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

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-oxygen (Li-O2) batteries offer high theoretical energy density but face challenges with electrolyte stability and cycling performance.
• Developing advanced electrolytes is crucial for overcoming these limitations and enabling practical Li-O2 battery applications.

Purpose of the Study:

• To investigate the potential of a room-temperature molten salt mixture, [DEME][TFSI]-LiTFSI, as an electrolyte for Li-O2 batteries.
• To evaluate the electrolyte's properties, including ionic conductivity, viscosity, electrochemical stability, and compatibility with lithium metal.
• To assess the electrochemical performance and cycling behavior of Li-O2 cells using this novel electrolyte.

Main Methods:

• Characterization of the [DEME][TFSI]-LiTFSI electrolyte's physicochemical properties (ionic conductivity, viscosity) at various temperatures.
• Electrochemical stability window and lithium metal compatibility testing.
• Assembly and testing of Li-O2 cells with the [DEME][TFSI]-LiTFSI electrolyte, including galvanostatic cycling and ex-situ analysis (XRD, SEM).
• Evaluation of a Li-ion/oxygen configuration using a carbon-coated Zn0.9Fe0.1O (TMO-C) anode.

Main Results:

• The [DEME][TFSI]-LiTFSI electrolyte exhibits suitable properties for Li-O2 batteries, including good ionic conductivity and electrochemical stability.
• Li-O2 cells demonstrated reversible discharge-charge performance with a capacity of ~13.5 Ah/g-carbon and coulombic efficiency near 100%.
• Ex-situ XRD and SEM confirmed the reversibility of the oxygen reduction and evolution reactions (ORR/OER).
• Cycling at elevated temperatures (30-60°C) showed enhanced energy efficiency and distinct morphology changes in deposited species.

Conclusions:

• The [DEME][TFSI]-LiTFSI molten salt mixture is a promising electrolyte for high-performance Li-O2 batteries.
• The electrolyte facilitates efficient and reversible oxygen electrochemistry, crucial for battery operation.
• Temperature variations impact energy efficiency and electrode morphology, offering insights for optimization.
• Preliminary results suggest potential for ionic-liquid-based Li-ion/oxygen configurations with advanced anodes.