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Published on January 17th, 2017 | By: April Gocha

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Ultrathin aluminum oxide layer boosts performance of garnet ceramic solid-state batteries

Published on January 17th, 2017 | By: April Gocha

[Image above] Credit: Paralog; Flickr CC BY-ND 2.0

 

 

Batteries are a key technology to reducing the world’s dependence on fossil fuels—we need better batteries that can collect and store energy to meet the high-power demands of today’s and tomorrow’s world.

 

Which is one of many reasons why researchers from all around the globe are working on battery varieties beyond the ubiquitous lithium-ion—including lithium-sulfur batteries, magnesium-ion batteries, flow batteries, sodium-sulfur batteries, and lithium-air batteries.

 

Several varieties of new battery prototypes are finally set to start their quests into the commercial manufacturing arena this year, so it may not be long before we start to see other battery types making inroads into consumer products.

 

For instance, I’ve sung the praises of solid-state batteries before—they offer the potential for batteries that are smaller and safer yet with improved performance. Solid ceramic electrolytes are a safer swap for the potentially explosive liquid electrolytes used in most of today’s batteries.

 

And when it comes to last year’s many battery disasters, safer batteries are prominent on consumers’ minds.

 

A few months ago, ACerS member Richard Laine, professor of materials science and engineering at the University of Michigan, reported that his team is making advances with garnet ceramic materials for solid battery electrolytes.

 

Although garnet’s a great material, garnet electrolytes create high impedance (resistance) between the garnet and the electrodes in a solid-state battery, limiting current flow.

 

High impedance makes it hard for a battery to charge and recharge—which pretty much defeats the purpose of a device that needs to be able to store and discharge energy over and over again.

 

Researchers at the University of Maryland, however, have a solution—they’ve designed a way to insert an ultrathin layer of aluminum oxide in between the garnet and electrodes, decreasing impedance by 300-fold and allowing the energy to flow.

 

“This is a revolutionary advancement in the field of solid-state batteries—particularly in light of recent battery fires, from Boeing 787s to hoverboards to Samsung smartphones,” Liangbing Hu, associate professor of materials science and engineering and one of the corresponding authors of the paper, says in a University of Maryland press release. “Our garnet-based solid-state battery is a triple threat, solving the typical problems that trouble existing lithium-ion batteries: safety, performance, and cost.”

 

The other corresponding author on the paper is Eric Wachsman, ACerS member and Fellow and director of the University of Maryland Energy Research Center and William L. Crentz Centennial Chair in Energy Research, who recently put ceramic materials in the public eye in a segment on CBS This Morning.

 

To solve the impedance problem, the team used atomic layer deposition to squeeze an ultrathin film of aluminum oxide between the battery’s lithium anode and garnet electrolyte LLCZN (Li7La2.75Ca0.25Zr1.75Nb0.25O12).

 

The oxide addition decreased impedance at room temperature from 1,710 Ω·cm2 to 1 Ω·cm2, “effectively negating the lithium metal/garnet interfacial impedance,” the authors write in the paper’s abstract.

 

The authors go on to explain that their experimental and computational results indicate that the oxide coating “enables wetting of metallic lithium in contact with the garnet electrolyte surface and the lithiated-alumina interface allows effective lithium ion transport between the lithium metal anode and garnet electrolyte.”

 

And the researchers themselves aren’t the only ones who realize the impact of their work.

 

“The work effectively solves the lithium metal–solid electrolyte interface resistance problem, which has been a major barrier to the development of a robust solid-state battery technology,” UCLA materials science and engineering professor Bruce Dunn, who wasn’t involved in the research, says in the press release. Dunn is a battery expert—a plenary speaker at MS&T16, he delivered the Edward Orton, Jr. Memorial Lecture on the power and capabilities of batteries, supercapacitors, and pseudocapacitors.

 

And lithium-ion battery guru John B. Goodenough, who wasn’t involved with the work, had good things to say in the release, too. “The [University of Maryland research team] has overcome these problems with two important innovations: first, the composition of the garnet framework was changed to allow fabrication at lower temperatures of a dense polycrystalline solid with tight grain boundaries while retaining a σLi ≈ 10-3 S cm-1; second, application of an ultrathin interphase Al2O3 film between the anode and the garnet electrolyte is shown to prevent the formation of dendrites on plating a lithium anode; therefore, a lithium/garnet interface can be fabricated so as to give a bonded interface with a low impedance to Li+ transport. Reaction of the Al2O3 interphase with Li+ from both the electrolyte and the anode transforms the thin Al2O3 interphase to a Li+ conductor.” Read more of the good stuff Goodenough had to say about the Maryland research here.

 

The paper, published in Nature Materials, is “Negating interfacial impedance in garnet-based solid-state Li metal batteries” (DOI: 10.1038/nmat4821).

 


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