(Press-News.org) 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 material like glass, 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 Li6, In situ observation of the electrochemical lithiation of a single SnO2 nanowire electrode, Dec. 10, 2010, Science, DOI 10.1126/science.1195628 (http://www.sciencemag.org/).
This work was supported by EMSL and the Department of Energy Office of Science.
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, national security and the environment. 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.
EMSL, the Environmental Molecular Sciences Laboratory located at Pacific Northwest National Laboratory, is a national scientific user facility sponsored by the Department of Energy's Office of Science, Biological and Environmental Research program. 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. EMSL's Facebook page.
END
Spearheaded by the University of Manchester's Jodrell Bank Observatory and funded by the Science and Technology Facilities Council, the e-MERLIN telescope will allow astronomers to address key questions relating to the origin and evolution of galaxies, stars and planets.
To demonstrate its capabilities, University of Manchester astronomers turned the new telescope array toward the "Double Quasar". This enigmatic object, first discovered by Jodrell Bank, is a famous example of Einstein's theory of gravity in action.
The new image shows how the light from a quasar billions ...
BOSTON, Mass. (December 9, 2010)—A team of researchers from Harvard Medical School, Brigham and Women's Hospital, and Massachusetts General Hospital, with others from the United States and Haiti, has determined that the strain of cholera erupting in Haiti matches bacterial samples from South Asia and not those from Latin America. The scientists conclude that the cholera bacterial strain introduced into Haiti probably came from an infected human, contaminated food or other item from outside of Latin America. It is highly unlikely, they say, that the outbreak was triggered ...
The technique, which they describe in the journal Science, involves rearranging the holes left by missing atoms to tune the properties of dopants – the chemical impurities that give the semiconductors in computer chips their special properties.
Though the technique is currently limited to the laboratory, it could prove valuable to industry in the future, as the continued miniaturization of cell phone and computer chips makes the performance of individual atoms in a semiconductor more important.
"The effect we discovered is probably already going on inside the devices ...
VIDEO:
Neurologists finally have an answer to one of the most important questions about Alzheimer's disease: In a study published in Science Express, researchers show that rising brain levels of a...
Click here for more information.
Neurologists finally have an answer to one of the most important questions about Alzheimer's disease: Do rising brain levels of a plaque-forming substance mean patients are making more of it or that they can no longer clear it from their brains ...
In Alzheimer's disease, a protein fragment called beta-amyloid accumulates at abnormally high levels in the brain. Now researchers funded by the National Institutes of Health have found that in the most common, late-onset form of Alzheimer's disease, beta-amyloid is produced in the brain at a normal rate but is not cleared, or removed from the brain, efficiently. In addition to improving the understanding of what pathways are most important in development of Alzheimer's pathology, these findings may one day lead to improved biomarker measures for early diagnosis as well ...
Silencing the TLR4 gene can stop the process which may lead to cardiovascular disease in diabetic patients. Researchers writing in BioMed Central's open access Journal of Translational Medicine carried out a series of in vitro tests which demonstrated that TLR4 plays a critical role in hyperglycaemic cardiac apoptosis, and that silencing the gene using specific small interfering RNA (siRNA) can prevent it.
Wei-Ping Min, from the University of Western Ontario, Canada, worked with a team of researchers to perform the tests in cells taken from diabetic mice. He said, "We ...
Research, led by the University of Warwick, The Sainsbury Laboratory, and Virginia Polytechnic Institute and State University (Virginia Tech), has sequenced the genome of a plant disease causing organism revealing that it acts like a "stealth bomber of plant pathogens". The research has uncovered the tactics used to sneak past the plant's immune defences. That same discovery also provides tools for researchers to identify the components of the plant immune system and devise new ways to prevent disease.
The research at the University of Warwick, the Sainsbury Laboratory ...
Cancer researchers have identified six gene markers present in early stage non-small cell lung cancer (NSCLC) that show promise in helping oncologists better identify which tumors will relapse after curative surgery, according to a study presented at the 2010 Chicago Multidisciplinary Symposium in Thoracic Oncology. This symposium is sponsored by the American Society for Radiation Oncology (ASTRO), the American Society of Clinical Oncology (ASCO), the International Association for the Study of Lung Cancer (ISLAC) and the University of Chicago.
Lung cancer is the leading ...
ANN ARBOR, Mich. — The cocktail of hormones cascading through depressed mothers' bodies may play an important role in the development of their unborn children's brains.
A higher level of depression in mothers during pregnancy was associated with higher levels of stress hormones in their children at birth, as well as with other neurological and behavioral differences, a University of Michigan-led study found.
"The two possibilities are that they are either more sensitive to stress and respond more vigorously to it, or that they are less able to shut down their stress ...
New data shows that people exposed to the mineral erionite found in the gravel of road materials in North Dakota may be at significantly increased risk of developing mesothelioma, a type of lung cancer most often associated with asbestos exposure, according to research presented at the 2010 Chicago Multidisciplinary Symposium in Thoracic Oncology. This symposium is sponsored by the American Society for Radiation Oncology (ASTRO), the American Society of Clinical Oncology (ASCO), the International Association for the Study of Lung Cancer (ISLAC) and The University of Chicago.
Erionite ...
