Lithium-air battery has higher energy density than Li-ion

Researchers are reporting new progress on a so-called breathing battery that has the potential to one day replace the lithium-ion technology in electric vehicles.

The team, from Mie University in Japan, presented their work at the 247th National Meeting & Exposition of the American Chemical Society (ACS).

‘Lithium-air batteries are lightweight and deliver a large amount of electric energy,’ said Nobuyuki Imanishi, a Ph.D student at Mie University. ‘Many people expect them to one day be used in electric vehicles.’

The main difference between lithium-ion and lithium-air batteries is that the latter replaces the traditional cathode with air, making the rechargeable metal-air battery lighter and potentially more powerful than its commercial counterpart.

One of the main components researchers are working on is the lithium-air batteries’ electrolytes, of which there are currently four electrolyte designs, with one involving 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, however, is that water in direct contact with lithium can damage it.

Seeing the potential of the aqueous version of the lithium-air battery, Imanishi’s team tackled this issue. Adding a protective material to the lithium metal is one approach, 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.

‘Our system’s practical energy density is more than 300 Wh/kg,’ Imanishi said in a statement. ‘That’s in contrast to the energy density of a commercial lithium-ion battery, which is far lower, only around 150Wh/kg.’

The battery is said to have 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 also have applications in the home, thanks to their low cost. Power output remains a big hurdle, but Imanishi said his group is committed to honing this approach, as well as exploring other options, until lithium-air becomes a commercial reality.