First Fully Rechargeable Carbon Dioxide Battery is Seven Times More Efficient Than Lithium Ion


CO2 Battery 1 Unmarked-Batteries-Public-Domain-via-Pxhere

Carbon Dioxide Battery is Seven Times More Efficient Than Lithium Ion

Lithium-carbon dioxide batteries are attractive energy storage systems because they have a specific energy density that is more than seven times greater than commonly used lithium-ion batteries. Until now, however, scientists have not been able to develop a fully rechargeable prototype, despite their potential to store more energy.

Researchers at the University of Illinois at Chicago are the first to show that lithium-carbon dioxide batteries can be designed to operate in a fully rechargeable manner, and they have successfully tested a lithium-carbon dioxide battery prototype running up to 500 consecutive cycles of charge/recharge processes.

Their findings are published in the journal Advanced Materials.

“Lithium-carbon dioxide batteries have been attractive for a long time, but in practice, we have been unable to get one that is truly efficient until now,” said Amin Salehi-Khojin, associate professor of mechanical and industrial engineering at UIC’s College of Engineering.

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Traditionally, when a lithium-carbon dioxide battery discharges, it produces lithium carbonate and carbon. The lithium carbonate recycles during the charge phase, but the carbon just accumulates on the catalyst, ultimately leading to the battery’s failure.

rechargeable-carbon-dioxide-battery

Lithium–CO2 batteries are attractive energy‐storage systems for fulfilling the demand of future large‐scale applications such as electric vehicles due to their high specific energy density.

“The accumulation of carbon not only blocks the active sites of the catalyst and prevents carbon dioxide diffusion, but also triggers electrolyte decomposition in a charged state,” said Alireza Ahmadiparidari, first author of the paper and a UIC College of Engineering graduate student.

Salehi-Khojin and his colleagues used new materials in their experimental carbon dioxide battery to encourage the thorough recycling of both lithium carbonate and carbon. They used molybdenum disulfide as a cathode catalyst combined with a hybrid electrolyte to help incorporate carbon in the cycling process.

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Specifically, their combination of materials produces a single multi-component composite of products rather than separate products, making recycling more efficient.

“Our unique combination of materials helps make the first carbon-neutral lithium carbon dioxide battery with much more efficiency and long-lasting cycle life, which will enable it to be used in advanced energy storage systems,” Salehi-Khojin said.

This research was supported, in part, by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, and a grant from the National Science Foundation.

Reprinted from the University of Illinois-Chicago

U of Illinois: Tiny nanoclusters could solve big problems for lithium-ion batteries


mit-solid-electrolyte-1

Illustrations show the crystal structure of a superionic conductor. 
tinynanoclusIllinois professor Prashant Jain’s research group found that ultrasmall nanoclusters of copper selenide could make superionic solid electrolytes for next-generation lithium-ion batteries. Credit: L. Brian Stauffer

As devices become smaller and more powerful, they require faster, smaller, more stable batteries. University of Illinois chemists have developed a superionic solid that could be the basis of next-generation lithium-ion batteries.

Chemistry professor Prashant Jain and graduate students Sarah White and Progna Banerjee described the material – ultrasmall nanoclusters of copper selenide – in the journal Nature Communications.

“Now that we’re seeing this nanoelectronics boom, we need tiny batteries that can be put on a chip, and that can’t happen with liquid electrolytes,” Jain said. “We are using nanostructured materials to achieve the properties at the heart of lithium-ion technology. They have much more thermal and mechanical stability, there are no leakage issues, and we can make extremely thin electrolyte layers so we can miniaturize batteries.”

Standard and other ionic batteries are filled with a liquid electrolyte that the lithium ions move through. The ions flow one direction when the battery is being used, and the opposite direction when the battery is charged. However, liquid electrolytes have several drawbacks: They require volume, degrade as the battery cycles, leak and are highly flammable, which has led to explosions in phones, laptops and other devices. Though solid electrolytes are considerably more stable, ions move through them much more slowly, making them less efficient for battery applications.

The copper selenide nanocluster electrolyte combines the best of both liquid and solid electrolytes: It has the stability of a solid, but ions easily move through it like a liquid. Copper selenide is known to be superionic at high temperatures, but the tiny nanoclusters are the first demonstration of the material being superionic at .

The researchers discovered this superionic property by accident while investigating copper selenide’s surface reactivity. They noticed that ultrasmall nanoclusters – about 2 nanometers in diameter – looked very different from larger copper selenide nanoparticles in an electron microscope.

“That was our first hint that they have different structures,” Jain said. “We investigated further, and we realized that these small clusters are actually semiliquid at room temperature.”

The reason for the semiliquid, superionic property is the special structure of the nanoclusters, Jain said. The much larger selenium ions form a crystal lattice, while the smaller ions move around them like a liquid. This crystal structure is a result of internal strain in the clusters.

“With around 100 atoms, these nanoclusters are right at the interface of molecules and nanoparticles,” Jain said. “Right now, the big push is to make every nanoparticle in a sample exactly the same size and shape. It turns out with these clusters, every single cluster is exactly the same structure. Somehow, at this size, the electronic structure of the material is so stable that every single cluster has the same arrangement of atoms.”

The researchers are working to incorporate the nanoclusters into a battery, measure the conductivity of lithium ions and compare the performance with existing solid-state electrolytes and liquid electrolytes.

Explore further: Solid electrolytes open doors to solid-state batteries

More information: Sarah L. White et al, Liquid-like cationic sub-lattice in copper selenide clusters, Nature Communications (2017). DOI: 10.1038/ncomms14514

 

Electricity generated with water, salt and a three-atoms-thick membrane: NEW Osmotic Power


Electricity from Water Salt - 3 Atoms 072016 578660a2f2413A molybdenum 3-atoms-thick selective membrane. Credit: © Steven Duensing / National Center for Supercomputing Applications, University of Illinois, Urbana-Champaign

Proponents of clean energy will soon have a new source to add to their existing array of solar, wind, and hydropower: osmotic power. Or more specifically, energy generated by a natural phenomenon occurring when fresh water comes into contact with seawater through a membrane.

Researchers at EPFL’s Laboratory of Nanoscale Biology have developed an osmotic power generation system that delivers never-before-seen yields. Their innovation lies in a three atoms thick membrane used to separate the two fluids. The results of their research have been published in Nature.

The concept is fairly simple. A semipermeable membrane separates two fluids with different salt concentrations. Salt- travel through the membrane until the salt concentrations in the two fluids reach equilibrium. That phenomenon is precisely osmosis.

If the system is used with seawater and fresh water, salt ions in the seawater pass through the membrane into the fresh water until both fluids have the same salt concentration. And since an ion is simply an atom with an electrical charge, the movement of the can be harnessed to generate electricity.

A 3 atoms thick, selective membrane that does the job

EPFL’s system consists of two liquid-filled compartments separated by a thin membrane made of molybdenum disulfide. The membrane has a tiny hole, or nanopore, through which seawater ions pass into the until the two fluids’ salt concentrations are equal. As the ions pass through the nanopore, their electrons are transferred to an electrode – which is what is used to generate an electric current.

Thanks to its properties the membrane allows positively-charged ions to pass through, while pushing away most of the negatively-charged ones. That creates voltage between the two liquids as one builds up a positive charge and the other a negative charge. This voltage is what causes the current generated by the transfer of ions to flow.

“We had to first fabricate and then investigate the optimal size of the nanopore. If it’s too big, can pass through and the resulting voltage would be too low. If it’s too small, not enough ions can pass through and the current would be too weak,” said Jiandong Feng, lead author of the research.

What sets EPFL’s system apart is its membrane. In these types of systems, the current increases with a thinner membrane. And EPFL’s membrane is just a few atoms thick. The material it is made of – molybdenum disulfide – is ideal for generating an osmotic current. “This is the first time a two-dimensional material has been used for this type of application,” said Aleksandra Radenovic, head of the laboratory of Nanoscale Biology

Powering 50’000 energy-saving light bulbs with 1m2 membrane

The potential of the new system is huge. According to their calculations, a 1m² membrane with 30% of its surface covered by nanopores should be able to produce 1MW of electricity – or enough to power 50,000 standard energy-saving light bulbs. And since (MoS2) is easily found in nature or can be grown by chemical vapor deposition, the system could feasibly be ramped up for large-scale power generation. The major challenge in scaling-up this process is finding out how to make relatively uniform pores.

Until now, researchers have worked on a membrane with a single nanopore, in order to understand precisely what was going on. ” From an engineering perspective, single nanopore system is ideal to further our fundamental understanding of -based processes and provide useful information for industry-level commercialization”, said Jiandong Feng.

The researchers were able to run a nanotransistor from the current generated by a single nanopore and thus demonstrated a self-powered nanosystem. Low-power single-layer MoS2 transistors were fabricated in collaboration with Andreas Kis’ team at at EPFL, while molecular dynamics simulations were performed by collaborators at University of Illinois at Urbana-Champaign

Harnessing the potential of estuaries

EPFL’s research is part of a growing trend. For the past several years, scientists around the world have been developing systems that leverage osmotic power to create electricity. Pilot projects have sprung up in places such as Norway, the Netherlands, Japan, and the United States to generate energy at estuaries, where rivers flow into the sea. For now, the membranes used in most systems are organic and fragile, and deliver low yields. Some systems use the movement of water, rather than ions, to power turbines that in turn produce electricity.

Once the systems become more robust, osmotic power could play a major role in the generation of renewable energy. While solar panels require adequate sunlight and wind turbines adequate wind, osmotic energy can be produced just about any time of day or night – provided there’s an estuary nearby.

More information: Jiandong Feng et al, Single-layer MoS2 nanopores as nanopower generators, Nature (2016). DOI: 10.1038/nature18593

Provided by: Ecole Polytechnique Federale de Lausanne

University of Illinois: Quantum Dots with Equalized Brightness improve Biological Imaging


QD Brightness U of Illinois 100515 id41509Researchers at the University of Illinois at Urbana-Champaign have introduced a new class of light-emitting quantum dots (QDs) with tunable and equalized fluorescence brightness across a broad range of colors. This results in more accurate measurements of molecules in diseased tissue and improved quantitative imaging capabilities.
“In this work, we have made two major advances–the ability to precisely control the brightness of light-emitting particles called quantum dots, and the ability to make multiple colors equal in brightness,” explained Andrew M. Smith, an assistant professor of bioengineering at Illinois. “Previously light emission had an unknown correspondence with molecule number. Now it can be precisely tuned and calibrated to accurately count specific molecules. This will be particularly useful for understanding complex processes in neurons and cancer cells to help us unravel disease mechanisms, and for characterizing cells from diseased tissue of patients.”
Quantum Dots
Left: Conventional fluorescent materials like quantum dots and dyes have mismatched brightness between different colors. When these materials are administered to a tumor (shown below) to measure molecular concentrations, the signals are dominated by the brighter fluorophores. Right: New brightness-equalized quantum dots that have equal fluorescence brightness for different colors. When these are administered to tumors, the signals are evenly matched, allowing measurement of many molecules at the same time. (Image: University of Illinois)
“Fluorescent dyes have been used to label molecules in cells and tissues for nearly a century, and have molded our understanding of cellular structures and protein function. But it has always been challenging to extract quantitative information because the amount of light emitted from a single dye is unstable and often unpredictable. Also the brightness varies drastically between different colors, which complicates the use of multiple dye colors at the same time. These attributes obscure correlations between measured light intensity and concentrations of molecules,” stated Sung Jun Lim, a postdoctoral fellow and first author of the paper, “Brightness-Equalized Quantum Dots,” published this week in Nature Communications.
According to the researchers, these new materials will be especially important for imaging in complex tissues and living organisms where there is a major need for quantitative imaging tools, and can provide a consistent and tunable number of photons per tagged biomolecule. They are also expected to be used for precise color matching in light-emitting devices and displays, and for photon-on-demand encryption applications. The same principles should be applicable across a wide range of semiconducting materials.
“The capacity to independently tune the QD fluorescence brightness and color has never before been possible, and these BE-QDs now provide this capability,” said Lim. “We have developed new materials-engineering principles that we anticipate will provide a diverse range of new optical capabilities, allow quantitative multicolor imaging in biological tissue, and improve color tuning in light-emitting devices. In addition, BE-QDs maintain their equal brightness over time while whereas conventional QDs with mismatched brightness become further mismatched over time. These attributes should lead to new LEDs and display devices not only with precisely matched colors–better color accuracy and brightness–but also with improved performance lifetime and improved ease of manufacturing.” QDs are already in use in display devices (e.g. Amazon Kindle and a new Samsung TV).
Source: University of Illinois College of Engineering

Printing Quantum Dot Displays: Electronics: A new printer uses electric fields to print quantum dots at high resolution for light-emitting diodes


Quantum Glow LED Print 1422381761226Researchers report a high-resolution method for printing quantum dots to make light-emitting diodes (Nano Lett. 2015, DOI: 10.1021/nl503779e). With further development, the technique could be used to print pixels for richly colored, low-power displays in cell phones and other electronic devices.

Quantum dots are appealing materials for displays because engineers can finely tune the light the semiconducting nanocrystals emit by controlling their dimensions.

Electronics makers already use quantum dots in some backlit displays on the market, in which red and green quantum dots convert blue light from a light-emitting diode (LED) into white light. Quantum dots also emit light in response to voltage changes, so researchers are looking into using them in red, green, and blue pixels in displays that wouldn’t need a backlight.

Quantum Glow LED Print 1422381761226

QUANTUM GLOW

With a new printing method, researchers created high-resolution patterns (left) and shapes (right) of red and green quantum dots, shown in these fluorescence images.
Credit: Nano Letters

Quantum dot LED displays should provide richer colors and use less power than the liquid-crystal displays (LCDs) used in many flat screens, which require filters and polarizers that reduce efficiency and limit color quality. But it’s not yet clear how quantum dot LED displays would be made commercially, says John A. Rogers, a materials scientist at the University of Illinois, Urbana-Champaign.

In 2011, researchers at Samsung made the first full-color quantum dot LED display by using a rubber stamp to pick up and transfer quantum dot inks (Nat. Photonics, DOI: 10.1038/nphoton.2011.12). As a manufacturing strategy, printing from ink nozzles would offer more flexibility to change designs on the fly, without the need for making new transfer stamps. Jet printing also would require less material, Rogers says.

Unfortunately, the resolution of conventional ink-jet printers, which use a heating element to force vapor droplets out of a nozzle, is limited. “It’s hard to get droplets smaller than about 25 µm,” Rogers says, because the smaller the nozzle diameter, the more pressure required to get the droplet out.

So for the past seven years, Rogers has been developing another method called electrohydrodynamic jet printing. This kind of printer works by pulling ink droplets out of the nozzle rather than pushing them, allowing for smaller droplets. An electric field at the nozzle opening causes ions to form on the meniscus of the ink droplet. The electric field pulls the ions forward, deforming the droplet into a conical shape. Then a tiny droplet shears off and lands on the printing surface. A computer program controls the printer by directing the movement of the substrate and varying the voltage at the nozzle to print a given pattern.

The Illinois researchers used this new method, including specialized quantum dot inks, to print lines on average about 500 nm wide. This allowed them to fabricate red and green quantum dot LEDs. They also showed they could carefully control the thickness of the printed film, which is difficult to do with stamp transfer and ink-jet printing methods.

The ultimate resolution possible with these kinds of printers is very high, says David J. Norris, a materials engineer at the Swiss Federal Institute of Technology (ETH), Zurich. Last year, Norris used a similar printing method to print spots containing as few as 10 quantum dots (Nano Lett. 2014, DOI: 10.1021/nl5026997). He says it’s even possible to place single quantum dots using electrohydrodynamic nozzles, albeit with less control and repeatability. Single-particle printing isn’t needed for making pixels for displays, but it is useful for studying other kinds of optical effects in quantum dots, he says.

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2015 American Chemical Society

High-Resolution Patterns of Quantum Dots with E-jet printing: Application for High-Def QD Enabled Displays


Q Dot E-Jet Printing highresolutiA team of 17 materials science and engineering researchers from the University of Illinois at Urbana−Champaign and Erciyes University in Turkey have authored “High-Resolution Patterns of Quantum Dots are Formed by Electrohydrodynamic Jet Printing for Light-Emitting Diodes.” Their paper was published in Nano Letters, an ACS journal. They demonstrated the materials and operating conditions that allow for high-resolution printing of layers of quantum dots with precise control over thickness and submicron lateral resolution and capabilities, for use as active layers of QD light-emitting diodes.

They wrote, “Patterning QDs with precise control of their thicknesses and nanoscale lateral dimensions represent two critical capabilities for advanced applications. The thickness can be controlled through a combination of printing parameters including the size of the nozzle, the stage speed, ink composition, and voltage bias.”

Their work on high-resolution patterns of is of interest as it shows that advanced techniques in “e-jet ” offer powerful capabilities in patterning quantum dot materials from solution inks, over large areas. (E-jet printing refers to a technique called electrohydrodynamic jet, described as a micro/nano-manufacturing process that uses an electric field to induce fluid jet printing through micro/nano-scale nozzles.)

Q Dot E-Jet Printing highresoluti

Katherine Bourzac in Chemical & Engineering News wrote about this technique and the research interests of John Rogers, co-author of the paper and a materials scientist at the University of Illinois, Urbana-Champaign. The resolution of conventional ink-jet printers is limited. For the past seven years, she said, Rogers has been developing the electrohydrodynamic jet . “This kind of printer works by pulling ink droplets out of the nozzle rather than pushing them, allowing for smaller droplets.

An electric field at the nozzle opening causes ions to form on the meniscus of the ink droplet. The electric field pulls the ions forward, deforming the droplet into a conical shape. Then a tiny droplet shears off and lands on the printing surface. A computer program controls the printer by directing the movement of the substrate and varying the voltage at the nozzle to print a given pattern.”

Dot, line, square, and complex images as QD patterns are possible, the researchers said, with tunable dimensions and thickness. They wrote that “these arrays as well as those constructed with multiple different QD materials, directly patterned/stacked by e-jet printing, can be utilized as photoluminescent and electroluminescent layers.”

What does their work mean for consumers? As for TV technology, nearly every TV manufacturer at CES this year, remarked Geoffrey Morrison in CNET, said quantum dots helped deliver better, more lifelike color. Writing in IEEE Spectrum on Monday, Prachi Patel similarly made note that “Quantum dots (QDs) are light-emitting semiconductor nanocrystals that, used in (LEDs), hold the promise of brighter, faster displays.”

In the IEEE story headlined “High-Resolution Printing of Quantum Dots For Vibrant, Inexpensive Displays,” Patel said these researchers repurposed a printing method which they devised for other applications. Patel wrote: “When used with ‘QD ink,’ it can create lines and spots that are just 0.25 micrometers wide.

They made arrays and complex patterns of QDs in multiple colors, and could even print QDs on top of others of a different color. They sandwiched these patterns between electrodes to make bright QD LEDs.” Patel also reported on the team’s future efforts. They are working on arrays of multiple nozzles. Inkjet printers usually have a few hundred nozzles, said Patel. “The difficulty with the e-jet printing method is that the at one nozzle affects the fields of neighboring nozzles.” They are trying to figure out “how to isolate nozzles in order to eliminate that crosstalk.”

Explore further: Princeton team explores 3D-printed quantum dot LEDs

More information: High-Resolution Patterns of Quantum Dots Formed by Electrohydrodynamic Jet Printing for Light-Emitting Diodes, Nano Lett., Article ASAP. DOI: 10.1021/nl503779e

Abstract
Here we demonstrate materials and operating conditions that allow for high-resolution printing of layers of quantum dots (QDs) with precise control over thickness and submicron lateral resolution and capabilities for use as active layers of QD light-emitting diodes (LEDs). The shapes and thicknesses of the QD patterns exhibit systematic dependence on the dimensions of the printing nozzle and the ink composition in ways that allow nearly arbitrary, systematic control when exploited in a fully automated printing tool. Homogeneous arrays of patterns of QDs serve as the basis for corresponding arrays of QD LEDs that exhibit excellent performance. Sequential printing of different types of QDs in a multilayer stack or in an interdigitated geometry provides strategies for continuous tuning of the effective, overall emission wavelengths of the resulting QD LEDs. This strategy is useful to efficient, additive use of QDs for wide ranging types of electronic and optoelectronic devices.