应过程中易出现体积膨胀/收缩、颗粒聚集/粉化，严重限制了其应用。目前，基于一维纳米材料在电化学储能领域中明显的动力学优势，构筑具有杂化结构的金属氧化物@碳多孔纳米管，将金属氧化物电极材料包裹于3D的导电碳网络中，可有效提高活性材料的电导性，同时能够缓解活性材料在电化学反应过程中易团聚/粉化、体积易膨胀/收缩等问题，且有助于增加活性材料电化学反应活性位点，促进离子扩散，具有潜在的实际应用价值。然而，构建此杂化结构的关键在碳结构支撑体的选择，其可有效保证细小金属氧化物均匀牢牢嵌入多孔碳矩阵，使材料维持良好的管状结构。. 基于此，本项目从结构均匀性及有序性角度出发，开发了一种新型薄壁多孔CNTs，优选其功能化方法，以此结构良好、功能化适中的薄壁多孔CNTs为碳结构支撑体，基于空间限域生成策略，借助该CNTs的薄壁、表面功能化及孔结构特性，选取廉价无机金属盐为原料，通过液相反应，调配反应溶剂，控制金属离子水解及迁移速率，将Fe3+、Co2+、Ni2+等金属离子引入薄壁多孔CNTs管壁，简单热处理后，普适的构建了几类结构稳定、性能良好的金属氧化物(合金)@碳杂化多孔纳米管电极材料，研究了其结构与储能性能之间的关系，揭示了其储能机制。此外，采用可构筑良好杂化结构的有机无机杂化策略，通过改性的溶胶凝胶法制备了一维多孔金属氧化物/CNTs复合材料，探究了其结构特性及电化学性能，研究结果表明此新型薄壁多孔CNTs在构筑具有良好结构及电化学性能的碳基金属氧化物多孔杂化纳米管中具有明显优势，同时此新型薄壁多孔CNTs在锂离子电池、锂硫电池、锌离子混合电容器等储能领域中展现出了良好应用前景。本项目的实施为新型高效二次电池负极材料的开发提供了科学依据和理论基础。