Scientists at ORNL used a miniature electrochemical liquid cell that is placed in a transmission electron microscope to study an enigmatic phenomenon in lithium-ion batteries called the solid electrolyte interphase, or SEI, as described in a study published in Chemical Communications.
A new in situ transmission electron microscopy technique enabled ORNL researchers to image the snowflake-like growth of the solid electrolyte interphase from a working battery electrode.
The SEI is a nanometer-scale film that forms on a battery’s negative electrode due to electrolyte decomposition. Scientists agree that the SEI’s formation and stability play key roles in controlling battery functionality. But after three decades of research in the battery field, details of the SEI’s dynamics, structure and chemistry during electrochemical cycling are still debated, stemming from inherent difficulties in studying battery electrode materials in their native liquid environment.
“We’ve used this novel in situ method to understand the dynamics of how this layer forms and evolves during battery operation,” said Raymond Unocic, ORNL R&D staff scientist.
Battery researchers typically study the structure and chemistry of the SEI through “post-mortem” methods, in which a cycled battery is disassembled, dried and then analyzed through a number of characterization methods.
“This is problematic because of the air and moisture sensitivity of the SEI, and the ease by which environmental exposure can modify its structure and chemistry.” Unocic said.
The ORNL researchers formed a miniature electrochemical cell by enclosing battery electrolyte between two silicon microchip devices that contain microfabricated electrodes and silicon nitride viewing membranes. The transparent “windows” seal the highly volatile battery electrolyte from the microscope’s vacuum environment and allow the electron beam to pass through the liquid, which facilitates imaging of the electrochemical reaction products as they form.
To reproduce a battery charging cycle, the researchers applied a potential at the working electrode and monitored the resulting changes in current. The most striking result, said the researchers, was capturing an unprecedented view of SEI evolution during potential cycling. The technique is able to image the formation of tiny crystalline particles only one billionth of a meter in size.
“As we start to sweep the potential, we didn’t initially observe anything,” said lead author Robert Sacci, a postdoctoral research fellow with ORNL’s FIRST Energy Frontier Research Center. “Then we started seeing shadows -- presumably polymeric SEI -- forming into a dendritic pattern. It looks like a snowflake forming from the electrode.” Watch a video of the process at http://www.youtube.com/watch?v=OHrlFNB-Q9Y.
The researchers plan to build on this initial proof-of-principle study to better understand the factors behind the SEI’s formation, which could ultimately help improve battery performance, capacity, and safety at the device level.
“Tailoring the SEI’s structure and chemistry to maximize battery capabilities appears to be a delicate balancing act,” Unocic said. “When you cycle a real battery, the interphase structure can form, break, and reform again, depending on how thick the layer grows, so we need to look at improving its structural stability. But at the same time, we have to think about making the interphase more efficient for lithium ion transport. This study brings us one step closer to understanding SEI formation and growth.”
Next steps for the researchers include applying their technique to study different types of battery electrodes and electrolytes and other energy storage systems including fuel cells and supercapacitors.
Coauthors are ORNL’s Raymond Unocic, Robert Sacci, Nancy Dudney and Karren More; and Pacific Northwest National Laboratory’s Lucas Parent, Ilke Arslan, Nigel Browning. The study is published as “Direct Visualization of Initial SEI Morphology and Growth Kinetics During Lithium Deposition by in situ Electrochemical Transmission Electron Microscopy.”
The research was supported by the DOE’s Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program, by the Fluid Interface Reactions Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the Office of Basic Energy Sciences, and as part of a user proposal at ORNL’s Center for Nanophase Materials Sciences. Parts of the work were supported by the laboratory directed research and development program at Pacific Northwest National Laboratory and the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by BES-DOE.
Part of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at ORNL by the Scientific User Facilities Division in DOE’s Office of Basic Energy Sciences. CNMS is one of the five DOE Nanoscale Science Research Centers supported by the DOE Office of Science, premier national user facilities for interdisciplinary research at the nanoscale. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE's Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge and Sandia and Los Alamos national laboratories. For more information about the DOE NSRCs, please visit http://science.energy.gov/bes/suf/user-facilities/nanoscale-science-research-centers/.
UT-Battelle manages ORNL for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of the time.
Molecular evolution: How the building blocks of life may form in space
26.04.2018 | American Institute of Physics
Multifunctional bacterial microswimmer able to deliver cargo and destroy itself
26.04.2018 | Max-Planck-Institut für Intelligente Systeme
Magnetic resonance imaging, or MRI, is a widely used medical tool for taking pictures of the insides of our body. One way to make MRI scans easier to read is...
At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.
Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...
Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.
Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
26.04.2018 | Power and Electrical Engineering
26.04.2018 | Life Sciences
26.04.2018 | Power and Electrical Engineering