True lithium-air battery produced

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A lithium-air battery that works in a natural-air environment, while still being able to function after a record-breaking 750 charge/discharge cycles has been designed by a team from the University of Illinois at Chicago and at Argonne National Laboratory.

The batteries would work by combining 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.

Experimental designs of lithium-air batteries have previously been unable to operate in a true natural-air environment due to the oxidation of the lithium anode and production of undesirable byproducts on the cathode that result from lithium ions combining with carbon dioxide and water vapor in the air. These byproducts gum up the cathode, which eventually becomes completely coated and unable to function. These experimental batteries have relied on tanks of pure oxygen, which limit their practicality and pose safety risks.

The research team said it overcame this by using anode, cathode and electrolyte to prevent anode oxidation and buildup of battery-killing byproducts on the cathode.

It coated the lithium anode with a thin layer of lithium carbonate that selectively allows lithium ions from the anode to enter the electrolyte, while preventing unwanted compounds from reaching the anode.

In a lithium-air battery, the cathode is where the air enters the battery. In experimental designs of lithium-air batteries, oxygen, and the other gases that make up air, enters the electrolyte through a carbon-based spongy lattice structure.

The researchers coated the lattice structure with a molybdenum disulfate catalyst and used a hybrid electrolyte made of ionic liquid and dimethyl sulfoxide to facilitate lithium-oxygen reactions, minimise lithium reactions with other elements in the air and boost battery efficiency.