By Neal Singer
A benchtop version of the world’s smallest battery — its anode a single nanowire one seven-thousandth the thickness of a human hair —has been created by a team led by Jianyu Huang (1132).
To better study the anode’s characteristics, the tiny rechargeable, lithium-based battery was formed inside a transmission electron microscope (TEM) at the Center for Integrated Nanotechnologies (CINT), a DOE research facility jointly operated by Sandia and Los Alamos national laboratories.
“These are the first controlled measurements of the growth of magneto-Rayleigh-Taylor [MRT] instabilities in fast Z-pinches,” says project lead Daniel Sinars (1643).
Says Jianyu of the work, reported in the Dec. 10 Science, “This experiment enabled us to study the charging and discharging of a nanobattery in real time and at atomic-scale resolution, thus enlarging our understanding of the fundamental mechanisms by which batteries work.”
Because nanowire-based materials in lithium ion batteries offer the potential for significant improvements over bulk electrodes in power and energy density, more stringent investigations of their operating properties should improve new generations of plug-in hybrid electric vehicles, laptops, and cell phones.
“What motivated our work,” says Jianyu, “is that lithium ion batteries [LIB] have very important applications, but the low energy and power densities of current LIBs cannot meet the demand. To improve performance, we wanted to understand LIBs from the bottom up, and we thought in-situ TEM could bring new insights to the problem.”
Battery research groups around the world use nanomaterials as anodes, but in bulk rather than individually — a process, Jianyu says, that resembles “looking at a forest to try to understand the behavior of an individual tree.”
Observing change in atomic structure
The Sandia-led design consists of a single tin oxide nanowire anode 100 nanometers in diameter and 10 micrometers long, a bulk lithium cobalt oxide cathode three millimeters long, and an ionic liquid electrolyte. The device offers the ability to directly observe change in atomic structure during charging and discharging of the individual “trees.”
An unexpected find of the researchers was that the tin oxide nanowire rod nearly doubles in length during charging — far more than its diameter increases — a fact that could help avoid short circuits that shorten battery life. “Manufacturers should take account of this elongation in their battery design,” Jianyu says. (The common belief of workers in the field had been that batteries swell across their diameter, not longitudinally.)
Jianyu’s group found this behavior by following the progression of the lithium ions as they travel along the nanowire and create what researchers christened the “Medusa front” — an area where the high density of mobile dislocations causes the nanowire to bend and wiggle as the front progresses. The web of dislocations is caused by lithium penetration of the crystalline
“These observations also prove that nanowires can sustain large stress — greater than 10 GPa [gigapascals] — induced by lithiation without breaking, indicating that nanowires are very good candidates for battery electrodes,” says Jianyu.
Still, the researchers were surprised to see the lengthwise elongations and the dislocations. Says Jianyu, “No one had ever seen either before. But our observations tell battery researchers how they are generated, how they evolve during charging, and offer guidance in how to mitigate them. This is the closest view to what’s happening during charging of a battery that researchers have achieved so far.”
Lithiation-induced volume expansion, plasticity, and pulverization of electrode materials are the major mechanical defects that plague the performance and lifetime of high-capacity anodes in lithium-ion batteries, Jianyu says. “So our observations of structural kinetics and amorphization [the change from normal crystalline structure] have important implications for high-energy battery design and in mitigating battery failure.”
The electronic noise level generated from the researchers’ measurement system was too high to read electrical currents, but co-author John Sullivan (1132) estimated a current level of a picoampere flowing in the nanowire during charging and discharging. The nanowire was charged to a potential of about 3.5 volts, Jianyu says. A picoampere is a millionth of a microampere. A microampere is a millionth of an ampere.
Functioning in a vacuum environment
The reason that atomic-scale examination of the charging and discharging process of a single nanowire had not been possible was because the high vacuum in a TEM made it difficult to use a liquid electrolyte. Part of the Huang group’s achievement was to demonstrate that a low-vapor-pressure ionic liquid — essentially, molten salt — could function in the vacuum environment.
Although the work was carried out using tin oxide (SnO2) nanowires, the experiments can be extended to other materials systems, either for cathode or anode studies, Jianyu says.
“Our experiments lay a foundation for in-situ studies of electrochemical reactions, and will have broad impact in energy storage, corrosion, electrodeposition, and general chemical synthesis research field as well,” he predicts.
Other researchers contributing to this work include Xiao Hua Liu, Nicholas Hudak, Arunkumar Subramanian (all 1132), and Hongyou Fan (1813); Li Zhong, Scott Mao, and Li Qiang Zhang of the University of Pittsburgh; Chong Min Wang and Wu Xu of Pacific Northwest National Laboratory; and Liang Qi, Akihiro Kushima, and Ju Li of the University of Pennsylvania.
Funding came from Sandia’s Laboratory Directed Research and Development Office and DOE’s Office of Science through CINT and the Energy Frontier Research Centers program. -- Neal Singer
By Mike Janes
Two projects led by researchers at Sandia’s Combustion Research Facility (CRF) and Computer Sciences and Information Systems Center have been awarded 65 million hours on two DOE supercomputers through DOE’s Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. The research projects utilize two world-leading supercomputers with a computational capacity roughly equal to 135,000 quad-core laptops.
“The Department of Energy’s supercomputers provide an enormous competitive advantage for the United States,” Energy Secretary Steven Chu said when the awards were announced. “This is a great example of how investments in innovation can help lead the way to new industries, new jobs, and new opportunities for America to succeed in the global marketplace.”
Awarded on a competitive basis, many of the new and continuing INCITE projects aim to further renewable energy solutions and advance understanding of the environmental impacts of energy use. The program, open to all scientists, is supported by DOE’s Office of Science and managed by the DOE Leadership Computing Facilities at Argonne and Oak Ridge national laboratories, which host some of the world’s fastest supercomputers.
INCITE projects could help speed the development of more efficient solar cells, lead to improvements in biofuel production, and help identify more effective medications to slow the progression of Parkinson’s disease.
This year’s INCITE awards are the largest-ever awards of the department’s supercomputing time. A total of 1.7 billion processor hours were granted to 57 innovative research projects that will use computer simulations to perform virtual experiments that in most cases would be impossible or impractical in the natural world.
Joe Oefelein (8351) is the principal investigator on “High-Fidelity Simulations for Advanced Engine Combustion Research,” with his colleague, Jackie Chen (also 8351), serving as co-investigator. Joe and Jackie were awarded 60 million hours on the Cray XT5 (“Jaguar”) machine at Oak Ridge National Laboratory.
Their project aims to provide new insights into the dynamics of turbulent combustion processes in internal combustion engines, and to maximize the collective benefits of those insights through collaborations among the researchers involved.
David Evensky (8966) is principal investigator for “Trace Collection for Simulation-Driven Co-design of Exascale Platforms and Codes.” Curtis Janssen (8953) serves as co-investigator. The project was awarded 5 million hours on the IBM Blue Gene/p (“Intrepid”) machine.
Their project focuses on “exascale” computing and is the validation part of a larger effort to help researchers co-design applications, runtimes, and systems for future exascale computing, considered the next great leap in size for computers.
A third Sandia researcher, Mark Taylor (1442), is participating in two other proposals that were granted 110 million and 35 million hours. Mark is a co-investigator on “Climate-Science Computational Development Team: The Climate End Station II,” led by the National Center for Atmospheric Research, and on “Numerical Study of Multiscale Coupling in Low-Aspect Ratio Rotating Stratified Turbulence,” led by Los Alamos National Laboratory. -- Mike Janes
Greg Nielson (1749-2) could have been annoyed by a caller who telephoned him by mistake, thinking he was a different former Truman Fellow, but instead Greg engaged the man in conversation, and a collaboration was born.
“It was a wrong number, but I heard he was from the solar group and he was looking for another Truman Fellow, so I gave him the name and then said, ‘Actually, I have this idea. It could be useful for solar power,’” Greg says.
Five years later, Greg, the caller, Vipin Gupta (6124), and more than two dozen other researchers developed tiny glitter-sized photovoltaic (PV) cells that could revolutionize the way solar energy is collected and used.
Nielson is among 15 Sandians who were honored with the first Up-and-Coming Innovator awards this year at the Innovation and Intellectual Property Celebration at the Albuquerque Museum. They were nominated by their directors for displaying enormous potential for innovation, entrepreneurial talent, and their ability to develop unique solutions to complex scientific challenges.
A laboratory that values innovation
Div. 1000 VP and Chief Technology Officer Steve Rottler, who spoke at the ceremony that also honored new patent holders and researchers who received copyrights and licenses, welcomed efforts to make innovation part of the culture at the Labs.
“What we want as a key characteristic of our culture, meaning the attitude and behaviors of everybody who works at Sandia, is valuing innovation. We want to have a work environment and we want to have a laboratory that values and expresses innovation in everything that it does,” Steve said during his speech.
Encouraging younger researchers to be innovative is part of that effort, says Mark Allen of Intellectual Property Management Alliances & Licensing Dept. (1931).
Director Gil Herrera (1700) says he nominated Greg because of his intellectual leadership and his ability to work well with people, to manage a project, and to keep a team of about 30 people together.
“The complexity of modern-day inventions requires somebody who can broadly understand the concept and the components of the invention, as modern inventions tend to be made from integrated systems,” Gil says. “Greg is an outstanding example of how you do innovation into the future, as he combines this systems-level vision with excellent leadership and teamwork.”
The tiny PV cells are fabricated using microelectronic and microelectromechanical systems (MEMS) techniques. They are expected to be less expensive and more efficient than current photovoltaic collectors.
Greg says he came up with the idea while talking with a friend, Mike Watts, a former Sandian who is now a professor at MIT. At the time, research had been done on how MEMS devices interacted with coherent light — for example, lasers — but the two researchers discussed looking into how MEMS devices interacted with incoherent light, like sunlight, Greg says.
Working at the boundaries
“At the time I started my PhD, I was realizing that working at the boundaries of MEMS, microsystems, and optics, there’s a lot of unexplored things there,” Greg says. “It’s really exciting because you are bringing these technologies together that are fairly new, so you can do things that just weren’t possible to do before. It’s fun. There’s a lot of creativity there.”
Because the solar cells are so small — about 20 microns thick — they are flexible, which has enormous advantages for manufacturing and efficiency.
Greg says his team is working on how to put solar glitter into products and hopes to create some functional demonstrations of solar glitter prototype systems, possibly within the next year.
Talking in his office, Greg pulls a container off the top of his desk that contains what looks like a bubble of oil with glitter inside it floating in water. Greg explains researchers are looking at self-assembled monolayers using different chemicals, so they can coat either the metal or the other face of the solar cell to orient the glitter in a certain direction.
“So basically you can get them sunny side up,” Greg says. “The reason this is cool is that we’re working to create a system where you use these very small solar cells as a sort of photovoltaic ink. We want to print them onto a flexible substrate or wherever we want, thousands at a time, like a Xerox copying process. We’ve made some progress down that path. We’ve done some things there that people have not done before.”
Working on self-assembly of cells
Greg says his team has been successful at working within the confines of current manufacturing techniques and improving the efficiency of the solar cells, but they are still working on the self-assembly of the cells.
Greg emphasizes that nearly 30 people worked on solar glitter, which has helped move the innovation along.
“Sandia is definitely a place where people are inclined to work together and that really does help,” Greg says. “You can come up with really great solutions in your own little area and that’s fantastic, but if you can bring together people from a variety of areas to come up with a solution, then that’s even more powerful.”
Greg first encountered Sandia as an undergraduate intern working with the Cubit Group, which works with an enabling technology for high-performance computer modeling and simulations. Rob Leland (1400) was his manager at the time and helped him consider different options for graduate school, Greg says.
After getting his bachelor’s degree in mechanical engineering from Utah State University, Greg went to MIT, where he received a master’s in mechanical engineering and a doctorate in mechanical engineering with a focus on optical microsystems.
One of the first Truman Fellows
Greg was one of two researchers to become the first Truman Fellows at Sandia in 2004. He worked on improving the energy efficiency and performance of optical MEMS switching, which would make the switches more appealing for applications in, for example, computing or telecommunications.
Greg says he came up with some ideas that led to faster switching using less power. The result was a switch that operates at 225 nanoseconds and needs 22 volts, and was about 10 times faster than the fastest switch on the market at the time.
After the Truman Fellowship, Greg became a member of technical staff in the same organization.
Asked whether he views himself as an entrepreneur, Greg says he enjoys creating new things and solving problems.
“Being able to spin Sandia’s technology out to companies, so that those things can be commercialized and benefit society, that’s great,” Greg says. “If at the end of my career, I had come up with some things that people find useful, I’d feel like I’d done good things.”