Advancements in battery technology shaping the future of electronic vehicles


battery_sunx250Scientists at the Canadian Light Source are on the forefront of battery technology using cheaper materials with higher energy and better recharging rates that make them ideal for electric vehicles (EVs).

The switch from conventional internal combustion engines to EVs is well underway. However, limited mileage of current EVs due to the confined energy storage capability of available battery systems is a major reason why these vehicles are not more common on the road.

A group of researchers from the CLS and Western Univ. have made significant strides in addressing the rechargeability and reaction kinetics of sodium-air batteries. They believe understanding sodium-air battery systems and the chemical composition and charging behavior will contribute to manufacturing more road-worthy batteries for EVs.

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Schematic diagram of sodium-air (Na-Air) batteries based on porous carbon electrodes. Image: Canadian Light Source

“Metal-air cells use different chemistry from conventional lithium-ion batteries, making them more suited to compete with gasoline,” said Dr. Xueliang (Andy) Sun, Canada Research Chair from Western’s Dept. of Mechanical and Materials Engineering. “Development of new rechargeable battery systems with higher energy density will increase the EVs mileage and make them more practical for everyday use.

“On the other side, higher energy density battery systems will pave the road for renewable energy sources in order to decrease emissions and climate change consequences,” said Sun.

During their experiments, researchers looked at different “discharge products” from the sodium-air batteries under various physicochemical conditions. Products such as sodium peroxide and sodium superoxide are produced. Understanding these discharge products is critically important to the charging cycle of the battery cell, since various oxides exhibit different charging potentials.

The experiments were conducted using the powerful x-rays of the CLS VLS-PGM beamline.

“We took advantage of the high brightness and high-energy resolution of the photoemission endstation, using a surface sensitive technique to identify the different states of the sodium oxides,” said Dr. Xiaoyu Cui, CLS staff scientist. “We could also monitor the change in the chemical composition of the products by changing the kinetic parameters of the cell. The conclusive data from the CLS helped us confirm our hypothesis.”

According to the researchers, only a few studies have ever addressed sodium-air battery systems, with limited understanding behind the chemistry of the cell. Their work was published in Energy and Environmental Science and the authors believe the findings of the study contribute to better understanding the chemistry behind sodium-air cells which, in turn, will result in improved recharging rates and energy efficiencies.

“Although lots of research has been done to develop rechargeable, high energy metal-air battery cells during the past decade, there is still a long road ahead to achieve a practical high-energy battery system that can meet the demand for our current EVs,” said Sun. “We are working to develop novel materials for different battery systems to increase the energy density and lifecycle.

“Metal-air batteries are less expensive compared with other battery systems such as lithium-ion. Specifically, sodium-air batteries are very cost effective since the materials can easily be supplied from natural resources – sodium and oxygen being among the most abundant elements on earth.”

Source: Canadian Light Source

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Improving Mobile Devices in a Big Way – Using “Small Things” Nanotechnology


1-princeton 163Abstract:
Nanotechnology has recently improved the picture of LED displays on mobile devices by 400 hundred percent.

October 16th, 2014

 

Small Scale Nanotechnology Is Improving Mobile Devices in a Big Way

The mastermind behind this improvement is Stephen Chou, an electrical engineering professor at Princeton University, who has been making waves in the nanotechnology industry as of late. Here are just a few reasons why nanotechnology is important.

It’s Changing the Rules
Chou is deeply involved in everything regarding nanotechnology. He is the head of a group called NanoStructure Laboratory (NSL) at Princeton and is a pioneer, world leader and inventor. He has set out to develop new nanotechnologies to improve today’s electronics, optics, optoelectronics, biology and magnetics by making them smaller, better and more affordable. Not only has his group improved picture quality in LED devices, it also improved the brightness and efficiency by 57 percent, according to Princeton University. Chou and his group were able to accomplish this by manipulating light on a scale smaller than one wavelength, a technique which Chou describes as changing the rules on the ways light is manipulated.

LED is more favorable than traditional light such as incandescent and fluorescent because it lasts longer, is more efficient and more compact. Chou explains that an LED device can trap much of the light inside its structure, which makes them a design challenge, and light extraction is the holy grail of LED lighting.

1-princeton 163

However, Chou and his group managed to find an alternative route, which helps to get away from the use of metal reflectors, lenses and light-absorbing materials that reduce its brightness and efficiency by half. NSL created a nanotech structure called plasmonic cavity with sub wavelength hole-array, or PlaCSH. One of the best features of this new technology is that power consumption will be reduced, thus both an LED device’s displays and its battery life will improve.

Nanotechnology With Today’s Phones
Chou’s resume is impressive. He is the inventor of (LISA), which is a process where a mask is used to control the formation of micro and nano structures in a thin polymer film. His LISA technique has helped advance organic electronic and opto-electronics devices. He also sports a long list of inventions within the nanomagnetic and nanoelectronics field that have put transistors in computer chips on a nanoscale that are much faster, more compact and cheaper to produce than traditional methods.

His recent work is just another example of how nanotechnology is improving our devices for both efficiency, features and style. Today’s iPhones will be seeing such nanotech features such as scratch-proof and waterproof coatings and chargers that can completely charge mobile devices in under a minute.

Mobile devices that include nanotechnology will see brighter images, enjoy wider viewing angles and feel lighter than what they are. They also will have better picture quality and a longer battery life. Chou’s nanotechnology breakthroughs extend over a broad range of consumer products, materials and equipment, but the mobile device market has seen dramatic improvement and will continue to do so as more and more mobile devices incorporate nanotechnology.

 

Controlling Nano-Energy Flows to Make Mobile Devices Last Longer


1-nano devices howtomakemobElectronic devices waste a lot of energy by producing useless heat. This is one of the main reasons our mobiles use up battery power so quickly. Researchers at University of Luxembourg have made a leap forward in understanding how this happens and how this waste could be reduced by controlling energy flows at a molecular level. This would make our technology cheaper to run and more durable.

Until now, scientists had just an average view of energy conversion efficiency in nano-devices. For the first time, a more complete picture has been described thanks to University of Luxembourg research. “We discovered universal properties about the way energy efficiency of nano-systems fluctuates,” explained Prof. Massimiliano Esposito of Luxembourg University’s Physics and Materials research unit. Using this knowledge it will be possible to control energy flows more accurately, so cutting waste.

These energy controls could be achieved by a technological regulator which would prevent the natural process whereby heat generated in one part of a device is lost as it spreads to cooler areas. In other words, this adds interesting nuances to the Second Law of Thermodynamics, one of the fundamental theories in physics. This theoretical understanding of how to regulate of energy flows brings to life “Maxwell’s demon”, a notion introduced by the major 19th Century mathematician and physicist James Clerk Maxwell. He imagined that this “demon” could overturn the laws of nature by allowing cold particles to flow towards hot areas.

Two recent papers published in highly respected scientific journals (Physical Review X and Nature Communications) describe these findings. The research team under Prof. Esposito used mathematical models to arrive at these conclusions. These ideas will be put into practice in the laboratory before any eventual practical technological applications are developed.

Explore further: Scientists produce a novel form of artificial graphene

Stanford’s GCEP awards $10.5 million for Research on Renewable Energy


 

Nano fuel cells c2cs35307e-f1The Global Climate and Energy Project (GCEP) at Stanford University has awarded $10.5 million for seven research projects designed to advance a broad range of renewable energy technologies. The funding will be shared by six Stanford research teams and an international group from the United States and Europe.

“The seven projects funded by GCEP could spark discoveries that lead to dramatic improvements in energy storage, solar cells and renewable biofuels,” said GCEP Director Sally Benson, a professor of energy resources engineering at Stanford. “I’m delighted to add that many of the scientists who received funding for these innovative projects will be featured speakers at our 2014 GCEP Research Symposium in October.”

The seven awards bring the total number of GCEP-supported research programs to 117 since the project’s launch in 2002. In total, GCEP has awarded approximately $161 million to researchers at Stanford and 40 other institutions worldwide.

“These awards demonstrate GCEP’s continued commitment to advancing cutting- edge research in energy,” said GCEP management committee member Steven Freilich, director of materials science at DuPont Central Research & Development. “As a science company, DuPont believes that collaboration enhances our power to innovate. Programs like GCEP help build the great working relationships between scientists and engineers at universities, companies and government institutions that are required to develop innovative solutions for people everywhere.”

The following Stanford faculty members received funding for advanced research on photovoltaics, battery technologies and new catalysts for sustainable fuels:

Self-healing polymers for high energy density lithium-ion batteries. The goal is to develop high-energy, durable lithium-ion batteries for electric vehicles by improving the cycle life of the battery electrodes. Researchers will design self-healing polymers that can stretch to accommodate large volume changes in the battery during charge and discharge. Investigators: Zhenan Bao, Chemical Engineering; Yi Cui, Materials Science and Engineering.Battery Secret untitled

Photo-electrochemically rechargeable zinc-air batteries. The zinc-air battery is a promising technology that has high energy density but limited power density. The research team will develop a photo-electrochemical battery with a stable zinc electrode capable of generating electricity using sunlight and air. Investigator: Hongjie Dai, Chemistry.

Novel inorganic-organic perovskites for photovoltaics. The mineral perovskite is a promising, low-cost material for enhancing the efficiency of silicon solar cells. The goal of this project is to develop a hybrid perovskite-silicon solar cell that significantly improves the light-to-energy conversion efficiency of conventional cells. Investigators: Michael McGehee, Materials Science and Engineering; Hemamala Karunadasa, Chemistry.

ElectrodeBarrierLight trapping in high‐efficiency, low‐cost silicon solar cells. This work aims to develop a new technique for trapping sunlight in thin-film silicon solar cells. Silicon and other materials will be engineered into nanosize spheres, domes and wires that promote light absorption and improve the overall efficiency of the solar cell. Investigator: Mark Brongersma, Materials Science and Engineering.

Maximizing solar-to-fuel conversion efficiency in photo-electrochemical cells. The goal is to create an efficient, stable photo-electrochemical cell capable of converting sunlight into hydrogen and other renewable fuels at elevated temperatures of 500°C to 700°C. Investigators: William Chueh and Nick Melosh, Materials Science and Engineering.

Electrochemical conversion of carbon gases to sustainable fuels and chemicals. Researchers will use computational analysis and experimental techniques to develop new catalysts that convert carbon dioxide and carbon monoxide into renewable fuels and chemicals. Investigators: Thomas Jaramillo, Chemical Engineering; Jens Nørskov, Chemical Engineering and SLAC National Accelerator Laboratory; Anders Nilsson, SLAC.

A team of scientists from the United States, Belgium and Scotland also received support for research that could lead to the large-scale conversion of cellulosic plants to biofuels:

Optimizing yield and composition in lignin‐modified plants. The inability to process lignin, a cement-like component of plant cell walls, has been a major hurdle in the production of biofuels from switchgrass and other cellulosic plants. In a previous GCEP study, the research team genetically engineered plants with reduced lignin that were smaller than normal. This project seeks to develop larger lignin-modified plants that can be cultivated for biofuels at scale. Investigators: Clint Chapple, Purdue University; Wout Boerjan, VIB and University of Ghent (Belgium); John Ralph, University of Wisconsin-Madison; Xu Li, North Carolina State University; Claire Halpin and Gordon Simpson, University of Dundee (Scotland).

GCEP is an industry partnership that supports innovative research on energy technologies that address the challenge of global climate change by reducing greenhouse gas emissions. Based at Stanford, the project includes five corporate sponsors – ExxonMobil, GE, Schlumberger, DuPont and Bank of America.

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For more information visit http://gcep.stanford.edu.

This article was written by Mark Shwartz, Precourt Institute for Energy, Stanford University.

The World Of Tomorrow: Nanotechnology: Interview with PhD and Attorney D.M. Vernon


Bricks and Mortar chemistsdemoThe Editor interviews Deborah M. VernonPhD, Partner in McCarter & English, LLP’s Boston office.

 

 

 

Why It Matters –

” … I would say the two most interesting areas in the last year or two have been in 3-D printing and nanotechnology. 3-D printing is an additive technology in which one is able to make a three-dimensional product, such as a screw, by adding material rather than using a traditional reduction process, like a CNC (milling) process or a grinding-away process.

The other interesting area has been nanotechnology. Nanotechnology is the science of materials and structures that have a dimension in the nanometer range (1-1,000 nm) – that is, on the atomic or molecular scale. A fascinating aspect of nanomaterials is that they can have vastly different material properties (e.g., chemical, electrical, mechanical properties) than their larger-scale counterparts. As a result, these materials can be used in applications where their larger-scale counterparts have traditionally not been utilized.”

nanotech

Editor: Deborah, please tell us about the specific practice areas of intellectual property in which you participate.

 

 

Vernon: My practice has been directed to helping clients assess, build, maintain and enforce their intellectual property, especially in the technology areas of material science, analytical chemistry and mechanical engineering. Prior to entering the practice of law, I studied mechanical engineering as an undergraduate and I obtained a PhD in material science engineering, where I focused on creating composite materials with improved mechanical properties.

Editor: Please describe some of the new areas of biological and chemical research into which your practice takes you, such as nanotechnology, three-dimensional printing technology, and other areas.

Vernon: I would say the two most interesting areas in the last year or two have been in 3-D printing and nanotechnology. 3-D printing is an additive technology in which one is able to make a three-dimensional product, such as a screw, by adding material rather than using a traditional reduction process, like a CNC (milling) process or a grinding-away process. The other interesting area has been nanotechnology. Nanotechnology is the science of materials and structures that have a dimension in the nanometer range (1-1,000 nm) – that is, on the atomic or molecular scale.

A fascinating aspect of nanomaterials is that they can have vastly different material properties (e.g., chemical, electrical, mechanical properties) than their larger-scale counterparts. As a result, these materials can be used in applications where their larger-scale counterparts have traditionally not been utilized.

Organ on a chip organx250

I was fortunate to work in the nanotech field in graduate school. During this time, I investigated and developed methods for forming ceramic composites, which maintain a nanoscale grain size even after sintering. Sintering is the process used to form fully dense ceramic materials. The problem with sintering is that it adds energy to a system, resulting in grain growth of the ceramic materials. In order to maintain the advantageous properties of the nanosized grains, I worked on methods that pinned the ceramic grain boundaries to reduce growth during sintering.

The methods I developed not only involved handling of nanosized ceramic particles, but also the deposition of nanofilms into a porous ceramic material to create nanocomposites. I have been able to apply this experience in my IP practice to assist clients in obtaining and assessing IP in the areas of nanolaminates and coatings, nanosized particles and nanostructures, such as carbon nanotubes, nano fluidic devices, which are very small devices which transport fluids, and 3D structures formed from nanomaterials, such as woven nanofibers.

Editor: I understand that some of the components of the new Boeing 787 are examples of nanotechnology.

Vernon: The design objective behind the 787 is that lighter, better-performing materials will reduce the weight of the aircraft, resulting in longer possible flight times and decreased operating costs. Boeing reports that approximately 50 percent of the materials in the 787 are composite materials, and that nanotechnology will play an important role in achieving and exceeding the design objective. (See, http://www.nasc.com/nanometa/Plenary%20Talk%20Chong.pdf).

While it is believed that nanocomposite materials are used in the fuselage of the 787, Boeing is investigating applying nanotechnology to reduce costs and increase performance not only in fuselage and aircraft structures, but also within energy, sensor and system controls of the aircraft.

Editor: What products have incorporated nanotechnology? What products are anticipated to incorporate its processes in the future?

Vernon: The products that people are the most familiar with are cosmetic products, such as hair products for thinning hair that deliver nutrients deep into the scalp, and sunscreen, which includes nanosized titanium dioxide and zinc oxide to eliminate the white, pasty look of sunscreens. Sports products, such as fishing rods and tennis rackets, have incorporated a composite of carbon fiber and silica nanoparticles to add strength. Nano products are used in paints and coatings to prevent algae and corrosion on the hulls of boats and to help reduce mold and kill bacteria. We’re seeing nanotechnology used in filters to separate chemicals and in water filtration.

The textile industry has also started to use nano coatings to repel water and make fabrics flame resistant. The medical imaging industry is starting to use nanoparticles to tag certain areas of the body, allowing for enhanced MRI imaging. Developing areas include drug delivery, disease detection and therapeutics for oncology. Obviously, those are definitely in the future, but it is the direction of scientific thinking.

Editor: What liabilities can product manufacturers incur who are incorporating nanotechnology into their products? What kinds of health and safety risks are incurred in their manufacture or consumption?Nano Body II 43a262816377a448922f9811e069be13

Vernon: There are three different areas that we should think about: the manufacturing process, consumer use and environmental issues. In manufacturing there are potential safety issues with respect to the incorporation or delivery of nanomaterials. For example, inhalation of nanoparticles can cause serious respiratory issues, and contact of some nanoparticles with the skin or eyes may result in irritation. In terms of consumer use, nanomaterials may have different material properties from their larger counterparts.

As a result, we are not quite sure how these materials will affect the human body insofar as they might have a higher toxicity level than in their larger counterparts. With respect to an environmental impact, waste or recycled products may lead to the release of nanoparticles into bodies of water or impact wildlife. The National Institute for Occupational Safety and Health has established the Nanotechnology Research Center to develop a strategic direction with respect to occupational safety and nanotechnology. Guidance and publications can be found at http://www.cdc.gov/niosh/topics/nanotech.

Editor: The European Union requires the labeling of foods containing nanomaterials. What has been the position of the Food & Drug Administration and the EPA in the United States about food labeling?

Vernon: So far the FDA has taken the position that just because nanomaterials are smaller, they are not materially different from their larger counterparts, and therefore there have been no labeling requirements on food products. The FDA believes that their current standards for safety assessment are robust and flexible enough to handle a variety of different materials. That being said, the FDA has issued some guidelines for the food and cosmetic industries, but there has not been any requirement for food labeling as of now. The EPA has a nanotechnology division, which is also studying nanomaterials and their impact, but I haven’t seen anything that specifically requires a special registration process for nanomaterials.

Editor: What new regulations regarding nanotech products are expected? Should governmental regulations be adopted to prevent nanoparticles in foods and cosmetics from causing toxicity?

Vernon: The FDA has not telegraphed that any new regulations will be put into place. The agency is currently in the data collection stage to make sure that these materials are being safely delivered to people using current FDA standards – that materials are safe for human consumption or contact with humans. We won’t really understand whether or not regulations will be coming into place until we see data coming out that indicates that there are issues that are directly associated with nanomaterials. Rather than expecting regulations, I would suggest that we examine the data regarding nano products to optimize safe handling and use procedures.

Editor: Have there ever been any cases involving toxicity resulting from nano products?

Vernon: There are current investigations about the toxicity of carbon nano tubes, but the research is in its infancy. There is no evidence to show any potential harm from this technology. Unlike asbestos or silica exposure, the science is not there yet to demonstrate any toxicity link. The general understanding is that it may take decades for any potential harm to manifest. I believe my colleague, Patrick J. Comerford, head of McCarter’s product liability team in Boston, summarizes the situation well by noting that “if any supportable science was available, plaintiff’s bar would have already made this a high-profile target.”

Editor: While some biotech cases have failed the test of patentability before the courts, such as the case of Mayo v. Prometheus, what standard has been set forth for a biotech process to pass the test for patentability?

Vernon: There is no specified bright-line test for determining if a biotech process is patentable. But what the U.S. Patent and Trademark Office has done is to issue some new examination guidelines with respect to the Mayo decision that help examiners figure out whether a biotech process is patent eligible. Specifically, the guidelines look to see if the biotech process (i.e., a process incorporating a law of nature) also includes at least one additional element or step. That additional element needs to be significant and not just a mental or correlation step. If a biotech process patent claim includes this significant additional step, there still needs to be a determination if the process is novel and non-obvious over the prior art. So while this might not be a bright-line test to help us figure out whether a biotech process is patentable, it at least gives us some direction about what the examiners are looking for in the patent claims.

Editor: What effect do you think the new America Invents Act will have in encouraging biotech companies to file early in the first stages of product development? Might that not run the risk that the courts could deny patentability as in the Ariad case where functional results of a process were described rather than the specific invention?

Vernon: The AIA goes into effect next month. What companies, especially biotech companies, need to do is file early. Companies need to submit applications supported by their research to include both a written description and enablement of the invention. Companies will need to be more focused on making sure that they are not only inventing in a timely manner but are also involving their patent counsel in planned and well-thought-out experiments to make sure that the supporting information is available in a timely fashion for patenting.

Editor: Have there been any recent cases relating to biotechnology or nanotechnology that our readers should be informed about?

Vernon: The Supreme Court will hear oral arguments in April in the Myriad case. This case involves the BRCA gene, the breast cancer gene – and the issue is whether isolating a portion of a gene is patentable. While I am not a biotechnologist, I think this case will also impact nanotechnology as a whole. Applying for a patent on a portion of a gene is not too far distant from applying for a patent on a nanoparticle of a material that already exists but which has different properties from the original, larger-counterpart material. Would this nanosize material be patentable? This will be an important case to see what guidance the Supreme Court delivers this coming term.

Editor: Is there anything else you’d like to add?

Vernon: I think the next couple of years for nanotech will be very interesting. As I mentioned, I did my PhD thesis in the nanotechnology area a few years ago. My studies, like those of many other students, were funded in part with government grants. There is a great deal of government money being poured into nanotechnology. In the next ten years we will start seeing more and more of this research being commercialized and adopted into our lives. To keep current of developments, readers can visit www.nano.gov.

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Graphene May be KEY to Leap in Supercapacitor Performance


graphene_cover_orange_highresAbstract: By Dr Peter Harrop, Chairman, IDTechEx

Graphene electrodes are one of the best prospects for enabling supercapacitors and superbatteries to take up to half of the lithium-ion battery market in 15 years – amounting to tens of billions of dollars yearly.

They may also be key to supercapacitors taking much of the multibillion dollar aluminium electrolytic capacitor business. That would make supercapacitors and supercabatteries (notably in the form of lithium-ion capacitors) one of the largest applications for graphene.

Cambridge, UK | Posted on August 20th, 2014

Heirarchical to exohedral?

Today’s supercapacitor electrodes usually have hierarchical electrode structures with large pores progressing to small pores letting appropriate electrolyte ions into monolithic masses of carbon. In research, this is often giving way to better results from exohedral structures – where the large functional area is created by allotropes of carbon often only one atom thick. Examples are graphene, carbon nanotubes and nano-onions (spheres within spheres). Add to that the newer aerogels with uniform particles a few nanometers across.

It is not simply an area game. The exohedral structure must also be optimally matched to the electrolyte, then the pair assessed not just for specific capacitance (capacitance density) but voltage increase, because that also increases the commercially-important energy density when competing with batteries.

Nothing guaranteed

It is not a done deal. Graphene is expensive when good purity and structural integrity are required. Exohedral structures like graphene, with the greatest theoretical area, tend to improve gravimetric but not volumetric energy density. Poor volumetric energy density will cut off many applications unless structural supercapacitors prove feasible. Here the supercapacitor would replace dumb structures like car bodies, taking effectively no volume, regardless of measured volumetric energy density. Some of these formulations increase the already superb power density but that is not very exciting commercially.

piezoelectric-graphene

Other parameters matter

Of course cost, stability, temperature performance and many other parameters must also be appropriate in all potential applications of graphene in supercapacitors and supercabatteries. Indeed for replacing electrolytic capacitors, working at 120Hz is key. In other applications, increased power density may be valuable when combined with other improvements. Nevertheless, energy density improvement is the big one for sharply increasing the addressable market – probably around 2025 or later.

Highest energy density by leveraging new generation electrolytes

Graphene gives some of the highest energy densities in the laboratory and it is particularly effective in exhibiting high specific capacitance with the new electrolytes. That means aqueous electrolytes with desirably low cost and non-flammability, and ionic electrolytes with desirably simplified manufacturing, high voltage, non-flammability, low toxicity and now exceptional temperature range.

Ionic graphene

With ionic electrolytes, graphene works despite the high viscosity that makes them ineffective in hierarchical electrode structures. On the other hand, graphene does not exhibit good specific capacitance with the old acetonitrile and propylene carbonate organic solvent electrolytes. It is advantageous that there is no solvent or solute with ionic electrolytes, though sometimes they are added to tailor the ionic supercapacitor to obtain certain performance in experiments.

Aqueous graphene

With aqueous electrolytes, graphene’s accessible area is large and this offsets the low voltage to give good energy density in some experiments. Curved graphene is often used. Under a microscope it looks like crushed paper so further optimisation is possible. In the laboratory, the energy density of lead-acid and nickel cadmium batteries and even lithium-ion batteries has been achieved with various formulations involving graphene so it is likely that one of them will prove commercial in due course.

Supercabattery graphene

Recent developments by industrial companies demonstrate that graphene lithium-ion capacitor supercabattery systems can operate up to 3.7 V. They have a very good cycle life and excellent power performance.

AC graphene supercapacitors

Potentially, inverters in electric vehicles can be made smaller, lighter and have lower installed cost thanks to planned graphene supercapacitors replacing their large aluminium electrolytic capacitors. So far, it is only with vertically stacked graphene that the necessary time constant of 200 microseconds has been demonstrated suitable for such 120Hz filtering.

For more see the brand new IDTechEx report Functional Materials for Supercapacitors / Ultracapacitors / EDLC 2015-2025 and also Graphene Markets, Technologies and Opportunities 2014-2024. In addition, attend IDTechEx’s events Supercapacitors LIVE! USA 2014 and Graphene & 2D Materials LIVE! USA 2014 taking place in November.

Simpler process to grow germanium nanowires could improve lithium ion batteries


Nanowires simplerproceResearchers at Missouri University of Science and Technology have developed what they call “a simple, one-step method” to grow nanowires of germanium from an aqueous solution. Their process could make it more feasible to use germanium in lithium ion batteries.

 

The Missouri S&T researchers describe their method in “Electrodeposited Germanium Nanowires,” a paper published today (Thursday, Aug. 28, 2014) on the website of the journal ACS Nano. Their one-step approach could lead to a simpler, less expensive way to grow .

As a semiconductor material, germanium is superior to silicon, says Dr. Jay A. Switzer, the Donald L. Castleman/Foundation for Chemical Research Professor of Discover at Missouri S&T. Germanium was even used in the first transistors. But it is more expensive to process for widespread use in batteries, solar cells, transistors and other applications, says Switzer, who is the lead researcher on the project.

Nanowires simplerproce

Switzer and his team have had success growing other materials at the nanometer scale through electrodeposition – a process that Switzer likens to “growing rock candy crystals on a string.” For example, in a 2009 Chemistry of Materials paper, Switzer and his team reported that they had grown zinc oxide “nanospears” – each hundreds of times smaller than the width of a human hair – on a single-crystal silicon wafer placed in a beaker filled with an alkaline solution saturated with zinc ions.

But growing germanium at the nano level is not so simple. In fact, electrodeposition in an such as that used to grow the zinc oxide nanospears “is thermodynamically not feasible,” Switzer and his team explain in their ACS Nano paper, “Electrodeposited Germanium Nanowires.”

So the Missouri S&T researchers took a different approach. They modified an electrodeposition process found to produce germanium nanowires using liquid metal electrodes. That process, developed by University of Michigan researchers led by Dr. Stephen Maldonado and known as the electrochemical liquid-liquid-solid process (ec-LLS), involves the use of a metallic liquid that performs two functions: It acts as an electrode to cause the electrodeposition as well as a solvent to recrystallize nanoparticles.

Switzer and his team applied the ec-LLS process by electrochemically reducing indium-tin oxide (ITO) to produce indium nanoparticles in a solution containing germanium dioxide, or Ge(IV). “The indium nanoparticle in contact with the ITO acts as the electrode for the reduction of Ge(IV) and also dissolves the reduced Ge into the particle,” the Missouri S&T team reports in the ACS Nano paper. The germanium then “starts to crystallize out of the nanoparticle allowing the growth of the nanowire.”

The Missouri S&T researchers tested the effect of temperature for electrodeposition by growing the germanium nanowires at room temperature and at 95 degrees Celsius (203 degrees Fahrenheit). They found no significant difference in the quality of the nanowires, although the nanowires grown at room temperature had smaller diameters. Switzer believes that the ability to produce the nanowires at through this one-step process could lead to a less expensive way to produce the material.

“The high conductivity (of germanium nanowires) makes them ideal for applications,” Switzer says.

Explore further: Growing thin films of germanium

More information: “Electrodeposited Germanium Nanowires.” Naveen K. Mahenderkar, Ying-Chau Liu, Jakub A. Koza, and Jay A. Switzer. ACS Nano Article ASAP DOI: 10.1021/nn503784d Tilted