Subscribe to our free daily newsletters
  Energy News  




Subscribe to our free daily newsletters



ENERGY TECH
Building a better battery
by Staff Writers
College Station TX (SPX) Jul 03, 2016


Mapping electron density in order of increasing lithiation levels using spectral imaging. Each colored region corresponds to sites where electron density is localized, which also corresponds to high concentrations of Li-ions. "The stripes mark regions that have been extensively lithiated and reduced," Banerjee notes. Image courtesy Luis De Jesus and Texas A and M University. For a larger version of this image please go here.

Forget mousetraps - today's scientists will get the cheese if they manage to build a better battery. An international team led by Texas A and M University chemist Sarbajit Banerjee is one step closer, thanks to new research published in the journal Nature Communications that has the potential to create more efficient batteries by shedding light on the cause of one of their biggest problems - a "traffic jam" of ions that slows down their charging and discharging process.

All batteries have three main components: two electrodes and an intervening electrolyte. Lithium ion batteries work under the so-called rocking-chair model. Imagine discharging and charging a battery as similar to the back-and-forth motion of a rocking chair. As the chair rocks one way, using its stored energy, lithium ions flow out of one electrode through the electrolyte and into the other electrode. Then as the chair rocks the other way, charging the battery after a day's use, the reverse happens, emptying the second electrode of lithium ions.

"Fundamentally, when you have a battery, every time you use it, it starts to die a little bit," Banerjee said. "The more you use it, the more it dies. Eventually, it becomes unusable. Theoretically speaking, you expect a certain performance from a battery, and you rarely ever get there. People have been at a loss to understand all the factors that contribute to this lack of full capacity. This study points us in that direction."

Using one of the world's most powerful soft X-ray microscopes - the Scanning Transmission X-ray Microscope (STXM) - at the Canadian Light Source (CLS) in tandem with decades of combined experience in materials science, Banerjee and collaborators from the Lawrence Berkeley National Laboratory, Binghamton University and the National Institute of Standards and Technology (NIST) were able to image a traffic jam of lithium ions chemically driven through the nanowire-based channels of a simulated battery.

"For a battery to function properly, you need to get lithium ions in, and you need to be able to pull them out," Banerjee said. "Once our lithium ions got in, we were seeing that they sort of stop at some point along the way."

Banerjee points to this interruption as a veritable ghost in the machine that not only slows everything down but also sometimes prevents the device - be it a cell phone or a laptop computer - from exploiting its full battery potential. He says the devil is in the details, which in this case clearly show that the electrons, once coupled with the lithium ions, appear content to sit instead of moving freely, thereby distorting the electronic structure and, in essence, trapping or stranding the flow of energy.

Two of Banerjee's graduate students, Luis De Jesus and Gregory Horrocks, are joint first authors on the Nature paper detailing the team's National Science Foundation-funded research, which also features a third Texas A and M graduate student, Abhishek Parija. Berkeley Lab staff scientist David Prendergast and postdoctoral fellow Yufeng Liang at Berkeley Lab's Molecular Foundry, a U.S. Department of Energy National User Facility for Nanoscale Science Research, helped the Texas A and M team design and implement their calculations, which were experimentally verified by colleagues at Binghamton and using NIST National Synchrotron Light Source beamlines at Brookhaven National Laboratory supervised by Daniel Fischer. Calculations were conducted using Molecular Foundry as well as Texas A and M computing resources.

Berkeley Lab's Prendergast notes that the team's work demonstrates how X-rays can "see" small polarons - the combination of a charged particle (electron) and an associated structural distortion - through their impact on electronic structure around the oxygen atoms in the cathode. Small polarons previously have been proposed to be present in transport within Li-ion cathodes but have not been "seen" directly until now.

In order to make way for additional lithium to enter the structure, Prendergast says, the lithium ions need to diffuse, bringing their electrons in tow. But as a small polaron, it also has to carry along the structural distortion - a real drag for transport of charge in a material.

"Imagine wanting to move a house to a different site," Prendergast said. "A wooden house can be transported in one piece, but a brick or stone house might have to be dismantled or demolished first."

The team also was able to identify the specific site where the electron sits within the particle, down to the orbital. Interestingly enough, De Jesus says, the holdup always occurs at the same material-dependent point.

Once the lithium gets in, Banerjee notes there's a very slight distortion that causes the electrons to get trapped in a plane, where they form what he describes as "puddles of charge" that are unable to link up and move as they should through the material.

"You can always draw an analogy between water and electrons," Banerjee said. "They are making these little puddles, but until the puddles are connected, they can't flow. Once you have enough electrons coming in, they can all link up and start flowing. But until that happens, they're all stranded, and they can't move to charge or discharge something. And so they go out and hang in different areas of the particle. They're all sort of sitting, defining different regions, and they aren't able to move easily."

Banerjee, who joined the Texas A and M Department of Chemistry in 2014 and is an affiliated faculty member in the Department of Materials Science and Engineering, has been working for a number of years to understand ion intercalation, the process by which ions like lithium move in and out of other materials. He says the resulting analysis can be applied in many different areas, including one of his group's specialties - design of better logic circuitry.

"One of the things we look at is, why do devices like cell phones and computers use up so much energy?" Banerjee said. "We're trying to develop new materials to make better circuits that are less energy guzzling. This work hones in on the problem, and it's a really good measurement. In the end, we were able to get to the bottom of the problem."

For Banerjee, it's a result driven by the most basic of energies: curiosity. A couple of years ago, he and Horrocks realized while using conventional laboratory techniques to study the lithiation process in cathode materials that lithium ions would enter nanostructures much faster than they would larger structures. Right then and there, they made it their mission to figure out why smaller was faster - a quest that eventually led them to the Canadian Light Source and an expanded research team featuring, among other top-caliber colleagues, CLS Spectromicroscopy beamline scientist Jian Wang.

"Jian Wang was greatly instrumental, because the reviewers pushed us really hard on making 100 percent sure that what we were seeing was real," Banerjee said.

"The Binghamton group helped us verify some of the predictions in theory. We had an observation; we calculated and matched that in models and then from there the models predicted some other things. They basically said, 'Well, if you're filling an electron into these certain states and they're no longer visible to you by X-ray imaging in a particular region of the spectrum, that means they're already full, so you should be looking for them somewhere else.' So the Binghamton group helped us look elsewhere, and we saw that, too. Once again, that really brings home the entire story."

Binghamton physicist Louis Piper adds that his group has been studying polaron formation and migration in other Li-ion battery cathodes using X-ray spectroscopy methodology. For this particular project, he says, their role was to confirm that the team's calculations were predicting the polaron well by making direct comparisons using another observation method, spatially-averaging hard X-ray photoelectron spectroscopy (HAXPES), which is able to probe occupied energy states.

"The STXM is spatially-resolving but looks at empty states," Piper said. "In my opinion, the STXM shows the spatial effects of the polarons, which is very exciting, while the HAXPES confirmed the energies. The combination meant that we could use the calculations to artificially 'zoom in' with the model.

"I consider our role at Binghamton as keeping the calculations honest. It was nice to see all the approaches converge in this study."

Ultimately, Horrocks and Banerjee agree that building a better battery boils down to figuring out a better way to move electrons - a feat in which size matters and everything points to material.

"There are two ways to solve the problem of moving electrons through cathode material better," Banerjee says.

"One, you can make the stuff smaller or design architectures. Two, you can come up with entirely new materials, which is what we're trying to do. Basically, you prevent the electron from getting stranded because you design the material in such a way that it doesn't have orbitals where they would get stranded. You force them to always be de-localized. We have several materials in mind and are trying to get that research published."


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
Texas A and M University
Powering The World in the 21st Century at Energy-Daily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
ENERGY TECH
Borophene: A prospective extraordinary sodium anode material for sodium-based batteries
Beijing, China (SPX) Jun 28, 2016
Sodium-based batteries have drawn considerable attention as a prospective alternative to lithium-based batteries due to the abundance and low price of sodium element. However, finding a suitable anode material has been a long-standing critical task before the commercialization of sodium-based batteries. As the size of sodium atom is much larger than that of lithium atom, many anode materia ... read more


ENERGY TECH
Sweden's 100 percent carbon-free emissions challenge

Norway MPs vote to go carbon neutral by 2030

Algorithm could help detect and reduce power grid faults

It pays to increase energy consumption

ENERGY TECH
Building a better battery

Activists denounce murder of Philippine anti-coal campaigner

Coal dust kills 23,000 per year in EU: report

Next-generation fluorescent and LED lighting thanks to new phosphor

ENERGY TECH
More wind power added to French grid

How China can ramp up wind power

Scotland investing more in offshore wind

Gamesa, Siemens join forces to create global wind power leader

ENERGY TECH
Scientists explain unusual and effective features in perovskite

'Flower Power': Photovoltaic cells replicate rose petals

Saved by the sun

Energy from sunlight: Further steps towards artificial photosynthesis

ENERGY TECH
EDF nuclear project 'more difficult' after Brexit: Sapin

Expert says most nuclear fuel melted at Fukushima nuclear plant

Mitsubishi joins EDF in bid to save reactor builder Areva

Putin: Russia, China to Step Up Nuclear Energy Cooperation

ENERGY TECH
Study shows trees with altered lignin are better for biofuels

Solar exposure energizes muddy microbes

Chemists find new way to recycle plastic waste into fuel

Bioenergy integrated in the bio-based economy crucial to meet climate targets

ENERGY TECH
China to launch its largest carrier rocket later this year

China committed to peaceful use of outer space

China to launch second space lab Tiangong-2 in September

Upgraded "space shuttle bus" aboard new carrier rocket

ENERGY TECH
Britain's commitment firm on climate: secretary

Climate study finds human fingerprint in Northern Hemisphere greening

Controlled Colorado River flooding released stored greenhouse gases

Future global warming could be even warmer




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement