Sales of electric vehicles (EVs) nearly doubled in 2013, but most won’t take you farther than 100 miles on one charge. To boost their range toward a tantalizing 300 miles or more, researchers are reporting new progress on a “breathing” battery that has the potential to one day replace the lithium-ion technology of today’s EVs. These are known as Lithium-air batteries and are lightweight and deliver a large amount of electric energy. But are they commercially viable?
The main difference between lithium-ion and lithium-air batteries, says Bernstein, is that the latter replaces the traditional cathode — a key battery component involved in the flow of electric current — with air. That makes the rechargeable metal-air battery lighter with the potential to pack in more energy than its commercial counterpart.
“While lithium-air batteries have been touted as an exciting technology to watch, they still have some kinks that need to be worked out,” Bernstein reports.” Researchers are forging ahead on multiple fronts to get the batteries in top form before they debut under the hood.” says Bernstein.
“One of the main components researchers are working on is the batteries’ electrolytes, materials that conduct electricity between the electrodes. There are currently four electrolyte designs, one of which involves water. The advantage of this “aqueous” design over the others is that it protects the lithium from interacting with gases in the atmosphere and enables fast reactions at the air electrode. The downside is that water in direct contact with lithium can damage it.” Bernstein adds.
A team at Mie University in Japan tackled the potential of the aqueous version of the lithium-air battery. They discovered that adding a protective material to the lithium metal protects the lithium, but this typically decreases the battery power. So they developed a layered approach, sandwiching a polymer electrolyte with high conductivity and a solid electrolyte in between the lithium electrode and the watery solution. The result was a unit with the potential to pack almost twice the energy storage capacity, as measured in Watt hours per kilogram (Wh/kg), as a lithium-ion battery.
The battery showed a lot of promise, with high conductivity of lithium ions, and the ability to discharge and recharge 100 times. In addition to powering EVs, lithium-air batteries could one day have applications in the home, thanks to their low cost. Power output remains a big hurdle, but the Mei University team is committed to honing this approach, as well as exploring other options, until lithium-air becomes a commercial reality.