Li-Diffusion in oxide nanotubes and in ordered nanostructured as well as mesostructured layered materials

近年来，纳米材料在材料科学和能源技术领域引起了广泛的关注。在许多情况下，当与它们的粗粒对应物相比时，它们显示出改进的性质。特别是，纳米结构固体的输运或扩散参数的特点是增强的界面区域的体积分数可以显着不同的μ m大小的类似物。在这个项目中，锂的扩散和传输参数，分别为纳米结构的氧化物，如TiO 2和SnO 2（有序的介孔材料，只有几个纳米直径的纳米晶体，纳米片）计划进行研究的阻抗和NMR光谱。特别是，后者提供了一个大的一套互补的技术来研究微观和宏观锂动力学在一个广泛的时间尺度上，包括非常缓慢和非常快的李议案。此外，NMR自旋-晶格弛豫速率，当作为在高T极限中的频率的函数测量时，对给定的扩散过程的维数是敏感的。拟由以下人员制备的材料：例如，在一个实施例中，结构导向的溶胶-凝胶工艺、水热法或电化学阳极氧化将通过丰富的技术组合，如XRD、TEM、XPS、UV-vis和高分辨率MAS NMR（Li，Sn，Ti）以及使用电化学方法（循环伏安法）进行全面表征。该项目的主要目标是研究（表面）形态，结构无序以及几何和维度对Li流动性的影响。例如，在TiO 2和SnO 2的纳米管或纳米片中，Li扩散可能被预期为空间受限的。因此，离子必须使用低维度的迁移路径。

During the last years, nanostructured materials have attracted much attention in materials science and energy technology. In many cases, when compared to their coarse grained counterparts, they show improved properties. In particular, the transport or diffusion parameters of nanostructured solids characterized by an enhanced volume fraction of interfacial regions can be significantly different from their μm-sized analogues. In this project, Li diffusion and transport parameters, respectively, of nanostructured oxides such as TiO2 and SnO2 (ordered mesoporous materials, nanocrystallites of just a few nm diameter, nanosheets) are planned to be studied by impedance and NMR spectroscopy. In particular, the latter offers a large set of complementary techniques to study both micro- and macroscopic Li dynamics on a broad time scale including extremely slow and very fast Li motions. Moreover, NMR spin-lattice relaxation rates, when measured as a function of frequency in the high-T limit, are sensitive to the dimensionality of a given diffusion process. The materials which are intended to be prepared by, e. g., structure-directed sol-gel processes, hydrothermal methods or electrochemical anodization will be thoroughly characterized by a rich portfolio of techniques such as XRD, TEM, XPS, UV-vis and high-resolution MAS NMR (Li, Sn, Ti) as well as by using electrochemical methods (cyclo-voltammetry). The main goal of the project is to study the influence of the (surface) morphology, structural disorder and both the geometry and dimensionality on the Li mobility. For example, in nanotubes or nanosheets of TiO2 and SnO2 Li diffusion might be expected to be spatially confined. Thus, the ions have to use migration pathways of low dimensionality.