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article imageScientists have developed a true lithium-air battery

By Karen Graham     Mar 22, 2018 in Science
Researchers at the University of Illinois at Chicago and the Argonne National Laboratory have designed a new lithium-air battery that works in a natural-air environment while continuing to function after hundreds of charge-discharge cycles.
"Our lithium-air battery design represents a revolution in the battery community," said Amin Salehi-Khojin, assistant professor of mechanical and industrial engineering and co-corresponding author of the paper that was published in the journal Nature.
"This first demonstration of a true lithium-air battery is an important step toward what we call 'beyond lithium-ion' batteries, but we have more work to do in order to commercialize it."
As a replacement for lithium-ion, Metal-air batteries, specifically zinc-air, have created a lot of excitement in the battery sector. Theoretically, they can hold nine-times more energy than a lithium-ion battery. A Lithium-air battery potentially has 5–15 times the specific energy of a Lithium-ion battery as of 2016.
Charge-discharge diagram for a lithium-air battery
Charge-discharge diagram for a lithium-air battery
However, there are very few lithium-air batteries that are capable of running on air instead of pure oxygen. And, they can only be recharged about 10 times before the lithium salts clog up the electrodes, according to Chemistry World.
The vision of a lithium-air battery
In a perfect world, researchers say a lithium-air battery works by combining the lithium present in the anode with oxygen from the air to produce lithium peroxide on the cathode during the discharge phase. The lithium peroxide would be broken back down into its lithium and oxygen components during the charge phase.
However, the problem is that nitrogen, carbon dioxide, and water vapor in the air react with ions at the battery's electrodes, gumming them up and preventing the electrodes from holding a charge. This is why pure oxygen, which has no other components, has been tried in what they call lithium-oxygen batteries.
File photo: Cutaway rendering of the battery pack in the Chevrolet Volt.
File photo: Cutaway rendering of the battery pack in the Chevrolet Volt.
General Motors
These experimental batteries have relied on tanks of pure oxygen, but doing so limits their practicality and poses serious safety risks due to the flammability of oxygen, reports Science Daily.
"A few others have tried to build lithium-air battery cells, but they failed because of poor cycle life," said Larry Curtiss, co-principal author, and Argonne Distinguished Fellow.
Overcoming the problem
To overcome the problem of poor cycle life, the UIC-Argonne research team came up with a unique combination of an anode, cathode, and electrolyte -- the three main components of any battery - creating a system comprising a lithium carbonate-based protected anode, a molybdenum disulfide cathode, and an ionic liquid/dimethyl sulfoxide electrolyte.
The research team electrochemically deposited lithium carbonate and carbon onto lithium chips. This coating allows lithium ions to pass through but stops the nitrogen, carbon dioxide and water vapor from coming in contact with the reactive lithium at the electrode surface.
In experimental designs, the cathode in a lithium-air battery is where the air enters the electrolyte through a carbon-based spongy lattice structure. Salehi-Khojin and his colleagues coated the lattice structure with a molybdenum disulfate catalyst and used a unique hybrid electrolyte made of ionic liquid and dimethyl sulfoxide, a common component of battery electrolytes,
Robert Klie  Mohammad Asadi  Amin Salehi-Khojin and Fatemeh Khalili. (Photo: Jenny Fontaine)
Robert Klie, Mohammad Asadi, Amin Salehi-Khojin and Fatemeh Khalili. (Photo: Jenny Fontaine)
UIC Today
‘The beauty of this design is that we can get all the benefits of a pure oxygen atmosphere while using air,’ Salehi-Khojin says. ‘The components of the battery isolate nitrogen, carbon dioxide, and water vapor so they can’t participate in unwanted side reactions."
"The complete architectural overhaul we performed on this battery by redesigning every part of it, helped us enable the reactions we wanted to occur and prevent or block those that would ultimately cause the battery to go dead," said Salehi-Khojin.
This research suggests the future development of lithium-air batteries may not be restricted to using purified air streams, opening the way for safer batteries for electric vehicles.
The UIC team built, tested, analyzed and characterized the battery cells. The Argonne group, together with colleagues at UIC and California State University, carried out the computational analyses.
More about lithiumair battery, lithiumoxygen battery, electrochemical reactions, Batteries, Science
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