Low-Polarization Lithium–Oxygen Battery Using [DEME][TFSI] Ionic Liquid Electrolyte

Abstract

The room-temperature molten salt mixture of N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis(trifluoromethanesulfonyl) imide ([DEME][TFSI]) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt is herein reported as electrolyte for application in Li–O2 batteries. The [DEME][TFSI]–LiTFSI solution is studied in terms of ionic conductivity, viscosity, electrochemical stability, and compatibility with lithium metal at 30 °C, 40 °C, and 60 °C. The electrolyte shows suitable properties for application in Li–O2 battery, allowing a reversible, low-polarization discharge–charge performance with a capacity of about 13 Ah gurn:x-wiley:18645631:media:cssc201701696:cssc201701696-math-0001 in the positive electrode and coulombic efficiency approaching 100 %. The reversibility of the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) is demonstrated by ex situ XRD and SEM studies. Furthermore, the study of the cycling behavior of the Li–O2 cell using the [DEME][TFSI]-LiTFSI electrolyte at increasing temperatures (from 30 to 60 °C) evidences enhanced energy efficiency together with morphology changes of the deposited species at the working electrode. In addition, the use of carbon-coated Zn0.9Fe0.1O (TMO-C) lithium-conversion anode in an ionic-liquid-based Li-ion/oxygen configuration is preliminarily demonstrated.