Overcoming a Battery's Fatal Flaw

Estimated reading time: 5 minutes

Texas A&M researchers use supercomputers at the Texas Advanced Computing Center to develop next-generation lithium-metal batteries for electric vehicles, smart grids.

As renewable energy grows as a power source around the world, one key component still eludes the industry: large-scale, stable, efficient and affordable batteries.

Lithium-ion batteries have proven successful for consumer electronics, but electric vehicles, wind turbines or smart grids require batteries with far greater energy capacity. A leading contender is the lithium-metal battery, which differs from lithium ion technology in that it contains lithium metal electrodes.

First conceived in 1912, lithium-metal batteries have the potential for huge amounts of energy storage at a low cost, but they suffer from a fatal flaw: dendrites - sharp needles made of clumps of lithium atoms that can cause batteries to heat up and occasionally short-circuit and catch fire.

However, the promise of the technology has kept researchers and companies working on ways to overcome this problem.

"Lithium-metal batteries are basically the dream batteries since they provide an extremely high energy density," said Reza Shahbazian-Yassar, associate professor of mechanical and industrial engineering at the University of Illinois at Chicago (UIC). "However, we have not been able to build commercially viable lithium-metal batteries with organic liquid electrolytes due to heterogeneous lithium metal plating that leads to dendrites under extended battery cycling."

Recently, teams of researchers, including Shahbazian-Yassar at UIC and Perla Balbuena at Texas A&M University, have been inching closer to finding a solution, in part by applying the power of supercomputers to understand the core chemistry and physics at work in dendrite formation and to engineer new materials that can mitigate dendrite growth.

Writing in Advanced Functional Materials in February 2018, the researchers presented the results of studies into a new material that may solve the long-standing dendrite problem.

"The idea was to develop a coating material that can protect the lithium metal and make the ion deposition much smoother," said Balbuena, professor of Chemical Engineering at Texas A&M and co-author on the paper.

The investigations relied on the Stampede and Lonestar supercomputers at the Texas Advanced Computing Center (TACC) — among the most powerful in the world.

Ion Pachinko

In the paper, the researchers described a graphene oxide nanosheet that can be sprayed onto a glass fiber separator which is then inserted into the battery. The material allows lithium ions to pass through it, but slows down and controls how the ions combine with electrons from the surface to become neutral atoms. Instead of forming needles, the deposited atoms form smooth, flat surfaces at the bottom of the sheet.

The researchers used computer models and simulations in tandem with physical experiments and microscopic imaging to reveal how and why the material effectively controls lithium deposition. They showed that the lithium ions form a thin film on the surface of the graphene oxide and then diffuse through defect sites — essentially gaps in the layers of the material — before settling below the bottom layer of the graphene oxide. The material acts like the pegs in a pachinko game, slowing and directing the metal balls as they fall.

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