'Air-breathing' battery could cut costs of renewable energy storage (Update)

Storage is renewable energy's greatest challenge -- this low-cost sulfur battery may help
One of several laboratory sulfur battery cell designs used in the research. Credit: Felice C. Frankel


Now MIT researchers have developed an "air-breathing" battery that could store electricity for very long durations for about one-fifth the cost of current technologies, with minimal location restraints and zero emissions. The battery could be used to make sporadic renewable power a more reliable source of electricity for the grid.


"This battery literally inhales and exhales air, but it doesn't exhale carbon dioxide, like humans—it exhales oxygen," says Yet-Ming Chiang, the Kyocera Professor of Materials Science and Engineering at MIT and co-author of a paper describing the battery. The research appears today in the journal Joule.



This graph shows the increasing cost of battery chemistries. Credit: Li, Z. Pan, M.S., and Su, L.et al./Joule 2017

Finding the right balance

Development of the battery began in 2012, when Chiang joined the Department of Energy's Joint Center for Energy Storage Research, a five-year project that brought together about 180 researchers to collaborate on energy-saving technologies. Chiang, for his part, focused on developing an efficient battery that could reduce the cost of grid-scale energy storage.


"This meant maybe we weren't focusing on the right thing, with an ever-increasing chemical cost in pursuit of high energy-density," Chiang says. He brought the issue to other MIT researchers. "We said, 'If we want energy storage at the terawatt scale, we have to use truly abundant materials.'"

The researchers first decided the anode needed to be sulfur, a widely available byproduct of natural gas and petroleum refining that's very energy dense, having the lowest cost per stored charge next to water and air. The challenge then was finding an inexpensive liquid cathode material that remained stable while producing a meaningful charge. That seemed improbable—until a serendipitous discovery in the lab.

On a short list of candidates was a compound called potassium permanganate. If used as a cathode material, that compound is "reduced"—a reaction that draws ions from the anode to the cathode, discharging electricity. However, the reduction of the permanganate is normally impossible to reverse, meaning the battery wouldn't be rechargeable.

Still, Li tried. As expected, the reversal failed. However, the battery was, in fact, recharging, due to an unexpected oxygen reaction in the cathode, which was running entirely on air. "I said, 'Wait, you figured out a rechargeable chemistry using sulfur that does not require a cathode compound?' That was the ah-ha moment," Chiang says.

MIT researchers have developed an “air-breathing” battery that could store electricity for very long durations for about a third the price of current technologies, with minimal location restraints and zero emissions. Credit: Massachusetts Institute of Technology



"What this does is create a charge balance by taking oxygen in and out of the system," Chiang says.


Making renewables more reliable


As the battery can discharge over months, the best use may be for storing electricity from notoriously unpredictable wind and solar power sources. "The intermittency for solar is daily, but for wind it's longer-scale intermittency and not so predictable. When it's not so predictable you need more reserve—the capability to discharge a battery over a longer period of time—because you don't know when the wind is going to come back next," Chiang says. Seasonal storage is important too, he adds, especially with increasing distance north of the equator, where the amount of sunlight varies more widely from summer to winter.


"The energy density of a flow battery like this is more than 500 times higher than pumped hydroelectric storage. It's also so much more compact, so that you can imagine putting it anywhere you have renewable generation," Chiang says.

Explore further


More information: Joule, Li, Z. Pan, M.S., and Su, L.et al: "Air-Breathing Aqueous Sulfur Flow Battery for Ultralow-Cost Long-Duration Electrical Storage" www.cell.com/joule/fulltext/S2542-4351(17)30032-6 , DOI: 10.1016/j.joule.2017.08.007
Journal information: Joule

Provided by Massachusetts Institute of Technology


Citation: 'Air-breathing' battery could cut costs of renewable energy storage (Update) (2017, October 11) retrieved 6 June 2020 from https://phys.org/news/2017-10-storage-renewable-energy-greatest-challengethis.html

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