Scientists have developed a lithium-air battery that can function in a natural-air environment and continues to work after 750 charge and discharge cycles.

The team, from the University of Illinois at Chicago and the Argonne National Laboratory, published its findings in ‘A lithium-oxygen battery with a long cycle life in an air-like atmosphere’ in the journal Nature. Lithium-air batteries are considered to be able to store up to five times more energy than lithium-ion batteries that are currently used to power electric vehicles.

“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 commercialise it.”

The batteries combine lithium with oxygen from the air to produce lithium peroxide during the discharge phase, which is then broken back down into its lithium and oxygen components during the charge phase. The formation of lithium peroxide generates electric energy.

However, lithium-air batteries have proven difficult to produce. When lithium peroxide is produced, deposits can be left behind on the battery’s cathode, the negatively-charged electrode that is responsible for providing negatively-charged electrons to the system. These deposits can ‘gum up’ the cathode, rendering it useless and meaning the battery ceases to function. One solution, to supply oxygen to the battery from external tanks of pure oxygen, has left the batteries impractical, and posing a significant risk to safety due to the flammability of oxygen.

“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 of the study and Argonne distinguished fellow.

The researchers coated the battery’s lithium anode with lithium carbonate which allows lithium ions to enter the electrolyte while blocking unwanted compounds from reaching the anode. They also coated the entire structure with a molybdenum disulphate catalyst and used a hybrid electrolyte of ionic liquid and dimethyl sulphoxide to encourage lithium-oxygen reactions while minimising reactions between lithium and other elements in the air.

Producing cheap and effective batteries is a key obstacle to the growth of the electric vehicle industry; a replacement battery pack for a Chevrolet Bolt costs more than $15,700, over 40% of the entire vehicle.

“This demonstration of a lithium–oxygen battery with a long cycle life in an air-like atmosphere is an important step towards the development of this field beyond lithium-ion technology, with a possibility to obtain much higher specific energy densities than for conventional lithium-ion batteries,” said the researchers.