同轴磷酸铁锂/CNT纳米阵列的制备及其刷电极物理化学、电化学性能研究

Due to the high specific capacity, long span life, nontoxic properties, safety advantage and low cost, LiFePO4 has been established as a promising candidate for the preferred cathode materials for the lithium-ion batteries with the excellent electrochemical performance and the high reliability. Currently, the intensive research has been concentrated on the preparation and the performance investigations for the zero- and one-dimensional LiFePO4 electrode material. And there are few literatures concerning about the synthesis of the free-standing, three-dimensional nano-array of LiFePO4, and the studies of the related formation and electrochemical storage mechanisms. However, the design of the three-dimensional nano-array electrode is a paramount development trend for the lithium-ion batteries with the high energy and power densities. On the other hand, when the electrochemical storage mechanism and the electrode processes are investigated, the porous LiFePO4 electrode is usually simplified as an idea plate electrode, which does not accord with the characteristics of the real porous electrode. The electrochemical storage mechanism and the electrode processes must be studied via a "brush" electrode on the basis of a porous electrode theory. And the as-prepared nano-array LiFePO4 electrode is just a "brush" electrode. Moreover, the potential safety hazards for the lithium-ion batteries generally could be prevented via some macroscopical ways to some extent. However, it is far from enough. In order to clearly understand the corresponding safety issues, it is necessary to systematically investigate the real electrochemical responses and the physicochemical features of the porous electrode. Therefore, in this project, the coaxial nano-array LiFePO4 and LiFePO4/CNT with directionally aligned are prepared and the corresponding formation mechanism is systematically investigated. And most importantly, the electrochemical storage mechanism and the electrode processes are intensively studied via the as-resulting nano-array as a "brush" electrode on the basis of a transmission line model. Lastly, the electrochemical reactions, the charge transfer, the mass transfer and the heat transfer will be modeled and stimulated by Comsol and Ansys.

磷酸铁锂具有比容量高、循环寿命长、安全性好等优点被认为是未来高性能、高安全性锂离子电池的首选正极材料，目前的研究主要集中在零维或一维纳米磷酸铁锂的制备及其性能研究。而对于高定向同轴磷酸铁锂纳米管阵列及其磷酸铁锂/碳管复合阵列的研究还鲜有报道，对其形成机理和电化学储能机制尚未深入研究。但是电极的自支撑三维纳米化设计是获得高容量高功率电池的重要发展方向。另一方面，现在的研究都把磷酸铁锂多孔电极简化为理想平板电极，与多孔电极的特性不符，必须借助多孔电极理论，采用所制备的纳米阵列"刷"电极对其进行研究。此外，对电池安全性的理解也必须从多孔电极的本质入手。因此，本项目提出高定向同轴磷酸铁锂纳米管阵列及其磷酸铁锂/碳管复合阵列的制备，进而以传输线模型为理论依据，以该纳米阵列为"刷"电极，系统研究该体系的电化学储能机理及其电极过程，用Comsol和Ansys模拟仿真其电化学反应、传荷/传质以及传热过程。

面对生存和可持续发展，开发绿色环保、更可持续的电化学存储和转换体系势在必行。面对日益严苛的性能要求，开发性能优异的纳米尺度的阵列电极、薄膜电极成为必然，研究其电化学反应机理、开发相关制备技术意义深远。本项目的主要内容为长径比可控阳极氧化铝（AAO）模板的制备、磷酸铁锂纳米点阵/纳米线的制备及其物理化学、电化学性能的研究、第一性原理和量子化学计算的电化学反应机理研究、电化学阳极氧化及电震荡阳极氧化纳米薄膜的制备及其物理化学、电电化学性能研究等。此外，为了制备具有良好电化学性能的阵列电极，对相关工艺（如AAO的制备工艺、填充工艺、去模板工艺以及披电极工艺等）还做了较为细致的摸索和优化，并设计出了具有一定普适性的实验装置和工艺方法。通过实验和理论计算等方式对所涉及的反应机理等进行了较为深入的探讨，取得了一定的结果。通过调解工艺参数，可控制备孔径可调（最大孔径为400 nm）的、有序度较高的AAO模板，性能指标优于商业化产品。通过真空负压填充工艺，研究了纳米点阵的生长机理，制备了具有良好电化学性能的磷酸铁锂纳米线阵列，其性能指标优于同等纳米颗粒，其电化学性能的相关报道还鲜有报道，为后续的基础研究的继续进行奠定了良好的基础。通过阳极氧化法、振荡阳极氧化法制备了具有高倍率、超长寿命的纳米膜超级电容器，其性能远远鲜有文献报道，并能够远远满足商业化的相关器件的实际诉求。结合扩散动力学模型建立等，优化了电极的构造，极大地改善了锂空气电池的放电深度、倍率性能和寿命。Super P基锂空气电池可以在3000 mA/g的电流密度和1000 mAh/g的容量限制下可逆循环100周以上。通过第一性原理计算，研究了β-NiOOH/β-Ni(OH)2电化学反应机理，电解液DMI的亲核反应机理，其结果与实验数据吻合，为后续的理论研究奠定了良好的基础。特别需要指出的是，通过项目的实施发明了两项用于制备具有高电化学活性的纳米薄膜的制备技术。