Credit: Peter Bruce

Credit: Peter Bruce

Using something of the same concept behind zinc-air batteries, a group of scientists in the UK have attained a proof-of-concept version of a lithium-air battery that they say could significantly increase a batteries energy capacity or decrease its bulkiness

A story in New Scientist quotes St. Andrews University researcher Peter Bruce as saying, “The major barrier to increasing the energy density of these batteries is the positive electrode,” he says. “Everyone wants to find a way to push up the amount of lithium stored there, which would raise the capacity.”

Bruce’s lithium-air battery has a positive electrode composed of porous (and therefore low weight) carbon and a lithium salt electrolyte solution. The electrolyte can easily soak into the porous carbon electrode. As the battery discharges, a membrane allows oxygen into the battery. The lithium reacts with the oxygen to form lithium oxide in the openings in the electrode. Under recharging conditions, the lithium oxide reverts to lithium ions and oxygen.

“By using oxygen from the environment instead you save weight and volume because you don’t have to carry the reagents around inside the battery – you just need the carbon scaffold,” Bruce told New Scientist.

Bruce says a prototype (400 milliamp hours per gram)  has already beaten the capacity-to-weight ratios of small conventional lithium batteries by a factor of eight, and says a 10-fold improvement is still attainable.