A research team from two US universities may have cracked the reasons for the breakdown of key components in lithium-air batteries.
Teams from MIT, Harvard University, and Cornell University isolated, and been able to study, lithium superoxide— the molecule that may be responsible for the breakdown.
Researchers used a shell of quinone—a molecule used as an energy carrier in biology— to trap the lithium superoxide.
The work demonstrated how encapsulation or physical confinement with specific materials might be a method to prevent electrolyte and cell degradation in the technology, and increase cell cyclability.
Matthew Nava was the lead author of a paper on the work, published in the peer reviewed PNAS (Proceedings of the National Academy of Sciences of the United States of America).
The accidental discovery was made by graduate student Nava when he noticed that lithium peroxide turned blue when it got close to quinone, representing a rare colour change of two reactant solids.
Although the researchers knew the lithium superoxide intermediate should be present in this new material, it was difficult to prove, as the intermediate was buried in a shell of highly coloured quinone, prone to detonation.
Lithium–air batteries operate by electron transfer from a high-surface-area cathode to oxygen gas during discharge, generating lithium peroxide deposits, the crucial storage material for this class of batteries.
Lithium superoxide, formed during charging and discharging, is too unstable and short-lived at room temperature for scientists to reliably study, which made being able to generate and stabilise the intermediate an important step toward developing a viable lithium-air battery.
Lithium-air batteries were thought promising in the 1970s as a potential power source for electric vehicles, offering energy densities that rival gasoline and significantly surpass conventional lithium-ion batteries.
However, scientists have previously been unable to overcome challenges to practical application of this technology, including reversible charging and low cyclability.
Nava— now a postdoc at Harvard University — contributed to the work as a researcher in the laboratory of Henry Dreyfus professor of chemistry Christopher Cummins, who is a senior author of the study along with: Shiyu Zhang from MIT; Katharine Pastore and Kyle Lancaster from Cornell University; and Xiaowen Feng and Daniel Nocera of Harvard.