Simulation of a Solvate Ionic Liquid at a Polarizable Electrode with a Constant Potential

SW Coles and VB Ivanistsev, JOURNAL OF PHYSICAL CHEMISTRY C, 123, 3935-3943 (2019).

DOI: 10.1021/acs.jpcc.8b09369

Solvate ionic liquids have the potential for use in a wide range of electrochemical devices. The interfacial nanostructure of these liquids largely determines the performance of such applications. In this work, we have focused on the nanostructure and calculated the capacitance of a solvate ionic liquid-electrode interface, where the electrode has a constant potential and is thus inherently polarizable. The first time, to our knowledge, a solvate ionic liquid has been simulated at such an electrode. Lithium cations from the lithium-glyme solvate ionic liquid are found within 0.5 nm of the electrode at all voltages studied, however, their solvation environment varies with voltage, with both lithium cation anion and lithium cation-glyme complexes being observed in the first interfacial layer. Our study provides a molecular insight into the electrode interface of solvate ionic liquids, with many features similar to pure ionic liquids. The profound differences between the structure observed in these simulations and our previous study performed with fixed charge electrode boundary conditions make clear the importance of accurate modeling interfaces when studying solvate ionic liquids. The differences shown here are qualitatively greater than observed for conventional ionic liquids.

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