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

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 g-1/carbon 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.