Highly efficient oxygen catalyst found: Rechargeable batteries and hydrogen-fuel production could benefit

ScienceDaily (Oct. 28, 2011) — A team of researchers at MIT has found one of the most effective catalysts ever discovered for splitting oxygen atoms from water molecules -- a key reaction for advanced energy-storage systems, including electrolyzers, to produce hydrogen fuel and rechargeable batteries. This new catalyst liberates oxygen at more than 10 times the rate of the best previously known catalyst of its type.

The new compound, composed of cobalt, iron and oxygen with other metals, splits oxygen from water (called the Oxygen Evolution Reaction, or OER) at a rate at least an order of magnitude higher than the compound currently considered the gold standard for such reactions, the team says. The compound's high level of activity was predicted from a systematic experimental study that looked at the catalytic activity of 10 known compounds.

The team, which includes materials science and engineering graduate student Jin Suntivich, mechanical engineering graduate student Kevin J. May and professor Yang Shao-Horn, published their results in Science on Oct. 28.

The scientists found that reactivity depended on a specific characteristic: the configuration of the outermost electron of transition metal ions. They were able to use this information to predict the high reactivity of the new compound -- which they then confirmed in lab tests.

"We not only identified a fundamental principle" that governs the OER activity of different compounds, "but also we actually found this new compound" based on that principle, says Shao-Horn, the Gail E. Kendall (1978) Associate Professor of Mechanical Engineering and Materials Science and Engineering.

Many other groups have been searching for more efficient catalysts to speed the splitting of water into hydrogen and oxygen. This reaction is key to the production of hydrogen as a fuel to be used in cars; the operation of some rechargeable batteries, including zinc-air batteries; and to generate electricity in devices called fuel cells. Two catalysts are needed for such a reaction -- one that liberates the hydrogen atoms, and another for the oxygen atoms -- but the oxygen reaction has been the limiting factor in such systems.

Other groups, including one led by MIT's Daniel Nocera, have focused on similar catalysts that can operate -- in a so-called "artificial leaf" -- at low cost in ordinary water. But such reactions can occur with higher efficiency in alkaline solutions, which are required for the best previously known catalyst, iridium oxide, as well as for this new compound.

Shao-Horn and her collaborators are now working with Nocera, integrating their catalyst with his artificial leaf to produce a self-contained system to generate hydrogen and oxygen when placed in an alkaline solution. They will also be exploring different configurations of the catalyst material to better understand the mechanisms involved. Their initial tests used a powder form of the catalyst; now they plan to try thin films to better understand the reactions.

In addition, even though they have already found the highest rate of activity yet seen, they plan to continue searching for even more efficient catalyst materials. "It's our belief that there may be others with even higher activity," Shao-Horn says.

Jens Norskov, a professor of chemical engineering at Stanford University and director of the Suncat Center for Interface Science and Catalysis there, who was not involved in this work, says, "I find this an extremely interesting 'rational design' approach to finding new catalysts for a very important and demanding problem."

The research, which was done in collaboration with visiting professor Hubert A. Gasteiger (currently a professor at the Technische Universität München in Germany) and professor John B. Goodenough from the University of Texas at Austin, was supported by the U.S. Department of Energy's Hydrogen Initiative, the National Science Foundation, the Toyota Motor Corporation and the Chesonis Foundation.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by Massachusetts Institute of Technology. The original article was written by David L. Chandler, MIT News Office.

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

Journal Reference:

J. Suntivich, K. J. May, H. A. Gasteiger, J. B. Goodenough, Y. Shao-Horn. A Perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles. Science, 2011; DOI: 10.1126/science.1212858

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Redox flow batteries, a promising technology for renewable energies integration

ScienceDaily (Oct. 14, 2011) — Today there is a wide variety of energy storage technologies at very different stages of development. Among them, the Redox Flow Battery (RFB) is an innovative solution based on the use of liquid electrolytes stored in tanks and pumped through a reactor to produce energy. Tecnalia is currently working in the development of high performance RFBs.

RFB is, by its very nature, a modular and highly flexible technology with very rapid response, little environmental impact and considerable potential for cutting costs. This is the reason why Redox Flow Batteries are emerging as a very promising option for stationary storage in general and for renewable applications in particular.

Renewable energies

There is no doubt that the development of renewable energies will be a key milestone in the way towards a new environmentally-friendly energy model., However, their variability and limited predictability are posing a problem for the operation of the system and, as a result, a barrier to their massive penetration.

A clear example of these difficulties is the need to maintain backup systems that generate energy during low wind or low solar irradiance periods. On the other side, high renewable generation can lead to energy waste during low demand periods.

Redox Flow Batteries are considered as a highly adequate technology to mitigate the variability of renewable energies and to improve their dispatchability, that is, to provide the capability to regulate the output in a similar way to conventional power stations. The energy stored during periods of high renewable production can be used to compensate for the lack of generation when the weather conditions are less favourable.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Elhuyar Fundazioa.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Novel energy-storage membrane: Performance surpasses existing rechargeable batteries and supercapacitors

ScienceDaily (Sep. 29, 2011) — A team from the National University of Singapore's Nanoscience and Nanotechnology Initiative (NUSNNI), led by principle investigator Dr Xie Xian Ning, has developed a novel energy-storage membrane.

Electrical energy storage and its management are becoming urgent issues due to climate change and energy shortage. Existing technologies such as rechargeable batteries and supercapacitors are based on complicated configurations including liquid electrolytes, and suffer from difficulties in scaling-up and high fabrication costs. There is also growing public concern and awareness of the impact of traditional energy sources on the environment, spurring a continued search for alternative, green, sustainable energy sources.

Cost-effective and environmentally-friendly

Recognising the issue, Dr Xie and his team have developed a membrane that not only promises greater cost-effectiveness in delivering energy, but also an environmentally-friendly solution. The researchers used a polystyrene-based polymer to deposit the soft, foldable membrane that, when sandwiched between and charged by two metal plates, could store charge at 0.2 farads per square centimeter. This is well above the typical upper limit of 1 microfarad per square centimetre for a standard capacitor.

The cost involved in energy storage is also drastically reduced. With existing technologies based on liquid electrolytes, it costs about US$7 to store each farad. With the advanced energy storage membrane, the cost to store each farad falls to an impressive US$0.62. This translates to an energy cost of 10-20 watt-hour per US dollar for the membrane, as compared to just 2.5 watt-hour per US dollar for lithium ion batteries.

Dr Xie said: "Compared to rechargeable batteries and supercapacitors, the proprietary membrane allows for very simple device configuration and low fabrication cost. Moreover, the performance of the membrane surpasses those of rechargeable batteries, such as lithium ion and lead-acid batteries, and supercapacitors."

The research is supported by grants from the Singapore-MIT Alliance for Research & Technology (SMART), and National Research Foundation. Dr Xie and his team started work on the membrane early last year and took about 1.5 years to reach their current status, and have successfully filed a US patent for this novel invention.

The discovery was featured in Energy & Environmental Science and highlighted by the international journal Nature.

Potential applications: From hybrid vehicles to solar panels and wind turbines

The membrane could be used in hybrid vehicles for instant power storage and delivery, thus improving energy efficiency and reducing carbon emission. Potentially, hybrid cars with the membrane technology could be powered by the energy stored in the membranes in conjunction with the energy provided by fuel combustion, increasing the lifespan of car batteries and cutting down on waste.

The membrane could also be integrated into solar panels and wind turbines to store and manage the electricity generated. Energy provided through these sources is prone to instability due to their dependence on natural factors. By augmenting these energy sources with the membrane, the issue of instability could potentially be negated, as surplus energy generated can be instantly stored in the membranes, and delivered for use at a stable rate at times when natural factors are insufficient, such as a lack of solar power during night-time.

Next Step

The research team has demonstrated the membrane's superior performance in energy storage using prototype devices. The team is currently exploring opportunities to work with venture capitalists to commercialise the membrane. To date, several venture capitalists have expressed strong interest in the technology.

"With the advent of our novel membrane, energy storage technology will be more accessible, affordable, and producible on a large scale. It is also environmentally-friendly and could change the current status of energy technology," Dr Xie said.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National University of Singapore, via AlphaGalileo.

Journal References:

Xie Xian Ning. Energy technology: Supersizing a supercapacitor. Nature, 477, 9; 01 September 2011 DOI: 10.1038/477009cXian Ning Xie, Kian Keat Lee, Junzhong Wang, Kian Ping Loh. Polarizable energy-storage membrane based on ionic condensation and decondensation. Energy & Environmental Science, 2011; 4 (10): 3960 DOI: 10.1039/C1EE01841H

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Better lithium-ion batteries are on the way

ScienceDaily (Sep. 26, 2011) — Lithium-ion batteries are everywhere, in smart phones, laptops, an array of other consumer electronics, and the newest electric cars. Good as they are, they could be much better, especially when it comes to lowering the cost and extending the range of electric cars. To do that, batteries need to store a lot more energy.

The anode is a critical component for storing energy in lithium-ion batteries. A team of scientists at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has designed a new kind of anode that can absorb eight times the lithium of current designs, and has maintained its greatly increased energy capacity after over a year of testing and many hundreds of charge-discharge cycles.

The secret is a tailored polymer that conducts electricity and binds closely to lithium-storing silicon particles, even as they expand to more than three times their volume during charging and then shrink again during discharge. The new anodes are made from low-cost materials, compatible with standard lithium-battery manufacturing technologies. The research team reports its findings in Advanced Materials, now available online.

High-capacity expansion

"High-capacity lithium-ion anode materials have always confronted the challenge of volume change -- swelling -- when electrodes absorb lithium," says Gao Liu of Berkeley Lab's Environmental Energy Technologies Division (EETD), a member of the BATT program (Batteries for Advanced Transportation Technologies) managed by the Lab and supported by DOE's Office of Vehicle Technologies.

Says Liu, "Most of today's lithium-ion batteries have anodes made of graphite, which is electrically conducting and expands only modestly when housing the ions between its graphene layers. Silicon can store 10 times more -- it has by far the highest capacity among lithium-ion storage materials -- but it swells to more than three times its volume when fully charged."

This kind of swelling quickly breaks the electrical contacts in the anode, so researchers have concentrated on finding other ways to use silicon while maintaining anode conductivity. Many approaches have been proposed; some are prohibitively costly.

One less-expensive approach has been to mix silicon particles in a flexible polymer binder, with carbon black added to the mix to conduct electricity. Unfortunately, the repeated swelling and shrinking of the silicon particles as they acquire and release lithium ions eventually push away the added carbon particles. What's needed is a flexible binder that can conduct electricity by itself, without the added carbon.

"Conducting polymers aren't a new idea," says Liu, "but previous efforts haven't worked well, because they haven't taken into account the severe reducing environment on the anode side of a lithium-ion battery, which renders most conducting polymers insulators."

One such experimental polymer, called PAN (polyaniline), has positive charges; it starts out as a conductor but quickly loses conductivity. An ideal conducting polymer should readily acquire electrons, rendering it conducting in the anode's reducing environment.

The signature of a promising polymer would be one with a low value of the state called the "lowest unoccupied molecular orbital," where electrons can easily reside and move freely. Ideally, electrons would be acquired from the lithium atoms during the initial charging process. Liu and his postdoctoral fellow Shidi Xun in EETD designed a series of such polyfluorene-based conducting polymers -- PFs for short.

When Liu discussed the excellent performance of the PFs with Wanli Yang of Berkeley Lab's Advanced Light Source (ALS), a scientific collaboration emerged to understand the new materials. Yang suggested conducting soft x-ray absorption spectroscopy on Liu and Xun's candidate polymers using ALS beamline 8.0.1 to determine their key electronic properties.

Says Yang, "Gao wanted to know where the ions and electrons are and where they move. Soft x-ray spectroscopy has the power to deliver exactly this kind of crucial information."

Compared with the electronic structure of PAN, the absorption spectra Yang obtained for the PFs stood out immediately. The differences were greatest in PFs incorporating a carbon-oxygen functional group (carbonyl).

"We had the experimental evidence," says Yang, "but to understand what we were seeing, and its relevance to the conductivity of the polymer, we needed a theoretical explanation, starting from first principles." He asked Lin-Wang Wang of Berkeley Lab's Materials Sciences Division (MSD) to join the research collaboration.

Wang and his postdoctoral fellow, Nenad Vukmirovic, conducted ab initio calculations of the promising polymers at the Lab's National Energy Research Scientific Computing Center (NERSC). Wang says, "The calculation tells you what's really going on -- including precisely how the lithium ions attach to the polymer, and why the added carbonyl functional group improves the process. It was quite impressive that the calculations matched the experiments so beautifully."

The simulation did indeed reveal "what's really going on" with the type of PF that includes the carbonyl functional group, and showed why the system works so well. The lithium ions interact with the polymer first, and afterward bind to the silicon particles. When a lithium atom binds to the polymer through the carbonyl group, it gives its electron to the polymer -- a doping process that significantly improves the polymer's electrical conductivity, facilitating electron and ion transport to the silicon particles.

Cycling for success

Having gone through one cycle of material synthesis at EETD, experimental analysis at the ALS, and theoretical simulation at MSD, the positive results triggered a new cycle of improvements. Almost as important as its electrical properties are the polymer's physical properties, to which Liu now added another functional group, producing a polymer that can adhere tightly to the silicon particles as they acquire or lose lithium ions and undergo repeated changes in volume.

Scanning electron microscopy and transmission electron microscopy at the National Center for Electron Microscopy (NCEM), showing the anodes after 32 charge-discharge cycles, confirmed that the modified polymer adhered strongly throughout the battery operation even as the silicon particles repeatedly expanded and contracted. Tests at the ALS and simulations confirmed that the added mechanical properties did not affect the polymer's superior electrical properties.

"Without the input from our partners at the ALS and in MSD, what can be modified and what should not be modified in the next generation of polymers would not have been obvious," says Vince Battaglia, Program Manager of EETD's Advanced Energy Technologies Department.

"This achievement provides a rare scientific showcase, combining advanced tools of synthesis, characterization, and simulation in a novel approach to materials development," says Zahid Hussain, the ALS Division Deputy for Scientific Support and Scientific Support Group Leader. "The cyclic approach can lead to the discovery of new practical materials with a fundamental understanding of their properties."

The icing on the anode cake is that the new PF-based anode is not only superior but economical. "Using commercial silicon particles and without any conductive additive, our composite anode exhibits the best performance so far," says Gao Liu. "The whole manufacturing process is low cost and compatible with established manufacturing technologies. The commercial value of the polymer has already been recognized by major companies, and its possible applications extend beyond silicon anodes."

Anodes are a key component of lithium-ion battery technology, but far from the only challenge. Already the research collaboration is pushing to the next step, studying other battery components including cathodes.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

Gao Liu, Shidi Xun, Nenad Vukmirovic, Xiangyun Song, Paul Olalde-Velasco, Honghe Zheng, Vince S. Battaglia, Lin-Wang Wang, and Wanli Yang. Polymers with Tailored Electronic Structure for High Capacity Lithium Battery Electrodes. Advanced Materials, 2011 DOI: 10.1002/adma.201102421

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Better lithium-ion batteries are on the way

ScienceDaily (Sep. 26, 2011) — Lithium-ion batteries are everywhere, in smart phones, laptops, an array of other consumer electronics, and the newest electric cars. Good as they are, they could be much better, especially when it comes to lowering the cost and extending the range of electric cars. To do that, batteries need to store a lot more energy.

The anode is a critical component for storing energy in lithium-ion batteries. A team of scientists at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has designed a new kind of anode that can absorb eight times the lithium of current designs, and has maintained its greatly increased energy capacity after over a year of testing and many hundreds of charge-discharge cycles.

The secret is a tailored polymer that conducts electricity and binds closely to lithium-storing silicon particles, even as they expand to more than three times their volume during charging and then shrink again during discharge. The new anodes are made from low-cost materials, compatible with standard lithium-battery manufacturing technologies. The research team reports its findings in Advanced Materials, now available online.

High-capacity expansion

"High-capacity lithium-ion anode materials have always confronted the challenge of volume change -- swelling -- when electrodes absorb lithium," says Gao Liu of Berkeley Lab's Environmental Energy Technologies Division (EETD), a member of the BATT program (Batteries for Advanced Transportation Technologies) managed by the Lab and supported by DOE's Office of Vehicle Technologies.

Says Liu, "Most of today's lithium-ion batteries have anodes made of graphite, which is electrically conducting and expands only modestly when housing the ions between its graphene layers. Silicon can store 10 times more -- it has by far the highest capacity among lithium-ion storage materials -- but it swells to more than three times its volume when fully charged."

This kind of swelling quickly breaks the electrical contacts in the anode, so researchers have concentrated on finding other ways to use silicon while maintaining anode conductivity. Many approaches have been proposed; some are prohibitively costly.

One less-expensive approach has been to mix silicon particles in a flexible polymer binder, with carbon black added to the mix to conduct electricity. Unfortunately, the repeated swelling and shrinking of the silicon particles as they acquire and release lithium ions eventually push away the added carbon particles. What's needed is a flexible binder that can conduct electricity by itself, without the added carbon.

"Conducting polymers aren't a new idea," says Liu, "but previous efforts haven't worked well, because they haven't taken into account the severe reducing environment on the anode side of a lithium-ion battery, which renders most conducting polymers insulators."

One such experimental polymer, called PAN (polyaniline), has positive charges; it starts out as a conductor but quickly loses conductivity. An ideal conducting polymer should readily acquire electrons, rendering it conducting in the anode's reducing environment.

The signature of a promising polymer would be one with a low value of the state called the "lowest unoccupied molecular orbital," where electrons can easily reside and move freely. Ideally, electrons would be acquired from the lithium atoms during the initial charging process. Liu and his postdoctoral fellow Shidi Xun in EETD designed a series of such polyfluorene-based conducting polymers -- PFs for short.

When Liu discussed the excellent performance of the PFs with Wanli Yang of Berkeley Lab's Advanced Light Source (ALS), a scientific collaboration emerged to understand the new materials. Yang suggested conducting soft x-ray absorption spectroscopy on Liu and Xun's candidate polymers using ALS beamline 8.0.1 to determine their key electronic properties.

Says Yang, "Gao wanted to know where the ions and electrons are and where they move. Soft x-ray spectroscopy has the power to deliver exactly this kind of crucial information."

Compared with the electronic structure of PAN, the absorption spectra Yang obtained for the PFs stood out immediately. The differences were greatest in PFs incorporating a carbon-oxygen functional group (carbonyl).

"We had the experimental evidence," says Yang, "but to understand what we were seeing, and its relevance to the conductivity of the polymer, we needed a theoretical explanation, starting from first principles." He asked Lin-Wang Wang of Berkeley Lab's Materials Sciences Division (MSD) to join the research collaboration.

Wang and his postdoctoral fellow, Nenad Vukmirovic, conducted ab initio calculations of the promising polymers at the Lab's National Energy Research Scientific Computing Center (NERSC). Wang says, "The calculation tells you what's really going on -- including precisely how the lithium ions attach to the polymer, and why the added carbonyl functional group improves the process. It was quite impressive that the calculations matched the experiments so beautifully."

The simulation did indeed reveal "what's really going on" with the type of PF that includes the carbonyl functional group, and showed why the system works so well. The lithium ions interact with the polymer first, and afterward bind to the silicon particles. When a lithium atom binds to the polymer through the carbonyl group, it gives its electron to the polymer -- a doping process that significantly improves the polymer's electrical conductivity, facilitating electron and ion transport to the silicon particles.

Cycling for success

Having gone through one cycle of material synthesis at EETD, experimental analysis at the ALS, and theoretical simulation at MSD, the positive results triggered a new cycle of improvements. Almost as important as its electrical properties are the polymer's physical properties, to which Liu now added another functional group, producing a polymer that can adhere tightly to the silicon particles as they acquire or lose lithium ions and undergo repeated changes in volume.

Scanning electron microscopy and transmission electron microscopy at the National Center for Electron Microscopy (NCEM), showing the anodes after 32 charge-discharge cycles, confirmed that the modified polymer adhered strongly throughout the battery operation even as the silicon particles repeatedly expanded and contracted. Tests at the ALS and simulations confirmed that the added mechanical properties did not affect the polymer's superior electrical properties.

"Without the input from our partners at the ALS and in MSD, what can be modified and what should not be modified in the next generation of polymers would not have been obvious," says Vince Battaglia, Program Manager of EETD's Advanced Energy Technologies Department.

"This achievement provides a rare scientific showcase, combining advanced tools of synthesis, characterization, and simulation in a novel approach to materials development," says Zahid Hussain, the ALS Division Deputy for Scientific Support and Scientific Support Group Leader. "The cyclic approach can lead to the discovery of new practical materials with a fundamental understanding of their properties."

The icing on the anode cake is that the new PF-based anode is not only superior but economical. "Using commercial silicon particles and without any conductive additive, our composite anode exhibits the best performance so far," says Gao Liu. "The whole manufacturing process is low cost and compatible with established manufacturing technologies. The commercial value of the polymer has already been recognized by major companies, and its possible applications extend beyond silicon anodes."

Anodes are a key component of lithium-ion battery technology, but far from the only challenge. Already the research collaboration is pushing to the next step, studying other battery components including cathodes.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

Gao Liu, Shidi Xun, Nenad Vukmirovic, Xiangyun Song, Paul Olalde-Velasco, Honghe Zheng, Vince S. Battaglia, Lin-Wang Wang, and Wanli Yang. Polymers with Tailored Electronic Structure for High Capacity Lithium Battery Electrodes. Advanced Materials, 2011 DOI: 10.1002/adma.201102421

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Novel energy-storage membrane: Performance surpasses existing rechargeable batteries and supercapacitors

ScienceDaily (Sep. 29, 2011) — A team from the National University of Singapore's Nanoscience and Nanotechnology Initiative (NUSNNI), led by principle investigator Dr Xie Xian Ning, has developed a novel energy-storage membrane.

Electrical energy storage and its management are becoming urgent issues due to climate change and energy shortage. Existing technologies such as rechargeable batteries and supercapacitors are based on complicated configurations including liquid electrolytes, and suffer from difficulties in scaling-up and high fabrication costs. There is also growing public concern and awareness of the impact of traditional energy sources on the environment, spurring a continued search for alternative, green, sustainable energy sources.

Cost-effective and environmentally-friendly

Recognising the issue, Dr Xie and his team have developed a membrane that not only promises greater cost-effectiveness in delivering energy, but also an environmentally-friendly solution. The researchers used a polystyrene-based polymer to deposit the soft, foldable membrane that, when sandwiched between and charged by two metal plates, could store charge at 0.2 farads per square centimeter. This is well above the typical upper limit of 1 microfarad per square centimetre for a standard capacitor.

The cost involved in energy storage is also drastically reduced. With existing technologies based on liquid electrolytes, it costs about US$7 to store each farad. With the advanced energy storage membrane, the cost to store each farad falls to an impressive US$0.62. This translates to an energy cost of 10-20 watt-hour per US dollar for the membrane, as compared to just 2.5 watt-hour per US dollar for lithium ion batteries.

Dr Xie said: "Compared to rechargeable batteries and supercapacitors, the proprietary membrane allows for very simple device configuration and low fabrication cost. Moreover, the performance of the membrane surpasses those of rechargeable batteries, such as lithium ion and lead-acid batteries, and supercapacitors."

The research is supported by grants from the Singapore-MIT Alliance for Research & Technology (SMART), and National Research Foundation. Dr Xie and his team started work on the membrane early last year and took about 1.5 years to reach their current status, and have successfully filed a US patent for this novel invention.

The discovery was featured in Energy & Environmental Science and highlighted by the international journal Nature.

Potential applications: From hybrid vehicles to solar panels and wind turbines

The membrane could be used in hybrid vehicles for instant power storage and delivery, thus improving energy efficiency and reducing carbon emission. Potentially, hybrid cars with the membrane technology could be powered by the energy stored in the membranes in conjunction with the energy provided by fuel combustion, increasing the lifespan of car batteries and cutting down on waste.

The membrane could also be integrated into solar panels and wind turbines to store and manage the electricity generated. Energy provided through these sources is prone to instability due to their dependence on natural factors. By augmenting these energy sources with the membrane, the issue of instability could potentially be negated, as surplus energy generated can be instantly stored in the membranes, and delivered for use at a stable rate at times when natural factors are insufficient, such as a lack of solar power during night-time.

Next Step

The research team has demonstrated the membrane's superior performance in energy storage using prototype devices. The team is currently exploring opportunities to work with venture capitalists to commercialise the membrane. To date, several venture capitalists have expressed strong interest in the technology.

"With the advent of our novel membrane, energy storage technology will be more accessible, affordable, and producible on a large scale. It is also environmentally-friendly and could change the current status of energy technology," Dr Xie said.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National University of Singapore, via AlphaGalileo.

Journal References:

Xie Xian Ning. Energy technology: Supersizing a supercapacitor. Nature, 477, 9; 01 September 2011 DOI: 10.1038/477009cXian Ning Xie, Kian Keat Lee, Junzhong Wang, Kian Ping Loh. Polarizable energy-storage membrane based on ionic condensation and decondensation. Energy & Environmental Science, 2011; 4 (10): 3960 DOI: 10.1039/C1EE01841H

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New insights on an old material will enable design of better polymer batteries, water purification

ScienceDaily (June 19, 2011) — Designing new materials depends upon understanding the properties of today's materials. One such material, Nafion ©, is a polymer that efficiently conducts ions (a polymer electrolyte) and water through its nanostructure, making it important for many energy-related industrial applications, including in fuel cells, organic batteries, and reverse-osmosis water purification. But since Nafion was invented 50 years ago, scientists have only been able to speculate about how to build new materials because they have not been able to see details on how the molecules come together and work within Nafion.

Now, two Virginia Tech research groups have combined forces to devise a way to measure Nafion's internal structure and, in the process, have discovered how to manipulate this structure to enhance the material's applications.

The research is published in the June 19 issue of Nature Materials in the Letters article, "Linear coupling of alignment with transport in a polymer electrolyte membrane," by Jing Li, Jong Keun Park, Robert B. Moore, and Louis A. Madsen, all with the chemistry department in the College of Science and the Macromolecules and Interfaces Institute at Virginia Tech.

Nafion is made up of molecules that combine the non-stick and tough nature of Teflon with the conductive properties of an acid, such as battery acid. A network of tiny channels, nanometers in size, carries water or ions quickly through the polymer. "But, due to the irregular structure of Nafion, scientists have not been able to get reliable information about its properties using most standard analysis tools, such as transmission electron microscopy," said Madsen, assistant professor of physical, polymer, and materials chemistry.

Madsen and Moore, professor of physical and polymer chemistry; Madsen's post-doctoral associate Jing Li; and Moore's Ph.D. student Jong Keun Park, of Korea, were able to use nuclear magnetic resonance (NMR)to measure molecular motion, and a combination of NMR and X-ray scattering to measure molecular alignment within Nafion. "We were looking at water molecules inside Nafion as internal reporters of structure and efficiency of conduction," said Madsen. "The new feature we discovered is the locally aligned aggregates of polymer molecules in the material. The molecules align like strands of dry spaghetti lined up in a box. We can measure the speed (diffusion) of the water molecules and the direction they travel within those structures, which relates strongly to the alignment of the polymer molecule strands."

The researchers observed that the alignment of the channels influenced the speed and preferential direction of water motion. And a startlingly clear picture presented itself when the scientists stretched the Nafion and measured its structure and water motion.

"Stretching drastically influences the degree of alignment," said Madsen. "So the molecules move faster along the direction of the stretch, and in a very predictable way. These materials actually share some properties with liquid crystals -- molecules that line up with each other and are used in every LCD television, projector, and screen."

These relationships have not been previously recognized in a polymer electrolyte, Madsen said.

The ability to observe motion and direction, and understand what is happening within Nafion, has implications for using the material in new ways, and for designing new materials, the researchers write in the Nature Materials article. Ion-based applications could include actuator devices such as artificial muscles, organic batteries, and more energy efficient fuel cells. A water-based application would be improved reverse osmosis membranes for water purification.

Madsen and Moore started this collaborative project shortly after they arrived at Virginia Tech (Madsen in 2006, Moore in 2007), and they are furthering their work together by investigating new polymeric materials using their unique combination of analysis techniques.

"Alignment provides for a better flow of the molecules through the polymer," Madsen said.

The research is supported by Madsen's National Science Foundation Faculty Early Career Development (CAREER) Award. His research focuses on improving advanced polymers for fuel cells and reverse-osmosis water purification by combining detailed analysis of these materials with theoretical understanding. The research is also supported by the US Army Research Office under Ionic Liquids in Electro-Active Devices (ILEAD) Multidisciplinary University Research Initiative (MURI) grant.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Virginia Tech, via EurekAlert!, a service of AAAS.

Journal Reference:

Jing Li, Jong Keun Park, Robert B. Moore and Louis A. Madsen. Linear coupling of alignment with transport in a polymer electrolyte membrane. Nature Materials, June 19 2011 DOI: 10.1038/NMAT3048

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New method to make sodium ion-based battery cells could lead to better, cheaper batteries for the electrical grid

ScienceDaily (June 8, 2011) — By adding the right amount of heat, researchers have developed a method that improves the electrical capacity and recharging lifetime of sodium ion rechargeable batteries, which could be a cheaper alternative for large-scale uses such as storing energy on the electrical grid.

To connect solar and wind energy sources to the electrical grid, grid managers require batteries that can store large amounts of energy created at the source. Lithium ion rechargeable batteries -- common in consumer electronics and electric vehicles -- perform well, but are too expensive for widespread use on the grid because many batteries will be needed, and they will likely need to be large. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300 degrees Celsius, or three times the temperature of boiling water, making them less energy efficient and safe than batteries that run at ambient temperatures.

Battery developers want the best of both worlds -- to use both inexpensive sodium and use the type of electrodes found in lithium rechargeables. A team of scientists at the Department of Energy's Pacific Northwest National Laboratory and visiting researchers from Wuhan University in Wuhan, China used nanomaterials to make electrodes that can work with sodium, they reported June 3 online in the journal Advanced Materials.

"The sodium-ion battery works at room temperature and uses sodium ions, an ingredient in cooking salt. So it will be much cheaper and safer," said PNNL chemist Jun Liu, who co-led the study with Wuhan University chemist Yuliang Cao.

The electrodes in lithium rechargeables that interest researchers are made of manganese oxide. The atoms in this metal oxide form many holes and tunnels that lithium ions travel through when batteries are being charged or are in use. The free movement of lithium ions allows the battery to hold electricity or release it in a current. But simply replacing the lithium ions with sodium ions is problematic -- sodium ions are 70 percent bigger than lithium ions and don't fit in the crevices as well.

To find a way to make bigger holes in the manganese oxide, PNNL researchers went much much smaller. They turned to nanomaterials -- materials made on the nanometer-sized scale, or about a million times thinner than a dime -- that have surprising properties due to their smallness. For example, the short distances that sodium ions have to travel in nanowires might make the manganese oxide a better electrode in ways unrelated to the size of the tunnels.

To explore, the team mixed two different kinds of manganese oxide atomic building blocks -- one whose atoms arrange themselves in pyramids, and another one whose atoms form an octahedron, a diamond-like structure from two pyramids stuck together at their bases. They expected the final material to have large S-shaped tunnels and smaller five-sided tunnels through which the ions could flow.

After mixing, the team treated the materials with temperatures ranging from 450 to 900 degrees Celsius, then examined the materials and tested which treatment worked best. Using a scanning electron microscope, the team found that different temperatures created material of different quality. Treating the manganese oxide at 750 degrees Celsius created the best crystals: too low and the crystals appeared flakey, too high and the crystals turned into larger flat plates.

Zooming in even more using a transmission electron microscope at EMSL, DOE's Environmental Molecular Sciences Laboratory on PNNL's campus, the team saw that manganese oxide heated to 600 degrees had pockmarks in the nanowires that could impede the sodium ions, but the 750 degree-treated wires looked uniform and very crystalline.

But even the best-looking material is just window-dressing if it doesn't perform well. To find out if it lived up to its good looks, the PNNL-Wuhan team dipped the electrode material in electrolyte, the liquid containing sodium ions that will help the manganese oxide electrodes form a current. Then they charged and discharged the experimental battery cells repeatedly.

The team measured peak capacity at 128 milliAmp hours per gram of electrode material as the experimental battery cell discharged. This result surpassed earlier ones taken by other researchers, one of which achieved peak capacity of 80 milliAmp hours per gram for electrodes made from manganese oxide but with a different production method. The researchers think the lower capacity is due to sodium ions causing structural changes in that manganese oxide that do not occur or occur less frequently in the heat-treated nano-sized material.

In addition to high capacity, the material held up well to cycles of charging and discharging, as would occur in consumer use. Again, the material treated at 750 Celsius performed the best: after 100 cycles of charging-discharging, it lost only 7 percent of its capacity. Material treated at 600 Celsius or 900 Celsius lost about 37 percent and 25 percent, respectively.

Even after 1,000 cycles, the capacity of the 750 Celsius-treated electrodes only dropped about 23 percent. The researchers thought the material performed very well, retaining 77 percent of its initial capacity.

Last, the team charged the experimental cell at different speeds to determine how quickly it could take up electricity. The team found that the faster they charged it, the less electricity it could hold. This suggested to the team that the speed with which sodium ions could diffuse into the manganese oxide limited the battery cell's capacity -- when charged fast, the sodium ions couldn't enter the tunnels fast enough to fill them up.

To compensate for the slow sodium ions, the researchers suggest in the future they make even smaller nanowires to speed up charging and discharging. Grid batteries need fast charging so they can collect as much newly made energy coming from renewable sources as possible. And they need to discharge fast when demands shoots up as consumers turn on their air conditioners and television sets, and plug in their electric vehicles at home.

Such high performing batteries could take the heat off an already taxed electrical power grid.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Pacific Northwest National Laboratory.

Journal Reference:

Yuliang Cao, Lifen Xiao, Wei Wang, Daiwon Choi, Zimin Nie, Jianguo Yu, Laxmikant V. Saraf, Zhenguo Yang, Jun Liu. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Advanced Materials, 2011; DOI: 10.1002/adma.201100904

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New method to make sodium ion-based battery cells could lead to better, cheaper batteries for the electrical grid

ScienceDaily (June 8, 2011) — By adding the right amount of heat, researchers have developed a method that improves the electrical capacity and recharging lifetime of sodium ion rechargeable batteries, which could be a cheaper alternative for large-scale uses such as storing energy on the electrical grid.

To connect solar and wind energy sources to the electrical grid, grid managers require batteries that can store large amounts of energy created at the source. Lithium ion rechargeable batteries -- common in consumer electronics and electric vehicles -- perform well, but are too expensive for widespread use on the grid because many batteries will be needed, and they will likely need to be large. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300 degrees Celsius, or three times the temperature of boiling water, making them less energy efficient and safe than batteries that run at ambient temperatures.

Battery developers want the best of both worlds -- to use both inexpensive sodium and use the type of electrodes found in lithium rechargeables. A team of scientists at the Department of Energy's Pacific Northwest National Laboratory and visiting researchers from Wuhan University in Wuhan, China used nanomaterials to make electrodes that can work with sodium, they reported June 3 online in the journal Advanced Materials.

"The sodium-ion battery works at room temperature and uses sodium ions, an ingredient in cooking salt. So it will be much cheaper and safer," said PNNL chemist Jun Liu, who co-led the study with Wuhan University chemist Yuliang Cao.

The electrodes in lithium rechargeables that interest researchers are made of manganese oxide. The atoms in this metal oxide form many holes and tunnels that lithium ions travel through when batteries are being charged or are in use. The free movement of lithium ions allows the battery to hold electricity or release it in a current. But simply replacing the lithium ions with sodium ions is problematic -- sodium ions are 70 percent bigger than lithium ions and don't fit in the crevices as well.

To find a way to make bigger holes in the manganese oxide, PNNL researchers went much much smaller. They turned to nanomaterials -- materials made on the nanometer-sized scale, or about a million times thinner than a dime -- that have surprising properties due to their smallness. For example, the short distances that sodium ions have to travel in nanowires might make the manganese oxide a better electrode in ways unrelated to the size of the tunnels.

To explore, the team mixed two different kinds of manganese oxide atomic building blocks -- one whose atoms arrange themselves in pyramids, and another one whose atoms form an octahedron, a diamond-like structure from two pyramids stuck together at their bases. They expected the final material to have large S-shaped tunnels and smaller five-sided tunnels through which the ions could flow.

After mixing, the team treated the materials with temperatures ranging from 450 to 900 degrees Celsius, then examined the materials and tested which treatment worked best. Using a scanning electron microscope, the team found that different temperatures created material of different quality. Treating the manganese oxide at 750 degrees Celsius created the best crystals: too low and the crystals appeared flakey, too high and the crystals turned into larger flat plates.

Zooming in even more using a transmission electron microscope at EMSL, DOE's Environmental Molecular Sciences Laboratory on PNNL's campus, the team saw that manganese oxide heated to 600 degrees had pockmarks in the nanowires that could impede the sodium ions, but the 750 degree-treated wires looked uniform and very crystalline.

But even the best-looking material is just window-dressing if it doesn't perform well. To find out if it lived up to its good looks, the PNNL-Wuhan team dipped the electrode material in electrolyte, the liquid containing sodium ions that will help the manganese oxide electrodes form a current. Then they charged and discharged the experimental battery cells repeatedly.

The team measured peak capacity at 128 milliAmp hours per gram of electrode material as the experimental battery cell discharged. This result surpassed earlier ones taken by other researchers, one of which achieved peak capacity of 80 milliAmp hours per gram for electrodes made from manganese oxide but with a different production method. The researchers think the lower capacity is due to sodium ions causing structural changes in that manganese oxide that do not occur or occur less frequently in the heat-treated nano-sized material.

In addition to high capacity, the material held up well to cycles of charging and discharging, as would occur in consumer use. Again, the material treated at 750 Celsius performed the best: after 100 cycles of charging-discharging, it lost only 7 percent of its capacity. Material treated at 600 Celsius or 900 Celsius lost about 37 percent and 25 percent, respectively.

Even after 1,000 cycles, the capacity of the 750 Celsius-treated electrodes only dropped about 23 percent. The researchers thought the material performed very well, retaining 77 percent of its initial capacity.

Last, the team charged the experimental cell at different speeds to determine how quickly it could take up electricity. The team found that the faster they charged it, the less electricity it could hold. This suggested to the team that the speed with which sodium ions could diffuse into the manganese oxide limited the battery cell's capacity -- when charged fast, the sodium ions couldn't enter the tunnels fast enough to fill them up.

To compensate for the slow sodium ions, the researchers suggest in the future they make even smaller nanowires to speed up charging and discharging. Grid batteries need fast charging so they can collect as much newly made energy coming from renewable sources as possible. And they need to discharge fast when demands shoots up as consumers turn on their air conditioners and television sets, and plug in their electric vehicles at home.

Such high performing batteries could take the heat off an already taxed electrical power grid.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Pacific Northwest National Laboratory.

Journal Reference:

Yuliang Cao, Lifen Xiao, Wei Wang, Daiwon Choi, Zimin Nie, Jianguo Yu, Laxmikant V. Saraf, Zhenguo Yang, Jun Liu. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Advanced Materials, 2011; DOI: 10.1002/adma.201100904

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here