Quantification of Dynamic Ion Correlations in Highly Concentrated Liquid Electrolytes and of their Implications for Charge and Mass Transport

盐：溶剂摩尔比高达1：1的高浓度液体电解质在电池和超级电容器的电化学能量存储领域中的应用中表现出有前途的性能。由于高离子浓度，在阳离子和阴离子的运动中发生强的方向相关性，这影响电荷和质量传输。传输特性的理论描述可以在Onsager形式主义的框架中结合线性响应理论来完成。对于传输参数的实验表征，通常只要绝对必要，就可以组合尽可能多的测量变量。这可能导致所获得的传输系数的相对较大的不确定性区间。本项目超越了这种方法，通过将电化学测量与基于NMR的传输测量相结合，以确定一个绝对必要的测量变量。结合详细的不确定性分析，非常精确的值的Onsager传输系数将获得选定的电解质，产生有关电荷和质量传输特性的准确信息。这种方法适用于三种Li+导电液体电解质体系：（i）基于有机碳酸酯的高浓度电解质;（ii）基于环丁砜的高浓度电解质;（iii）以碳酸酯作为盐配位溶剂和氟化醚作为非配位溶剂的局部高浓度电解质。通过改变具有不同Li+配位强度（FSI-较弱，BF 4-较强）的阴离子的锂盐，将改变阳离子-阴离子和阳离子-溶剂相互作用，并且将检查这些相互作用对电荷和质量传输的影响。在此基础上，将制定关于如何平衡高浓度电解质中的相互作用的指导方针，以便实现最佳的电荷和质量传输特性。通过这种方式，该项目将有助于提高对高浓度电解质相互作用与储能电池传输特性之间关系的基本理解。

Highly concentrated liquid electrolytes with molar ratios of salt: solvent of up to 1:1 exhibit promising properties for applications in the field of electrochemical energy storage in batteries and supercapacitors. Due to the high ion concentrations, strong directional correlations occur in the movement of cations and anions, which influence both charge and mass transport. A theoretical description of the transport properties can be done in the framework of the Onsager formalism in combination with linear response theory. For the experimental characterization of the transport parameters, typically just as many measured variables are combined as are absolutely necessary. This can lead to relatively large uncertainty intervals for the obtained transport coefficients. The present project goes beyond this approach, as by combining electrochemical measurements with NMR-based transport measurements in order to determine one more measured variable as absolutely necessary. In combination with a detailed uncertainty analysis, very precise values for the Onsager transport coefficients are to be obtained for selected electrolytes, yielding exact information about charge and mass transport properties. This approach is applied to three Li+- conducting liquid electrolyte systems: (i) Highly concentrated electrolytes based on organic carbonates; (ii) Sulfolane-based highly concentrated electrolytes; (iii) Localized high concentration electrolytes with a carbonate as a salt-coordinating solvent and a fluorinated ether as a non-coordinating solvent. Through the variation of lithium salts with anions of different Li+ coordination strength (FSI- weaker, BF4- stronger), cation-anion and cation-solvent interactions will be varied, and the influence of these interactions on charge and mass transport will be examined. Building on this, guidelines are to be drawn up on how the interactions in highly concentrated electrolytes can be balanced in such a way that the best possible charge and mass transport properties are achieved. In this way, the project will contribute to an improved fundamental understanding of the relationships between interactions in highly concentrated electrolytes and transport properties in energy storage cells.