Wang Jianan, Buzolic Joshua J, Mullen Jesse W, Fitzgerald Paul A, Aman Zachary M, Forsyth Maria, Li Hua, Silvester Debbie S, Warr Gregory G, Atkin Rob
School of Molecular Sciences, The University of Western Australia, Perth 6009, Australia.
School of Molecular and Life Sciences, Curtin University, Perth 6102, Australia.
ACS Nano. 2023 Nov 14;17(21):21567-21584. doi: 10.1021/acsnano.3c06609. Epub 2023 Oct 26.
The physical properties of ionic liquids (ILs) have led to intense research interest, but for many applications, high viscosity is problematic. Mixing the IL with a diluent that lowers viscosity offers a solution if the favorable IL physical properties are not compromised. Here we show that mixing an IL or IL electrolyte (ILE, an IL with dissolved metal ions) with a nonsolvating fluorous diluent produces a low viscosity mixture in which the local ion arrangements, and therefore key physical properties, are retained or enhanced. The locally concentrated ionic liquids (LCILs) examined are 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIM TFSI), 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (HMIM FAP), or 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (BMIM FAP) mixed with 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TFTFE) at 2:1, 1:1, and 1:2 (w/w) IL:TFTFE, as well as the locally concentrated ILEs (LCILEs) formed from 2:1 (w/w) HMIM TFSI-TFTFE with 0.25, 0.5, and 0.75 lithium bis(trifluoromethylsulfonyl)imide (LiTFSI). Rheology and conductivity measurements reveal that the added TFTFE significantly reduces viscosity and increases ionic conductivity, and cyclic voltammetry (CV) reveals minimal reductions in electrochemical windows on gold and carbon electrodes. This is explained by the small- and wide-angle X-ray scattering (S/WAXS) and atomic force microscopy (AFM) data, which show that the local ion nanostructures are largely retained in LCILs and LCILEs in bulk and at gold and graphite electrodes for all potentials investigated.
离子液体（ILs）的物理性质引发了强烈的研究兴趣，但在许多应用中，高粘度是个问题。如果不损害离子液体良好的物理性质，将离子液体与降低粘度的稀释剂混合可提供一种解决方案。在此我们表明，将离子液体或离子液体电解质（ILE，一种溶解有金属离子的离子液体）与非溶剂化的氟代稀释剂混合，会产生一种低粘度混合物，其中局部离子排列以及因此的关键物理性质得以保留或增强。所研究的局部浓缩离子液体（LCILs）是1 - 己基 - 3 - 甲基咪唑鎓双（三氟甲基磺酰）亚胺（HMIM TFSI）、1 - 己基 - 3 - 甲基咪唑鎓三（五氟乙基）三氟磷酸盐（HMIM FAP）或1 - 丁基 - 3 - 甲基咪唑鎓三（五氟乙基）三氟磷酸盐（BMIM FAP），它们与1,1,2,2 - 四氟乙基2,2,2 - 三氟乙基醚（TFTFE）按离子液体与TFTFE的质量比为2:1、1:1和1:2混合，以及由质量比为2:1的HMIM TFSI - TFTFE与0.25、0.5和0.75的双（三氟甲基磺酰）亚胺锂（LiTFSI）形成的局部浓缩离子液体电解质（LCILEs）。流变学和电导率测量表明，添加的TFTFE显著降低了粘度并提高了离子电导率，循环伏安法（CV）表明在金电极和碳电极上电化学窗口的减小幅度最小。这可由小角和广角X射线散射（S/WAXS）以及原子力显微镜（AFM）数据来解释，这些数据表明，在所研究的所有电位下，局部离子纳米结构在本体以及金电极和石墨电极处的LCILs和LCILEs中基本得以保留。
