Design for new electrode could boost supercapacitors’ performance – UCLA Researchers Design Super-efficient and Long-lasting electrode for Supercapacitors – 10X Efficiency


UCLA SC Boost 163903_webIMAGE: THE BRANCH-AND-LEAVES DESIGN IS MADE UP OF ARRAYS OF HOLLOW, CYLINDRICAL CARBON NANOTUBES (THE ‘BRANCHES’) AND SHARP-EDGED PETAL-LIKE STRUCTURES (THE ‘LEAVES’) MADE OF GRAPHENE. view more  CREDIT: UCLA ENGINEERING

Engineers from UCLA, 4 other universities produce nanoscale device that mimics the structure of tree branches

UCLA HENRY SAMUELI SCHOOL OF ENGINEERING OF APPLIED SCIENCE

Mechanical engineers from the UCLA Henry Samueli School of Engineering and Applied Science and four other institutions have designed a super-efficient and long-lasting electrode for supercapacitors. The device’s design was inspired by the structure and function of leaves on tree branches, and it is more than 10 times more efficient than other designs.

 

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The branch-and-leaves design is made up of arrays of hollow, cylindrical carbon nanotubes (the “branches”) and sharp-edged petal-like structures (the “leaves”) made of graphene.

The electrode design provides the same amount of energy storage, and delivers as much power, as similar electrodes, despite being much smaller and lighter. In experiments it produced 30 percent better capacitance — a device’s ability to store an electric charge — for its mass compared to the best available electrode made from similar carbon materials, and 30 times better capacitance per area. It also produced 10 times more power than other designs and retained 95 percent of its initial capacitance after more than 10,000 charging cycles.

Their work is described in the journal Nature Communications.

Supercapacitors are rechargeable energy storage devices that deliver more power for their size than similar-sized batteries. They also recharge quickly, and they last for hundreds to thousands of recharging cycles. Today, they’re used in hybrid cars’ regenerative braking systems and for other applications. Advances in supercapacitor technology could make their use widespread as a complement to, or even replacement for, the more familiar batteries consumers buy every day for household electronics.

Engineers have known that supercapacitors could be made more powerful than today’s models, but one challenge has been producing more efficient and durable electrodes. Electrodes attract ions, which store energy, to the surface of the supercapacitor, where that energy becomes available to use. Ions in supercapacitors are stored in an electrolyte solution. An electrode’s ability to deliver stored power quickly is determined in large part by how many ions it can exchange with that solution: The more ions it can exchange, the faster it can deliver power.

Knowing that, the researchers designed their electrode to maximize its surface area, creating the most possible space for it to attract electrons. They drew inspiration from the structure of trees, which are able to absorb ample amounts of carbon dioxide for photosynthesis because of the surface area of their leaves.

“We often find inspiration in nature, and plants have discovered the best way to absorb chemicals such as carbon dioxide from their environment,” said Tim Fisher, the study’s principal investigator and a UCLA professor of mechanical and aerospace engineering. “In this case, we used that idea but at a much, much smaller scale — about one-millionth the size, in fact.”

To create the branch-and-leaves design, the researchers used two nanoscale structures composed of carbon atoms. The “branches” are arrays of hollow, cylindrical carbon nanotubes, about 20 to 30 nanometers in diameter; and the “leaves” are sharp-edged petal-like structures, about 100 nanometers wide, that are made of graphene — ultra thin sheets of carbon. The leaves are then arranged on the perimeter of the nanotube stems. The leaf-like graphene petals also give the electrode stability.

The engineers then formed the structures into tunnel-shaped arrays, which the ions that transport the stored energy flow through with much less resistance between the electrolyte and the surface to deliver energy than they would if the electrode surfaces were flat.

The electrode also performs well in acidic conditions and high temperatures, both environments in which supercapacitors could be used.

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Fisher directs UCLA’s Nanoscale Transport Research Group and is a member of the California NanoSystems Institute at UCLA. Lei Chen, a professor at Mississippi State, was the project’s other principal investigator. The first authors are Guoping Xiong of the University of Nevada, Reno, and Pingge He of Central South University. The research was supported by the Air Force Office of Scientific Research.

 

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Battery-free implantable medical device powered by human body – A biological supercapacitor


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Researchers from UCLA and the University of Connecticut have designed a new biofriendly energy storage system called a biological supercapacitor, which operates using charged particles, or ions, from fluids in the human body. The device is harmless to the body’s biological systems, and it could lead to longer-lasting cardiac pacemakers and other implantable medical devices.   The UCLA team was led by Richard Kaner, a distinguished professor of chemistry and biochemistry, and of materials science and engineering, and the Connecticut researchers were led by James Rusling, a professor of chemistry and cell biology.

A paper about their design was published this week in the journal Advanced Energy Materials.   Pacemakers — which help regulate abnormal heart rhythms — and other implantable devices have saved countless lives. But they’re powered by traditional batteries that eventually run out of power and must be replaced, meaning another painful surgery and the accompanying risk of infection. In addition, batteries contain toxic materials that could endanger the patient if they leak.

The researchers propose storing energy in those devices without a battery. The supercapacitor they invented charges using electrolytes from biological fluids like blood serum and urine, and it would work with another device called an energy harvester, which converts heat and motion from the human body into electricity — in much the same way that self-winding watches are powered by the wearer’s body movements. That electricity is then captured by the supercapacitor.   “Combining energy harvesters with supercapacitors can provide endless power for lifelong implantable devices that may never need to be replaced,” said Maher El-Kady, a UCLA postdoctoral researcher and a co-author of the study.

Modern pacemakers are typically about 6 to 8 millimeters thick, and about the same diameter as a 50-cent coin; about half of that space is usually occupied by the battery. The new supercapacitor is only 1 micrometer thick — much smaller than the thickness of a human hair — meaning that it could improve implantable devices’ energy efficiency. It also can maintain its performance for a long time, bend and twist inside the body without any mechanical damage, and store more charge than the energy lithium film batteries of comparable size that are currently used in pacemakers.   “Unlike batteries that use chemical reactions that involve toxic chemicals and electrolytes to store energy, this new class of biosupercapacitors stores energy by utilizing readily available ions, or charged molecules, from the blood serum,” said Islam Mosa, a Connecticut graduate student and first author of the study.

The new biosupercapacitor comprises a carbon nanomaterial called graphene layered with modified human proteins as an electrode, a conductor through which electricity from the energy harvester can enter or leave. The new platform could eventually also be used to develop next-generation implantable devices to speed up bone growth, promote healing or stimulate the brain, Kaner said.

Although supercapacitors have not yet been widely used in medical devices, the study shows that they may be viable for that purpose.   “In order to be effective, battery-free pacemakers must have supercapacitors that can capture, store and transport energy, and commercial supercapacitors are too slow to make it work,” El-Kady said. “Our research focused on custom-designing our supercapacitor to capture energy effectively, and finding a way to make it compatible with the human body.”   Among the paper’s other authors are the University of Connecticut’s Challa Kumar, Ashis Basu and Karteek Kadimisetty. The research was supported by the National Institute of Health’s National Institute of Biomedical Imaging and Bioengineering, the NIH’s National Institute of Environmental Health Sciences, and a National Science Foundation EAGER grant.   Source and top image: UCLA Engineering

 

MIT: The Internet of Things ~ A RoadMap to a Connected World And  … The Super-Capacitors and Batteries Needed to Power ‘The Internet of Things”


The Internet of Things: Roadmap to a Connected World ~ The Sensors ~ The Super Capacitors and Batteries Needed to Power the IoT

Provided by: MIT PE: Dr. S. Sarma

The rapidly increasing number of interconnected devices and systems today brings both benefits and concerns. In this column and a new MIT Professional Education class, the head of MIT’s open and digital learning efforts discusses how to successfully navigate the IoT.

What if every vehicle, home appliance, heating system and light switch were connected to the Internet? Today, that’s not such a stretch of the imagination.

Modern cars, for instance, already have hundreds of sensors and multiple computers connected over an internal network. And that’s just one example of the 6.4 billion connected “things” in use worldwide this year, according to research by Gartner Inc. DHL and Cisco Systems offer even higher estimates—their 2015 Trend Report sets the current number of connected devices at about 15 billion, amidst industry expectations that the tally will increase to 50 billion by 2020.

The Internet of Things (IoT)—a sophisticated network of objects embedded with electronic systems that enable them to collect and exchange data—is disrupting technology and changing the way we live. 

Fewer than two decades ago, if I’d predicted that the IoT would transform the auto-rental industry, people would have laughed. Yet here we are now in the age of Zipcar. By pioneering a range of connected technologies, the car-sharing company has unlocked greater convenience for customers and kick-started the sharing economy. Now the functionality of IoT-enabled cars is transforming the auto industry—from the ultra-connected Tesla to Google’s self-driving cars—and Uber hopes one day to chauffeur you to your destination in an autonomous vehicle.

The IoT is ultimately bound to affect almost every aspect of daily life. In fact, I encourage you to try to figure out where the IoT will not be. But how “smart” is it to let the IoT pervade everything in our lives, without active and purposeful design?

Read About: How Smart-Nano Materials will Change the World Around Us

Watch a Video Presentation About a New Energy Company Making the Super-Capacitors and Batteries that will Power the IoT

 

The IoT: Then and Now

About 18 years ago, as a mechanical engineering professor at MIT, I worked with my colleagues to launch the research effort that laid some of the groundwork for the IoT.

In those early days, our goals were to help implement the radio-frequency identification (RFID) systems that would become integral to connected devices, and to work on developing a standard for data from those devices. At that time, we were excited by the potential for a world of networked things.

Since then, the IoT has expanded into many corners of society and industry, but I’ve become increasingly concerned about its security implications.

How ‘smart’ is it to let the Internet of Things pervade everything in our lives, without active and purposeful design?

I will address such concerns in my new MIT Professional Education online course, Internet of Things: Roadmap to a Connected World.

While we’ll focus on the future of IoT and its business potential, we’ll also tackle its significant challenges, which range from security, privacy, and authenticity issues to the desirable features of a distributed architecture for a network of things.

The IoT’s underlying challenge is that there are no clear and agreed-upon architectures for building connected systems. Your light switch may have one level of data-security encryption, while your TV remote control has another.
Wireless protocols may differ, too: One device might use ZigBee while others rely on Bluetooth or Wi-Fi. Bridges to connect across all these options will proliferate. And even if independent systems are secure, we will have to cobble them together—and the resulting chain will only be as strong as the weakest link.

Controlling the Chaos


By creating new procedures, standards, and best practices, we can bring order to the disorder the IoT generates. As the IoT grows, we should focus on three primary issues:

1. Agreement on system architecture. Today, the IoT is an abstract collection of uses and products. It’s imperative that we establish paradigms for effective implementation and use.

2. Development of open standards reflecting the best architectural choices. Standards for communication between connected things do exist. But there are simply too many standards, each serving a different purpose. The result: a series of silos. For instance, think about how the blood oxygen sensor on a patient’s finger can be affected by what’s happening with the blood pressure monitor on his or her arm. Neither device is necessarily designed to share data.

Open standards, rather than a series of private ones, are necessary to facilitate genuine inter-connectedness. But the deeper question is how and why we need to make these connections, as well as how to extract value from them. This is where cloud computing comes in. Perhaps instead of having the sensors talk to each other directly, they need to talk in the cloud. (I’ll discuss this more in our online course.)

3. Creation of a “test bed” where best practices can be designed and perfected. While the first two needs are best handled by industry, the test bed platform is best created by the government. Remember that the current Internet would not have existed without the early leadership of the U.S. Advanced Research Projects Agency (now called the Defense Advanced Research Projects Agency, or DARPA.) Today, the government could create a similar agency to incubate academic institutions, labs, and companies testing and working on best practices for the IoT.

A ‘Smarter’ Future  
No question about it: The IoT will influence everything from robots and retail to buildings and banking. To leverage the power of the IoT responsibly and profitably, you need to develop and implement your own IoT technologies, solutions, and applications.

Dr. Sanjay Sarma: MIT Professional Education Course: Internet of Things: Roadmap to a Connected World. This six-week course is designed to help you better understand the IoT—and, ultimately, harness its power. 

Transparent, flexible supercapacitors pave the way for a multitude of applications


transparentf Super CapacitorsThe transparent, flexible supercapacitor prototype, based on single-walled carbon nanotube thin films, is shown during charging and discharging. Credit: Kanninen et al. ©2016 IOP Publishing

The standard appearance of today’s electronic devices as solid, black objects could one day change completely as researchers make electronic components that are transparent and flexible. Working toward this goal, researchers in a new study have developed transparent, flexible supercapacitors made of carbon nanotube films. The high-performance devices could one day be used to store energy for everything from wearable electronics to photovoltaics.

The researchers, Kanninen et al., from institutions in Finland and Russia, have published a paper on the new supercapacitors in a recent issue of Nanotechnology.

In general, supercapacitors can store several times more charge in a given volume or mass than traditional capacitors, have faster charge and discharge rates, and are very stable. Over the past few years, researchers have begun working on making supercapacitors that are transparent and flexible due to their potential use in a wide variety of applications.

“Potential applications can be roughly divided into two categories: high-aesthetic-value products, such as activity bands and smart clothes, and inherently transparent end-uses, such as displays and windows,” coauthor Tanja Kallio, an associate professor at Aalto University who is currently a visiting professor at the Skolkovo Institute of Science and Technology, told Phys.org. “The latter include, for example, such future applications as smart windows for automobiles and aerospace vehicles, self-powered rolled-up displays, self-powered wearable optoelectronics, and electronic skin.”

The type of supercapacitor developed here, called an electrochemical double-layer capacitor, is based on high-surface-area carbon. One prime candidate for this material is single-walled carbon nanotubes due to their combination of many appealing properties, including a , high strength, high elasticity, and the ability to withstand extremely high currents, which is essential for fast charging and discharging.

The problem so far, however, has been that the carbon nanotubes must be prepared as in order to be used as electrodes in supercapacitors. Current techniques for preparing thin films have drawbacks, often resulting in defected nanotubes, limited conductivity, and other performance limitations.

In the new study, the researchers demonstrated a new method to fabricate thin films made of single-walled carbon nanotubes using a one-step aerosol synthesis method. When incorporated into a supercapacitor, the thin films exhibit the highest transparency to date (92%), the highest mass specific capacitance (178 F/g), and one of the highest area specific capacitances (552 µF/cm2) compared to other carbon-based, flexible, transparent supercapacitors. The films also have a high stability, as demonstrated by the fact that their capacitance does not degrade after 10,000 charging cycles.

With these advantages, the new device illustrates the continued improvement in the development of transparent, flexible supercapacitors. In the future, the researchers plan to further improve the energy density, flexibility, and durability, and also make the supercapacitors stretchable.

“One more important characteristic to be realized and urgently expected in future electronics is the stretchability of the conductive materials and assembled electronic components,” said coauthor Albert Nasibulin, a professor at the Skolkovo Institute of Science and Technology and an adjunct professor at Aalto University. “Together with Tanja, we are currently working on a new type of stretchable and transparent single-walled carbon nanotube supercapacitor. We are confident that one can create prototypes based on carbon nanotubes that might withstand 100% elongation with no performance degradation.”

Explore further: Researchers develop stretchable wire-shaped supercapacitor

More information: Kanninen et al. “Transparent and flexible high-performance supercapacitors based on single-walled carbon nanotube films.” Nanotechnology. DOI: 10.1088/0957-4484/27/23/235403

 

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MIT & University of British Columbia: Nano-Supercapacitors Tiny wires could Provide a Big Energy Boost


Yarn made of niobium nanowires, seen here in a scanning electron microscope image (background), can be used to make very efficient supercapacitors, MIT researchers have found. Adding a coating of a conductive polymer to the yarn (shown in pink, inset) further increases the capacitor’s charge capacity. Positive and negative ions in the material are depicted as blue and red spheres.

Yarns of niobium nanowire can make supercapacitors to provide a surge of energy when it’s needed

Wearable electronic devices for health and fitness monitoring are a rapidly growing area of consumer electronics; one of their biggest limitations is the capacity of their tiny batteries to deliver enough power to transmit data. Now, researchers at MIT and in Canada have found a promising new approach to delivering the short but intense bursts of power needed by such small devices.

The key is a new approach to making supercapacitors — devices that can store and release electrical power in such bursts, which are needed for brief transmissions of data from wearable devices such as heart-rate monitors, computers, or smartphones, the researchers say. They may also be useful for other applications where high power is needed in small volumes, such as autonomous microrobots.

The new approach uses yarns, made from nanowires of the element niobium, as the electrodes in tiny supercapacitors (which are essentially pairs of electrically conducting fibers with an insulator between). The concept is described in a paper in the journal ACS Applied Materials and Interfaces by MIT professor of mechanical engineering Ian W. Hunter, doctoral student Seyed M. Mirvakili, and three others at the University of British Columbia.

Nanotechnology researchers have been working to increase the performance of supercapacitors for the past decade. Among nanomaterials, carbon-based nanoparticles — such as carbon nanotubes and graphene — have shown promising results, but they suffer from relatively low electrical conductivity, Mirvakili says.

In this new work, he and his colleagues have shown that desirable characteristics for such devices, such as high power density, are not unique to carbon-based nanoparticles, and that niobium nanowire yarn is a promising an alternative.

“Imagine you’ve got some kind of wearable health-monitoring system,” Hunter says, “and it needs to broadcast data, for example using Wi-Fi, over a long distance.” At the moment, the coin-sized batteries used in many small electronic devices have very limited ability to deliver a lot of power at once, which is what such data transmissions need.

“Long-distance Wi-Fi requires a fair amount of power,” says Hunter, the George N. Hatsopoulos Professor in Thermodynamics in MIT’s Department of Mechanical Engineering, “but it may not be needed for very long.” Small batteries are generally poorly suited for such power needs, he adds.

“We know it’s a problem experienced by a number of companies in the health-monitoring or exercise-monitoring space. So an alternative is to go to a combination of a battery and a capacitor,” Hunter says: the battery for long-term, low-power functions, and the capacitor for short bursts of high power. Such a combination should be able to either increase the range of the device, or — perhaps more important in the marketplace — to significantly reduce size requirements.

The new nanowire-based supercapacitor exceeds the performance of existing batteries, while occupying a very small volume. “If you’ve got an Apple Watch and I shave 30 percent off the mass, you may not even notice,” Hunter says. “But if you reduce the volume by 30 percent, that would be a big deal,” he says: Consumers are very sensitive to the size of wearable devices.

The innovation is especially significant for small devices, Hunter says, because other energy-storage technologies — such as fuel cells, batteries, and flywheels — tend to be less efficient, or simply too complex to be practical when reduced to very small sizes. “We are in a sweet spot,” he says, with a technology that can deliver big bursts of power from a very small device.

Ideally, Hunter says, it would be desirable to have a high volumetric power density (the amount of power stored in a given volume) and high volumetric energy density (the amount of energy in a given volume). “Nobody’s figured out how to do that,” he says. However, with the new device, “We have fairly high volumetric power density, medium energy density, and a low cost,” a combination that could be well suited for many applications.

Niobium is a fairly abundant and widely used material, Mirvakili says, so the whole system should be inexpensive and easy to produce. “The fabrication cost is cheap,” he says. Other groups have made similar supercapacitors using carbon nanotubes or other materials, but the niobium yarns are stronger and 100 times more conductive. Overall, niobium-based supercapacitors can store up to five times as much power in a given volume as carbon nanotube versions.

Niobium also has a very high melting point — nearly 2,500 degrees Celsius — so devices made from these nanowires could potentially be suitable for use in high-temperature applications.

In addition, the material is highly flexible and could be woven into fabrics, enabling wearable forms; individual niobium nanowires are just 140 nanometers in diameter — 140 billionths of a meter across, or about one-thousandth the width of a human hair.

So far, the material has been produced only in lab-scale devices. The next step, already under way, is to figure out how to design a practical, easily manufactured version, the researchers say.

“The work is very significant in the development of smart fabrics and future wearable technologies,” says Geoff Spinks, a professor of engineering at the University of Wollongong, in Australia, who was not associated with this research. This paper, he adds, “convincingly demonstrates the impressive performance of niobium-based fiber supercapacitors.”

The team also included PhD student Mehr Negar Mirvakili and professors Peter Englezos and John Madden, all from the University of British Columbia.