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New Technique Produces Longer-lasting Lithium Batteries

Posted By Graphene Council, The Graphene Council, Monday, April 29, 2019
Updated: Friday, April 26, 2019
The grand challenge to improve energy storage and increase battery life, while ensuring safe operation, is becoming evermore critical as we become increasingly reliant on this energy source for everything from portable devices to electric vehicles. A Columbia Engineering team led by Yuan Yang, assistant professor of materials science and engineering, announced that they have developed a new method for safely prolonging battery life by inserting a nano-coating of boron nitride (BN) to stabilize solid electrolytes in lithium metal batteries. Their findings are outlined in a new study published by Joule.

While conventional lithium ion (Li-ion) batteries are currently widely used in daily life, they have low energy density, resulting in shorter battery life, and, because of the highly flammable liquid electrolyte inside them, they can short out and even catch fire. Energy density could be improved by using lithium metal to replace the graphite anode used in Li-ion batteries: lithium metal’s theoretical capacity for the amount of charge it can deliver is almost 10 times higher than that of graphite. But during lithium plating, dendrites often form and, if they penetrate the membrane separator in the middle of the battery, they can create short-circuits, raising concerns about battery safety.

“We decided to focus on solid, ceramic electrolytes. They show great promise in improving both safety and energy density, as compared with conventional, flammable electrolytes in Li-ion batteries,” says Yang. “We are particularly interested in rechargeable solid-state lithium batteries because they are promising candidates for next-generation energy storage.”

Most solid electrolytes are ceramic, and therefore non-flammable, eliminating safety concerns. In addition, solid ceramic electrolytes have a high mechanical strength that can actually suppress lithium dendrite growth, making lithium metal a coating option for battery anodes. However, most solid electrolytes are unstable against Li—they can be easily corroded by lithium metal and cannot be used in batteries.

“Lithium metal is indispensable for enhancing energy density and so it’s critical that we be able to use it as the anode for solid electrolytes,” says Qian Cheng, the paper’s lead author and a postdoctoral research scientist in the department of applied physics and applied mathematics who works in Yang's group. “To adapt these unstable solid electrolytes for real-life applications, we needed to develop a chemically and mechanically stable interface to protect these solid electrolytes against the lithium anode. It is essential that the interface not only be highly electronically insulating, but also ionically conducting in order to transport lithium ions. Plus, this interface has to be super-thin to avoid lowering the energy density of batteries.”

To address these challenges, the team worked with colleagues at Brookhaven National Lab and the City University of New York. They deposited 5~10 nm boron nitride (BN) nano-film as a protective layer to isolate the electrical contact between lithium metal and the ionic conductor (the solid electrolyte), along with a trace quantity of polymer or liquid electrolyte to infiltrate the electrode/electrolyte interface. They selected BN as a protective layer because it is chemically and mechanically stable with lithium metal, providing a high degree of electronic insulation. They designed the BN layer to have intrinsic defects, through which lithium ions can pass through, allowing it to serve as an excellent separator. In addition, BN can be readily prepared by chemical vapor deposition to form large-scale (~dm level), atomically thin scale (~nm level), and continuous films.

“While earlier studies used polymeric protection layers as thick as 200 µm, our BN protective film, at only 5~10 nm thick, is record-thin—at the limit of such protection layers—without lowering the energy density of batteries,” Cheng says. “It’s the perfect material to function as a barrier that prevents the invasion of lithium metal to solid electrolyte. Like a bullet-proof vest, we’ve developed a lithium-metal-proof ‘vest’ for unstable solid electrolytes and, with that innovation, achieved long-cycling lifetime lithium metal batteries.”

The researchers are now extending their method to a broad range of unstable solid electrolytes and further optimizing the interface. They expect to fabricate solid-state batteries with high performance and long-cycle lifetimes.
 

Tags:  Batteries  Boron Nitride  Columbia Engineering  Graphene  Li-Ion batteries  Qian Cheng  Yuan Yang 

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Both Graphene and Financial Expertise Leads to Unique Graphene Player

Posted By Dexter Johnson, IEEE Spectrum, Tuesday, September 18, 2018

About four years ago, Alan Dalton, a professor at the University of Sussex in the UK, made some news in graphene circles when, in collaboration with colleagues at Trinity College Dublin, he demonstrated that rubber bands when combined with graphene could serve as effective health monitors.  A couple of years later, Dalton continued to make news by using graphene to link together silver nanowires to create a material that could potentially replace indium tin oxide (ITO) as a transparent conductor in touch-screen displays. The following year in 2017, Dalton, serving as chief scientific officer, joined with an experienced group of individuals, led by CEO John Lee, who had a long career in energy and cleantech equity markets, to form Advanced Material Development (AMD).

While the work of Dalton along with a focus on graphene remains part of the company’s genetic makeup, it has established itself first and foremost as a company set up to support scientific research in materials science conducted at British Universities.

Using a unique process, AMD already has a commercially available product it has dubbed “nHance” that includes graphene, molybdenum disulfide and boron nitride in dispersions for use in a range of bespoke emulsions and applications. The patent-pending emulsions have been developed with the University of Sussex.

In addition to having a commercial product in hand, AMD also has secured £750,000 ($985,000) in funding in April to support its commercialization aims and has now commenced R&D funding.

As a corporate partner to the Graphene Council, we got an opportunity to conduct a Q&A with John Lee, the CEO of AMD and below is that interview.

Q: Could you give a little bit more background on the nature of AMD’s business? It seems to at least initially to be a company based on the research of Alan Dalton at the University of Sussex. But it seems that you are also open to any technologies in the area of graphene and 2D materials that might be licensable. Could you explain a bit more about how AMD has set itself up and what its business models and strategies are?

Advanced Material Development Ltd (AMD) is a UK-based, privately funded business recently formed to support scientific research in British universities. The first collaboration, with leading academic Professor Alan Dalton from the University of Sussex Material Physics Group will fund several distinct research streams within the field of 2D materials. AMD is already engaged in a number of key partnerships with other commercial enterprises to further work in areas such as composites, coatings, printed electronics and wearable sensors. In addition, AMD is also producing nano-dispersion inks and emulsions under the brand name “nHance” for its own internal R&D efforts and also for commercial sale.

Q: Some of the work of Alan Dalton that got the most publicity was the simple process he developed for infusing graphene into elastic bands so that they become extremely sensitive strain sensors. Is that a line of research your company is looking to commercialize? If so, what sort of landmarks have you reached in the development of this technology? If not, what went behind the decision not to follow that line of research into commercial applications?

Although AMD supplies materials into this and other ongoing projects, it is not a programme we are funding at this point. IP in this area is already well established, allocated, and outside of our core focus. Our website outlines the areas that we are keen to support.

Q: At the moment, you have likely narrowed down the technologies you are pursuing commercially. Could you say what those technologies currently are and why you chose to pursue those over some others?

One of the main areas of focus for AMD is producing nano-dispersion inks and emulsions. These support our own R&D work and also provide a foundation for bespoke materials formulations being developed for partners. This is a key reason why we choose to keep our R&D efforts within the University - to retain a critical high-end capability. Our other efforts in coatings, flexible electronics, composites and medtech sensors all sit nicely on this platform technology.

Q: In the broader market of graphene, what applications area do you see holding the most commercial potential and what is your company doing to be a part of those applications? If you are not, why have you chosen to not get involved, i.e. already too many competitors, etc.?

There are plenty of key verticals that have obvious areas of application for these materials. The graphene “fatigue” described by some early adopters comes from the frustration associated with a cure-all mentality. The hard to come-by knowledge and critical component that the team is focused on is the ability to disperse these materials into other matrices to provide a worthwhile benefit. We have chosen to support the areas of R&D where the University team can demonstrate a path to commercial interest, notably electronics in the consumer supply chain, material composites and medtech sensors where we consider there to be a realistic pathway to a commercial endgame within two years.

Q: Where do you see AMD in the value chain of graphene, i.e. a manufacturer of devices based on graphene or a company that enables other companies to make devices based on graphene?

The answer really is both. Although AMD cannot claim to be a manufacturer of devices and hence is not fully vertically integrated, it is already a materials manufacturer and is funding research with an end-game goal of prototype applications that we can then market to heavyweight commercial partners, a number of which, we are already doing early development work for or are in discussions to do so.

Q. As a company trying to bring emerging technologies to market, what do you see as the greatest challenges you face, i.e. customers resistant to change, lack of standards in graphene, etc.?

It’s been said that the greatest fear of many start-up companies is the threat of its ideas being stolen. The truth is that taking a product, however good and trying to convince someone already overwhelmed with new ideas and getting them to listen is a huge challenge. But the main problem I see at the moment is that many companies are a little burned by engaging with the graphene dream without having had the right degree of support to see the proper benefits – the lack of standards until now has been a major bugbear in this outcome and so these are vital. However, whatever the standard, no size fits all and the varying material requirements for different applications, like nature, are unlikely to conform to the categories we try to define.

Q. Over the next 5-10 years, how do you see the graphene market developing, i.e. fewer graphene producers and more downstream device producers?

I would agree with this outlook – ultimately graphene and other 2D materials will commoditize as production scales and applications become more accepted, but this will need the development of end-markets to facilitate such growth. I believe the real secret is the integration of the right formulation into devices that solve real world challenges.

Tags:  boron nitride  finance  Medical devices  touch screen displays 

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Boron nitride-graphene hybrid for next-gen energy storage

Posted By Terrance Barkan, Tuesday, October 25, 2016

Layers of graphene separated by nanotube pillars of boron nitride may be a suitable material to store hydrogen fuel in cars, according to Rice University scientists.

The Department of Energy has set benchmarks for storage materials that would make  a practical fuel for light-duty vehicles. The Rice lab of materials scientist Rouzbeh Shahsavari determined in a new computational study that pillared boron nitride and graphene could be a candidate.

The study by Shahsavari and Farzaneh Shayeganfar appears in the American Chemical Society journal Langmuir.

Shahsavari's lab had already determined through computer models how tough and resilient pillared graphene structures would be, and later worked boron nitride nanotubes into the mix to model a unique three-dimensional architecture. (Samples of  seamlessly bonded to graphene have been made.)

Just as pillars in a building make space between floors for people, pillars in boron nitride graphene make space for hydrogen atoms. The challenge is to make them enter and stay in sufficient numbers and exit upon demand.

In their latest molecular dynamics simulations, the researchers found that either pillared graphene or pillared boron nitride graphene would offer abundant surface area (about 2,547 square meters per gram) with good recyclable properties under ambient conditions. Their models showed adding oxygen or lithium to the materials would make them even better at binding hydrogen.

They focused the simulations on four variants: pillared structures of boron nitride or pillared boron nitride graphene doped with either oxygen or lithium. At room temperature and in ambient pressure, oxygen-doped boron nitride graphene proved the best, holding 11.6 percent of its weight in hydrogen (its gravimetric capacity) and about 60 grams per liter (its volumetric capacity); it easily beat competing technologies like porous boron nitride, metal oxide frameworks and carbon nanotubes.

At a chilly -321 degrees Fahrenheit, the material held 14.77 percent of its weight in hydrogen.

The Department of Energy's current target for economic storage media is the ability to store more than 5.5 percent of its weight and 40 grams per liter in hydrogen under moderate conditions. The ultimate targets are 7.5 weight percent and 70 grams per liter.

Shahsavari said  adsorbed to the undoped pillared boron nitride graphene, thanks to weak van der Waals forces. When the material was doped with oxygen, the atoms bonded strongly with the hybrid and created a better surface for incoming hydrogen, which Shahsavari said would likely be delivered under pressure and would exit when pressure is released.

"Adding oxygen to the substrate gives us good bonding because of the nature of the charges and their interactions," he said. "Oxygen and hydrogen are known to have good chemical affinity."

He said the polarized nature of the  where it bonds with the graphene and the electron mobility of the graphene itself make the material highly tunable for applications.

"What we're looking for is the sweet spot," Shahsavari said, describing the ideal conditions as a balance between the material's surface area and weight, as well as the operating temperatures and pressures. "This is only practical through computational modeling, because we can test a lot of variations very quickly. It would take experimentalists months to do what takes us only days."

He said the structures should be robust enough to easily surpass the Department of Energy requirement that a hydrogen fuel tank be able to withstand 1,500 charge-discharge cycles.


SOURCE: PHYS.ORG 

Tags:  Boron Nitride  Boron nitride-graphene hybrid  Department of Energy  Energy Storage 

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