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    Reversing the charge

    Owners of electric vehicles (EVs) are accustomed to plugging into charging stations at home and at work and filling up their batteries with electricity from the power grid. But someday soon, when these drivers plug in, their cars will also have the capacity to reverse the flow and send electrons back to the grid. As the number of EVs climbs, the fleet’s batteries could serve as a cost-effective, large-scale energy source, with potentially dramatic impacts on the energy transition, according to a new paper published by an MIT team in the journal Energy Advances.

    “At scale, vehicle-to-grid (V2G) can boost renewable energy growth, displacing the need for stationary energy storage and decreasing reliance on firm [always-on] generators, such as natural gas, that are traditionally used to balance wind and solar intermittency,” says Jim Owens, lead author and a doctoral student in the MIT Department of Chemical Engineering. Additional authors include Emre Gençer, a principal research scientist at the MIT Energy Initiative (MITEI), and Ian Miller, a research specialist for MITEI at the time of the study.

    The group’s work is the first comprehensive, systems-based analysis of future power systems, drawing on a novel mix of computational models integrating such factors as carbon emission goals, variable renewable energy (VRE) generation, and costs of building energy storage, production, and transmission infrastructure.

    “We explored not just how EVs could provide service back to the grid — thinking of these vehicles almost like energy storage on wheels — but also the value of V2G applications to the entire energy system and if EVs could reduce the cost of decarbonizing the power system,” says Gençer. “The results were surprising; I personally didn’t believe we’d have so much potential here.”

    Displacing new infrastructure

    As the United States and other nations pursue stringent goals to limit carbon emissions, electrification of transportation has taken off, with the rate of EV adoption rapidly accelerating. (Some projections show EVs supplanting internal combustion vehicles over the next 30 years.) With the rise of emission-free driving, though, there will be increased demand for energy. “The challenge is ensuring both that there’s enough electricity to charge the vehicles and that this electricity is coming from renewable sources,” says Gençer.

    But solar and wind energy is intermittent. Without adequate backup for these sources, such as stationary energy storage facilities using lithium-ion batteries, for instance, or large-scale, natural gas- or hydrogen-fueled power plants, achieving clean energy goals will prove elusive. More vexing, costs for building the necessary new energy infrastructure runs to the hundreds of billions.

    This is precisely where V2G can play a critical, and welcome, role, the researchers reported. In their case study of a theoretical New England power system meeting strict carbon constraints, for instance, the team found that participation from just 13.9 percent of the region’s 8 million light-duty (passenger) EVs displaced 14.7 gigawatts of stationary energy storage. This added up to $700 million in savings — the anticipated costs of building new storage capacity.

    Their paper also described the role EV batteries could play at times of peak demand, such as hot summer days. “V2G technology has the ability to inject electricity back into the system to cover these episodes, so we don’t need to install or invest in additional natural gas turbines,” says Owens. “The way that EVs and V2G can influence the future of our power systems is one of the most exciting and novel aspects of our study.”

    Modeling power

    To investigate the impacts of V2G on their hypothetical New England power system, the researchers integrated their EV travel and V2G service models with two of MITEI’s existing modeling tools: the Sustainable Energy System Analysis Modeling Environment (SESAME) to project vehicle fleet and electricity demand growth, and GenX, which models the investment and operation costs of electricity generation, storage, and transmission systems. They incorporated such inputs as different EV participation rates, costs of generation for conventional and renewable power suppliers, charging infrastructure upgrades, travel demand for vehicles, changes in electricity demand, and EV battery costs.

    Their analysis found benefits from V2G applications in power systems (in terms of displacing energy storage and firm generation) at all levels of carbon emission restrictions, including one with no emissions caps at all. However, their models suggest that V2G delivers the greatest value to the power system when carbon constraints are most aggressive — at 10 grams of carbon dioxide per kilowatt hour load. Total system savings from V2G ranged from $183 million to $1,326 million, reflecting EV participation rates between 5 percent and 80 percent.

    “Our study has begun to uncover the inherent value V2G has for a future power system, demonstrating that there is a lot of money we can save that would otherwise be spent on storage and firm generation,” says Owens.

    Harnessing V2G

    For scientists seeking ways to decarbonize the economy, the vision of millions of EVs parked in garages or in office spaces and plugged into the grid for 90 percent of their operating lives proves an irresistible provocation. “There is all this storage sitting right there, a huge available capacity that will only grow, and it is wasted unless we take full advantage of it,” says Gençer.

    This is not a distant prospect. Startup companies are currently testing software that would allow two-way communication between EVs and grid operators or other entities. With the right algorithms, EVs would charge from and dispatch energy to the grid according to profiles tailored to each car owner’s needs, never depleting the battery and endangering a commute.

    “We don’t assume all vehicles will be available to send energy back to the grid at the same time, at 6 p.m. for instance, when most commuters return home in the early evening,” says Gençer. He believes that the vastly varied schedules of EV drivers will make enough battery power available to cover spikes in electricity use over an average 24-hour period. And there are other potential sources of battery power down the road, such as electric school buses that are employed only for short stints during the day and then sit idle.

    The MIT team acknowledges the challenges of V2G consumer buy-in. While EV owners relish a clean, green drive, they may not be as enthusiastic handing over access to their car’s battery to a utility or an aggregator working with power system operators. Policies and incentives would help.

    “Since you’re providing a service to the grid, much as solar panel users do, you could be paid for your participation, and paid at a premium when electricity prices are very high,” says Gençer.

    “People may not be willing to participate ’round the clock, but if we have blackout scenarios like in Texas last year, or hot-day congestion on transmission lines, maybe we can turn on these vehicles for 24 to 48 hours, sending energy back to the system,” adds Owens. “If there’s a power outage and people wave a bunch of money at you, you might be willing to talk.”

    “Basically, I think this comes back to all of us being in this together, right?” says Gençer. “As you contribute to society by giving this service to the grid, you will get the full benefit of reducing system costs, and also help to decarbonize the system faster and to a greater extent.”

    Actionable insights

    Owens, who is building his dissertation on V2G research, is now investigating the potential impact of heavy-duty electric vehicles in decarbonizing the power system. “The last-mile delivery trucks of companies like Amazon and FedEx are likely to be the earliest adopters of EVs,” Owen says. “They are appealing because they have regularly scheduled routes during the day and go back to the depot at night, which makes them very useful for providing electricity and balancing services in the power system.”

    Owens is committed to “providing insights that are actionable by system planners, operators, and to a certain extent, investors,” he says. His work might come into play in determining what kind of charging infrastructure should be built, and where.

    “Our analysis is really timely because the EV market has not yet been developed,” says Gençer. “This means we can share our insights with vehicle manufacturers and system operators — potentially influencing them to invest in V2G technologies, avoiding the costs of building utility-scale storage, and enabling the transition to a cleaner future. It’s a huge win, within our grasp.”

    The research for this study was funded by MITEI’s Future Energy Systems Center. More

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    Engineers solve a mystery on the path to smaller, lighter batteries

    A discovery by MIT researchers could finally unlock the door to the design of a new kind of rechargeable lithium battery that is more lightweight, compact, and safe than current versions, and that has been pursued by labs around the world for years.

    The key to this potential leap in battery technology is replacing the liquid electrolyte that sits between the positive and negative electrodes with a much thinner, lighter layer of solid ceramic material, and replacing one of the electrodes with solid lithium metal. This would greatly reduce the overall size and weight of the battery and remove the safety risk associated with liquid electrolytes, which are flammable. But that quest has been beset with one big problem: dendrites.

    Dendrites, whose name comes from the Latin for branches, are projections of metal that can build up on the lithium surface and penetrate into the solid electrolyte, eventually crossing from one electrode to the other and shorting out the battery cell. Researchers haven’t been able to agree on what gives rise to these metal filaments, nor has there been much progress on how to prevent them and thus make lightweight solid-state batteries a practical option.

    The new research, being published today in the journal Joule in a paper by MIT Professor Yet-Ming Chiang, graduate student Cole Fincher, and five others at MIT and Brown University, seems to resolve the question of what causes dendrite formation. It also shows how dendrites can be prevented from crossing through the electrolyte.

    Chiang says in the group’s earlier work, they made a “surprising and unexpected” finding, which was that the hard, solid electrolyte material used for a solid-state battery can be penetrated by lithium, which is a very soft metal, during the process of charging and discharging the battery, as ions of lithium move between the two sides.

    This shuttling back and forth of ions causes the volume of the electrodes to change. That inevitably causes stresses in the solid electrolyte, which has to remain fully in contact with both of the electrodes that it is sandwiched between. “To deposit this metal, there has to be an expansion of the volume because you’re adding new mass,” Chiang says. “So, there’s an increase in volume on the side of the cell where the lithium is being deposited. And if there are even microscopic flaws present, this will generate a pressure on those flaws that can cause cracking.”

    Those stresses, the team has now shown, cause the cracks that allow dendrites to form. The solution to the problem turns out to be more stress, applied in just the right direction and with the right amount of force.

    While previously, some researchers thought that dendrites formed by a purely electrochemical process, rather than a mechanical one, the team’s experiments demonstrate that it is mechanical stresses that cause the problem.

    The process of dendrite formation normally takes place deep within the opaque materials of the battery cell and cannot be observed directly, so Fincher developed a way of making thin cells using a transparent electrolyte, allowing the whole process to be directly seen and recorded. “You can see what happens when you put a compression on the system, and you can see whether or not the dendrites behave in a way that’s commensurate with a corrosion process or a fracture process,” he says.

    The team demonstrated that they could directly manipulate the growth of dendrites simply by applying and releasing pressure, causing the dendrites to zig and zag in perfect alignment with the direction of the force.

    Applying mechanical stresses to the solid electrolyte doesn’t eliminate the formation of dendrites, but it does control the direction of their growth. This means they can be directed to remain parallel to the two electrodes and prevented from ever crossing to the other side, and thus rendered harmless.

    In their tests, the researchers used pressure induced by bending the material, which was formed into a beam with a weight at one end. But they say that in practice, there could be many different ways of producing the needed stress. For example, the electrolyte could be made with two layers of material that have different amounts of thermal expansion, so that there is an inherent bending of the material, as is done in some thermostats.

    Another approach would be to “dope” the material with atoms that would become embedded in it, distorting it and leaving it in a permanently stressed state. This is the same method used to produce the super-hard glass used in the screens of smart phones and tablets, Chiang explains. And the amount of pressure needed is not extreme: The experiments showed that pressures of 150 to 200 megapascals were sufficient to stop the dendrites from crossing the electrolyte.

    The required pressure is “commensurate with stresses that are commonly induced in commercial film growth processes and many other manufacturing processes,” so should not be difficult to implement in practice, Fincher adds.

    In fact, a different kind of stress, called stack pressure, is often applied to battery cells, by essentially squishing the material in the direction perpendicular to the battery’s plates — somewhat like compressing a sandwich by putting a weight on top of it. It was thought that this might help prevent the layers from separating. But the experiments have now demonstrated that pressure in that direction actually exacerbates dendrite formation. “We showed that this type of stack pressure actually accelerates dendrite-induced failure,” Fincher says.

    What is needed instead is pressure along the plane of the plates, as if the sandwich were being squeezed from the sides. “What we have shown in this work is that when you apply a compressive force you can force the dendrites to travel in the direction of the compression,” Fincher says, and if that direction is along the plane of the plates, the dendrites “will never get to the other side.”

    That could finally make it practical to produce batteries using solid electrolyte and metallic lithium electrodes. Not only would these pack more energy into a given volume and weight, but they would eliminate the need for liquid electrolytes, which are flammable materials.

    Having demonstrated the basic principles involved, the team’s next step will be to try to apply these to the creation of a functional prototype battery, Chiang says, and then to figure out exactly what manufacturing processes would be needed to produce such batteries in quantity. Though they have filed for a patent, the researchers don’t plan to commercialize the system themselves, he says, as there are already companies working on the development of solid-state batteries. “I would say this is an understanding of failure modes in solid-state batteries that we believe the industry needs to be aware of and try to use in designing better products,” he says.

    The research team included Christos Athanasiou and Brian Sheldon at Brown University, and Colin Gilgenbach, Michael Wang, and W. Craig Carter at MIT. The work was supported by the U.S. National Science Foundation, the U.S. Department of Defense, the U.S. Defense Advanced Research Projects Agency, and the U.S. Department of Energy. More

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    On batteries, teaching, and world peace

    Over his long career as an electrochemist and professor, Donald Sadoway has earned an impressive variety of honors, from being named one of Time magazine’s 100 most influential people in 2012 to appearing on “The Colbert Report,” where he talked about “renewable energy and world peace,” according to Comedy Central.

    What does he personally consider to be his top achievements?

    “That’s easy,” he says immediately. “For teaching, it’s 3.091,” the MIT course on solid-state chemistry he led for some 18 years. An MIT core requirement, 3.091 is also one of the largest classes at the Institute. In 2003 it was the largest, with 630 students. Sadoway, who retires this year after 45 years in the Department of Materials Science and Engineering, estimates that over the years he’s taught the course to some 10,000 undergraduates.

    A passion for teaching

    Along the way he turned the class into an MIT favorite, complete with music, art, and literature. “I brought in all that enrichment because I knew that 95 percent of the students in that room weren’t going to major in anything chemical and this might be the last class they’d take in the subject. But it’s a requirement. So they’re 18 years old, they’re very smart, and many of them are very bored. You have to find a hook [to reach them]. And I did.”

    In 1995, Sadoway was named a Margaret MacVicar Faculty Fellow, an honor that recognizes outstanding classroom teaching at the Institute. Among the communications in support of his nomination:

    “His contributions are enormous and the class is in rapt attention from beginning to end. His lectures are highly articulate yet animated and he has uncommon grace and style. I was awed by his ability to introduce playful and creative elements into a core lecture…”

    Bill Gates would agree. In the early 2000s Sadoway’s lectures were shared with the world through OpenCourseWare, the web-based publication of MIT course materials. Gates was so inspired by the lectures that he asked to meet with Sadoway to learn more about his research. (Sadoway initially ignored Gates’ email because he thought his account had been hacked by MIT pranksters.)

    Research breakthroughs

    Teaching is not Sadoway’s only passion. He’s also proud of his accomplishments in electrochemistry. The discipline that involves electron transfer reactions is key to everything from batteries to the primary extraction of metals like aluminum and magnesium. “It’s quite wide-ranging,” says the John F. Elliott Professor Emeritus of Materials Chemistry.

    Sadoway’s contributions include two battery breakthroughs. First came the liquid metal battery, which could enable the large-scale storage of renewable energy. “That represents a huge step forward in the transition to green energy,” said António Campinos, president of the European Patent Office, earlier this year when Sadoway won the 2022 European Inventor Award for the invention in the category for Non-European Patent Office Countries.

    On “The Colbert Report,” Sadoway alluded to that work when he told Stephen Colbert that electrochemistry is the key to world peace. Why? Because it could lead to a battery capable of storing energy from the sun when the sun doesn’t shine and otherwise make renewables an important part of the clean energy mix. And that in turn could “plummet the price of petroleum and depose dictators all over the world without one shot being fired,” he recently recalled.

    The liquid metal battery is the focus of Ambri, one of six companies based on Sadoway’s inventions. Bill Gates was the first funder of the company, which formed in 2010 and aims to install its first battery soon. That battery will store energy from a reported 500 megawatts of on-site renewable generation, the same output as a natural gas power plant.

    Then, in August of this year, Sadoway and colleagues published a paper in Nature about “one of the first new battery chemistries in 30 years,” Sadoway says. “I wanted to invent something that was better, much better,” than the expensive lithium-ion batteries used in, for example, today’s electric cars.

    That battery is the focus of Avanti, one of three Sadoway companies formed just last year. The other two are Pure Lithium, to commercialize his inventions related to that element, and Sadoway Labs. The latter, a nonprofit, is essentially “a space to try radical innovations. We’re gonna start working on wild ideas.”

    Another focus of Sadoway’s research: green steel. Steelmaking produces huge amounts of greenhouse gases. Enter Boston Metal, another Sadoway company. This one is developing a new approach to producing steel based on research begun some 25 years ago. Unlike the current technology for producing steel, the Boston Metal approach — molten oxide electrolysis — does not use the element at the root of steel’s problems: carbon. The principal byproduct of the new system? Oxygen.

    In 2012, Sadoway gave a TED talk to 2,000 people on the liquid metal battery. He believes that that talk, which has now been seen by almost 2.5 million people, led to the wider publicity of his work — and science overall — on “The Colbert Report” and elsewhere. “The moral here is that if you step out of your comfort zone, you might be surprised at what can happen,” he concludes.

    Colleagues’ reflections

    “I met Don in 2006 when I was working for the iron and steel industry in Europe on ways to reduce greenhouse gas emissions from the production of those materials,” says Antoine Allanore, professor of metallurgy, Department of Materials Science and Engineering. “He was the same Don Sadoway that you see in recordings of his lectures: very elegant, very charismatic, and passionate about the technical solutions and underlying science of the process we were all investigating; electrolysis. A few years later, when I decided to pursue an academic career, I contacted Don and became a postdoctoral associate in his lab. That ultimately led to my becoming an MIT professor. People don’t believe me, but before I came to MIT the only thing I knew about the Institute was that Noam Chomsky was there … and Don Sadoway. And I felt, that’s a great place to be. And I stayed because I saw the exceptional things that can be accomplished at MIT and Don is the perfect example of that.”

    “I had the joy of meeting Don when I first arrived on the MIT campus in 1994,” recalls Felice Frankel, research scientist in the MIT departments of Chemical Engineering and Mechanical Engineering. “I didn’t have to talk him into the idea that researchers needed to take their images and graphics more seriously.  He got it — that it wasn’t just about pretty pictures. He was an important part of our five-year National Science Foundation project — Picturing to Learn — to bring that concept into the classroom. How lucky that was for me!”

    “Don has been a friend and mentor since we met in 1995 when I was an MIT senior,” says Luis Ortiz, co-founder and chief executive officer, Avanti Battery Co. “One story that is emblematic of Don’s insistence on excellence is from when he and I met with Bill Gates about the challenges in addressing climate change and how batteries could be the linchpin in solving them. I suggested that we create our presentation in PowerPoint [Microsoft software]. Don balked. He insisted that we present using Keynote on his MacBook Air, because ‘it looks so much better.’ I was incredulous that he wanted to walk into that venue exclusively using Apple products. Of course, he won the argument, but not without my admonition that there had better not be even a blip of an issue. In the meeting room, Microsoft’s former chief technology officer asked Don if he needed anything to hook up to the screen, ‘we have all those dongles.’ Don declined, but gave me that knowing look and whispered, ‘You see, they know, too.’ I ate my crow and we had a great long conversation without any issues.”

    “I remember when I first started working with Don on the liquid metal battery project at MIT, after I had chosen it as the topic for my master’s of engineering thesis,” adds David Bradwell, co-founder and chief technology officer, Ambri. “I was a wide-eyed graduate student, sitting in his office, amongst his art deco decorations, unique furniture, and historical and stylistic infographics, and from our first meeting, I could see Don’s passion for coming up with new and creative, yet practical scientific ideas, and for working on hard problems, in service of society. Don’s approaches always appear to be unconventional — wanting to stand out in a crowd, take the path less trodden, both based on his ideas, and his sense of style. It’s been an amazing journey working with him over the past decade-and-a-half, and I remain excited to see what other new, unconventional ideas, he can bring to this world.” More

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    New materials could enable longer-lasting implantable batteries

    For the last few decades, battery research has largely focused on rechargeable lithium-ion batteries, which are used in everything from electric cars to portable electronics and have improved dramatically in terms of affordability and capacity. But nonrechargeable batteries have seen little improvement during that time, despite their crucial role in many important uses such as implantable medical devices like pacemakers.

    Now, researchers at MIT have come up with a way to improve the energy density of these nonrechargeable, or “primary,” batteries. They say it could enable up to a 50 percent increase in useful lifetime, or a corresponding decrease in size and weight for a given amount of power or energy capacity, while also improving safety, with little or no increase in cost.

    The new findings, which involve substituting the conventionally inactive battery electrolyte with a material that is active for energy delivery, are reported today in the journal Proceedings of the National Academy of Sciences, in a paper by MIT Kavanaugh Postdoctoral Fellow Haining Gao, graduate student Alejandro Sevilla, associate professor of mechanical engineering Betar Gallant, and four others at MIT and Caltech.

    Replacing the battery in a pacemaker or other medical implant requires a surgical procedure, so any increase in the longevity of their batteries could have a significant impact on the patient’s quality of life, Gallant says. Primary batteries are used for such essential applications because they can provide about three times as much energy for a given size and weight as rechargeable batteries.

    That difference in capacity, Gao says, makes primary batteries “critical for applications where charging is not possible or is impractical.” The new materials work at human body temperature, so would be suitable for medical implants. In addition to implantable devices, with further development to make the batteries operate efficiently at cooler temperatures, applications could also include sensors in tracking devices for shipments, for example to ensure that temperature and humidity requirements for food or drug shipments are properly maintained throughout the shipping process. Or, they might be used in remotely operated aerial or underwater vehicles that need to remain ready for deployment over long periods.

    Pacemaker batteries typically last from five to 10 years, and even less if they require high-voltage functions such as defibrillation. Yet for such batteries, Gao says, the technology is considered mature, and “there haven’t been any major innovations in fundamental cell chemistries in the past 40 years.”

    The key to the team’s innovation is a new kind of electrolyte — the material that lies between the two electrical poles of the battery, the cathode and the anode, and allows charge carriers to pass through from one side to the other. Using a new liquid fluorinated compound, the team found that they could combine some of the functions of the cathode and the electrolyte in one compound, called a catholyte. This allows for saving much of the weight of typical primary batteries, Gao says.

    While there are other materials besides this new compound that could theoretically function in a similar catholyte role in a high-capacity battery, Gallant explains, those materials have lower inherent voltages that do not match those of the remainder of the material in a conventional pacemaker battery, a type known as CFx. Because the overall output from the battery can’t be more than that of the lesser of the two electrode materials,  the extra capacity would go to waste because of the voltage mismatch. But with the new material, “one of the key merits of our fluorinated liquids is that their voltage aligns very well with that of CFx,” Gallant says.

    In a conventional  CFx battery, the liquid electrolyte is essential because it allows charged particles to pass through from one electrode to the other. But “those electrolytes are actually chemically inactive, so they’re basically dead weight,” Gao says. This means about 50 percent of the battery’s key components, mainly the electrolyte, is inactive material. But in the new design with the fluorinated catholyte material, the amount of dead weight can be reduced to about 20 percent, she says.

    The new cells also provide safety improvements over other kinds of proposed chemistries that would use toxic and corrosive catholyte materials, which their formula does not, Gallant says. And preliminary tests have demonstrated a stable shelf life over more than a year, an important characteristic for primary batteries, she says.

    So far, the team has not yet experimentally achieved the full 50 percent improvement in energy density predicted by their analysis. They have demonstrated a 20 percent improvement, which in itself would be an important gain for some applications, Gallant says. The design of the cell itself has not yet been fully optimized, but the researchers can project the cell performance based on the performance of the active material itself. “We can see the projected cell-level performance when it’s scaled up can reach around 50 percent higher than the CFx cell,” she says. Achieving that level experimentally is the team’s next goal.

    Sevilla, a doctoral student in the mechanical engineering department, will be focusing on that work in the coming year. “I was brought into this project to try to understand some of the limitations of why we haven’t been able to attain the full energy density possible,” he says. “My role has been trying to fill in the gaps in terms of understanding the underlying reaction.”

    One big advantage of the new material, Gao says, is that it can easily be integrated into existing battery manufacturing processes, as a simple substitution of one material for another. Preliminary discussions with manufacturers confirm this potentially easy substitution, Gao says. The basic starting material, used for other purposes, has already been scaled up for production, she says, and its price is comparable to that of the materials currently used in CFx batteries. The cost of batteries using the new material is likely to be comparable to the existing batteries as well, she says. The team has already applied for a patent on the catholyte, and they expect that the medical applications are likely to be the first to be commercialized, perhaps with a full-scale prototype ready for testing in real devices within about a year.

    Further down the road, other applications could likely take advantage of the new materials as well, such as smart water or gas meters that can be read out remotely, or devices like EZPass transponders, increasing their usable lifetime, the researchers say. Power for drone aircraft or undersea vehicles would require higher power and so may take longer to be developed. Other uses could include batteries for equipment used at remote sites, such as drilling rigs for oil and gas, including devices sent down into the wells to monitor conditions.

    The team also included Gustavo Hobold, Aaron Melemed, and Rui Guo at MIT and Simon Jones at Caltech. The work was supported by MIT Lincoln Laboratory and the Army Research Office. More

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    Simplifying the production of lithium-ion batteries

    When it comes to battery innovations, much attention gets paid to potential new chemistries and materials. Often overlooked is the importance of production processes for bringing down costs.

    Now the MIT spinout 24M Technologies has simplified lithium-ion battery production with a new design that requires fewer materials and fewer steps to manufacture each cell. The company says the design, which it calls “SemiSolid” for its use of gooey electrodes, reduces production costs by up to 40 percent. The approach also improves the batteries’ energy density, safety, and recyclability.

    Judging by industry interest, 24M is onto something. Since coming out of stealth mode in 2015, 24M has licensed its technology to multinational companies including Volkswagen, Fujifilm, Lucas TVS, Axxiva, and Freyr. Those last three companies are planning to build gigafactories (factories with gigawatt-scale annual production capacity) based on 24M’s technology in India, China, Norway, and the United States.

    “The SemiSolid platform has been proven at the scale of hundreds of megawatts being produced for residential energy-storage systems. Now we want to prove it at the gigawatt scale,” says 24M CEO Naoki Ota, whose team includes 24M co-founder, chief scientist, and MIT Professor Yet-Ming Chiang.

    Establishing large-scale production lines is only the first phase of 24M’s plan. Another key draw of its battery design is that it can work with different combinations of lithium-ion chemistries. That means 24M’s partners can incorporate better-performing materials down the line without substantially changing manufacturing processes.

    The kind of quick, large-scale production of next-generation batteries that 24M hopes to enable could have a dramatic impact on battery adoption across society — from the cost and performance of electric cars to the ability of renewable energy to replace fossil fuels.

    “This is a platform technology,” Ota says. “We’re not just a low-cost and high-reliability operator. That’s what we are today, but we can also be competitive with next-generation chemistry. We can use any chemistry in the market without customers changing their supply chains. Other startups are trying to address that issue tomorrow, not today. Our tech can address the issue today and tomorrow.”

    A simplified design

    Chiang, who is MIT’s Kyocera Professor of Materials Science and Engineering, got his first glimpse into large-scale battery production after co-founding another battery company, A123 Systems, in 2001. As that company was preparing to go public in the late 2000s, Chiang began wondering if he could design a battery that would be easier to manufacture.

    “I got this window into what battery manufacturing looked like, and what struck me was that even though we pulled it off, it was an incredibly complicated manufacturing process,” Chiang says. “It derived from magnetic tape manufacturing that was adapted to batteries in the late 1980s.”

    In his lab at MIT, where he’s been a professor since 1985, Chiang started from scratch with a new kind of device he called a “semi-solid flow battery” that pumps liquids carrying particle-based electrodes to and from tanks to store a charge.

    In 2010, Chiang partnered with W. Craig Carter, who is MIT’s POSCO Professor of Materials Science and Engineering, and the two professors supervised a student, Mihai Duduta ’11, who explored flow batteries for his undergraduate thesis. Within a month, Duduta had developed a prototype in Chiang’s lab, and 24M was born. (Duduta was the company’s first hire.)

    But even as 24M worked with MIT’s Technology Licensing Office (TLO) to commercialize research done in Chiang’s lab, people in the company including Duduta began rethinking the flow battery concept. An internal cost analysis by Carter, who consulted for 24M for several years, ultimately lead the researchers to change directions.

    That left the company with loads of the gooey slurry that made up the electrodes in their flow batteries. A few weeks after Carter’s cost analysis, Duduta, then a senior research scientist at 24M, decided to start using the slurry to assemble batteries by hand, mixing the gooey electrodes directly into the electrolyte. The idea caught on.

    The main components of batteries are the positive and negatively charged electrodes and the electrolyte material that allows ions to flow between them. Traditional lithium-ion batteries use solid electrodes separated from the electrolyte by layers of inert plastics and metals, which hold the electrodes in place.

    Stripping away the inert materials of traditional batteries and embracing the gooey electrode mix gives 24M’s design a number of advantages.

    For one, it eliminates the energy-intensive process of drying and solidifying the electrodes in traditional lithium-ion production. The company says it also reduces the need for more than 80 percent of the inactive materials in traditional batteries, including expensive ones like copper and aluminum. The design also requires no binder and features extra thick electrodes, improving the energy density of the batteries.

    “When you start a company, the smart thing to do is to revisit all of your assumptions  and ask what is the best way to accomplish your objectives, which in our case was simply-manufactured, low-cost batteries,” Chiang says. “We decided our real value was in making a lithium-ion suspension that was electrochemically active from the beginning, with electrolyte in it, and you just use the electrolyte as the processing solvent.”

    In 2017, 24M participated in the MIT Industrial Liaison Program’s STEX25 Startup Accelerator, in which Chiang and collaborators made critical industry connections that would help it secure early partnerships. 24M has also collaborated with MIT researchers on projects funded by the Department of Energy.

    Enabling the battery revolution

    Most of 24M’s partners are eyeing the rapidly growing electric vehicle (EV) market for their batteries, and the founders believe their technology will accelerate EV adoption. (Battery costs make up 30 to 40 percent of the price of EVs, according to the Institute for Energy Research).

    “Lithium-ion batteries have made huge improvements over the years, but even Elon Musk says we need some breakthrough technology,” Ota says, referring to the CEO of EV firm Tesla. “To make EVs more common, we need a production cost breakthrough; we can’t just rely on cost reduction through scaling because we already make a lot of batteries today.”

    24M is also working to prove out new battery chemistries that its partners could quickly incorporate into their gigafactories. In January of this year, 24M received a grant from the Department of Energy’s ARPA-E program to develop and scale a high-energy-density battery that uses a lithium metal anode and semi-solid cathode for use in electric aviation.

    That project is one of many around the world designed to validate new lithium-ion battery chemistries that could enable a long-sought battery revolution. As 24M continues to foster the creation of large scale, global production lines, the team believes it is well-positioned to turn lab innovations into ubiquitous, world-changing products.

    “This technology is a platform, and our vision is to be like Google’s Android [operating system], where other people can build things on our platform,” Ota says. “We want to do that but with hardware. That’s why we’re licensing the technology. Our partners can use the same production lines to get the benefits of new chemistries and approaches. This platform gives everyone more options.” More

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    3 Questions: Janelle Knox-Hayes on producing renewable energy that communities want

    Wind power accounted for 8 percent of U.S. electricity consumption in 2020, and is growing rapidly in the country’s energy portfolio. But some projects, like the now-defunct Cape Wind proposal for offshore power in Massachusetts, have run aground due to local opposition. Are there ways to avoid this in the future?

    MIT professors Janelle Knox-Hayes and Donald Sadoway think so. In a perspective piece published today in the journal Joule, they and eight other professors call for a new approach to wind-power deployment, one that engages communities in a process of “co-design” and adapts solutions to local needs. That process, they say, could spur additional creativity in renewable energy engineering, while making communities more amenable to existing technologies. In addition to Knox-Hayes and Sadoway, the paper’s co-authors are Michael J. Aziz of Harvard University; Dennice F. Gayme of Johns Hopkins University; Kathryn Johnson of the Colorado School of Mines; Perry Li of the University of Minnesota; Eric Loth of the University of Virginia; Lucy Y. Pao of the University of Colorado; Jessica Smith of the Colorado School of Mines; and Sonya Smith of Howard University.

    Knox-Hayes is the Lister Brothers Associate Professor of Economic Geography and Planning in MIT’s Department of Urban Studies and Planning, and an expert on the social and political context of renewable energy adoption; Sadoway is the John F. Elliott Professor of Materials Chemistry in MIT’s Department of Materials Science and Engineering, and a leading global expert on developing new forms of energy storage. MIT News spoke with Knox-Hayes about the topic.

    Q: What is the core problem you are addressing in this article?

    A: It is problematic to act as if technology can only be engineered in a silo and then delivered to society. To solve problems like climate change, we need to see technology as a socio-technical system, which is integrated from its inception into society. From a design standpoint, that begins with conversations, values assessments, and understanding what communities need.  If we can do that, we will have a much easier time delivering the technology in the end.

    What we have seen in the Northeast, in trying to meet our climate objectives and energy efficiency targets, is that we need a lot of offshore wind, and a lot of projects have stalled because a community was saying “no.” And part of the reason communities refuse projects is because they that they’ve never been properly consulted. What form does the technology take, and how would it operate within a community? That conversation can push the boundaries of engineering.

    Q: The new paper makes the case for a new practice of “co-design” in the field of renewable energy. You call this the “STEP” process, standing for all the socio-technical-political-economic issues that an engineering project might encounter. How would you describe the STEP idea? And to what extent would industry be open to new attempts to design an established technology?

    A: The idea is to bring together all these elements in an interdisciplinary process, and engage stakeholders. The process could start with a series of community forums where we bring everyone together, and do a needs assessment, which is a common practice in planning. We might see that offshore wind energy needs to be considered in tandem with the local fishing industry, or servicing the installations, or providing local workforce training. The STEP process allows us to take a step back, and start with planners, policymakers, and community members on the ground.

    It is also about changing the nature of research and practice and teaching, so that students are not just in classrooms, they are also learning to work with communities. I think formalizing that piece is important. We are starting now to really feel the impacts of climate change, so we have to confront the reality of breaking through political boundaries, even in the United States. That is the only way to make this successful, and that comes back to how can technology be co-designed.

    At MIT, innovation is the spirit of the endeavor, and that is why MIT has so many industry partners engaged in initiatives like MITEI [the MIT Energy Initiative] and the Climate Consortium. The value of the partnership is that MIT pushes the boundaries of what is possible. It is the idea that we can advance and we can do something incredible, we can innovate the future. What we are suggesting with this work is that innovation isn’t something that happens exclusively in a laboratory, but something that is very much built in partnership with communities and other stakeholders.

    Q: How much does this approach also apply to solar power, as the other leading type of renewable energy? It seems like communities also wrestle with where to locate solar arrays, or how to compensate homeowners, communities, and other solar hosts for the power they generate.

    A: I would not say solar has the same set of challenges, but rather that renewable technologies face similar challenges. With solar, there are also questions of access and siting. Another big challenge is to create financing models that provide value and opportunity at different scales. For example, is solar viable for tenants in multi-family units who want to engage with clean energy? This is a similar question for micro-wind opportunities for buildings. With offshore wind, a restriction is that if it is within sightlines, it might be problematic. But there are exciting technologies that have enabled deep wind, or the establishment of floating turbines up to 50 kilometers offshore. Storage solutions such as hydro-pneumatic energy storage, gravity energy storage or buoyancy storage can help maintain the transmission rate while reducing the number of transmission lines needed.

    In a lot of communities, the reality of renewables is that if you can generate your own energy, you can establish a level of security and resilience that feeds other benefits. 

    Nevertheless, as demonstrated in the Cape Wind case, technology [may be rejected] unless a community is involved from the beginning. Community involvement also creates other opportunities. Suppose, for example, that high school students are working as interns on renewable energy projects with engineers at great universities from the region. This provides a point of access for families and allows them to take pride in the systems they create.  It gives a further sense of purpose to the technology system, and vests the community in the system’s success. It is the difference between, “It was delivered to me,” and “I built it.” For researchers the article is a reminder that engineering and design are more successful if they are inclusive. Engineering and design processes are also meant to be accessible and fun. More

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    A lasting — and valuable — legacy

    Betar Gallant, MIT associate professor and Class of 1922 Career Development Chair in Mechanical Engineering, grew up in a curious, independently minded family. Her mother had multiple jobs over the years, including in urban planning and in the geospatial field. Her father, although formally trained in English, read textbooks of all kinds from cover to cover, taught himself numerous technical fields including engineering, and worked successfully in them. When Gallant was very young, she and her father did science experiments in the basement.

    It wasn’t until she was in her teenage years, though, that she says she got drawn into science. Her father, who had fallen ill five years before, died when Gallant was 16, and while grieving, “when I was missing him the most,” she started to look at what had captivated her father.

    “I started to take a deeper interest in the things he had spent his life working on as a way to feel closer to him in his absence,” Gallant says. “I spent a few long months one summer looking through some of the things he had worked on, and found myself reading physics textbooks. That was enough, and I was hooked.”

    The love for independently finding and understanding solutions, that she had apparently inherited from her parents, eventually took her to the professional love of her life: electrochemistry.

    As an undergraduate at MIT, Gallant did an Undergraduate Research Opportunities Program project with Professor Yang Shao-Horn’s research group that went from her sophomore year through her senior thesis. This was Gallant’s first official exposure to electrochemistry.

    “When I met Yang, she showed me very quickly how challenging and enriching electrochemistry can be, and there was real conviction and excitement in how she and her group members talked about research,” Gallant says. “It was totally eye-opening, and I’m fortunate that she was a (relatively rare) electrochemist in a mechanical engineering department, or else I likely would not have been able to go down that road.”

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    Gallant earned three degrees at MIT (’08, SM ’10, and PhD ’13). Before joining the MIT faculty in 2016, she was a Kavli Nanoscience Institute Prize Postdoctoral Fellow at Caltech in the Division of Chemistry and Chemical Engineering.

    Her passion for electrochemistry is enormous. “Electrons are just dazzling — they power so much of our everyday world, and are the key to a renewable future,” she says, explaining that despite electrons’ amazing potential, isolated electrons cannot be stored and produced on demand, because “nature doesn’t allow excessive amounts of charge imbalances to accumulate.”

    Electrons can, however, be stored on molecules, in bonds and in metal ions or nonmetal centers that are able to lose and gain electrons — as long as positive charge transfers occur to accommodate the electrons.

    “Here’s where chemistry rears its head,” Gallant says. “What types of molecules or materials can behave in this way? How do we store as much charge as possible while making the weight and volume as low as possible?”

    Gallant points out that early battery developers using lithium and ions built a technology that “has arguably shaped our modern world more than any other.

    “If you look at some early papers, the concepts of how a lithium-ion battery or a lithium metal anode worked were sketched out by hand — they had been deduced to be true, before the field even had the tools to prove all the mechanisms were actually occurring — yet even now, those ideas are still turning out to be right!”

    Gallant says, “that’s because if you truly understand the basic principles of electrochemistry, you can start to intuit how systems will behave. Once you can do that, you can really begin to engineer better materials and devices.”

    Truly her father’s daughter, Gallant’s emphasis is on independently finding solutions.

    “Ultimately, it’s a race to have the best mental models,” she says. “A great lab and lots of funding and personnel to run it are very nice, but the most valuable tools in the toolbox are solid mental models and a way of thinking about electrochemistry, which is actually very personalized depending on the researcher.”

    She says one project with immediate impact that’s coming out of her Gallant Energy and Carbon Conversion Lab relates to primary (non-rechargeable) battery work that she and her team are working to commercialize. It involves injecting new electrochemically active electrolytes into leading high-energy batteries as they’re being assembled. Replacing a conventional electrolyte with the new chemistry decreases the normally inactive weight of the battery and boosts the energy substantially, Gallant says. One important application of such batteries would be for medical devices such as pacemakers.

    “If you can extend lifetime, you’re talking about longer times between invasive replacement surgeries, which really affects patient quality of life,” she says.

    Gallant’s team is also leading efforts to enable higher-energy rechargeable lithium-ion batteries for electric vehicles. Key to a step-change in energy, and therefore driving range, is to use a lithium metal anode in place of graphite. Lithium metal is highly reactive, however, with all battery electrolytes, and its interface needs to be stabilized in ways that still elude researchers. Gallant’s team is developing design guidelines for such interfaces, and for next-generation electrolytes to form and sustain these interfaces. Gallant says that applying the technology to that purpose and commercializing it would be “a bit longer-term, but I believe this change to lithium anodes will happen, and it’s just a matter of when.”

    About six years ago, when Gallant founded her lab, she and her team started introducing carbon dioxide into batteries as a way to experiment with electrochemical conversion of the greenhouse gas. She says they realized that batteries do not present the best practical technology to mitigate CO2, but their experimentation did open up new paths to carbon capture and conversion. “That work allowed us to think creatively, and we started to realize that there is tremendous potential to manipulate CO2 reactions by carefully designing the electrochemical environment.” That led her team to the idea of conducting electrochemical transformations on CO2 from a captured state bound to a capture sorbent, replacing the energy-intense regeneration step of today’s capture processes and streamlining the process.  

    “Now we’re seeing other researchers working on that, too, and taking this idea in exciting directions — it’s a very challenging and very rich topic,” she says.

    Gallant has won awards including an MIT Bose Fellowship, the Army Research Office Young Investigator Award, the Scialog Fellowship in Energy Storage and in Negative Emissions Science, a CAREER award from the National Science Foundation, the Ruth and Joel Spira Award for Distinguished Teaching at MIT, the Electrochemical Society (ECS) Battery Division Early Career award, and an ECS-Toyota Young Investigator Award.

    These days, Gallant does some of her best thinking while brainstorming with her research group members and with her husband, who is also an academic. She says being a professor at MIT means she has “a queue of things to think about,” but she sometimes gets awarded with a revelation.

    “My brain gets overloaded because I can’t think through everything instantaneously; ideas have to get in line! So there’s a lot going on in the background at all times,” she say. “I don’t know how it works, but sometimes I’ll be going for a walk or doing something else, and an idea breaks through. Those are the fun ones.” More

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    A new concept for low-cost batteries

    As the world builds out ever larger installations of wind and solar power systems, the 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 topography that’s not always available.

    Now, researchers at MIT and elsewhere have developed a new kind of battery, made entirely from abundant and inexpensive materials, that could help to fill that gap.

    The new battery architecture, which uses aluminum and sulfur as its two electrode materials, with a molten salt electrolyte in between, is described today 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.

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

    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 says. 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 says.

    Then came 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 says. 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 degrees 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 says.

    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 says.

    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 degrees Celsius (230 degrees 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 says. “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 says, 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 says. “I guess it was serendipity for us.”

    What’s more, 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 says. 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 says. 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 these 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 says, 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 says. “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. More