Tiny filter, big breakthrough: UF team helps lithium–sulfur batteries keep their charge
Longer-lasting phones, lighter drones, electric cars that drive farther. These are just some of the possibilities thanks to a new battery separator design from University of Florida researchers and their partners.
Think of a tiny coffee filter, but this one works inside a battery. The team recently showed that a one-atom-thick filter can block sulfur chains from shuttling within the battery, potentially unlocking the long-awaited promise of lithium–sulfur batteries.
While lithium-sulfur batteries are lighter and pack more power in a lighter package compared to the more conventional lithium-ion batteries, their fatal flaw is the sulfur doesn’t cooperate well inside the system. It clumps into long chains that clog up the works, draining the battery’s power and cutting its lifespan.
Engineers from UF, Purdue University and Vanderbilt University developed a high-performance filter that works at a molecular level to fix the problem.
“It’s like a microscopic coffee filter or a bouncer at a club,” said Piran Kidambi, an associate professor of mechanical and aerospace engineering at UF and author of the study published this month in ACS Applied Materials and Interfaces. “Tiny lithium ions slip through easily, but bulky sulfur chains get blocked.”
Why it matters
Today’s lithium-ion batteries power nearly everything we carry and drive, from smartphones to electric vehicles. They work well, but they’ve hit limits on how much energy they can store for their weight.
“Lithium-ion batteries have been perfected over a long time, and they work very well,” Kidambi said. “But lithium–sulfur can be much lighter and can store more electrical energy.”
An average electrical vehicle battery weighs about 1,000 pounds and gets around 200 to 250 miles of range. With lithium–sulfur at the same weight, a driver can go farther on one charge, Kidambi said. Cellphones would last longer between charges, and lighter batteries would allow drones to stay in the air longer.
A filter at the atomic scale
To make the filter, the researchers used a method called chemical vapor deposition. They start with a copper foil, heat it and flow a vapor over it. The chemical reaction leaves behind a film of graphene with perfectly defined openings to separate the lithium from the sulfur chains.
When they tested the design, the difference was striking. Unfiltered batteries began losing performance quickly. With the one-atom-thick filter, batteries held nearly all their capacity over more than 150 charge-discharge cycles.
“They performed quite well,” Kidambi said. “The others dropped off with each charge and discharge, but the ones with our filter held steady.”
Beyond cars and phones
The potential applications extend well beyond consumer devices. Kidambi pointed to freight trucks, trains and even ships, where battery weight becomes a major obstacle.
“As you move from cars to trucks, trains or ships, the battery weight rises exponentially because you need more energy to move them,” he said. “That’s called weight compounding. The battery starts to weigh almost as much as the load it’s supposed to move.”
A step forward, with more to do
Much work remains before lithium–sulfur batteries with atom-thin filters could be manufactured at scale and placed into everyday devices. But Kidambi is encouraged by their progress.
“There’s real scientific success in being able to show that we can solve a problem, and we can solve it by engineering at the atomic level,” he said. “That is exciting for me.”
Journal
ACS Applied Materials & Interfaces
Article Title
Size-Selective Nanoporous Atomically Thin Graphene Separators for Lithium−Sulfur Batteries
University of Houston researchers drive breakthroughs in building longer-lasting, faster-charging batteries
University of Houston
image:
Yan Yao, professor at Cullen College of Engineering, University of Houston
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Researchers at the University of Houston, a global leader in energy research and innovation, are spearheading a study that could transform the future of battery technology.
Yan Yao, an award-winning professor at UH’s Cullen College of Engineering, along with collaborators from Singapore, Zhejiang University and Seoul National University, have published a review in the journal Science eying alternative metals for battery anodes.
If Yao and his fellow collaborators succeed, it could lead to longer-lasting batteries for electric vehicles, smartphones, laptops and more.
“I think the most exciting part of this is the global interest in this new battery,” Yao said. “But we still have a lot of challenges ahead; there’s still a lot of learning that needs to be done.”
The review highlights the similarities and differences in monovalent metals such as lithium, sodium and potassium, and multivalent metals, including magnesium, calcium and aluminum.
The impetus for this review is that graphite, the standard anode for lithium-ion batteries, is reaching its practical limits. Lithium metal could be a strong alternative as it offers 10 times the charge storage capacity of graphite, but it tends to form tiny spikes called dendrites that can short-circuit batteries.
Meanwhile, multivalent metals present promising alternatives because they are more abundant, safer and potentially able to store more energy at a lower cost. The downside to these metals is multivalent ions move more slowly, which can slow charging, but are less prone to forming dendrites.
To overcome these barriers, researchers are exploring textured electrode surfaces that guide smooth metal growth and developing new electrolytes that optimize ion movement and protective film formation.
“This work underscores the need for continued research to overcome the technical barriers of multivalent metal batteries,” Yao said. “Advances in electrode design, electrolyte chemistry, and battery architecture are crucial to harness the full potential of these materials.”
The study also identifies emerging design principles, such as using locally high salt concentrations and weakly solvating electrolytes for monovalent systems, and strongly solvating, weakly ion-pairing electrolytes for multivalent systems, offering a roadmap for next-generation electrolyte development.
Other contributors include Yuanjian Li, Sonal Kumar, Gaoliang Yang and Zhi Wei Seh from the Institute of Materials Research and Engineering (IMRE) in Singapore; Jun Lu from Zhejiang University; and Kisuk Kang from Seoul National University.
With global demand for high-performance, sustainable batteries growing, this research provides critical guidance for scientists and engineers striving to develop the next generation of energy storage technologies.
Journal
Science
Method of Research
Systematic review
Subject of Research
Not applicable
Article Title
The contrast between monovalent and multivalent metal battery anodes
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