[Py_1,4]FSI-NaFSI-Based Ionic Liquid Electrolyte for Sodium Batteries: Na⁺ Solvation and Interfacial Nanostructure on Au(111)

Abstract

In this paper, the NaFSI-[Py 1,4 ]FSI/Au(111) interface was investigated using cyclic voltammetry (CV) and in situ atomic force microscopy (AFM). Raman spectroscopy was used to evaluate the Na + solvation in [Py 1,4 ]FSI. It was found that Na coordinates with three FSIforming [Na(FSI) 3 ] 2-. In situ AFM revealed that the interaction of [Py 1,4 ]FSI with Au (111) is much stronger compared to other ionic liquids measured using the same technique. On applying a potential, a force of about 50 nN is required to penetrate through the innermost layer. On addition of low concentration of NaFSI (0.05 M), an insignificant change in the innermost solvation layer was observed, whereas on addition of 0.25 M and 0.5 M NaFSI, a significant change in the interfacial structure was noted. The present study clearly shows that Na + ions vary the ionic liquid/Au(111) interface and could provide insight into the interfacial processes in ionic liquid based sodium batteries.

Advances in sodium secondary batteries utilizing ionic liquid electrolytes

“…6c for Na salt concentration dependency) 79,84,116,119,125,126,135,180 and tend to increase with increasing Na salt concentration in the Na[FSA]-[C 3 180 Molecular dynamics simulations have indicated that clustering of Na + and FSA À ions occurs at high Na[FSA] concentrations, 79,181 enabling site exchange and/or indicates a structural diffusion mechanism for Na + , leading to high transport numbers. Clustering of Na + and FSA À ions and rapid exchange of the Na + ion between different coordination environments have also been suggested in this and analogous IL systems by Raman spectroscopic, 180 NMR spectroscopic, 79,182 and atomic force microscopic 182 studies.…”

Ionic Liquids and Organic Ionic Plastic Crystals: Advanced Electrolytes for Safer High Performance Sodium Energy Storage Technologies

“…The same is true for the Raman bands observed in C 2 mim[TFSI] and C 4 mim[TFSI] systems which together with DFT calculations suggest the presence of predominantly [Na(TFSI) 3 ] 2‐ . Similar complexation has been reported for the [FSI] − anion in the NaFSI/C 4 mpyr[FSI] system using Raman and AFM techniques . NMR studies of NaTFSI/N 2(2O2O1)3 [TFSI] and the mixed anion system (NaFSI/N 2(2O2O1)3 [TFSI]) suggest a similar coordination environment for Na + since diffusion in both systems was similar…”

Atomic Force Spectroscopy on Ionic Liquids

“…As ionic liquids are promising electrolytes for applications containing metallic components such as batteries or electrodeposition, many AFS studies have been performed that focus on the formation of the interface structure in the presence of the dissolved metals. Endres et al [115] [116] reported that the interfacial multilayer structure is not significantly affected after adding small amounts of Na. However, when adding more than 0.25 M of Na, the innermost layers changed, indicating the local formation of [Na(FSI) 3 ] 2− .…”