The UCF researchers developing new energy technologies (left to right): Zhao Li, Kyle Marcus, Kun Liang, Yang Yang, Guanzhi Wang and Wenhan Niu. Photo: UCF.
The UCF researchers developing new energy technologies (left to right): Zhao Li, Kyle Marcus, Kun Liang, Yang Yang, Guanzhi Wang and Wenhan Niu. Photo: UCF.

The research group of Yang Yang, an assistant professor at the University of Central Florida (UCF), has developed two promising energy storage technologies as part of work with sustainable energy systems. Yang sees revolutionary systems able to produce and store energy inexpensively and efficiently as a potential solution to energy and environmental crises.

"We try to convert solar energy either to electricity or chemical fuels. We also try to convert chemical fuels to electricity. So, we do different things, but all of them are related to energy," said Yang, who came to UCF in 2015 and has joint appointments in the NanoScience Technology Center and the Department of Materials Science and Engineering.

One of the researchers' new technologies would upgrade the lithium-ion batteries that are ubiquitous in today's laptops, smartphones, portable electronics and electric vehicles. The other offers a safer, more stable alternative to lithium-ion batteries.

As they report in a recent paper in Advanced Energy Materials, the UCF researchers designed a new type of electrode for lithium-ion batteries that displays excellent conductivity, is stable at high temperatures and cheap to manufacture. Most significantly, it offers a way for a high-performance lithium-ion battery to be recharged thousands of times without degrading.

Batteries generate electrical current when ions pass from the negative terminal, or anode, to the positive terminal, or cathode, through an electrolyte. Yang's group developed a battery cathode made from a thin-film alloy of nickel sulfide and iron sulfide, and showed that this combination of materials brings big advantages to their new electrode.

On their own, nickel sulfide and iron sulfide display good conductivity. But the conductivity is even better when they're combined, the researchers found.

They were able to boost the conductivity even more by making the cathode from a thin film of nickel sulfide and iron sulfide, and then etching the thin film to cover it in nanopores, which greatly expanded the surface area available for chemical reactions. "This is really transformative thin-film technology," Yang said.

All batteries eventually begin degrading after they've been drained and recharged over and over again. Quality lithium-ion batteries can be drained and recharged about 300 to 500 times before they begin to lose capacity. Tests showed that a battery with the nickel sulfide-iron sulfide cathode could be depleted and recharged more than 5000 times before degrading.

Researchers Kun Liang and Kyle Marcus from Yang's group worked on the project. Collaborators included Le Zhou, Yilun Li, Samuel De Oliveira, Nina Orlovskaya and Yong-Ho Sohn, all at UCF, and Shoufeng Zhang of Jilin University in China and Yilun Li of Rice University.

Graduate student researchers in Yang's lab have also developed a new catalyst for a high-efficiency battery that has several advantages over conventional ones. Metal-air batteries, fuel cells and other energy storage and conversion technologies rely on chemical reactions to produce current. In turn, these reactions require an efficient catalyst to help them along. Precious metals including platinum, palladium and iridium have proven to be efficient catalysts, but their high cost and poor stability and durability make them impractical for large-scale commercialization.

Researchers in Yang's group led by Wenhan Niu, Zhao Li and Kyle Marcus have now developed a new process for creating a catalyst comprising cobalt-based nanoparticles on a substrate made of graphene, a highly conductive two-dimensional material with the thickness of a single atom.

As reported in another paper in Advanced Energy Materials, the researchers showed the effectiveness of their catalyst's nanomesh-like structure by testing it in a zinc-air battery, demonstrating its ability to be depleted and recharged many times. This electrocatalyst is safer and more stable than the volatile compounds found in lithium-ion batteries, and can function in rain, extreme temperatures and other harsh conditions. Furthermore, without the need for precious metals, it can be manufactured more cheaply.

This story is adapted from material from the University of Central Florida, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.