Fundamental reactions behind advanced battery technology, revealed in detail by advanced imaging method, could lead to improved materials, reports David L. Chandler of the Massachusetts Institute of Technology’s (MIT) News Office. Exactly what goes inside advanced lithium-air batteries as they charge and discharge has always been impossible to observe directly before the advent of a new technique developed by MIT researchers, whose research has been published the journal Scientific Reports.
Yang Shao-Horn, the Gail E. Kendall Associate Professor of Mechanical Engineering and Materials Science and Engineering who was the senior author of the paper, used a special kind of high-intensity X-ray illumination at one of only two facilities in the world capable of producing such an experiment: the Advanced Light Source (ALS) at the Lawrence Berkeley National Laboratory (LBNL) in California.
That facility made it possible to study the electrochemical reactions taking place at the surface of electrodes, and to show the reactions between lithium and oxygen as the voltage applied to the cell was changed.
The tests used a novel solid-state version of a lithium-air battery made possible via collaboration with Nancy Dudney and colleagues at Oak Ridge National Laboratory (ORNL), Shao-Horn says. When discharging, such batteries draw in some lithium ions to convert oxygen into lithium peroxide. Using ALS, Yi-Chun Lu, a post-doctoral student in Shao-Horn’s lab, and Ethan Crumlin, who received his doctorate from MIT this year and is now at LBNL, were able to produce detailed spectra of how the reaction unfolds, and show that this reaction is reversible on metal oxide surfaces. Lu and Crumlin were the lead authors of the new research paper.
A lack of understanding of how lithium reacts with oxygen has hindered the development of practical lithium-air batteries, the authors say — but this type of battery offers the prospect of storing up to four times as much energy as today’s lithium-ion batteries for a given weight. Most existing lithium-air batteries suffer from large energy losses during charging and discharging, and have been unable to successfully sustain repeated cycles.
This study showed that using metal oxides as the oxygen electrode could potentially enable a lithium-air battery to maintain its performance over many cycles of operation.
The observational method this team developed could have implications for studying reactions far beyond lithium-air batteries, Shao-Horn says. This research, she says, “points to a new paradigm of studying reaction mechanisms for electrochemical energy storage. We can use this technique to study a large number of reactions.”
The work, which also involved six other researchers from ORNL, ALS and MIT, was partly funded by the National Science Foundation and the US Department of Energy.
