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.

电解质是电池、燃料电池或超级电容器等能量存储和转换装置的重要组成部分。太阳能和风能的非连续可用性以及电动汽车未来的成功需要大幅推进这些技术。因此，寻找更好的电解质是确保未来可持续能源供应的关键。一类有前途的新型电解质是低共熔溶剂（DES），与其他材料相比，它在易于制备、低成本、可持续性和生物相容性方面具有优越性。 DES 通常由盐和分子氢键供体组成。两种组分的混合会产生典型的共晶熔点降低，使 DES 在室温下呈液态。这可以将在室温下结晶的盐转化为液体电解质。正如在低共熔混合物中经常发现的那样，DES 在冷却得足够快时往往会表现出玻璃化转变。了解 DES 中的离子传输机制是促进其在电化学应用方面优化的一个重要目标。在本项目中，应使用介电谱 (DS) 和核能研究 DES 的离子电荷传输和玻璃形成特性。磁共振 (NMR)，辅以流变学和量热测量。 DS 对离子的平移位移以及偶极分子的重新定向运动敏感，其中两种动力学可以耦合。 NMR 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，NMR 是 DS 的理想补充，DS 覆盖了异常广泛的动态范围，但不提供此类选择性信息。此外，这些方法的组合也非常适合研究离子和分子动力学的玻璃态冻结，因为它们可以提供有关玻璃化转变过程中这些动力学连续减慢的详细信息。这是本发明的目标该项目旨在更好地了解控制 DES 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迄今为止经常被忽视的重定向运动及其与平移离子动力学的相关性。在其他类别的离子导体中，分子重新定向被认为可以通过类似旋转门的机制打开离子电荷传输的途径。我们的目的是澄清这是否也对 DES 发挥作用。此外，我们计划详细研究唯一很少研究的玻璃化转变和 DES 的玻璃态特性。特别是，需要澄清玻璃温度和典型的非阿伦尼亚玻璃动力学如何影响 DES 中的离子电荷传输。