Storage devices, like this one-megawatt battery at the National Wind Technology Center, can reduce variable generation curtailments. Photo by Dennis Schroeder / NREL 47219
Increasing the penetration of variable energy sources such as solar and wind energy in the grid—without introducing heavy curtailment—does not require costly, very-long-duration storage, says a new study by National Renewable Energy Laboratory researchers Paul Denholm and Trieu Mai.
Historically, energy storage has been considered too pricey an option for integrating wind and solar into the grid, and utilities have relied on less expensive options. However, declining costs indicate that energy storage solutions may play a greater role in providing grid flexibility and storing because of their ability to decrease the amounts of curtained wind and solar generation.
When wind and solar are curtailed, grid operators cannot use all of the available renewable resources (i.e., there is more wind blowing than the grid can utilize). Often, this means that the grid must rely on a fossil-fuel energy generation source, rather than a cleaner source of energy. But with storage solutions, operators can save some of that excess energy, and thereby incorporate more renewable energy into the grid.
“Interest in very-high-renewable systems warrants further exploration into storage’s role in the future grid,” says Mai.
The team’s study, “Timescales of Energy Storage Needed for Reducing Renewable Energy CurtailmentPDF,” examines the amount and configuration of energy storage required to decrease variable-generation curtailments under high-renewable scenarios. Researchers developed a case study based on the U.S. Department of Energy’s Wind Vision report, in which variable generation provides 55% of the electricity demand in the Electricity Reliability Council of Texas (ERCOT) grid system in 2050. Analysis results showed that the amount of avoided curtailment falls off rapidly with storage durations longer than 8 hours, with the first 4 hours providing the largest benefit.
Denholm and Mai developed several energy mix scenarios based on the isolated ERCOT grid system, and found that deploying wind and solar together produced much lower levels of curtailment than when deployed individually.
“Wind and photovoltaics play well together,” Denholm says. However, the mix that produces the least amount of curtailment uses about twice as much wind as solar.
Among all energy mixes analyzed, there was little incremental benefit to deploying costly, very-long-duration or seasonal storage—at penetrations of up to 55%, the greatest benefit is found with the first 4 hours of storage.
Abstract: In article number 1703909, Gang Chen, Guihua Yu, and co-workers present a novel concept of 2D nanofluidic lithium-ion transport channels based on stacked Co3O4nanosheets for high-performance lithium batteries. This unique nanoarchitecture exhibits exceptional capacity and outstanding long-term cycling stability for lithium-ion storage at high-rates in both half- and full-cells.
Despite being a promising electrode material, bulk cobalt oxide (Co3O4) exhibits poor lithium ion storage properties. Nanostructuring, e.g. making Co3O4 into ultrathin nanosheets, shows improved performance, however, Co3O4-based nanomaterials still lack long-term stability and high rate capability due to sluggish ion transport and structure degradation.
Nanofluidic channels possess desired properties to address above issues. However, while these unique structures have been studied in hollow nanotubes and recently in restacked layered materials such as graphene, it remains challenging to construct nanofluidic channels in intrinsically non-layered materials.
Motived by the large number of non-layered materials, e.g. transition metal oxides, which hold great promise in battery applications, scientists aim to extend the concept of nanofluidic channels into these materials and improve their electrochemical properties.
Nanofluidic channels feature a unique unipolar ionic transport when properly designed and constructed. By controlling surface charge and channel spacing, enhanced and selective ion transport can be achieved in these channels by constructing them with dimensions comparable to the double Debye length and opposite surface charge with respect to the transporting ion.
“Such constructed 2D nanofluidic channels in non-layered materials manifest a general structural engineering strategy for improving electrochemical properties in a vast number of different electrode materials,” Guihua Yu, a professor in Materials Science and Engineering, Mechanical Engineering, at the Texas Materials Institute, University of Texas at Austin. “The enhanced and selective ion transport demonstrated in our study is of broad interest to many applications where fast kinetics of ion transport is essential.”
Illustration of lithium ion transport in 2D nanofluidic channels. (Reprinted with permission by Wiley-VCH)
On the one hand, an intercalated molecule acts as interlayer pillar in the stacked oxide, constituting transport channels with proper spacing. On the other hand, negatively charged functional groups anchored on the nanosheets surface facilitate transport of positively charged lithium ions inside the channels.
“Satisfying aforementioned conditions for unipolar ionic transport, combined with other advantageous features – extra storage capacity contributed by the surface functional groups, buffered structural stress from the interlayer spacing, and shortened lithium ion diffusion distance due to the ultrathin nanosheet morphology – the resulting nanoarchitecture exhibit exceptional electrochemical performance as tested in lithium-ion batteries,” notes Yu.
In a next step, the researchers are going to extend the concept of 2D nanofluidic channels to other electrode materials with or without layering structures. With ability to further tune interlayer spacing, they expect some promising energy storage applications in beyond-lithium-ion batteries.
It might also be interesting to examine this structural engineering strategy in other applications, for example, catalysis.
Design and LIBs application of Co3O4 nanosheets with 2D nanofluidic channels. (a) The synthetic route from Co-based layered hydroxide precursor to Co3O4 nanosheets with 2D nanofluidic channels. (b) Cycling performance of a full cell (anode: Co3O4 nanosheets /cathode: commercial LiCoO2). (Reprinted with permission by Wiley-VCH)
Constructing 2D nanofluidic channels for energy storage application is still in its infancy and the success of using non-layered materials demonstrated in this study promises a bright future in this direction with a broader material coverage.
“We are also taking this research direction even further by looking into the transport and storage properties for energy storage systems based on larger charge-carrying ions, such as Na+ and Mg2+, ” concludes Yu. “In order to realize that, an important challenge is to tune the channel spacing in a controlled manner. It is also imperative to investigate structural stability and scalability of this specially designed nanoarchitecture for its utilization in practical applications.”
Berkeley Lab leads discovery of the fastest magnesium-ion solid-state conductor to date.
A team of Department of Energy (DOE) scientists at the Joint Center for Energy Storage Research (JCESR) has discovered the fastest magnesium-ion solid-state conductor, a major step towards making solid-state magnesium-ion batteries that are both energy dense and safe.
Argonne scientist Baris Key, shown on left at work in his nuclear magnetic resonance lab, worked with researchers at Berkeley Lab on the discovery of the fastest ever magnesium-ion solid-state conductor. (Credit: Argonne National Laboratory)
The electrolyte, which carries charge back and forth between the battery’s cathode and anode, is a liquid in all commercial batteries, which makes them potentially flammable, especially in lithium-ion batteries. A solid-state conductor, which has the potential to become an electrolyte, would be far more fire-resistant.
Researchers at DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Argonne National Laboratory were working on a magnesium battery, which offers higher energy density than lithium, but were stymied by the dearth of good options for a liquid electrolyte, most of which tend to be corrosive against other parts of the battery. “Magnesium is such a new technology, it doesn’t have any good liquid electrolytes,” said Gerbrand Ceder, a Berkeley Lab Senior Faculty Scientist. “We thought, why not leapfrog and make a solid-state electrolyte?”
The material they came up with, magnesium scandium selenide spinel, has magnesium mobility comparable to solid-state electrolytes for lithium batteries. Their findings were reported in Nature Communications in a paper titled, “High magnesium mobility in ternary spinel chalcogenides.”JCESR, a DOE Innovation Hub, sponsored the study, and the lead authors are Pieremanuele Canepa and Shou-Hang Bo, postdoctoral fellows at Berkeley Lab.
“With the help of a concerted effort bringing together computational materials science methodologies, synthesis, and a variety of characterization techniques, we have identified a new class of solid conductors that can transport magnesium ions at unprecedented speed,” Canepa said.
Collaboration with MIT and Argonne
The research team also included scientists at MIT, who provided computational resources, and Argonne, who provided key experimental confirmation of the magnesium scandium selenide spinel material to document its structure and function.
Co-author Baris Key, a research chemist at Argonne, conducted nuclear magnetic resonance (NMR) spectroscopy experiments. These tests were among the first steps to experimentally prove that magnesium ions could move through the material as rapidly as the theoretical studies had predicted.
“It was crucial to confirm the fast magnesium hopping experimentally. It is not often that the theory and the experiment agree closely with each other,” Key said. “The solid state NMR experiments for this chemistry were very challenging and would not be possible without dedicated resources and a funding source such as JCESR.
As we’ve shown in this study, an in-depth understanding of short- and long-range structure and ion dynamics will be the key for magnesium ion battery research.”
NMR is akin to magnetic resonance imaging (MRI), which is routinely used in medical settings, where it shows hydrogen atoms of water in human muscles, nerves, fatty tissue, and other biological substances. But researchers can also tune NMR frequency to detect other elements, including the lithium or magnesium ions that are found in battery materials.
The NMR data from the magnesium scandium selenide material, however, involved material of unknown structure with complex properties, making them challenging to interpret.
Canepa noted the challenges of testing materials that are so new. “Protocols are basically non-existent,” he said. “These findings were only possible by combining a multi-technique approach (solid-state NMR and synchrotron measurements at Argonne) in addition to conventional electrochemical characterization.”
Doing the impossible
The team plans to do further work to use the conductor in a battery. “This probably has a long way to go before you can make a battery out of it, but it’s the first demonstration you can make solid-state materials with really good magnesium mobility through it,” Ceder said. “Magnesium is thought to move slowly in most solids, so nobody thought this would be possible.”
Bo, now an assistant professor at Shanghai Jiao Tong University, said the discovery could have a dramatic effect on the energy landscape. “This work brought together a great team of scientists from various scientific disciplines, and took the first stab at the formidable challenge of building a solid-state magnesium battery,” he said. “Although currently in its infancy, this emerging technology may have a transformative impact on energy storage in the near future.”
Gopalakrishnan Sai Gautam, another co-author who was an affiliate at Berkeley Lab and is now at Princeton, said the team approach made possible by a DOE hub such as JCESR was critical. “The work shows the importance of using a variety of theoretical and experimental techniques in a highly collaborative environment to make important fundamental discoveries,” he said.
Ceder was excited at the prospects for the finding but cautioned that work remains to be done. “There are enormous efforts in industry to make a solid-state battery. It’s the holy grail because you would have the ultimate safe battery. But we still have work to do. This material shows a small amount of electron leakage, which has to be removed before it can be used in a battery.”
Funding for the project was provided by the DOE Office of Science through the Joint Center for Energy Storage Research, a Department of Energy Innovation Hub. The Advanced Photon Source, a DOE Office of Science User Facility at Argonne, added vital data to the study regarding the structure of the solid conductor.
The National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility at Berkeley Lab, provided computing resources. Other co-authors on the paper are Juchaun Li of Berkeley Lab, William Richards and Yan Wang of MIT, and Tan Shi and Yaosen Tian of UC Berkeley.
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Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel Prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state, and municipal agencies to help them solve their specific problems, advance America’s scientific leadership, and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.
DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
The Joint Center for Energy Storage Research (JCESR), a DOE Energy Innovation Hub, is a major partnership that integrates researchers from many disciplines to overcome critical scientific and technical barriers and create new breakthrough energy storage technology. Led by the U.S. Department of Energy’s Argonne National Laboratory, partners include national leaders in science and engineering from academia, the private sector, and national laboratories. Their combined expertise spans the full range of the technology-development pipeline from basic research to prototype development to product engineering to market delivery.
“Air-breathing” battery can store electricity for months, for about a fifth the cost of current technologies.
Wind and solar power are increasingly popular sources for renewable energy. But intermittency issues keep them from connecting widely to the U.S. grid: They require energy-storage systems that, at the cheapest, run about $100 per kilowatt hour and function only in certain locations.
Now MIT researchers have developed an “air-breathing” battery that could store electricity for very long durations for about one-fifth the cost of current technologies, with minimal location restraints and zero emissions. The battery could be used to make sporadic renewable power a more reliable source of electricity for the grid.
For its anode, the rechargeable flow battery uses cheap, abundant sulfur dissolved in water. An aerated liquid salt solution in the cathode continuously takes in and releases oxygen that balances charge as ions shuttle between the electrodes. Oxygen flowing into the cathode causes the anode to discharge electrons to an external circuit. Oxygen flowing out sends electrons back to the anode, recharging the battery.
“This battery literally inhales and exhales air, but it doesn’t exhale carbon dioxide, like humans — it exhales oxygen,” says Yet-Ming Chiang, the Kyocera Professor of Materials Science and Engineering at MIT and co-author of a paper describing the battery.
The research appears today in the journal Joule.
The battery’s total chemical cost — the combined price of the cathode, anode, and electrolyte materials — is about 1/30th the cost of competing batteries, such as lithium-ion batteries. Scaled-up systems could be used to store electricity from wind or solar power, for multiple days to entire seasons, for about $20 to $30 per kilowatt hour.
Co-authors with Chiang on the paper are: first author Zheng Li, who was a postdoc at MIT during the research and is now a professor at Virginia Tech; Fikile R. Brushett, the Raymond A. and Helen E. St. Laurent Career Development Professor of Chemical Engineering; research scientist Liang Su; graduate students Menghsuan Pan and Kai Xiang; and undergraduate students Andres Badel, Joseph M. Valle, and Stephanie L. Eiler.
Finding the right balance
Development of the battery began in 2012, when Chiang joined the Department of Energy’s Joint Center for Energy Storage Research, a five-year project that brought together about 180 researchers to collaborate on energy-saving technologies. Chiang, for his part, focused on developing an efficient battery that could reduce the cost of grid-scale energy storage.
A major issue with batteries over the past several decades, Chiang says, has been a focus on synthesizing materials that offer greater energy density but are very expensive. The most widely used materials in lithium-ion batteries for cellphones, for instance, have a cost of about $100 for each kilowatt hour of energy stored.
“This meant maybe we weren’t focusing on the right thing, with an ever-increasing chemical cost in pursuit of high energy-density,” Chiang says. He brought the issue to other MIT researchers. “We said, ‘If we want energy storage at the terawatt scale, we have to use truly abundant materials.’”
The researchers first decided the anode needed to be sulfur, a widely available byproduct of natural gas and petroleum refining that’s very energy dense, having the lowest cost per stored charge next to water and air. The challenge then was finding an inexpensive liquid cathode material that remained stable while producing a meaningful charge.
That seemed improbable — until a serendipitous discovery in the lab.
On a short list of candidates was a compound called potassium permanganate. If used as a cathode material, that compound is “reduced” — a reaction that draws ions from the anode to the cathode, discharging electricity. However, the reduction of the permanganate is normally impossible to reverse, meaning the battery wouldn’t be rechargeable.
Still, Li tried. As expected, the reversal failed. However, the battery was, in fact, recharging, due to an unexpected oxygen reaction in the cathode, which was running entirely on air. “I said, ‘Wait, you figured out a rechargeable chemistry using sulfur that does not require a cathode compound?’ That was the ah-ha moment,” Chiang says.
Using that concept, the team of researchers created a type of flow battery, where electrolytes are continuously pumped through electrodes and travel through a reaction cell to create charge or discharge.
The battery consists of a liquid anode (anolyte) of polysulfide that contains lithium or sodium ions, and a liquid cathode (catholyte) that consists of an oxygenated dissolved salt, separated by a membrane.
Upon discharging, the anolyte releases electrons into an external circuit and the lithium or sodium ions travel to the cathode.
At the same time, to maintain electroneutrality, the catholyte draws in oxygen, creating negatively charged hydroxide ions. When charging, the process is simply reversed. Oxygen is expelled from the catholyte, increasing hydrogen ions, which donate electrons back to the anolyte through the external circuit.
“What this does is create a charge balance by taking oxygen in and out of the system,” Chiang says.
Because the battery uses ultra-low-cost materials, its chemical cost is one of the lowest — if not the lowest — of any rechargeable battery to enable cost-effective long-duration discharge. Its energy density is slightly lower than today’s lithium-ion batteries.
“It’s a creative and interesting new concept that could potentially be an ultra-low-cost solution for grid storage,” says Venkat Viswanathan, an assistant professor of mechanical engineering at Carnegie Mellon University who studies energy-storage systems.
Lithium-sulfur and lithium-air batteries — where sulfur or oxygen are used in the cathode — exist today. But the key innovation of the MIT research, Viswanathan says, is combining the two concepts to create a lower-cost battery with comparable efficiency and energy density. The design could inspire new work in the field, he adds: “It’s something that immediately captures your imagination.”
Making renewables more reliable
The prototype is currently about the size of a coffee cup. But flow batteries are highly scalable, Chiang says, and cells can be combined into larger systems.
As the battery can discharge over months, the best use may be for storing electricity from notoriously unpredictable wind and solar power sources. “The intermittency for solar is daily, but for wind it’s longer-scale intermittency and not so predictable.
When it’s not so predictable you need more reserve — the capability to discharge a battery over a longer period of time — because you don’t know when the wind is going to come back next,” Chiang says. Seasonal storage is important too, he adds, especially with increasing distance north of the equator, where the amount of sunlight varies more widely from summer to winter.
Chiang says this could be the first technology to compete, in cost and energy density, with pumped hydroelectric storage systems, which provide most of the energy storage for renewables around the world but are very restricted by location.
“The energy density of a flow battery like this is more than 500 times higher than pumped hydroelectric storage. It’s also so much more compact, so that you can imagine putting it anywhere you have renewable generation,” Chiang says.
The research was supported by the Department of Energy.
Now the company is announcing a “breakthrough” in solid-state batteries to power their next-generation electric cars and they are filing for patents to protect their IP.
Get ready for some crazy claims here.
Solid-state batteries are thought to be a lot safer than common li-ion cells and could have more potential for higher energy density, but they also have limitations, like temperature ranges, electrode current density, and we have yet to see a company capable of producing it in large-scale and at an attractive price point competitive with li-ion.
Now Fisker announced that they are patenting a new solid-state electrode structure that would enable a viable battery with some unbelievable specs.
“Fisker’s solid-state batteries will feature three-dimensional electrodes with 2.5 times the energy density of lithium-ion batteries. Fisker claims that this technology will enable ranges of more than 500 miles on a single charge and charging times as low as one minute—faster than filling up a gas tank.”
Here’s a representation of the three-dimensional electrodes:
But its latest solid-state project is led by Dr. Fabio Albano, VP of battery systems at Fisker and the co-founder of Sakti3, which adds credibility to the effort.
Albano commented on the announcement:
“This breakthrough marks the beginning of a new era in solid-state materials and manufacturing technologies. We are addressing all of the hurdles that solid-state batteries have encountered on the path to commercialization, such as performance in cold temperatures; the use of low cost and scalable manufacturing methods; and the ability to form bulk solid-state electrodes with significant thickness and high active material loadings. We are excited to build on this foundation and move the needle in energy storage.”
Like any battery breakthrough announcement, it should be taken with a grain of salt. Most of those announcements never result in any kind of commercialization.
For this particular technology, Fisker says that it will be automotive production grade ready around 2023.
Top row (l-r): Tata Center spinoff Khethworks develops affordable irrigation for the developing world; students discuss utility research in Washington; thin, lightweight solar cell developed by Professor Vladimir Bulović and team. Bottom row (l-r): MIT’s record-setting Alcator tokamak fusion research reactor; a researcher in the MIT Energy Laboratory’s Combustion Research Facility; Professor Kripa Varanasi, whose research on slippery surfaces has led to a spinoff co-founded with Associate Provost Karen Gleason.
Photos: Tata Center for Technology and Design, MITEI, Joel Jean and Anna Osherov, Bob Mumgaard/PSFC, Energy Laboratory Archives, Bryce Vickmark
Research, education, and student activities help create a robust community focused on fueling the world’s future.
On any given day at MIT, undergraduates design hydro-powered desalination systems, graduate students test alternative fuels, and professors work to tap the huge energy-generating potential of nuclear fusion, biomaterials, and more. While some MIT researchers are modeling the impacts of policy on energy markets, others are experimenting with electrochemical forms of energy storage.
This is the robust energy community at MIT. Developed over the past 10 years with the guidance and support of the MIT Energy Initiative (MITEI) — and with roots extending back into the early days of the Institute — it has engaged more than 300 faculty members and spans more than 900 research projects across all five schools.
In addition, MIT offers a multidisciplinary energy minor and myriad energy-related events and activities throughout the year. Together, these efforts ensure that students who arrive on campus with an interest in energy have free rein to pursue their ambitions.
Opportunities for students
“The MIT energy ecosystem is an incredible system, and it’s built from the ground up,” says Robert C. Armstrong, a professor of chemical engineering and the director of MITEI, which is overseen at the Institute level by Vice President for Research Maria Zuber. “It begins with extensive student involvement in energy.”
Opportunities begin the moment undergraduates arrive on campus, with a freshman pre-orientation program offered through MITEI that includes such hands-on activities as building motors and visiting the Institute’s nuclear research reactor.
“I got accepted into the pre-orientation program and from there, I was just hooked. I learned about solar technology, wind technology, different types of alternative fuels, bio fuels, even wave power,” says graduate student Priyanka Chatterjee ’15, who minored in energy studies and majored in mechanical and ocean engineering.
Those who choose the minor take a core set of subjects encompassing energy science, technology, and social science. Those interested in a deep dive into research can participate in the Energy Undergraduate Research Opportunities Program (UROP), which provides full-time summer positions. UROP students are mentored by graduate students and postdocs, many of them members of the Society of Energy Fellows, who are also conducting their own energy research at MIT.
For extracurricular activities, students can join the MIT Energy Club, which is among the largest student-run organizations at MIT with more than 5,000 members. They can also compete for the MIT Clean Energy Prize, a student competition that awards more than $200,000 each year for energy innovation. And there are many other opportunities.
The Tata Center for Technology and Design, now in its sixth year, extends MIT’s reach abroad. It supports 65 graduate students every year who conduct research central to improving life in developing countries — including lowering costs of rural electrification and using solar energy in novel ways.
Students have other opportunities to conduct and share energy research internationally as well.
“Over the years, MITEI has made it possible for several of the students I’ve advised to engage more directly in global energy and climate policy negotiations,” says Valerie Karplus, an assistant professor of global economics and management. “In 2015, I joined them at the Paris climate conference, which was a tremendous educational and outreach experience for all of us.”
“What is important is to provide our students a holistic understanding of the energy challenges,” says MIT Associate Dean for Innovation Vladimir Bulović.
Adds Karplus: “There’s been an evolution in thinking from ‘How do we build a better mousetrap?’ to ‘How do we bring about change in society at a system level?’”
This kind of thinking is at the root of MIT’s multidisciplinary approach to addressing the global energy challenge — and it has been since MITEI was conceived and launched by then-MIT President Susan Hockfield, a professor of neuroscience. While energy research has been part of the Institute since its founding (MIT’s first president, William Barton Rogers, famously collapsed and died after uttering the words “bituminous coal” at the 1882 commencement), the concerted effort to connect researchers across the five schools for collaborative projects is a more recent development.
“The objective of MITEI was really to solve the big energy problems, which we feel needs all of the schools’ and departments’ contributions,” says Ernest J. Moniz, a professor emeritus of physics and special advisor to MIT’s president. Moniz was the founding director of MITEI before serving as U.S. Secretary of Energy during President Obama’s administration.
Hockfield says great technology by itself “can’t go anywhere without great policy.”
“It’s the economics, it’s the sociology, it’s the science and the engineering, it’s the architecture — it’s all of the pieces of MIT that had to come together if we were going to develop really impactful sustainable energy solutions,” she says.
This multidisciplinary approach is evident in much of MIT’s energy research — notably the series of comprehensive studies MITEI has conducted on such topics as the future of solar energy, natural gas, the electric grid, and more.
“To make a better world, it’s essential that we figure out how to take what we’ve learned at MIT in energy and get that out into the world,” Armstrong says.
MITEI’s eight low-carbon energy research centers — focused on a range of topics from materials design to solar generation to carbon capture and storage — similarly address challenges on multiple technology and policy fronts. These centers are a core component of MIT’s five-year Plan for Action on Climate Change, announced by President L. Rafael Reif in October 2015. The centers employ a strategy that has been fundamental to MIT’s energy work since the founding of MITEI: broad, sustained collaboration with stakeholders from industry, government, and the philanthropic and non-governmental organization communities.
“It’s one thing to do research that’s interesting in a laboratory. It’s something very different to take that laboratory discovery into the world and deliver practical applications,” Hockfield says. “Our collaboration with industry allowed us to do that with a kind of alacrity that we could never have done on our own.”
For example, MITEI’s members have supported more than 160 energy-focused research projects, representing $21.4 million in funding over the past nine years, through the Seed Fund Program. Projects have led to follow-on federal and industry funding, startup companies, and pilot plants for solar desalinization systems in India and Gaza, among other outcomes.
What has MIT’s energy community as a whole accomplished over the past decade? Hockfield says it’s raised the visibility of the world’s energy problems, contributed solutions — both technical and sociopolitical — and provided “an army of young people” to lead the way to a sustainable energy future.
“I couldn’t be prouder of what MIT has contributed,” she says. “We are in the midst of a reinvention of how we make energy and how we use energy. And we will develop sustainable energy practices for a larger population, a wealthier population, and a healthier planet.”
Molecular models shows the initial state of battery chemistry that leads to instability in a test cell featuring a magnesium anode
Rechargeable batteries based on magnesium, rather than lithium, have the potential to extend electric vehicle range by packing more energy into smaller batteries. But unforeseen chemical roadblocks have slowed scientific progress.
And the places where solid meets liquid – where the oppositely charged battery electrodes interact with the surrounding chemical mixture known as the electrolyte – are the known problem spots.
Now, a research team at the U.S. Department of Energy’s Joint Center for Energy Storage Research, led by scientists at Lawrence Berkeley National Laboratory (Berkeley Lab), has discovered a surprising set of chemical reactions involving magnesium that degrade battery performance even before the battery can be charged up.
The findings could be relevant to other battery materials, and could steer the design of next-generation batteries toward workarounds that avoid these newly identified pitfalls.
The team used X-ray experiments, theoretical modeling, and supercomputer simulations to develop a full understanding of the chemical breakdown of a liquid electrolyte occurring within tens of nanometers of an electrode surface that degrades battery performance. Their findings are published online in the journal Chemistry of Materials (“Instability at the Electrode/Electrolyte Interface Induced by Hard Cation Chelation and Nucleophilic Attack”).
The battery they were testing featured magnesium metal as its negative electrode (the anode) in contact with an electrolyte composed of a liquid (a type of solvent known as diglyme) and a dissolved salt, Mg(TFSI)2.
While the combination of materials they used were believed to be compatible and nonreactive in the battery’s resting state, experiments at Berkeley Lab’s Advanced Light Source (ALS), an X-ray source called a synchrotron, uncovered that this is not the case and led the study in new directions.
These molecular models show the initial state of battery chemistry that leads to instability in a test cell featuring a magnesium (Mg) anode. (Credit: Berkeley Lab)
“People had thought the problems with these materials occurred during the battery’s charging, but instead the experiments indicated that there was already some activity,” said David Prendergast, who directs the Theory of Nanostructured Materials Facility at the Molecular Foundry and served as one of the study’s leaders.
“At that point it got very interesting,” he said. “What could possibly cause these reactions between substances that are supposed to be stable under these conditions?”
Molecular Foundry researchers developed detailed simulations of the point where the electrode and electrolyte meet, known as the interface, indicating that no spontaneous chemical reactions should occur under ideal conditions, either. The simulations, though, did not account for all of the chemical details.
“Prior to our investigations,” said Ethan Crumlin, an ALS scientist who coordinated the X-ray experiments and co-led the study with Prendergast, “there were suspicions about the behavior of these materials and possible connections to poor battery performance, but they hadn’t been confirmed in a working battery.”
Commercially popular lithium-ion batteries, which power many portable electronic devices (such as mobile phones, laptops, and power tools) and a growing fleet of electric vehicles, shuttle lithium ions – lithium atoms that become charged by shedding an electron – back and forth between the two battery electrodes. These electrode materials are porous at the atomic scale and are alternatively loaded up or emptied of lithium ions as the battery is charged or discharged.
In this type of battery, the negative electrode is typically composed of carbon, which has a more limited capacity for storing these lithium ions than other materials would.
So increasing the density of stored lithium by using another material would make for lighter, smaller, more powerful batteries. Using lithium metal in the electrode, for example, can pack in more lithium ions in the same space, though it is a highly reactive substance that burns when exposed to air, and requires further research on how to best package and protect it for long-term stability.
Magnesium metal has a higher energy density than lithium metal, meaning you can potentially store more energy in a battery of the same size if you use magnesium rather than lithium.
Magnesium is also more stable than lithium. Its surface forms a self-protecting “oxidized” layer as it reacts with moisture and oxygen in the air. But within a battery, this oxidized layer is believed to reduce efficiency and shorten battery life, so researchers are looking for ways to avoid its formation.
To explore the formation of this layer in more detail, the team employed a unique X-ray technique developed recently at the ALS, called APXPS (ambient pressure X-ray photoelectron spectroscopy). This new technique is sensitive to the chemistry occurring at the interface of a solid and liquid, which makes it an ideal tool to explore battery chemistry at the surface of the electrode, where it meets the liquid electrolyte.
Simulations show the weakening of a bond in a liquid solvent due to the presence of free-floating hydroxide ions, which contain a single oxygen atom bound to a hydrogen atom. In this illustration, atoms are color-coded: hydrogen (white), oxygen (red), carbon (light blue), magnesium (green), nitrogen (dark blue), sulfur (yellow), fluorine (brown). This process degrades battery performance. (Credit: Berkeley Lab)
Even before a current was fed into the test battery, the X-ray results showed signs of chemical decomposition of the electrolyte, specifically at the interface of the magnesium electrode. The findings forced researchers to rethink their molecular-scale picture of these materials and how they interact.
What they determined is that the self-stabilizing, thin oxide surface layer that forms on the magnesium has defects and impurities that drive unwanted reactions.
“It’s not the metal itself, or its oxides, that are a problem,” Prendergast said. “It’s the fact you can have imperfections in the oxidized surface. These little disparities become sites for reactions. It feeds itself in this way.”
A further round of simulations, which proposed possible defects in the oxidized magnesium surface, showed that defects in the oxidized surface layer of the anode can expose magnesium ions that then act as traps for the electrolyte’s molecules.
If free-floating hydroxide ions – molecules containing a single oxygen atom bound to a hydrogen atom that can be formed as trace amounts of water react with the magnesium metal – meet these surface-bound molecules, they will react.
This wastes electrolyte, drying out the battery over time. And the products of these reactions foul the anode’s surface, impairing the battery’s function.
It took several iterations back and forth, between the experimental and theoretical members of the team, to develop a model consistent with the X-ray measurements. The efforts were supported by millions of hours’ worth of computing power at the Lab’s National Energy Research Scientific Computing Center.
Researchers noted the importance of having access to X-ray techniques, nanoscale expertise, and computing resources at the same Lab.
The results could be relevant to other types of battery materials, too, including prototypes based on lithium or aluminum metal. Prendergast said, “This could be a more general phenomenon defining electrolyte stability.”
Crumlin added, “We’ve already started running new simulations that could show us how to modify the electrolyte to reduce the instability of these reactions.” Likewise, he said, it may be possible to tailor the surface of the magnesium to reduce or eliminate some of the unwanted chemical reactivity.
“Rather than allowing it to create its own interface, you could construct it yourself to control and stabilize the interface chemistry,” he added. “Right now it leads to uncontrollable events.”
Source: By Glenn Roberts Jr., Lawrence Berkeley National Laboratory
Images show the difference between paper prior to metallization (left) and the paper coated with conductive nanoparticles. Credit: Ko et al., published in Nature Communications
Using a simple layer-by-layer coating technique, researchers from the U.S. and Korea have developed a paper-based flexible supercapacitor that could be used to help power wearable devices. The device uses metallic nanoparticles to coat cellulose fibers in the paper, creating supercapacitor electrodes with high energy and power densities — and the best performance so far in a textile-based supercapacitor.
By implanting conductive and charge storage materials in the paper, the technique creates large surface areas that function as current collectors and nanoparticle reservoirs for the electrodes. Testing shows that devices fabricated with the technique can be folded thousands of times without affecting conductivity.
“This type of flexible energy storage device could provide unique opportunities for connectivity among wearable and internet of things devices,” said Seung Woo Lee, an assistant professor in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “We could support an evolution of the most advanced portable electronics. We also have an opportunity to combine this supercapacitor with energy-harvesting devices that could power biomedical sensors, consumer and military electronics, and similar applications.”
The research, done with collaborators at Korea University, was supported by the National Research Foundation of Korea and reported September 14 in the journal Nature Communications.
Energy storage devices are generally judged on three properties: their energy density, power density and cycling stability. Supercapacitors often have high power density, but low energy density — the amount of energy that can be stored — compared to batteries, which often have the opposite attributes. In developing their new technique, Lee and collaborator Jinhan Cho from the Department of Chemical and Biological Engineering at Korea University set out to boost energy density of the supercapacitors while maintaining their high power output.
The researchers began by dipping paper samples into a beaker of solution containing an amine surfactant material designed to bind the gold nanoparticles to the paper. Next they dipped the paper into a solution containing gold nanoparticles. Because the fibers are porous, the surfactants and nanoparticles enter the fibers and become strongly attached, creating a conformal coating on each fiber.
By repeating the dipping steps, the researchers created a conductive paper on which they added alternating layers of metal oxide energy storage materials such as manganese oxide. The ligand-mediated layer-by-layer approach helped minimize the contact resistance between neighboring metal and/or metal oxide nanonparticles. Using the simple process done at room temperatures, the layers can be built up to provide the desired electrical properties.
“It’s basically a very simple process,” Lee said. “The layer-by-layer process, which we did in alternating beakers, provides a good conformal coating on the cellulose fibers. We can fold the resulting metallized paper and otherwise flex it without damage to the conductivity.”
Though the research involved small samples of paper, the solution-based technique could likely be scaled up using larger tanks or even a spray-on technique. “There should be no limitation on the size of the samples that we could produce,” Lee said. “We just need to establish the optimal layer thickness that provides good conductivity while minimizing the use of the nanoparticles to optimize the tradeoff between cost and performance.”
The researchers demonstrated that their self-assembly technique improves several aspects of the paper supercapacitor, including its areal performance, an important factor for measuring flexible energy-storage electrodes. The maximum power and energy density of the metallic paper-based supercapacitors are estimated to be 15.1mWcm?2 and 267.3 ?Wh cm?2, respectively, substantially outperforming conventional paper or textile supercapacitors.
The next steps will include testing the technique on flexible fabrics, and developing flexible batteries that could work with the supercapacitors. The researchers used gold nanoparticles because they are easy to work with, but plan to test less expensive metals such as silver and copper to reduce the cost.
During his Ph.D. work, Lee developed the layer-by-layer self-assembly process for energy storage using different materials. With his Korean collaborators, he saw a new opportunity to apply that to flexible and wearable devices with nanoparticles.
“We have nanoscale control over the coating applied to the paper,” he added. “If we increase the number of layers, the performance continues to increase. And it’s all based on ordinary paper.”
Extending the battery life of our tech is something that preoccupies manufacturers and consumers alike. With every new phone launch we’re treated to new features, such as increasingly high-res displays and better cameras, but it’s longer battery life we all want. For most of us, being able to use our phone for a full day still means charging it every night, or lugging your charger around all day and hunting for a power socket. And when the electric car revolution reaches full speed, fast-charging, long-life batteries are going to be essential.
Advances in battery life are being made all the time, even if we’re yet to see the full benefits in our day-to-day gadgets.
But what’s beyond that? Wireless power. And we don’t mean laying our phone on a charging pad – we’re talking about long-range wireless power. If this is cracked we could have all our devices at full juice all the time, no matter where we are.
The current tech
The batteries in your current phone, and in electric cars, are lithium-ion. These charge quickly, last for plenty of cycles and offer decent capacity. But devices are more juice-hungry than ever, and with cars in particular fast charging needs to become more effective, because batteries aren’t going away any time soon.
While wireless power could be a viable option in the future, in the short-to-medium term we need to enhance batteries so that individuals and energy providers can first transition from fossil fuels to green renewable power.
Louis Shaffer of power management solutions firm Eaton tells TechRadar: “We constantly hear about battery breakthroughs but still have the same lithium-ion batteries in our phones. Innovation takes time. It took over 30 years for li-ion batteries to enter the mainstream, from their invention in the 1980s to featuring in iPhones.”
Another factor in slowing this progress is highlighted by Chris Slattery, product manager at smart lighting manufacturer Tridonic. “The interesting point with mobile phones is that one of the major factors for upgrading your phone is the degradation of the current phone’s battery life,“ he says.
“Increasing the life of these batteries removes a major reason for upgrading to the latest smartphone when the feature set itself doesn’t change that greatly.”
Ultracapacitors are seen by many as the future of energy storage, as they store energy in an electric field, rather than in a chemical reaction as a battery does, meaning they can survive hundreds of thousands more charge and discharge cycles than a battery can.
Taavi Madiburk is CEO of Skeleton Technologies, a global leader in ultracapacitor-based storage solutions. He says: “The future, we believe, lies not in replacing lithium-ion, but coupling this technology with ultracapacitors in a hybrid approach.
“In doing so, it is possible to benefit from both the high energy density of batteries, and the high power density and output of ultracapacitors.
“Ultracapacitors can be re-charged in a matter of 2-3 seconds, providing one million deep charge/discharge cycles. Also, with ultracapacitors protecting batteries from high power surges, the lifetime of the battery pack is increased by 50% and the range by 10%.
Skeleton is already working to improve power grids to cater for the growing number of electric cars. It sees current large-scale electrical grids being replaced in certain areas by smaller, less centralized grids called microgrids, and, Madiburk adds, “We’re currently working on with ultracapacitors as a piece of that puzzle.”
Solid state batteries
One of the major advances in battery tech right now sticks with good old lithium.
Solid-state lithium batteries dispense with the electrolyte liquid that transfers charged particles, making them safer than current batteries yet still able to operate at super-capacitor levels, meaning that charging and discharging can happen faster.
This is great for car batteries, as it means more power can be utilized by the car for quick pull-away speed, but fast charging will mean drivers need to spend less time at charging stations.
One example of this, from , is a battery that can be fully charged from empty in just seven minutes.
Another promising area is , which have been placed in a car to deliver a whopping 1,100 miles on a single charge. Then there are , which – while still lithium-ion – manage to offer three times better performance than lithium-ion while being cheaper to make, non-toxic and environmentally friendly.
Whisper it, but one of the big hopes for improved batteries for a while now has been graphene. The Grabat battery from charges 33 times faster than lithium-ion units, and can deliver high power too, making it ideal for cars.
One way to go without batteries is to make gadgets super-low power consuming. A phone has been built that doesn’t even require a battery, so low are its power needs – and it was achieved using components that are available to anyone.
Engineers at the University of Washington designed the phone, which is able to pull power from the environment, with radio signals and light harvested by an antenna and tiny solar cell.
The result is enough power to run the 3.5 microwatt-consuming phone. You’re limited to making calls only, but the idea having a tiny credit card-sized backup phone in your wallet will appeal to everyone from constantly on-the-move workers who need to stay in touch, to hikers.
Other breakthroughs have also been based on drawing ambient power from the world around us. , so that simply talking into your phone generates power to charge it.
MIT scientists, meanwhile, have shown off a way to harvest power from water dew in the air; they’ve only been able to create a potential one microwatt so far, but combine these methods, throw in a bit more evolution and we could be looking at a battery-free future.
Over the air power
The dream of transmitting power over the air has existed since the days of the legendary inventor and electrical engineer Nikolas Tesla, but it’s only recently started to become a reality. One company that claims to have mastered the technology, taking it beyond the close-range Qi wireless charging now found in many smartphones, is uBeam.
The uBeam system was cracked by 25-year-old astrobiology grad Meredith Perry, who has since received over $28 million in funding.
This system uses microwaves to transmit energy several metres across a room to power devices. Perry has shown it off charging phones, but says it could be applied to TVs, computers and even cars.
It uses a lot of power, costs a lot to manufacture and offers a pretty slow charging rate; but there are no wires to be seen, and this way of delivering power could hail a future without batteries.
If it could be made efficient on a large scale, in a similar way to mobile phone networks, all our devices could draw power from such a system. Imagine phones and electric cars that never need charging.
But is this future as close as uBeam would have its investors and us believe? Probably not.
This is where things get really interesting – harnessing the power of human beings. Not like in The Matrix, where we’re reduced to a glorified battery, but through friction generated by movement.
Scientists have shown off the tech in action, powering 12 LED bulbs. That’s not going to change the way you use your gadgets right now, but it’s a step in the right direction.
The technology uses a 50nm thin gold film sitting under silicone rubber nanopillars which create maximum surface area with the skin. The result is lots of friction, and all the user has to do is strap the unit on, making it ideal for wearables.
And the Bill Gates Foundation has even developed a process that harvests enough power from our urine to charge a phone, dubbed the Microbial Fuel Cell; that’s pretty much the definition of sustainable power.
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Study explains conflicting results from other experiments, may lead to batteries with more energy per pound.
Battery researchers agree that one of the most promising possibilities for future battery technology is the lithium-air (or lithium-oxygen) battery, which could provide three times as much power for a given weight as today’s leading technology, lithium-ion batteries. But tests of various approaches to creating such batteries have produced conflicting and confusing results, as well as controversies over how to explain them.
Now, a team at MIT has carried out detailed tests that seem to resolve the questions surrounding one promising material for such batteries: a compound called lithium iodide (LiI). The compound was seen as a possible solution to some of the lithium-air battery’s problems, including an inability to sustain many charging-discharging cycles, but conflicting findings had raised questions about the material’s usefulness for this task. The new study explains these discrepancies, and although it suggests that the material might not be suitable after all, the work provides guidance for efforts to overcome LiI’s drawbacks or find alternative materials.
The new results appear in the journal Energy and Environmental Science, in a paper by Yang Shao-Horn, MIT’s W.M. Keck Professor of Energy; Paula Hammond, the David H. Koch Professor in Engineering and head of the Department of Chemical Engineering; Michal Tulodziecki, a recent MIT postdoc at the Research Laboratory of Electronics; Graham Leverick, an MIT graduate student; Yu Katayama, a visiting student; and three others.
The promise of the lithium-air battery comes from the fact one of the two electrodes, which are usually made of metal or metal oxides, is replaced with air that flows in and out of the battery; a weightless substance is thus substituted for one of the heavy components. The other electrode in such batteries would be pure metallic lithium, a lightweight element.
But that theoretical promise has been limited in practice because of three issues: the need for high voltages for charging, a low efficiency with regard to getting back the amount of energy put in, and low cycle lifetimes, which result from instability in the battery’s oxygen electrode. Researchers have proposed adding lithium iodide in the electrolyte as a way of addressing these problems. But published results have been contradictory, with some studies finding the LiI does improve the cycling life, “while others show that the presence of LiI leads to irreversible reactions and poor battery cycling,” Shao-Horn says.
Previously, “most of the research was focused on organics” to make lithium-air batteries feasible, says Michal Tulodziecki, the paper’s lead author. But most of these organic compounds are not stable, he says, “and that’s why there’s been a great focus on lithium iodide [an inorganic material], which some papers said helps the batteries achieve thousands of cycles. But others say no, it will damage the battery.” In this new study, he says, “we explored in detail how lithium iodide affects the process, with and without water,” a comparison which turned out to be significant.
The team looked at the role of LiI on lithium-air battery discharge, using a different approach from most other studies. One set of studies was conducted with the components outside of the battery, which allowed the researchers to zero in on one part of the reaction, while the other study was done in the battery, to help explain the overall process.
They then used ultraviolet and visible-light spectroscopy and other techniques to study the reactions that took place. Both of these processes foster the production of different lithium compound such as LiOH (lithium hydroxide) in the presence of both LiI and water, instead of Li2O2 (lithium peroxide). LiI can enhance water’s reactivity and make it lose protons more easily, which promotes the formation of LiOH in these batteries and interferes with the charging process. These observations show that finding ways to suppress these reactions could make compounds such as LiI work better.
This study could point the way toward selecting a different compound instead of LiI to perform its intended function of suppressing unwanted chemical reactions at the electrode surface, Leverick says, adding that this work demonstrates the importance of “looking at the detailed mechanism carefully.”
Shao-Horn says that the new findings “help get to the bottom of this existing controversy on the role of LiI on discharge. We believe this clarifies and brings together all these different points of view.”
But this work is just one step in a long process of trying to make lithium-air technology practical, the researchers say. “There’s so much to understand,” says Leverick, “so there’s not one paper that’s going to solve it. But we will make consistent progress.”
“Lithium-oxygen batteries that run on oxygen and lithium ions are of great interest because they could enable electric vehicles of much greater range. However, one of the problems is that they are not very efficient yet,” says Larry Curtiss, a distinguished fellow at Argonne National Laboratory, who was not involved in this work. In this study, he says, “it is shown how adding a simple salt, lithium iodide, can potentially be used to make these batteries run much more efficiently. They have provided new insight into how the lithium iodide acts to help break up the solid discharge product, which will help to enable the development of these advanced battery systems.”
Curtiss adds that “there are still significant barriers remaining to be overcome before these batteries become a reality, such as getting long enough cycle life, but this is an important contribution to the field.”
The team also included recent MIT graduates Chibueze Amanchukwu PhD ’17 and David Kwabi PhD ’16, and Fanny Bardé of Toyota Motor Europe. The work was supported by Toyota Motor Europe and the Skoltech Center for Electrochemical Energy Storage, and used facilities supported by the National Science Foundation.