Scientists at Argonne National Laboratory helped kick off the modern energy storage race with their diligent experimentation on lithium-ion batteries.
Their patents have ended up in the technology that powers the Chevy Volt and contributed to stationary storage for buildings and the grid. Today's batteries, though, have not reached their full potential for power density, duration or cycle life.
So, tucked away among mid-century brick buildings on a windswept prairie and oak landscape southwest of Chicago, researchers for the Department of Energy are chugging away on optimizing the current battery chemistries and inventing new ones.
The labs handle everything from theoretical work to small-scale cell prototyping, larger batch production and automated assembly-line fabrication. This proves not only that the chemistry works, but also that it still works after scaling up to commercial volume and streamlining the manufacturing process.
On a recent visit to the lab, GTM identified ongoing research efforts of particular interest to our readers. Keep an eye on these ones.
Store for a month
These days, when you hear someone selling a “long-duration” battery, it usually means six or eight hours. That can go a long way toward making intermittent renewable generation dispatchable for peak hours.
Day-to-night solar shifting doesn't do much good in the midst of a prolonged rainy season, though. If communities with significant seasonal variation want to rely heavily on renewable generation, they're probably going to need some sort of seasonal storage. Pumped hydro can't carry it all.
Scientists with the Joint Center for Energy Storage Research, a research consortium led by Argonne, may eventually be able to fix that.
They are refining test cells for a seasonal storage battery that will be economical at a duration of one month or more, said Venkat Srinivasan, deputy director for research and development at JCESR.
MIT professor Yet-Ming Chiang had investigated the potential for a battery made with two especially cheap and abundant components: sulfur and air. JCESR scientists built on that idea and developed an aqueous oxygen sulfur flow battery cell. Since the materials are cheap and the energy capacity can scale independently from the power capacity, this battery has the potential to lead in cost reduction for super-long duration.
“At its ultimate limit, like an internal combustion engine, if you had a huge tank full of gasoline and a tiny 4-cylinder engine, all-in, the cost is only the cost of gasoline in the tank,” Srinivasan said. In the case of the flow system at super-long duration, “the chemical cost becomes the most important, and sulfur and oxygen are so cheap that you get to be really, really cheap [overall].”
There are still some kinks to be worked out, like finding a cheaper membrane. And optimizing any one part of a battery tends to throw something else out of whack, necessitating additional effort to balance out the system. JCESR has 10 more months left for this program to figure out these issues.
Assuming that effort succeeds, the scientists have already laid the groundwork for the move to commercialization.
“The size we've picked [for the test cell] is the size that our industry partners have told us, ‘If you can do something there and it looks promising, we think we can take it from there,” Srinivasan said.
If the test cell continues to improve, and industry steps in to carry it forward, how long will it take before we see seasonal batteries at work?
Based on Argonne’s recent experience with advanced battery commercialization, the range lies between a slow scenario of 15 to 20 years and a best case of about five, Srinivasan said.
Even under the slow scenario, that’s enough time to help Hawaii with its goal of a 100 percent renewable grid by 2045, or lend a hand to California, which is considering that goal for itself.
Seasonal storage would reduce the additional capacity such grids would need to meet peak load when seasonal weather limits solar and wind generation. That, in turn, lessens the over-generation burden from that extra capacity when the sun comes back out, reducing the system costs of the transition to high rates of renewables.
Fast charge using the power of light
Range anxiety diminishes with every new electric-vehicle model released. As long as you don’t commute 300 miles a day, currently available EV batteries have you covered — if you can afford them.
Charge time, though, still deters some customers, and for good reason. If you’re used to filling up a tank in a few minutes, the idea of pausing your road trip to charge for a few hours, or even 45 minutes, puts a damper on electric driving excitement.
Much of the development on this problem has focused on the charger itself. Tesla’s market-leading Supercharger, for instance, has tried liquid-cooling the cable to push a higher electrical current. At a certain point, charging with a strong enough current warms up the battery, potentially degrading long-term cycle life.
Christopher Johnson, a chemist at Argonne, decided to approach this challenge from the battery side. He noticed that certain battery materials have photoreactive properties similar to semiconductors: By exciting the molecules with a beam of concentrated light, you can reduce their electrical resistance and cajole them into accepting a faster current without heating up.
From that impulse, he created a photo-assisted fast charge technique that he says cuts the time to charge in half for the same current.
“We've tested it, we've verified it, we're getting ready for publication,” Johnson said in an interview. “Our hope is that not only can it go faster, but hopefully the battery lifetime will be extended as a result of this way to charge” compared to current charging techniques.
If this process checks out and scales properly, it could change the look and feel of charging stations.
“At the gas station, you would have a light station,” Johnson said. “You would pull in and clamp the lamp onto your battery as well as the current. You flip the lamp on and then you trickle the charge into the battery.”
This would affect car design too, because you would need a way of getting the light beam to the battery, perhaps through a fiber optic cable with a port on the exterior.
The range of battery materials Johnson examined was constrained by what is actually used in EV batteries. One chemistry in use, the lithium-manganese-oxide spinelle, exhibits the necessary semiconducting properties, so the photo-assisted technique could be integrated into existing manufacturing processes.
Johnson has been working at Argonne's Center for Electrochemical Energy Storage, funded by the Department of Energy's Basic Energy Sciences program. Once he publishes the initial findings, Johnson wants to move from the applied science he's been doing to a more fundamental science approach, to better understand why the process works.
It's too early to know if light-assisted charging will become commonplace, but it provides a few valuable insights. For one thing, it's important to remember that it takes two to charge: It makes sense to attack the problem from both the charger end and the battery end.
Additionally, since battery functions are so closely interconnected in the cell structure, advances in the speed of charging need to come with commensurate protections for the health of the battery. Trading speed of charging for battery lifetime is a costly gamble. If Johnson can achieve both simultaneously, the consumer discomfort of using a second charging apparatus would be a small price to pay.
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