Ionic Charge Transport and Molecular Reorientation in Deep Eutectic Solvents studied by Dielectric Spectroscopy and Nuclear Magnetic Resonance

通过介电谱和核磁共振研究深共晶溶剂中的离子电荷传输和分子重新取向

• 批准号: 444797029
• 负责人: Professor Dr. Roland Böhmer
• 金额: --
• 依托单位: Lehrstuhl für Experimentelle Physik III
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/444797029?language=en
• 关键词: Ionic; Charge; Transport; Molecular; Reorientation

Electrolytes are essential components of energy-storage and -conversion devices such as batteries, fuel cells or supercapacitors. The non-continuous availability of solar and wind energy and a future success of electromobility require to advance these technologies significantly. Finding better electrolytes, thus, is key to ensuring tomorrow's sustainable energy supply. A promising new class of electrolytes are deep eutectic solvents (DESs), which are superior compared to other materials concerning ease of preparation, low cost, sustainability and biocompatibility. DESs are commonly composed of a salt and a molecular hydrogen-bond donor. The mixing of the two components generates the typical eutectic melting-point reduction, rendering DESs liquid at room temperature. This can transform salts, that otherwise are crystalline at room temperature, to liquid electrolytes. As often found for eutectic mixtures, DESs tend to exhibit a glass transition when cooled sufficiently fast. To understand the ionic transport mechanism in DESs is an important goal to facilitate their optimization with respect to electrochemical applications.Within the present project, the ionic charge-transport and glass-forming properties of DESs shall be investigated using dielectric spectroscopy (DS) and nuclear magnetic resonance (NMR), supplemented by rheological and calorimetric measurements. DS is sensitive to the translational displacements of the ions as well as to the reorientational motions of the dipolar molecules, where the two dynamics can be coupled. NMR is able to detect both dynamics in a mixing-partner-specific manner by employing suitable nuclear probes and isotopomers. Thus, NMR ideally complements DS, which covers an exceptionally broad dynamic range but does not provide such selective information. Moreover, the combination of these methods is also ideal to investigate the glassy freezing of the ionic and molecular dynamics as they can provide detailed information concerning the continuous slowing down of these dynamics in the course of the glass transition.It is the goal of the present project to achieve a better understanding of the microscopic mechanisms that govern the ionic charge transport in DESs. Especially, we wish to explore the so-far often neglected reorientational motion in these materials and its relevance for the translational ion dynamics. In other classes of ionic conductors, the molecular reorientation was, suggested to open pathways for the ionic charge transport via a revolving-door-like mechanism. We aim at clarifying whether this may also play a role for DESs. Moreover, we plan to study the only sparsely investigated glass transition and the glassy properties of DESs in detail. Especially, it needs to be clarified how the glass temperature and the typical non-Arrhenian glassy dynamics affect the ionic charge transport in DESs.

电解液是蓄电池、燃料电池或超级电容器等储能和转换设备的重要组成部分。太阳能和风能的非连续可获得性以及电动汽车的未来成功需要大力推动这些技术的发展。因此，找到更好的电解液是确保明天可持续能源供应的关键。深共晶溶剂(DESS)是一种很有前途的新型电解质，与其他材料相比具有制备简单、成本低、可持续性好和生物相容性好等优点。DESS通常由盐和分子氢键给体组成。这两个组分的混合产生典型的共晶熔点降低，在室温下呈现DESS液体。这可以将在室温下呈结晶状态的盐类转变为液态电解质。就像通常发现的共晶混合物一样，当冷却速度足够快时，DESS往往会出现玻璃化转变。了解DESS中的离子传输机制是促进它们在电化学应用方面优化的一个重要目标。在本项目中，将使用介电光谱(DS)和核磁共振(NMR)结合流变学和热学测量来研究DESS的离子电荷传输和玻璃形成特性。DS对离子的平移位移和偶极分子的重定向运动很敏感，这两种动力学可以耦合在一起。核磁共振能够通过使用合适的核探针和同位素异构体，以混合伙伴特定的方式检测这两种动力学。因此，核磁共振是对DS的理想补充，DS覆盖了非常广泛的动态范围，但不提供这种选择性信息。此外，这些方法的结合也是研究离子和分子动力学玻璃化冻结的理想方法，因为它们可以提供关于这些动力学在玻璃化转变过程中不断减慢的详细信息。本项目的目标是更好地理解支配DESS中离子电荷传输的微观机制。特别是，我们希望探索这些材料中到目前为止经常被忽略的重定向运动及其与平移离子动力学的相关性。在其他类型的离子导体中，分子的重新取向被认为是通过旋转门机制为离子电荷的输运开辟了通道。我们的目的是澄清这是否也会对Dess起到作用。此外，我们还计划详细研究DESS的玻璃化转变和玻璃化性质。特别是，需要阐明玻璃温度和典型的非Arrhenian玻璃动力学如何影响DESS中的离子电荷输运。