Elverfeldt Carl-Philipp, Lee Young Joo, Fröba Michael
Institute of Inorganic and Applied Chemistry , University of Hamburg , Martin-Luther-King-Platz 6 , 20146 Hamburg , Germany.
ACS Appl Mater Interfaces. 2019 Jul 10;11(27):24423-24434. doi: 10.1021/acsami.9b06445. Epub 2019 Jun 25.
Thermal and dynamic properties of ionic liquid (IL)-based electrolytic solution (LiTFSI in Pyr13TFSI; 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide = Pyr13TFSI) confined in nanoporous polymer hosts were investigated with respect to the pore size/porosity and the surface chemistry of the polymer host. As host material, mesoporous resorcinol-formaldehyde (RF) polymer monoliths with three-dimensionally connected pore structure were prepared, with precise control of the pore size ranging from ca. 7 to 60 nm. Thermal analysis of RF polymer-ionic liquid composites showed stability up to almost 400 °C and a melting point depression proportional to the inverse of the pore diameter. Good ionic conductivity comparable to that of a commercial separator is obtained, which is dependent on the porosity (i.e., pore volume) of the confining host material (i.e., the number of charge carriers available in the system). Further pulsed field gradient (PFG) NMR experiments revealed that the diffusion coefficient of Pyr13 cation becomes smaller than that of TFSI anion inside RF pores, which is contradictory to the bulk IL system. This change in the ionic motion is due to electrostatic attraction between the pore walls and Pyr13 cations, resulting in a layer structure composed of a Pyr13 cation-rich layer adsorbed at the pore wall surface and a TFSI anion-enriched bulklike layer at the pore center. Our study suggests that transport characteristics of the ions of interest can be controlled by optimizing the surface chemistry of the host framework and their motion can be separately monitored by PFG NMR spectroscopy.
研究了限制在纳米多孔聚合物主体中的离子液体（IL）基电解液（1-甲基-1-丙基吡咯烷鎓双（三氟甲基磺酰）亚胺中的双三氟甲烷磺酰亚胺锂（LiTFSI）= Pyr13TFSI）的热性能和动力学性能，涉及聚合物主体的孔径/孔隙率和表面化学。作为主体材料，制备了具有三维连通孔结构的介孔间苯二酚-甲醛（RF）聚合物整体材料，精确控制孔径范围约为7至60 nm。RF聚合物-离子液体复合材料的热分析表明，其稳定性高达近400°C，熔点降低与孔径的倒数成正比。获得了与商业隔膜相当的良好离子电导率，这取决于限制主体材料的孔隙率（即孔体积）（即系统中可用的电荷载流子数量）。进一步的脉冲场梯度（PFG）NMR实验表明，在RF孔内，Pyr13阳离子的扩散系数小于TFSI阴离子的扩散系数，这与本体IL系统相反。离子运动的这种变化是由于孔壁与Pyr13阳离子之间的静电吸引，导致形成了一种层状结构，该结构由吸附在孔壁表面的富含Pyr13阳离子的层和位于孔中心的富含TFSI阴离子的类似本体的层组成。我们的研究表明，可以通过优化主体框架的表面化学来控制目标离子的传输特性，并且可以通过PFG NMR光谱分别监测它们的运动。
