Role of Li Concentration and the SEI Layer in Enabling High Performance Li Metal Electrodes Using a Phosphonium Bis(fluorosulfonyl)imide Ionic Liquid

• DOI: 10.1021/acs.jpcc.7b01929
• Publication Date: 2017-08-23T16:23:55Z
• Authors: Gaetan M. A. Girard; Matthias Hilder; Donato Nucciarone; Kristina Whitbread; Serguei Zavorine; Michael Moser; Maria Forsyth; Douglas R. MacFar...; Patrick C. Howlett
• Keywords: Phosphonium

In this study the performance of lithium (Li) anode is characterized in two alternative ionic liquid electrolytes: (i) a solution 0.5 mol·kg–1 bis(fluorosulfonyl)imide (LiFSI) trimethyl(isobutyl)phosphonium FSI (P111i4FSI) and (ii) an equimolar mixture these salts, effectively inorganic–organic IL. We have investigated formation solid electrolyte interphase (SEI) at electrode its influence on polarization potential, surface impedance deposition morphologies. Lithium metal cycling revealed to be significantly more stable with high salt concentration due creation uniform SEI. Stable effective was demonstrated applied currents (up 12 mA·cm–2) large areal capacities being transferred each cycle 6 mAh·cm–2 50 °C). An average Coulombic efficiency not less than 99.2% under conditions SEM observations cycled surfaces show compact deposit. Combined spectroscopic characterization surface, indicate role for speciation transport properties electrolytes modifiying physicochemical SEI which result enhanced Li electrode.