Electron microscopy of the cathode. Source: Nature/University of Illinois at Chicago/Argonne National Laboratory
The University of Illinois at Chicago and Argonne National Laboratory researchers have designed a new lithium-air battery. This new battery works in a natural-air environment and has been proven to work after 750 charge/discharge cycles, breaking the previous record.
"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. "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."
Researchers believe that lithium-air batteries can hold up to five times more energy than the traditional lithium-ion batteries that are currently in our everyday electronics. The lithium-air battery has interested researchers for years, but there have been a few issues in the way of their further development.
Potentially, these batteries would work by combining lithium in the anode with oxygen from the air in order to produce lithium peroxide on the cathode in the battery’s discharge phase. Lithium peroxide would be broken down into its basic lithium and oxygen components during the charge phase of batteries.
Previously experimental designs of these batteries have failed to operate in a true natural-air environment outside of a lab. This is because a lithium anode oxygenates when exposed to the air and the cathode from lithium ions combining with water vapor and carbon dioxide creates unwanted byproducts. The byproducts gum up the cathode and make the battery unable to function. Lithium-air batteries have only been able to operate when they have tanks of pure oxygen attached.
"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.
The researchers managed to overcome these issues by creating a perfect combination of anode, cathode and electrolyte that prevents anode oxidation and buildup of those pesky byproducts. Their developments allowed the battery to operate in a natural environment outside of the lab without an oxygen tank.
The team coated the lithium anode with a layer of lithium carbonate. This selectively allowed the lithium ions from the anode to enter the electrolyte and prevented unwanted compounds from affecting the anode.
The new design has the cathode right where the air enters the battery. In the experimental batteries with this development, oxygen and all of the other gases in the air enter the electrolyte through a lattice structure made out of carbon, which itself is coated with molybdenum disulfate catalyst. They also used a unique hybrid electrolyte that is made of ionic liquid and dimethyl sulfoxide. This combination helped calm the lithium-oxygen reactions with the air and boost battery efficiency.
"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.
The paper on this research was published in Nature.
