Berkeley Lab – DOE – Argonne – “Holy Grail” for Batteries: Solid-State Magnesium Battery a Big Step Closer


 

Berkeley Lab leads discovery of the fastest magnesium-ion solid-state conductor to date.

 

A team of Department of Energy (DOE) scientists at the Joint Center for Energy Storage Research (JCESR) has discovered the fastest magnesium-ion solid-state conductor, a major step towards making solid-state magnesium-ion batteries that are both energy dense and safe.

Argonne scientist Baris Key, shown on left at work in his nuclear magnetic resonance lab, worked with researchers at Berkeley Lab on the discovery of the fastest ever magnesium-ion solid-state conductor. (Credit: Argonne National Laboratory)

The electrolyte, which carries charge back and forth between the battery’s cathode and anode, is a liquid in all commercial batteries, which makes them potentially flammable, especially in lithium-ion batteries. A solid-state conductor, which has the potential to become an electrolyte, would be far more fire-resistant.

Researchers at DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Argonne National Laboratory were working on a magnesium battery, which offers higher energy density than lithium, but were stymied by the dearth of good options for a liquid electrolyte, most of which tend to be corrosive against other parts of the battery. “Magnesium is such a new technology, it doesn’t have any good liquid electrolytes,” said Gerbrand Ceder, a Berkeley Lab Senior Faculty Scientist. “We thought, why not leapfrog and make a solid-state electrolyte?”

The material they came up with, magnesium scandium selenide spinel, has magnesium mobility comparable to solid-state electrolytes for lithium batteries. Their findings were reported in Nature Communications in a paper titled, “High magnesium mobility in ternary spinel chalcogenides.”JCESR, a DOE Innovation Hub, sponsored the study, and the lead authors are Pieremanuele Canepa and Shou-Hang Bo, postdoctoral fellows at Berkeley Lab.

“With the help of a concerted effort bringing together computational materials science methodologies, synthesis, and a variety of characterization techniques, we have identified a new class of solid conductors that can transport magnesium ions at unprecedented speed,” Canepa said.

Collaboration with MIT and Argonne

The research team also included scientists at MIT, who provided computational resources, and Argonne, who provided key experimental confirmation of the magnesium scandium selenide spinel material to document its structure and function.

Co-author Baris Key, a research chemist at Argonne, conducted nuclear magnetic resonance (NMR) spectroscopy experiments. These tests were among the first steps to experimentally prove that magnesium ions could move through the material as rapidly as the theoretical studies had predicted.

“It was crucial to confirm the fast magnesium hopping experimentally. It is not often that the theory and the experiment agree closely with each other,” Key said. “The solid state NMR experiments for this chemistry were very challenging and would not be possible without dedicated resources and a funding source such as JCESR.

As we’ve shown in this study, an in-depth understanding of short- and long-range structure and ion dynamics will be the key for magnesium ion battery research.”

NMR is akin to magnetic resonance imaging (MRI), which is routinely used in medical settings, where it shows hydrogen atoms of water in human muscles, nerves, fatty tissue, and other biological substances. But researchers can also tune NMR frequency to detect other elements, including the lithium or magnesium ions that are found in battery materials.

The NMR data from the magnesium scandium selenide material, however, involved material of unknown structure with complex properties, making them challenging to interpret.

Canepa noted the challenges of testing materials that are so new. “Protocols are basically non-existent,” he said. “These findings were only possible by combining a multi-technique approach (solid-state NMR and synchrotron measurements at Argonne) in addition to conventional electrochemical characterization.”

Doing the impossible

The team plans to do further work to use the conductor in a battery. “This probably has a long way to go before you can make a battery out of it, but it’s the first demonstration you can make solid-state materials with really good magnesium mobility through it,” Ceder said. “Magnesium is thought to move slowly in most solids, so nobody thought this would be possible.”

Additionally, the research identified two related fundamental phenomena that could significantly affect the development of magnesium solid electrolytes in the near future, namely, the role of anti-site defects and the interplay of electronic and magnesium conductivity, both published recently in Chemistry of Materials.

Bo, now an assistant professor at Shanghai Jiao Tong University, said the discovery could have a dramatic effect on the energy landscape. “This work brought together a great team of scientists from various scientific disciplines, and took the first stab at the formidable challenge of building a solid-state magnesium battery,” he said. “Although currently in its infancy, this emerging technology may have a transformative impact on energy storage in the near future.”

Gopalakrishnan Sai Gautam, another co-author who was an affiliate at Berkeley Lab and is now at Princeton, said the team approach made possible by a DOE hub such as JCESR was critical. “The work shows the importance of using a variety of theoretical and experimental techniques in a highly collaborative environment to make important fundamental discoveries,” he said.

Ceder was excited at the prospects for the finding but cautioned that work remains to be done. “There are enormous efforts in industry to make a solid-state battery. It’s the holy grail because you would have the ultimate safe battery. But we still have work to do. This material shows a small amount of electron leakage, which has to be removed before it can be used in a battery.”

Funding for the project was provided by the DOE Office of Science through the Joint Center for Energy Storage Research, a Department of Energy Innovation Hub. The Advanced Photon Source, a DOE Office of Science User Facility at Argonne, added vital data to the study regarding the structure of the solid conductor.

The National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility at Berkeley Lab, provided computing resources. Other co-authors on the paper are Juchaun Li of Berkeley Lab, William Richards and Yan Wang of MIT, and Tan Shi and Yaosen Tian of UC Berkeley.

# # #

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel Prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state, and municipal agencies to help them solve their specific problems, advance America’s scientific leadership, and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. 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 our time. For more information, please visit science.energy.gov.

The Joint Center for Energy Storage Research (JCESR), a DOE Energy Innovation Hub, is a major partnership that integrates researchers from many disciplines to overcome critical scientific and technical barriers and create new breakthrough energy storage technology. Led by the U.S. Department of Energy’s Argonne National Laboratory, partners include national leaders in science and engineering from academia, the private sector, and national laboratories. Their combined expertise spans the full range of the technology-development pipeline from basic research to prototype development to product engineering to market delivery.

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Improved Solar Cell Efficiency with New Polymer


PolymerSolarNew light has been shed on solar power generation using devices made with polymers, thanks to collaboration between scientists in the University of Chicago’s chemistry department, the Institute for Molecular Engineering and Argonne National Laboratory.

Researchers identified a new polymer—a type of large molecule that forms plastics and other familiar materials—that improved the efficiency of solar cells. The group also determined the method by which the polymer improved the cells’ efficiency. The polymer allows electrical charges to move more easily throughout the cell, boosting the production of electricity—a mechanism never before demonstrated in such devices.

“Polymer solar cells have great potential to provide low-cost, lightweight and flexible electronic devices to harvest solar energy,” said Luyao Lu, graduate student in chemistry and lead author of a paper describing the result, published online last month in the journal Nature Photonics.

Solar cells made from polymers are a popular topic of research due to their appealing properties, but researchers are still struggling to efficiently generate electrical power with these materials.

“The field is rather immature—it’s in the infancy stage,” said Luping Yu, professor in chemistry and fellow in the Institute for Molecular Engineering, who led the UChicago group carrying out the research.

The active regions of such solar cells are composed of a mixture of polymers that give and receive electrons to generate electrical current when exposed to light. The new polymer developed by Yu’s group, called PID2, improves the efficiency of electrical power generation by 15% when added to a standard polymer-fullerene mixture.

“Fullerene, a small carbon molecule, is one of the standard materials used in polymer solar cells,” Lu said. “Basically, in polymer solar cells we have a polymer as electron donor and fullerene as electron acceptor to allow charge separation.” In their work, the UChicago-Argonne researchers added another polymer into the device, resulting in solar cells with two polymers and one fullerene.

 

Luyao Lu, a graduate student in chemistry, works in the solar cell characterization facility of the University of Chicago’s Gordon Center for Integrative Science. Lu is the lead author of a Nature Photonics article describing the development of a new type of polymer solar cell that displays enhanced power conversion efficiency. Image: Andrew NellesLuyao Lu, a graduate student in chemistry, works in the solar cell characterization facility of the University of Chicago’s Gordon Center for Integrative Science. Lu is the lead author of a Nature Photonics article describing the development of a new type of polymer solar cell that displays enhanced power conversion efficiency. Image: Andrew Nelles

8.2% efficiency

The group achieved an efficiency of 8.2% when an optimal amount of PID2 was added—the highest ever for solar cells made up of two types of polymers with fullerene—and the result implies that even higher efficiencies could be possible with further work. The group is now working to push efficiencies toward 10%, a benchmark necessary for polymer solar cells to be viable for commercial application.

The result was remarkable not only because of the advance in technical capabilities, Yu noted, but also because PID2 enhanced the efficiency via a new method. The standard mechanism for improving efficiency with a third polymer is by increasing the absorption of light in the device. But in addition to that effect, the team found that when PID2 was added, charges were transported more easily between polymers and throughout the cell.

In order for a current to be generated by the solar cell, electrons must be transferred from polymer to fullerene within the device. But the difference between electron energy levels for the standard polymer-fullerene is large enough that electron transfer between them is difficult. PID2 has energy levels in between the other two, and acts as an intermediary in the process.

“It’s like a step,” Yu said. “When it’s too high, it’s hard to climb up, but if you put in the middle another step then you can easily walk up.”

Thanks to collaboration with Argonne, Yu and his group were also able to study the changes in structure of the polymer blend when PID2 was added, and show that these changes likewise improved the ability of charges to move throughout the cell, further improving the efficiency. The addition of PID2 caused the polymer blend to form fibers, which improve the mobility of electrons throughout the material. The fibers serve as a pathway to allow electrons to travel to the electrodes on the sides of the solar cell.

“It’s like you’re generating a street and somebody that’s traveling along the street can find a way to go from this end to another,” Yu said.

To reveal this structure, Wei Chen of the Materials Science Division at Argonne National Laboratory and the Institute for Molecular Engineering performed x-ray scattering studies using the Advanced Photon Source at Argonne and the Advanced Light Source at Lawrence Berkeley National Laboratory.

“Without that it’s hard to get insight about the structure,” Yu said, calling the collaboration with Argonne “crucial” to the work. “That benefits us tremendously,” he said.

Chen noted that “Working together, these groups represent a confluence of the best materials and the best expertise and tools to study them, to achieve progress beyond what could be achieved with independent efforts.”

“This knowledge will serve as a foundation from which to develop high-efficiency organic photovoltaic devices to meet the nation’s future energy needs,” Chen said.

Ternary blend polymer solar cells with enhanced power conversion efficiency

Source: Univ. of Chicago