Published on March 20th, 2011 | by Tina Casey0
Ordinary Pencil Offers Solution for Elusive Lithium-Air Battery
March 20th, 2011 by Tina Casey
As their name suggests, lithium-air batteries are much lighter than their lithium-ion counterparts, giving them vast potential for use in electric vehicles and portable devices. There’s a big catch, though. Commercial development of rechargeable lithium-air batteries has stalled partly over the presence of moisture in air, which reacts violently with lithium. Now a team of scientists from the National Institute of Advanced Industrial Science and Technology in Japan has come up with a solution, in which an ordinary graphite pencil plays a key role.
Pencils and Lithium-Air Batteries
As described by Harriet Brewerton of the Royal Chemistry Society, the team layered an organic electrolyte around the lithium, then capped it with a ceramic seal that keeps moisture out while doubling as a solid-state electrolyte. A two-dimensional cathode can then be drawn on the ceramic with a graphite pencil. The desired reaction occurs when lithium ions in the electrolyte solution pass through the ceramic. They combine with oxygen in the air, within the area covered by graphite from the pencil. The cathode can be removed and redrawn multiple times.
More Hurdles for Lithium-Air Batteries
In addition to the moisture problem, lithium-air technology still has to overcome efficiency and longevity problems. Last year, researchers at MIT took a big step toward resolving one issue by developing a new high efficiency catalyst for a lithium-air battery, made of a gold-silver alloy. According to writer Kevin Bullis, the magic number is 85 to 90 percent efficiency for commercial batteries. The MIT team improved on the previous high of 70 percent, reaching 77 percent. There’s still a long way to go, but a good two years ago IBM began looking into lithium-air technology for stationary grid use as well as in electric vehicles, which is one indicator that technical obstacles to a commercial grade lithium air-battery can be overcome sooner rather than later.
Image: Pencils by fde comite on flickr.com.