energy storage

Houston researchers make headway on developing low-cost sodium-ion batteries

Rice's Atin Pramanik and a team in Pulickel Ajayan's lab shared new findings that offer a sustainable alternative to lithium batteries by enhancing sodium and potassium ion storage. Photo by Jeff Fitlow/Courtesy Rice University

A new study by researchers from Rice University’s Department of Materials Science and NanoEngineering, Baylor University and the Indian Institute of Science Education and Research Thiruvananthapuram has introduced a solution that could help develop more affordable and sustainable sodium-ion batteries.

The findings were recently published in the journal Advanced Functional Materials.

The team worked with tiny cone- and disc-shaped carbon materials from oil and gas industry byproducts with a pure graphitic structure. The forms allow for more efficient energy storage with larger sodium and potassium ions, which is a challenge for anodes in battery research. Sodium and potassium are more widely available and cheaper than lithium.

“For years, we’ve known that sodium and potassium are attractive alternatives to lithium,” Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor of Engineering at Rice, said in a news release. “But the challenge has always been finding carbon-based anode materials that can store these larger ions efficiently.”

Lithium-ion batteries traditionally rely on graphite as an anode material. However, traditional graphite structures cannot efficiently store sodium or potassium energy, since the atoms are too big and interactions become too complex to slide in and out of graphite’s layers. The cone and disc structures “offer curvature and spacing that welcome sodium and potassium ions without the need for chemical doping (the process of intentionally adding small amounts of specific atoms or molecules to change its properties) or other artificial modifications,” according to the study.

“This is one of the first clear demonstrations of sodium-ion intercalation in pure graphitic materials with such stability,” Atin Pramanik, first author of the study and a postdoctoral associate in Ajayan’s lab, said in the release. “It challenges the belief that pure graphite can’t work with sodium.”

In lab tests, the carbon cones and discs stored about 230 milliamp-hours of charge per gram (mAh/g) by using sodium ions. They still held 151 mAh/g even after 2,000 fast charging cycles. They also worked with potassium-ion batteries.

“We believe this discovery opens up a new design space for battery anodes,” Ajayan added in the release. “Instead of changing the chemistry, we’re changing the shape, and that’s proving to be just as interesting.”

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A View From HETI

Houston researchers have uncovered why solid-state batteries break down and what could be done to slow the process. Photo via Getty Images.

A team of researchers from the University of Houston, Rice University and Brown University has uncovered new findings that could extend battery life and potentially change the electric vehicle landscape.

The team, led by Yan Yao, the Hugh Roy and Lillie Cranz Cullen Distinguished Professor of Electrical and Computer Engineering at UH, recently published its findings in the journal Nature Communications.

The work deployed a powerful, high-resolution imaging technique known as operando scanning electron microscopy to better understand why solid-state batteries break down and what could be done to slow the process.

“This research solves a long-standing mystery about why solid-state batteries sometimes fail,” Yao, corresponding author of the study, said in a news release. “This discovery allows solid-state batteries to operate under lower pressure, which can reduce the need for bulky external casing and improve overall safety.”

A solid-state battery replaces liquid electrolytes found in conventional lithium-ion cells with a solid separator, according to Car and Driver. They also boast faster recharging capabilities, better safety and higher energy density.

However, when it comes to EVs, solid-state batteries are not ideal since they require high external stack pressure to stay intact while operating.

Yao’s team learned that tiny empty spaces, or voids, form within the solid-state batteries and merge into a large gap, which causes them to fail. The team found that adding small amounts of alloying elements, like magnesium, can help close the voids and help the battery continue to function. The team captured it in real-time with high-resolution videos that showed what happens inside a battery while it’s working under a scanning electron microscope.

“By carefully adjusting the battery’s chemistry, we can significantly lower the pressure needed to keep it stable,” Lihong Zhao, the first author of this work, a former postdoctoral researcher in Yao’s lab and now an assistant professor of electrical and computer engineering at UH, said in the release. “This breakthrough brings solid-state batteries much closer to being ready for real-world EV applications.”

The team says it plans to build on the alloy concept and explore other metals that could improve battery performance in the future.

“It’s about making future energy storage more reliable for everyone,” Zhao added.

The research was supported by the U.S. Department of Energy’s Battery 500 Consortium under the Vehicle Technologies Program. Other contributors were Min Feng from Brown; Chaoshan Wu, Liqun Guo, Zhaoyang Chen, Samprash Risal and Zheng Fan from UH; and Qing Ai and Jun Lou from Rice.

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