The nanomaterial is composed of tiny tin crystals, which are to be deployed at the minus pole of the batteries (anode). When charging the batteries, lithium ions are absorbed at this electrode; while discharging, they are released again (see box). “The more lithium ions the electrodes can absorb and release – the better they can breathe, as it were – the more energy can be stored in a battery,” explains Kovalenko.

Uniform crystals

The element tin is ideal for this: every tin atom can absorb at least four lithium ions. However, the challenge is to deal with the volume change of tin electrodes: tin crystal becomes up to three times bigger if it absorbs a lot of lithium ions and shrinks again when it releases them back. The scientists thus resorted to nanotechnology: they produced the tiniest tin nanocrystals and embedded a large number of them in a porous, conductive permeable carbon matrix. Much like how a sponge can suck up water and release it again, an electrode constructed in this way can absorb lithium ions while charging and release them when discharging. If the electrode were made of a compact tin block, this would practically be impossible.

During the development of the nanomaterial, the issue of the ideal size for the nanocrystals arose, which also carries the challenge of producing uniform crystals. “The trick here was to separate the two basic steps in the formation of the crystals – the formation of as small as a crystal nucleus as possible on the one hand and its subsequent growth on the other,” explains Kovalenko. By influencing the time and temperature of the growth phase, the scientists were able to control the size of the crystals. “We are the first to produce such small tin crystals with such precision,” says the scientist.

Larger cycle stability

Using uniform tin nanocrystals, carbon, and binding agents, the scientists produced different test electrodes for batteries. “This enables twice as much power to be stored compared to conventional electrodes,” says Kovalenko. The size of the nanocrystals did not affect the storage capacity during the initial charging and discharging cycle. After a few charging and discharging cycles, however, differences caused by the crystal size became apparent: batteries with ten-nanometre crystals in the electrodes were able to store considerably more energy than ones with twice the diameter. The scientists assume that the smaller crystals perform better because they can absorb and release lithium ions more effectively. “Ten-nanometre tin crystals thus seem to be just the ticket for lithium ion batteries,” says Kovalenko.

As the scientists now know the ideal size for the tin nanocrystals, they would like to turn their attention to the remaining challenges of producing optimum tin electrodes in further research projects. These include the choice of the best possible carbon matrix and binding agent for the electrodes, and the electrodes’ ideal microscopic structure. Moreover, an optimal and stable electrolyte liquid in which the lithium ions can travel back and forth between the two poles in the battery also needs to be selected. Ultimately, the production costs are also an issue, which the researchers are looking to reduce by testing which cost-effective base materials are suitable for electrode production. The aim is to prepare batteries with an increased energy storage capacity and lifespan for the market, in collaboration with a Swiss industrial partner.

How lithium ion batteries work

In lithium ion batteries, the energy is stored in the form of positively charged lithium atoms (ions) that are found at the minus pole in a charged battery. If energy is taken from the battery, negatively charged electrons flow from the minus pole to the plus pole via the external circuit. To balance the charge, positively charged lithium ions also flow from the minus pole to the plus pole. However, these travel in the electrolyte fluid inside the battery. The process is reversible: lithium ion batteries can be recharged with electricity. In most lithium ion batteries these days, the plus pole is composed of the transition metal oxides cobalt, nickel, and manganese, the minus pole of graphite. In more powerful lithium ion batteries of the next generation, however, elements such as tin or silicon may well be used at the minus pole.

Source: ETH Life

The new technology has the potential to dramatically increase the driving range of electric vehicles and eventually transform highway travel, according to the researchers. Their results are published in the journal Applied Physics Letters (APL).

“Our vision is that you’ll be able to drive onto any highway and charge your car,” said Shanhui Fan, an associate professor of electrical engineering. “Large-scale deployment would involve revamping the entire highway system and could even have applications beyond transportation.”

Driving range

A wireless charging system would address a major drawback of plug-in electric cars – their limited driving range. The all-electric Nissan Leaf, for example, gets less than 100 miles on a single charge, and the battery takes several hours to fully recharge.

A charge-as-you-drive system would overcome these limitations. “What makes this concept exciting is that you could potentially drive for an unlimited amount of time without having to recharge,” said APL study co-author Richard Sassoon, the managing director of the Stanford Global Climate and Energy Project (GCEP), which funded the research. “You could actually have more energy stored in your battery at the end of your trip than you started with.”

The wireless power transfer is based on a technology called magnetic resonance coupling. Two copper coils are tuned to resonate at the same natural frequency – like two wine glasses that vibrate when a specific note is sung. The coils are placed a few feet apart. One coil is connected to an electric current, which generates a magnetic field that causes the second coil to resonate. This magnetic resonance results in the invisible transfer of electric energy through the air from the first coil to the receiving coil.

“Wireless power transfer will only occur if the two resonators are in tune,” Fan noted. “Objects tuned at different frequencies will not be affected.”

In 2007, researchers at the Massachusetts Institute of Technology used magnetic resonance to light a 60-watt bulb. The experiment demonstrated that power could be transferred between two stationary coils about six feet apart, even when humans and other obstacles are placed in between.

Click here to view the embedded video.

“In the MIT experiment, the magnetic field appeared to have no impact on people who stood between the coils,” Fan said. “That’s very important in terms of safety. “

Wireless charging

The MIT researchers have created a spinoff company that’s developing a stationary charging system capable of wirelessly transferring about 3 kilowatts of electric power to a vehicle parked in a garage or on the street.

Fan and his colleagues wondered if the MIT system could be modified to transfer 10 kilowatts of electric power over a distance of 6.5 feet – enough to charge a car moving at highway speeds. The car battery would provide an additional boost for acceleration or uphill driving.

Here’s how the system would work: A series of coils connected to an electric current would be embedded in the highway. Receiving coils attached to the bottom of the car would resonate as the vehicle speeds along, creating magnetic fields that continuously transfer electricity to charge the battery.

Source: Stanford University News.

The resulting electric Berlingo van carried a whopping 180 kilowatt-hours’ worth of batteries, which consumed almost the entire rear compartment of the vehicle. This is obviously less than optimum for a production vehicle. Even the cheapest guestimate of what that amount of energy storage might cost would put the Berlingo’s battery pack price in the tens of thousands of dollars. But assuming more advancements in battery technology, which seem to be in the news almost daily, the future of the concept is not too far fetched.

The distance covered by the electrified Berlingo was 1000 KM or 621 miles, with the trip originating in Flensburg, Germany and ending Munich. Speeds on the route ranged from 30 to 50 mph.

The time of the trip was 17 hours, though the planners estimated it would take 20. An escort car followed with relief drivers. The trip covered country roads, city streets and the Autobahn, giving a variety of driving conditions, adding to the veracity of the test.

Once the can arrived in Munich, for the eCarTec 2011 3rd International Trade Fair for Electric Mobility, there was still enough remaining charge for an additional 100 miles.

We can only hope that more companies will start thinking outside the box and push EV envelope!

Braun’s group developed a three-dimensional nanostructure for battery cathodes that allows for dramatically faster charging and discharging without sacrificing energy storage capacity. The researchers’ findings will be published in the March 20 advance online edition of the journal Nature Nanotechnology.

Aside from quick-charge consumer electronics, batteries that can store a lot of energy, release it fast and recharge quickly are desirable for electric vehicles, medical devices, lasers and military applications.

“This system that we have gives you capacitor-like power with battery-like energy,” said Braun, a professor of materials science and engineering. “Most capacitors store very little energy. They can release it very fast, but they can’t hold much. Most batteries store a reasonably large amount of energy, but they can’t provide or receive energy rapidly. This does both.”

The performance of typical lithium-ion (Li-ion) or nickel metal hydride (NiMH) rechargeable batteries degrades significantly when they are rapidly charged or discharged. Making the active material in the battery a thin film allows for very fast charging and discharging, but reduces the capacity to nearly zero because the active material lacks volume to store energy.

Braun’s group wraps a thin film into three-dimensional structure, achieving both high active volume (high capacity) and large current. They have demonstrated battery electrodes that can charge or discharge in a few seconds, 10 to 100 times faster than equivalent bulk electrodes, yet can perform normally in existing devices.

This kind of performance could lead to phones that charge in seconds or laptops that charge in minutes, as well as high-power lasers and defibrillators that don’t need time to power up before or between pulses.

Braun is particularly optimistic for the batteries’ potential in electric vehicles. Battery life and recharging time are major limitations of electric vehicles. Long-distance road trips can be their own form of start-and-stop driving if the battery only lasts for 100 miles and then requires an hour to recharge.

“If you had the ability to charge rapidly, instead of taking hours to charge the vehicle you could potentially have vehicles that would charge in similar times as needed to refuel a car with gasoline,” Braun said. “If you had five-minute charge capability, you would think of this the same way you do an internal combustion engine. You would just pull up to a charging station and fill up.”

Click here to read the rest of this article at ScienceDaily.com.

Electric vehicles records are dropping like flies these days, as more and more vehicles push the boundaries of what’s possible for electric cars, boats, and planes. The latest to fall: the record for longest drive ever in a battery-powered vehicle (no recharge) was broken by a new, experimental electric vehicle called “Schluckspecht” (“heavy drinker” in colloquial German).

Developed at the University of Applied Sciences in Offenburg, the car – which is not pretty – does a solid Energizer bunny routine, going and going and going for 1631.5km (1013.77 miles) without needing to recharge the battery.

The test drive took place in Boxberg at the Bosch corporate test track, where a team of four drivers made the record run alongside a camera-equipped pace car. The 36 hour and 12 minute drive (which didn’t exactly break any EV speed records) was also monitored by European testing agents from TÜV Süd.

This world record follows the team’s successful participation in the South-African Solar Challenge 2010, in which the Schluckspecht drove 626.6km (389.35 miles) on public roads – farther (at the time) than any other electric vehicle.

The Schluckspecht boasts little in the way of creature comforts, a fact which helped reduce overall weight and was no doubt helpful during its record-setting drive. However, the engineering behind its design also played a large part in its success, as the Schluckspecht was built from the ground up specifically to chase battery-powered vehicle records in a lab belonging to Ms. Sunmin Lee from Pforzheim University.

The body was shaped with “pure aerodynamics” in mind, and – since the vehicle makes use of two wheel-mounted hub-motors – without the need to accommodate an internal engine or transmission.

Source: Gas 2.0.

But a third dimension, one that has both tangible and intangible properties, sees the addition of new EV charging stations can as powerful marketing tools, especially when the charging stations being installed have all the familiarity of the traditional gas station but include the unmistakable connection to clean energy roots via the solar panels they are attached to.

Beginning last week with stations at Serra Automotive in Grand Blanc, Michigan and American Chevrolet in Modesto, California, GM is outfitting at least 26 dealerships with solar canopy arrays to charge and display the plug-in Chevy Volt in its clean energy habitat. Each installation will allow the simultaneous charging of 6, 12,18 or 24 vehicles, depending on how many solar canopies the dealer chooses to install.

“The question isn’t whether to install a solar canopy, it’s where and how many,” said Joe Serra, president of Serra Automotive in Grand Blanc, Michigan.

The solar canopy projects are being installed by Michigan-based Sunlogics, a global developer and operator of large-scale solar power projects that just received $7.5 million in investment capital from GM Ventures, the $100-million venture capital arm of GM. The addition of Sunlogics brings the number of companies to six in the GM Ventures portfolio, all of which are developing technologies in the sustainable mobility sector.

According to GM, each 20-kilowatt canopy will generate electricity equivalent to 12 full vehicle charges per day and excess electricity created will help supplement the dealership’s electrical power needs, providing as much as one-quarter of a dealership’s electricity.

Click here to read the rest of this article at EarthandIndustry.com.

Nissan, 44 percent owned by Renault of France, said it aims to commercialize the technology in Japan by March 2012.

The system works by linking the car via a quick charging port to the house’s electricity distribution panel. Power can also be fed the other way if the house generates its own electricity with rooftop solar panels.

The Leaf batteries have a capacity of 24 kilowatt hours when fully charged, equivalent to the electricity used by the average Japanese household in two days, said the company.

The output from the vehicle comes to six kilowatts, enough to power electricity-guzzling appliances such as a refrigerator, air conditioner and washing machine at the same time, the company said.

Nissan says as well as its potential use in blackouts, the car can be charged during night time off-peak hours and the electricity used by households during high-demand periods.

Source: AFP

The Rice lab of Professor Pulickel Ajayan has packed an entire lithium ion energy storage device into a single nanowire, as reported this month in the American Chemical Society journal Nano Letters. The researchers believe their creation is as small as such devices can possibly get, and could be valuable as a rechargeable power source for new generations of nanoelectronics.

In their paper, researchers described testing two versions of their battery/supercapacitor hybrid. The first is a sandwich with nickel/tin anode, polyethylene oxide (PEO) electrolyte and polyaniline cathode layers; it was built as proof that lithium ions would move efficiently through the anode to the electrolyte and then to the supercapacitor-like cathode, which stores the ions in bulk and gives the device the ability to charge and discharge quickly.

The second packs the same capabilities into a single nanowire. The researchers built centimeter-scale arrays containing thousands of nanowire devices, each about 150 nanometers wide. A nanometer is a billionth of a meter, thousands of times smaller than a human hair.

Ajayan’s team has been inching toward single-nanowire devices for years. The researchers first reported the creation of three-dimensional nanobatteries last December. In that project, they encased vertical arrays of nickel-tin nanowires in PMMA, a widely used polymer best known as Plexiglas, which served as an electrolyte and insulator. They grew the nanowires via electrodeposition in an anodized alumina template atop a copper substrate. They widened the template’s pores with a simple chemical etching technique that created a gap between the wires and the alumina, and then drop-coated PMMA to encase the wires in a smooth, consistent sheath. A chemical wash removed the template and left a forest of electrolyte-encased nanowires.

In that battery, the encased nickel-tin was the anode, but the cathode had to be attached on the outside.

The new process tucks the cathode inside the nanowires, said Ajayan, a professor of mechanical engineering and materials science. In this feat of nanoengineering, the researchers used PEO as the gel-like electrolyte that stores lithium ions and also serves as an electrical insulator between nanowires in an array.

After much trial and error, they settled on an easily synthesized polymer known as polyaniline (PANI) as their cathode. Drop-coating the widened alumina pores with PEO coats the insides, encases the anodes and leaves tubes at the top into which PANI cathodes could also be drop-coated. An aluminum current collector placed on top of the array completes the circuit.

“The idea here is to fabricate nanowire energy storage devices with ultrathin separation between the electrodes,” said Arava Leela Mohana Reddy, a research scientist at Rice and co-author of the paper. “This affects the electrochemical behavior of the device. Our devices could be a very useful tool to probe nanoscale phenomenon.”

The team’s experimental batteries are about 50 microns tall — about the diameter of a human hair and almost invisible when viewed edge-on, Reddy said. Theoretically, the nanowire energy storage devices can be as long and wide as the templates allow, which makes them scalable.

The nanowire devices show good capacity; the researchers are fine-tuning the materials to increase their ability to repeatedly charge and discharge, which now drops off after a about 20 cycles.

“There’s a lot to be done to optimize the devices in terms of performance,” said the paper’s lead author, Sanketh Gowda, a chemical engineering graduate student at Rice. “Optimization of the polymer separator and its thickness and an exploration of different electrode systems could lead to improvements.”

Rice graduate student Xiaobo Zhan is a co-author of the paper.

The Hartley Family Foundation, Rice University, National Institutes of Health, Army Research Office and Multidisciplinary University Research Initiative supported the research.

Source: ScienceDaily.com

“For an electric vehicle, you need a lightweight battery that can be charged quickly and holds its charge capacity after repeated cycling,” says Yuegang Zhang, a staff scientist with Berkeley Lab’s Molecular Foundry, in the Inorganic Nanostructures Facility, who led this research. “Here, we’ve shown the rational design of a nanoscale architecture, which doesn’t need an additive or binder to operate, to improve battery performance.”

Graphene is a single-atom-thick, “chicken-wire” lattice of carbon atoms with stellar electronic and mechanical properties, far beyond silicon and other traditional semiconductor materials. Previous work on graphene by Zhang and his colleagues has emphasized electronic device applications.

In this study, the team assembled alternating layers of graphene and tin to create a nanoscale composite. To create the composite material, a thin film of tin is deposited onto graphene. Next, another sheet of graphene is transferred on top of the tin film. This process is repeated to create a composite material, which is then heated to 300˚ Celsius (572˚ Fahrenheit) in a hydrogen and argon environment. During this heat treatment, the tin film transforms into a series of pillars, increasing the height of the tin layer.

“The formation of these tin nanopillars from a thin film is very particular to this system, and we find the distance between the top and bottom graphene layers also changes to accommodate the height change of the tin layer,” says Liwen Ji, a post-doctoral researcher at the Foundry. Ji is the lead author and Zhang the corresponding author of a paper reporting the research in the journal Energy and Environmental Science.

The change in height between the graphene layers in these new nanocomposites helps during electrochemical cycling of the battery, as the volume change of tin improves the electrode’s performance. In addition, this accommodating behavior means the battery can be charged quickly and repeatedly without degrading — crucial for rechargeable batteries in electric vehicles.

Source: Lawrence-Berkely National Laboratory

Storing the sun’s heat in chemical form—rather than converting it to electricity or storing the heat itself in a heavily insulated container—has significant advantages, since in principle the chemical material can be stored for long periods of time without losing any of its stored energy. The problem with that approach has been that until now the chemicals needed to perform this conversion and storage either degraded within a few cycles, or included the element ruthenium, which is rare and expensive.
Last year, MIT associate professor Jeffrey Grossman and four co-authors figured out exactly how fulvalene diruthenium—known to scientists as the best chemical for reversibly storing solar energy, since it did not degrade—was able to accomplish this feat. Grossman said at the time that better understanding this process could make it easier to search for other compounds, made of abundant and inexpensive materials, which could be used in the same way.

Now, he and postdoc Alexie Kolpak have succeeded in doing just that. A paper describing their new findings has just been published online in the journal Nano Letters, and will appear in print in a forthcoming issue.

The new material found by Grossman and Kolpak is made using carbon nanotubes, tiny tubular structures of pure carbon, in combination with a compound called azobenzene. The resulting molecules, produced using nanoscale templates to shape and constrain their physical structure, gain “new properties that aren’t available” in the separate materials, says Grossman, the Carl Richard Soderberg Associate Professor of Power Engineering.

Not only is this new chemical system less expensive than the earlier ruthenium-containing compound, but it also is vastly more efficient at storing energy in a given amount of space—about 10,000 times higher in volumetric energy density, Kolpak says—making its energy density comparable to lithium-ion batteries. By using nanofabrication methods, “you can control [the molecules’] interactions, increasing the amount of energy they can store and the length of time for which they can store it—and most importantly, you can control both independently,” she says.

Thermo-chemical storage of solar energy uses a molecule whose structure changes when exposed to sunlight, and can remain stable in that form indefinitely. Then, when nudged by a stimulus—a catalyst, a small temperature change, a flash of light—it can quickly snap back to its other form, releasing its stored energy in a burst of heat. Grossman describes it as creating a rechargeable heat battery with a long shelf life, like a conventional battery.

One of the great advantages of the new approach to harnessing solar energy, Grossman says, is that it simplifies the process by combining energy harvesting and storage into a single step. “You’ve got a material that both converts and stores energy,” he says. “It’s robust, it doesn’t degrade, and it’s cheap.” One limitation, however, is that while this process is useful for heating applications, to produce electricity would require another conversion step, using thermoelectric devices or producing steam to run a generator.

While the new work shows the energy-storage capability of a specific type of molecule — azobenzene-functionalized carbon nanotubes — Grossman says the way the material was designed involves “a general concept that can be applied to many new materials.” Many of these have already been synthesized by other researchers for different applications, and would simply need to have their properties fine-tuned for solar thermal storage.

The key to controlling solar thermal storage is an energy barrier separating the two stable states the molecule can adopt; the detailed understanding of that barrier was central to Grossman’s earlier research on fulvalene dirunthenium, accounting for its long-term stability. Too low a barrier, and the molecule would return too easily to its “uncharged” state, failing to store energy for long periods; if the barrier were too high, it would not be able to easily release its energy when needed. “The barrier has to be optimized,” Grossman says.

Already, the team is “very actively looking at a range of new materials,” he says. While they have already identified the one very promising material described in this paper, he says, “I see this as the tip of the iceberg. We’re pretty jazzed up about it.”

Yosuke Kanai, assistant professor of chemistry at the University of North Carolina at Chapel Hill, says “the idea of reversibly storing solar energy in chemical bonds is gaining a lot of attention these days. The novelty of this work is how these authors have shown that the energy density can be significantly increased by using carbon nanotubes as nanoscale templates. This innovative idea also opens up an interesting avenue for tailoring already-known photoactive molecules for solar thermal fuels and storage in general.”

Source: MIT News Office