Molecular Dynamics Study of Ionic Liquids in Graphite Nanopores

We performed MD calculations on ionic liquids (ILs) to investigate the effects of solvent and pore size. The slit graphite pore models with three pore sizes 1.6, 2.8, and 4.0 nm were constructed, which confine EMITFSI and EMITFSI/PC. We found that EMI+ and solvent PC form layering structures along the pore walls. For the effects of solvent, the layering of EMI+ is interfered by PC. It was also clarified, for the effects of pore size, that the diffusion coefficients of EMI+ and TFSI- in 1.6 nm pore are significantly large compared with other pore sizes. In the 1.6 nm pore, EMI+ forms triple layering structures. Since this pore size nearly corresponds to the threefold space of molecular thickness, we concluded that the layering of ILs is important for the ionic mobility improvement in nanopores. (c) The Electrochemical Society of Japan, All rights reserved.