结构互穿型纳米金属氧化物/碳复合多孔纳米管的构建及其电化学特性

Metal oxides have been considered as potential anodes for Li-ion batteries due to their high theoretical capacity and working voltage. However, the low electrical conductivity and poor Li-ion diffusivity greatly restrict further development of metal oxides electrodes. In order to overcome these issues, an effective approach is to use nanocomposites by adding or coating conductive agents of carbon nanotubes (CNTs), so metal oxides@CNTs 1D nanocomposites have been widely investigated in improving their electrochemical performance. However, the preparation of CNTs in metal oxides@CNTs nanocomposites usually requires complex process control, high temperature and expensive equipments, leading to the high cost and the low yield. Up to now, it remains difficult to facilely prepare CNTs on a large scale. In addition, metal oxides have the larger size, easily aggregate or pulverize. And, the synergistic effect of separated two phases cannot completely exhibite. So it is necessary to design and synthesize new 1D metal oxides@CNTs composites with the special structure and the high performance.. In this proposal, considering the cost and the structural integration, we will clever design and prepare novel nano-sized metal oxides/carbon porous nanotubes with the interpenetrating structure through the saturated adsorption, sol-gel method and pyrolysis. Surface modified and cross-linked degree controlled polymer nanotubes act as a source of carbon and template. Through the saturated adsorption of organic salt solutions containing Ti，Fe，Co，Ni for functional polymer nanotubes, controlling and optimizing the preparation conditions, the superfine (˂10nm) metal oxides nanoparticles such as the deintercalate-type TiO2、Li4Ti5O12 and the redox-type Fe3O4, Co3O4, CoO, NiO, are uniformly embedded in walls of porous carbon nanotubes due to the space confinement of the cross-linked polymer networks, resulting in the formation of nano-sized metal oxides/C porous nanotubes with the interpenetrating structure. The electrochemical properties of nanocomposites are investigated in detail. The relation between the structure, pore size distribution, the mass ratio of C and metal oxides, the interpenetrating degree, the size and dispersity of metal oxides and the electrochemical properties will be systematically discussed. The synergistic effect of two phases in nanocomposites will be elucidated during the electrochemical reaction. These results will provide scientific and theoretical basis for exploitation and application of novel high-performance anode materials for Li-ion batteries.

金属氧化物具有高的理论容量和工作电压，是一类有应用前景的锂电负极材料。针对金属氧化物低的电导率，金属氧化物与碳纳米管复合物中碳纳米管制备方法复杂、成本高、产率低，金属氧化物颗粒大、易团聚、粉化，两相简单包覆不能充分发挥其协同优势等问题，亟待研发独特结构、高性能金属氧化物@碳纳米管一维纳米复合材料。本项目以易修饰及交联度可调的聚合物纳米管为碳源和模板，饱和吸附有机钛、铁， 钴和镍盐溶液、通过溶胶-凝胶过程及后续热处理，控制并优化制备条件，利用聚合物网络的空间限域作用，使超细（˂10nm）脱嵌型TiO2、Li4Ti5O12及氧化还原转换型Fe3O4、Co3O4、CoO和NiO颗粒均匀地嵌入CNTs管壁中，构建一类互穿结构的纳米金属氧化物/碳复合多孔纳米管，研究其电化学性能，建立其构效关系，揭示复合材料的两相在电化学储锂中协同作用机制，为新型高性能锂电负极材料的开发与应用提供科学依据和理论基础。

金属氧化物理论容量和工作电压高、廉价易得，是一类非常有应用前景的二次电池负极材料。但大多金属氧化物属宽带隙半导体材料，低的电子电导率和离子扩散率，以及在脱/嵌锂过程中易出现体积膨胀/收缩、颗粒聚集/粉化等现象，严重限制了该类材料的进一步发展和应用。金属氧化物的纳米化和复合化是解决上述问题的有效途径。通常与CNTs复合构筑金属氧化物@CNT复合材料，可有效改善其电化学性能，但该复合材料中金属氧化物纳米颗粒较大、易团聚、粉化，且两相简单包覆不能充分发挥其协同优势，复合材料机械结构稳定性较差。. 针对上述问题，本项目从结构可融性角度出发，利用聚合物廉价、易修饰、具有交联网络结构及其网络空隙的空间限域效应等特点，通过巧妙设计，采用改性的溶胶凝胶法及后续的煅烧处理构筑了互穿结构金属氧化物/C杂化多孔纳米管，使金属氧化物纳米颗粒嵌入多孔CNTs管壁中，提高CNTs与金属氧化物两相的连续性和兼容性，同时提高材料的机械结构稳定性。从根本上解决了金属氧化物电极材料电子、离子导电性差，在电化学反应中材料易出现体积膨胀/收缩、颗粒聚集/粉化等问题。此外，基于上述基础，采用微波加热、回流、水热等方法构筑了具有电缆结构和封装结构的金属氧化物@CNT复合材料，探讨了其电化学性能，研究了其结构优劣性，研究结果表明互穿结构是最理想的可用于二次电池负极材料的纳米结构。本项目的实施为新型高性能二次电池负极材料的开发与应用提供科学依据和理论基础。