The University of Waterloo (Ontario, Canada – not far from Niagara Falls) News, reported, “Chemists make breakthrough on the road to creating a rechargeable lithium-oxygen battery.” Dr. Linda Nazar, Canada Research Chair in Solid State Energy Materials, led a team that “Resolved two of the most challenging issues surrounding lithium-oxygen batteries, and in the process created a working battery with near 100 per cent coulombic efficiency.”
The new work, which appears this week in the journal Science, Proves that four-electron conversion for lithium-oxygen electrochemistry is highly reversible.” Waterloo is the first to achieve this, doubling electron storage in lithium-oxygen (Li-O2 – also known as lithium-air) batteries. The video below touches on this and a great many other chemistries.
Dr. Nazar explains, “There are limitations based on thermodynamics. Nevertheless, our work has addressed fundamental issues that people have been trying to resolve for a long time.” As noted in the abstract for the Science paper, when Dr. Nazar and her colleagues changed from using an organic electrolyte to an inorganic molten salt, and replaced a porous carbon cathode to “a bifunctional metal oxide catalyst,” they reduced cell degradation and electrolyte consumption. This extended cycle life and produced near 100-percent Coulombic efficiency (almost every electron that goes into the battery is stored and available for output when called upon).
They achieve the near-theoretical energy density of Li-O2 cells while giving a “highly-reversible” charge/discharge characteristic and long life.
The lead author on the study is Chun Xia, a postdoctoral fellow, and co-author is Chun Yuen Kwok, a PhD student, both in Nazar’s lab.
The Natural Sciences and Engineering Research Council of Canada in part funded the project through their Discovery Grants and Canada Research Chair programs, along with the U.S. Department of Energy’s Joint Center for Energy Storage Research.
The abstract for the Science article, “A high-energy-density lithium-oxygen battery based on a reversible four-electron conversion to lithium oxide,” includes reasons lithium-oxygen cells have not been successful up to now.
Batteries based on lithium metal and oxygen could offer energy densities an order of magnitude larger than that of lithium ion cells. But, under normal operation conditions, the lithium oxidizes to form peroxide or superoxide. Xia et al. show that, at increased temperatures, the formation of lithium oxide is favored, through a process in which four electrons are transferred for each oxygen molecule (see the Perspective by Feng et al.). Reversible cycling is achieved through the use of a thermally stable inorganic electrolyte and a bi-functional catalyst for both oxygen reduction and evolution reactions.”
Another report in Science magazine adds to the potential for Dr. Nazar and her team’s findings.
Since lithium-oxygen batteries could store up to 10 times more power than their “conventional” lithium cousins, rail-car-sized batteries could act as backups for a green energy grid. “Storing excess wind and solar power and delivering it on demand.”
So far, the Nazar team’s batteries have no degradation out to 150 cycles. As they demonstrate further charge/discharge cycles, they will eventually show their ability to take on the big jobs of the future. Although today’s lithium-oxygen batteries require further development, the idea of a 10 times improvement in energy density and long cycle life would certainly find a place in the green flight realm.