Fluoride shuttle increases storage capacity: Researchers develop new concept for rechargeable batteries

 Karlsruhe Institute of Technology (KIT) researchers have developed a new concept for rechargeable batteries. Based on a fluoride shuttle -- the transfer of fluoride anions between the electrodes -- it promises to enhance the storage capacity reached by lithium-ion batteries by several factors. Operational safety is also increased, as it can be done without lithium.

The fluoride-ion battery is presented for the first time in the Journal of Materials Chemistry by Dr. Maximilian Fichtner and Dr. Munnangi Anji Reddy.

Lithium-ion batteries are applied widely, but their storage capacity is limited. In the future, battery systems of enhanced energy density will be needed for mobile applications in particular. Such batteries can store more energy at reduced weight. For this reason, KIT researchers are also conducting research into alternative systems. A completely new concept for secondary batteries based on metal fluorides was developed by Dr. Maximilian Fichtner, Head of the Energy Storage Systems Group, and Dr. Munnangi Anji Reddy at the KIT Institute of Nanotechnology (INT).

Metal fluorides may be applied as conversion materials in lithium-ion batteries. They also allow for lithium-free batteries with a fluoride-containing electrolyte, a metal anode, and metal fluoride cathode, which reach a much better storage capacity and possess improved safety properties. Instead of the lithium cation, the fluoride anion takes over charge transfer. At the cathode and anode, a metal fluoride is formed or reduced. "As several electrons per metal atom can be transferred, this concept allows to reach extraordinarily high energy densities -- up to ten times as high as those of conventional lithium-ion batteries," explains Dr. Maximilian Fichtner.

The KIT researchers are now working on the further development of material design and battery architecture in order to improve the initial capacity and cyclic stability of the fluoride-ion battery. Another challenge lies in the further development of the electrolyte: The solid electrolyte applied so far is suited for applications at elevated temperatures only. It is therefore aimed at finding a liquid electrolyte that is suited for use at room temperature.

Story Source:

The above story is reprinted from materials provided by Karlsruhe Institute of Technology.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

M. Anji Reddy, M. Fichtner. Batteries based on fluoride shuttle. Journal of Materials Chemistry, 2011; DOI: 10.1039/C1JM13535J

Argonne patents technology that increases safety of Li-ion batteries

Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory have patented a new, extremely stable, 4-volt redox shuttle molecule that provides overcharge protection for lithium-ion batteries containing lithium-iron-phosphate based cathodes across hundreds of charging cycles.

Overcharge is a major safety concern for Li-ion batteries because it could cause thermal runaway. Thermal runaway is a concern for large batteries—such as those used for transportation, satellite and storage applications—because they contain a large amount of active material.

"When a battery pack is being charged, each cell in the pack may have varying levels of charge," said Argonne materials scientist Khalil Amine, who leads the research group that developed the shuttle. "Overcharge generally occurs when a current is forced through a battery and the charge that is delivered exceeds the charge-storing capacity of the battery, which can damage the entire battery.” Modern, well-designed batteries prevent overcharge from occurring through the use of external battery monitoring and control systems that function both at the cell and battery level. This new material offers a tool for addressing some of the concerns associated with overcharge using an approach that functions inside each cell.

"The new redox shuttle, known as 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene or DBBB, works by halting the charging process of individual cells as they come to a full state of charge," Amine said. "Being able to discontinue the charging process on a cell-by-cell basis protects the entire battery pack by preventing individual cells from overcharging."

DBBB, which dissolves in the electrolyte, works by moving back and forth from the anode and cathode in place of the Li-ion, Amine explained. The shuttle technology achieved up to 300 cycled overcharges in the lab.

The shuttle is currently undergoing validation test by industry, and the results to date are very encouraging, he said.

Researchers in Argonne's Advanced Battery Materials Synthesis and Manufacturing Research & Development Program have already scaled up production of DBBB to 1.5 kilograms from the sub-gram amounts Amine's group required for bench-scale research and development (See related story). The larger amount of the redox shuttle material is needed by companies that want to test the material for possible commercialization.

The stability and repeated long-term overcharge cycling capability of this new shuttle molecule was demonstrated by Amine and his Argonne colleagues Zhengcheng Zhang, Lu Zhang and Wei Weng.

The redox shuttle is part of a suite of advanced battery materials developed by scientists at Argonne. This research was funded by the DOE Office of Energy Efficiency and Renewable Energy.

Provided by Argonne National Laboratory (news : web)

Blocking carbon dioxide fixation in bacteria increases biofuel production

 Reducing the ability of certain bacteria to fix carbon dioxide can greatly increase their production of hydrogen gas that can be used as a biofuel. Researchers from the University of Washington, Seattle, report their findings in the current issue of online journal mBio®.

"Hydrogen gas is a promising transportation fuel that can be used in hydrogen fuel cells to generate an electric current with water as the only waste product," says Caroline Harwood, who conducted the study with James McKinlay. "Phototrophic bacteria, like Rhodopseudomonas palustris obtain energy from light and carbon from organic compounds during anaerobic growth. Cells can naturally produce hydrogen gas biofuel as a way of disposing of excess electrons."

Feeding these bacteria more electron rich organic compounds though, does not always produce the logically expected result of increased hydrogen production. Harwood and McKinlay analyzed metabolic functions of R. palustris grown on four different compounds to better understand what other variables might be involved.

One factor involved appears to be the Calvin cycle, a series of biochemical reactions responsible for the process known as carbon dioxide fixation. The Calvin cycle converts carbon dioxide and electrons into organic compounds. Therefore carbon dioxide-fixation and hydrogen production naturally compete for electrons.

When they tested a strain of the bacterium, which had been genetically modified to block carbon dioxide-fixation they observed an increased output of hydrogen from all four substrates.

The Calvin cycle was not the only variable affecting hydrogen production that Harwood and McKinlay identified in the paper. They also determined that the metabolic route a growth substrate took on its way to becoming a building block for making new cells also played a role.

"Our work illustrates how an understanding of bacterial metabolism and physiology can be applied to engineer microbes for the production of sustainable biofuels," says Harwood.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by American Society for Microbiology, via EurekAlert!, a service of AAAS.

Journal Reference:

J. B. McKinlay, C. S. Harwood. Calvin Cycle Flux, Pathway Constraints, and Substrate Oxidation State Together Determine the H2 Biofuel Yield in Photoheterotrophic Bacteria. mBio, 2011; 2 (2): e00323-10 DOI: 10.1128/mBio.00323-10

Multiplexed capillary isoelectric focusing increases efficiency in protein measurements

The Springer journal Analytical and Bioanalytical Chemistry (ABC) has chosen Oluwatosin O. Dada (34) as the recipient of its Best Paper Award 2010. Dada is the lead author of a paper in ABC on capillary isoelectric focusing. The award, accompanied by 1,000 euros, was created by Springer to help exceptional young scientists establish their research careers. The ABC Best Paper Award has been given since 2005.

Capillary isoelectric focusing is an interesting technique for the characterization of proteins. However, multiplexing capillary isoelectric focusing is a daunting task. Dr. Dada's significant contribution to this technology is the development of a state-of-the-art tool for high-throughput capillary isoelectric focusing. The performance of this technology is stunning: It provides the highest throughput isoelectric focusing analysis ever reported, the highest sensitivity ever reported for a high-throughput instrument, and the highest resolution separation ever reported for capillary isoelectric focusing. The technology will find wide application, including characterization of recombinant and therapeutic proteins, the diagnosis of disease, and the study of systems biology.

Dr. Dada received his BSc in industrial chemistry in 2001 from Olabisi Onabanjo University in Nigeria. He moved to the United States in 2004, where he received his PhD in analytical chemistry from Utah State University in 2008. He then spent two years at the University of Washington in Seattle as a postdoctoral research associate. Currently, he holds a research assistant professor position at the University of Notre Dame, USA, where he continues his research on capillary electrophoresis with laser-induced fluorescence and photothermal instrumentation for bioanalysis.

Prof. Aldo Roda, Editor of Analytical and Bioanalytical Chemistry, said, "There is a highly competitive effort underway in the scientific community to improve the analytical performance of isoelectric focusing (IEF) as a tool for protein separation and concentration. Several groups have investigated the miniaturization of cIEF and the integration of cIEF to a microchip format. With this paper, Dada and co-workers offer us new analytical approaches to resolving the ongoing problem of time-consuming procedures."

More information: The article "Capillary array isoelectric focusing with laser-induced fluorescence detection" is freely available online on SpringerLink at http://www.springe … 71l58435h58/

Provided by Springer