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Graphene Lays Foundation for Fast Charging High Capacity Li-ion Batteries

Posted By Dexter Johnson, IEEE Spectrum, Thursday, June 14, 2018

Prof. Dina Fattakhova-Rohlfing. (Image: FZ Juelich)

Graphene has been earmarked for energy storage applications for years. The fact that graphene is just surface area is very appealing to battery applications in which anodes and electrodes store energy in the material that covers them.

With lithium ion (Li-ion) batteries representing the most ubiquitous battery technology, with uses ranging from our smart phones to electric cars, increasing their storage capacity and shortening their charging times with graphene has been a big research push. 

Unfortunately, the prospects for graphene in energy storage have been stalled for years. This is in part due to the fact that while graphene is all surface area, in order to get anywhere near the kind of storage capacity of today’s activated carbon you need to layer graphene. The result after enough layering is you end up back with graphite, defeating the purpose of using graphene in the first place.

Now a team of German researchers has developed an approach for improving the anodes of Li-ion batteries that uses graphene in support of tin oxide nanoparticles.

"In principle, anodes based on tin dioxide can achieve much higher specific capacities, and therefore store more energy, than the carbon anodes currently being used. They have the ability to absorb more lithium ions," said Dian Fattakhova-Rohlfing, a researcher at Forschungszentrum Jülich research institute in Germain, in a press release. "Pure tin oxide, however, exhibits very weak cycle stability – the storage capability of the batteries steadily decreases and they can only be recharged a few times. The volume of the anode changes with each charging and discharging cycle, which leads to it crumbling."

The research described in the Wiley journal Advanced Functional Materials, uses graphene as a base layer in a hybrid nanocomposite in which the tin oxide nanoparticles enriched with antimony are layered on top of the graphene. The graphene provides structural stability to the nanocomposite material.

The combination of the tin oxide nanoparticle being enriched with antimony makes them extremely conductive, according to Fattakhova-Rohlfing. "This makes the anode much quicker, meaning that it can store one-and-a-half times more energy in just one minute than would be possible with conventional graphite anodes. It can even store three times more energy for the usual charging time of one hour."

The scientists found that in contrast to most batteries the high energy density did not have to come with very slow charging rates. Anybody who has a smartphone knows how long it takes to charge it to 100 percent.

"Such high energy densities were only previously achieved with low charging rates," says Fattakhova-Rohlfing. "Faster charging cycles always led to a quick reduction in capacity."

In contrast, the research found that their antimony-doped anodes retain 77 percent of their original capacity even after 1,000 cycles.

Because tin oxide is abundant and cheap, the scientists claim that the nanocomposite anodes can be produced in an easy and cost-effective way.

Fattakhova-Rohlfing added: "We hope that our development will pave the way for lithium-ion batteries with a significantly increased energy density and very short charging time."

Tags:  energy storage  Li-ion batteries  nanocomposites  nanoparticles 

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Fraunhofer IPA Maps Out Its Graphene Strategy

Posted By Dexter Johnson, IEEE Spectrum, Thursday, November 30, 2017

The Fraunhofer Institute for Manufacturing Engineering and Automation IPA uses the tagline: “We manufacture the future”.

Certainly as one of the leading research institutes in the world for the development of automotive technology, Fraunhofer has a global reputation for delivering the latest cutting edge breakthroughs in any technology associated with the automotive industry from energy storage to lightweight engineering.

Based on Fraunhofer’s titanic reputation in R&D, it was a stroke of luck that The Graphene Council was able to meet up with Fraunhofer’s Head of Functional Materials, Ivica Kolaric, at the Economist’s “The Future of Materials Summit” held in Luxembourg in mid-November.

In his role as leader of the functional material group at Fraunhofer, Kolaric has been conducting research on nanoscale carbon materials, like graphene, for almost 20 years. The aim of all this work has consistently been to produce functionalized nanoscale carbon materials to bring them to industrial applications.

Kolaric and his team have been working specifically on graphene since 2008 and have been synthesizing graphene using both chemical vapor deposition (CVD) as well as exfoliation techniques. With these various grades of graphene, the Fraunhofer researchers have experimented with a variety of applications.

“We first started with applications in the field of energy storage and transparent conductive films,” said Kolaric in an interview at the Luxembourg conference.  “As you may remember there was a big discussion a few years back going on if graphene could serve as a replacement for idium tin oxide (ITO).  But we determined that this is maybe not the right application for graphene because when you use it large areas for conductive films it’s competing with commodity products.”

Kolaric also explained that Fraunhofer had collaborated with battery manufacturer Maxell in the development of different types of energy storage devices, specifically supercapacitors. They had some success in increasing the energy density of these devices, which is an energy storage device’s ability to store a charge. With the graphene, the increased surface area of graphene did give a boost to storage capabilities but it just couldn’t deliver enough of an increase in performance over its costs, according to Kolaric.

Now Kolaric says that Fraunhofer is looking at graphene in sensor applications, in particular biosensors. “Graphene is really a perfect substrate for doping, so you can make it sensitive for any kind of biological effects,” said Kolaric. “This could make it a very good biosensor.”

But Kolaric cautions that avenues for purification have to be developed. If this and other issues can be addressed with graphene, there is the promise of a sensor technology that could be very effective at detecting gases, which currently is tricky for automotive sensors that are restricted to detecting pressure and temperature. “I think graphene can play an important role in this,” added Kolaric.

In addition to next generation sensors, Kolaric believes that graphene’s efficiency as a conductor could lead to it being what he terms an “interlink” on the submicron level. Kolaric believes that this will lead to its use in power electronics.

Kolaric added: “I would say sensors and serving as an interlink, so these are the two occasions where we think graphene can be effective.”

Tags:  biosensors  energy storage  Fraunhofer Institute  indium tin oxide  ITO  sensors  supercapacitors 

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CealTech AS - Endless Possibilities

Posted By Dexter Johnson, IEEE Spectrum, Thursday, January 5, 2017

Established in 2012, Norway-based CealTech AS is already staking claim to being the largest volume producer of graphene in the world. This past year, 2016, was a big year in the company’s development with a number of landmark events occurring, perhaps most notably bringing online a new production unit with capacity of 10,000m3 of single layer graphene

If graphene is going to find use in a more applications, companies like CealTech will undoubtedly play a key role in making that happen by providing high-quality graphene at a competitive price. The company is also moving up the value chain with plans of bringing online this year a large-scale battery production unit that will use graphene on the electrodes

As the newest member of The Graphene Council’s corporate members we took the opportunity to discuss with them how they see graphene and its applications evolving and how they are positioning themselves in this changing landscape. To do this we spoke with the company’s CEO, Runar Tunem.

Q: Your website makes the claim of having the largest volume production of graphene globally. Can you say what forms of graphene you are producing, i.e. graphene platelets, and how do your volumes breakdown according to those different forms and how they supply your various markets?

A: CealTech produces graphene in powder form. Our graphene is produced by a patented plasma-enhanced chemical vapor deposition (PE-CVD) technology based on DA Boyd, W-H Lin, C-C Hsu, ML Teague, C-C Chen, Y-Y Lo, W-Y Chan, W-B Su, TC Cheng, C-S Chang, et al. Single-step deposition of high-mobility graphene at reduced temperatures. Nature Communications, 6, 2015.

The patent pending FORZA™ production unit makes it possible to produce different types of graphene depending on application. More recently, Dr. David Boyd was able to optimize the process for mass production and the quality of the graphene flakes has been found to be very good. Another advantage of the production unit is that flakes can be directly functionalized according to the intended application, e.g. nitrogen and or oxygen functional groups, without any chemical modification. 

Q: In your company’s estimates what is the global production of graphene in all its forms and what percentage of the production does your company represent?

A: Regarding the volumes of graphene, a 28 tons global production was reported in 2010, which is projected to grow to about 575-600 tons by this year. Our estimate lies within the same range for fine- and for ultra-fine graphite. It is important to differentiate between graphite products from graphene’s, as both materials have different properties.

We do expect that the market for pure graphene will grow by leaps and bounds in the coming decade. This will be possible thanks to the advances in manufacturing processes which will address the main challenge of producing large quantities of graphene, in various formats, and at an affordable price, with effective yields and a purity sufficient so as not to impair graphene’s desired chemical properties. In that respect, we believe that CealTech’s technology will be a major enabler, and will contribute to taking graphene to the next level, as we soon start our commercial production of graphene – currently planned from March 2017. CealTech’s expected yearly production volume of pure graphene (from March 2017) is 10,000m3, and this volume will be adjusted (i.e. ramped-up) to accommodate the market needs.

Q: What were the market drivers in demand that spurred your company to make such a large increase in production capacity this year?

A: Over the last couple of years, CealTech has conducted a comprehensive research program aimed at assessing if the use of fine and ultra-fine graphite helped to enhance the properties of a wide range of engineering materials. Examples of the materials investigated by the program are rubber, paints, lacquers, carbon fibers, glass fiber, etc. 

During the research program, it became apparent that neither the fine nor the ultra-fine graphite available on today’s market are suitable to attaining such a goal. In comparison, when using the pure graphene produced by our patented PE-CVD technique, we achieved great results by significantly improving the properties of the different materials studied by the program. This learning process was one of the catalysts for CealTech to set sight at becoming the world’s largest manufacturer of PE-CVD graphene. 

Q:  Going forward what market segments do you see requiring the most volume of graphene? And, what are the markets that will likely exhibit the largest profit margins for graphene producers?

A: The application segments are currently dominated by electronics industry. Due to its high strength and conduction property, graphene is (to be) widely used in this industry. Apart from touch screens for tablets and mobile phones, it can also be used to make circuitry of laptops and personal computers, making them run faster. Also, due to its low thickness, it can be used as a semiconductor. Its chips are faster than the existing silicon chips. The electronics industry is driven by growing demand from the Asia Pacific region and a manufacturing rebound in the U.S. brought on by the economic slowdown of 2007 to 2009. In addition, growing markets for smartphones, tablets, high-definition TVs are further expected to boost the global electronics industry.

Composites accounted for the second largest share (36%) of graphene applications in 2016, dispersed among the automotive, plastics, coatings, construction, metals and engineering materials, aerospace, medical implants and energy markets. These composites can enhance the strength and conductivity of bulk materials. The composites and coatings have also found applications in sports, including lawn tennis and Formula 1 racing.

Looking ahead, Energy Storage and Supercapacitors are expected to emerge as a key area for PE-CVD graphene, followed by composites and graphene coatings. Graphene inks are said to be constantly improving (while their prices seem to be dropping), which might promote, among others, applications like sensor electrodes and smart packaging. Reports project that energy storage will account for around 40%, and composites, 25%, of the market by 2026, and that nearly $100 million worth of graphene will be sold into the energy storage sector in 2026.

Currently, graphene commercialization follows primarily a supplementation/substitution strategy. While products marketed as ‘graphene’ may be on the market in 2016, many, if not all, are still likely (to be) constructed principally from more traditional materials and incorporate a limited quantity of graphite. Accordingly, the profit margins are or will be, to some extent, dictated by the type of graphite used (i.e. quality), and/or the cost of the material that graphene is attempting to substitute. For example, on the low end of the graphene market is bulk material used as a filler to provide strength and conductivity in future day-to-day composite products.

The market for carbon fiber composites was $16,479.4 million in 2013, and was expected to grow at a rate of 12.8% annually from 2014 to 2019 with bulk carbon costs on the order of half-a-dollar per gram. Graphene could replace these products if sold at lower costs. Profit margins on the bulk material are likely to be minimal but significant profits will be made through large volumes. On the other end of the spectrum, the highest quality graphene will be used in applications that are being developed that require graphene, or where the use of high-quality graphene significantly improves the product specifications and performance; hence justifying a premium price. This material will probably command the highest margins –assuming a market structure similar to cell phones.  Lithium-ion electrodes are an example where graphite is used as an additive to boost the performance of the electrodes and alleviating a key shortcoming: limited cycle life. In this case, profit margins can be proportional to the degree of improvement enabled by graphene, and as such, could be significantly high.

Q: Do you foresee a business model in which your company will become more involved in downstream production of graphene-enabled products, i.e. moving from producing graphene to producing graphene-enabled products?

A: Further to producing and supplying large volume, high quality PE-CVD Graphene, CealTech is committed to developing and commercializing Graphene-enabled products and solutions for major industries, such as but no limited to: defense, automotive, space & aerospace, energy storage, electronics and sensors, medicine, maritime, and oil & gas. In that respect, our business portfolio is set to encompass everything from Raw Material (i.e. the graphene itself), Manufactured Materials (i.e. graphene doped with oxygen, nitrogen organic and inorganic molecules, etc.), to Component Parts and Finished Products (i.e. battery electrodes, conductive inks, paints and coatings, etc.). On the latter, we are proud to say that we are well on track with the development of a new, revolutionary battery technology. The test results so far are very promising (to be published online soon), and the aim is for an in-house annual production capacity of 20 millions square meters of CealTech’s PE-CVD graphene-based electrodes.

Furthermore, we are working with several leading companies, both nationally in Norway and internationally, to implement our PE-CVD graphene in various industrial products. You will have to stay tuned for more information…

Q: In the mid-2000s, some large chemical companies, like Bayer, drastically increased carbon nanotube production (multi-walled carbon nanotubes) with the idea that the resulting lowered costs of the material would help drive demand. The demand never picked up enough to soak up the increased capacity. What sort of precautions are graphene producers taking to avoid this same kind of pitfall?

A: To answer this, one must try to understand the likely reasons for this ‘pitfall’.

Firstly, one can cite the intrinsic problems of Carbon Nanotubes themselves. In an ideal perfect world, the carbon atoms that form nanotubes should be arranged in a hexagonal network. In this way, each carbon atom is bonded to three other carbon atoms making a sp2 bond, but that is when the nanotubes are perfect and they are of a uniform diameter. However, in reality, there are defects in the nanotubes that cause sp3 bonding to occur. Defects can be observed in the gradual widening or narrowing along the length of nanotubes. Also, nanotubes are not flat, and therefore cannot accurately be modeled with sp2 bond characters. Subsequently, CNTs suffer from lack of control of physical and chemical properties, difficulties in scalability, as well as the high cost of production and purification thus limiting the range of their applications.

In contrast, our produced Graphene with its Sp2 bonding means that the carbon has a ONE double bond. For a carbon with 1 double bond and 2 single bonds, the orbitals will become 33% "s" and 66.7% "p" making our graphene "sp2." That means that our graphene does not suffer from the same issues as nanotubes as all of our graphene sheets are identical, and therefore its properties are easily reproduced.

Secondly, it is reasonable to say that while some observers believed that the price cut of the MWNT would result in the applications being developed, it was soon recognized that this was a case of putting the cart before the horse, or “technology push” ahead of the preferable “market pull.” In contrast, we see a more downstream-focused approach for the graphene, with the aim of fostering concrete commercial benefits across key industries. As such, significant investments have been made in recent years to hasten the pace at which we start to see more practical applications of graphene and new technologies. For example, the European Union has invested $1.3 billion in ‘The Graphene Flagship’, a consortium of academic and commercial researchers, tasked with taking graphene from the realm of academic laboratories into European society in the space of 10 years, thus generating economic growth, new jobs and new opportunities. Similar efforts are taken by governments across the world (such as USA, China, UK, Japan, South Korea, Singapore, Malaysia, etc.) to build awareness about the vast potential of graphene and to facilitate partnerships and collaborations across the various stakeholders in the ecosystem (e.g., between industry and academia, and/or between upstream and downstream producers). For example, the UK Government has provided £235 million ($353 million) to fund a graphene research center. Tech companies are investing in developing their understanding of the material. Samsung, for example, has already applied for hundreds of graphene-related patents. Furthermore, we see that Graphene producers are also on the ‘offensive’, continuously innovating and developing new technologies aligned to targeted market needs and requirements.    

For CealTech’s part, we know that our technology expertise and business strategy address both points above. First, our unique PE-CVD Graphene will be of high quality, produced at large scale, in a reproducible manner, and soon to be commercially available. Accordingly, CealTech is strongly committed to having a resilient and flexible supply chain to ensure fast turnaround times and close customer relationships for its graphene production. Second, we acknowledge the risk of being only in the business of producing a nanomaterial that serves just to make some other product. Therefore, and as mentioned above, we are also focused on developing graphene-enabled products for various industrial applications. We are collaborating with other leading companies to contribute to bringing graphene-enhanced products to the market.

Q: What do you see being some of the graphene-enabled products that are most likely to grow significantly over the next five years and how will that shape graphene production?

A: As stated above, it is expected that graphene continues to be used mainly as a supplementary material in the short term (and through to 2020 at least), until the manufacturing process for graphene is mature enough for it to be used as a key material in products. Barriers to widespread industry uptake mirror carbon nanotubes: functionalization and dispersion; mass manufacturing at an acceptable cost; need for application partnerships; and health and safety issues. So the adoption of graphene and developments of graphene-enabled products depend on how soon these challenges are addressed.

As to which graphene-enabled products are expected to grow the most over the next five years, it is best to refer to interview by the Graphene Council with Prof. Jari Kinaret in his interview – we quote: “The early applications are more likely to use exfoliated graphene flakes than large sheets of graphene. Functional and structural nanocomposites fall in this category – wind power plant blades are one specific example. Other low-hanging fruits are applications where graphene and related materials offer advantages as new or greatly improved functionalities. Here advanced batteries or supercapacitors in anything from portable electric appliances to cars is a promising direction. Also flexible electronics – screens, sensors, smart textiles etc. – are coming strongly. Applications that require large, defect free graphene sheets are likely to take longer time to develop; many solid state electronic applications fall in this category.” We are in perfect agreement with this statement as CealTech and the industry alike, are currently focusing on such products as coatings, batteries, structural composites, functional inks, etc.

Tags:  batteries  CealTech  energy storage  PE-CVD 

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Graphene "Sandwich" Supercapcitor

Posted By Terrance Barkan, Wednesday, October 26, 2016

Ramakrishna Podila and Apparao Rao at the Clemson Nanomaterials Center, along with graduate students Jingyi Zhu and Anthony Childress, have discovered how to increase by five-fold the energy capacity of supercapacitors without sacrificing strength or durability using specially designed layers of atom-thick carbon sheets called graphene.

For the average person who may use but never see a supercapacitor, Clemson’s work means faster charging times, longer lives, a lighter power source than batteries, reduced dependency on fossil fuels, tons less air pollution and possibly lower energy prices.


Graphene sealed in a pouch with electrolytes makes a flexible supercapacitor.

Image Credit: Ashley Jones / Clemson University

 

In Geneva, Switzerland, supercapacitors power public buses two kilometers from a 15-second charge, and interest in Clemson’s research is building.

“A national research and development enterprise in India is interested in the Clemson supercapacitors and visited the Clemson Nanomaterials Institute twice. Negotiations for manufacturing supercapacitors to power a bus are in progress,” said Rao, the Robert A. Bowen Professor of Physics in the College of Science.

Other potential applications of supercapacitors are far-reaching, from regenerative braking in hybrid and electric vehicles to providing the burst of power needed to adjust the direction of turbine blades in changing wind conditions.

Capacitors, unlike batteries, deliver a lot of power over a very short time. Batteries deliver less power, but they store much more energy. Batteries store energy through a chemical reaction: ions in lithium ion batteries move between negative and positive electrodes.

“While the chemical reactions hold much energy, the ion motion in batteries is rather slow, leading to low power,” said Podila, an assistant professor in physics and astronomy in the College of Science.

Supercapacitors overcome this by storing ions on the surface of nanomaterials electrostatically, like socks sticking to towels coming out of a dryer.

Graphene, the nanomaterial used by the Clemson team, is ultrathin, a million times thinner than a human hair. It’s stronger than steel, flexible and lightweight; a sheet the size of a football field would weigh less than a gram.

“The high-surface area of graphene provides space for ion storage (high-energy) and the ions are always on the surface ready to race (high power),” Podila said. “The problem, however, has been to effectively use the high surface area.”

Often, Podila said, ions can’t access some of the spaces in nanomaterials due to lack of connectivity. Also, the electrons within some nanomaterials may limit the total energy of a supercapacitor through an effect called “quantum capacitance”.

The Clemson team created microscopic layers of graphene with nanometer-sized pores, then sandwiched them together. The pores not only open new channels for ions to access all the spaces in graphene, but they also increase the quantum capacitance.

Creating the pores in specific configurations increased storage capacity 150 percent. Then the researchers introduced two different electrolytes whose ions were smaller than the pores; one by 20 percent, the other by 55 percent.

The effect was like spreading mayo on soft, light, porous bread; the electrolytes oozed into the pores.

“Testing showed the electrolytes with the larger ions did not increase the capacity, but the smaller ions travel through the pores into untapped parts of graphene. The result was a 500 percent increase in capacity,” Zhu said.

Furthermore, the graphene retained its electrical and material properties; the bread, soaked with mayo, didn’t fall apart.

Zhu and Childress also fashioned graphene into thin, flexible electrodes and inserted them into a flexible pouch. They filled the pouch with the electrolyte containing the smaller ions and sealed it, creating a lightweight, flexible supercapacitor that withstood more than 10,000 charge-discharge cycles without any loss in performance.

Source: Clemson

Tags:  Batteries  Clemson  Energy Storage  Graphene  Supercapacitor 

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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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