Significant Step Toward Lightweight Batteries

Significant Step Toward Lightweight Batteries

  1:00:00 AM    Science Lover

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A team of researchers at MIT has made significant progress on a technology that could lead to batteries with up to three times the energy density of any battery that currently exists.

Yang Shao-Horn, an MIT associate professor of mechanical engineering and materials science and engineering, says that many groups have been pursuing work on lithium-air batteries, a technology that has great potential for achieving great gains in energy density. But there has been a lack of understanding of what kinds of electrode materials could promote the electrochemical reactions that take place in these batteries.

Test battery has inlet and outlet on the sides to provide 
a flow of air,providing oxygen for the battery's operation.
Photo: (Credit: Patrick Gillooly/MIT)

Lithium-oxygen (also known as lithium-air) batteries are similar in principle to the lithium-ion batteries that now dominate the field of portable electronics and are a leading contender for electric vehicles. But because lithium-air batteries replace the heavy conventional compounds in such batteries with a carbon-based air electrode and flow of air, the batteries themselves can be much lighter. That's why leading companies, including IBM and General Motors, have committed to major research initiatives on lithium-air technology.

In a paper published this week in the journal Electrochemical and Solid-State Letters, Shao-Horn, along with some of her students and visiting professor Hubert Gasteiger, reported on a study showing that electrodes with gold or platinum as a catalyst show a much higher level of activity and thus a higher efficiency than simple carbon electrodes in these batteries. In addition, this new work sets the stage for further research that could lead to even better electrode materials, perhaps alloys of gold and platinum or other metals, or metallic oxides, and to less expensive alternatives.

Doctoral student Yi-Chun Lu, lead author of the paper, explains that this team has developed a method for analyzing the activity of different catalysts in the batteries, and now they can build on this research to study a variety of possible materials. "We'll look at different materials, and look at the trends," she says. "Such research could allow us to identify the physical parameters that govern the catalyst activity. Ultimately, we will be able to predict the catalyst behaviors. "

Lightweight batteries that can deliver lots of energy are crucial for a variety of applications -- for example, improving the range of electric cars. For that reason, even modest increases in a battery's energy-density rating -- a measure of the amount of energy that can be delivered for a given weight -- are important advances.

One issue to be dealt with in developing a battery system that could be widely commercialized is safety. Lithium in metallic form, which is used in lithium-air batteries, is highly reactive in the presence of even minuscule amounts of water. This is not an issue in current lithium-ion batteries because carbon-based materials are used for the negative electrode. Shao-Horn says the same battery principle can be applied without the need to use metallic lithium; graphite or some other more stable negative electrode materials could be used instead, she says, leading to a safer system.

A number of issues must be addressed before lithium-air batteries can become a practical commercial product, she says. The biggest issue is developing a system that keeps its power through a sufficient number of charging and discharging cycles for it to be useful in vehicles or electronic devices.

Researchers also need to look into details of the chemistry of the charging and discharging processes, to see what compounds are produced and where, and how they react with other compounds in the system. "We're at the very beginning" of understanding exactly how these reactions occur, Shao-Horn says.

Gholam-Abbas Nazri, a researcher at the GM Research & Development Center in Michigan, calls this research "interesting and important," and says this addresses a significant bottleneck in the development of this technology: the need find an efficient catalyst. This work is "in the right direction for further understanding of the role of catalysts," and it "may significantly contribute to the further understanding and future development of lithium-air systems," he says.

While some companies working on lithium-air batteries have said they see it as a 10-year development program, Shao-Horn says it is too early to predict how long it may take to reach commercialization. "It's a very promising area, but there are many science and engineering challenges to be overcome," she says. "If it truly demonstrates two to three times the energy density" of today's lithium-ion batteries, she says, the likely first applications will be in portable electronics such as computers and cell phones, which are high-value items, and only later would be applied to vehicles once the costs are reduced.

Funding was provided by the Department of Energy, with additional support from the Martin Family Society of Fellows for Sustainability and the National Science Foundation.

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Nanotechnology Sparks Energy Storage on Paper and Cloth

Nanotechnology Sparks Energy Storage on Paper and Cloth

  10:08:00 PM    Science Lover

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By dipping ordinary paper or fabric in a special ink infused with nanoparticles, Stanford engineer Yi Cui has found a way to cheaply and efficiently manufacture lightweight paper batteries and supercapacitors (which, like batteries, store energy, but by electrostatic rather than chemical means), as well as stretchable, conductive textiles known as "eTextiles" -- capable of storing energy while retaining the mechanical properties of ordinary paper or fabric.

While the technology is still new, Cui's team has envisioned numerous functional uses for their inventions. Homes of the future could one day be lined with energy-storing wallpaper. Gadget lovers would be able to charge their portable appliances on the go, simply plugging them into an outlet woven into their T-shirts. Energy textiles might also be used to create moving-display apparel, reactive high-performance sportswear and wearable power for a soldier's battle gear.

The key ingredients in developing these high-tech products are not visible to the human eye. Nanostructures, which can be assembled in patterns that allow them to transport electricity, may provide the solutions to a number of problems encountered with electrical storage devices currently available on the market.

The type of nanoparticle used in the Cui group's experimental devices varies according to the intended function of the product -- lithium cobalt oxide is a common compound used for batteries, while single-walled carbon nanotubes, or SWNTs, are used for supercapacitors.

Cui, an assistant professor of materials science and engineering at Stanford, leads a research group that investigates new applications of nanoscale materials. The objective, said Cui, is not only to supply answers to theoretical inquiries but also to pursue projects with practical value. Recently, his team has focused on ways to integrate nanotechnology into the realm of energy development.

"Energy storage is a pretty old research field," said Cui. "Supercapacitors, batteries -- those things are old. How do you really make a revolutionary impact in this field? It requires quite a dramatic difference of thinking."

While electrical energy storage devices have come a long way since Alessandro Volta debuted the world's first electrical cell in 1800, the technology is facing yet another revolution. Current methods of manufacturing energy storage devices can be capital intensive and environmentally hazardous, and the end products have noticeable performance constraints -- conventional lithium ion batteries have a limited storage capacity and are costly to manufacture, while traditional capacitors provide high power but at the expense of energy storage capacity.

With a little help from new science, the batteries of the future may not look anything like the bulky metal units we've grown accustomed to. Nanotechnology is favored as a remedy both for its economic appeal and its capability to improve energy performance in devices that integrate it. Replacing the carbon (graphite) anodes found in lithium ion batteries with anodes of silicon nanowires, for example, has the potential to increase their storage capacity by 10 times, according to experiments conducted by Cui's team.

Silicon had previously been recognized as a favorable anode material because it can hold a larger amount of lithium than carbon. But applications of silicon were limited by its inability to sustain physical stress -- namely, the fourfold volume increase that silicon undergoes when lithium ions attach themselves to a silicon anode in the process of charging a battery, as well as the shrinkage that occurs when lithium ions are drawn out as it discharges. The result was that silicon structures would disintegrate, causing anodes of this material to lose much if not all of their storage capacity.

Cui and collaborators demonstrated in previous publications in Nature, Nanotechnology and Nano Letters that the use of silicon nanowire battery electrodes, mechanically capable of withstanding the absorption and discharge of lithium ions, was one way to sidestep the problem.

The findings hold promise for the development of rechargeable lithium batteries offering a longer life cycle and higher energy capacity than their contemporaries. Silicon nanowire technology may one day find a home in electric cars, portable electronic devices and implantable medical appliances.

Cui now hopes to direct his research toward studying both the "hard science" behind the electrical properties of nanomaterials and designing real-world applications.

"This is the right time to really see what we learn from nanoscience and do practical applications that are extremely promising," said Cui. "The beauty of this is, it combines the lowest cost technology that you can find to the highest tech nanotechnology to produce something great. I think this is a very exciting idea … a huge impact for society."

The Cui group's latest research on energy storage devices was detailed in papers published in the online editions of the Proceedings of the National Academy of Sciences in December 2009 ("Highly Conductive Paper for Energy-Storage Devices") and Nano Letters in January 2010 ("Stretchable, Porous and Conductive Energy Textiles").

Cui's presented his talk at the symposium "Nanotechnology: Will Nanomaterials Revolutionize Energy Applications?" at the San Diego Convention Center.

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Lithium-Air Batteries might Displace Gasoline in Future Cars

Lithium-Air Batteries might Displace Gasoline in Future Cars

  8:03:00 PM    Science Lover

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Inside surplus of seven million barrels of gasoline are consumed by vehicles in the United States each time. Equally scientists rush to discover environmentally sound solutions to fuel the world's ever-growing moving needs, battery researchers are exploring the look good of lithium-air battery equipment.

Argonne researcher Lynn Trahey tons a coin-sized cell on a trying thing used to evaluate electrochemical cycling performance in batteries. (Credit: Photo by Wes Agresta / Courtesy of Argonne National Laboratory)

Li-air batteries aid a catalytic air cathode with the intention of equipment oxygen, an electrolyte and a lithium anode. The equipment has the the makings to pile almost as much energy as a tank of gasoline, and will be inflicted with a room pro energy storage space with the intention of is five to 10 era greater than with the intention of of Li-ion batteries, a join equipment. That the makings, however, will not be realized until vital methodical challenges be inflicted with been solved.

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Paper, Nanotube Ink, Wires: Instant Battery

Paper, Nanotube Ink, Wires: Instant Battery

  10:15:00 AM    Science Lover

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Stanford scientists are harnessing nanotechnology to quickly produce ultra-lightweight, bendable batteries and supercapacitors in the form of everyday paper.

Bing Hu, a post-doctoral fellow, prepares a small square of ordinary paper to with an ink that will deposit nanotubes on the surface that can then be charged with energy to create a battery. (Credit: L.A. Cicero)

Simply coating a sheet of paper with ink made of carbon nanotubes and silver nanowires makes a highly conductive storage device, said Yi Cui, assistant professor of materials science and engineering.

"Society really needs a low-cost, high-performance energy storage device, such as batteries and simple supercapacitors," he said.

Like batteries, capacitors hold an electric charge, but for a shorter period of time. However, capacitors can store and discharge electricity much more rapidly than a battery.

Cui's work is reported in the paper "Highly Conductive Paper for Energy Storage Devices," published online in the Proceedings of the National Academy of Sciences.

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A cheaper, lighter and longer-lasting alternative to modern batteries

A cheaper, lighter and longer-lasting alternative to modern batteries

  9:56:00 PM    Science Lover

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MOBILE phones looked like bricks in the 1980s. Indeed, they were so cumbersome that most were installed in cars. That was because the batteries required to power them were so hefty. When lithium-ion batteries were invented, mobile phones became small enough to be carried in a pocket or slipped into a handbag. Now a new design of battery that uses oxygen from ambient air to power devices could provide even smaller and lighter sources of power. Not only that, such batteries would be cheaper and last for longer between charges.

Lithium-ion batteries have two electrodes immersed in an electrically conductive solution, called an electrolyte. One of the electrodes, the cathode, is made of lithium cobalt oxide; the other, the anode, is composed of carbon. When the battery is being charged, positively charged lithium ions break away from the cathode and travel in the electrolyte to the anode, where they meet electrons brought there by a charging device. When electricity is needed, the anode releases the lithium ions, which rapidly move back to the cathode. As they do so, the electrons that were paired with them in the anode during the charging process are released. These electrons travel around an external circuit to which the battery is attached and power it.

Peter Bruce and his colleagues at the University of St Andrews in Scotland came up with the idea of replacing the lithium cobalt oxide electrode with a cheaper and lighter alternative. They designed an electrode made from porous carbon and lithium oxide. They knew that lithium oxide forms naturally from lithium ions, electrons and oxygen, but, to their surprise, they found that it could also be made to separate easily when an electric current passed through it. They exposed one side of their porous carbon electrode to an electrolyte rich in lithium ions and put a mesh window on the other side of the electrode through which air could be drawn. Oxygen from the air took the place of the cobalt oxide.

When they charged their battery, the lithium ions migrated to the anode where they combined with electrons from the charging device. When they discharged it, lithium ions and electrons were released from the anode. The ions crossed the electrolyte and the electrons travelled round the external circuit. The ions and electrons then met at the cathode, where they combined with the oxygen to form lithium oxide that filled the pores in the carbon.

Because the oxygen being used by the battery comes from the surrounding air rather than having to be carried around inside the battery, the device that Dr Bruce’s team has designed can be a mere one-eighth to one-tenth the size and weight of modern batteries, while still carrying the same charge. Alternatively, batteries using the new technology would last eight to ten times longer than modern batteries of the same size.

Performance and size are not the only expected improvements. Although they are not yet commercially available, making such a battery is expected to be cheaper. Lithium cobalt oxide accounts for 30% of the cost of a lithium-ion battery. Air, however, is free.

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Air-fueled Battery Could Last Up To 10 Times Longer: Ground-breaking Technology For Electric Cars

Air-fueled Battery Could Last Up To 10 Times Longer: Ground-breaking Technology For Electric Cars

  9:55:00 AM    Science Lover

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A new type of air-fuelled battery could give up to ten times the energy storage of designs currently available.

Diagram of the STAIR (St Andrews Air) cell. Oxygen drawn from the air reacts within the porous carbon to release the electrical charge in this lithium-air battery. (Credit: Image courtesy of Engineering and Physical Sciences Research Council (EPSRC))

This step-change in capacity could pave the way for a new generation of electric cars, mobile phones and laptops.

The research work, funded by the Engineering and Physical Sciences Research Council (EPSRC), is being led by researchers at the University of St Andrews with partners at Strathclyde and Newcastle.

The new design has the potential to improve the performance of portable electronic products and give a major boost to the renewable energy industry. The batteries will enable a constant electrical output from sources such as wind or solar, which stop generating when the weather changes or night falls.

Improved capacity is thanks to the addition of a component that uses oxygen drawn from the air during discharge, replacing one chemical constituent used in rechargeable batteries today. Not having to carry the chemicals around in the battery offers more energy for the same size battery. Reducing the size and weight of batteries with the necessary charge capacity has been a long-running battle for developers of electric cars.

The STAIR (St Andrews Air) cell should be cheaper than today’s rechargeables, too. The new component is made of porous carbon, which is far less expensive than the lithium cobalt oxide it replaces.

This four-year research project, which reaches its halfway mark in July, builds on the discovery at the university that the carbon component’s interaction with air can be repeated, creating a cycle of charge and discharge. Subsequent work has more than tripled the capacity to store charge in the STAIR cell.

Principal investigator on the project, Professor Peter Bruce of the Chemistry Department at the University of St Andrews, says: “Our target is to get a five to ten fold increase in storage capacity, which is beyond the horizon of current lithium batteries. Our results so far are very encouraging and have far exceeded our expectations.”

“The key is to use oxygen in the air as a re-agent, rather than carry the necessary chemicals around inside the battery,” says Bruce.

The oxygen, which will be drawn in through a surface of the battery exposed to air, reacts within the pores of the carbon to discharge the battery. “Not only is this part of the process free, the carbon component is much cheaper than current technology,” says Bruce. He estimates that it will be at least five years before the STAIR cell is commercially available.

The project is focused on understanding more about how the chemical reaction of the battery works and investigating how to improve it. The research team is also working towards making a STAIR cell prototype suited, in the first instance, for small applications, such as mobile phones or MP3 players.

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Virus-built Battery Could Power Cars, Electronic Devices

Virus-built Battery Could Power Cars, Electronic Devices

  9:11:00 PM    Science Lover

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Angela Belcher holds a display of the virus-built battery she helped engineer. The battery -- the silver-colored disc -- is being used to power an LED. (Credit: Photo by Donna Coveney)

For the first time, MIT researchers have shown they can genetically engineer viruses to build both the positively and negatively charged ends of a lithium-ion battery.

The new virus-produced batteries have the same energy capacity and power performance as state-of-the-art rechargeable batteries being considered to power plug-in hybrid cars, and they could also be used to power a range of personal electronic devices, said Angela Belcher, the MIT materials scientist who led the research team.

The new batteries, described in the April 2 online edition of Science, could be manufactured with a cheap and environmentally benign process: The synthesis takes place at and below room temperature and requires no harmful organic solvents, and the materials that go into the battery are non-toxic.

In a traditional lithium-ion battery, lithium ions flow between a negatively charged anode, usually graphite, and the positively charged cathode, usually cobalt oxide or lithium iron phosphate. Three years ago, an MIT team led by Belcher reported that it had engineered viruses that could build an anode by coating themselves with cobalt oxide and gold and self-assembling to form a nanowire.

In the latest work, the team focused on building a highly powerful cathode to pair up with the anode, said Belcher, the Germeshausen Professor of Materials Science and Engineering and Biological Engineering. Cathodes are more difficult to build than anodes because they must be highly conducting to be a fast electrode, however, most candidate materials for cathodes are highly insulating (non-conductive).

To achieve that, the researchers, including MIT Professor Gerbrand Ceder of materials science and Associate Professor Michael Strano of chemical engineering, genetically engineered viruses that first coat themselves with iron phosphate, then grab hold of carbon nanotubes to create a network of highly conductive material.

Because the viruses recognize and bind specifically to certain materials (carbon nanotubes in this case), each iron phosphate nanowire can be electrically "wired" to conducting carbon nanotube networks. Electrons can travel along the carbon nanotube networks, percolating throughout the electrodes to the iron phosphate and transferring energy in a very short time.

The viruses are a common bacteriophage, which infect bacteria but are harmless to humans.

The team found that incorporating carbon nanotubes increases the cathode's conductivity without adding too much weight to the battery. In lab tests, batteries with the new cathode material could be charged and discharged at least 100 times without losing any capacitance. That is fewer charge cycles than currently available lithium-ion batteries, but "we expect them to be able to go much longer," Belcher said.

The prototype is packaged as a typical coin cell battery, but the technology allows for the assembly of very lightweight, flexible and conformable batteries that can take the shape of their container.

Last week, MIT President Susan Hockfield took the prototype battery to a press briefing at the White House where she and U.S. President Barack Obama spoke about the need for federal funding to advance new clean-energy technologies.

Now that the researchers have demonstrated they can wire virus batteries at the nanoscale, they intend to pursue even better batteries using materials with higher voltage and capacitance, such as manganese phosphate and nickel phosphate, said Belcher. Once that next generation is ready, the technology could go into commercial production, she said.

Lead authors of the Science paper are Yun Jung Lee and Hyunjung Yi, graduate students in materials science and engineering. Other authors are Woo-Jae Kim, postdoctoral fellow in chemical engineering; Kisuk Kang, recent MIT PhD recipient in materials science and engineering; and Dong Soo Yun, research engineer in materials science and engineering.

The research was funded by the Army Research Office Institute of the Institute of Collaborative Technologies, and the National Science Foundation through the Materials Research Science and Engineering Centers program.

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Journal reference:

1. Yun Jung Lee, Hyunjung Yi, Woo-Jae Kim, Kisuk Kang, Dong Soo Yun, Michael S. Strano, Gerbrand Ceder, and Angela M. Belcher. Fabricating Genetically Engineered High-Power Lithium Ion Batteries Using Multiple Virus Genes. Science, 2009; DOI: 10.1126/science.1171541

Adapted from materials provided by Massachusetts Institute of Technology.

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