Lithium redox imaging for a better battery

A technique developed at Massachusetts Institute of Technology allows, for the first time, the direct observation of the reactions inside advanced lithium-air batteries. Until now, exactly what goes on inside such batteries had been impossible to observe. This new method could help researchers design better batteries. Yang Shao-Horn, senior author of the study said: “We focused on finding out what really happens during charging and discharging.”

The team, whose research has been published in Scientific Reports, used high-intensity X-ray illumination at the Advanced Light Source (ALS) at the Lawrence Berkley National Laboratory (LBNL) in California, one of only two facilities in the world capable of producing such an experiment. The facility made it possible to study the electrochemical reactions taking place at the surface of electrons, and to show the reactions between lithium and oxygen as the voltage applied to the cell was changed.

“The ALS enables the investigation of a wide array of electrochemical studies in real environmental conditions, including the ability to study the surface chemistry of our specially designed sold-state lithium dioxide cell,” explained Ethan Crumlin, a postdoc at LBNL.

Novel solid-state lithium-air batteries were used in the study. When discharging, such batteries draw in some lithium ions to convert oxygen into lithium peroxide. The team were able to produce detailed spectra of how the reaction unfolds, and show that this reaction is reversible on metal oxide surfaces. Metal oxides could potentially enable a lithium-air battery to maintain its performance over many cycles of operation.

Lithium-air batteries could store up to four times as much energy as today’s lithium-ion batteries. However, the development of such batteries has thus far been hindered by a lack of understand of how lithium reacts with oxygen.

“This research points to a new paradigm of studying reaction mechanisms for electrochemical energy storage.” Shao-Horn added.