Published on August 21st, 2017 | by Tina Casey0
Toyota (Still) Banks On Lithium-Air Energy Storage For Next-Gen EV Batteries
August 21st, 2017 by Tina Casey
Lithium-air batteries may or may not ever happen, but it’s not for lack of trying. Toyota Motor Europe is one of the funders behind a new MIT study that dives into the mysteries of this elusive energy storage technology, which promises to triple the power per weight of conventional lithium-ion batteries.
Lithium-air technology translates into lighter, cheaper EV batteries and better range — if anybody can ever figure out how to get them to work in an EV.
EVs And The Lithium-Air Energy Storage Unicorn
Lithium-air batteries literally replace some of the lithium with an air flow, which is why they save on weight.
Back in 2010 the US Energy Department laid out the challenge facing EVs in the auto market…
An EV that is cost-competitive with gasoline would require a battery with twice the energy storage of today’s state-of-the-art Li-Ion battery at 30% of the cost.
…and tagged Li-air energy storage technology as one promising solution:
Li-Air batteries are better than the Li-Ion batteries used in most EVs today because they breathe in air from the atmosphere for use as an active material in the battery, which greatly decreases its weight. Li-Air batteries also store nearly 700% as much energy as traditional Li-Ion batteries. A lighter battery would improve the range of EVs dramatically.
So, how are we doing? After all, it’s been seven years since the Energy Department wrote up its wish list.
The problem, as summed up by MIT writer David Chandler, is a triple whammy:
But that theoretical promise has been limited in practice because of three issues: the need for high voltages for charging, a low efficiency with regard to getting back the amount of energy put in, and low cycle lifetimes, which result from instability in the battery’s oxygen electrode.
CleanTechnica has been periodically checking on the progress of Li-air energy storage since 2010, and researchers have been trying all sorts of things to resolve any or all of those three issues, from genetically modified viruses to ordinary pencils. Researchers at MIT have also been looking into glass-based Li-air batteries.
The last time we took a look was back in 2016, when, researchers at Argonne National Laboratory had some luck with a graphene-based version. The researchers found that graphene acts as a stabilizer, but is just the first step in a longer journey:
We anticipate that this discovery will lead to methods of synthesizing and stabilizing LiO2, which could open the way to high-energy-density batteries based on LiO2 as well as to other possible uses of this compound, such as oxygen storage.
Ups And Downs For Li-Air Energy Storage
Toyota crossed the CleanTechnica energy storage radar back in 2013, when it entered into an energy storage collaboration with BMW and predicted that solid state and Li-air batteries would happen by 2020.
That same year Reuters reported that IBM was working on a Li-air battery with a EV range of 500 miles on a single charge.
If that rings a bell, you may be recalling IBM’s “Battery500” project for Li-air energy storage technology, which kicked off all the way back in 2009.
Toyota Keeps The Faith
Where were we? Oh right, the new Toyota-funded battery research at MIT. Russia’s Skoltech Center for Electrochemical Energy Storage and the National Science Foundation also chipped in.
As MIT puts it, the over-arching problem is that the body of Li-air research amounts to “conflicting and confusing results, as well as controversies over how to explain them,” as MIT puts it.
The MIT team decided to zero in on lithium iodide, one of the more promising materials to emerge from the stew of confusion:
The compound was seen as a possible solution to some of the lithium-air battery’s problems, including an inability to sustain many charging-discharging cycles, but conflicting findings had raised questions about the material’s usefulness for this task.
According to MIT, some of the previous research indicates that lithium iodide improves performance, while other studies show that it sparks “irreversible reactions and poor battery cycling.”
So, first the bad news: the team concluded that lithium iodide is most likely not so promising after all.
And now, the good news: by drilling down into the nanoscale architecture of the reaction, the team discovered precisely why lithium iodide has a problem:
[It] can enhance water’s reactivity and make it lose protons more easily, which promotes the formation of LiOH in these batteries and interferes with the charging process.
Did you get all that? In other words, the MIT team nailed down the mechanism that produces “unwanted” reactions on the surface of the electrode.
The next step is to work out from there and investigate alternative materials that mitigate or even eliminate those reactions.
Toyota may have been somewhat optimistic about that 2020 energy storage goal, but as the saying goes if you aim for the sky you’ll land on the roof.
Image: “This series of photographs shows the chemical reaction that occurs during the charging of a lithium oxygen battery using lithium iodide as an additive” by Jose-Luis Olivares/MIT.
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