Better Batteries: New Technology Improves Both Energy Capacity and Charge Rate in Rechargeable Batteries

Better Batteries: New Technology Improves Both Energy Capacity and Charge Rate in Rechargeable Batteries

  8:37:00 PM    Science Lover

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Imagine a cellphone battery that stayed charged for more than a week and recharged in just 15 minutes. That dream battery could be closer to reality thanks to Northwestern University research.

New research could lead to rechargeable lithium-ion
batteries that hold a charge up to 10 times greater than
current technology and that charge 10 times faster than
current batteries. (Credit: © janaka Dharmasena / Fotolia)

A team of engineers has created an electrode for lithium-ion batteries -- rechargeable batteries such as those found in cellphones and iPods -- that allows the batteries to hold a charge up to 10 times greater than current technology. Batteries with the new electrode also can charge 10 times faster than current batteries.

The researchers combined two chemical engineering approaches to address two major battery limitations -- energy capacity and charge rate -- in one fell swoop. In addition to better batteries for cellphones and iPods, the technology could pave the way for more efficient, smaller batteries for electric cars.

The technology could be seen in the marketplace in the next three to five years, the researchers said.

A paper describing the research is published by the journal Advanced Energy Materials.

"We have found a way to extend a new lithium-ion battery's charge life by 10 times," said Harold H. Kung, lead author of the paper. "Even after 150 charges, which would be one year or more of operation, the battery is still five times more effective than lithium-ion batteries on the market today."

Kung is professor of chemical and biological engineering in the McCormick School of Engineering and Applied Science. He also is a Dorothy Ann and Clarence L. Ver Steeg Distinguished Research Fellow.

Lithium-ion batteries charge through a chemical reaction in which lithium ions are sent between two ends of the battery, the anode and the cathode. As energy in the battery is used, the lithium ions travel from the anode, through the electrolyte, and to the cathode; as the battery is recharged, they travel in the reverse direction.

With current technology, the performance of a lithium-ion battery is limited in two ways. Its energy capacity -- how long a battery can maintain its charge -- is limited by the charge density, or how many lithium ions can be packed into the anode or cathode. Meanwhile, a battery's charge rate -- the speed at which it recharges -- is limited by another factor: the speed at which the lithium ions can make their way from the electrolyte into the anode.

In current rechargeable batteries, the anode -- made of layer upon layer of carbon-based graphene sheets -- can only accommodate one lithium atom for every six carbon atoms. To increase energy capacity, scientists have previously experimented with replacing the carbon with silicon, as silicon can accommodate much more lithium: four lithium atoms for every silicon atom. However, silicon expands and contracts dramatically in the charging process, causing fragmentation and losing its charge capacity rapidly.

Currently, the speed of a battery's charge rate is hindered by the shape of the graphene sheets: they are extremely thin -- just one carbon atom thick -- but by comparison, very long. During the charging process, a lithium ion must travel all the way to the outer edges of the graphene sheet before entering and coming to rest between the sheets. And because it takes so long for lithium to travel to the middle of the graphene sheet, a sort of ionic traffic jam occurs around the edges of the material.

Now, Kung's research team has combined two techniques to combat both these problems. First, to stabilize the silicon in order to maintain maximum charge capacity, they sandwiched clusters of silicon between the graphene sheets. This allowed for a greater number of lithium atoms in the electrode while utilizing the flexibility of graphene sheets to accommodate the volume changes of silicon during use.

"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's team also used a chemical oxidation process to create miniscule holes (10 to 20 nanometers) in the graphene sheets -- termed "in-plane defects" -- so the lithium ions would have a "shortcut" into the anode and be stored there by reaction with silicon. This reduced the time it takes the battery to recharge by up to 10 times.

This research was all focused on the anode; next, the researchers will begin studying changes in the cathode that could further increase effectiveness of the batteries. They also will look into developing an electrolyte system that will allow the battery to automatically and reversibly shut off at high temperatures -- a safety mechanism that could prove vital in electric car applications.

The Energy Frontier Research Center program of the U.S. Department of Energy, Basic Energy Sciences, supported the research.

The paper is titled "In-Plane Vacancy-Enabled High-Power Si-Graphene Composite Electrode for Lithium-Ion Batteries." Other authors of the paper are Xin Zhao, Cary M. Hayner and Mayfair C. Kung, all from Northwestern.

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Important step in the next generation of computing

Important step in the next generation of computing

  11:56:00 PM    Science Lover

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Scientists have taken one step closer to the next generation of computers. Research from the Cavendish Laboratory, the University of Cambridge's Department of Physics, provides new insight into spintronics, which has been hailed as the successor to the transistor.

Progress in electronics has relied heavily on reducing the size of the transistor to create small, powerful computers. Now spintronics, hailed as the successor to the transistor, looks set to transform the field.

Spintronics, which exploits the electron’s tiny magnetic moment, or ‘spin’, could radically change computing due to its potential of high-speed, high-density and low-power consumption. The new research sheds light on how to make ‘spin’ more efficient.

For the past fifty years, progress in electronics has relied heavily on the downsizing of the transistor through the semiconductor industry in order to provide the technology for the small, powerful computers that are the basis of our modern information society. In a 1965 paper, Intel co-founder Gordon E. Moore described how the number of transistors that could be placed inexpensively on an integrated circuit had doubled every year between 1958 and 1965, predicting that the trend would continue for at least ten more years.

That prediction, now known as Moore’s Law, effectively described a trend that has continued ever since, but the end of that trend—the moment when transistors are as small as atoms, and cannot be shrunk any further—is expected as early as 2015. At the moment, researchers are seeking new concepts of electronics that sustain the growth of computing power.

Spintronics research attempts to develop a spin-based electronic technology that will replace the charge-based technology of semiconductors. Scientists have already begun to develop new spin-based electronics, beginning with the discovery in 1988 of giant magnetoresistance (GMR) effect. The discovery of GMR effect brought about a breakthrough in gigabyte hard disk drives and was also key in the development of portable electronic devices such as the iPod.

While conventional technology relies on harnessing the charge of electrons, the field of spintronics depends instead on the manipulation of electrons’ spin. One of the unique properties in spintronics is that spins can be transferred without the flow of electric charge currents. This is called “spin current” and unlike other concepts of harnessing electrons, the spin current can transfer information without generating heat in electric devices. The major remaining obstacle to a viable spin current technology is the difficulty of creating a volume of spin current large enough to support current and future electronic devices.



However, the new Cambridge researchers in close collaboration with Professor Sergej Demokritov group at the University of Muenster, Germany, have, in part, addressed this issue. In order to create enhanced spin currents, the researchers used the collective motion of spins called spin waves (the wave property of spins). By bringing spin waves into interaction, they have demonstrated a new, more efficient way of generating spin current.

Dr Hidekazu Kurebayashi, from the Microelectronics Group at the Cavendish Laboratory, said: “You can find lots of different waves in nature, and one of the fascinating things is that waves often interact with each other. Likewise, there are a number of different interactions in spin waves. Our idea was to use such spin wave interactions for generating efficient spin currents.”

According to their findings, one of the spin wave interactions (called three-magnon splitting) generates spin current ten times more efficiently than using pre-interacting spin-waves. Additionally, the findings link the two major research fields in spintronics, namely the spin current and the spin wave interaction.

Dr Kurebayashi added: “I am grateful for the collegial and supportive environment at the Cavendish which makes the flexibility I have been afforded in my postdoc research. This allows me freedom to pursue my interest in spintronics outside of my normal research. I feel that Cambridge is the place where you are able to explore your ideas in an intellectually stimulating atmosphere.”

The research was published on Sunday 03 July in the journal Nature Materials.

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Energy Harvesting: Nanogenerators Grow Strong Enough to Power Small Conventional Electronic Devices

Energy Harvesting: Nanogenerators Grow Strong Enough to Power Small Conventional Electronic Devices

  10:22:00 AM    Science Lover

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Blinking numbers on a liquid-crystal display (LCD) often indicate that a device's clock needs resetting. But in the laboratory of Zhong Lin Wang at Georgia Tech, the blinking number on a small LCD signals the success of a five-year effort to power conventional electronic devices with nanoscale generators that harvest mechanical energy from the environment using an array of tiny nanowires.

In a new technique for producing nanogenerators,
researchers transfer vertically-aligned nanowires to a 
flexible substrate. (Credit: Courtesy of Zhong Lin Wang)

In this case, the mechanical energy comes from compressing a nanogenerator between two fingers, but it could also come from a heartbeat, the pounding of a hiker's shoe on a trail, the rustling of a shirt, or the vibration of a heavy machine. While these nanogenerators will never produce large amounts of electricity for conventional purposes, they could be used to power nanoscale and microscale devices -- and even to recharge pacemakers or iPods.

Wang's nanogenerators rely on the piezoelectric effect seen in crystalline materials such as zinc oxide, in which an electric charge potential is created when structures made from the material are flexed or compressed. By capturing and combining the charges from millions of these nanoscale zinc oxide wires, Wang and his research team can produce as much as three volts -- and up to 300 nanoamps.

"By simplifying our design, making it more robust and integrating the contributions from many more nanowires, we have successfully boosted the output of our nanogenerator enough to drive devices such as commercial liquid-crystal displays, light-emitting diodes and laser diodes," said Wang, a Regents' professor in Georgia Tech's School of Materials Science and Engineering. "If we can sustain this rate of improvement, we will reach some true applications in healthcare devices, personal electronics, or environmental monitoring."

Recent improvements in the nanogenerators, including a simpler fabrication technique, were reported online last week in the journal Nano Letters. Earlier papers in the same journal and in Nature Communications reported other advances for the work, which has been supported by the Defense Advanced Research Projects Agency (DARPA), the U.S. Department of Energy, the U.S. Air Force, and the National Science Foundation.

"We are interested in very small devices that can be used in applications such as health care, environmental monitoring and personal electronics," said Wang. "How to power these devices is a critical issue."

The earliest zinc oxide nanogenerators used arrays of nanowires grown on a rigid substrate and topped with a metal electrode. Later versions embedded both ends of the nanowires in polymer and produced power by simple flexing. Regardless of the configuration, the devices required careful growth of the nanowire arrays and painstaking assembly.

In the latest paper, Wang and his group members Youfan Hu, Yan Zhang, Chen Xu, Guang Zhu and Zetang Li reported on much simpler fabrication techniques. First, they grew arrays of a new type of nanowire that has a conical shape. These wires were cut from their growth substrate and placed into an alcohol solution.

The solution containing the nanowires was then dripped onto a thin metal electrode and a sheet of flexible polymer film. After the alcohol was allowed to dry, another layer was created. Multiple nanowire/polymer layers were built up into a kind of composite, using a process that Wang believes could be scaled up to industrial production.

When flexed, these nanowire sandwiches -- which are about two centimeters by 1.5 centimeters -- generated enough power to drive a commercial display borrowed from a pocket calculator.

Wang says the nanogenerators are now close to producing enough current for a self-powered system that might monitor the environment for a toxic gas, for instance, then broadcast a warning. The system would include capacitors able to store up the small charges until enough power was available to send out a burst of data.

While even the current nanogenerator output remains below the level required for such devices as iPods or cardiac pacemakers, Wang believes those levels will be reached within three to five years. The current nanogenerator, he notes, is nearly 100 times more powerful than what his group had developed just a year ago.

Writing in a separate paper published in October in the journal Nature Communications, group members Sheng Xu, Benjamin J. Hansen and Wang reported on a new technique for fabricating piezoelectric nanowires from lead zirconate titanate -- also known as PZT. The material is already used industrially, but is difficult to grow because it requires temperatures of 650 degrees Celsius.

In the paper, Wang's team reported the first chemical epitaxial growth of vertically-aligned single-crystal nanowire arrays of PZT on a variety of conductive and non-conductive substrates. They used a process known as hydrothermal decomposition, which took place at just 230 degrees Celsius.

With a rectifying circuit to convert alternating current to direct current, the researchers used the PZT nanogenerators to power a commercial laser diode, demonstrating an alternative materials system for Wang's nanogenerator family. "This allows us the flexibility of choosing the best material and process for the given need, although the performance of PZT is not as good as zinc oxide for power generation," he explained.

And in another paper published in Nano Letters, Wang and group members Guang Zhu, Rusen Yang and Sihong Wang reported on yet another advance boosting nanogenerator output. Their approach, called "scalable sweeping printing," includes a two-step process of (1) transferring vertically-aligned zinc oxide nanowires to a polymer receiving substrate to form horizontal arrays and (2) applying parallel strip electrodes to connect all of the nanowires together.

Using a single layer of this structure, the researchers produced an open-circuit voltage of 2.03 volts and a peak output power density of approximately 11 milliwatts per cubic centimeter.

"From when we got started in 2005 until today, we have dramatically improved the output of our nanogenerators," Wang noted. "We are within the range of what's needed. If we can drive these small components, I believe we will be able to power small systems in the near future. In the next five years, I hope to see this move into application."

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New Nanogenerator May Charge IPods And Cell Phones With A Wave Of The Hand

New Nanogenerator May Charge IPods And Cell Phones With A Wave Of The Hand

  3:18:00 AM    Science Lover

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Pictured is a schematic illustration shows the microfiber-nanowire hybrid nanogenerator, which is the basis of using fabrics for generating electricity. (Credit: Professor. Z. L. Wang and Dr. X. D. Wang, Georgia Institute of Technology.)

Imagine if all you had to do to charge your iPod or your BlackBerry was to wave your hand, or stretch your arm, or take a walk? You could say goodbye to batteries and never have to plug those devices into a power source again.

In research presented at the American Chemical Society's 237th National Meeting in Salt Lake City, Utah on March 26, scientists from Georgia describe technology that converts mechanical energy from body movements or even the flow of blood in the body into electric energy that can be used to power a broad range of electronic devices without using batteries.

"This research will have a major impact on defense technology, environmental monitoring, biomedical sciences and even personal electronics," says lead researcher Zhong Lin Wang, Regents' Professor, School of Material Science and Engineering at the Georgia Institute of Technology. The new "nanogenerator" could have countless applications, among them a way to run electronic devices used by the military when troops are far in the field.

The researchers describe harvesting energy from the environment by converting low-frequency vibrations, like simple body movements, the beating of the heart or movement of the wind, into electricity, using zinc oxide (ZnO) nanowires that conduct the electricity. The ZnO nanowires are piezoelectric — they generate an electric current when subjected to mechanical stress. The diameter and length of the wire are 1/5,000th and 1/25th the diameter of a human hair.

In generating energy from movement, Wang says his team concluded that it was most effective to develop a method that worked at low frequencies and was based on flexible materials. The ZnO nanowires met these requirements. At the same time, he says a real advantage of this technology is that the nanowires can be grown easily on a wide variety of surfaces, and the nanogenerators will operate in the air or in liquids once properly packaged. Among the surfaces on which the nanowires can be grown are metals, ceramics, polymers, clothing and even tents.

"Quite simply, this technology can be used to generate energy under any circumstances as long as there is movement," according to Wang.

To date, he says that there have been limited methods created to produce nanopower despite the growing need by the military and defense agencies for nanoscale sensing devices used to detect bioterror agents. The nanogenerator would be particularly critical to troops in the field, where they are far from energy sources and need to use sensors or communication devices. In addition, having a sensor which doesn't need batteries could be extremely useful to the military and police sampling air for potential bioterrorism attacks in the United States, Wang says.

While biosensors have been miniaturized and can be implanted under the skin, he points out that these devices still require batteries, and the new nanogenerator would offer much more flexibility. A major advantage of this new technology is that many nanogenerators can produce electricity continuously and simultaneously. On the other hand, the greatest challenge in developing these nanogenerators is to improve the output voltage and power, he says. Last year Wang's group presented a study on nanogenerators driven by ultrasound. Today's research represents a much broader application of nanogenerators as driven by low-frequency body movement.

The study was funded by the Defense Advanced Research Projects Agency, the Department of Energy, the National Institutes of Health and the National Science Foundation.

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Adapted from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.

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Stick tongue out, wink: gadget introduces new ways to control iPods

Stick tongue out, wink: gadget introduces new ways to control iPods

  9:10:00 PM    Science Lover

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A woman wears the Mimi Switch earphone-shaped device to operate electronic devices such as a digital music player. An iPod can start or stop music when the wearer sticks her tongue out, like in the famous Einstein picture, researchers said

A wink, a smile or a raised eyebrow could soon change the music on your iPod or start up the washing machine, thanks to a new Japanese gadget.

The gizmo – called the “Mimi Switch” or “Ear Switch” – looks like a normal set of headphones, but is fitted with a set of infrared sensors that measure tiny movements inside the ear that result from different facial expressions.

The device is connected to a micro-computer that can control electronic devices, essentially making it a hands-free remote control for anything.

“You will be able to turn on room lights or swing your washing machine into action with a quick twitch of your mouth,” said inventor Kazuhiro Taniguch of Osaka University.

“An iPod can start or stop music when the wearer sticks his tongue out, like in the famous Einstein picture. If he opens his eyes wide, the machine skips to the next tune. A wink with the right eye makes it go back,” he explained.

As for the washing machine: “It can be programmed to run with various other facial expressions, such as a wriggle of the nose or a smile,” he added.

The Mimi Switch could also store and interpret data and get to know its user, Taniguchi said: “It monitors natural movements of the face in everyday life and accumulates data. If it judges that you aren’t smiling enough, it may play a cheerful song.”

The device could also have more serious applications to make people’s lives safer and easier.

“If the system is mounted on a hearing aid for elderly people, it could tell how often they sneeze or whether they are eating regularly,” Taniguchi pointed out.

“If it believes they are not well, it could send a warning message to relatives,” he added.

It could also be used by physically disabled people as a remote control for appliances, such as computers and air conditioners.

Taniguchi, who is now working on a wireless version, said the Mimi Switch could be available in two or three years.

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Affair with iPhone cools when handset breaks

Affair with iPhone cools when handset breaks

  8:56:00 PM    Science Lover

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After four days with phone, trouble in paradise

	A customer at an Apple store at Southpark Mall in Charlotte, N.C., examines the new Apple iPhone during the first day of sales for the device June 29. View related photos
Jason E. Miczek / AP file

By Joe Hutsko

MSNBC contributor

Falling in lust with an expensive device like the iPhone sets owners up for a hard fall if it stops working. I know, because mine died after only four days into our relationship.

At first I thought it was just a hiccup when the iPhone was working fine one minute, then wouldn’t turn on the next. I tried the prescribed reset (hold down the Home and Sleep/Wake buttons at the same time for several seconds until the device restarts) with no luck. Black screen, period. But when I plugged it in the Apple logo appeared as if restarting. Then it vanished, the screen went black again, and a few seconds later the logo reappeared, as if restarting. Again. Then again. And again. Trouble in paradise.

On a whim I held the buttons for a reset again but this time kept holding, until eventually a bright yellow triangle appeared, instructing me to Connect the iPhone to iTunes. This forced “restore mode” allowed the otherwise endless-looped iPhone to appear in iTunes, which prompted me to restore the phone. Since iTunes backs up the phone’s data after every sync I said sure, gladly, please do.

The restore process began — but then the loopy restarts started again. And again, ad nauseam. At that point I felt a little nauseous, too — four days and the iPhone I spent eight hours in line to buy was a goner.

I contacted the AT&T store and was told I could return the phone for a refund (with a 10 percent restocking fee) but could not exchange it for a replacement; all iPhone support is handled by Apple. I contacted a public relations person at Apple and she said she’d have customer service call me. While waiting on that call I decided to drive to the nearby Apple Store with the far-flung hope that they’d simply swap the phone for me (crazily assuming they’d even have another 8 GB model in stock).

An extremely polite Apple customer service rep named Nate called just as I was walking into the Apple Store. He introduced me to the store manager, Sean, who was also on the line. We hung up with Nate and conducted the service business in person. Sean said they’d simply swap my phone for another, and after some help from two guys named Chris at the Genius Bar, they took back the broken one and I left with the new iPhone. Driving home, I had a number of questions. Would they completely erase my iPhone when it reached the service department, so that my private data remains mine alone? What if they hadn’t had another iPhone in stock?

I got answers from Apple’s PR department. Yes, all iPods and iPhones that are exchanged for replacements get wiped clean. As for the in-stock issue, iPhone owners can swap a “DOA” phone for a replacement if within 30 days of purchase. If the store is out of stock or if the purchase is past thirty days (or if a customer doesn’t live near an Apple Store), the repair-by-mail process kicks in.

The owner removes the SIM card (which will work in the previously used phone that the iPhone presumably replaced), mails the iPhone to Apple, and they repair it and send it back. Apple offers the option of a rental iPhone during the repair process for a $29 fee — something that is bound to rub customers the wrong way.

There was no such fee from AT&T when one of my previous phones — the Palm Treo 680 — went in for repairs. While under warranty AT&T automatically ships a loaner phone, which you wind up keeping if they deem your original dead.

They do charge a small fee if you want the replacement sent overnight, but otherwise the repair process is free. (AT&T waived the rush fee the two additional times I had to send the Treo in for replacement due to the thin plastic bezel around the screen repeatedly cracking despite my handling the device with kid gloves.)

Why did my iPhone fail so soon? Apple’s Geniuses couldn’t say on the spot. But I think it had something to do with heat — my iPhone would get incredibly hot to the touch when plugged in and charging while I was on a long phone call. So hot I lived those first three days in constant fear that it would heat to the point of burning up.

So hot that I was tempted to put some raw egg in a foil cup and set it atop the iPhone to see if it would cook — or if not actually cook, turn opaque from the iPhone’s super-heated back surface. Describing this on my blog JOEyGADGET promoted one other iPhone owner to comment:

“Yep, mine seems hot but I don’t know if it’s too hot. Hotness is relative you know.” Agreed when discussing physical attraction, but when talking about physical touch, take my word for it, my original iPhone all but burned the skin on my hand.

SOURCE : http://www.msnbc.msn.com/id/19614050/

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