Metal-Ion Diffusion in Ionic Liquid Studied by Electrochemical Scanning Electron Microscopy with X‑ray Fluorescence Spectrometry

Investigating metal-ion transport in ionic liquid media is important to realize batteries and electrodeposition, which utilize intriguing properties of the media. An in situ electrochemical scanning electron microscopy together with X-ray fluorescence spectrometry is developed by a simple modification of an instrument as a tool for the investigation. Diffusion of silver ions (Ag+) in an ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonylamide (BMI-TFSA) is monitored as the time variation of Ag+ concentration during the anodic dissolution of a silver electrode. The results are analyzed by a digital simulation of the diffusion layer based on Fick’s law. The diffusion coefficient of Ag+ is unexpectedly varied according to the concentration, and the tendency of variation is discussed in terms of viscosity change.