EVLN: Next-gen li-metal EV& smart-grid batteries> (ION PACHINKO)

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https://www.sciencedaily.com/releases/2018/03/180328120053.htm
Next-gen lithium-metal batteries for electric vehicles, smart grids
March 28, 2018  

[image  
https://www.sciencedaily.com/images/2018/03/180328120053_1_540x360.jpg
Schematics of lithum deposition mechanism in the case of
graphene-oxide-modified samples. A-F) Adsorption of Li-ions to the
lithiophilic GOn coating and controlled on-site delivery of Li-ions to the
metal surface, leading to a more uniform Li deposition.
Credit: Tara Foroozan, Fernando A. Soto, Vitaliy Yurkiv, Soroosh
Sharifi?Asl, Ramasubramonian Deivanayagam, Zhennan Huang, Ramin Rojaee,
Farzad Mashayek, Perla B. Balbuena, Reza Shahbazian-Yassar
]

Next-gen lithium-metal batteries for electric vehicles, smart grids
Date:    March 28, 2018
Source:    University of Texas at Austin, Texas Advanced Computing Center
Summary:    Electric vehicles, wind turbines or smart grids require
batteries with far greater energy capacity than currently available. A
leading contender is the lithium-metal battery. However, dendrite, or sharp
needles, made of clumps of lithium atoms can cause the batteries to heat up,
lose efficiency and occasionally short-circuit. Using supercomputers,
researchers have simulated the behavior of graphene oxide nanosheets that
can limit the formation of dendrites.


FULL STORY

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.

"Our contribution was to conduct molecular dynamics simulations where we
follow the trajectory of the electrons and atoms in time and observe what's
going on at the atomistic level," Balbuena said. "We were interested in
elucidating how the lithium ions were diffusing through the system and
becoming atoms when the deposition ends in lithium plating."

The graphene-oxide-doped batteries show an enhanced cycle life and exhibit
stability up to 160 cycles, whereas an unmodified battery rapidly loses its
efficiency after 120 cycles. The oxide can be applied simply and affordably
with a spray coating gun.

How the spray is layered on the nanosheets was another focus of the
research. "When you do the experiment, it's not clear at the microscopic
level where the coating will sit," said Balbuena. "It's very thin, so
locating these coatings with precision is not trivial."

Their computer model explored whether it would be more favorable if the
oxide were oriented parallel or perpendicular to the current collector. Both
can be effective, they found, but if deposited in parallel, the material
requires a certain number of defects so ions can slip through.

"The simulations gave our collaborators ideas about the mechanism of ion
transfer through the coating," Balbuena said. "It's possible that some of
the future directions may involve different thickness or chemical
composition based on the phenomenon that we observed."

EXPLORING ALTERNATIVE CATHODE MATERIALS

In separate research, published in ChemSusChem in February 2018, Balbuena
and graduate student Saul Perez Beltran described a battery design that uses
graphene sheets to improve the performance of carbon-sulfur cathodes for
lithium-sulfur batteries, another potential high-capacity storage system.

Besides sulfur's natural abundance, non-toxicity and low-cost, a
sulfur-based cathode is theoretically capable of delivering storage up to 10
times greater than the commonly-used lithium-cobalt oxide cathodes in
conventional lithium ion batteries.

However, chemical reactions in the battery lead to the formation of lithium
polysulfides, chemical compounds containing chains of sulfur atoms.
Long-chain polysulfides are soluble in the liquid electrolyte and migrate to
the lithium metal anode where they decompose, an unwanted effect. On the
other hand, short-chain polysulfides are insoluble and remain at the
sulfur-based cathode. The researchers investigated how the cathode
microstructure may affect this chemistry.

They addressed the problem of uncontrolled polysulfide formation by creating
a sulfur/graphene composite material that avoids the formation of the
soluble long-chain polysulfides. They found that the graphene sheets bring
stability to the cathode and improve its ion trapping capabilities.

Balbuena's research is supported by the Department of Energy as part the
Battery Materials Research and Battery 500 Seedling programs, both of which
are aimed at creating smaller, safer, lighter-weight and less expensive
battery packs to make electric vehicles more affordable.

Stampede and its follow-on Stampede2 are supported by grants from the
National Science Foundation and allow tens of thousands of researchers from
across the nation to explore problems that could not otherwise we addressed.

"These are very extensive computations, that's why we need high performance
computers," Balbuena said. "We are heavy users of TACC resources and we are
very thankful to The University of Texas for allowing us to use these
facilities."

For Balbuena, supercomputer-powered fundamental research into
next-generation batteries is a perfect synthesis of her interests.

"The research is a combination of chemistry, physics and engineering, all
enabled by computing, this theoretical microscope that can visualize things
through theory."

Story Source:

Materials provided by University of Texas at Austin, Texas Advanced
Computing Center [
https://www.tacc.utexas.edu/
]. Note: Content may be edited for style and length.

Journal Reference:

    Tara Foroozan, Fernando A. Soto, Vitaliy Yurkiv, Soroosh Sharifi-Asl,
Ramasubramonian Deivanayagam, Zhennan Huang, Ramin Rojaee, Farzad Mashayek,
Perla B. Balbuena, Reza Shahbazian-Yassar. Synergistic Effect of Graphene
Oxide for Impeding the Dendritic Plating of Li. Advanced Functional
Materials, 2018; 1705917 DOI: 10.1002/adfm.201705917 [
http://dx.doi.org/10.1002/adfm.201705917
] ... [© 2018 ScienceDaily]
...
https://www.tacc.utexas.edu/-/overcoming-a-battery-s-fatal-flaw
Overcoming A Battery's Fatal Flaw
Texas A&M researchers use supercomputers at the Texas Advanced Computing
Center to develop next-generation lithium-metal batteries for electric
vehicles, smart grids
March 28, 2018 by Aaron Dubrow
Mar 28, 2018 - 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 ...
https://www.tacc.utexas.edu/image/journal/article?img_id=1603173&t=1522183119791


https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201705917
Synergistic Effect of Graphene Oxide for Impeding the Dendritic Plating of
Li
Tara Foroozan
Fernando A. Soto
Vitaliy Yurkiv
Soroosh Sharifi?Asl
Ramasubramonian Deivanayagam
Zhennan Huang
Ramin Rojaee
Farzad Mashayek
Perla B. Balbuena
Reza Shahbazian?Yassar
First published: 7 February 2018
https://doi.org/10.1002/adfm.201705917

Dendritic growth of lithium (Li) has severely impeded the practical
application of Li?metal batteries. Herein, a 3D conformal graphene oxide
nanosheet (GOn) coating, confined into the woven structure of a glass fiber
separator, is reported, which permits facile transport of Li?ions thought
its structure, meanwhile regulating the Li deposition. Electrochemical
measurements illustrate a remarkably enhanced cycle life and stability of
the Li?metal anode, which is explained by various microscopy and modeling
results. Utilizing scanning electron microscopy, focused ion beam, and
optical imaging, the formation of an uniform Li film on the electrode
surface in the case of GO?modified samples is revealed. Ab initio molecular
dynamics (AIMD) simulations suggest that Li?ions initially get adsorbed to
the lithiophilic GOn and then diffuse through defect sites. This delayed Li
transfer eliminates the “tip effect” leading to a more homogeneous Li
nucleation. Meanwhile, C?C bonds rupture observed in the GO during AIMD
simulations creates more pathways for faster Li?ions transport. In addition,
phase?field modeling demonstrates that mechanically rigid GOn coating with
proper defect size (smaller than 25 nm) can physically block the anisotropic
growth of Li. This new understanding is a significant step toward the
employment of 2D materials for regulating the Li deposition.

Supporting Information
https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1002%2Fadfm.201705917&attachmentId=2172021970

https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1002%2Fadfm.201705917&attachmentId=2172021969

https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1002%2Fadfm.201705917&attachmentId=2172021971
[© 2018 John Wiley & Sons]


+
http://www.valleymorningstar.com/news/local_news/start-your-engines-utrgv-electric-car-race-is-first-of/article_d2312d70-3acb-11e8-9807-47bcd95af686.html
Start your engines: UTRGV electric car race is first of its kind in Texas
April 7, 2018- BROWNSVILLE — With the sweep of a green starting flag,
Brownsville Mayor Tony Martinez gave the signal that officially revved up
the inaugural HESTEC GreenpowerUSA South Texas Electric Car Competition
yesterday at the Brownsville South Padre Island International Airport ...
https://bloximages.newyork1.vip.townnews.com/valleymorningstar.com/content/tncms/assets/v3/editorial/3/dc/3dc31680-3acb-11e8-9124-5fd15ac22321/5ac96eba5de44.image.jpg




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