In Situ Atomic Force Microscopic Studies of the Interfacial Multilayer Nanostructure of LiTFSI-[Py_{1, 4}]TFSI on Au(111): Influence of Li⁺ Ion Concentration on the Au(111)/IL Interface

In this paper, we present results on the nanoscale interactions of LiTFSI-[Py_{1, 4}]TFSI with Au(111) using cyclic voltammetry and atomic force microscopy (AFM). Raman spectroscopy was used to understand the Li⁺ ion coordination with the TFSI^- ion and showed that with increase in LiTFSI concentration in [Py_{1, 4}]TFSI, the Li⁺ ion solvation structure significantly changes. Correspondingly, the force-distance profile in AFM revealed that at lower concentrations of LiTFSI (0.1 M) a multilayered structure is obtained. On increasing the concentration of LiTFSI (0.5 and 1 M), a significant decrease in the number of interfacial layers was observed. With change in the potential, the interfacial layers were found to vary with an increase in the force required to rupture the layers. The present study clearly shows that Li⁺ ions vary the ionic liquid/Au(111) interface and could provide insight into the interfacial processes in ionic liquid based lithium batteries.