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 Sandia National Laboratories researcher Jianyu Huang.
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 Department of Energy research facility jointly operated by Sandia and Los Alamos national laboratories.
Says Huang of the work, reported in the Dec. 10 issue of the journal Science, “This experiment enables us to study the charging and discharging of a battery 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 in power and energy density over bulk electrodes, 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 Huang, “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 do use nanomaterials as anodes, but in bulk rather than individually — a process, Huang says, that resembles “looking at a forest and trying to understand the behavior of an individual tree.”
The tiny battery created by Huang and co-workers 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 may shorten battery life. “Manufacturers should take account of this elongation in their battery design,” Huang said. (The common belief of workers in the field has been that batteries swell across their diameter, not longitudinally.)
Huang’s group found this flaw 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 high density of mobile dislocations cause the nanowire to bend and wiggle as the front progresses. The web of dislocations is caused by lithium penetration of the crystalline lattice. “These observations prove that nanowires can sustain large stress (>10 GPa) induced by lithiation without breaking, indicating that nanowires are very good candidates for battery electrodes,” said Huang.
“Our observations — which initially surprised us — tell battery researchers how these dislocations are generated, how they evolve during charging, and offer guidance in how to mitigate them,” Huang said. “This is the closest view to what’s happening during charging of a battery that researcher 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, Huang said. “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 Sandia co-author John Sullivan 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, Huang said.
A picoampere is a millionth of a microampere. A microampere is a millionth of an ampere.
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, Huang said.
“The methodology that we developed should stimulate extensive real-time studies of the microscopic processes in batteries and lead to a more complete understanding of the mechanisms governing battery performance and reliability,” he said. “Our experiments also 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.”
Other researchers contributing to this work include Xiao Hua Liu, Nicholas Hudak, Arunkumar Subramanian and Hong You Fan, all of Sandia; 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 the Department of Energy’s Office of Science through the Center for Integrated Nanotechnologies and the Energy Frontier Research Centers program.
Sandia National Laboratories is a multiprogram laboratory operated and managed by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.
Sandia news media contact: Neal Singer, firstname.lastname@example.org (505) 845-7078
Neal Singer | EurekAlert!
Patented nanostructure for solar cells: Rough optics, smooth surface
18.09.2018 | Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
With Gallium Nitride for a Powerful 5G Cellular Network - EU project “5G GaN2” started
17.09.2018 | Fraunhofer-Institut für Angewandte Festkörperphysik IAF
The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.
This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.
Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of...
Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.
"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...
A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.
Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...
Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.
An international team of researchers has mapped Nemo's genome, providing the research community with an invaluable resource to decode the response of fish to...
21.09.2018 | Event News
03.09.2018 | Event News
27.08.2018 | Event News
21.09.2018 | Physics and Astronomy
21.09.2018 | Life Sciences
21.09.2018 | Event News