Thompson Matthew W, Matsumoto Ray, Sacci Robert L, Sanders Nicolette C, Cummings Peter T
Materials Science and Technology Division , Oak Ridge National Laboratory , Oak Ridge 37831 , Tennessee , United States.
J Phys Chem B. 2019 Feb 14;123(6):1340-1347. doi: 10.1021/acs.jpcb.8b11527. Epub 2019 Jan 31.
Room-temperature ionic liquids (RTILs) are a class of organic salts that are liquid at room temperature. Their physiochemical properties, including low vapor pressure and wide electrochemical stability window, have driven their use as electrolytes in many electrochemical applications; however, the slow transport properties of many RTILs have limited their utility in some applications. This issue is often mitigated by solvating ionic liquids in neutral organic solvents. To date, however, solvent interactions have only been explored for a small number of solvents, particularly acetonitrile and propylene carbonate, at only a few compositions. In this work, we use molecular dynamics simulations in the context of a computational screening approach to study mixtures of ionic liquids in many different solvents at a range of concentrations. Building on prior work, we again find that ionic liquid diffusivity increases monotonically with greater solvent concentration. In contrast to prior work, we find that pure solvent diffusivity, not polarity, is the most influential solvent property on mixture behavior. We also explore the concentration dependence of ionic conductivity and find maxima at intermediate concentrations. Experimental conductivity measurements, inspired by the computational screening study, support this observation with qualitatively consistent results. These results can further guide the selection of solvents for electrochemical applications of RTILs.
室温离子液体（RTILs）是一类在室温下呈液态的有机盐。它们的物理化学性质，包括低蒸气压和宽电化学稳定窗口，推动了它们在许多电化学应用中作为电解质的使用；然而，许多RTILs缓慢的传输性质限制了它们在某些应用中的效用。这个问题通常通过将离子液体溶解在中性有机溶剂中来缓解。然而，迄今为止，仅在少数组成下，针对少数几种溶剂，特别是乙腈和碳酸丙烯酯，研究了溶剂相互作用。在这项工作中，我们在计算筛选方法的背景下使用分子动力学模拟，以研究离子液体在一系列浓度下与许多不同溶剂的混合物。基于先前的工作，我们再次发现离子液体扩散率随着溶剂浓度的增加而单调增加。与先前的工作不同，我们发现纯溶剂扩散率而非极性是对混合物行为最具影响力的溶剂性质。我们还研究了离子电导率的浓度依赖性，并发现中间浓度处存在最大值。受计算筛选研究启发进行的实验电导率测量，以定性一致的结果支持了这一观察结果。这些结果可以进一步指导用于RTILs电化学应用的溶剂选择。
