Energy storage technology is a hot item these days, and the latest news from the Massachusetts Institute of Technology just made things a little hotter. A bi-national research team based at the school has just figured out how to solve some key issues with cutting edge lithium-air technology that makes it even cutting-edgier.
The new finding has huge implications for the electric vehicle marketplace. That’s mainly because it could result in a significantly lighter battery, which translates into greater battery range. As for cost, that’s a whole ‘nother can of worms — or is it?
What’s Wrong With Li-Ion Energy Storage
For those of you new to the topic, lithium-air energy storage has already been around the block a few times. Back in 2010, the Energy Department’s cutting edge funding division, ARPA-E, provided a short list of the reasons why lithium-air batteries and EVs go together like bread and butter. The agency also foretold the demise of the current gold standard for EV energy storage, lithium-ion (Li-Ion):
That’s a pretty big if. It’s been six years, EV sales are skyrocketing, and lithium-ion is still king of the road.
That’s partly due to some sticky issues with lithium-air technology, as described by the MIT team:
They waste much of the injected energy as heat and degrade relatively quickly. They also require expensive extra components to pump oxygen gas in and out, in an open-cell configuration that is very different from conventional sealed batteries.
The MIT team also notes that lithium-air batteries tend to be expensive and complex, because water and carbon dioxide have to be removed from the air before the battery can make use of the oxygen.
Another problem is the change in volume that occurs during charging cycles, which can severely crimp the lifespan of the battery.
The MIT “Glass Battery” Solution
Working with researchers from Argonne National Laboratory and Peking University, the MIT team is on the trail of a solution for all of these problems, all at once.
The new “glass battery” is still in the concept stage, so don’t hold your breath for the production model, but their results were promising enough to merit publication in the journal Nature Energy, where you can find it under the title, “Anion-redox nanolithia cathodes for Li-ion batteries.”
The team zeroed in on the imbalance between the relatively high voltage that lithium-air batteries put out, compared to their charging voltage. That imbalance translates into a significant amount of heat generation when the battery is charged (that’s the problem ARPA-E refers to above).
Charge too quickly and you could fry the whole battery to a crisp, according to the MIT team.
The solution was to prevent oxygen from reverting to a gaseous state. In a typical lithium-air configuration, atmospheric oxygen is sucked into the battery, where it reacts with the lithium to generate an electrical current before being booted back out into the atmosphere.
In contrast, the MIT battery does not need atmospheric oxygen. It’s a sealed device, like a traditional battery, which contains oxygen trapped in three solid lithium-oxygen compounds (Li2O, Li2O2, and LiO2 for those of you keeping score at home), all stabilized within a spongy cobalt oxide matrix, in the form of a glass.
The MIT calls the compounds “nanolithia” because they consist of nanoscale particles of lithium and oxygen.
Et voilà — there’s your glass battery.
Advantages of Lithium-Oxygen Energy Storage
The new approach cut down the voltage differential to a manageable level, which means that the battery could be subjected to a higher rate of charging without overheating.
Aside from being far lighter than a typical lithium-air battery, the new battery is also practically immune to overcharging.
Here’s a couple of snippets from the test results:
“…we have overcharged the battery for 15 days, to a hundred times its capacity, but there was no damage at all.”
…a lab version of the new battery was put through 120 charging-discharging cycles, and showed less than a 2 percent loss of capacity, indicating that such batteries could have a long useful lifetime.
To ice the cake, the sealed design of the battery is consistent with conventional lithium-ion technology, so it could be adapted to conventional energy storage and EV design with relatively little adjustment.
The team is already looking at double the energy (relative to the weight of the cathode) compared to conventional lithium-ion, and it expects to double that again as the design is refined.
As for cost, check this rundown from researcher Ju Li, who is the Battelle Energy Alliance Professor of Nuclear Science and Engineering at MIT:
…The carbonate they use as the liquid electrolyte in this battery “is the cheapest kind” of electrolyte, he says. And the cobalt oxide component weighs less than 50 percent of the nanolithia component. Overall, the new battery system is “very scalable, cheap, and much safer” than lithium-air batteries, Li says.
Game on! The next step involves getting out of the proof-of-concept stage and into the prototype phase. That should take about a year so stay tuned.
Image: Courtesy of the researchers via MIT.