A versatile functionalized ionic liquid to boost the solution-mediated performances of lithium-oxygen batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-oxygen batteries offer high theoretical specific energy for applications like electric vehicles.
• Challenges include large over-potentials, side-product formation, and short cycle life during operation.

Purpose of the Study:

• To develop a functional electrolyte additive for lithium-oxygen batteries.
• To improve discharge capacity, reduce over-potentials, and enhance cycle stability.

Main Methods:

• Incorporation of a redox-active ionic liquid (2,2,6,6-tetramethyl-1-piperidinyloxy moiety) into the electrolyte.
• Electrochemical cycling and analysis of lithium-oxygen cells with varying ionic liquid concentrations.
• Investigation of lithium anode protection and solid electrolyte interface formation.

Main Results:

• A 33-fold increase in discharge capacity compared to pure ether electrolytes.
• Reduction of over-potential to 0.9 V.
• Facilitation of stable lithium plating/stripping and suppression of side reactions.
• Achieved over 200 cycles with amorphous lithium peroxide formation at high ionic liquid proportions.

Conclusions:

• The developed ionic liquid additive functions as a multi-purpose component: redox mediator, oxygen shuttle, anode protector, and electrolyte solvent.
• Optimized electrolyte composition with the ionic liquid leads to significantly enhanced electrochemical performance and cycle life.
• The system demonstrates outstanding performance, particularly when operated in air.