Stanford's nanowire battery leapfrogs Li-ion

 

Stanford claims its latest advances in silicon nanowires have it building batteries with 10 times the capacity of existing Li-ion cells. Apparently people have been trying to stuff silicon -- which has a much higher capacity than existing materials -- into a battery for decades, but since it swells when charged with positively charged lithium and shrinks during use, the silicon has a tendency to "pulverize." Who knew batteries could be so dramatic? Oh, right. The advancement at Stanford, led by Yi Cui, builds the battery in the form of silicon nanowires, giving the silicon room to grow and shrink without damage. A patent is being filed, and Yi Cui is already considering forming a company or licensing the tech to a manufacturer.

 

   

Stanford wants to roll its own paper batteries

 

It was only a couple of months ago that MIT was wooing us with the energy-preserving properties of carbon nanotubes, and in a classic act of oneupmanship Stanford has now come out and demonstrated paper batteries, which work thanks to a carbon nanotube and silver nanowire "ink." We've seen this idea before, but the ability to just douse a sheet of paper in the proper magical goo and make a battery out of it is as new as it is mindblowing. Battery weight can, as a result, be reduced by 20 percent, and the fast energy discharge of this technology lends itself to utilization in electric vehicles. The video after the break should enlighten and thrill you in equal measures.                

World's smallest battery uses a single nanowire, plant-eating virus could improve Li-ion cells tenfold

When it comes to building better batteries, building electrodes with greater surface area is key, and scientists are looking to exotic methods to attract the tiny particles they need. We've already seen graphene and carbon nanotubes soak up those electrons, but the University of Maryland has another idea -- they're using the Tobacco mosaic virus (TMV) to generate usable patterns of nanorods on the surface of existing metal electrodes. By simply modifying the germ and letting it do its thing, then coating the surface with a conductive film, they're generating ten times the energy capacity of a standard lithium-ion battery while simultaneously rendering the nasty vegetarian bug inert.

Meanwhile, the Center for Integrated Nanotechnologies (CINT) at Sandia Labs was more curious how these tiny charges actually work without confusing the forest for the trees, so to speak, so a team of scientists set about constructing the world's smallest battery. Using a single tin dioxide nanowire as anode, a chunk of lithium cobalt dioxide as cathode, and piping some liquid electrolyte in between, they took a microscopic video of the charging process. See it in all its grey, goopy glory right after the break.  

 

   

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Via: TG Daily Source: PhysOrg, EurekaAlert

Researchers find weak point in lithium-ion batteries, suggest better nanowires could be the answer

 

We've seen countless attempts to build a better lithium-ion battery, but there's been far fewer research efforts devoted solely to figuring out why lithium-ion batteries don't last longer. A team of scientists at the Pacific Northwest National Laboratory have been doing just that, however, and they're now sharing some of their findings. The main culprit, they say, are the nano-sized wires made of bulk tin oxide used in the batteries, which can expand and deform considerably over time, eventually rendering the battery useless. What's more, while the research was focused primarily on examining the cause of battery aging, the researchers do naturally have a few suggestions on how to improve them -- namely, to replace those wires made of bulk tin oxide with finer tin oxide nanowires. As lead scientist Chongmin Wang explains, that would effectively amount to winding together "thinner wires rather than making one thick rope," which is of course easier said than done. Head on past the break for the complete press release.

 

Charging makes nano-sized electrodes swell, elongate and spiral

December 09, 2010

High-resolution video shows how batteries wear out over time

RICHLAND, Wash. – New high resolution images of electrode wires made from materials used in rechargeable lithium ion batteries shows them contorting as they become charged with electricity. The thin, nano-sized wires writhe and fatten as lithium ions flow in during charging, according to a paper in this week's issue of the journal Science. The work suggests how rechargeable batteries eventually give out and might offer insights for building better batteries.

Battery developers know that recharging and using lithium batteries over and over damages the electrode materials, but these images at nanometer scale offer a real-life glimpse into how. Thin wires of tin oxide, which serve as the negative electrode, fatten by a third and stretch twice as long due to lithium ions coursing in. In addition, the lithium ions change the tin oxide from a neatly arranged crystal to an amorphous glassy material.

"Nanowires of tin oxide were able to withstand the deformations associated with electrical flow better than bulk tin oxide, which is a brittle ceramic," said Chongmin Wang, a materials scientist at the Department of Energy's Pacific Northwest National Laboratory. "It reminds me of making a rope from steel - you wind together thinner wires rather than making one thick rope."

In one of the videos, shown here, the nanowire appears like a straw, while the lithium ions seem like a beverage being sucked up through it. Repeated shape changes could damage the electrode materials by introducing tiny defects that accumulate over time.

Chasing Electrons

In previous work at DOE's Environmental Molecular Sciences Laboratory on the PNNL campus, Wang, PNNL chemist Wu Xu and other colleagues succeeded in taking a snapshot of a larger nanowire of about one micrometer - or one-hundredth the width of a human hair - that had been partially charged. But the experimental set-up didn't show charging in action.

To view the dynamics of an electrode being charged, Wang and Xu teamed up with Jianyu Huang at DOE's Center for Integrated Nanotechnologies at Sandia National Laboratories in New Mexico and others. The team used a specially outfitted transmission electron microscope to set up a miniature battery. This instrument allowed them to image smaller wires of about 200 nanometers in diameter (about a fifth the width of the previous nanowires) while charging it.

Rechargeable lithium ion batteries work because lithium ions love electrons. Positively charged lithium ions normally hang out in the positive electrode, where a metal oxide shares its electrons with lithium. But charging a battery pumps free electrons into the negative electrode, which sits across a lake of electrolytes through which lithium ions can swim but electrons can't. The lithium desires the electrons on the negative side of the lake more than the electrons it shares with the metal oxide on the positive side. So lithium ions flow from the positive to the negative electrode, pairing up with free electrons there.

But electrons are fickle. Using a battery in a device allows the electrons to slip out of the negative electrode, leaving the lithium ions behind. So without free electron companions, the lithium ions return to the positive electrode and the metal oxide's embrace.

Wang's miniature battery included a positive electrode of lithium cobalt oxide and a negative electrode made from thin nanowires of tin oxide. Between the two electrodes, an electrolyte provided a conduit for lithium ions and a barrier for electrons. The electrolyte was specially designed to withstand the conditions in the microscope.

When the team charged the miniature battery at a constant voltage, lithium ions wicked up through the tin oxide wire, drawn by the electrons at the negative electrode. The wire fattened and lengthened by about 250 percent in total volume, and twisted like a snake.

In addition, the microscopy showed that the wire started out in a crystalline form. But the lithium ions changed the tin oxide to a glassy material, in which atoms are arranged more randomly than in a crystal. The researchers concluded the amount of deformation occurring during charging and use might wear down battery materials after a while. Even so, the tin oxide appeared to fare better as a nanowire than in its larger, bulk form.

"We think this work will stimulate new thinking for energy storage in general," said Wang. "This is just the beginning, and we hope with continued work it will show us how to design a better battery."

Future work will include imaging what happens when such a miniature battery is repeatedly charged and discharged. When a battery gets used, the lithium ions must run back through the tin oxide wire and across the electrolyte to the positive electrode. How much structural damage the receding lithium leaves in its wake will help researchers understand why rechargeable batteries stop working after being recharged so many times.

The researchers would also like to develop a fully functioning nano-sized rechargeable battery.

Reference: Jian Yu Huang, Li Zhong, Chong Min Wang, John P. Sullivan, Wu Xu, Li Qiang Zhang, Scott X. Mao, Nicholas S. Hudak, Xiao Hua Liu, Arunkumar Subramanian, Hong You Fan, Liang Qi, Akihiro Kushima, Ju Li, In situ observation of the electrochemical lithiation of a single SnO2 nanowire electrode, Dec. 10, 2010, Science, DOI 10.1126/science.1195628.

This work was supported by EMSL and the Department of Energy Office of Science.

Tags: Energy, Fundamental Science, EMSL, Batteries

EMSL, the Environmental Molecular Sciences Laboratory, is a national scientific user facility sponsored by the Department of Energy's Office of Science, Biological and Environmental Research program that is located at Pacific Northwest National Laboratory. EMSL offers an open, collaborative environment for scientific discovery to researchers around the world. EMSL's technical experts and suite of custom and advanced instruments are unmatched. Its integrated computational and experimental capabilities enable researchers to realize fundamental scientific insights and create new technologies. Follow EMSL on Facebook.

Pacific Northwest National Laboratory is a Department of Energy Office of Science national laboratory where interdisciplinary teams advance science and technology and deliver solutions to America's most intractable problems in energy, the environment and national security. PNNL employs 4,900 staff, has an annual budget of nearly $1.1 billion, and has been managed by Ohio-based Battelle since the lab's inception in 1965. Follow PNNL on Facebook, LinkedIn and Twitter.

  

  

Via: Autoblog Green Source: PNNL

USC battery wields silicon nanowires to hold triple the energy, charge in 10 minutes

 

There's no shortage of attempts to build a better battery, usually with a few caveats. USC may have ticked all the right checkboxes with its latest discovery, however. Its use of porous, flexible silicon nanowires for the anodes in a lithium-ion battery delivers the high capacity, fast recharging and low costs that come with silicon, but without the fragility of earlier attempts relying on simpler silicon plates. In practice, the battery could deliver the best of all worlds. Triple the capacity of today's batteries? Full recharges in 10 minutes? More than 2,000 charging cycles? Check. It all sounds a bit fantastical, but USC does see real-world use on the horizon. Researchers estimate that there should be products with silicon-equipped lithium-ion packs inside of two to three years, which isn't long to wait if the invention saves us from constantly hunting for the nearest wall outlet.

 

   

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Via: Gizmodo Source: USC