Massachusetts Institute of Technology engineers have designed a battery made from inexpensive, abundant materials, that could provide low-cost backup storage for renewable energy sources. Less expensive than lithium-ion battery technology, the new architecture uses aluminum and sulfur as its two electrode materials with a molten salt electrolyte in between.

The new battery architecture is described in the journal Nature, in a paper by MIT Professor Donald Sadoway, along with 15 others at MIT and in China, Canada, Kentucky, and Tennessee.

Wind and solar advocates are building out ever larger installations of wind and solar power systems, thus need is growing fast for economical, large-scale backup systems to provide power when the sun is down and the air is calm. Today’s lithium-ion batteries are still too expensive for most such applications, and other options such as pumped hydro require specific landscapes that are not always available.

The MIT led group’s chemistry architecture could help to fill the intermittency gaps.

Sadoway, who is the John F. Elliott Professor Emeritus of Materials Chemistry said, “I wanted to invent something that was better, much better, than lithium-ion batteries for small-scale stationary storage, and ultimately for automotive [uses].”

In addition to being expensive, lithium-ion batteries contain a flammable electrolyte, making them less than ideal for transportation. So, Sadoway started studying the periodic table, looking for cheap, Earth-abundant metals that might be able to substitute for lithium. The commercially dominant metal, iron, doesn’t have the right electrochemical properties for an efficient battery, he said. But the second-most-abundant metal in the marketplace – and actually the most abundant metal on Earth – is aluminum.

“So, I said, well, let’s just make that a bookend. It’s gonna be aluminum,” he commented.

Next up was deciding what to pair the aluminum with for the other electrode, and what kind of electrolyte to put in between to carry ions back and forth during charging and discharging. The cheapest of all the non-metals is sulfur, so that became the second electrode material.

As for the electrolyte, “we were not going to use the volatile, flammable organic liquids” that have sometimes led to dangerous fires in cars and other applications of lithium-ion batteries, Sadoway said. They tried some polymers but ended up looking at a variety of molten salts that have relatively low melting points – close to the boiling point of water, as opposed to nearly 1,000° Fahrenheit for many salts. “Once you get down to near body temperature, it becomes practical” to make batteries that don’t require special insulation and anticorrosion measures, he noted.

The three ingredients they ended up with are cheap and readily available – aluminum, no different from the foil at the supermarket; sulfur, which is often a waste product from processes such as petroleum refining; and widely available salts. “The ingredients are cheap, and the thing is safe – it cannot burn,” Sadoway said.

In their experiments, the team showed that the battery cells could endure hundreds of cycles at exceptionally high charging rates, with a projected cost per cell of about one-sixth that of comparable lithium-ion cells. They showed that the charging rate was highly dependent on the working temperature, with 110° Celsius (230° Fahrenheit) showing 25 times faster rates than 25° C (77° F).

Surprisingly, the molten salt the team chose as an electrolyte simply because of its low melting point turned out to have a fortuitous advantage. One of the biggest problems in battery reliability is the formation of dendrites, which are narrow spikes of metal that build up on one electrode and eventually grow across to contact the other electrode, causing a short-circuit and hampering efficiency. But this particular salt, it happens, is very good at preventing that malfunction.

The chloro-aluminate salt they chose “essentially retired these runaway dendrites, while also allowing for very rapid charging,” Sadoway said. “We did experiments at very high charging rates, charging in less than a minute, and we never lost cells due to dendrite shorting.”

“It’s funny,” he said, because the whole focus was on finding a salt with the lowest melting point, but the catenated chloro-aluminates they ended up with turned out to be resistant to the shorting problem. “If we had started off with trying to prevent dendritic shorting, I’m not sure I would’ve known how to pursue that,” Sadoway said. “I guess it was serendipity for us.”

Additionally, the battery requires no external heat source to maintain its operating temperature. The heat is naturally produced electrochemically by the charging and discharging of the battery. “As you charge, you generate heat, and that keeps the salt from freezing. And then, when you discharge, it also generates heat,” Sadoway said.

In a typical installation used for load-leveling at a solar generation facility, for example, “you’d store electricity when the sun is shining, and then you’d draw electricity after dark, and you’d do this every day. And that charge-idle-discharge-idle is enough to generate enough heat to keep the thing at temperature.”

This new battery formulation, he says, would be ideal for installations of about the size needed to power a single home or small to medium business, producing on the order of a few tens of kilowatt-hours of storage capacity.

For larger installations, up to utility scale of tens to hundreds of megawatt hours, other technologies might be more effective, including the liquid metal batteries Sadoway and his students developed several years ago and which formed the basis for a spinoff company called Ambri, which hopes to deliver its first products within the next year. For that invention, Sadoway was recently awarded this year’s European Inventor Award.

The smaller scale of the aluminum-sulfur batteries would also make them practical for uses such as electric vehicle charging stations, Sadoway noted. He points out that when electric vehicles become common enough on the roads that several cars want to charge up at once, as happens today with gasoline fuel pumps, “if you try to do that with batteries and you want rapid charging, the amperages are just so high that we don’t have that amount of amperage in the line that feeds the facility.” So having a battery system such as this to store power and then release it quickly when needed could eliminate the need for installing expensive new power lines to serve those chargers.

The new technology is already the basis for a new spinoff company called Avanti, which has licensed the patents to the system, co-founded by Sadoway and Luis Ortiz ’96 ScD ’00, who was also a co-founder of Ambri. “The first order of business for the company is to demonstrate that it works at scale,” Sadoway said, and then subject it to a series of stress tests, including running through hundreds of charging cycles.

Would a battery based on sulfur run the risk of producing the foul odors associated with some forms of sulfur? Not a chance, Sadoway said. “The rotten-egg smell is in the gas, hydrogen sulfide. This is elemental sulfur, and it’s going to be enclosed inside the cells.” If you were to try to open up a lithium-ion cell in your kitchen, he says (and please don’t try this at home!), “the moisture in the air would react and you’d start generating all sorts of foul gases as well. These are legitimate questions, but the battery is sealed, it’s not an open vessel. So I wouldn’t be concerned about that.”

The research team included members from Peking University, Yunnan University and the Wuhan University of Technology, in China; the University of Louisville, in Kentucky; the University of Waterloo, in Canada; Oak Ridge National Laboratory, in Tennessee; and MIT. The work was supported by the MIT Energy Initiative, the MIT Deshpande Center for Technological Innovation, and ENN Group.

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This sounds pretty good! But no mention of how many watt hours by battery volume or weight. Then there are those “going to scale” things that come up when leaving the lab and getting to a factory setup.

One does hope there will be continued refinement. The press release makes it sound as if the whole thing just fell together by virtue of making low cost choices. One can be certain a lot of thought went into those decisions.

What we do know that gives some pause is this technology needs to be used to stay warm enough to work well. There has to be an energy price in this and that was not revealed or discussed. One might want to be sure these are real cheap as continuous duty with only cycles in the “hundreds” might not actually cut the economic starting ribbon.

University of Technology Sydney (UTS) and Queensland University of Technology (QUT) researchers have announced a new design for solid-state hydrogen storage that could significantly reduce charging times.

Hydrogen is gaining significant attention as an efficient way to store ‘green energy’ from renewables such as wind and solar. Compressed gas is the most common form of hydrogen storage, however it can also be stored in a liquid or solid state.

Dr Saidul Islam, from the University of Technology Sydney, explained solid hydrogen storage, and in particular metal hydride, is attracting interest because it is safer, more compact, and lower cost than compressed gas or liquid, and it can reversibly absorb and release hydrogen.

Dr Islam commented, “Metal hydride hydrogen storage technology is ideal for onsite hydrogen production from renewable electrolysis. It can store the hydrogen for extended periods and once needed, it can be converted as gas or a form of thermal or electric energy when converted through a fuel cell.”

“Applications include hydrogen compressors, rechargeable batteries, heat pumps and heat storage, isotope separation and hydrogen purification. It can also be used to store hydrogen in space, to be used in satellites and other ‘green’ space technology,” he added.

However, a problem with metal hydride for hydrogen energy storage has been its low thermal conductivity, which leads to slow charging and discharging times.

To address this the researchers developed a new method to improve solid-state hydrogen charging and discharging times. The study: “Design optimization of a magnesium-based metal hydride hydrogen energy storage system,” was recently published in the journal Scientific Reports.

Comparison of hydrogen absorption concentration with different designs. Image Credit: Puchanee Larpruenrudee, School of Mechanical and Mechatronic Engineering, University of Technology Sydney. Click the press release link above for a larger image.

First author Puchanee Larpruenrudee, a PhD candidate in the UTS School of Mechanical and Mechatronic Engineering, said faster heat removal from the solid fuel cell results in faster charging times.

Larpruenrudee explained, “Several internal heat exchangers have been designed for use with metal hydride hydrogen storage. These include straight tubes, helical coil or spiral tubes, U-shape tubes, and fins. Using a helical coil significantly improves heat and mass transfer inside the storage.”

“This is due to the secondary circulation and having more surface area for heat removal from the metal hydride powder to the cooling fluid. Our study further developed a helical coil to increase heat transfer performance,” he concluded.

The researchers developed a semi-cylindrical coil as an internal heat exchanger, which significantly improved heat transfer performance. The hydrogen charging time was reduced by 59% when using the new semi-cylindrical coil compared to a traditional helical coil heat exchanger.

The team is now working on the numerical simulation of the hydrogen desorption process, and continuing to improve absorption times. The semi-cylindrical coil heat exchanger will be further developed for this purpose.

As a goal, the researchers aim to develop a new design for hydrogen energy storage, which will combine other types of heat exchangers. They hope to also work with industry partners to investigate real tank performance based on the new heat exchanger.

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Low pressure metal hydride hydrogen storage has potential. Some of the most difficult problems are reduced to more manageable levels. Yet hydrogen is still the smallest atom and is a devil to contain, and likes to get involved with whatever materials are used in its containment, which is why the metal hydride idea works.

No idea offered for storing hydrogen offers a leak proof long term (days or weeks) solution and hydrogen’s properties are just more than a bit scary if allowed to escape into much of a confined space.

Metal hydride might get to safe practicality someday.

Meanwhile, hundreds of millions of years ago nature figured out what to do. Combine that hydrogen with a bit of carbon and presto, food and fuel and a whole lot of life gets going!

Gwangju Institute of Science and Technology (GIST) scientists use a water treatment for morphology control in the fabrication of active layer thin films, improving the performance and stability of large-area organic solar cells.

Morphology control is essentially about making and placing very small particles in their working position. Albeit somewhat a simplified description, as miniaturization becomes micro miniaturization and now molecule, crystal and sometimes even atom placement, the process engineering efforts are getting very challenging indeed. The efforts have been ongoing for decades. These are basic problems that sometimes simply stop great ideas from getting to market.

Until now a lack of morphology control of the active layer made it challenging to develop organic solar cells (OSCs) with large active areas.

OSCs, which use organic polymers to convert sunlight into electricity, have received considerable attention in recent times for their desirable properties as next-generation energy sources. These include lightweight, flexibility, scalability, and a high power conversion efficiency (>19%). Currently, several strategies exist for enhancing the performance and stability of OSCs. However, a problem that lingers on is the difficulty of controlling the morphology of the active layer in OSCs when scaling up to large areas. This makes it challenging to obtain high-quality active layer thin films and, in turn, fine-tune the device efficiency.

Controlling the morphology of the active layer thin film during upscaling has proved challenging. GIST researchers solve this problem with deionized water as a method for morphology control, enabling high efficiency OSC modules with large active areas. Image Credit: Dong-Yu Kim, Gwangju Institute of Science and Technology. Click the study paper link below for more information.

In a recent study, a team of researchers from the Gwangju Institute of Science and Technology, Korea set out to address this issue. In their work, published in Advanced Functional Materials, they suggested a solution that appears rather counterintuitive at first glance: using water treatment to control the active layer morphology.

Professor Dong-Yu Kim, who headed the study explained, “Water is known to hinder the performance of organic electronic devices, since it remains in the ‘trap states’ of the organic material, blocking the charge flow and degrading the device performance. However, we figured that using water rather than an organic solvent-based active solution as a medium of treatment method would enable necessary physical changes without causing chemical reactions.”

The researchers chose the polymers PTB7-Th and PM6 as donor materials and PC61BM and EH-IDTBR and Y6 as acceptor materials for the active layer.

They noticed that inducing a vortex to mix the donor and acceptor materials in the active solution could lead to a well-mixed active solution, yet it was not enough on its own. The active solution was hydrophobic and, accordingly, the researchers decided to use deionized (DI) water and vortices to stir the solution.

They let the donor and acceptor materials sit in chlorobenzene (host active solution) overnight, and then added DI water in the solution and stirred it, creating tiny vortices.

Due to the hydrophobic nature of the solution, the water pushed on the donor and acceptor molecules, causing them to dissolve more finely into the solution. They then let the solution rest, which caused the water to separate from the solution.

This water was then removed and the water-treated active solution was used to prepare thin films of PTB7-Th: PC61BM (F, fullerene), PTB7-Th: EH-IDTBR (NF, fullerene), and PM6: Y6 (H-NF, high-efficiency non-fullerene).

The researchers then examined the photovoltaic performance of these thin films in a slot-die-coated inverted OSC configuration and compared them with those for OSCs without water treatment.

Prof Kim noted, “We observed that the water-treated active solution led to a more uniform active layer thin films, which showed higher power conversion efficiencies compared to those not treated with water. Moreover, we fabricated large-area OSC modules with an active area of 10 cm2, which showed a conversion efficiency as high as 11.92% for water-treated H-NF films.”

Overall, this study provides a guideline for developing large-scale, efficient OSCs using a remarkably easy, economical, and eco-friendly method, which can open doors to their realization and commercialization.

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In case you were wondering where the large organic solar cells were, this post shows what has been and what might be coming. This process has produced OSCs to better than ½ of the efficiency potential and they wouldn’t cost a small fortune.

This post is an opportunity to show those who wonder “what happened to that great idea?” that comes up for a lot of what we see on these pages. This work from Korea is quite newsworthy, welcome and shows great innovation in a perplexing problem.

Everyone keep in mind there are thousands more perplexing problems out there. One could say engineering is making things with the systems and tooling that exist to get certain functions underway. Things to come to a stop if the systems simply haven’t been discovered yet.

DGIST (Daegu Gyeongbuk Institute of Science and Technology in Korea) researchers developed a piezoelectric polymer/ceramic composite fiber with a cross-sectional form that is uniformly controlled to allow the use of energy harvesting technologies that can recycle energy wasted or consumed in everyday life.

The results of this study have been published in Nano Energy.

Piezoelectric fiber can produce electrical energy through the piezoelectric effect of the material and drive wearable electronic devices through the movement of the wearer. However, most of the piezoelectric fibers developed so far are made of nanofibers, meaning that it is difficult to control the shape of the fibers, and that the fibers are weak, thus hindering its commercialization. In addition, there are very few studies on the relationship between the shape of the fiber material and the piezoelectric performance.

A research team led by Lim Sang-kyoo, senior researcher of Division of Energy Technology, produced PVDF (Polyvinylidene fluoride) fiber that contains barium titanate in a nano stick form by taking the shape of flowers and stems (daffodils, radish blossoms, papyrus stems, and sedge stems) using melt spinning technology and controlling their cross-sectional shapes uniformly.

A schematic diagram of the method for determining the relationship between the morphology and piezoelectric performance of fiber components. Image Credit: Daegu Gyeongbuk Institute of Science and Technology. For larger image views click either the study paper or press release links above.

The team confirmed that it improved the piezoelectric performance by increasing the surface area of the fiber while simultaneously increasing the crystallinity of the fiber, which is advantageous for generating electricity.

The team also confirmed the correlation between the specific surface area and the piezoelectric effect according to the shape of the fiber using a high-speed camera. The piezoceramic PVDF composite fiber generates an electrical signal according to the deformation by an external force.

PVDF fibers containing barium titanate nanostructures in different shapes (spherical and stick shapes) were produced to investigate the difference in piezoelectric performance depending on the shape of piezoelectric ceramics.

The team confirmed that it maximizes the dielectric polarization and contributes to the improvement of the piezoelectric performance favorable to the arrangement.

Senior Researcher Lim Sang-kyoo said, “It is expected that high-performance fiber-type energy harvesting materials with enhanced fiber strength can be commercialized through this research in the future.”

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When it comes to low power needs in remote areas or in mobility and other applications piezoelectric could be quite the saver in the costs to generate a little remote power. With a little low cost, long lived storage a lot of opportunities could result across the planet for all income levels.

This isn’t super interesting or exotic, but the units marketed could reach into the billons. That’s pretty interesting.

The University of Illinois Chicago researchers new system uses electrolysis to transform captured carbon dioxide gas into high purity ethylene, with other carbon-based fuels and oxygen as byproducts.

Their reporting paper has been published in Cell Reports Physical Science.

The discovery offers a way to convert 100% of carbon dioxide captured from industrial exhaust into ethylene, a key building block for plastics, and major product made from ethylene.

While researchers have been exploring the possibility of converting carbon dioxide to ethylene for more than a decade, the UIC team’s approach is the first to achieve nearly 100% utilization of carbon dioxide to produce hydrocarbons

Schematic diagram of the custom 3D-printed electrochemical cell for CO2RR experiments. Image Credit: University of Illinois Chicago. Click either links above for the study (no paywall at post time) or press release for more images and information.

The process can convert up to 6 metric tons of carbon dioxide into 1 metric ton of ethylene, recycling almost all carbon dioxide captured. Because the system runs on electricity, the use of renewable energy can make the process carbon negative.

According to Singh, his team’s approach surpasses the net-zero carbon goal of other carbon capture and conversion technologies by actually reducing the total carbon dioxide output from industry. “It’s a net negative,” he said. “For every 1 ton of ethylene produced, you’re taking 6 tons of CO2 from point sources that otherwise would be released to the atmosphere.”

Previous attempts at converting carbon dioxide into ethylene have relied on reactors that produce ethylene within the source carbon dioxide emission stream. In these cases, as little as 10% of CO2 emissions typically converts to ethylene. The ethylene must later be separated from the carbon dioxide in an energy-intensive process often involving fossil fuel energy.

In UIC’s approach, an electric current is passed through a cell, half of which is filled with captured carbon dioxide, the other half with a water-based solution. An electrified catalyst draws charged hydrogen atoms from the water molecules into the other half of the unit separated by a membrane, where they combine with charged carbon atoms from the carbon dioxide molecules to form ethylene.

Among manufactured chemicals worldwide, ethylene ranks third for carbon emissions after ammonia and cement. Ethylene is used not only to create plastic products for the packaging, agricultural and automotive industries, but also to produce chemicals used in antifreeze, medical sterilizers and vinyl siding for houses.

Ethylene is usually made in a process called steam cracking that requires enormous amounts of heat. Cracking generates about 1.5 metric tons of carbon emissions per ton of ethylene created. On average, manufacturers produce around 160 million tons of ethylene each year, which results in more than 260 million tons of carbon dioxide emissions worldwide.

In addition to ethylene, the UIC scientists were able to produce other carbon-rich products useful to industry with their electrolysis approach. They also achieved a very high solar energy conversion efficiency, converting 10% of energy from the solar panels directly to carbon product output. This is well above the state-of-the-art standard of 2%. For all the ethylene they produced, the solar energy conversion efficiency was around 4%, approximately the same rate as photosynthesis.

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This is the kind of news that has to snap the attention of independent petroleum producers and the coal industry. As the process matures we might see a gradual shift from the fossil fuel sources to a form of a current CO2 recycling norm. The press release is driven in part by the CO2 effluent that ranks #3 from ethylene production. There is much more available CO2 from the ammonia, cement, power generation and other large concentrated CO2 sources.

While the 4% efficiency rank isn’t going to light everyone up, note that 4% is about where nature is satisfied after hundreds of millions of years with great results. The notation of 10% from solar panels is impressive and suggests further improvements might come over time.

Plastics are an obvious target as the energy input is concentrated and large. But there are other opportunities, and this new technology just begs for much more and broader attention and effort.

Lots of question remain. Is the oxygen from the water that’s lost its hydrogen just vented? Then how does this compare to water electrolysis as the freed hydrogen is already locked up in a carbon based gas?

If other products are likely forthcoming a selection of light petroleum gasses like methane, propane and butane are possible too? Then is there a probability that liquid alcohols could also be forthcoming? Should this technology gain development and market traction will the optimum product trigger fuel cell development for it too?

Yup. Big News Indeed! Congratulations to the team at UIC!


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