A breathing battery

Most electrical vehicles won’t take you farther than 160 km on one charge. Japanese researchers are working towards increasing the range to 480 km or more with the help of a breathing battery that could one day replace the lithium-ion technology of today’s EVs.

“Lithium-air batteries are lightweight and deliver a large amount of electric energy,” said Nobuyuki Imanishi, PhD, Mie University in Japan. The main difference between lithium-ion and lithium-air batteries 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.

One of the main components researchers are working on is the battery’s electrolytes, materials that conduct electricity between the electrodes There are currently four electrolyte designs, one of which involves water. The advantage of the ‘aqueous’ design 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 if the water is in direct contact with lithium, it can cause damage.

Seeing the potential of the aqueous version of the lithium-air battery, Imanishi’s team tackled this issue. They considered adding a protective material to the lithium metal, 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. “That’s in contrast to the energy density of a commercial lithium-ion battery, which is far lower, only around 150 Wh/kg.”