Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Microscopic defects make batteries better

30.10.2017

Rice University-led study reveals unknown details about common lithium-ion battery materials

Department of Energy Office of Basic Energy Science, National Science Foundation, University of Wisconsin-Madison WEI Seed Grant, Vilas Research Travel Awards


An illustration shows the growth of a lithium-deficient phase (blue) at the expense of a Lithium-rich phase (red) in a lithium iron phosphate microrod. Rice University researchers led a study that found defects in a common cathode material for lithium-ion batteries can potentially improve performance over perfect electrodes by allowing for lithium transport over much more surface area than previously thought possible.

Credit: Mesoscale Materials Modeling Group/Rice University

HOUSTON -- (Oct. 30, 2017) -- High-performance electrodes for lithium-ion batteries can be improved by paying closer attention to their defects -- and capitalizing on them, according to Rice University scientists.

Rice materials scientist Ming Tang and chemists Song Jin at the University of Wisconsin-Madison and Linsen Li at Wisconsin and the Massachusetts Institute of Technology led a study that combined state-of-the-art, in situ X-ray spectroscopy and modeling to gain insight into lithium transport in battery cathodes. They found that a common cathode material for lithium-ion batteries, olivine lithium iron phosphate, releases or takes in lithium ions through a much larger surface area than previously thought.

"We know this material works very well but there's still much debate about why," Tang said. "In many aspects, this material isn't supposed to be so good, but somehow it exceeds people's expectations."

Part of the reason, Tang said, comes from point defects -- atoms misplaced in the crystal lattice -- known as antisite defects. Such defects are impossible to completely eliminate in the fabrication process. As it turns out, he said, they make real-world electrode materials behave very differently from perfect crystals.

That and other revelations in a Nature Communications paper could potentially help manufacturers develop better lithium-ion batteries that power electronic devices worldwide.

The lead authors of the study -- Liang Hong of Rice and Li of Wisconsin and MIT -- and their colleagues collaborated with Department of Energy scientists at Brookhaven National Laboratory to use its powerful synchrotron light sources and observe in real time what happens inside the battery material when it is being charged. They also employed computer simulations to explain their observations.

One revelation, Tang said, was that microscopic defects in electrodes are a feature, not a bug.

"People usually think defects are a bad thing for battery materials, that they destroy properties and performance," he said. "With the increasing amount of evidence, we realized that having a suitable amount of point defects can actually be a good thing."

Inside a defect-free, perfect crystal lattice of a lithium iron phosphate cathode, lithium can only move in one direction, Tang said. Because of this, it is believed the lithium intercalation reaction can happen over only a fraction of the particle's surface area.

But the team made a surprising discovery when analyzing Li's X-ray spectroscopic images: The surface reaction takes place on the large side of his imperfect, synthesized microrods, which counters theoretical predictions that the sides would be inactive because they are parallel to the perceived movement of lithium.

The researchers explained that particle defects fundamentally change the electrode's lithium transport properties and enable lithium to hop inside the cathode along more than one direction. That increases the reactive surface area and allows for more efficient exchange of lithium ions between the cathode and electrolyte.

Because the cathode in this study was made by a typical synthesis method, Tang said, the finding is highly relevant to practical applications.

"What we learned changes the thinking on how the shape of lithium iron phosphate particles should be optimized," he said. "Assuming one-dimensional lithium movement, people tend to believe the ideal particle shape should be a thin plate because it reduces the distance lithium needs to travel in that direction and maximizes the reactive surface area at the same time. But as we now know that lithium can move in multiple directions, thanks to defects, the design criteria to maximize performance will certainly look quite different."

The second surprising observation, Tang said, has to do with the movement of phase boundaries in the cathode as it is charged and discharged.

"When you take heat out of water, it turns into ice," he said. "And when you take lithium out of these particles, it forms a different lithium-poor phase, like ice, that coexists with the initial lithium-rich phase." The phases are separated by an interface, or a phase boundary. How fast the lithium can be extracted depends on how fast the phase boundary moves across a particle, he said.

Unlike in bulk materials, Tang explained, it has been predicted that phase boundary movement in small battery particles can be limited by the surface reaction rate. The researchers were able to provide the first concrete evidence for this surface reaction-controlled mechanism, but with a twist.

"We see the phase boundary move in two different directions through two different mechanisms, either controlled by surface reaction or lithium bulk diffusion," he said. "This hybrid mechanism paints a more complicated picture about how phase transformation happens in battery materials. Because it can take place in a large group of electrode materials, this discovery is fundamental for understanding battery performance and highlights the importance of improving the surface reaction rate."

###

The paper's co-authors are graduate student Fan Wang of Rice, Jun Wang, Yuchen-Karen Chen-Wiegart and Jiajun Wang of Brookhaven National Laboratory, Kai Xiang and Yet-Ming Chiang of MIT, and Liyang Gan, Wenjie Li and Fei Meng of the University of Wisconsin-Madison. Tang is an assistant professor of materials science and nanoengineering at Rice.

The research was supported by the U.S. Department of Energy (DOE) Office of Basic Energy Science, the National Science Foundation (NSF), a University of Wisconsin-Madison WEI Seed Grant and the Vilas Research Travel Awards. Research was also conducted at the Department of Energy's Argonne National Laboratory. The Texas Advanced Computing Center at the University of Texas at Austin and the National Energy Research Scientific Computing Center funded by the DOE and the Big-Data Private-Cloud Research Cyberinfrastructure funded by the NSF and Rice provided computing resources.

Read the abstract at http://dx.doi.org/10.1038/s41467-017-01315-8

DOI: 10.1038/s41467-017-01315-8

This news release can be found online at news.rice.edu

Follow Rice News and Media Relations via Twitter @RiceUNews

Related materials:

Mesoscale Materials Modeling Group (Tang): http://tanggroup.blogs.rice.edu/research/

Rice Department of Materials Science and NanoEngineering: https://msne.rice.edu Images for download:

http://news.rice.edu/files/2017/10/1030_LITHIUM-1-WEB-1gor1gn.jpg

An illustration shows the growth of a lithium-deficient phase (blue) at the expense of a Lithium-rich phase (red) in a lithium iron phosphate microrod. Rice University researchers led a study that found defects in a common cathode material for lithium-ion batteries can potentially improve performance over perfect electrodes by allowing for lithium transport over much more surface area than previously thought possible. (Credit: Mesoscale Materials Modeling Group/Rice University)

http://news.rice.edu/files/2017/10/1030_LITHIUM-2-WEB-1e2d6d5.jpg

An electron microscope image shows microrod particles of the type used in a Rice University-led study of lithium transport in lithium-ion batteries. (Credit: Linsen Li and Song Jin/University of Wisconsin Madison)

http://news.rice.edu/files/2017/10/1030_LITHIUM-3-WEB-1abpsjl.jpg

Rice University researchers Liang Hong, left, and Ming Tang study the lithium transport characteristics of batteries. They and their colleagues discovered that defects in common lithium-ion battery cathodes can potentially improve the material's performance over "perfect" electrodes. (Credit: Jeff Fitlow/Rice University)

http://news.rice.edu/files/2017/10/1030_LITHIUM-4-WEB-10fw5jv.jpg

A stack of batteries in the Rice University lab of Ming Tang, an assistant professor of materials science and nanoengineering, who led a team that discovered defects in cathodes can potentially add to the performance of lithium-ion batteries. (Credit: Jeff Fitlow/Rice University)

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,879 undergraduates and 2,861 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for quality of life and for lots of race/class interaction and No. 2 for happiest students by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

Media Contact

David Ruth
david@rice.edu
713-348-6327

 @RiceUNews

http://news.rice.edu 

David Ruth | EurekAlert!

More articles from Materials Sciences:

nachricht The stacked colour sensor
16.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

nachricht Counterfeits and product piracy can be prevented by security features, such as printed 3-D microstructures
16.11.2017 | Karlsruher Institut für Technologie (KIT)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>