Low-dimensional lithium ion conductors

低维锂离子导体

• 批准号: 166864354
• 负责人: Professor Dr. Paul Heitjans
• 金额: --
• 依托单位: Arbeitsgruppe Anorganische Chemie/ Festkörperchemie
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/166864354?language=en
• 关键词: Low; dimensional; lithium; ion; conductors

The project is concerned with the study how Li diffusion is influenced by dimensionality effects. The investigations are to be performed on selected single-crystalline and polycrystalline materials which feature structurally confined diffusion pathways. To this end NMR techniques will be employed which are sensitive to both the mobility of the Li ions and the dimensionality of the diffusion process.One and two dimensional diffusion can be distinguished by means of temperature dependent and frequency dependent 6,7Li NMR spin-lattice relaxation (SLR) measurements. Both 1D and 2D lithium-ion conductors show a characteristic asymmetry of the diffusion-induced SLR NMR rate peak. Furthermore, the rates reveal a characteristic dependence on the Larmor frequency ω0 in the so-called high temperature limit where the mean jump rate 1/τ is much larger than ω0. Typically, at common magnetic field strengths, the frequency ω0/2π(7Li) ranges from 10 to 300 MHz. In the case of 1D diffusion appropriate relaxation models predict a square root dependence of the rate on ω0 and a logarithmic dependence in the case of 2D diffusion. Analogously, the same holds true for SLR measurements performed in the rotating frame of reference where the Larmor frequency is replaced by the locking frequency ω1 being of the order of several kHz. In this case jump processes are covered which are 1000 times slower than those usually probed in the laboratory frame of reference. Even lower jump rates are directly accessible by NMR spin-alignment echo (SAE) measurements which do not require a model to convert decay rates into Li jump rates. The SAE NMR technique is per se sensitive to the geometry of the elementary jump process, and thus to its dimensionality.Besides NMR techniques, for which polycrystalline materials are sufficient, macroscopic methods can be employed in the case of single crystalline samples. Here, the dimensionality of the transport process is reflected by the anisotropy of the mass or charge transport. Macroscopic techniques include impedance spectroscopy, mass tracer measurements and field gradient NMR spectroscopy.

该项目与研究有关，LI差异如何受维度效应的影响。这些投资将在选定的单晶和多晶材料上进行，这些材料具有结构上限制的扩散途径。为此，将采用NMR技术，对li离子的迁移率和扩散过程的尺寸敏感。一个和二维差异可以通过温度依赖性和频率依赖于6,7LI NMR NMR Spin-lattice弛豫（SLR）测量来区分。 1d和2d锂离子导体都显示出扩散诱导的SLR NMR率峰的特征不对称性。此外，速率在所谓的高温限制中揭示了对Larmor频率ω0的特征依赖性，而平均跳跃速率1/τ远大于ω0。通常，在常见的磁场强度下，频率ω0/2π（7Li）的范围为10至300 MHz。在1D扩散的情况下，适当的松弛模型可以预测率对ω0的平方根依赖性和2D扩散的对数依赖性。类似地，对于在旋转的参考框架中执行的SLR测量值也是如此，其中Larmor频率被锁定频率ω1代替了几个KHz的阶。在这种情况下，涵盖了跳跃过程，其速度比实验室参考框架中通常证明的速度慢1000倍。 NMR自旋分配回声（SAE）测量值不需要模型将衰减速率转换为LI跳跃速率的NMR旋转率回声（SAE），甚至可以直接访问较低的跳跃速率。 SAE NMR技术本质上对基本跳跃过程的几何形状敏感，因此对其尺寸敏感。BesidesNMR技术为此，多晶材料足够，可以在单晶样品的情况下采用宏观方法。在这里，质量或电荷传输的各向异性反映了运输过程的尺寸。宏观技术包括阻抗光谱，质量示踪剂测量和现场梯度NMR光谱。