Spectroscopic Characterization of the SEI Layer Formed on Lithium Metal Electrodes in Phosphonium Bis(fluorosulfonyl)imide Ionic Liquid Electrolytes

• DOI: 10.1021/acsami.7b18183
• Publication Date: 2018-01-29T19:21:57Z
• Authors: Gaetan M. A. Girard; Matthias Hilder; Nicolas Dupre; Dominique Guyomard; Donato Nucciarone; Kristina Whitbread; Serguei Zavorine; Michael Moser; Maria Forsyth; Douglas R. MacFar...; Patrick C. Howlett
• Keywords: Phosphonium; Imide; Magic angle spinning

The chemical composition of the solid electrolyte interphase (SEI) layer formed on surface lithium metal electrodes cycled in phosphonium bis(fluorosulfonyl)imide ionic liquid (IL) electrolytes are characterized by magic angle spinning nuclear magnetic resonance (MAS NMR), X-ray photoelectron spectroscopy (XPS), fourier transformed infrared spectroscopy, and electrochemical impedance spectroscopy. A multiphase layered structure is revealed, which shown to remain relatively unchanged during extended cycling (up 250 cycles at 1.5 mA·cm–2, 3 mA h·cm–2, 50 °C). main components detected MAS NMR XPS after several hundreds LiF breakdown products from anion including Li2S. Similarities observed case dilute (0.5 mol·kg–1 Li salt IL) highly concentrated (3.8 cycling. system found promote formation a thicker more uniform SEI with larger amounts reduced species anion. These features thought facilitate stable efficient tendency for dendrite formation.