Sandia National Laboratories: Making ‘solid ground’ toward better lithium-ion battery interfaces


5-1-researchersmSchematic of full battery cell architecture and cross-sectional microscopic image of the actual battery. Credit: Sandia National Laboratories

Research at Sandia National Laboratories has identified a major obstacle to advancing solid-state lithium-ion battery performance in small electronics: the flow of lithium ions across battery interfaces.

Sandia’s three-year Laboratory Directed Research and Development project investigated the nanoscale chemistry of , focusing on the region where electrodes and electrolytes make contact. Most commercial  contain a liquid electrolyte and two solid electrodes, but solid-state batteries instead have a solid electrolyte layer, allowing them to last longer and operate more safely.

“The underlying goal of the work is to make solid-state batteries more efficient and to improve the interfaces between different materials,” Sandia physicist Farid El Gabaly said. “In this project, all of the materials are solid; we don’t have a liquid-solid  like in traditional lithium-ion batteries.”

The research was published in a Nano Letters paper titled, “Non-Faradaic Li+ Migration and Chemical Coordination across Solid-State Battery Interfaces.” Authors include Sandia postdoctoral scientist Forrest Gittleson and El Gabaly. The work was funded by the Laboratory Directed Research and Development program, with supplemental funding by the Department of Energy’s Office of Science.

El Gabaly explained that in any lithium , the lithium must travel back and forth from one electrode to the other when it is charged and discharged. However, the mobility of lithium ions is not the same in all materials and interfaces between materials are a major obstacle.

Speeding up the intersection

El Gabaly compares the work to figuring out how to make traffic move quickly through a busy intersection.

“For us, we are trying to reduce the traffic jam at the junction between two materials,” he said.

El Gabaly likened the electrode-electrolyte interface to a tollbooth or merge on a freeway.

“We are essentially taking away the cash tolls and saying everybody needs to go through the fast track, so you’re smoothing out or eliminating the slowdowns,” he said. “When you improve the process at the interface you have the right infrastructure for vehicles to pass easily. You still have to pay, but it is faster and more controlled than people searching for coins in the glove box.”

There are two important interfaces in solid state batteries, he explained, at the cathode-electrolyte junction and electrolyte-anode junction. Either could be dictating the performance limits of a full battery.

Gittleson adds, “When we identify one of these bottlenecks, we ask, ‘Can we modify it?’ And then we try to change the interface and make the chemical processes more stable over time.”

Researchers make solid ground toward better lithium-ion battery interfaces
Sandia National Laboratories researchers Forrest Gittleson, left, and Farid El Gabaly investigate the nanoscale chemistry of solid-state batteries, focusing on the region where electrodes and electrolytes make contact. Credit: Dino Vournas

Sandia’s interest in solid-state batteries

El Gabaly said Sandia is interested in the research mainly because solid-state batteries are low maintenance, reliable and safe. Liquid electrolytes are typically reactive, volatile and highly flammable and are a leading cause of commercial battery failure. Eliminating the liquid component can make these devices perform better.

“Our focus wasn’t on large batteries, like in electric vehicles,” El Gabaly said. “It was more for small or integrated electronics.”

Since Sandia’s California laboratory did not conduct solid-state battery research, the project first built the foundation to prototype batteries and examine interfaces.

“This sort of characterization is not trivial because the interfaces that we are interested in are only a few atomic layers thick,” Gittleson said. “We use X-rays to probe the chemistry of those buried interfaces, seeing through only a few nanometers of material. Though challenging to design experiments, we have been successful in probing those regions and relating the chemistry to full battery performance.”

Processing the research

The research was conducted using materials that have been used in previous proof-of-concept solid-state batteries.

“Since these materials are not produced on a massive commercial scale, we needed to be able to fabricate full devices on-site,” El Gabaly said. “We sought methods to improve the batteries by either inserting or changing the interfaces in various ways or exchanging materials.”

The work used pulsed laser deposition and X-ray photoelectron spectroscopy combined with electrochemical techniques. This allowed very small-scale deposition since the batteries are thin and integrated on a silicon wafer.

“Using this method, we can engineer the interface down to the nanometer or even subnanometer level,” Gittleson said, adding that hundreds of samples were created.

Building batteries in this way allowed the researchers to get a precise view of what that interface looks like because the  can be assembled so controllably.

The next phase of the research is to improve the performance of the batteries and to assemble them alongside other Sandia technologies.

“We can now start combining our batteries with LEDs, sensors, small antennas or any number of integrated devices,” El Gabaly said. “Even though we are happy with our , we can always try to improve it more.”

 Explore further: Toward safer, longer-lasting batteries for electronics and vehicles

More information: Forrest S. Gittleson et al. Non-Faradaic Li+ Migration and Chemical Coordination across Solid-State Battery Interfaces, Nano Letters (2017). DOI: 10.1021/acs.nanolett.7b03498

 

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Rice and Sandia National Labs Discover Unique NanoTube Photodetector


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Project with Sandia National Laboratories leads to promising optoelectronic device

HOUSTON – (Feb. 27, 2013) – Researchers at Rice University and Sandia National Laboratories have made a nanotube-based photodetector that gathers light in and beyond visible wavelengths. It promises to make possible a unique set of optoelectronic devices, solar cells and perhaps even specialized cameras.

A traditional camera is a light detector that captures a record, in chemicals, of what it sees. Modern digital cameras replaced film with semiconductor-based detectors.

But the Rice detector, the focus of a paper that appeared today in the online Nature journal Scientific Reports, is based on extra-long carbon nanotubes. At 300 micrometers, the nanotubes are still only about 100th of an inch long, but each tube is thousands of times longer than it is wide.

That boots the broadband detector into what Rice physicist Junichiro Kono considers a macroscopic device, easily attached to electrodes for testing. The nanotubes are grown as a very thin “carpet” by the lab of Rice chemist Robert Hauge and pressed horizontally to turn them into a thin sheet of hundreds of thousands of well-aligned tubes.

They’re all the same length, Kono said, but the nanotubes have different widths and are a mix of conductors and semiconductors, each of which is sensitive to different wavelengths of light. “Earlier devices were either a single nanotube, which are sensitive to only limited wavelengths,” he said. “Or they were random networks of nanotubes that worked, but it was very difficult to understand why.”

“Our device combines the two techniques,” said Sébastien Nanot, a former postdoctoral researcher in Kono’s group and first author of the paper. “It’s simple in the sense that each nanotube is connected to both electrodes, like in the single-nanotube experiments. But we have many nanotubes, which gives us the quality of a macroscopic device.”

With so many nanotubes of so many types, the array can detect light from the infrared (IR) to the ultraviolet, and all the visible wavelengths in between. That it can absorb light across the spectrum should make the detector of great interest for solar energy, and its IR capabilities may make it suitable for military imaging applications, Kono said. “In the visible range, there are many good detectors already,” he said. “But in the IR, only low-temperature detectors exist and they are not convenient for military purposes. Our detector works at room temperature and doesn’t need to operate in a special vacuum.”

The detector is also sensitive to polarized light and absorbs light that hits it parallel to the nanotubes, but not if the device is turned 90 degrees.

The work is the first successful outcome of a collaboration between Rice and Sandia under Sandia’s National Institute for Nano Engineering program funded by the Department of Energy. François Léonard’s group at Sandia developed a novel theoretical model that correctly and quantitatively explained all characteristics of the nanotube photodetector. “Understanding the fundamental principles that govern these photodetectors is important to optimize their design and performance,” Léonard said.

Kono expects many more papers to spring from the collaboration. The initial device, according to Léonard, merely demonstrates the potential for nanotube photodetectors. They plan to build new configurations that extend their range to the terahertz and to test their abilities as imaging devices. “There is potential here to make real and useful devices from this fundamental research,” Kono said.

Co-authors are Aron Cummings, a postdoctoral fellow in Léonard’s Nanoelectronics and Nanophotonics Group at Sandia; Rice alumnus Cary Pint, an assistant professor of mechanical engineering at Vanderbilt University; Kazuhisa Sueoka, a professor at Hokkaido University; and Akira Ikeuchi and Takafumi Akiho, Hokkaido University graduate students who worked in Kono’s lab as part of Rice’s NanoJapan program. Hauge is a distinguished faculty fellow in chemistry. Kono is a professor of electrical and computer engineering and of physics and astronomy.

The U.S. Department of Energy, the National Institute for Nano Engineering at Sandia National Laboratories, the Lockheed Martin Advanced Nanotechnology Center of Excellence at Rice University, the National Science Foundation and the Robert A. Welch Foundation supported the research.

A Nano Way to Store Hydrogen


October / November 2012By: Tona KunzVolume 10 Number 5
A new type of nanoscale molecular trap makes it possible for industry to store large amounts of hydrogen in small fuel cells or capture, compact and remove volatile radioactive gas from spent nuclear fuel in an affordable, easily commercialized way.

The ability to adjust the size of the trap openings to select for specific molecules or to alter how molecules are released at industrially accessible pressures makes the trap uniquely versatile.  The trap is constructed of commercially available material and made possible through collaborative work at Argonne and Sandia national laboratories.

“This introduces a new class of materials to nuclear waste remediation,” said Tina Nenoff, a Sandia chemist. “This design can capture and retain about five times more iodine that current material technologies.”

Organic molecules linked together with metal ions in a molecular-scale Tinker Toy-like lattice called a metal-organic-framework, or MOF, form the trap. Molecules of radioactive iodine or carbon dioxide or even hydrogen for use as fuel can enter through windows in the framework.
Once pressure is applied, these windows are distorted, preventing the molecules from leaving.  This creates a cage and a way of selecting what to trap based on the molecule’s shape and size.
The compression also turns the MOF from a fluffy molecular sponge taking up a lot of space into a compact pellet.  The ability to compress large amounts of gas into small volumes is a crucial step to developing hydrogen gas as an alternative fuel for engines.

But what makes this MOF, called ZIF-8, dramatically different from designs created during the past decade is its ability to distort the windows in the framework and trap large volumes of gas at relatively low pressures. ZIF-8 takes about twice the pressure of a junkyard car compactor, which is about 10 times less pressure than is needed to compress other comparable zeolite MOFs.

This creates an environmentally friendly process that is within the reach of existing industrial machinery, can be produced on a large scale, and is financially viable.

The ZIF-8 is composed of zinc cations and organic imidazolate-based linkers. The topology of the framework is analogous to sodalite – a well-known zeolite.

The use of other available porous MOFs is limited to small batches because specialized scientific equipment is needed to apply the large amount of pressure they require to compress to a position that will maintain the new shape that traps the gas. This makes them not commercially viable.

Chapman and her colleagues at Argonne used X-rays from the Advanced Photon Source to perfect the low-pressure technique of making the MOFs into dense pellets. The distortion of the molecular framework that occurs during the process does not significantly reduce the gas storage capacity.

“These MOFs have wide-reaching applications,” said Karena Chapman, an Argonne scientist, who was inspired to explore low-pressure treatments for MOFs by her experiences working with flexible MOFs for hydrogen storage. Prior to this work, most high –pressure science research, such as the development of MOFs, took its cue from earth studies were extensive pressures cause transitions in geological materials.

With the pellet process worked out, the scientists tapped Nenoff at Sandia, to find a just the right type of molecule for the MOF’s structure to expand its use from hydrogen and carbon dioxide capture. Nenoff and her team had identified the ZIF-8 MOF as being ideally suited to separate and trap radioactive iodine molecules from a stream of spent nuclear fuel based on its pore size and high surface area.

This marks one of the first attempts to use MOFs in this way.  This presents opportunities for cleaning up nuclear reactor accidents and for reprocessing fuel.  Countries such as France, Russia and India recover fissile materials from radioactive components in used nuclear fuel to provide fresh fuel for power plants. This reduces the amount of nuclear waste that must be stored.  Radioactive iodine has a half-life of 16 million years.

The research team is continuing to look at different MOF structures to increase the amount of iodine storage and better predict how environmental conditions such as humidity will affect the storage lifetime.

Tona Kunz is a writer at Argonne National Laboratory.