Charging a Li-O₂ battery using a redox mediator

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Non-aqueous lithium-air (Li-O2) batteries offer higher theoretical specific energy than lithium-ion batteries.
• Recharging Li-O2 batteries is hindered by the difficulty of oxidizing solid lithium peroxide (Li2O2) on the cathode.
• This oxidation challenge leads to significant voltage polarization and limits charging rates.

Purpose of the Study:

• To investigate the use of a redox mediator to improve the recharging process of non-aqueous Li-O2 batteries.
• To overcome the limitations of solid-state Li2O2 oxidation during the charging cycle.
• To enhance the charge/discharge efficiency and cycling stability of Li-O2 batteries.

Main Methods:

• Incorporation of tetrathiafulvalene (TTF) as a redox mediator into the Li-O2 battery system.
• Electrochemical analysis to evaluate the effect of TTF on Li2O2 oxidation during charging.
• Charge/discharge cycling tests to assess the performance and stability of the mediated cell.

Main Results:

• The addition of TTF enabled recharging Li-O2 batteries at significantly higher rates than cells without the mediator.
• TTF acts as an electron-hole transfer agent, facilitating the efficient oxidation of solid Li2O2.
• The mediated Li-O2 battery demonstrated stable performance over 100 charge/discharge cycles.

Conclusions:

• Tetrathiafulvalene (TTF) effectively mediates the oxidation of Li2O2, overcoming a major hurdle in Li-O2 battery recharging.
• The use of redox mediators presents a viable strategy for enhancing the practical applicability of non-aqueous Li-O2 batteries.
• This advancement paves the way for developing next-generation high-energy-density batteries.