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Your Mobile May Need Charging Just Once a Month

US scientists have reduced the power consumption of a key component in lithium-ion batteries used in mobile phones which could boost the overall battery life of our gadgets

CHAMPAIGN, Ill. 10-3-2011 - Technophiles who have been dreaming of mobile devices that run longer on lighter, slimmer batteries may soon find their wish has been granted.

University of Illinois engineers have developed a form of ultra-low-power digital memory that is faster and uses 100 times less energy than similar available memory. The technology could give future portable devices much longer battery life between charges.

Led by electrical and computer engineering professor Eric Pop, the team will publish its results in an upcoming issue of Science magazine and online in the March 10 Science Express.

"I think anyone who is dealing with a lot of chargers and plugging things in every night can relate to wanting a cell phone or laptop whose batteries can last for weeks or months," said Pop, who is also affiliated with the Beckman Institute for Advanced Science and Technology at Illinois.

The flash memory used in mobile devices today stores bits as charge, which requires high programming voltages and is relatively slow. Industry has been exploring faster, but higher power phase-change materials (PCM) as an alternative. In PCM memory a bit is stored in the resistance of the material, which is switchable.

Pop's group lowered the power per bit to 100 times less than existing PCM memory by focusing on one simple, yet key factor: size.

Rather than the metal wires standard in industry, the group used carbon nanotubes, tiny tubes only a few nanometers in diameter – 10,000 times smaller than a human hair.

"The energy consumption is essentially scaled with the volume of the memory bit," said graduate student Feng Xiong, the first author of the paper. "By using nanoscale contacts, we are able to achieve much smaller power consumption."

To create a bit, the researchers place a small amount of PCM in a nanoscale gap formed in the middle of a carbon nanotube. They can switch the bit "on" and "off" by passing small currents through the nanotube.

"Carbon nanotubes are the smallest known electronic conductors," Pop said. "They are better than any metal at delivering a little jolt of electricity to zap the PCM bit."


Three parallel memory bits with carbon nanotube electrodes (false color image based on topographic profile from atomic force microscopy). The middle bit is in the "off" state, the other two are "on". The silicon dioxide substrate is shown in blue. | Image courtesy Eric Pop

Nanotubes also boast an extraordinary stability, as they are not susceptible to the degradation that can plague metal wires. In addition, the PCM that functions as the actual bit is immune to accidental erasure from a passing scanner or magnet.

The low-power PCM bits could be used in existing devices with a significant increase in battery life. Right now, a smart phone uses about a watt of energy and a laptop runs on more than 25 watts. Some of that energy goes to the display, but an increasing percentage is dedicated to memory.


A schematic of four bits in various on/off states. The bit is made up of phase-change material (PCM) with a size of about 10 nanometers with carbon nanotube electrodes. The programming current is 100 times lower than the present state-of-the-art memory. | Image by Alex Jerez, Beckman Institute ITG

"Anytime you're running an app, or storing MP3s, or streaming videos, it's draining the battery," said Albert Liao, a graduate student and co-author. "The memory and the processor are working hard retrieving data. As people use their phones to place calls less and use them for computing more, improving the data storage and retrieval operations is important."

Pop believes that, along with improvements in display technology, the nanotube PCM memory could increase an iPhone's energy efficiency so it could run for a longer time on a smaller battery, or even to the point where it could run simply by harvesting its own thermal, mechanical or solar energy – no battery required.

And device junkies will not be the only beneficiaries.

"We're not just talking about lightening our pockets or purses," Pop said. "This is also important for anything that has to operate on a battery, such as satellites, telecommunications equipment in remote locations, or any number of scientific and military applications."

In addition, ultra-low-power memory could cut the energy consumption – and thus the expense – of data storage or supercomputing centers by a large percentage. The low-power memory could also enable three-dimensional integration, a stacking of chips that has eluded researchers because of fabrication and heat problems.

The team has made and tested a few hundred bits so far, and they want to scale up production to create arrays of memory bits that operate together. They also hope to achieve greater data density through clever programming such that each physical PCM bit can program two data bits, called multibit memory.

The team is continuing to work to reduce power consumption and increase energy efficiency even beyond the groundbreaking savings they've already demonstrated.

"Even though we've taken one technology and shown that it can be improved by a factor of 100, we have not yet reached what is physically possible. We have not even tested the limits yet. I think we could lower power by at least another factor of 10," Pop said.


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Thanks, processors are being developed at breakneck speed but batteries are lagging this should improve.

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3D Battery Nanotechnology Could Charge Your Phone in Seconds

Mark Brown Wired U.K. 21 March 2011

A team of researchers at the University of Illinois has made a new type of battery that could charge an electric car in five minutes, your laptop in a couple of minutes, and juice up your mobile phone in seconds.

The new design takes its lead from both batteries and capacitors. The latter components can charge and release energy very fast, but can't hold much of it. Batteries, like the lithium-ion one stuffed in your smartphone, can hold a lot but take hours to recharge.

"This does both," announces Illinois professor Paul Braun, boldly. His findings have been published in the 20 March, 2011, issue of the Nature Nanotechnology journal.

Typical rechargable batteries, like the thin lithium-ion blocks in modern gadgets and nickel metal hydride batteries, degrade significantly if charged or discharged too fast. You can swap the battery's active material with a thin film to get faster charging, but because the material lacks the area to store energy, your iPad would run out of power in seconds.

Braun's solution is to wrap that thin film into a three-dimensional structure to significantly increase surface area, and therefore bump up the energy storage capacity. The battery can last for the same length of time as a traditional battery, but charging is sped up by up to 10 to 100 times.

To make this novel structure, the team creates a tiny lattice of tightly-packed spheres. Metal is used to fill in the space around the spheres, and then the whole thing is melted to leave a sponge-like 3D scaffold. Next, a process called electropolishing uniformly etches away the surface of the scaffold to enlarge the pores and make an open framework.

Finally, the frame is coated with a thin film of active material. The resulting material allows the lithium ions to move rapidly, with high electrical conductivity. It can be packed in to any shape or material, including traditional lithium-ion-style packs.

"We like that it's very universal", explains Braun. "This is not linked to one very specific kind of battery, but rather it's a new paradigm in thinking about a battery in three dimensions for enhancing properties."

Other uses include high-powered lasers, military packs and defibrillators that don't need time to power up before or between pulses.

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Better Batteries. New technology improves both energy capacity and charge rate in rechargeable batteries

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.

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.

More Info >> http://www.northwest...nergy-kung.html

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Lithium-ion batteries could hold up to 10 times as much energy per cell if silicon anodes were used instead of graphite ones. But manufacturers don't use silicon because such anodes degrade quickly as the battery is charged and discharged.

Researchers at the Georgia Institute of Technology and Clemson University think they might have found the ingredient that will make silicon anodes work—a common binding agent and food additive derived from algae and used in many household products. They say this material could not only make lithium-ion batteries more efficient, but also cleaner and cheaper to manufacture.

Lithium-ion batteries store energy by accumulating ions at the anode; during use, these ions migrate, via an electrolyte, to the cathode. The anodes are typically made by mixing an electroactive graphite powder with a polymer binder—typically polyvinylidene fluoride (PVDF)—dissolved in a solvent called NMP. The resulting slurry is spread on the metal foil used to collect electrical current, and dried.

If silicon particles are used as the basis of the electroactive powder, the battery's anode can hold more ions. But silicon particles swell as the battery is charged, increasing in volume up to four times their original size. This swelling causes cracks in the PVDF binder, damaging the anode. In research published today by Science, the Georgia Tech and Clemson scientists show that when alginate is used instead of PVDF, the anode can swell and the binder won't crack. This allows researchers to create a stable silicon anode that has, so far, been demonstrated to have eight times the capacity of the best graphite-based anodes.

The polymer alginate is made from brown algae, including the type which forms forests of giant kelp. It is already widely used as a gelling agent and a food additive. Initially, the researchers thought to replace PVDF with a combination of several different materials. Then, on theoretical grounds, they realized that a polymer with just the right kind of uniform structure could do all the things the binder was supposed to do, including providing good structural support while not chemically reacting with the electrolyte.

Gleb Yushin, one of the researchers and director of the Center for Nanostructured Materials for Energy Storage at Georgia Tech, says the team realized that some synthetic polymers, derived from plant cellulose, have structures that were close to what was needed, but weren't uniform enough. So the team began looking at aquatic plants. Says Yushin: "We thought that there might already be a polymer [we could use], because aquatic plants—especially those in seawater—are immersed in an electrolyte," and so would have evolved to prevent unwanted reactions. They came across alginate, which can be extracted by boiling kelp in soda water, and which has the uniform structure required.

Another advantage of alginate over PVDF is that, during anode manufacture, alginate can be dissolved in water, eliminating the need for NMP, potentially making for a cleaner manufacturing process. The researchers believe the binder could be integrated into existing anode manufacturing systems simply by swapping the PVDF and NMP supplies for alginate and water. The alginate could also be used to improve the performance of graphite-based anodes, allowing more charge and discharge cycles over the battery's lifetime.

The full potential of a silicon anode can't be exploited until researchers develop a matching cathode capable of handling the same amount of lithium ions. But even with existing cathodes, alginate-silicon anodes could increase the capacity of lithium-ion batteries by 30 to 40 percent, according to Yushin.

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I feel that such batteries will be prohibitively expensive when they are launched commercially, given the huge R&D that has gone behind the making. As these will be pioneers with thousands of patents to protect copying (this is the part I'm absolutely sure of), economies of scale will never apply.

Our only hope is our Chinese brothers to manufacture effective "originals" as soon as the product goes to market.

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