How Better Battery Lifespans and Reused Batteries Can Push the US Power Grid Into the Future
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As artificial intelligence and data centers demand more power from the grid, Carnegie Mellon University is improving a key technology at the heart of America’s energy future — batteries.
Batteries have the ability to store cheap energy from solar farms for use at data centers and function as additional storage on the energy grid to reliably power cars and homes. But making and using the technology domestically has been challenging — batteries have limited lifespans and the U.S. lacks the raw source materials needed to manufacture them on American soil. To address these issues, researchers at CMU are working to extend the lifespan of older batteries, improve the reliability of future batteries, and recover battery materials.
Repurposing batteries that already exist
One of the fastest ways to expand the country’s fleet of battery storage systems is to reuse what already exists in new ways. What does that mean on a practical level? Basically, when a battery can no longer power an electric vehicle, researchers in CMU’s Department of Engineering & Public Policy(opens in new window) (EPP) have found that that same battery can be effectively reused as stable, long-term stationary energy storage.
“We are just beginning to see the first EVs (electric vehicles) that were on the road in the U.S. start to reach their end-of-life,” said Anna Cobb, an EPP Ph.D. student who has been researching second-life battery usage. “And there's this question of what are we going to do with all these batteries? And what are the market forces going to incentivize people to do?”
Cobb and a team of researchers, including her adviser Jeremy Michalek(opens in new window), looked at the three most common types of batteries used in electric vehicles. They wanted to assess whether it made more sense to recycle them for critical minerals or keep them intact and reuse them in other capacities.
“We were thinking from the perspective of somebody who possesses a bunch of end-of-life batteries. Maybe that's an automotive scrapyard, or some sort of dismantler, or somebody who purchases vehicles from insurance auctions and they're trying to figure out what to do with those batteries. We wanted to know: How much money is a repurposer going to pay for that battery? And then, what state of health is the battery, and what second-use application might it be used for?”
Cobb and her team found that it’s more cost-effective to recycle nickel cobalt aluminum (NCA) batteries — which Tesla uses in its longer-range cars — because nickel and cobalt are expensive critical minerals.
“NCA batteries are valuable, so they’re a good candidate for recycling,” said Michalek, a mechanical engineering and EEP professor and founding co-director of the Vehicle Electrification Group(opens in new window). “You can recycle, and pay for the process of recycling by selling those recovered materials. But NCA batteries are not a good candidate for second use because they degrade really fast, so they just don't have a lot of life left for second use.”
The research results for another longer-range battery — nickel manganese and cobalt (NMC) — were not as cut and dry. They found that the cost-effectiveness of repurposing NMC batteries is highly dependent on the battery’s state of health and intensity of how it could be reused.
However, lithium iron phosphate (LFP) batteries, which are more commonly used in standard range EVs, have strong potential for reuse in stationary storage.
“LFP batteries are cheaper, and they just last forever,” Michalek said. “We've done studies subjecting them to extensive fast charging, and no matter what we do to them, they just keep ticking. They're like the Energizer Bunny.”
To reach these conclusions, the researchers simulated how often batteries are typically charged and used across their first (vehicle) and second (stationary storage) lives to try to understand how quickly the different kinds of batteries will degrade. Their findings suggest that an LFP battery that’s already been used in a car for 14 years could have at least 16 more years of use as storage. Those units could help expand battery capacity without importing new batteries from other countries.
Recovering renewable energy materials from industrial waste
Anactisis(opens in new window), a CMU-spinoff company, takes industrial waste, such as coal fly ash, and transforms it into new sources of critical minerals for commercial and defense applications.
The problem:
“By 2028, data centers could consume(opens in new window) about 12% of all electricity in the U.S., so we need to increase our country’s energy production and capacity,” said Thanos Karamalidis, the co-founder and current CEO of Anactisis, and former CMU professor. “We are heavily dependent on imported raw materials that are essential for semiconductors, batteries, solar panels and even electricity distribution lines. So we have to find alternative solutions to reduce our reliance on foreign materials.”
The fix:
Picture a big, sophisticated water filter, but for industrial waste. This waste is rich in other materials because traditional mining is very inefficient and at least 40% of valuable minerals are lost in the process. Anactisis’ filter systems — which only take up about 1,400 square feet — can be stacked next to industrial processing facilities like Lego bricks. Each filter unit can extract different minerals that can help shore up renewable energy production in the U.S.
“All our systems are modular, environmentally friendly, cheaper, faster, with less carbon emissions, so the carbon footprint is much smaller,” Karamalidis said.
Anactisis can take waste like coal fly ash — a powdery byproduct of burning coal — and run it through the filter to extract germanium, an important element used in products like semiconductors, microchips and solar cells. Karamalidis believes Anactisis can cover nearly 100% of domestic demand for germanium using their technology.
These filter units could also process wastes from titanium dioxide production, which is used to make paint pigments, and extract scandium and vanadium — elements that could be used in future batteries for grid energy storage.
“Our systems can be deployed immediately, contrary to conventional mining that takes decades to open and a lot of capital, to sites across the U.S., and start injecting our domestic supply chain with critical minerals,” Karamalidis said.
Work That Matters
Researchers at CMU are working on real world solutions to the biggest challenges.
Read more about the latest discoveries.(opens in new window)
An LFP battery that’s already been used in a car for 14 years could have at least 16 more years of use as storage. Those units could help expand battery capacity without importing new batteries from other countries.
“These reused batteries could be used to store energy captured from solar fields or as frequency regulation for the grid,” Cobb said. “When the supply and demand for power on the grid gets out of balance, it’s useful to have battery storage that you can just tap into to assist with meeting demand.”
There’s a strong business and political argument to be made for reusing batteries.
“If we can reuse, recycle and repurpose, this inherently creates a domestic source for these items, and then we are less reliant on overseas suppliers,” said Alan Scheller-Wolf(opens in new window), a professor at the Tepper School of Business who studies renewable energy supply chains. “Given global politics, that’s a legitimate concern.”
Scheller-Wolf said that while this doesn’t exist in the U.S. right now, circular supply chains(opens in new window) can enhance energy efficiency, economic stability and industrial growth.
“It would make things less expensive at the front because you would be reducing the cost of the materials,” he said. “And you'd be reducing the decommissioning cost, because instead of land filling it and having to pay some amount, you'd actually be able to harvest value. And so there is value trapped there, but we haven't figured out how to get it out yet economically.”
A cheap solution to extend battery life
Reusing batteries alone won’t stabilize or expand the country’s renewable energy grid. The U.S. also doesn’t have most of the critical minerals — such as cobalt, nickel and lithium — needed to make new batteries. Developing longer-lasting batteries could reduce how often the U.S. must import them from China.
That’s where Reeja Jayan(opens in new window)’s work comes into play.
“When a battery is dead, it's not dead,” said Jayan, a professor in the departments of Mechanical Engineering, Electrical and Computer Engineering, and Materials Science & Engineering. “The minerals are intact, it’s just that you often don't have the ability to get the current out of them. So having technology like ours helps us extend its life.”
Jayan has developed an ultra-thin plastic coating that could make batteries last ten times as long as a normal battery.
To understand how this works, Jayan said to imagine a battery’s structure as a sandwich. The two slices of bread are called electrodes — one end is positive and the other end is negative. The sandwich filling in between the bread is the electrolyte, through which the (Lithium) ions shuttle back and forth between the electrodes. But over time, the activity of those ions degrades the electrodes, obstructing the flow of charges and eventually the battery dies.
“When a battery is dead, it's not dead.” — Reeja Jayan
The polymer coating Jayan created can slow that degradation. Using the sandwich analogy — it stabilizes the two pieces of bread and keeps the ions bouncing around inside the sandwich filling for longer.
The plastic coating is 10,000 times thinner than a strand of hair. Using special machines created by Jayan’s lab, the coating can be precisely applied to different parts of a battery, like the electrodes or even the mineral particles inside the electrodes.
“Polymers — or plastics — are flexible, and they can shrink wrap material like Saran wrap,” she said. “But unlike Saran wrap, these plastics are conducting electricity. That was the key. If you Saran wrap the battery, you can keep the electrode particles morphologically and electrically intact and that enhances life, so the batteries last longer.”
This technology is also relatively cheap. Jayan estimates that the plastic coating when scaled up would only be 1%-3% of the total cost of a battery cell.
Improving batteries at the molecular level is the focus of Jayan’s company SeaLion Energy(opens in new window), which has received funding(opens in new window) from the U.S. Department of Energy Advanced Research Projects Agency-Energy (ARPA-E). Jayan hopes the technology can contribute to sustainable energy independence in the U.S.
“In the future, we don’t have to throw away battery cells,” she said. “There’s bipartisan support to make these energy storage systems right now in the U.S., and keeping batteries in circulation for longer periods of time can help lower energy costs. It can also lower the effect of the greenhouse gas emissions that naturally come from manufacturing anything, especially something like a battery.”
That promise makes good economic sense and could help meet growing energy demands, said Akshaya Jha(opens in new window), associate professor in economics and public policy at the Heinz College of Information Systems and Public Policy.
“If you can extend the life of a battery, it makes it more profitable to invest in a battery,” Jha said. “This is kind of exciting from the perspective of incentivizing investment in batteries.”
Jha believes that having more access to battery storage will be key to expanding and stabilizing the U.S. power grid, especially as solar power continues to grow at a record pace.
“As we get higher percentages of electricity generation coming from wind and solar technologies, we're going to need to increasingly confront the fact that wind and solar technologies only produce when nature permits — when the wind is blowing or the sun is out,” Jha said. “That's where batteries can have an outsized impact. Solar only produces during the day and doesn't produce in the evening. So when there's a lot of sun, the battery can charge and then release power when there’s demand in the evening and it’s dark outside.”
He said the same idea is true for data centers co-located with both solar farms and battery storage.
“A battery co-located with a solar farm means that, to some extent, the data center is going to use that solar during the day, and whatever excess energy is left over, can be stored in the battery. Then the battery can discharge in the evening and the data center can use the on site electricity coming from the battery.”
As solar continues to grow faster than ever(opens in new window), it will be incumbent on America to turn to the best batteries and energy supply chains possible.
