Graphene Coating could help Prevent Lithium Battery Fires


Car in

Lithium batteries are what allow electric vehicles to travel several hundred miles on one charge. Their capacity for energy storage is well known, but so is their tendency to occasionally catch on fire—an occurrence known to battery researchers as “thermal runaway.” These fires occur most frequently when the batteries overheat or cycle rapidly. With more and more electric vehicles on the road each year, battery technology needs to adapt to reduce the likelihood of these dangerous and catastrophic fires.

Researchers from the University of Illinois at Chicago College of Engineering report that graphene—wonder material of the 21st century—may take the oxygen out of lithium battery fires. They report their findings in the journal Advanced Functional Materials.

The reasons  catch fire include rapid cycling or charging and discharging, and  in the battery. These conditions can cause the cathode inside the battery—which in the case of most lithium batteries is a lithium-containing oxide, usually lithium cobalt oxide—to decompose and release oxygen. If the oxygen combines with other flammable products given off through decomposition of the electrolyte under high enough heat, spontaneous combustion can occur.

“We thought that if there was a way to prevent the oxygen from leaving the cathode and mixing with other flammable products in the battery, we could reduce the chances of a fire occurring,” said Reza Shahbazian-Yassar, associate professor of mechanical and industrial engineering in the UIC College of Engineering and corresponding author of the paper.

It turns out that a material Shahbazian-Yassar is very familiar with provided a perfect solution to this problem. That material is graphene—a super-thin layer of carbon atoms with unique properties. Shahbazian-Yassar and his colleagues previously had used graphene to help modulate lithium buildup on electrodes in lithium metal batteries.

graphenecoat

Lithium cobalt oxide particles coated in graphene. Credit: Reza Shahbazian-Yassar.

Shahbazian-Yassar and his colleagues knew that graphene sheets are impermeable to oxygen atoms. Graphene is also strong, flexible and can be made to be electrically conductive. Shahbazian-Yassar and Soroosh Sharifi-Asl, a graduate student in mechanical and  at UIC and lead author of the paper, thought that if they wrapped very small particles of the lithium cobalt oxide cathode of a lithium battery in graphene, it might prevent oxygen from escaping.

First, the researchers chemically altered the graphene to make it electrically conductive. Next, they wrapped the tiny particles of lithium cobalt oxide cathode electrode in the conductive graphene.

When they looked at the -wrapped lithium cobalt oxide particles using electron microscopy, they saw that the release of oxygen under high heat was reduced significantly compared with unwrapped particles.

Next, they bound together the wrapped particles with a binding material to form a usable cathode, and incorporated it into a lithium metal battery. When they measured released oxygen during battery cycling, they saw almost no oxygen escaping from cathodes even at very high voltages. The lithium metal battery continued to perform well even after 200 cycles.

“The wrapped cathode battery lost only about 14% of its capacity after rapid cycling compared to a conventional  metal battery where performance was down about 45% under the same conditions,” Sharifi-Asl said.

“Graphene is the ideal material for blocking the release of oxygen into the electrolyte,” Shahbazian-Yassar said. “It is impermeable to oxygen, electrically conductive, flexible, and is strong enough to withstand conditions within the battery. It is only a few nanometers thick so there would be no extra mass added to the . Our research shows that its use in the  can reliably reduce the release of  and could be one way that the risk for fire in these batteries—which power everything from our phones to our cars—could be significantly reduced.”


Explore further

Liquid microscopy technique reveals new problem with lithium-oxygen batteries

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Einstein’s Theory of ‘entanglement’ (aka – spooky action) goes massive


Quantum Entangle 1 download

Perhaps the strangest prediction of quantum theory is entanglement, a phenomenon whereby two distant objects become intertwined in a manner that defies both classical physics and a “common-sense” understanding of reality. In 1935, Albert Einstein expressed his concern over this concept, referring to it as “spooky action at a distance”.

Nowadays, entanglement is considered a cornerstone of quantum mechanics, and it is the key resource for a host of potentially transformative quantum technologies. Entanglement is, however, extremely fragile, and it has previously been observed only in microscopic systems such as light or atoms, and recently in superconducting electric circuits.

In work recently published in Nature, a team led by Prof. Mika Sillanpää at Aalto University in Finland has shown that entanglement of massive objects can be generated and detected.

The researchers managed to bring the motions of two individual vibrating drumheads – fabricated from metallic aluminium on a silicon chip – into an entangled quantum state. The objects in the experiment are truly massive and macroscopic compared to the atomic scale: the circular drumheads have a diametre similar to the width of a thin human hair.

The team also included scientists from the University of New South Wales Canberra in Australia, the University of Chicago, and the University of Jyväskylä in Finland. The approach taken in the experiment was based on a theoretical innovation developed by Dr. Matt Woolley at UNSW and Prof. Aashish Clerk, now at the University of Chicago.

‘The vibrating bodies are made to interact via a superconducting microwave circuit. The electromagnetic fields in the circuit are used to absorb all thermal disturbances and to leave behind only the quantum mechanical vibrations,’ says Mika Sillanpää, describing the experimental setup.

Eliminating all forms of noise is crucial for the experiments, which is why they have to be conducted at extremely low temperatures near absolute zero, at -273 °C. Remarkably, the experimental approach allows the unusual state of entanglement to persist for long periods of time, in this case up to half an hour.

Quantum Entangle 2 2873c6e954901a23c40ff5afdf8a924d

‘These measurements are challenging but extremely fascinating. In the future, we will attempt to teleport the mechanical vibrations. In quantum teleportation, properties of physical bodies can be transmitted across arbitrary distances using the channel of “spooky action at a distance”,’ explains Dr. Caspar Ockeloen-Korppi, the lead author on the work, who also performed the measurements.

The results demonstrate that it is now possible to have control over large mechanical objects in which exotic quantum states can be generated and stabilized. Not only does this achievement open doors for new kinds of quantum technologies and sensors, it can also enable studies of fundamental physics in, for example, the poorly understood interplay of gravity and quantum mechanics. einstein_solving_problems_zpsde94bc7e

The experimental research was carried out at the OtaNano national research infrastructure for micro- and nanotechnologies in Finland, and was funded also by the European Research Council, the European Union’s Horizon 2020 research and innovation programme, and by the Academy of Finland.

Stabilized entanglement of massive mechanical oscillators’.C. F. Ockeloen-Korppi, E. Damskägg, J.-M. Pirkkalainen, A. A. Clerk, F. Massel, M. J. Woolley, M. A. Sillanpää: ‘Stabilized entanglement of massive mechanical oscillators’. Nature 556, 7702 (2018). https://doi.org/10.1038/s41586-018-0038-x

For More Information:

Mika Sillanpää, Professor
Aalto University, Department of Applied Physics

 Matt Woolley, Senior Lecturer
UNSW Canberra, School of Engineering and Information Technology

Researchers make atoms-thick Post-It notes for solar cells and circuits: U of Chicago


23-scientistsmaSchematic diagram (left) and electron microscope image (right) of a stacked set of semiconductor films, made using the Park lab’s new technique. Credit: Park et. al./Nature

Over the past half-century, scientists have shaved silicon films down to just a wisp of atoms in pursuit of smaller, faster electronics. For the next set of breakthroughs, though, they’ll need novel ways to build even tinier and more powerful devices.

A study led by UChicago researchers, published Sept. 20 in Nature, describes an innovative method to make stacks of semiconductors just a few atoms thick. The technique offers scientists and engineers a simple, cost-effective method to make thin, uniform layers of these materials, which could expand capabilities for devices from solar cells to cell phones.

Stacking thin layers of materials offers a range of possibilities for making  with unique properties. But manufacturing such  is a delicate process, with little room for error.

“The scale of the problem we’re looking at is, imagine trying to lay down a flat sheet of plastic wrap the size of Chicago without getting any  in it,” said Jiwoong Park, a UChicago professor with the Department of Chemistry, the Institute for Molecular Engineering and the James Franck Institute, who led the study. “When the material itself is just atoms thick, every little stray atom is a problem.”

Today, these layers are “grown” instead of stacking them on top of one another. But that means the bottom layers have to be subjected to harsh growth conditions such as high temperatures while the new ones are added—a process that limits the materials with which to make them.

Park’s team instead made the films individually. Then they put them into a vacuum, peeled them off and stuck them to one another, like Post-It notes. This allowed the scientists to make films that were connected with weak bonds instead of stronger covalent bonds—interfering less with the perfect surfaces between the layers.

“The films, vertically controlled at the atomic-level, are exceptionally high-quality over entire wafers,” said Kibum Kang, a postdoctoral associate who was the first author of the study.

Kan-Heng Lee, a graduate student and co-first author of the study, then tested the films’ electrical properties by making them into devices and showed that their functions can be designed on the atomic scale, which could allow them to serve as the essential ingredient for future computer chips.

The method opens up a myriad of possibilities for such films. They can be made on top of water or plastics; they can be made to detach by dipping them into water; and they can be carved or patterned with an ion beam. Researchers are exploring the full range of what can be done with the method, which they said is simple and cost-effective.

“We expect this new  to accelerate the discovery of novel , as well as enabling large-scale manufacturing,” Park said.

 Explore further: A simple additive to improve film quality

More information: “Layer-by-layer assembly of two-dimensional materials into wafer-scale heterostructures,” Kang et. al, Nature, Sept. 20. DOI: 10.1038/nature23905

 

Improved Solar Cell Efficiency with New Polymer


PolymerSolarNew light has been shed on solar power generation using devices made with polymers, thanks to collaboration between scientists in the University of Chicago’s chemistry department, the Institute for Molecular Engineering and Argonne National Laboratory.

Researchers identified a new polymer—a type of large molecule that forms plastics and other familiar materials—that improved the efficiency of solar cells. The group also determined the method by which the polymer improved the cells’ efficiency. The polymer allows electrical charges to move more easily throughout the cell, boosting the production of electricity—a mechanism never before demonstrated in such devices.

“Polymer solar cells have great potential to provide low-cost, lightweight and flexible electronic devices to harvest solar energy,” said Luyao Lu, graduate student in chemistry and lead author of a paper describing the result, published online last month in the journal Nature Photonics.

Solar cells made from polymers are a popular topic of research due to their appealing properties, but researchers are still struggling to efficiently generate electrical power with these materials.

“The field is rather immature—it’s in the infancy stage,” said Luping Yu, professor in chemistry and fellow in the Institute for Molecular Engineering, who led the UChicago group carrying out the research.

The active regions of such solar cells are composed of a mixture of polymers that give and receive electrons to generate electrical current when exposed to light. The new polymer developed by Yu’s group, called PID2, improves the efficiency of electrical power generation by 15% when added to a standard polymer-fullerene mixture.

“Fullerene, a small carbon molecule, is one of the standard materials used in polymer solar cells,” Lu said. “Basically, in polymer solar cells we have a polymer as electron donor and fullerene as electron acceptor to allow charge separation.” In their work, the UChicago-Argonne researchers added another polymer into the device, resulting in solar cells with two polymers and one fullerene.

 

Luyao Lu, a graduate student in chemistry, works in the solar cell characterization facility of the University of Chicago’s Gordon Center for Integrative Science. Lu is the lead author of a Nature Photonics article describing the development of a new type of polymer solar cell that displays enhanced power conversion efficiency. Image: Andrew NellesLuyao Lu, a graduate student in chemistry, works in the solar cell characterization facility of the University of Chicago’s Gordon Center for Integrative Science. Lu is the lead author of a Nature Photonics article describing the development of a new type of polymer solar cell that displays enhanced power conversion efficiency. Image: Andrew Nelles

8.2% efficiency

The group achieved an efficiency of 8.2% when an optimal amount of PID2 was added—the highest ever for solar cells made up of two types of polymers with fullerene—and the result implies that even higher efficiencies could be possible with further work. The group is now working to push efficiencies toward 10%, a benchmark necessary for polymer solar cells to be viable for commercial application.

The result was remarkable not only because of the advance in technical capabilities, Yu noted, but also because PID2 enhanced the efficiency via a new method. The standard mechanism for improving efficiency with a third polymer is by increasing the absorption of light in the device. But in addition to that effect, the team found that when PID2 was added, charges were transported more easily between polymers and throughout the cell.

In order for a current to be generated by the solar cell, electrons must be transferred from polymer to fullerene within the device. But the difference between electron energy levels for the standard polymer-fullerene is large enough that electron transfer between them is difficult. PID2 has energy levels in between the other two, and acts as an intermediary in the process.

“It’s like a step,” Yu said. “When it’s too high, it’s hard to climb up, but if you put in the middle another step then you can easily walk up.”

Thanks to collaboration with Argonne, Yu and his group were also able to study the changes in structure of the polymer blend when PID2 was added, and show that these changes likewise improved the ability of charges to move throughout the cell, further improving the efficiency. The addition of PID2 caused the polymer blend to form fibers, which improve the mobility of electrons throughout the material. The fibers serve as a pathway to allow electrons to travel to the electrodes on the sides of the solar cell.

“It’s like you’re generating a street and somebody that’s traveling along the street can find a way to go from this end to another,” Yu said.

To reveal this structure, Wei Chen of the Materials Science Division at Argonne National Laboratory and the Institute for Molecular Engineering performed x-ray scattering studies using the Advanced Photon Source at Argonne and the Advanced Light Source at Lawrence Berkeley National Laboratory.

“Without that it’s hard to get insight about the structure,” Yu said, calling the collaboration with Argonne “crucial” to the work. “That benefits us tremendously,” he said.

Chen noted that “Working together, these groups represent a confluence of the best materials and the best expertise and tools to study them, to achieve progress beyond what could be achieved with independent efforts.”

“This knowledge will serve as a foundation from which to develop high-efficiency organic photovoltaic devices to meet the nation’s future energy needs,” Chen said.

Ternary blend polymer solar cells with enhanced power conversion efficiency

Source: Univ. of Chicago

Nanotechnology key to new Desalination System


QDOTS imagesCAKXSY1K 8(Nanowerk News) The scarcity of fresh water is an  increasingly serious problem around the world due to growing populations and  diminishing supplies of fresh water. Desalination could help alleviate these  shortages, but it has traditionally been an extremely expensive process.
The demand for water is so great that the worldwide desalination  market is expected to reach an astonishing $87.8 billion by 2016, even though  only about 1 percent of the world’s drinking water is produced by desalination.  There is a huge need for technologies that could reduce this cost.
To help meet this need, the Innovation Fund, the University of  Chicago’s venture philanthropic proof-of-concept fund, awarded Heinrich Jaeger, the William J. Friedman and Alicia Townsend  Professor of Physics at the University of Chicago, $65,000 in its third round of  funding at the end of 2011 to establish the commercial feasibility of a  nanoparticle desalination system that Jaeger invented.
Heinrich Jaeger, the William J. Friedman and Alicia Townsend Professor of Physics at the University of Chicago
A  grant from the University of Chicago’s Innovation Fund will help Heinrich  Jaeger, PhD, establish the commercial feasibility of a nanoparticle desalination  system.
“In order for desalination to become a real solution to the  growing water scarcity problem, new technologies will be required to reduce the  major cost components of the process,” says Sean Sheridan, an assistant director  at UChicagoTech, which administers the Innovation Fund. “Professor Jaeger’s  nanofiltration technology represents a promising step towards achieving this  goal.”
The high cost of traditional desalination is driven by the price  of energy for high-pressure systems and the capital cost of high-pressure pumps  and seals. Today, recovery of capital and electric power add up to as much as  73% of the cost of desalinated water.
“Our system has the potential to cut these costs by using an  ultrathin self-assembled nanoparticle membrane,” Jaeger says. “Due to its  extreme thinness and excellent permeability characteristics, this nanofiltration  membrane can be used for a wide range of nanofiltration processes at low  pressures, including desalination.”  
The nanofiltration membrane was developed by Jaeger and Xiao-Min  Lin, scientist at Argonne’s Center for Nanoscale Materials, together with  University of Chicago postdocs Jinbo He, Edward Barry and Sean McBride. At about  30 nanometers, it is the world’s thinnest and has unique features that may turn  out to make the crucial difference with this technology. The size, shape and  chemical structure of the membrane’s pores can be systematically tuned to  optimize its filtration properties. As a result, it allows 100 times more flow  at the same pressure. In addition, the self-assembly process used to fabricate  it reduces costs.
UChicagoTech’s role
Jaeger has a close working relationship with UChicagoTech, which  is committed to supporting University faculty as they work to translate bench  science to commercial applications. He regularly updates the office on his new  ideas and research results. After he approached UChicagoTech with his initial  data about the nanofiltration system, UChicagoTech helped him to develop a  business proposal and present the opportunity to the Innovation Fund.  UChicagoTech also filed an international patent application at the end of 2012  to protect the technology.
“The Innovation Fund award has been extremely helpful by giving  us not only financial support to further develop this technology in a timely  manner but also by connecting us with a highly supportive group of industry  experts and entrepreneurs,” Jaeger says.
The award is helping to optimize the low-pressure ion  rejection/permeation characteristics for the product; develop and test a system  that is environmentally friendly, compatible with drinking water standards, and  scalable for the production of large volumes of water; and design an assembly  process that is compatible with existing commercial filtration systems.
Initially, Jaeger intends to target small, distributed or mobile  water treatment systems. After being proven on a small scale, the technology  could attract additional funding and be developed for larger systems.
“The potential of this technology to establish a new class of  nanofiltration devices is an exciting prospect,” Jaeger says. “Many purification  processes in a wide range of industries depend on nanofiltration and could  benefit greatly from highly specialized and tunable parameters in a low-pressure  technology. UChicagoTech’s help has been indispensible.”
Source: By Greg Borzo, University of Chicago

Read more: http://www.nanowerk.com/news2/newsid=29442.php#ixzz2bEPuwE4i

Nanotechnology Key to New Desalination System


Nanowerk News) The scarcity of fresh water is an  increasingly serious problem around the world due to growing populations and  diminishing supplies of fresh water. Desalination could help alleviate these  shortages, but it has traditionally been an extremely expensive process. The demand for water is so great that the worldwide desalination  market is expected to reach an astonishing $87.8 billion by 2016, even though  only about 1 percent of the world’s drinking water is produced by desalination.  There is a huge need for technologies that could reduce this cost. To help meet this need, the Innovation Fund, the University of  Chicago’s venture philanthropic proof-of-concept fund, awarded Heinrich Jaeger, the William J. Friedman and Alicia Townsend  Professor of Physics at the University of Chicago, $65,000 in its third round of  funding at the end of 2011 to establish the commercial feasibility of a  nanoparticle desalination system that Jaeger invented.

Dr. Jaegger

A grant from the University of Chicago’s Innovation Fund will help Heinrich  Jaeger, PhD, establish the commercial feasibility of a nanoparticle desalination  system.

“In order for desalination to become a real solution to the  growing water scarcity problem, new technologies will be required to reduce the  major cost components of the process,” says Sean Sheridan, an assistant director  at UChicagoTech, which administers the Innovation Fund. “Professor Jaeger’s  nanofiltration technology represents a promising step towards achieving this  goal.”
The high cost of traditional desalination is driven by the price  of energy for high-pressure systems and the capital cost of high-pressure pumps  and seals. Today, recovery of capital and electric power add up to as much as  73% of the cost of desalinated water.
“Our system has the potential to cut these costs by using an  ultrathin self-assembled nanoparticle membrane,” Jaeger says. “Due to its  extreme thinness and excellent permeability characteristics, this nanofiltration  membrane can be used for a wide range of nanofiltration processes at low  pressures, including desalination.”
The nanofiltration membrane was developed by Jaeger and Xiao-Min  Lin, scientist at Argonne’s Center for Nanoscale Materials, together with  University of Chicago postdocs Jinbo He, Edward Barry and Sean McBride. At about  30 nanometers, it is the world’s thinnest and has unique features that may turn  out to make the crucial difference with this technology. The size, shape and  chemical structure of the membrane’s pores can be systematically tuned to  optimize its filtration properties. As a result, it allows 100 times more flow  at the same pressure. In addition, the self-assembly process used to fabricate  it reduces costs.
UChicagoTech’s role
Jaeger has a close working relationship with UChicagoTech, which  is committed to supporting University faculty as they work to translate bench  science to commercial applications. He regularly updates the office on his new  ideas and research results. After he approached UChicagoTech with his initial  data about the nanofiltration system, UChicagoTech helped him to develop a  business proposal and present the opportunity to the Innovation Fund.  UChicagoTech also filed an international patent application at the end of 2012  to protect the technology.
“The Innovation Fund award has been extremely helpful by giving  us not only financial support to further develop this technology in a timely  manner but also by connecting us with a highly supportive group of industry  experts and entrepreneurs,” Jaeger says.
The award is helping to optimize the low-pressure ion  rejection/permeation characteristics for the product; develop and test a system  that is environmentally friendly, compatible with drinking water standards, and  scalable for the production of large volumes of water; and design an assembly  process that is compatible with existing commercial filtration systems.
Initially, Jaeger intends to target small, distributed or mobile  water treatment systems. After being proven on a small scale, the technology  could attract additional funding and be developed for larger systems.
“The potential of this technology to establish a new class of  nanofiltration devices is an exciting prospect,” Jaeger says. “Many purification  processes in a wide range of industries depend on nanofiltration and could  benefit greatly from highly specialized and tunable parameters in a low-pressure  technology. UChicagoTech’s help has been indispensible.”
Source: By Greg Borzo, University of  Chicago