Tailoring electrolyte activity for a highly stable LiOH redox process in lithium-oxygen batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-oxygen (Li-O2) batteries have high theoretical energy density but face challenges with cycle life and overpotentials.
• Lithium hydroxide (LiOH) chemistry offers better environmental tolerance than Li2O2 but suffers from high charging overpotentials due to its four-electron redox process.

Purpose of the Study:

• To enhance the efficiency and cycle life of Li-O2 batteries by optimizing the LiOH redox process.
• To overcome electrode-electrolyte contact limitations and reduce charging overpotentials in LiOH-based systems.

Main Methods:

• Integration of 1-phenylpyrrolidine (PPD) as a redox mediator in an ionic liquid electrolyte (C3C1im TFSI).
• Engineering the ionic liquid to control water reactivity and maintain hydrogen-bond networks for selective LiOH formation.
• Investigating the electrolyte-mediator synergy to shift the charging mechanism to a solution-mediated chemical route.

Main Results:

• Achieved 180 stable charge-discharge cycles, a significant improvement in cycle life.
• Markedly reduced charging overpotentials compared to conventional LiOH-based systems.
• Demonstrated a shift from interfacial charge transfer to a fast, solution-mediated chemical charging pathway.

Conclusions:

• The tailored electrolyte-mediator system enables an efficient and durable LiOH redox process in Li-O2 batteries.
• Molecular-level design principles for electrolyte activity are crucial for high-performance Li-O2 batteries.
• This approach offers a promising strategy for advancing Li-O2 battery technology.