Studies on the Mechanisms for the Transport of Lithium Ions in Solid-State Composites Using a New Combination of Li NMR Methods

鉴于在能源和信息技术中的高度相关性，大量最近的研究集中在固态电解质中的离子动力学上。尽管有这些努力，我们对固体中离子输运的理解仍然是不完整的，限制了基于知识的新材料设计的可能性。全面的实验表征奠定了基本理解的基础。在这里，我们建议利用固态核磁共振是一个强大的工具来调查复杂的运动的离子在固态电解质。具体来说，我们打算使用6Li和7 Li NMR方法的广谱来确定锂离子在各种时间尺度和长度尺度上的动力学。为了研究微观尺度上的动力学，将首次将受激回波实验和场循环实验结合起来。前者能够直接测量离子运动的相关函数，而后者通过确定自旋-晶格弛豫时间T1的频率依赖性来提供对离子运动的谱密度的访问。这两种技术的时间窗口以理想的方式相互补充，使我们能够覆盖约1000年的时间范围。一个ps - 10。为了研究锂离子在介观和宏观尺度上的输运，计划通过静态场梯度中的NMR实验测量自扩散系数。应用这种新的组合的6Li和7 Li NMR方法的锂离子的运动在不同的时间尺度和长度scales.Our的研究将集中在复合材料，这已经吸引了大量的关注，在寻求固态电解质与改进的材料性能的长距离传输和导电性的基本离子跳跃在一个solid matrix. Our的研究。具体而言，我们建议调查复合材料的固体基质表现出可区分的结构或组合物在不同的空间区域。选择体系的一个重要标准是结构异质性的增加伴随着离子电导率的增加。具体来说，我们研究了（Li_2S）_x（P_2S_5）_（1-x）微晶玻璃和（Li_2S）_0.5-[（1-x）GeS_2-xGeO_2]_0.5混合网络形成玻璃。为了确定这些复合材料的增强的离子电导率的来源，离子传输的机制将根据结构的不均匀性来确定。这些知识将对未来改善固态电解质的导电性非常有用。

In view of a high relevance in energy and information technologies, a large number of recent research studies have focused on the dynamics of ions in solid-state electrolytes. Despite these efforts, our understanding of ion transport in solids is still incomplete, limiting the possibilities of a knowledge-based design of new materials. The foundations for a fundamental understanding are laid by a comprehensive experimental characterization. Here, we propose to exploit that solid-state nuclear magnetic resonance is a powerful tool to investigate complex motions of ions in solid-state electrolytes. Specifically, we intend to use a broad spectrum of 6Li and 7Li NMR methods to ascertain dynamics of lithium ions on a large variety of time scales and length scales. For a study of dynamics on microscopic length scales, stimulated-echo experiments and field-cycling experiments will be combined for the first time. The former enable a direct measurement of correlation functions of the ionic motion, while the latter provide access to the spectral density of the ionic motion via a determination of the frequency dependence of the spin-lattice relaxation time T1. The time windows of both these techniques complement each other in an ideal way, allowing us to cover a time range of ca. 1 ps - 10 s. To study the transport of lithium ions on mesoscopic and macroscopic length scales, it is planned to measure self-diffusion coefficients by means of NMR experiments in static field gradients. Applying this new combination of 6Li und 7Li NMR methods to the lithium ionic motion on various time scales and length scales, we intend to trace back long-range transport and conductivity to elementary ionic jumps in a solid matrix.Our studies will focus on composites, which have attracted a great deal of attention in the quest for solid-state electrolytes with improved material properties. Specifically, we propose to investigate composites where the solid matrix exhibits distinguishable structures or compositions in different spatial regions. An important criterion for the selection of the systems is that an increase of structural heterogeneity is accompanied by an increase of the ionic conductivity. In detail, two interesting examples to be studied are (Li2S)_x(P2S5)_(1-x) glass-ceramics and (Li2S)_0.5-[(1-x)GeS2-xGeO2]_0.5 mixed-network former glasses. In order to ascertain the origin of the enhanced ionic conductivity of these composite materials, the mechanism for the ion transport will be ascertained in the light of the structural heterogeneity. This knowledge will be of great use for a future improvement of the electric conductivity of solid-state electrolytes.