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Lithium-Air Batteries With More Oomph

Electrochemistry: Modifying the electrode and electrolyte leads to a battery that cycles by forming and decomposing lithium hydroxide, not lithium peroxide

by Mitch Jacoby
November 2, 2015 | A version of this story appeared in Volume 93, Issue 43

By overhauling the guts of a lithium-air battery, researchers in England have come up with a higher performance design that may help move the battery from research labs to consumer products (Science 2015, DOI: 10.1126/science.aac7730). Lithium-air batteries, which draw oxygen from the air to drive battery chemistry, pack roughly 10 times as much energy per weight as lithium-ion batteries. But they operate sluggishly and fail quickly as a result of the electrochemistry products, mainly Li2O2, that form during battery use. Li2O2 tends to form crystals about 2 μm in diameter that clog standard porous carbon electrodes, which reduces charge capacity. Li2O2 also resists decomposition during charging, requiring energy-wasting high voltages to reverse the electrochemistry. Aiming to improve on those limitations, University of Cambridge chemists Tao Liu and Clare P. Grey and coworkers prepared graphene-based electrodes with large pores and added a redox mediator, lithium iodide, to the electrolyte solution. The new battery reversibly forms large LiOH crystals, about 15 μm in diameter, which fill but don’t plug the electrode pores and decompose at low voltage, boosting charge capacity and battery lifetime.

Reaction cycle for new lithium-air battery design.
Credit: Tao Liu
This new electrochemical reaction cycle occurs in a rechargeable lithium-air battery featuring a porous graphene electrode (SEM images) and an iodide electrolyte.


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