More stories

  • in

    Cobalt-free batteries could power cars of the future

    Many electric vehicles are powered by batteries that contain cobalt — a metal that carries high financial, environmental, and social costs.

    MIT researchers have now designed a battery material that could offer a more sustainable way to power electric cars. The new lithium-ion battery includes a cathode based on organic materials, instead of cobalt or nickel (another metal often used in lithium-ion batteries).

    In a new study, the researchers showed that this material, which could be produced at much lower cost than cobalt-containing batteries, can conduct electricity at similar rates as cobalt batteries. The new battery also has comparable storage capacity and can be charged up faster than cobalt batteries, the researchers report.

    “I think this material could have a big impact because it works really well,” says Mircea Dincă, the W.M. Keck Professor of Energy at MIT. “It is already competitive with incumbent technologies, and it can save a lot of the cost and pain and environmental issues related to mining the metals that currently go into batteries.”

    Dincă is the senior author of the study, which appears today in the journal ACS Central Science. Tianyang Chen PhD ’23 and Harish Banda, a former MIT postdoc, are the lead authors of the paper. Other authors include Jiande Wang, an MIT postdoc; Julius Oppenheim, an MIT graduate student; and Alessandro Franceschi, a research fellow at the University of Bologna.

    Alternatives to cobalt

    Most electric cars are powered by lithium-ion batteries, a type of battery that is recharged when lithium ions flow from a positively charged electrode, called a cathode, to a negatively electrode, called an anode. In most lithium-ion batteries, the cathode contains cobalt, a metal that offers high stability and energy density.

    However, cobalt has significant downsides. A scarce metal, its price can fluctuate dramatically, and much of the world’s cobalt deposits are located in politically unstable countries. Cobalt extraction creates hazardous working conditions and generates toxic waste that contaminates land, air, and water surrounding the mines.

    “Cobalt batteries can store a lot of energy, and they have all of features that people care about in terms of performance, but they have the issue of not being widely available, and the cost fluctuates broadly with commodity prices. And, as you transition to a much higher proportion of electrified vehicles in the consumer market, it’s certainly going to get more expensive,” Dincă says.

    Because of the many drawbacks to cobalt, a great deal of research has gone into trying to develop alternative battery materials. One such material is lithium-iron-phosphate (LFP), which some car manufacturers are beginning to use in electric vehicles. Although still practically useful, LFP has only about half the energy density of cobalt and nickel batteries.

    Another appealing option are organic materials, but so far most of these materials have not been able to match the conductivity, storage capacity, and lifetime of cobalt-containing batteries. Because of their low conductivity, such materials typically need to be mixed with binders such as polymers, which help them maintain a conductive network. These binders, which make up at least 50 percent of the overall material, bring down the battery’s storage capacity.

    About six years ago, Dincă’s lab began working on a project, funded by Lamborghini, to develop an organic battery that could be used to power electric cars. While working on porous materials that were partly organic and partly inorganic, Dincă and his students realized that a fully organic material they had made appeared that it might be a strong conductor.

    This material consists of many layers of TAQ (bis-tetraaminobenzoquinone), an organic small molecule that contains three fused hexagonal rings. These layers can extend outward in every direction, forming a structure similar to graphite. Within the molecules are chemical groups called quinones, which are the electron reservoirs, and amines, which help the material to form strong hydrogen bonds.

    Those hydrogen bonds make the material highly stable and also very insoluble. That insolubility is important because it prevents the material from dissolving into the battery electrolyte, as some organic battery materials do, thereby extending its lifetime.

    “One of the main methods of degradation for organic materials is that they simply dissolve into the battery electrolyte and cross over to the other side of the battery, essentially creating a short circuit. If you make the material completely insoluble, that process doesn’t happen, so we can go to over 2,000 charge cycles with minimal degradation,” Dincă says.

    Strong performance

    Tests of this material showed that its conductivity and storage capacity were comparable to that of traditional cobalt-containing batteries. Also, batteries with a TAQ cathode can be charged and discharged faster than existing batteries, which could speed up the charging rate for electric vehicles.

    To stabilize the organic material and increase its ability to adhere to the battery’s current collector, which is made of copper or aluminum, the researchers added filler materials such as cellulose and rubber. These fillers make up less than one-tenth of the overall cathode composite, so they don’t significantly reduce the battery’s storage capacity.

    These fillers also extend the lifetime of the battery cathode by preventing it from cracking when lithium ions flow into the cathode as the battery charges.

    The primary materials needed to manufacture this type of cathode are a quinone precursor and an amine precursor, which are already commercially available and produced in large quantities as commodity chemicals. The researchers estimate that the material cost of assembling these organic batteries could be about one-third to one-half the cost of cobalt batteries.

    Lamborghini has licensed the patent on the technology. Dincă’s lab plans to continue developing alternative battery materials and is exploring possible replacement of lithium with sodium or magnesium, which are cheaper and more abundant than lithium. More

  • in

    Angela Belcher delivers 2023 Dresselhaus Lecture on evolving organisms for new nanomaterials

    “How do we get to making nanomaterials that haven’t been evolved before?” asked Angela Belcher at the 2023 Mildred S. Dresselhaus Lecture at MIT on Nov. 20. “We can use elements that biology has already given us.”

    The combined in-person and virtual audience of over 300 was treated to a light-up, 3D model of M13 bacteriophage, a virus that only infects bacteria, complete with a pull-out strand of DNA. Belcher used the feather-boa-like model to show how her research group modifies the M13’s genes to add new DNA and peptide sequences to template inorganic materials.

    “I love controlling materials at the nanoscale using biology,” said Belcher, the James Mason Crafts Professor of Biological Engineering, materials science professor, and of the Koch Institute of Integrative Cancer Research at MIT. “We all know if you control materials at the nanoscale and you can start to tune them, then you can have all kinds of different applications.” And the opportunities are indeed vast — from building batteries, fuel cells, and solar cells to carbon sequestration and storage, environmental remediation, catalysis, and medical diagnostics and imaging.

    Belcher sprinkled her talk with models and props, lined up on a table at the front of the 10-250 lecture hall, to demonstrate a wide variety of concepts and projects made possible by the intersection of biology and nanotechnology.

    Play video

    2023 Mildred S. Dresselhaus Lecture: Angela BelcherVideo: MIT.nano

    Energy storage and environment

    “How do you go from a DNA sequence to a functioning battery?” posed Belcher. Grabbing a model of a large carbon nanotube, she explained how her group engineered a phage to pick up carbon nanotubes that would wind all the way around the virus and then fill in with different cathode or anode materials to make nanowires for battery electrodes.

    How about using the M13 bacteriophage to improve the environment? Belcher referred to a project by former student Geran Zhang PhD ’19 that proved the virus can be modified for this context, too. He used the phage to template high-surface-area, carbon-based materials that can grab small molecules and break them down, Belcher said, opening a realm of possibilities from cleaning up rivers to developing chemical warfare agents to combating smog.

    Belcher’s lab worked with the U.S. Army to produce protective clothing and masks made of these carbon-based virus nanofibers. “We went from five liters in our lab to a thousand liters, then 10,000 liters in the army labs where we’re able to make kilograms of the material,” Belcher said, stressing the importance of being able to test and prototype at scale.

    Imaging tools and therapeutics in cancer

    In the area of biomedical imaging, Belcher explained, a lot less is known in near-infrared imaging — imaging in wavelengths above 1,000 nanometers — than other imaging techniques, yet with near-infrared scientists can see much deeper inside the body. Belcher’s lab built their own systems to image at these wavelengths. The third generation of this system provides real-time, sub-millimeter optical imaging for guided surgery.

    Working with Sangeeta Bhatia, the John J. and Dorothy Wilson Professor of Engineering, Belcher used carbon nanotubes to build imaging tools that find tiny tumors during surgery that doctors otherwise would not be able to see. The tool is actually a virus engineered to carry with it a fluorescent, single-walled carbon nanotube as it seeks out the tumors.

    Nearing the end of her talk, Belcher presented a goal: to develop an accessible detection and diagnostic technology for ovarian cancer in five to 10 years.

    “We think that we can do it,” Belcher said. She described her students’ work developing a way to scan an entire fallopian tube, as opposed to just one small portion, to find pre-cancer lesions, and talked about the team of MIT faculty, doctors, and researchers working collectively toward this goal.

    “Part of the secret of life and the meaning of life is helping other people enjoy the passage of time,” said Belcher in her closing remarks. “I think that we can all do that by working to solve some of the biggest issues on the planet, including helping to diagnose and treat ovarian cancer early so people have more time to spend with their family.”

    Honoring Mildred S. Dresselhaus

    Belcher was the fifth speaker to deliver the Dresselhaus Lecture, an annual event organized by MIT.nano to honor the late MIT physics and electrical engineering Institute Professor Mildred Dresselhaus. The lecture features a speaker from anywhere in the world whose leadership and impact echo Dresselhaus’s life, accomplishments, and values.

    “Millie was and is a huge hero of mine,” said Belcher. “Giving a lecture in Millie’s name is just the greatest honor.”

    Belcher dedicated the talk to Dresselhaus, whom she described with an array of accolades — a trailblazer, a genius, an amazing mentor, teacher, and inventor. “Just knowing her was such a privilege,” she said.

    Belcher also dedicated her talk to her own grandmother and mother, both of whom passed away from cancer, as well as late MIT professors Susan Lindquist and Angelika Amon, who both died of ovarian cancer.

    “I’ve been so fortunate to work with just the most talented and dedicated graduate students, undergraduate students, postdocs, and researchers,” concluded Belcher. “It has been a pure joy to be in partnership with all of you to solve these very daunting problems.” More

  • in

    Pixel-by-pixel analysis yields insights into lithium-ion batteries

    By mining data from X-ray images, researchers at MIT, Stanford University, SLAC National Accelerator, and the Toyota Research Institute have made significant new discoveries about the reactivity of lithium iron phosphate, a material used in batteries for electric cars and in other rechargeable batteries.

    The new technique has revealed several phenomena that were previously impossible to see, including variations in the rate of lithium intercalation reactions in different regions of a lithium iron phosphate nanoparticle.

    The paper’s most significant practical finding — that these variations in reaction rate are correlated with differences in the thickness of the carbon coating on the surface of the particles — could lead to improvements in the efficiency of charging and discharging such batteries.

    “What we learned from this study is that it’s the interfaces that really control the dynamics of the battery, especially in today’s modern batteries made from nanoparticles of the active material. That means that our focus should really be on engineering that interface,” says Martin Bazant, the E.G. Roos Professor of Chemical Engineering and a professor of mathematics at MIT, who is the senior author of the study.

    This approach to discovering the physics behind complex patterns in images could also be used to gain insights into many other materials, not only other types of batteries but also biological systems, such as dividing cells in a developing embryo.

    “What I find most exciting about this work is the ability to take images of a system that’s undergoing the formation of some pattern, and learning the principles that govern that,” Bazant says.

    Hongbo Zhao PhD ’21, a former MIT graduate student who is now a postdoc at Princeton University, is the lead author of the new study, which appears today in Nature. Other authors include Richard Bratz, the Edwin R. Gilliland Professor of Chemical Engineering at MIT; William Chueh, an associate professor of materials science and engineering at Stanford and director of the SLAC-Stanford Battery Center; and Brian Storey, senior director of Energy and Materials at the Toyota Research Institute.

    “Until now, we could make these beautiful X-ray movies of battery nanoparticles at work, but it was challenging to measure and understand subtle details of how they function because the movies were so information-rich,” Chueh says. “By applying image learning to these nanoscale movies, we can extract insights that were not previously possible.”

    Modeling reaction rates

    Lithium iron phosphate battery electrodes are made of many tiny particles of lithium iron phosphate, surrounded by an electrolyte solution. A typical particle is about 1 micron in diameter and about 100 nanometers thick. When the battery discharges, lithium ions flow from the electrolyte solution into the material by an electrochemical reaction known as ion intercalation. When the battery charges, the intercalation reaction is reversed, and ions flow in the opposite direction.

    “Lithium iron phosphate (LFP) is an important battery material due to low cost, a good safety record, and its use of abundant elements,” Storey says. “We are seeing an increased use of LFP in the EV market, so the timing of this study could not be better.”

    Before the current study, Bazant had done a great deal of theoretical modeling of patterns formed by lithium-ion intercalation. Lithium iron phosphate prefers to exist in one of two stable phases: either full of lithium ions or empty. Since 2005, Bazant has been working on mathematical models of this phenomenon, known as phase separation, which generates distinctive patterns of lithium-ion flow driven by intercalation reactions. In 2015, while on sabbatical at Stanford, he began working with Chueh to try to interpret images of lithium iron phosphate particles from scanning tunneling X-ray microscopy.

    Using this type of microscopy, the researchers can obtain images that reveal the concentration of lithium ions, pixel-by-pixel, at every point in the particle. They can scan the particles several times as the particles charge or discharge, allowing them to create movies of how lithium ions flow in and out of the particles.

    In 2017, Bazant and his colleagues at SLAC received funding from the Toyota Research Institute to pursue further studies using this approach, along with other battery-related research projects.

    By analyzing X-ray images of 63 lithium iron phosphate particles as they charged and discharged, the researchers found that the movement of lithium ions within the material could be nearly identical to the computer simulations that Bazant had created earlier. Using all 180,000 pixels as measurements, the researchers trained the computational model to produce equations that accurately describe the nonequilibrium thermodynamics and reaction kinetics of the battery material.
    By analyzing X-ray images of lithium iron phosphate particles as they charged and discharged, researchers have shown that the movement of lithium ions within the material was nearly identical to computer simulations they had created earlier.  In each pair, the actual particles are on the left and the simulations are on the right.Courtesy of the researchers

    “Every little pixel in there is jumping from full to empty, full to empty. And we’re mapping that whole process, using our equations to understand how that’s happening,” Bazant says.

    The researchers also found that the patterns of lithium-ion flow that they observed could reveal spatial variations in the rate at which lithium ions are absorbed at each location on the particle surface.

    “It was a real surprise to us that we could learn the heterogeneities in the system — in this case, the variations in surface reaction rate — simply by looking at the images,” Bazant says. “There are regions that seem to be fast and others that seem to be slow.”

    Furthermore, the researchers showed that these differences in reaction rate were correlated with the thickness of the carbon coating on the surface of the lithium iron phosphate particles. That carbon coating is applied to lithium iron phosphate to help it conduct electricity — otherwise the material would conduct too slowly to be useful as a battery.

    “We discovered at the nano scale that variation of the carbon coating thickness directly controls the rate, which is something you could never figure out if you didn’t have all of this modeling and image analysis,” Bazant says.

    The findings also offer quantitative support for a hypothesis Bazant formulated several years ago: that the performance of lithium iron phosphate electrodes is limited primarily by the rate of coupled ion-electron transfer at the interface between the solid particle and the carbon coating, rather than the rate of lithium-ion diffusion in the solid.

    Optimized materials

    The results from this study suggest that optimizing the thickness of the carbon layer on the electrode surface could help researchers to design batteries that would work more efficiently, the researchers say.

    “This is the first study that’s been able to directly attribute a property of the battery material with a physical property of the coating,” Bazant says. “The focus for optimizing and designing batteries should be on controlling reaction kinetics at the interface of the electrolyte and electrode.”

    “This publication is the culmination of six years of dedication and collaboration,” Storey says. “This technique allows us to unlock the inner workings of the battery in a way not previously possible. Our next goal is to improve battery design by applying this new understanding.”  

    In addition to using this type of analysis on other battery materials, Bazant anticipates that it could be useful for studying pattern formation in other chemical and biological systems.

    This work was supported by the Toyota Research Institute through the Accelerated Materials Design and Discovery program. More

  • in

    Study suggests energy-efficient route to capturing and converting CO2

    In the race to draw down greenhouse gas emissions around the world, scientists at MIT are looking to carbon-capture technologies to decarbonize the most stubborn industrial emitters.

    Steel, cement, and chemical manufacturing are especially difficult industries to decarbonize, as carbon and fossil fuels are inherent ingredients in their production. Technologies that can capture carbon emissions and convert them into forms that feed back into the production process could help to reduce the overall emissions from these “hard-to-abate” sectors.

    But thus far, experimental technologies that capture and convert carbon dioxide do so as two separate processes, that themselves require a huge amount of energy to run. The MIT team is looking to combine the two processes into one integrated and far more energy-efficient system that could potentially run on renewable energy to both capture and convert carbon dioxide from concentrated, industrial sources.

    In a study appearing today in ACS Catalysis, the researchers reveal the hidden functioning of how carbon dioxide can be both captured and converted through a single electrochemical process. The process involves using an electrode to attract carbon dioxide released from a sorbent, and to convert it into a reduced, reusable form.

    Others have reported similar demonstrations, but the mechanisms driving the electrochemical reaction have remained unclear. The MIT team carried out extensive experiments to determine that driver, and found that, in the end, it came down to the partial pressure of carbon dioxide. In other words, the more pure carbon dioxide that makes contact with the electrode, the more efficiently the electrode can capture and convert the molecule.

    Knowledge of this main driver, or “active species,” can help scientists tune and optimize similar electrochemical systems to efficiently capture and convert carbon dioxide in an integrated process.

    The study’s results imply that, while these electrochemical systems would probably not work for very dilute environments (for instance, to capture and convert carbon emissions directly from the air), they would be well-suited to the highly concentrated emissions generated by industrial processes, particularly those that have no obvious renewable alternative.

    “We can and should switch to renewables for electricity production. But deeply decarbonizing industries like cement or steel production is challenging and will take a longer time,” says study author Betar Gallant, the Class of 1922 Career Development Associate Professor at MIT. “Even if we get rid of all our power plants, we need some solutions to deal with the emissions from other industries in the shorter term, before we can fully decarbonize them. That’s where we see a sweet spot, where something like this system could fit.”

    The study’s MIT co-authors are lead author and postdoc Graham Leverick and graduate student Elizabeth Bernhardt, along with Aisyah Illyani Ismail, Jun Hui Law, Arif Arifutzzaman, and Mohamed Kheireddine Aroua of Sunway University in Malaysia.

    Breaking bonds

    Carbon-capture technologies are designed to capture emissions, or “flue gas,” from the smokestacks of power plants and manufacturing facilities. This is done primarily using large retrofits to funnel emissions into chambers filled with a “capture” solution — a mix of amines, or ammonia-based compounds, that chemically bind with carbon dioxide, producing a stable form that can be separated out from the rest of the flue gas.

    High temperatures are then applied, typically in the form of fossil-fuel-generated steam, to release the captured carbon dioxide from its amine bond. In its pure form, the gas can then be pumped into storage tanks or underground, mineralized, or further converted into chemicals or fuels.

    “Carbon capture is a mature technology, in that the chemistry has been known for about 100 years, but it requires really large installations, and is quite expensive and energy-intensive to run,” Gallant notes. “What we want are technologies that are more modular and flexible and can be adapted to more diverse sources of carbon dioxide. Electrochemical systems can help to address that.”

    Her group at MIT is developing an electrochemical system that both recovers the captured carbon dioxide and converts it into a reduced, usable product. Such an integrated system, rather than a decoupled one, she says, could be entirely powered with renewable electricity rather than fossil-fuel-derived steam.

    Their concept centers on an electrode that would fit into existing chambers of carbon-capture solutions. When a voltage is applied to the electrode, electrons flow onto the reactive form of carbon dioxide and convert it to a product using protons supplied from water. This makes the sorbent available to bind more carbon dioxide, rather than using steam to do the same.

    Gallant previously demonstrated this electrochemical process could work to capture and convert carbon dioxide into a solid carbonate form.

    “We showed that this electrochemical process was feasible in very early concepts,” she says. “Since then, there have been other studies focused on using this process to attempt to produce useful chemicals and fuels. But there’s been inconsistent explanations of how these reactions work, under the hood.”

    Solo CO2

    In the new study, the MIT team took a magnifying glass under the hood to tease out the specific reactions driving the electrochemical process. In the lab, they generated amine solutions that resemble the industrial capture solutions used to extract carbon dioxide from flue gas. They methodically altered various properties of each solution, such as the pH, concentration, and type of amine, then ran each solution past an electrode made from silver — a metal that is widely used in electrolysis studies and known to efficiently convert carbon dioxide to carbon monoxide. They then measured the concentration of carbon monoxide that was converted at the end of the reaction, and compared this number against that of every other solution they tested, to see which parameter had the most influence on how much carbon monoxide was produced.

    In the end, they found that what mattered most was not the type of amine used to initially capture carbon dioxide, as many have suspected. Instead, it was the concentration of solo, free-floating carbon dioxide molecules, which avoided bonding with amines but were nevertheless present in the solution. This “solo-CO2” determined the concentration of carbon monoxide that was ultimately produced.

    “We found that it’s easier to react this ‘solo’ CO2, as compared to CO2 that has been captured by the amine,” Leverick offers. “This tells future researchers that this process could be feasible for industrial streams, where high concentrations of carbon dioxide could efficiently be captured and converted into useful chemicals and fuels.”

    “This is not a removal technology, and it’s important to state that,” Gallant stresses. “The value that it does bring is that it allows us to recycle carbon dioxide some number of times while sustaining existing industrial processes, for fewer associated emissions. Ultimately, my dream is that electrochemical systems can be used to facilitate mineralization, and permanent storage of CO2 — a true removal technology. That’s a longer-term vision. And a lot of the science we’re starting to understand is a first step toward designing those processes.”

    This research is supported by Sunway University in Malaysia. More

  • in

    Q&A: Three Tata Fellows on the program’s impact on themselves and the world

    The Tata Fellowship at MIT gives graduate students the opportunity to pursue interdisciplinary research and work with real-world applications in developing countries. Part of the MIT Tata Center for Technology and Design, this fellowship contributes to the center’s goal of designing appropriate, practical solutions for resource-constrained communities. Three Tata Fellows — Serena Patel, Rameen Hayat Malik, and Ethan Harrison — discuss the impact of this program on their research, perspectives, and time at MIT.

    Serena Patel

    Serena Patel graduated from the University of California at Berkeley with a degree in energy engineering and a minor in energy and resources. She is currently pursuing her SM in technology and policy at MIT and is a Tata Fellow focusing on decarbonization in India using techno-economic modeling. Her interest in the intersection of technology, policy, economics, and social justice led her to attend COP27, where she experienced decision-maker and activist interactions firsthand.

    Q: How did you become interested in the Tata Fellowship, and how has it influenced your time at MIT?

    A: The Tata Center appealed to my interest in searching for creative, sustainable energy technologies that center collaboration with local-leading organizations. It has also shaped my understanding of the role of technology in sustainable development planning. Our current energy system disproportionately impacts marginalized communities, and new energy systems have the potential to perpetuate and/or create inequities. I am broadly interested in how we can put people at the core of our technological solutions and support equitable energy transitions. I specifically work on techno-economic modeling to analyze the potential for an early retirement of India’s large coal fleet and conversion to long-duration thermal energy storage. This could mitigate job losses from rapid transitions, support India’s energy system decarbonization plan, and provide a cost-effective way to retire stranded assets.

    Q: Why is interdisciplinary study important to real-world solutions for global communities, and how has working at the intersection of technology and policy influenced your research?

    A: Technology and policy work together in mediating and regulating the world around us. Technological solutions can be disruptive in all the good ways, but they can also do a lot of harm and perpetuate existing inequities. Interdisciplinary studies are important to mitigate these interrelated issues so innovative ideas in the ivory towers of Western academia do not negatively impact marginalized communities. For real-world solutions to positively impact individuals, marginalized communities need to be centered within the research design process. I think the research community’s perspective on real-world, global solutions is shifting to achieve these goals, but much work remains for resources to reach the right communities.

    The energy space is especially fascinating because it impacts everyone’s quality of life in overt or nuanced ways. I’ve had the privilege of taking classes that sit at the intersection of energy technology and policy, involving land-use law, geographic representation, energy regulation, and technology policy. In general, working at the intersection of technology and policy has shaped my perspective on how regulation influences widespread technology adoption and the overall research directions and assumptions in our energy models.

    Q: How has your experience at COP27 influenced your approach to your research?

    A: Attending COP27 at Sharm El-Sheikh, Egypt, last November influenced my understanding of the role of science, research, and activism in climate negotiations and action. Science and research are often promoted as necessary for sharing knowledge at the higher levels, but they were also used as a delay tactic by negotiators. I heard how institutional bodies meant to support fair science and research often did not reach intended stakeholders. Lofty goals or financial commitments to ensure global climate stability and resilience still lacked implementation and coordination with deep technology transfer and support. On the face of it, these agreements have impact and influence, but I heard many frustrations over the lack of tangible, local support. This has driven my research to be as context-specific as possible, to provide actionable insights and leverage different disciplines.

    I also observed the role of activism in the negotiations. Decision-makers are accountable to their country, and activists are spreading awareness and bringing transparency to the COP process. As a U.S. citizen, I suddenly became more aware of how political engagement and awareness in the country could push the boundaries of international climate agreements if the government were more aligned on climate action.

    Rameen Hayat Malik

    Rameen Hayat Malik graduated from the University of Sydney with a bachelor’s degree in chemical and biomolecular engineering and a Bachelor of Laws. She is currently pursuing her SM in technology and policy and is a Tata Fellow researching the impacts of electric vehicle (EV) battery production in Indonesia. Originally from Australia, she first became interested in the geopolitical landscape of resources trade and its implications for the clean energy transition while working in her native country’s Department of Climate Change, Energy, the Environment and Water.

    Q: How did you become interested in the Tata Fellowship, and how has it influenced your time at MIT?

    A: I came across the Tata Fellowship while looking for research opportunities that aligned with my interest in understanding how a just energy transition will occur in a global context, with a particular focus on emerging economies. My research explores the techno-economic, social, and environmental impacts of nickel mining in Indonesia as it seeks to establish itself as a major producer of EV batteries. The fellowship’s focus on community-driven research has given me the freedom to guide the scope of my research. It has allowed me to integrate a community voice into my work that seeks to understand the impact of this mining on forest-dependent communities, Indigenous communities, and workforce development.

    Q: Battery technology and production are highly discussed in the energy sector. How does your research on Indonesia’s battery production contribute to the current discussion around batteries, and what drew you to this topic?

    A: Indonesia is one of the world’s largest exporters of coal, while also having one of the largest nickel reserves in the world — a key mineral for EV battery production. This presents an exciting opportunity for Indonesia to be a leader in the energy transition, as it both seeks to phase out coal production and establish itself as a key supplier of critical minerals. It is also an opportunity to actually apply principles of a just transition to the region, which seeks to repurpose and re-skill existing coal workforces, to bring Indigenous communities into the conversation around the future of their lands, and to explore whether it is actually possible to sustainably and ethically produce nickel for EV battery production.

    I’ve always seen battery technologies and EVs as products that, at least today, are accessible to a small, privileged customer base that can afford such technologies. I’m interested in understanding how we can make such products more widely affordable and provide our lowest-income communities with the opportunities to actively participate in the transition — especially since access to transportation is a key driver of social mobility. With nickel prices impacting EV prices in such a dramatic way, unlocking more nickel supply chains presents an opportunity to make EV batteries more accessible and affordable.

    Q: What advice would you give to new students who want to be a part of real-world solutions to the climate crisis?

    A: Bring your whole self with you when engaging these issues. Quite often we get caught up with the technology or modeling aspect of addressing the climate crisis and forget to bring people and their experiences into our work. Think about your positionality: Who is your community, what are the avenues you have to bring that community along, and what privileges do you hold to empower and amplify voices that need to be heard? Find a piece of this complex puzzle that excites you, and find opportunities to talk and listen to people who are directly impacted by the solutions you are looking to explore. It can get quite overwhelming working in this space, which carries a sense of urgency, politicization, and polarization with it. Stay optimistic, keep advocating, and remember to take care of yourself while doing this important work.

    Ethan Harrison

    After earning his degree in economics and applied science from the College of William and Mary, Ethan Harrison worked at the United Nations Development Program in its Crisis Bureau as a research officer focused on conflict prevention and predictive analysis. He is currently pursuing his SM in technology and policy at MIT. In his Tata Fellowship, he focuses on the impacts of the Ukraine-Russia conflict on global vulnerability and the global energy market.

    Q: How did you become interested in the Tata Fellowship, and how has it influenced your time at MIT?

    A: Coming to MIT, one of my chief interests was figuring out how we can leverage gains from technology to improve outcomes and build pro-poor solutions in developing and crisis contexts. The Tata Fellowship aligned with many of the conclusions I drew while working in crisis contexts and some of the outstanding questions that I was hoping to answer during my time at MIT, specifically: How can we leverage technology to build sustainable, participatory, and ethically grounded interventions in these contexts?

    My research currently examines the secondary impacts of the Ukraine-Russia conflict on low- and middle-income countries — especially fragile states — with a focus on shocks in the global energy market. This includes the development of a novel framework that systematically identifies factors of vulnerability — such as in energy, food systems, and trade dependence — and quantitatively ranks countries by their level of vulnerability. By identifying the specific mechanisms by which these countries are vulnerable, we can develop a map of global vulnerability and identify key policy solutions that can insulate countries from current and future shocks.

    Q: I understand that your research deals with the relationship between oil and gas price fluctuation and political stability. What has been the most surprising aspect of this relationship, and what are its implications for global decarbonization?

    A: One surprising aspect is the degree to which citizen grievances regarding price fluctuations can quickly expand to broader democratic demands and destabilization. In Sri Lanka last year and in Egypt during the Arab spring, initial protests around fuel prices and power outages eventually led to broader demands and the loss of power by heads of state. Another surprising aspect is the popularity of fuel subsidies despite the fact that they are economically regressive: They often comprise a large proportion of GDP in poor countries, disproportionately benefit higher-income populations, and leave countries vulnerable to fiscal stress during price spikes.

    Regarding implications for global decarbonization, one project we are pursuing examines the implications of directing financing from fuel subsidies toward investments in renewable energy. Countries that rely on fossil fuels for electricity have been hit especially hard 
by price spikes from the Ukraine-Russia conflict, especially since many were carrying costly fuel subsidies to keep the price of fuel and energy artificially low. Much of the international community is advocating for low-income countries to invest in renewables and reduce their fossil fuel burden, but it’s important to explore how global decarbonization can align with efforts to end energy poverty and other Sustainable Development Goals.

    Q: How does your research impact the Tata Center’s goal of transforming policy research into real-world solutions, and why is this important?

    A: The crisis in Ukraine has shifted the international community’s focus away from other countries in crisis, such as Yemen and Lebanon. By developing a global map of vulnerability, we’re building a large evidence base on which countries have been most impacted by this crisis. Most importantly, by identifying individual channels of vulnerability for each country, we can also identify the most effective policy solutions to insulate vulnerable populations from shocks. Whether that’s advocating for short-term social protection programs or identifying more medium-term policy solutions — like fuel banks or investment in renewables — we hope providing a detailed map of sources of vulnerability can help inform the global response to shocks imposed by the Russia-Ukraine conflict and post-Covid recovery. More

  • in

    Alumnus’ thermal battery helps industry eliminate fossil fuels

    The explosion of renewable energy projects around the globe is leading to a saturation problem. As more renewable power contributes to the grid, the value of electricity is plummeting during the times of day when wind and solar hit peak productivity. The problem is limiting renewable energy investments in some of the sunniest and windiest places in the world.

    Now Antora Energy, co-founded by David Bierman SM ’14, PhD ’17, is addressing the intermittent nature of wind and solar with a low-cost, highly efficient thermal battery that stores electricity as heat to allow manufacturers and other energy-hungry businesses to eliminate their use of fossil fuels.

    “We take electricity when it’s cheapest, meaning when wind gusts are strongest and the sun is shining brightest,” Bierman explains. “We run that electricity through a resistive heater to drive up the temperature of a very inexpensive material — we use carbon blocks, which are extremely stable, produced at incredible scales, and are some of the cheapest materials on Earth. When you need to pull energy from the battery, you open a large shutter to extract thermal radiation, which is used to generate process heat or power using our thermophotovoltaic, or TPV, technology. The end result is a zero-carbon, flexible, combined heat and power system for industry.”

    Antora’s battery could dramatically expand the application of renewable energy by enabling its use in industry, a sector of the U.S. economy that accounted for nearly a quarter of all greenhouse gas emissions in 2021.

    Antora says it is able to deliver on the long-sought promise of heat-to-power TPV technology because it has achieved new levels of efficiency and scalability with its cells. Earlier this year, Antora opened a new manufacturing facility that will be capable of producing 2 megawatts of its TPV cells each year — which the company says makes it the largest TPV production facility in the world.

    Antora’s thermal battery manufacturing facilities and demonstration unit are located in sun-soaked California, where renewables make up close to a third of all electricity. But Antora’s team says its technology holds promise in other regions as increasingly large renewable projects connect to grids across the globe.

    “We see places today [with high renewables] as a sign of where things are going,” Bierman says. “If you look at the tailwinds we have in the renewable industry, there’s a sense of inevitability about solar and wind, which will need to be deployed at incredible scales to avoid a climate catastrophe. We’ll see terawatts and terawatts of new additions of these renewables, so what you see today in California or Texas or Kansas, with significant periods of renewable overproduction, is just the tip of the iceberg.”

    Bierman has been working on thermal energy storage and thermophotovoltaics since his time at MIT, and Antora’s ties to MIT are especially strong because its progress is the result of two MIT startups becoming one.

    Alumni join forces

    Bierman did his masters and doctoral work in MIT’s Department of Mechanical Engineering, where he worked on solid-state solar thermal energy conversion systems. In 2016, while taking course 15.366 (Climate and Energy Ventures), he met Jordan Kearns SM ’17, then a graduate student in the Technology and Policy Program and the Department of Nuclear Science and Engineering. The two were studying renewable energy when they began to think about the intermittent nature of wind and solar as an opportunity rather than a problem.

    “There are already places in the U.S. where we have more wind and solar at times than we know what to do with,” Kearns says. “That is an opportunity for not only emissions reductions but also for reducing energy costs. What’s the application? I don’t think the overproduction of energy was being talked about as much as the intermittency problem.”

    Kearns did research through the MIT Energy Initiative and the researchers received support from MIT’s Venture Mentoring Service and the MIT Sandbox Innovation Fund to further explore ways to capitalize on fluctuating power prices.

    Kearns officially founded a company called Medley Thermal in 2017 to help companies that use natural gas switch to energy produced by renewables when the price was right. To accomplish that, he combined an off-the-shelf electric boiler with novel control software so the companies could switch energy sources seamlessly from fossil fuel to electricity at especially windy or sunny times. Medley went on to become a finalist for the MIT Clean Energy Prize, and Kearns wanted Bierman to join him as a co-founder, but Bierman had received a fellowship to commercialize a thermal energy storage solution and decided to pursue that after graduation.

    The split ended up working out for both alumni. In the ensuing years, Kearns led Medley Thermal through a number of projects in which gradually larger companies switched from relying on natural gas or propane sources to renewable electricity from the grid. The work culminated in an installment at the Jay Peak resort in Vermont that Kearns says is one of the largest projects in the U.S. using renewable energy to produce heat. The project is expected to reduce about 2,500 tons of carbon dioxide per year.

    Bierman, meanwhile, further developed a thermal energy storage solution for industrial decarbonization, which works by using renewable electricity to heat blocks of carbon, which are stored in insulation to retain energy for long periods of time. The heat from those blocks can then be used to deliver electricity or heat to customers, at temperatures that can exceed 1,500 C. When Antora raised a $50 million Series A funding round last year, Bierman asked Kearns if he could buy out Medley’s team, and the researchers finally became co-workers.

    “Antora and Medley Thermal have a similar value prop: There’s low-cost electricity, and we want to connect that to the industrial sector,” Kearns explains. “But whereas Medley used renewables on an as-available basis, and then when the winds stop we went back to burning fossil fuel with a boiler, Antora has a thermal battery that takes in the electricity, converts it to heat, but also stores it as heat so even when the wind stops blowing we have a reservoir of heat that we can continue to pull from to make steam or power or whatever the facility needs. So, we can now further reduce energy costs by offsetting more fuel and offer a 100 percent clean energy solution.”

    United we scale

    Today, Kearns runs the project development arm of Antora.

    “There are other, much larger projects in the pipeline,” Kearns says. “The Jay Peak project is about 3 megawatts of power, but some of the ones we’re working on now are 30, 60 megawatt projects. Those are more industrial focused, and they’re located in places where we have a strong industrial base and an abundance of renewables, everywhere from Texas to Kansas to the Dakotas — that heart of the country that our team lovingly calls the Wind Belt.”

    Antora’s future projects will be with companies in the chemicals, mining, food and beverage, and oil and gas industries. Some of those projects are expected to come online as early as 2025.          

    The company’s scaling strategy is centered on the inexpensive production process for its batteries.

    “We constantly ask ourselves, ‘What is the best product we can make here?’” Bierman says. “We landed on a compact, containerized, modular system that gets shipped to sites and is easily integrated into industrial processes. It means we don’t have huge construction projects, timelines, and budget overruns. Instead, it’s all about scaling up the factory that builds these thermal batteries and just churning them out.”

    It was a winding journey for Kearns and Bierman, but they now believe they’re positioned to help huge companies become carbon-free while promoting the growth of the solar and wind industries.

    “The more I dig into this, the more shocked I am at how important a piece of the decarbonization puzzle this is today,” Bierman says. “The need has become super real since we first started talking about this in 2016. The economic opportunity has grown, but more importantly the awareness from industries that they need to decarbonize is totally different. Antora can help with that, so we’re scaling up as rapidly as possible to meet the demand we see in the market.” More

  • in

    Powering the future in Mongolia

    Nestled within the Tuul River valley and embraced by the southern Khentii Mountain Range, Ulaanbaatar (UB), Mongolia’s largest city, presents itself as an arena where nature’s forces wage an unrelenting battle against human resilience. The capital city is an icy crucible, with bone-chilling winters that plummet temperatures to an astonishing -40 degrees Fahrenheit (-40 degrees Celsius). Mongolia, often hailed with the celestial moniker of “The Land of the Eternal Blue Sky,” paradoxically succumbs to a veil of pollution and energy struggles during the winter months, obscuring the true shade of the cherished vista.

    To understand the root of these issues, MIT students from classes 22.S094 (Climate and Sustainability Systems: Decarbonizing Ulaanbaatar at Scale) and 21A.S01 (Anthro-Engineering: Decarbonization at the Million-Person Scale) visited Mongolia to conduct on-site surveys, diving into the diverse tapestry of local life as they gleaned insight from various stakeholder groups. Setting foot on Mongolian soil on a crisp day in January, they wasted no time in shaking off the weariness of their arduous 17-hour flight, promptly embarking on a waiting bus. As they traversed the vast expanse of the countryside, their eyes were captivated by snow-laden terrain.

    That is, until a disconcerting sight unfolded — thick smog, akin to ethereal pillars, permeated the cityscape ahead. These imposing plumes emanated from the colossal smokestacks of Ulaanbaatar’s coal-fired power plants, steadfastly churning electricity and heat to fuel Mongolia’s central and district energy systems. Over 93 percent of the nation’s energy comes from coal-fired power plants, where the most considerable load is caused by household consumption. Nevertheless, with nearly half of Ulaanbaatar’s population disconnected from the central heating networks, one of Mongolia’s most significant sources of pollution comes from coal-burning stoves in the residential settlements known as the ger districts. Over the past three decades, since the democratic revolution in 1990, Mongolians have grappled with escalating concerns surrounding energy provision, accessibility, and sustainability.

    Engineers who think like anthropologists

    “We find ourselves compelled to venture on-site, engaging in direct conversations with the locals, and immersing ourselves in the fabric of daily life to uncover what we don’t know,” emphasized Michael Short, professor in MIT’s Department of Nuclear Science and Engineering and faculty lead of MIT’s NEET Climate and Sustainability Systems thread, shortly before heading to Mongolia.

    The Ulaanbaatar Project sprang from a multiyear collaboration between MIT and the National University of Mongolia (NUM). Shedding light on the matter, Professor Munkhbat Byambajav of the Department of Chemical and Biological Engineering at NUM underscored the paramount importance of mitigating environmental pollution at an economic scale to alleviate the heavy burden borne by the people.

    Class 22.S094 is offered through MIT’s New Engineering Education Transformation (NEET) program, which allows students with multidisciplinary interests to collaborate across departments within four different subject areas, or threads. In this capstone project, students consider ways to decarbonize a city like Ulaanbaatar, transitioning from burning coal briquettes to a more sustainable, energy-efficient solution, given several parameters and constraints set by the local context.

    One of the ideas students have recently explored is a thermal battery made with molten salt that can store enough energy to heat a ger for up to 12 hours with added insulation for cooling curve regulation. The Mongolian ger, meaning home, is a dome-like portable dwelling covered in felt and canvas, held together by ropes traditionally crafted of animal hair or wool. Over several semesters, students have been testing a version of their proposed idea on campus, working with a prototype that weighs around 35 pounds.

    Nathan Melenbrink, the lead instructor of NEET’s Climate and Sustainability Systems (CSS) thread, believes that the complexity of the Ulaanbaatar capstone project allows students to reject the one-way solution approach and instead consider challenges with a nonprescriptive mindset. The uniqueness of the CSS thread is that students are asked to build on the previous findings from the past cohort and iterate on their designs each year. This workflow has allowed the project to mature and advance in ways that may not be feasible within a semester schedule. When asked how the recent trip impacted the ongoing research back on campus, Melenbrink states, “In light of the recent trip to Mongolia, students are beginning to see the impact of cultural immersion and social awareness leveraging the technical scope and rigor of their work.”

    Course 21A.S01, taught by Professor Manduhai Buyandelger of the MIT Anthropology Section, proved instrumental in deepening students’ understanding of the intricate dynamics at play. She asks, “The prototype works in the lab, but does it work in real life once you factor in the challenges in the larger structures of delivery, production, and implementation in Mongolia?”

    This recognition of the social dimensions of engineering permeated the early stages of the UB project, engaging all participants, including students from MIT and NUM, professionals residing in Mongolia, and local nongovernmental organizations, fostering what Buyandelger aptly describes as “a collaboration on multiple scales: trans-disciplinary and transcontinental.” Lauren Bonilla, co-lecturer for the anthropology course, was crucial in devising the first onsite trip to Mongolia. Drawing upon her extensive ethnographic research in Mongolia that spans decades, Bonilla remarks, “To me, engineering is a highly social discipline.” She further stresses how anthro-engineering elevates the social dimensions of engineering by critically questioning the framing of problems and solutions, stating, “It draws on anthropological insights and methods, like ethnography, to bring a human face to the users of a technology and adds complexity and nuance to the social constraints that limit designs.”

    Making of khorkhog

    Amidst the frigid atmosphere, a traditional Mongolian ger stands in front of the Nuclear Science Laboratory at the National University of Mongolia, emitting warm steam from its roof. The faculty and students of NUM organize a welcoming event inside the ger, inviting everyone to partake in a khorkhog cookout. Earlier that week, a remark from the Mongolian energy representative stood out during one of the presentations: “We need powerful heat. Solar is not enough, and electricity is not enough. Mongolians need fire,” he had emphasized.

    Indeed, the culinary delight known as khorkhog demands the relentless embrace of scorching flames. The process involves a large metal jug, stones, fire, and lamb. With skillful precision, the volunteer chef places the fire-heated stones and large pieces of lamb into the cooking container, triggering a cascade of steam that fills the ger, accompanied by the sounds of sizzling and hissing. Everyone waits patiently as the cook carefully inspects the dish, keenly listening for signs of readiness. And when the time comes, a feast is shared among all, complemented by steam-cooked potatoes, freshly sliced onions, and vegetables. In this moment, the presence of fire symbolizes a profound connection with the heart of Mongolian culture, evoking a deep resonance among the gathered crowd as they partake in this cherished staple meal.

    The distance between two points

    Familiar faces form a grid on the computer screen as the standing meeting between the students in Massachusetts and Ulaanbaatar begins. Sharing the morning (evening in Mongolia) for updates has been a critical effort by both sides to stay engaged and make decisions together. NEET CSS students in Cambridge proceeded to share their latest findings.

    Lucy Nester, a nuclear science and engineering major, has been diligently working on developing a high-efficiency electrical heating solution for individual consumers. Her primary focus is leveraging the discounted electricity rates available in the ger districts and utilize existing infrastructure. Recognizing the importance of maximum flexibility in heating the brick, Nester emphasizes the “no one-size-fits-all” solution. She shares the results of her test trials, which involve both inductive and resistive heating methods, outlining the advantages and disadvantages of each approach. Despite her limited experience in electrical engineering and circuit building, Nester has impressively overcome the steep learning curve. She enthusiastically describes her UB trip as “one of the most remarkable experiences I’ve had during my time at MIT.”

    Darshdeep Grewal, a dedicated materials science and engineering major with a strong passion for data science and computation, has been diligently conducting research on convection heating using COMSOL Multiphysics. In his investigation, Grewal explores the correlation between air temperature and heating, investigates the impact of convecting air arrangement on the heating process, and examines the conditions that may contribute to overheating. Leveraging his expertise in computational workflows, Grewal presents an impressive collection of heatmap simulations derived from the extensive data accumulated by his team throughout the project. Recognizing the immense value of these simulations in modeling complex scenarios, he highlights the importance of running experiments concurrently with simulations to ensure accurate calibration of results, stating, “It’s important to stay rooted in reality.”

    Arina Khotimsky, another materials science and engineering major, has actively engaged in NEET’s Climate and Sustainability Systems thread since her sophomore year. Balancing the demands of her final semester at MIT and the upcoming review of 22.S094, Khotimsky reveals how she has seamlessly integrated her project involvement into her energy studies minor. Reflecting on her journey, she remarks, “Working on the Ulaanbaatar project has taught me the significance of taking local context into account while suggesting solutions as an engineer.” Khotimsky has been tirelessly iterating and refining the insulation box prototype, which holds the thermal battery and controls the rate at which the battery releases heat. In addition, the on-site observations have unveiled another design challenge — ensuring the insulation box functions as a secure and dependable means of transportation. 

    To “engineer” means to contrive through one’s deliberate use of skills. What confronted the UB Project team on site was not the limitations of skill or technology, but the real-world constraints often amiss in the early equation: the people and their everyday lives. With over 6,195 miles of distance between the two groups, it takes more than just dedication to make a collaboration blossom. That may be the desire for a positive impact. Moreover, it may be the goal of cultivating a healthier relationship with energy that spans a million-person scale. No matter where you are, there is no one solution to the complex story of energy. This progressive realization brings the two teams together every two weeks in virtual space, bridging the distance between the two points.  More

  • in

    Flow batteries for grid-scale energy storage

    In the coming decades, renewable energy sources such as solar and wind will increasingly dominate the conventional power grid. Because those sources only generate electricity when it’s sunny or windy, ensuring a reliable grid — one that can deliver power 24/7 — requires some means of storing electricity when supplies are abundant and delivering it later when they’re not. And because there can be hours and even days with no wind, for example, some energy storage devices must be able to store a large amount of electricity for a long time.

    A promising technology for performing that task is the flow battery, an electrochemical device that can store hundreds of megawatt-hours of energy — enough to keep thousands of homes running for many hours on a single charge. Flow batteries have the potential for long lifetimes and low costs in part due to their unusual design. In the everyday batteries used in phones and electric vehicles, the materials that store the electric charge are solid coatings on the electrodes. “A flow battery takes those solid-state charge-storage materials, dissolves them in electrolyte solutions, and then pumps the solutions through the electrodes,” says Fikile Brushett, an associate professor of chemical engineering at MIT. That design offers many benefits and poses a few challenges.

    Flow batteries: Design and operation

    A flow battery contains two substances that undergo electrochemical reactions in which electrons are transferred from one to the other. When the battery is being charged, the transfer of electrons forces the two substances into a state that’s “less energetically favorable” as it stores extra energy. (Think of a ball being pushed up to the top of a hill.) When the battery is being discharged, the transfer of electrons shifts the substances into a more energetically favorable state as the stored energy is released. (The ball is set free and allowed to roll down the hill.)

    At the core of a flow battery are two large tanks that hold liquid electrolytes, one positive and the other negative. Each electrolyte contains dissolved “active species” — atoms or molecules that will electrochemically react to release or store electrons. During charging, one species is “oxidized” (releases electrons), and the other is “reduced” (gains electrons); during discharging, they swap roles. Pumps are used to circulate the two electrolytes through separate electrodes, each made of a porous material that provides abundant surfaces on which the active species can react. A thin membrane between the adjacent electrodes keeps the two electrolytes from coming into direct contact and possibly reacting, which would release heat and waste energy that could otherwise be used on the grid.

    When the battery is being discharged, active species on the negative side oxidize, releasing electrons that flow through an external circuit to the positive side, causing the species there to be reduced. The flow of those electrons through the external circuit can power the grid. In addition to the movement of the electrons, “supporting” ions — other charged species in the electrolyte — pass through the membrane to help complete the reaction and keep the system electrically neutral.

    Once all the species have reacted and the battery is fully discharged, the system can be recharged. In that process, electricity from wind turbines, solar farms, and other generating sources drives the reverse reactions. The active species on the positive side oxidize to release electrons back through the wires to the negative side, where they rejoin their original active species. The battery is now reset and ready to send out more electricity when it’s needed. Brushett adds, “The battery can be cycled in this way over and over again for years on end.”

    Benefits and challenges

    A major advantage of this system design is that where the energy is stored (the tanks) is separated from where the electrochemical reactions occur (the so-called reactor, which includes the porous electrodes and membrane). As a result, the capacity of the battery — how much energy it can store — and its power — the rate at which it can be charged and discharged — can be adjusted separately. “If I want to have more capacity, I can just make the tanks bigger,” explains Kara Rodby PhD ’22, a former member of Brushett’s lab and now a technical analyst at Volta Energy Technologies. “And if I want to increase its power, I can increase the size of the reactor.” That flexibility makes it possible to design a flow battery to suit a particular application and to modify it if needs change in the future.

    However, the electrolyte in a flow battery can degrade with time and use. While all batteries experience electrolyte degradation, flow batteries in particular suffer from a relatively faster form of degradation called “crossover.” The membrane is designed to allow small supporting ions to pass through and block the larger active species, but in reality, it isn’t perfectly selective. Some of the active species in one tank can sneak through (or “cross over”) and mix with the electrolyte in the other tank. The two active species may then chemically react, effectively discharging the battery. Even if they don’t, some of the active species is no longer in the first tank where it belongs, so the overall capacity of the battery is lower.

    Recovering capacity lost to crossover requires some sort of remediation — for example, replacing the electrolyte in one or both tanks or finding a way to reestablish the “oxidation states” of the active species in the two tanks. (Oxidation state is a number assigned to an atom or compound to tell if it has more or fewer electrons than it has when it’s in its neutral state.) Such remediation is more easily — and therefore more cost-effectively — executed in a flow battery because all the components are more easily accessed than they are in a conventional battery.

    The state of the art: Vanadium

    A critical factor in designing flow batteries is the selected chemistry. The two electrolytes can contain different chemicals, but today the most widely used setup has vanadium in different oxidation states on the two sides. That arrangement addresses the two major challenges with flow batteries.

    First, vanadium doesn’t degrade. “If you put 100 grams of vanadium into your battery and you come back in 100 years, you should be able to recover 100 grams of that vanadium — as long as the battery doesn’t have some sort of a physical leak,” says Brushett.

    And second, if some of the vanadium in one tank flows through the membrane to the other side, there is no permanent cross-contamination of the electrolytes, only a shift in the oxidation states, which is easily remediated by re-balancing the electrolyte volumes and restoring the oxidation state via a minor charge step. Most of today’s commercial systems include a pipe connecting the two vanadium tanks that automatically transfers a certain amount of electrolyte from one tank to the other when the two get out of balance.

    However, as the grid becomes increasingly dominated by renewables, more and more flow batteries will be needed to provide long-duration storage. Demand for vanadium will grow, and that will be a problem. “Vanadium is found around the world but in dilute amounts, and extracting it is difficult,” says Rodby. “So there are limited places — mostly in Russia, China, and South Africa — where it’s produced, and the supply chain isn’t reliable.” As a result, vanadium prices are both high and extremely volatile — an impediment to the broad deployment of the vanadium flow battery.

    Beyond vanadium

    The question then becomes: If not vanadium, then what? Researchers worldwide are trying to answer that question, and many are focusing on promising chemistries using materials that are more abundant and less expensive than vanadium. But it’s not that easy, notes Rodby. While other chemistries may offer lower initial capital costs, they may be more expensive to operate over time. They may require periodic servicing to rejuvenate one or both of their electrolytes. “You may even need to replace them, so you’re essentially incurring that initial (low) capital cost again and again,” says Rodby.

    Indeed, comparing the economics of different options is difficult because “there are so many dependent variables,” says Brushett. “A flow battery is an electrochemical system, which means that there are multiple components working together in order for the device to function. Because of that, if you are trying to improve a system — performance, cost, whatever — it’s very difficult because when you touch one thing, five other things change.”

    So how can we compare these new and emerging chemistries — in a meaningful way — with today’s vanadium systems? And how do we compare them with one another, so we know which ones are more promising and what the potential pitfalls are with each one? “Addressing those questions can help us decide where to focus our research and where to invest our research and development dollars now,” says Brushett.

    Techno-economic modeling as a guide

    A good way to understand and assess the economic viability of new and emerging energy technologies is using techno-economic modeling. With certain models, one can account for the capital cost of a defined system and — based on the system’s projected performance — the operating costs over time, generating a total cost discounted over the system’s lifetime. That result allows a potential purchaser to compare options on a “levelized cost of storage” basis.

    Using that approach, Rodby developed a framework for estimating the levelized cost for flow batteries. The framework includes a dynamic physical model of the battery that tracks its performance over time, including any changes in storage capacity. The calculated operating costs therefore cover all services required over decades of operation, including the remediation steps taken in response to species degradation and crossover.

    Analyzing all possible chemistries would be impossible, so the researchers focused on certain classes. First, they narrowed the options down to those in which the active species are dissolved in water. “Aqueous systems are furthest along and are most likely to be successful commercially,” says Rodby. Next, they limited their analyses to “asymmetric” chemistries; that is, setups that use different materials in the two tanks. (As Brushett explains, vanadium is unusual in that using the same “parent” material in both tanks is rarely feasible.) Finally, they divided the possibilities into two classes: species that have a finite lifetime and species that have an infinite lifetime; that is, ones that degrade over time and ones that don’t.

    Results from their analyses aren’t clear-cut; there isn’t a particular chemistry that leads the pack. But they do provide general guidelines for choosing and pursuing the different options.

    Finite-lifetime materials

    While vanadium is a single element, the finite-lifetime materials are typically organic molecules made up of multiple elements, among them carbon. One advantage of organic molecules is that they can be synthesized in a lab and at an industrial scale, and the structure can be altered to suit a specific function. For example, the molecule can be made more soluble, so more will be present in the electrolyte and the energy density of the system will be greater; or it can be made bigger so it won’t fit through the membrane and cross to the other side. Finally, organic molecules can be made from simple, abundant, low-cost elements, potentially even waste streams from other industries.

    Despite those attractive features, there are two concerns. First, organic molecules would probably need to be made in a chemical plant, and upgrading the low-cost precursors as needed may prove to be more expensive than desired. Second, these molecules are large chemical structures that aren’t always very stable, so they’re prone to degradation. “So along with crossover, you now have a new degradation mechanism that occurs over time,” says Rodby. “Moreover, you may figure out the degradation process and how to reverse it in one type of organic molecule, but the process may be totally different in the next molecule you work on, making the discovery and development of each new chemistry require significant effort.”

    Research is ongoing, but at present, Rodby and Brushett find it challenging to make the case for the finite-lifetime chemistries, mostly based on their capital costs. Citing studies that have estimated the manufacturing costs of these materials, Rodby believes that current options cannot be made at low enough costs to be economically viable. “They’re cheaper than vanadium, but not cheap enough,” says Rodby.

    The results send an important message to researchers designing new chemistries using organic molecules: Be sure to consider operating challenges early on. Rodby and Brushett note that it’s often not until way down the “innovation pipeline” that researchers start to address practical questions concerning the long-term operation of a promising-looking system. The MIT team recommends that understanding the potential decay mechanisms and how they might be cost-effectively reversed or remediated should be an upfront design criterion.

    Infinite-lifetime species

    The infinite-lifetime species include materials that — like vanadium — are not going to decay. The most likely candidates are other metals; for example, iron or manganese. “These are commodity-scale chemicals that will certainly be low cost,” says Rodby.

    Here, the researchers found that there’s a wider “design space” of feasible options that could compete with vanadium. But there are still challenges to be addressed. While these species don’t degrade, they may trigger side reactions when used in a battery. For example, many metals catalyze the formation of hydrogen, which reduces efficiency and adds another form of capacity loss. While there are ways to deal with the hydrogen-evolution problem, a sufficiently low-cost and effective solution for high rates of this side reaction is still needed.

    In addition, crossover is a still a problem requiring remediation steps. The researchers evaluated two methods of dealing with crossover in systems combining two types of infinite-lifetime species.

    The first is the “spectator strategy.” Here, both of the tanks contain both active species. Explains Brushett, “You have the same electrolyte mixture on both sides of the battery, but only one of the species is ever working and the other is a spectator.” As a result, crossover can be remediated in similar ways to those used in the vanadium flow battery. The drawback is that half of the active material in each tank is unavailable for storing charge, so it’s wasted. “You’ve essentially doubled your electrolyte cost on a per-unit energy basis,” says Rodby.

    The second method calls for making a membrane that is perfectly selective: It must let through only the supporting ion needed to maintain the electrical balance between the two sides. However, that approach increases cell resistance, hurting system efficiency. In addition, the membrane would need to be made of a special material — say, a ceramic composite — that would be extremely expensive based on current production methods and scales. Rodby notes that work on such membranes is under way, but the cost and performance metrics are “far off from where they’d need to be to make sense.”

    Time is of the essence

    The researchers stress the urgency of the climate change threat and the need to have grid-scale, long-duration storage systems at the ready. “There are many chemistries now being looked at,” says Rodby, “but we need to hone in on some solutions that will actually be able to compete with vanadium and can be deployed soon and operated over the long term.”

    The techno-economic framework is intended to help guide that process. It can calculate the levelized cost of storage for specific designs for comparison with vanadium systems and with one another. It can identify critical gaps in knowledge related to long-term operation or remediation, thereby identifying technology development or experimental investigations that should be prioritized. And it can help determine whether the trade-off between lower upfront costs and greater operating costs makes sense in these next-generation chemistries.

    The good news, notes Rodby, is that advances achieved in research on one type of flow battery chemistry can often be applied to others. “A lot of the principles learned with vanadium can be translated to other systems,” she says. She believes that the field has advanced not only in understanding but also in the ability to design experiments that address problems common to all flow batteries, thereby helping to prepare the technology for its important role of grid-scale storage in the future.

    This research was supported by the MIT Energy Initiative. Kara Rodby PhD ’22 was supported by an ExxonMobil-MIT Energy Fellowship in 2021-22.

    This article appears in the Winter 2023 issue of Energy Futures, the magazine of the MIT Energy Initiative. More