2010/06/22 21:56野澤 哲生=日経エレクトロニクス
共同研究のメンバー(の一部)。左から,学生のBetar Gallant氏,第一著者の一人のSeung Woo Lee氏,教授のYang Shao-Horn氏と同 Paula Hammond氏。(写真提供:MIT)
米Massachusetts Institute of Technology(MIT)は,カーボン・ナノチューブを含む混合材料を正極材料に用いたLiイオン2次電池を開発した。Liイオン2次電池とキャパシタの両方の性能を備えるという。具体的には,出力密度は一般的なLiイオン2次電池の10倍,エネルギー密度は一般的なキャパシタの5倍になった。論文が2010年6月20日付けの「Nature Nanotechnology」に掲載された。この電池を開発したのは,MITのDepartment of Chemical Engineering ProfessorのPaula T.Hammond氏と,同Department of Mechanical Engineering兼同Department of Materials Science and Engineering ProfessorのYang Shao-Horn氏の研究グループ。ちなみに,論文の第一著者は,同大学 学生のSeung Woo Lee氏と,ポスト博士課程の薮内直明氏の二人である。開発した電池では,正極に多層カーボン・ナノチューブ(MWNT)と有機材料の混合材料,負極にチタン酸リチウム(Li4Ti5O12:LTO)を用いた。「正極にMWNTを用いたのはこれが初めてのはず」(MIT)という。正極の構造を詳しく説明すると,MWNTとカルボキシル基を結合させたMWNT-COOHの層,およびMWNTとアミノ基を結合させたMWNT-NH2の層を,それぞれの溶液に電極を浸すことで交互に100層弱から最大400層(2種類の層を1組とすると最大200組)重ねて作製する。2種類の層の一方は正に,もう一方は負に帯電しているため,積層することで互いに強固に結合するという。論文によれば,この電池の特徴は非常に高い出力が可能で,しかもその際にエネルギー密度が高いこと。「低出力時のエネルギー密度は,一般のLiイオン2次電池とあまり違いがないが,高出力時には今回の電池がより大きな性能を示す」(論文)という。具体的には,今回の電池の単位質量当たりのエネルギー密度は,出力密度が100kW/kgの場合に200Wh/kg。低出力時の最大エネルギー密度は約500Wh/kgである。ただしこれらは,電極のみの質量に対する値である。電池全体の質量に対しては,「これらの値のおおよそ1/5になる」(論文)。つまり,出力密度が約20kW/kgの場合にエネルギー密度約40Wh/kg,低出力時の最大エネルギー密度は約100Wh/kgとなる。「一般的なLiイオン2次電池は,電池の質量に対して出力密度1kW/kgの場合にエネルギー密度が150Wh/kg。一般的なキャパシタなら,その質量に対して電力密度10kW/kgの場合に5Wh/kg」(論文)。これらの既存の電池やキャパシタと比較すると,今回の電池は,「出力密度でLiイオン2次電池の約5倍,エネルギー密度でキャパシタの約10倍の性能を備える」(論文)。電池の充放電サイクル特性は,1000回以上充放電を繰り返しても性能の劣化は見られなかったという。
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「再生可能エネルギー」と「蓄電システム」の組合わせが人類の希望です。蓄電システムは世界的に新しい技術が生まれ始めています。大容量電気二重層キャパシタ、リチウムイオン電池、リチウムイオンキャパシタ等。「人類の明るい希望」(2008年から)
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※twitterでUCニュース配信はじめました。ユーザー名 a77a フォロー自由です
2010/06/23
2010/06/11
Saying goodbye to batteries
Researchers at MIT are developing a new device that has the potential to hold as much energy as a conventional battery but could be recharged in seconds rather than hours, would last almost indefinitely, and won’t mind the cold. The device could prove the first economically viable alternative to today’s battery. It could one day yield a practical all-electric car and provide electricity storage critical to using intermittent energy sources such as solar and wind.Just about everything that runs on batteries—cell phones, laptops, electric cars, missile-guidance systems—would be improved with a better energy-storage device. The battery continues to improve, but its basic concept hasn’t changed much since it was developed by Alessandro Volta in the 19th century.
Professor Joel E. Schindall of electrical engineering and computer science believes that what’s needed is a novel way of thinking. “I’m intrigued with the idea of using nanotechnology to transform ‘discarded’ technologies into the technology of choice,” he said. Now, using nanotube structures, he and his colleagues Professor John Kassakian and graduate student Riccardo Signorelli at MIT’s Laboratory for Electromagnetic and Electronic Systems are making a “synthetic battery” based on the ultracapacitor, an energy-storage device that’s been around since the 1960s and is used in many electronic devices to provide quick bursts of energy.
Conventional batteries store energy by using chemical reactions to trap ions that move from one electrode to the other. Batteries have a huge storage capacity, but—because of the chemistry involved—electricity can go in and out only so fast, and some is lost as heat.
In contrast, capacitors store energy in an electric field. The absence of chemical reactions has advantages. Capacitors can deliver energy quickly, and they can be charged up in minutes or even seconds. They can withstand temperature changes, shocks, and vibrations. And they can be recharged hundreds of thousands of times before they wear out. They’re thus much easier on the environment than today’s batteries, which must be tossed out after a few hundred charges.
But their capacity for storing energy is limited. The best version is the ultracapacitor. It contains an electrolyte, a fluid containing positive and negative ions; and its electrodes are coated with activated carbon, which is extremely porous and so provides a large surface area for storing the ions. Nevertheless, today’s commercial ultracapacitors store around 25 times less energy than a similarly sized lithium-ion battery can. As a result, they need to be much larger than batteries to hold the same charge.
Novel nanostructure
While ultracapacitors have many uses, they can’t compete with batteries when it comes to storing lots of electrical energy, noted Schindall. But a few years ago he read a journal article about vertically aligned nanotubes and began to wonder what would happen if he replaced the activated carbon with nanotubes. While the pores in activated carbon are irregular in size and shape, a nanotube “forest” might provide straight pathways so the ions could come in and out easily and pack together neatly—like sucking up paint with a paintbrush rather than a sponge.
Schindall and his colleagues have now developed a technique for growing nanotubes on an aluminum electrode. They put down droplets of a catalyst on the surface and pass a hydrocarbon gas over it at high temperature. The droplets grab carbon atoms out of the gas, and carbon nanotubes start growing upward, just like hair. Within ten minutes the surface is covered with millions of vertically aligned nanotubes, each one a thirty-thousandth the diameter of a human hair and 50,000 times as long as they are wide. By controlling the size and spacing of the droplets, they have made samples in which the nanotubes are just two ion-diameters apart—ideal for dense ion packing.
Detailed simulations suggest that their new device will work well. Indeed, the predicted energy-storage capacity is comparable to that of a lithium battery of equivalent dimensions—a similarity that they realized is no coincidence. The lattice structure of their device provides roughly the same storage space for ions as a battery does.
"When we were done, we realized that it wasn’t really a capacitor anymore," Schindall said. "Our adapted ultracapacitor actually mimics the molecular lattice of a battery but without the chemical reactions. It’s sort of a synthetic battery." The device could be made in all the sizes needed to replace today’s commercially available batteries—at roughly the same cost.
Schindall expects to have a working prototype finished in the next few months. If all goes well, the new nanotube-enhanced ultracapacitor could be on the market within five to ten years.
—Nancy Stauffer
This work is partially funded by a grant from the Ford-MIT Alliance.
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Professor Joel E. Schindall of electrical engineering and computer science believes that what’s needed is a novel way of thinking. “I’m intrigued with the idea of using nanotechnology to transform ‘discarded’ technologies into the technology of choice,” he said. Now, using nanotube structures, he and his colleagues Professor John Kassakian and graduate student Riccardo Signorelli at MIT’s Laboratory for Electromagnetic and Electronic Systems are making a “synthetic battery” based on the ultracapacitor, an energy-storage device that’s been around since the 1960s and is used in many electronic devices to provide quick bursts of energy.
Conventional batteries store energy by using chemical reactions to trap ions that move from one electrode to the other. Batteries have a huge storage capacity, but—because of the chemistry involved—electricity can go in and out only so fast, and some is lost as heat.
In contrast, capacitors store energy in an electric field. The absence of chemical reactions has advantages. Capacitors can deliver energy quickly, and they can be charged up in minutes or even seconds. They can withstand temperature changes, shocks, and vibrations. And they can be recharged hundreds of thousands of times before they wear out. They’re thus much easier on the environment than today’s batteries, which must be tossed out after a few hundred charges.
But their capacity for storing energy is limited. The best version is the ultracapacitor. It contains an electrolyte, a fluid containing positive and negative ions; and its electrodes are coated with activated carbon, which is extremely porous and so provides a large surface area for storing the ions. Nevertheless, today’s commercial ultracapacitors store around 25 times less energy than a similarly sized lithium-ion battery can. As a result, they need to be much larger than batteries to hold the same charge.
Novel nanostructure
While ultracapacitors have many uses, they can’t compete with batteries when it comes to storing lots of electrical energy, noted Schindall. But a few years ago he read a journal article about vertically aligned nanotubes and began to wonder what would happen if he replaced the activated carbon with nanotubes. While the pores in activated carbon are irregular in size and shape, a nanotube “forest” might provide straight pathways so the ions could come in and out easily and pack together neatly—like sucking up paint with a paintbrush rather than a sponge.
Schindall and his colleagues have now developed a technique for growing nanotubes on an aluminum electrode. They put down droplets of a catalyst on the surface and pass a hydrocarbon gas over it at high temperature. The droplets grab carbon atoms out of the gas, and carbon nanotubes start growing upward, just like hair. Within ten minutes the surface is covered with millions of vertically aligned nanotubes, each one a thirty-thousandth the diameter of a human hair and 50,000 times as long as they are wide. By controlling the size and spacing of the droplets, they have made samples in which the nanotubes are just two ion-diameters apart—ideal for dense ion packing.
Detailed simulations suggest that their new device will work well. Indeed, the predicted energy-storage capacity is comparable to that of a lithium battery of equivalent dimensions—a similarity that they realized is no coincidence. The lattice structure of their device provides roughly the same storage space for ions as a battery does.
"When we were done, we realized that it wasn’t really a capacitor anymore," Schindall said. "Our adapted ultracapacitor actually mimics the molecular lattice of a battery but without the chemical reactions. It’s sort of a synthetic battery." The device could be made in all the sizes needed to replace today’s commercially available batteries—at roughly the same cost.
Schindall expects to have a working prototype finished in the next few months. If all goes well, the new nanotube-enhanced ultracapacitor could be on the market within five to ten years.
—Nancy Stauffer
This work is partially funded by a grant from the Ford-MIT Alliance.
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Nanotube Superbatteries
Dense films of carbon nanotubes store large amounts of energy.
By Katherine Bourzac Friday, January 09, 2009
Pure power: Pure thin films of carbon nanotubes can store and carry large amounts of electrical charge, making them promising electrode materials. This scanning-electron-microscope image shows a film made up of 30 layers of the nanotubes on a silicone substrate.
Credit: Journal of the American Chemical Society
Researchers at MIT have made pure, dense, thin films of carbon nanotubes that show promise as electrodes for higher-capacity batteries and supercapacitors. Dispensing with the additives previously used to hold such films together improved their electrical properties, including the ability to carry and store a large amount of charge.
Carbon nanotubes can carry and store more charge than other forms of carbon, in part because their nanoscale structure gives them a very large surface area. But conventional methods for making them into films leave significant gaps between individual nanotubes or require binding materials to hold them together. Both approaches reduce the films' conductivity--the ability to convey charge--and capacitance--the ability to store it.
The MIT group, led by chemical-engineering professor Paula Hammond and mechanical-engineering professor Yang Shao-Horn, made the new nanotube films using a technique called layer-by-layer assembly. First, the group creates water solutions of two kinds of nanotubes: one type has positively charged molecules bound to them, and the other has negatively charged molecules. The researchers then alternately dip a very thin substrate, such as a silicon wafer, into the two solutions. Because of the differences in their charge, the nanotubes are attracted to each other and hold together without the help of any glues. And nanotubes of similar charge repel each other while in solution, so they form thin, uniform layers with no clumping.
The resulting films can then be detached from the substrate and baked in a cloud of hydrogen to burn off the charged molecules, leaving behind a pure mat of carbon nanotubes. The films are about 70 percent nanotubes; the rest is empty space, pores that could be used to store lithium or liquid electrolytes in future battery electrodes. The films "can store a lot of energy and discharge it rapidly," says Hammond. The capacitance of the MIT films--that is, their ability to store electrical charge--is one of the highest ever measured for carbon-nanotube films, says Shao-Horn. This means that they could serve as electrodes for batteries and supercapacitors that charge quickly, have a high power output, and have a long life.
The MIT group is not the first to use the layering technique to create nanotube films. But previously, researchers using the method layered a positively charged polymer with negatively charged nanotubes, resulting in films that were only half nanotubes. No polymer can equal the electrical conductivity of carbon nanotubes, so these films' electrical properties weren't as impressive as those of Hammond and Shao-Horn. Others have made films by growing the nanotubes from the substrate up, but the resulting forest of vertically aligned nanotubes is insufficiently dense.
"I see particular importance of these findings for supercapacitors, because all-nanotube materials can potentially store a greater amount of charge," says Nicholas Kotov, a professor of chemical engineering and materials science at the University of Michigan.
In addition to their high capacitance, the nanotube films have other advantages as electrode materials, says Shao-Horn. Conventional high-energy-density electrodes are made of carbon powder held together with a binder. But particles of the binder in the surface of the electrode reduce its active area and make it difficult to modify. With carbon nanotubes, says Shao-Horn, "you have systematic control of surface chemistry." Adding charged molecules to the electrodes' surface, for example, could increase their capacitance and energy density.
"Many researchers are pursuing thin films of carbon nanotubes for diverse applications in electronics, energy storage, and other areas," says John Rogers, a professor of materials science and engineering at the University of Illinois at Champaign-Urbana. The MIT group is primarily focused on developing the films for electrochemical applications like batteries, but the layering technique is versatile. By varying the pH of the nanotube solutions and the number of layers in the films, it's possible to tailor the films' electrical properties. This is "an attractive feature of this approach," says Rogers. The technique could be used to make nanotube films for flexible electronics, for example. Kotov also sees other potential uses of the nanotube films. When immersed in liquid, the films swell. "This will be useful, because it changes both the conductivity and capacity of the material, which opens up a lot of prospects for sensing applications and smart coatings," says Kotov.
The layer-by-layer method is time consuming, however. Typical electrodes are 10 to 100 micrometers thick; those that the MIT group has made so far are only about 1 micrometer thick. But Hammond, a pioneer in layer-by-layer assembly of polymers, has developed a layer-by-layer spraying technique that should be adaptable to nanotubes. "This reduces the time it takes by an order of magnitude, which will be necessary for commercial development," says Shao-Horn.
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By Katherine Bourzac Friday, January 09, 2009
Pure power: Pure thin films of carbon nanotubes can store and carry large amounts of electrical charge, making them promising electrode materials. This scanning-electron-microscope image shows a film made up of 30 layers of the nanotubes on a silicone substrate.
Credit: Journal of the American Chemical Society
Researchers at MIT have made pure, dense, thin films of carbon nanotubes that show promise as electrodes for higher-capacity batteries and supercapacitors. Dispensing with the additives previously used to hold such films together improved their electrical properties, including the ability to carry and store a large amount of charge.
Carbon nanotubes can carry and store more charge than other forms of carbon, in part because their nanoscale structure gives them a very large surface area. But conventional methods for making them into films leave significant gaps between individual nanotubes or require binding materials to hold them together. Both approaches reduce the films' conductivity--the ability to convey charge--and capacitance--the ability to store it.
The MIT group, led by chemical-engineering professor Paula Hammond and mechanical-engineering professor Yang Shao-Horn, made the new nanotube films using a technique called layer-by-layer assembly. First, the group creates water solutions of two kinds of nanotubes: one type has positively charged molecules bound to them, and the other has negatively charged molecules. The researchers then alternately dip a very thin substrate, such as a silicon wafer, into the two solutions. Because of the differences in their charge, the nanotubes are attracted to each other and hold together without the help of any glues. And nanotubes of similar charge repel each other while in solution, so they form thin, uniform layers with no clumping.
The resulting films can then be detached from the substrate and baked in a cloud of hydrogen to burn off the charged molecules, leaving behind a pure mat of carbon nanotubes. The films are about 70 percent nanotubes; the rest is empty space, pores that could be used to store lithium or liquid electrolytes in future battery electrodes. The films "can store a lot of energy and discharge it rapidly," says Hammond. The capacitance of the MIT films--that is, their ability to store electrical charge--is one of the highest ever measured for carbon-nanotube films, says Shao-Horn. This means that they could serve as electrodes for batteries and supercapacitors that charge quickly, have a high power output, and have a long life.
The MIT group is not the first to use the layering technique to create nanotube films. But previously, researchers using the method layered a positively charged polymer with negatively charged nanotubes, resulting in films that were only half nanotubes. No polymer can equal the electrical conductivity of carbon nanotubes, so these films' electrical properties weren't as impressive as those of Hammond and Shao-Horn. Others have made films by growing the nanotubes from the substrate up, but the resulting forest of vertically aligned nanotubes is insufficiently dense.
"I see particular importance of these findings for supercapacitors, because all-nanotube materials can potentially store a greater amount of charge," says Nicholas Kotov, a professor of chemical engineering and materials science at the University of Michigan.
In addition to their high capacitance, the nanotube films have other advantages as electrode materials, says Shao-Horn. Conventional high-energy-density electrodes are made of carbon powder held together with a binder. But particles of the binder in the surface of the electrode reduce its active area and make it difficult to modify. With carbon nanotubes, says Shao-Horn, "you have systematic control of surface chemistry." Adding charged molecules to the electrodes' surface, for example, could increase their capacitance and energy density.
"Many researchers are pursuing thin films of carbon nanotubes for diverse applications in electronics, energy storage, and other areas," says John Rogers, a professor of materials science and engineering at the University of Illinois at Champaign-Urbana. The MIT group is primarily focused on developing the films for electrochemical applications like batteries, but the layering technique is versatile. By varying the pH of the nanotube solutions and the number of layers in the films, it's possible to tailor the films' electrical properties. This is "an attractive feature of this approach," says Rogers. The technique could be used to make nanotube films for flexible electronics, for example. Kotov also sees other potential uses of the nanotube films. When immersed in liquid, the films swell. "This will be useful, because it changes both the conductivity and capacity of the material, which opens up a lot of prospects for sensing applications and smart coatings," says Kotov.
The layer-by-layer method is time consuming, however. Typical electrodes are 10 to 100 micrometers thick; those that the MIT group has made so far are only about 1 micrometer thick. But Hammond, a pioneer in layer-by-layer assembly of polymers, has developed a layer-by-layer spraying technique that should be adaptable to nanotubes. "This reduces the time it takes by an order of magnitude, which will be necessary for commercial development," says Shao-Horn.
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Directory:MIT Nanotube Super Capacitor
Nanotube filaments on the battery's electrodes
image: MIT/Riccardo Signorelli
Official Website
No official company yet. Still in research and development at MIT.
http://lees.mit.edu/lees/schindall_j.htm
Carbon Nanotube Enhanced Double Layer Capacitor (pdf)
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image: MIT/Riccardo Signorelli
Official Website
No official company yet. Still in research and development at MIT.
http://lees.mit.edu/lees/schindall_j.htm
Carbon Nanotube Enhanced Double Layer Capacitor (pdf)
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2009/04/24
「数秒で充電可能な新型バッテリー」:MIT開発
2009年3月12日

Photo:新しいバッテリーの素材/MIT。なお、サイトトップの画像はリヒテンベルク図形。Wikimedia Commonsより
現在ノートパソコン等に使用されているリチオムイオンより100倍速く充電できるという新しいバッテリー素材が開発された。
マサチューセッツ工科大学(MIT)で開発されたこの研究は、10秒で充電可能な、携帯電話サイズのバッテリーを生み出す可能性がある。
「これまで数時間かかっていたバッテリーの充電と放電を数秒間で行なえる能力によって、新たな工学的用途が生まれ、生活スタイルの変化につながるだろう」と、材料科学を専門とする研究者であるGerbrand Ceder氏とByoungwoo Kang氏は、『Nature』誌の3月11日号に掲載された論文に書いている。
エネルギー貯蔵においては、材料が蓄積できるエネルギーの量と充放電時間は、常に両立しないものだった。バッテリーはエネルギーの蓄積に関してはかなり優秀(石油とは比較にならないものの)だったが、エネルギーの入出力には難しい点があった。ウルトラキャパシタと、同類のスーパーキャパシタは非常に迅速に大量の充電を行なえるが、同程度のバッテリーと同量のエネルギーを蓄積するのに、20倍の材料が必要となる。
[ウルトラキャパシタやスーパーキャパシタは、電気二重層コンデンサとも呼ばれる。電気二重層という物理現象を利用することで蓄電効率が著しく高められたコンデンサ(キャパシタ)]
今回の新しいバッテリー素材は、イオンがリン酸鉄リチウムの周りを動き回る際の「高速レーン」を作ることで、上述の問題を解決しているようだ。以前の材料に特殊な表面コーティングを施すことで、ほとんど想像できないような速度でイオンがバッテリーの中を疾走できるようにしている。
Ceder氏はこのバッテリーが2〜3年以内に市場に出ると考えている。この技術はすでに2つの企業によってライセンスされている。
ただし、疑問は残る。米国立リニューアブル・エネルギー研究所のRob Farrington氏は、高速充電は確かに便利だと指摘しながらも、それには大量の電流をバッテリーに流して高熱化させることになり、結果としてバッテリーの寿命が短くなるのではないかという懸念を示した。
MITの2人の研究者による『Nature』誌の論文には、充電を50回繰り返した場合のデータしか示されていないが、「バッテリー容量はほとんど減っていない」という非常に期待のできる結果が出ている。
だがノートパソコンの所有者なら誰でも知っているように、充電回数が増えれば増えるほど、バッテリーに充電される電力量は少なくなる。2年前には喫茶店で3時間使えたバッテリーが、今では1時間半しか持たない。
ウルトラキャパシタが他のどのバッテリーよりも優位に立ちそうなのが、まさにこの点だ。
「1日に何度も充電と放電を繰り返す必要のある用途は多数存在するが、そうした用途において、ウルトラキャパシタはその強みを発揮する」と、MITでカーボン・ナノチューブベースのウルトラキャパシタを開発する研究プロジェクトを率いるJoel Schindall氏は述べる。
ウルトラキャパシタの生産者たちはこうした強みを携えてニッチ市場に進出しているものの、重量または容量当たりでリチウムイオン・バッテリーとほぼ同量のエネルギーを蓄積するウルトラキャパシタをなかなか生み出せずにいる。
Schindall氏の研究プロジェクトが話題になったのは、『MIT Technology Review』が「この画期的な技術によって、電子機器の充電が数分で完了し、バッテリー交換が不要になり、ハイブリッド自動車の価格が一気に下がる可能性がある」と絶賛した2006年のことだった。
{この翻訳は抄訳です}
参考論文: "Battery materials for ultrafast charging and discharging" by Byoungwoo Kang & Gerbrand Ceder doi:10.1038/nature07853
[日本語版:ガリレオ-天野美保]
WIRED NEWS 原文(English)
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Photo:新しいバッテリーの素材/MIT。なお、サイトトップの画像はリヒテンベルク図形。Wikimedia Commonsより
現在ノートパソコン等に使用されているリチオムイオンより100倍速く充電できるという新しいバッテリー素材が開発された。
マサチューセッツ工科大学(MIT)で開発されたこの研究は、10秒で充電可能な、携帯電話サイズのバッテリーを生み出す可能性がある。
「これまで数時間かかっていたバッテリーの充電と放電を数秒間で行なえる能力によって、新たな工学的用途が生まれ、生活スタイルの変化につながるだろう」と、材料科学を専門とする研究者であるGerbrand Ceder氏とByoungwoo Kang氏は、『Nature』誌の3月11日号に掲載された論文に書いている。
エネルギー貯蔵においては、材料が蓄積できるエネルギーの量と充放電時間は、常に両立しないものだった。バッテリーはエネルギーの蓄積に関してはかなり優秀(石油とは比較にならないものの)だったが、エネルギーの入出力には難しい点があった。ウルトラキャパシタと、同類のスーパーキャパシタは非常に迅速に大量の充電を行なえるが、同程度のバッテリーと同量のエネルギーを蓄積するのに、20倍の材料が必要となる。
[ウルトラキャパシタやスーパーキャパシタは、電気二重層コンデンサとも呼ばれる。電気二重層という物理現象を利用することで蓄電効率が著しく高められたコンデンサ(キャパシタ)]
今回の新しいバッテリー素材は、イオンがリン酸鉄リチウムの周りを動き回る際の「高速レーン」を作ることで、上述の問題を解決しているようだ。以前の材料に特殊な表面コーティングを施すことで、ほとんど想像できないような速度でイオンがバッテリーの中を疾走できるようにしている。
Ceder氏はこのバッテリーが2〜3年以内に市場に出ると考えている。この技術はすでに2つの企業によってライセンスされている。
ただし、疑問は残る。米国立リニューアブル・エネルギー研究所のRob Farrington氏は、高速充電は確かに便利だと指摘しながらも、それには大量の電流をバッテリーに流して高熱化させることになり、結果としてバッテリーの寿命が短くなるのではないかという懸念を示した。
MITの2人の研究者による『Nature』誌の論文には、充電を50回繰り返した場合のデータしか示されていないが、「バッテリー容量はほとんど減っていない」という非常に期待のできる結果が出ている。
だがノートパソコンの所有者なら誰でも知っているように、充電回数が増えれば増えるほど、バッテリーに充電される電力量は少なくなる。2年前には喫茶店で3時間使えたバッテリーが、今では1時間半しか持たない。
ウルトラキャパシタが他のどのバッテリーよりも優位に立ちそうなのが、まさにこの点だ。
「1日に何度も充電と放電を繰り返す必要のある用途は多数存在するが、そうした用途において、ウルトラキャパシタはその強みを発揮する」と、MITでカーボン・ナノチューブベースのウルトラキャパシタを開発する研究プロジェクトを率いるJoel Schindall氏は述べる。
ウルトラキャパシタの生産者たちはこうした強みを携えてニッチ市場に進出しているものの、重量または容量当たりでリチウムイオン・バッテリーとほぼ同量のエネルギーを蓄積するウルトラキャパシタをなかなか生み出せずにいる。
Schindall氏の研究プロジェクトが話題になったのは、『MIT Technology Review』が「この画期的な技術によって、電子機器の充電が数分で完了し、バッテリー交換が不要になり、ハイブリッド自動車の価格が一気に下がる可能性がある」と絶賛した2006年のことだった。
{この翻訳は抄訳です}
参考論文: "Battery materials for ultrafast charging and discharging" by Byoungwoo Kang & Gerbrand Ceder doi:10.1038/nature07853
[日本語版:ガリレオ-天野美保]
WIRED NEWS 原文(English)
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2009/04/15
2009/03/31
MITの研究者、リチウムイオン電池の電極改善でイオンの易動度大幅改善。EDLC並Building a better battery
http://cosmiclog.msnbc.msn.com/archive/2009/03/11/1831393.aspx
MSNBC - USA
... a combination power source of a fast-charge battery as described in this article paired with a supercapacitor to provide burst power for acceleration? ...
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2009/03/25
MIT、ショックアブソーバ発電でハイブリッド車の燃費を10%改善可能かも。・・・"could"を使用
Shock absorber harvests energy
Prototype device to take over much of the work now performed by
alternators.
http://www.automotivedesignline.com/showArticle.jhtml?articleID=214200169&cid=NL_autodl
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Green X Prize Challenge to Focus on Advanced Energy Storage
http://www.greenbiz.com/news/2009/02/06/green-x-prize-energy-storage
GreenBiz - Oakland,CA,USA
UC Irvine students Kyle Good and Bryan Le won $25000 for their entry, The Capacitor Challenge, which asks entrants to develop an advanced ultracapacitor, ...
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MIT Clean Energy Prize for University Students: $200000
http://cleantechnica.com/2009/02/06/mit-clean-energy-prize-for-university-students-200000/
CleanTechnica - San Francisco,CA,USA
Don’t think you can rise up to the X PRIZE ultracapacitor challenge? Maybe you should go for MIT’s Clean Energy Prize instead. The competition, which is ...
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2008/08/07
EEStor Joining Other Energy Storage Startups on the Grid
http://earth2tech.com/2008/08/06/eestor-joining-other-energy-storage-startups-on-the-grid/
EEStor, maker of the supposedly killer energy storage device, might soon plug its “electrical energy storage unit” (EESU) into the grid to help solve renewable energy’s intermittent power generation problem of when the sun doesn’t shine and the wind doesn’t blow. MIT Technology Review reports that the stealthy Austin, Texas-based startup is in “serious talks” with potential solar and wind energy partners to help boost grid capacity by providing utility-scale electricity storage. But before EEStor puts its EESUs on the grid it will have start making them and CEO Dick Weir has said production will start by the end of 2009.
EEStor(おそらくすごいエネルギー記憶装置のメーカー)は太陽がいつ輝かないかという再生可能エネルギーの断続的な発電問題を解決するのを助けるためにその「電気エネルギー記憶装置」(EESU)を格子にすぐに接続するかもしれません、そして、風は吹きません。MIT Technology Reviewはそれを報告します内密のオースティン、テキサスに拠点を置くスタートアップは有用性スケール電気保管を提供することによって格子能力を高めるのを助けるために潜在的太陽のおよび風力エネルギーパートナーと「重大な会談」です。しかし、EEStorがそのEESUsをグリッドに置く前に、それは彼らを作っているスタートを持ちます、そして、CEOディックウィアーは生産が2009年内に始まると言いました。
EEStor joins AltairNano and A123 Systems as startups looking to connect their energy storage devices to the grid. The idea is that large capacity, fast-charging storage devices could sit on the grid, storing and providing energy to the grid as necessary. Excess energy generated at night could be stored and then used during the day during peak demand. Large, static storage devices could allow operators more flexibility and help renewable energy offer a stable base load. Weir claims that by partnering with wind and solar energy producers, EEStor could put 45 percent more energy on the grid.
EEStorは、彼らのエネルギー記憶装置を格子に接続するために見ているスタートアップとして、AltairNanoとA123 Systemsに加わります。考えは大きな容量、高速充電記憶装置が格子に位置することができたということです。そして、必要に応じてエネルギーを格子へ保存して、供給します。夜に発生する過剰なエネルギーが、保存されることができて、それからピークの要求の間、日中使われることができました。大きな、静的記憶装置は、より多くの柔軟性をオペレーターに与えることができて、再生可能エネルギーが安定したベースロードを提供するのを助けることができました。堰は、風と太陽エネルギー製作者と組むことによって、EEStorが格子にもう45パーセントのエネルギーを与えることができたと主張します。
AltairNano is developing ceramic lithium-ion batteries with nano-structured materials that allow for large amounts of surface area for fast charging. AltairNano’s new CEO Terry Copeland told us earlier this summer that the startup had successfully charged and discharged two megawatts of power to the grid in 30 minutes from one of their batteries in a partnership with AES.
AltairNanoは、速く料金を請求するために大量の表面積を考慮に入れるナノ体系化された材料で、陶製リチウムイオン電池を開発しています。AltairNanoの新任のCEOテリーコープランドは、スタートアップがAESとの協力で彼らのバッテリーのうちの1つから30分で格子にうまく2メガワットの力の充電および放電を行ったとこの夏、以前に我々に話しました。
Battery darling A123 Systems said in June it is already working with its investor General Electric to use its lithium-ion batteries for “grid stabilization.” Ric Fulop, founder and vice president of business development, said on a panel of energy storage experts organized by the New England Clean Energy Council that the battery technology is already there. “Now it’s a question of building the systems. Megawatt-level systems are all about systems integration.”
バッテリーダーリンA123 Systemsは、6月に、「格子安定化のためにそのリチウムイオン電池を使うことがその投資家ジェネラルエレクトリックとともにすでに働いていると言いました。」、Ricファロップ(ビジネス開発の創始者と副社長)は、バッテリー技術がすでにそこにあるニューイングランドClean Energy会議によって組織されるエネルギー保管の専門家委員会の上で言いました。「現在、それはシステムを構築する問題です。メガワットレベルのシステムのすべては、システム統合についてです。」
EEStor has a long way to go before it tackles systems integration. The startup just had its materials verified for purity and consistency, a necessary step, but far off from a working EESU. “I’m not going to make claims on when we’re going to get product out there,” Weir Told MIT Tech Review unapologetically. “That’s between me and the customer. I don’t want to tell the industry.”
それがシステム統合に取り組む前に、EEStorは行く長い道のりを持ちます。スタートアップは、ちょうどその材料を純度と一貫性(必要なステップ)のために確かめられるが、働くEESUから遠くしました。「私は、我々がいつ製品を向こうに得るつもりかという請求をするつもりでありません」、ウィアーTold MIT技術Review unapologetically.、「それは、私と顧客の間にあります。私は、産業を言いたくありません。」
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2008/07/31
How Quantum Physics Could Power the Future
A theoretical model of a quantum dot made out of the semiconductor material gallium arsenide. The dot contains just 465 atoms. Credit: Lin-Wang Wang/Lawrence Berkeley Laboratory
http://www.livescience.com/environment/080730-pf-quantum-enviro.html
How Quantum Physics Could Power the Future
量子物理学は、どのように将来の原動力となることができましたかBy Michael Schirber, Special to
posted: 30 July 2008 09:11 am ET
Editor's Note: Each Wednesday LiveScience examines the viability of emerging energy technologies — the power of the future.
エディタの注: 各水曜日に、LiveScienceは新生のエネルギー技術の生存能力を調べます — 将来の力。
The strange behavior of quantum physics might seem too unpredictable to rely on for our energy needs, but new technologies hope to capitalize on its very strangeness.
量子物理学の変な作用は我々のエネルギーニーズを頼るにはあまりに予測できないようかもしれません、しかし、新技術はそのまさしくその珍しさを利用することを望みます。
The most familiar of these quantum tricks is the fact that light acts both like a wave and a particle.
これらの量子トリックで最もおなじみのものは、光が波と小片のようにふるまうという事実です。
This dual nature is utilized in solar power technology. Incoming sunlight is concentrated by mirrors and lenses that rely on the wave-like properties of light. Once inside a solar cell, however, this focused light collides with electrons in a particle-like way, thus freeing the electrons to create an electric current.
この二重自然は、太陽エネルギー技術で利用されます。入って来る日光は、光の波状の特性に頼る鏡とレンズで集中されます。一度太陽電池の中に、しかし、この焦束された光は小片のような方向で電子と衝突します。このように、電流をつくるために電子を解きます。
Quantum dots
量子点
The next generation of solar cells may employ tiny bits of semiconductor material called quantum dots. These nanometer-sized devices are so small that only a handful (anywhere from 1 to 1,000) of free electrons can reside inside.
太陽電池の次世代は、量子点と呼ばれている半導体材の小さいビットを使用するかもしれません。これらのナノメートルサイズの装置は、自由電子の厄介もの(1から1,000までどこでも)だけが中で住むことができるように小さいです。
Because of these cramped quarters, a quantum dot behaves like an artificial atom in that its electrons can reside only at specific (so-called quantized) energy levels. These levels define exactly what wavelengths of light the dot will absorb.
これらの窮屈な4分の1のため、その電子が特定の(いわゆる量子化された)エネルギー準位だけに住むことができるという点で、量子点は人工原子のようにふるまいます。これらのレベルは、点が光のどんな波長を吸収するかについて、正確に定めます。
"Quantum dots have a host of unusual properties compared to bulk semiconductors," said Arthur Nozik of the National Renewable Energy Laboratory, part of the U.S. Department of Energy. He and his colleagues are looking at how a single light particle (or photon) can enter a dot and excite several electrons, rather than the usual one.
「量子点には、大きさ半導体と比較して多数の変わった特性があります」と、国立RenewableなEnergy Laboratory(米エネルギー省の一部)のアーサーNozikが言いました。彼と彼の同僚は、一つの軽い粒子(または光子)が点を入力することができて、いくつかの電子(普通のものよりむしろ)を励起することができる方法を見ています。
Other researchers are looking to tune the wavelengths at which a dot absorbs light by making it bigger or smaller. Solar cell manufacturers may one day be able to mix together dots of different sizes to absorb sunlight along a wide range of wavelengths.
他の研究者は、点がそれをより大きいかより小さくすることによって光を吸収する波長を調整するのを期待しています。太陽電池メーカーは、ある日、広範囲にわたる波長に沿って日光を吸収するために異なるサイズの点を混ぜ合わせることができるかもしれません。
Quantum wires
量子ケーブル
A quantum wire is like a quantum dot stretched out along one direction. In certain cases, this narrow conduit — 10,000 times thinner than a human hair — can be very good at conducting electricity, as the electrons tend to move in a more orderly fashion down the wire.
量子ケーブルは、1つの方向に沿って伸ばされる量子点のようです。特定のケース(この細いパイプ)で — 人間の髪より10,000回細い — 電子がワイヤーの下により整然としたやり方で動く傾向があって、電気を伝導することが非常に上手でありえます。
One way to make quantum wires is with carbon nanotubes, which are small rolled-up sheets of hexagonally-bound carbon. Discovered in 1991, these nanotubes are beginning to show up in all types of applications, including better energy storage.
量子ケーブルを製造する1つの方法はカーボンナノチューブです。そして、それは六角形に縛られたカーボンの小さな巻かれた板です。1991年に発見されて、これらのナノチューブは、より良いエネルギー保管を含むさまざまなアプリケーションで現れ始めています。
As one MIT group has shown, it is possible to make a souped-up capacitor from carbon nanotubes. The researchers grow the nanotubes close together — in what is likely the world's tiniest shag carpet — to increase surface area inside the capacitor.
1 つのMITグループが示したように、カーボンナノチューブからパワーアップしたコンデンサを製造することは可能です。研究者は、一緒にナノチューブ終わりを発達させます — たぶん世界の最も小さいウカーペットであることで — コンデンサの中に表面積を増やすこと。
The resulting "ultracapacitor" could store as much as 50 percent of the electricity that a similarly-sized battery can, the scientists claim. This might be ideal inside an electric car, as capacitors are more durable and can charge and discharge much faster than batteries.
結果として生じる「ultracapacitor」は同じようにサイズのバッテリーがそうすることができる電気の50パーセントも保存することができたと、科学者が主張します。コンデンサがより耐久性があって、バッテリーより非常に速く充電および放電を行うことができて、これは電気自動車の中に理想的かもしれません。
Superconductors
超伝導体
Although quantum wires can be good conductors, another quantum substance is the best.
量子ケーブルが良いコンダクターでありえるが、もう一つの量子物質は最高です。
Superconductors are materials in which the electrons pair up to carry the current. This pairing is unusual because electrons typically repel each other, but quantum physics overcomes this and, in so doing, reduces the electrical resistance in the superconductor to zero, or very close to zero.
超伝導体は、電子が流れをもたらすためにペアになる材料です。電子が一般的に互いをはね返すので、この組合せは珍しいです、しかし、量子物理学はこれを克服して、とてもする際に、ゼロまたは非常に0近くまで超伝導体で電気抵抗を減らします。
Resistance is what makes a wire get hot when it carries electricity. Power companies typically lose about 7 percent of their energy to heat caused by resistance in transmission wires.
抵抗は、それが電気をもたらすとき、ワイヤーを熱くならせることです。電力会社は、一般的に、伝達ワイヤーで抵抗に起因する熱に、彼らのエネルギーのおよそ7パーセントを失います。
Superconducting wires could help reduce this waste. The trouble is that superconductors only work at extremely cold temperatures.
超伝導ワイヤーは、この無駄を還元するのを助けることができました。トラブルは、超伝導体がとても冷えた温度で働くだけであるということです。
For example, the longest superconducting cable system for transmitting power — installed earlier this year along a half-mile stretch of the Long Island power grid by American Superconductor Corporation and its partners — must be surrounded by liquid nitrogen to keep it at minus 330 degrees Fahrenheit (minus 200 degrees Celsius).
たとえば、力を伝導するために最も長い超伝導ケーブルシステム — アメリカンスーパーコンダクター社とそのパートナーによってロングアイランド送電網の半マイル範囲に沿って、今年始め装置されます — それを華氏マイナス330度(摂氏マイナス200度)に保つために、液体窒素によって囲まれなければなりません。
American Superconductor is also working on applying its superconducting wires to offshore wind turbines, in order to make them smaller and more efficient.
アメリカのSuperconductorも、彼らをより小さくてより効率的にするために、沖合風力タービンにその超伝導針金を塗ることに取り組んでいます。
Light-emitting diodes
発光ダイオード
One good way to use all this quantum-derived electricity is to turn on a light-emitting diode, or LED, which works like a solar cell but in reverse.
このような量子由来の電気を使う1つの良い方法は発光ダイオードまたはLEDをつけることになっています、そしてそれは、作品はリバースで太陽電池を以外好みます。
Electric current going through the diode causes electrons to jump across a barrier between two types of semiconductor material. The jumping electrons then fall into lower energy states, emitting a photon.
ダイオードによって行っている電流は、電子が2種類の半導体材の間の障壁全体でとぶ原因になります。跳ぶ電子はそれから下のエネルギー状態に落ちます。そして、光子を発します。
Because the wavelength of this emitted light is in a very narrow band, there is not a lot of wasted energy emitted in the infrared, as is the case for normal incandescent light bulbs. An LED's efficiency is even better than that of compact fluorescents.
この発された光の波長が非常に狭いバンドの中にあるので、通常の白熱電球の場合のように、赤外線で発される多くの無駄になるエネルギーがありません。LEDの効率は、小さい蛍光のそれよりさらによいです。
LEDs are now being made into full light fixtures that can replace normal bulbs. Their extra cost can be offset by lower electricity bills.
LEDは、現在、通常の電球にとって代わることができる強烈な照明設備になっています。彼らの追加コストは、低い電気代で相殺されることができます。
In the energy saving business, every quantum bit can help.
省エネルギービジネスにおいて、あらゆる量子ビットは助けることができます。
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