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Image: Lithium-air battery cutaway
Researchers say lithium-air battery technology could boost the range of electric cars by a factor of five. (Credit: IBM via YouTube)

A decade from now, we could all be driving low-cost electric cars for hundreds of miles without recharging, thanks to an advance in lithium-air battery technology announced today. Or maybe it’ll be some other lithium-air innovation. Or maybe we’ll see batteries with a different chemistry, such as sodium-air or sodium-lithium.

“The battery of the future is going to encompass a lot of these different technologies,” University of Cambridge chemist Clare Grey told GeekWire.

Grey is the senior author of a study describing a technological twist that promises to remove some of the obstacles that have blocked the path to battery nirvana. The research, featured on the cover of this week’s issue of the journal Science, shows how changing the nanostructure of the electrodes and shifting the chemistry can boost a lithium-oxygen battery’s efficiency and make it more stable.

Science cover
The journal Science’s cover illustration features a false-color microscopic view of a reduced graphene oxide electrode (black, center), which hosts the lithium hydroxide particles (pink) that form when a lithium-oxygen battery discharges. (Illustration by Valerie Altounian for Science/AAAS)

“We haven’t solved all the problems inherent to this chemistry, but our results do show routes forward towards a practical device,” Grey said in a news release.

If the problems can be solved, lithium-oxygen batteries would outperform today’s lithium-ion batteries, largely because they could take advantage of oxygen from the air rather than having to store an oxidizer internally.

Such batteries might be put to use initially for small-scale applications – for instance, in hearing aids or in smartphones that could go for days without a recharge. But the big payoff would come in the form of grid-scale storage batteries that could make the electricity generated by solar and wind power available 24/7, and electric cars that could theoretically go five times farther than they can today.

“If we could even manage a factor of two or three, those are substantial numbers for the transport industry,” Grey said.

In the Science paper, Grey and her colleagues explain how they built highly porous electrodes from atom-thick sheets of graphene and added a cocktail that included lithium iodide and water. The battery’s chemistry creates crystals of lithium hydroxide rather than the usual lithium peroxide. The result? Energy efficiency rose from 70 percent, which is the typical level for lithium-oxygen batteries, to 93 percent. Also, the battery could be recharged more than 2,000 times without breaking down.

If that kind of performance can be carried over into a commercial battery, lithium-air batteries would work as well as lithium-ion batteries and provide significantly greater storage capacity. “We are actually in there with a chance which wasn’t seen before,” Grey said.

One of the weird things about the battery is that the researchers don’t fully understand the mechanism behind the chemical reaction. Grey said the lithium iodide may have a “passivating” effect that reduces corrosion. “This is something we continue to work with,” she said.

Lithium-oxygen reaction
This schematic shows the formation of lithium hydroxide (LiOH) on the graphene electrode when discharging a non-aqueous lithium-oxygen battery in the presence of the redox mediator, lithium iodide, and trace water. When charging, the iodide is oxidized to iodine, which helps to remove the LiOH and reform the bare graphene electrode. (Credit: T. Liu, G. Bocchetti and C. Grey)

Grey said the technology has been patented by Cambridge Enterprise, her university’s commercialization arm – but she stressed that a number of challenges, including battery safety, still had to be overcome. “We are working with a number of companies to see if we can address some of the practical issues,” she said.

The Cambridge experiment is by no means the only potential route toward better batteries. Battery chemistry is a hot topic in innovation right now – even as lithium-ion batteries are taking off, thanks to Tesla and other electric ventures.

Just today, researchers at Berkeley Lab laid out new information about the workings of lithium-rich and manganese-rich transition metal oxides, which they called a “potentially game-changing battery material.” Other research teams have been looking into the opportunities afforded by silicon-basedsulfur-based, lithium-sulfuraluminum-air and sodium-air batteries.

“It might be that sodium is going to be sitting in a cheap application,” Grey said. “And it may well be that the lithium-air or the lithium-sulfur is sitting in an application where you need energy density, but you don’t need such high rate. So that’s my future. My future is diverse, with different battery technologies.”

Cambridge’s Tao Liu is the principal author of the Science paper, “Cycling Li-O2 Batteries Via LiOH Formation and Decomposition.” In addition to Liu and Grey, the authors include Michal Leskes, Wanjing Yu, Amy Moore, Lina Zhou, Paul Bayley and Gunwoo Kim.

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