SB-BNL Team’s discoveries may lead to better batteries

SB-BNL Team’s discoveries may lead to better batteries

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They help start car engines, provide light in the darkness, keep music playing as joggers circumnavigate their towns, and help send signals to hearts that might otherwise have irregular beats. They are, of course, batteries.

The fact that they work is something everyone understands as soon as they flip a switch. What no one can see completely yet, though, is what happens on a small scale as a battery discharges.

Mostly encased in stainless steel, the inner workings of a battery have been difficult to measure directly. A much-heralded hire from two years ago, who divides her time between Stony Brook and Brookhaven National Laboratory, Esther Takeuchi has teamed up with several other scientists to gather new clues about the changes in a battery as it discharges.

“We’re looking at the internal anatomy of a battery without taking it apart,” said Takeuchi, a distinguished professor with an appointment in the department of chemistry and the department of materials Science and engineering at Stony Brook and a chief scientist at BNL’s Basic Energy Sciences Directorate.

Takeuchi and her team worked at BNL’s National Synchrotron Light Source, where they stopped batteries at various times and measured them with the kind of x-rays that penetrate the steel casing. These provide a resolution on the scale of 20 microns, which is about 1/4 the width of a human hair.

By understanding on a more precise level what happens inside a battery, scientists may provide insight that enables a greater understanding of the best architecture or design for a battery.

“The way we understand a battery could change dramatically,” said study co-author Amy Marschilok, a research associate professor in materials science and engineering at Stony Brook. “We’re taking” the inner workings of a battery “from black box science to more [open] science, where we can see and understand what’s happening. We’re on the verge of that type of discovery right now.”

In general, Takeuchi said batteries may work at about 80 percent efficiency, depending on the type of battery or its use. That, she said, could increase with a design that makes best use of the developing environment in the battery as it functions.

The results of the study, which included Takeuchi’s husband Kenneth, who is a distinguished teaching professor at Stony Brook, Marschilok, BNL scientist Zhong Zhong, BNL postdoc Kevin Kirshenbaum and Stony Brook graduate student David Bock, were published in the prestigious journal Science.

The research team used these bright x-ray beams to study lithium batteries that have a special silver material at the cathode, the place from which current departs, that has high stability, high voltage and spontaneous matrix formation.

As the batteries, which Bock created, discharge, lithium ions from the anode travel to the cathode, displacing silver ions in the process. Coupling with free electrons and unused cathode material, the displaced silver forms a conductive silver metal matrix that enables electrons to flow.

The research demonstrated that a slow discharge rate early in the battery’s life creates a more uniform network.

“When we started activating the battery, the cathode spontaneously, within its own structure, starts forming small parts, or ions, of silver metal,” Takeuchi said. “The silver ions are reduced to silver metal. What’s really interesting is that, because we’re forming silver metal, we have something we can measure.”

The results of the experiment provided a clearer understanding of the steps the battery goes through. The last part of the battery to activate is the center.

In some batteries, the flow of electrons may just reach the edges and never have access to the middle.

Takeuchi, who left the University at Buffalo to come to Long Island, said she is excited by the opportunities at Stony Brook and BNL. This past June, Stony Brook led a multi-institution group that received a $10 million Energy Frontier Research Center Award from the Department of Energy.

Takeuchi is convinced she made the right decision to move to Long Island.

“The willingness of Stony Brook and BNL to commit to this field was appealing to me,” Takeuchi said. “They recognize how important it is, to Long Island, nationally, and globally. We have the opportunity to make a difference.”