Georgia Institute of Technology scientists have developed an anode material that enables sodium-ion batteries to perform at high capacity over hundreds of cycles. Lithium-ion batteries have become essential in everyday technology. But these power sources can explode under certain circumstances and are not ideal for grid-scale energy storage. Sodium-ion batteries are potentially a safer and less expensive alternative, but current versions don’t last long enough yet for practical use.

Sodium Antimony Graphene Anode Activity. Image Credit: American Chemical Society. Click image for the largest view.

The international team’s paper reporting the technology has been published the journal ACS Nano.

Meilin Liu, Chenghao Yang and their colleagues wanted to find an anode material that would give sodium-ion batteries a longer life. The colleagues hail from Georgia Institute of Technology, New Energy Research Institute, School of Environment and Energy, South China University of Technology and Department of Chemistry, National Taiwan Normal University.

For years, scientists have considered sodium-ion batteries a safer and lower-cost candidate for large-scale energy storage than lithium-ion. But so far, sodium-ion batteries have not operated at high capacity for long-term use. Lithium and sodium have similar properties in many ways, but sodium ions are much larger than lithium ions. This size difference leads to the rapid deterioration of a key battery component.

The researchers developed a simple approach to making a high-performance anode material by binding an antimony-based mineral onto sulfur-doped graphene sheets. Incorporating the anode into a sodium-ion battery allowed it to perform at 83 percent capacity over 900 cycles. The researchers say this is the best reported performance for a sodium-ion battery with an antimony-based anode material. To ultimately commercialize their technology, they would need to scale up battery fabrication while maintaining its high performance.

The team’s development is closing in on three years of life with daily charge and discharge cycling. Still in its lab stage of development the technology has lots of work yet to be done. For now the tech is very hopeful, some applications simply can’t tolerate the lithium-ion risk, getting those kinds of devices a higher power lower weight battery is a worthwhile effort, indeed.

University of Illinois at Urbana-Champaign (UI) researchers have invented a new kind of LED that can both emit and detect ambient light. The possibility then becomes that cellphones and other devices could soon be controlled with touchless gestures and charge themselves using ambient light. This would be a major design attribute for the future. Made of tiny nanorods arrayed in a thin film, the LEDs could enable new interactive functions and multitasking devices.

A laser stylus writes on a small array of multifunction pixels made by dual-function LEDs than can both emit and respond to light. Image Credit: Moonsub Shim, University of Illinois at Urbana-Champaign. Click image for the largest view.

The researchers at the University of Illinois at Urbana-Champaign and Dow Electronic Materials in Marlborough, Massachusetts, reported the advance in the journal Science.

Moonsub Shim, a professor of materials science and engineering at the UI and the leader of the study said, “These LEDs are the beginning of enabling displays to do something completely different, moving well beyond just displaying information to be much more interactive devices. That can become the basis for new and interesting designs for a lot of electronics.”

The tiny nanorods, each measuring less than 5 nanometers in diameter, are made of three types of semiconductor material. One type emits and absorbs visible light. The other two semiconductors control how charge flows through the first material. The combination is what allows the LEDs to emit, sense and respond to light.

The nanorod LEDs are able to perform both functions by quickly switching back and forth from emitting to detecting. They switch so fast that, to the human eye, the display appears to stay on continuously – in fact, it’s three orders of magnitude faster than standard display refresh rates. Yet the LEDs are also near-continuously detecting and absorbing light, and a display made of the LEDs can be programmed to respond to light signals in a number of ways.

For example, a display could automatically adjust brightness in response to ambient light conditions – on a pixel-by-pixel basis.

Shim explained, “You can imagine sitting outside with your tablet, reading. Your tablet will detect the brightness and adjust it for individual pixels. Where there’s a shadow falling across the screen it will be dimmer, and where it’s in the sun it will be brighter, so you can maintain steady contrast.”

The researchers demonstrated pixels that automatically adjust brightness, as well as pixels that respond to an approaching finger, which could be integrated into interactive displays that respond to touchless gestures or recognize objects.

They also demonstrated arrays that respond to a laser stylus, which could be the basis of smart whiteboards, tablets or other surfaces for writing or drawing with light. And the researchers found that the LEDs not only respond to light, but can convert it to electricity as well.

“The way it responds to light is like a solar cell. So not only can we enhance interaction between users and devices or displays, now we can actually use the displays to harvest light,” Shim said. “So imagine your cellphone just sitting there collecting the ambient light and charging. That’s a possibility without having to integrate separate solar cells. We still have a lot of development to do before a display can be completely self-powered, but we think that we can boost the power-harvesting properties without compromising LED performance, so that a significant amount of the display’s power is coming from the array itself.”

In addition to interacting with users and their environment, nanorod LED displays can interact with each other as large parallel communication arrays. It would be slower than device-to-device technologies like Bluetooth, Shim said, but those technologies are serial – they can only send one bit at a time. Two LED arrays facing each other could communicate with as many bits as there are pixels in the screen.

Study coauthor Peter Trefonas, a corporate fellow in Electronic Materials at the Dow Chemical Company said, “We primarily interface with our electronic devices through their displays, and a display’s appeal resides in the user’s experience of viewing and manipulating information. The bidirectional capability of these new LED materials could enable devices to respond intelligently to external stimuli in new ways. The potential for touchless gesture control alone is intriguing, and we’re only scratching the surface of what could be possible.”

The researchers did all their demonstrations with arrays of red LEDs. They are now working on methods to pattern three-color displays with red, blue and green pixels, as well as working on ways to boost the light-harvesting capabilities by adjusting the composition of the nanorods.

This is an astonishing development. The possibility to have a cellphone that would charge up as it is standing by or even while in use is a bit numbing. Your humble writer is always, yes, always planning cellphone use so as to make it to the next charge without a shutdown.

The potentials other applications is also a bit numbing. Congratulations UI Urbana-Champaign and Dow Electronic Materials. Very happy you have collaborated and have obtained such an impressive result.

University of Colorado at Boulder engineers have developed an engineered material to act as a kind of air conditioning system for structures.  The new material is a scalable manufactured metamaterial – an engineered material with extraordinary properties not found in nature with the ability to cool objects even under direct sunlight with zero energy and water consumption.

Image Credit: University of Colorado. Click image for the largest view.

When applied to a surface, the metamaterial film cools the object underneath by efficiently reflecting incoming solar energy back into space while simultaneously allowing the surface to shed its own heat in the form of infrared thermal radiation.

The new material, which is described today in the journal Science, could provide an eco-friendly means of supplementary cooling for thermoelectric power plants, which currently require large amounts of water and electricity to maintain the operating temperatures of their machinery.

The researchers’ glass-polymer hybrid material measures just 50 micrometers thick – slightly thicker than the aluminum foil found in a kitchen – and can be manufactured economically on rolls, making it a potentially viable large-scale technology for both residential and commercial applications.

“We feel that this low-cost manufacturing process will be transformative for real-world applications of this radiative cooling technology,” said Xiaobo Yin, co-director of the research and an assistant professor who holds dual appointments in CU Boulder’s Department of Mechanical Engineering and the Materials Science and Engineering Program. Yin received DARPA’s Young Faculty Award in 2015.

The material takes advantage of passive radiative cooling, the process by which objects naturally shed heat in the form of infrared radiation, without consuming energy. Thermal radiation provides some natural nighttime cooling and is used for residential cooling in some areas, but daytime cooling has historically been more of a challenge. For a structure exposed to sunlight, even a small amount of directly-absorbed solar energy is enough to negate passive radiation.

The challenge for the CU Boulder researchers, then, was to create a material that could provide a one-two punch: reflect any incoming solar rays back into the atmosphere while still providing a means of escape for infrared radiation. To solve this, the researchers embedded visibly-scattering but infrared-radiant glass microspheres into a polymer film. They then added a thin silver coating underneath in order to achieve maximum spectral reflectance.

“Both the glass-polymer metamaterial formation and the silver coating are manufactured at scale on roll-to-roll processes,” added Ronggui Yang, also a professor of mechanical engineering and a Fellow of the American Society of Mechanical Engineers.

During field tests in Boulder, Colorado and Cave Creek, Arizona, the metamaterial successfully demonstrated its average radiative cooling power larger than 110W/m2 for continuous 72 hours and larger than 90W/m2 in direct, noon-time sunlight. That cooling power is roughly equivalent to the electricity generated using solar cells for similar area, but the radiative cooling has the advantage of continuous running both day and night.

“Just 10 to 20 square meters of this material on the rooftop could nicely cool down a single-family house in summer,” said Gang Tan, an associate professor in the University of Wyoming’s Department of Civil and Architectural Engineering and a co-author of the paper.

In addition to being useful for cooling of buildings and power plants, the material could also help improve the efficiency and lifetime of solar panels. In direct sunlight, panels can overheat to temperatures that hamper their ability to convert solar rays into electricity.

“Just by applying this material to the surface of a solar panel, we can cool the panel and recover an additional one to two percent of solar efficiency,” said Yin. “That makes a big difference at scale.”

The engineers have applied for a patent for the technology and are working with CU Boulder’s Technology Transfer Office to explore potential commercial applications. They plan to create a 200-square-meter “cooling farm” prototype in Boulder in 2017.

The invention is the result of a $3 million grant awarded in 2015 to Yang, Yin and Tang by the Energy Department’s Advanced Research Projects Agency-Energy (ARPA-E).

“The key advantage of this technology is that it works 24/7 with no electricity or water usage,” said Yang. “We’re excited about the opportunity to explore potential uses in the power industry, aerospace, agriculture and more.”

This is extraordinary news. The press release also leaves some very critical questions unanswered. How tough is this material, standing up to weather across which seasons, it applies to what materials, and on and on.

Yet the result cannot be anything other than a kickoff to a new view of engineering the cooling aspect of a huge array of air-conditioning applications and the costs for both the installation and operating costs. As we saw last week, many anticipate more and higher rate increases coming, so a more efficient cooling system is a major breakthrough.

University of Michigan researchers prepared a new study purporting climate change is likely to increase U.S. electricity costs over the next century. The suggestion is it will cost billions of dollars more than economists have previously forecast.

Electricity costs in the U.S. are expected to increase more steeply than economists have previously forecast due to power grid upgrades necessary to absorb future peak electricity demand. The change in peak intensity varies by region. Regions represent load balancing authorities, which regulators use to examine grid reliability. This map shows the percentage change in the intensity of peak electricity load under a “business as usual” carbon emissions scenario. The largest peak demand increases appear in the south and west. Image credit: University of Michigan. Click image for the largest view.

The study shows how higher temperatures will raise not just the average annual electricity demand, but more importantly, the peak demand. To avoid brownouts and absorb these surges, utilities will need to spend between $70 billion and $180 billion in grid upgrades – power plants and futuristic energy storage systems for which ratepayers would ultimately foot the bill.

Catherine Hausman, assistant professor at U-M’s Gerald R. Ford School of Public Policy said, “If you look at your own bill across the year, you’ll probably see that your usage is highest in the summer, when you’re running the air conditioning. Climate change researchers know that when we look out over the next 100 years, things will get warmer and, on a per-person basis, use of air conditioning will rise. The question we asked was ‘On the hottest day of the year, when people are maxing out on that, can the grid handle it?’ We build the grid for the hottest hour of the year.”

Hausman and colleagues urge electric grid planners to keep their calculations in mind as they draft 20-year procurement plans. They also have a message for policymakers.

“This means that climate change adaptation is going to be more expensive than we thought. And so mitigation efforts become more valuable – more worthwhile – because they can prevent these costs,” said Hausman, who is co-author of the study that appears in the Proceedings of the National Academy of Sciences. “Our findings should inform the cost-benefit calculations of climate change policy.”

The need varies by region. The researchers examined separately each of 166 load-balancing authorities. These are regions that regulators use when they’re examining the grid’s reliability.

To generate their cost figures, the researchers calculated the mathematical relationship between air temperature and electricity in each region. Then they plugged that into simulations that took into account climate models and two different carbon emissions scenarios identified by the Intergovernmental Panel on Climate Change.

One scenario represents “business as usual,” under which carbon emissions would continue to increase. The other is a scenario under which we stabilize emissions. Under both scenarios, if the nation were to experience temperatures like the ones predicted 100 years from now with today’s infrastructure, the grid would be overtaxed.

In the stabilization scenario, demand on an average day would climb 3 percent, and on a peak day, 7 percent. They calculate a 152 percent change in the number of days experiencing the 95th percentile or above of demand. Absorbing this would require an investment of $70 billion.

Under business-as-usual, demand on a peak usage day would spike by 18 percent, and the number of days in the 95th percentile or above would go up by 395 percent. Preparing for this would cost $180 billion.

What exactly would that money pay for? Electricity storage technologies such as grid scale batteries could work, but they’re still in the research phase. Advances in batteries or the use of electric vehicles for storage could smooth the peaks.

The study also nods to “time varying pricing,” which gives customers incentives to reduce their use at peak times. Solar power and wind power could help a bit, but not enough without better energy storage options. The sun and wind aren’t always on at peak demand times. Given the current state of technology, if the projected climate of 2117 were to occur tomorrow, Hausman said we’d need to build more fossil fuel plants to jump in on the highest demand days.

The researchers caution that this isn’t a “prediction” for several reasons. Yes, increasing temperatures may spur greater adoption of air conditioners, and as a result, greater temperature impacts, but they could also hasten development of more efficient air conditioners.

“We’re not trying to say this is the future scenario,” Hausman said. “We’re saying, ‘If the future climate were here now, what would need to happen to the grid to adapt to that warmer world?'”

One of the problems with posting at the leading edge of technological change is the topics get posted before any replication or usually no third party expert review. Today’s topic hasn’t seen any oversight other than the peer review for publication.

The issues taken as foregone conclusions hinges on climate change. With billions of dollars in the business now and jobs on the line there is little chance that real science will reassert some discipline. Only a few days ago more misrepresentation was found and narrowly reported.

But there is good reason to think that the grid will need to increase capacity even as conservation and efficiency reduce demand. There will be more folks using more power and that alone justifies the Michigan team’s math for replication.

There are lots of more valid issues to factor in than climate change. Some may well have far more impact than climate change. Imagine 100 million cars with 250 mile ranges charging up. Can you imagine draining them in the middle of the afternoon before heading home from work? Just saying. Might want to think these things through with some common sense a well as serious real science.

Massachusetts Institute of Technology (MIT) researchers’ new study unravels the properties of a promising new material for all solid state lithium ion batteries, which could be safer and longer-lasting than traditional batteries. The team at MIT probed the mechanical properties of a sulfide-based solid electrolyte material to determine its mechanical performance when incorporated into batteries.

Using specialized equipment, the MIT team did tests in which they used a pyramidal-tipped probe to indent the surface of a piece of the sulfide-based material. Surrounding the resulting indentation (seen at center), cracks were seen forming in the material (indicated by arrows), revealing details of its mechanical properties. Image Credit: MIT. Click image for the largest view.

The new findings has been published in the journal Advanced Energy Materials.

Most batteries are composed of two solid, electrochemically active layers called electrodes, separated by a polymer membrane infused with a liquid or gel electrolyte. But recent research has explored the possibility of all solid state batteries, in which the liquid (and potentially flammable) electrolyte would be replaced by a solid electrolyte, which could enhance the batteries’ energy density and safety.

Lithium-ion batteries have provided a lightweight energy-storage solution that has enabled many of today’s high-tech devices, from smart phones to electric cars. But substituting the conventional liquid electrolyte with a solid electrolyte in such batteries could have significant advantages. Such all-solid-state lithium-ion batteries could provide even greater energy storage ability, pound for pound, at the battery pack level. They may also virtually eliminate the risk of tiny, fingerlike metallic projections called dendrites that can grow through the electrolyte layer and lead to short-circuits.

Krystyn Van Vliet, the Michael (1949) and Sonja Koerner Professor of Materials Science and Engineering said, “Batteries with components that are all solid are attractive options for performance and safety, but several challenges remain. In the lithium-ion batteries that dominate the market today, lithium ions pass through a liquid electrolyte to get from one electrode to the other while the battery is being charged, and then flow through in the opposite direction as it is being used. These batteries are very efficient, but “the liquid electrolytes tend to be chemically unstable, and can even be flammable. So if the electrolyte was solid, it could be safer, as well as smaller and lighter.”

But the big question regarding the use of such all-solid batteries is what kinds of mechanical stresses might occur within the electrolyte material as the electrodes charge and discharge repeatedly. This cycling causes the electrodes to swell and contract as the lithium ions pass in and out of their crystal structure. In a stiff electrolyte, those dimensional changes can lead to high stresses. If the electrolyte is also brittle, that constant changing of dimensions can lead to cracks that rapidly degrade battery performance, and could even provide channels for damaging dendrites to form, as they do in liquid-electrolyte batteries. But if the material is resistant to fracture, those stresses could be accommodated without rapid cracking.

Until now, though, the sulfide’s extreme sensitivity to normal lab air has posed a challenge to measuring mechanical properties including its fracture toughness. To circumvent this problem, members of the research team conducted the mechanical testing in a bath of mineral oil, protecting the sample from any chemical interactions with air or moisture. Using that technique, they were able to obtain detailed measurements of the mechanical properties of the lithium-conducting sulfide, which is considered a promising candidate for electrolytes in all-solid-state batteries.

MIT graduate student Frank McGrogan said, “There are a lot of different candidates for solid electrolytes out there.” Other groups have studied the mechanical properties of lithium-ion conducting oxides, but there had been little work so far on sulfides, even though those are especially promising because of their ability to conduct lithium ions easily and quickly.

Previous researchers used acoustic measurement techniques, passing sound waves through the material to probe its mechanical behavior, but that method does not quantify the resistance to fracture. But the new study, which used a fine-tipped probe to poke into the material and monitor its responses, gives a more complete picture of the important properties, including hardness, fracture toughness, and Young’s modulus (a measure of a material’s capacity to stretch reversibly under an applied stress).

Van Vliet explained, “Research groups have measured the elastic properties of the sulfide-based solid electrolytes, but not fracture properties.” The latter are crucial for predicting whether the material might crack or shatter when used in a battery application.

The researchers found that the material has a combination of properties somewhat similar to silly putty or salt water taffy: When subjected to stress, it can deform easily, but at sufficiently high stress it can crack like a brittle piece of glass.

By knowing those properties in detail, “you can calculate how much stress the material can tolerate before it fractures,” and design battery systems with that information in mind, Van Vliet said.

The material turned out to be more brittle than would be ideal for battery use, but as long as its properties are known and systems designed accordingly, it could still have potential for such uses, McGrogan said. “You have to design around that knowledge,” he added.

Working along with McGrogan and Van Vliet were Tushar Swamy, a MIT graduate student; Yet-Ming Chiang, a professor of materials science and engineering; and four others including an undergraduate participant in the National Science Foundation Research Experience for Undergraduate (REU) program administered by MIT’s Center for Materials Science and Engineering and its Materials Processing Center.

New electrolytes two days in a row. Battery tech is on a roll for now. Like yesterday’s topic this research is still gestating. But there is a good likely hood that solid state electrolytes will find some market sooner than we might expect.


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