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New Battery Technology Could Provide Large-Scale Energy Storage for the Grid

I, like many others, have been following the work being done by Yi Cui at Stanford University in improving battery technology.

Cui’s work has often aimed at improving Li-ion battery technology, much in the same way researchers at Northwestern University recently have done in getting a silicon-graphene sandwich to act as a more effective anode.

But in his most recent research he has abandoned the use of lithium ions and replaced them with either sodium or potassium ions for his new battery technology.

The result is a battery that Cui and his colleagues claim is able to retain 83% of its charge after 40,000 cycles, which compares more than favorably to Li-ion batteries of 1,000 cycles.

The researchers have been able to develop a cathode material that they can essentially mix in a flask by combining iron with cyanide and then replacing half of the iron with copper then making crystalline nanoparticles from the compound.

There is a weight penalty with this battery technology, which means that it will not be likely powering any laptops or electric vehicles. However, it may be the perfect fit for large-scale energy storage on the electrical grid.

"At a rate of several cycles per day, this electrode would have a good 30 years of useful life on the electrical grid," said Colin Wessells, a graduate student in materials science and engineering who is the lead author of a paper describing the research, published this week in Nature Communications.

"That is a breakthrough in performance – a battery that will keep running for tens of thousands of cycles and never fail," said Cui, who in this case is Wessell's adviser and a coauthor of the paper.

But all is not resolved as of yet. While the researchers have developed this ‘new chemistry’ for the battery, they only have the high-power cathode at this point, so they still need to develop an anode.

Nonetheless the researchers are confident they will develop a material for the anode. If they manage to get that sorted, they may have developed an economical battery for storing energy from solar and wind power so as to avoid sharp drop offs in electricity in the grid.

Silicon-Graphene Sandwich Creates Li-ion Batteries with Ten Times Longer Charge Life

When the media made a big noise about the concept of a flexible phone that was being considered by Nokia and Cambridge University back in 2008, aptly called the Morph, I asked who needs a phone that wraps around my wrist when what I really want is one that can last a decent amount of time before needing to be recharged.

Since then there has been a fair amount of research attempting to improve the venerable lithium-ion (Li-ion) battery.

The latest comes from researchers at Northwestern University, led by Harold H. Kung, who have developed a method  for sandwiching silicon between graphene sheets in the anode of the battery to allow for greater number of lithium atoms in the electrode.

Silicon has been experimented with for replacing the carbon in the anode of Li-ion batteries since they allow more Lithium atoms to be stored per atom of silicon than that of carbon (four lithium atoms for every silicon atom compared to one lithium atom for every six carbon atoms). However, silicon expands and contracts so much during the charging process that it soon loses its charge capacity.

“Now we almost have the best of both worlds,” Kung said. “We have much higher energy density because of the silicon, and the sandwiching reduces the capacity loss caused by the silicon expanding and contracting. Even if the silicon clusters break up, the silicon won’t be lost.”

Kung and his team also came up with a chemical oxidation process to create nanometer scale holes in the graphene sheets so that lithium ions can find a shortcut through the graphene in the anode, which could quicken the charging times by a factor of 10.

The research, which was published in the Wiley journal Advanced Energy Materials,  expects to build on this initial work that was focused on the anode and move to the cathode.

New Sorting Process for Carbon Nanotubes Prepares Them for Flexible Electronics

Researchers attempting to use carbon nanotubes (CNTs) in electronics have faced many obstacles, but perhaps the two most fundamental problems have been: putting them where you want them to go and developing a process that promises a homogeneity of CNTs.

Researchers at the University of California Davis and Stanford University, led by Zhenan Bao, who has been using CNTs for creating pressure sensors for use in an artificial skin, along with the Samsung Advanced Institute of Technology have developed a process by which the semiconducting single-walled carbon nanotubes are separated out from a mixture.

The researchers published their work in the journal Nature Communications.

"Sorting has been a major bottleneck for carbon nanotubes to be viable for practical electronics applications," Bao said. "This work solves the problem of separating the conducting from the semiconducting nanotubes."

The problem has been the conducting variety of CNTs and the semiconducting species have quite different application areas where they excel. This separation process could mean that the semiconducting CNTs can be sorted out and used for transistors and the conducting nanotubes can be used for wires and electrodes.

The method the researchers developed for carrying out this separation involves a polymer that wraps itself around the semiconduting and non-conducting CNTs. While researchers have developed polymers in the past that accomplish this, the problem with those polymers was that they insulated the CNTs and required extensive removal treatments to get the polymer off the CNTs.

This polymer does not need to be removed since it can be used as is as a semiconducting nanotube and polymer ink for use in printable electronics.

It is clear that Bao intends to use the semiconducing nanotube product for her work in flexible electronics.

"I'm especially happy that this polymer can now be used to sort nanotubes," Bao said. "It merges two very important materials together and makes a hybrid material that could be very useful for printed and flexible electronics."

Now that 3D Chips Are Here, What Does the Next Generation Hold?

Now that Intel will definitely be introducing its 22-nm Tri-Gate transistor—referred to as a 3-D chip due its 3-D ridge (or fin, thus the alternative name, FinFET) in which electrons runs through—it seems the era of 3-D chips are here sooner than expected. (Read and watch this interesting interview with Intel Senior Fellow Mark Bohr on how we got to this point.)

With this as its context, Dutch researchers from MESA+ Institute at the University of Twente, University of Eindhoven, ASML company and TNO Institute have developed processes by which they can rapidly fabricate “large 3-D photonic in mono-crystalline silicon using CMOS compatible processes”  that should enable novel fabrication methods for computer chips.

The researchers have published their work in a series of three papers and in the one published by the Journal of Vacuum Science and Technology have been able to fabricate a 3-D nanostructure in silicon by making etch marks on two sides of s wafer.

"There are many advantages of our fabrication route" says Willem Tjerkstra, a researcher at the MESA+ Institute in an interview with Nanowerk. "A complex 3-D structure can be made in only two etching steps, instead of tediously making such a structure by stacking layer-by-layer, as in standard CMOS-compatible fabrication. In our paper, we propose that our method allows the realization of 3-D computer chips that have more functional units concentrated on the same area. We also predict the realization of chips on different sides of liquid channels for microfluidic, or for cooling purposes."

In the two succeeding papers, the researchers described a “3D etch-masking method to realize a complex 3-D periodic array (a crystal structure) of pores in silicon” and then in the third paper observed for the first time the long-predicted phenomenon of the spontaneous emission of light from quantum dots in a 3-D photonic band gap.

It will be interesting to see if techniques such as these find their way into the next generation of 3-D chips when dimensions go down to 14nm and then 10nm.

Aircraft Nanocomposites that Provide Early Warning System for Structural Failures

Nanotechnology is already having an impact on air travel, as evidenced by EasyJet’s testing of a nanocoating that will reduce wind drag and fuel consumption.

But if current research into new adhesives based on nanomaterials proves effective, the future of aircraft manufacturing could be altered significantly beyond just coatings and into the actual structures of the aircraft.

Researchers at the University of Toronto are looking into the use of multifunctional nanocomposites and adhesives that would be used in joining techniques for primary flight load structures and serve a double purpose of providing an early warning system for stresses on these structures and possible future failures.

This line of research builds on the already developing practice of using composites and adhesive bonding in the place of mechanical fastening or welding, such as with the new Airbus A380.

The University of Toronto researchers are working with carbon nanotubes to develop their multifunctional adhesives (smart adhesives) due to their electrical conductivity.

Earlier this year, I covered research coming out of MIT that would use carbon nanotubes in a method for detecting internal damage to composites.

In the MIT research, an electrical current would be applied to the composites that would heat up the carbon nanotubes and allow the use of thermographic camera for detecting flaws without the cumbersome need for heating the entire surface of the aircraft. 

The Canadian researchers are attempting something a bit more ambitious in that the method "employs a novel network recognition approach to determine current continuity and critical percolation level."

Can Nanomaterials Bring Down the Costs of Polymer Solar Cells?

Last week when I criticized the New York Times’ Paul Krugman for emphasizing big-oil conspiracies rather than looking at the material science obstacles to solar power, I remarked that the issue for photovoltaics was not overcoming plots by oil companies but instead developing a material that can be produced cheaply and still produce high conversion rates.

Professor Richard Jones has addressed this issue in a new post over at Soft Machines. Jones examines the technical and economic issues in getting polymer solar cells to compete with everything from fossil fuels to nuclear energy and makes it clear that solving the technical issues can resolve the economic ones as well.

Jones uses as his embarkation point a paper authored by Brian Azzopardi from Manchester University in the journal Energy & Environmental Science entitled “Economic assessment of solar electricity production from organic-based photovoltaic modules in a domestic environment”.

According to Jones, Azzopardi reveals in the paper that “the so-called “levelised power cost” – i.e. the cost per unit of electricity, including all capital costs, averaged over the lifetime of the plant, comes in between €0.19 and €0.50 per kWh for 7% efficient solar cells with a lifetime of 5 years, assuming southern European sunshine.”

This is clearly more expensive than both fossil fuels and nuclear and is even short of conventional solar.

So, how is the gap to be closed? Not surprisingly the majority of the cost of the a photovoltaic system based on polymer solar cells comes from the modules, and the main cost of the modules stems from the cost of the materials, which account for anywhere between 60-80% of the modules.

One thing we can quickly see from numbers like this is that we need to find some cheaper materials and as Jones points out a good place to start is with the transparent conducting electrodes, which currently use a thin layer of indium tin oxide (ITO) and represents half of the material costs.

As we know, ITO is rare and expensive and is going to become more so as time goes on. The nanomaterials we have been looking at for providing both transparency and conductivity, like carbon nanotubes and graphene, have not presented any clear solutions as of yet. Jones does provide us with a useful link that provides us with a good summary of nanomaterial contenders for replacing ITO.

But the message is clear: We still have some technological obstacles to overcome to make the economics of polymer solar cells--and, by extension, photovoltaics in general--compete favorably with fossil fuels, no matter what conspiracy you want to blame on the lack of a wider adoption of solar.

Carbon Nanotubes and Graphene: Rival Rock Stars?

The best summation I’ve seen of a recent article that states that graphene has achieved a “rock star” status was a Tweet from Cientifica: “Graphene is Elvis & Nanotubes are Carl Perkins?”

That sounds about right. And as I recall Carl Perkins wrote and first recorded “Blue Suede Shoes” that Elvis eventually made into such a hit. Playing second fiddle to the younger upstart seems about how the relationship between carbon nanotubes and graphene is developing.

There seems to be an informed opinion out there that graphene is never going to go anywhere in electronics because of its lacking a band gap. But I am not so easily swayed by this line of argument because companies like IBM are investing so much time and effort in developing the material for electronics.

That said, it might be more likely that graphene will find its first applications outside of electronics, not unlike carbon nanotubes, which is still struggling to make an impact in electronics.

In fact, this is the point made by one of the Cornell University researchers who is cited in the initial article linked to at the top of this page.

"People often focus on the electronic applications of graphene, and they don't really think as much of its mechanical applications," said Robert A. Barton, graduate student and lead author of an American Vacuum Society online review article, Sept. 9, about graphene's present and future.

As rival rock stars go, it should be interesting to see how the relationship between the two stars of carbon nanotubes and graphene plays out over time.
 

Thermoelectric Materials Turn to Nanotechnology

After yesterday’s post  in which once again I tried pulling someone back down to earth from the nanotechnology/photovoltaic ethereal heights, I am pleased to blog on research that proves once again that when it comes to nanotech and energy, it’s the mundane that’s interesting.

Thermoelectric materials have been a tantalizing possibility for exploiting all the energy that is lost in waste heat. With their ability to generate an electrical charge simply from temperature differences, it boggles the imagination how much electricity could be generated with these materials.

Researchers at the University of Oslo in Norway cooperation with SINTEF (the Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology) are looking towards nanotechnology to provide an environmentally friendly and more efficient method to produce thermoelectric materials to generate electricity.

The thermoelectric materials that are currently in use employ the elements Lead and Tellurium, but both of which are toxic. In addition to being toxic, the thermoelectric materials are only able to recover 10% of the energy that is loss as waste heat.

But, according to Ole Martin Løvvik, who is both an associate professor in the Department of Physics at the University of Oslo and a senior scientist at SINTEF, nanotechnology could provide both an environmentally friendly alternative and improve its ability to recover energy by 50%.

"I think we will manage to solve this problem with nanotechnology. The technology is simple and flexible and is almost too good to be true. In the long run, the technology can utilise all heat sources, such as solar energy and geothermal energy. The only limits are in our imagination," Løvvik is quoted as saying in the research magazine Apollon at the University of Oslo.

First applications for their solution have already been targeted at automobiles and the researchers are already in discussion with the US car manufacturer General Motors on the technology.

"Modern cars need a lot of electricity. By covering the exhaust system with thermoelectric plates, the heat from the exhaust system can increase the car's efficiency by almost ten per cent at a single stroke,” says Løvvik. “If we succeed, this will be a revolution in the modern automotive industry."

The researchers’ method for balancing between the need for thermoelectric materials to have both high thermal resistance and high current flow is to grind down semi-conductor materials into nano-sized particles by freezing them to minus196 degrees. After breaking the semi-conductor material into nanoparticles they are glued back together, which results in a material that can reflect the heat waves but not reflect the current.

Conspiracy Theories Immaterial to Nanomaterial Science for Photovoltaics

Noted New York Times columnist and Nobel Prize winner, Paul Krugman has weighed in on the subject of solar power with somewhat mixed results.

He somehow believes that maintaining Moore’s Law over the past half century does not indicate an impressive “mastery of the material world”:

“Moore’s Law — in which the price of computing power falls roughly 50 percent every 18 months — has powered an ever-expanding range of applications, from faxes to Facebook.

Our mastery of the material world, on the other hand, has advanced much more slowly. The sources of energy, the way we move stuff around, are much the same as they were a generation ago.”

I suppose Prof. Krugman believes that the doubling of the number of transistors on a chip every two years comes solely from software developments.

But all of this the Nobel laureate presents to us only so he can introduce the concept of “Moore’s law in solar energy,” which a regular reader of Spectrum will know has not tracked as regularly as some pundits have suggested and may have fallen completely out of sight in the views of most.

Nonetheless Prof. Krugman is correct that the overall trend in the last 25 years has been a reduction in the costs of photovoltaics. But he runs afoul of sound reasoning when he chalks up the lack of greater adoption of solar power with this decreasing price trend—especially within the power grid—to the good old fossil fuel conspiracy.

I am afraid it is a bit more complex than that and part of it leads back to the subject he made a hash of at the beginning of his editorial: material science.

The problem has been to develop a material that produces high conversion rates at a reasonable cost. And a review of just this blog will reveal how much time and resources have been devoted to developing that material with everything from dye-sensitized solar cells to the use of quantum dots.

There is even a vocal segment that believes the nanotechnology solutions that could offer a cheap and highly efficient material for converting the sun’s energy into electricity should be banned because they cause more harm than good. So much for appealing to the sensibility of the so-called environmentalist.

I would like to suggest to Prof. Krugman that instead of railing against the evil intentions of oil producers, he look at some new proposals for ensuring that the technological innovations we need are developed rather than merely promised for some point in the future or their absences blamed on flimsy conspiracy theories.

When Promises from Nanotechnology Go Horribly Wrong

The modern-day snake oil pedaled by the less scrupulous among us sometimes consists of alternative energy and some little known emerging technology, and occasionally the potent mix of both of them together.

We need only look at the cautionary tale of Solyndra to see how desperate the US government was to give it money in the hope that they could make solar power just a little bit better than it is.

Combining precise amounts of desperation, greed and ignorance can really do people in as we can see from the latest bit of news coming out of India that follows along these lines.

The Kerala High Court in India has been investigating some outfit that calls itself Nano Excel Pvt Ltd after documents revealed that investors were promised high returns for a project that was touted as the “first nanotechnology-based hydroelectric power generation plant in the country”.

Reports estimate that the company “swindled” Rs350 crores ($71 million) from investors after claiming that they had a memorandum of understanding with the government to build a power plant with initial generation capacity of “100 MW, which would be scaled up to 10,000 MW by 2015.” Instead the only agreement Nano Excel had with the government was to build “a 14 MV small scale power plant.”

It seems Nano Excel was also claiming that they had deals in place with low-cost solar cell maker Nanosolar  as well as Korea-based inorganic chemical component manufacturer Biocera Co.

It’s not clear whether there were in fact deals in place with those companies, or not, but when you fudge the facts on this scale it’s hard to believe anything the company might have said.

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
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Dexter Johnson
Madrid, Spain
 
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Rachel Courtland
Associate Editor, IEEE Spectrum
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