Next generation batteries that use new electrolyte materials could achieve far higher energy density than today’s lithium-ion batteries, without many of the safety concerns. But advanced batteries, such as those that use solid or almost-solid electrolytes, have been plagued by the formation of tiny spikes of lithium metal called dendrites that cause the batteries to lose efficiency and fail.

Exactly how those dendrites form is still up for debate. While the interface between the battery’s electrolyte and electrodes has been the focus of most research, another culprit is the boundary where two grains of electrolyte in a solid material meet. Researchers know these boundaries can seed dendrites within electrolytes, although the effects have been difficult to study.

Now researchers at MIT and the Technical University of Munich have uncovered why such boundaries can lead to dendrites: Hidden electrical imbalances across the boundaries affect how the electrolyte conducts electrical charges, which influences how the ions and electrons move through the material during battery operation. In a paper published today in Nature Nanotechnology, the researchers characterized the electrical and chemical behavior of the boundaries and showed that adjusting how the electrolyte is processed enhances the movement of ions while reducing electron leakage. This adjustment can increase critical current density by more than 300 percent, which could enable solid-state batteries that charge faster and last longer.

“Grain boundaries are like the weather: Everyone talks about it, but nobody does anything about it,” says senior author Harry Tuller, a professor in MIT’s Department of Materials Science and Engineering. “In this paper, we’ve decided to do something about grain boundaries, and by doing something we’ve shown improved performance and demonstrated the importance of grain boundaries more broadly.”

Joining Tuller on the paper are first author Hyunwon Chu PhD ’25; former MIT professor Jennifer Rupp, the Electrochemical Material Professor at the Technical University of Munich (TUM), who led the study; TUM researchers Waldemar Kaiser, Lukas Wolz, Fran Kurnia, Kun Joong Kim, David Egger, and Johanna Eichhorn; Thomas Defferriere PhD ’22; Willis O’Leary PhD ’24; and University of Antwerp researchers Proloy Nandi, Johan Verbeeck, Sara Bals, and Thomas Altantzis.

Investigating grain boundaries

Rupp’s research group, which moved from MIT to TUM during this research, has spent years studying the behavior of next-generation electrolyte materials. Electrolytes in solid-state batteries are made of many tiny crystals of material packed together.

“What we call a grain, like a grain of salt, is actually a single crystal, but it might only be on the order of 1 micron in size,” explains Tuller. “Under high temperature processes, the best materials essentially consolidate to be void or pore-free and can be nearly 100 percent dense, but each of those crystallites is separated from its neighbor by a grain boundary.”

Solid-state battery researchers have increasingly focused on grain boundaries as the source of the lithium metal dendrites that cause them to short circuit. It’s been suspected that grain boundaries have different chemical and electrical properties from the grains, which interact with the ions and electrons shuttling between electrodes during battery charging and discharging. However, the exact mechanisms by which the boundaries slowed the ions down, leaked electrons, and led to dendrites was unknown.

“Grain boundaries are like defects,” Tuller says. “The boundaries have a higher level of defects than in the grains themselves, and generally that means as carriers of charge approach the boundary, whether electrons or ions, there’s some kind of blockage to overcome.”

To better understand that interference, the researchers developed a model to explain how local electrical imbalances at grain boundaries change the movement of lithium ions and electronic charge carriers. They tested the model in a common solid electrolyte material called lithium lanthanum zirconate, or LLZO, using techniques including electron microscopy, machine learning modeling, and electrochemical impedance spectroscopy, which measures how easily a charge moves through a material.

They found the cores of the boundaries carry a local electrical charge, building up local electric fields that lead to enhanced ionic resistance while causing a build-up of electrons in the boundary region, where they can reduce lithium ions, leading to lithium metal dendrite formation.

“For the last 30 years, the world has been dominated by lithium-ion batteries, but there is a growing recognition that other battery types are needed for batteries used in a variety of uses,” Rupp explains. “This work gives us the fundamental understanding of the space charge interface at the grain boundary. If understood properly, we can come up with engineering concepts to increase cycle life, transference of ions over electrons at these interfaces, and ultimately a better battery.”

Better battery materials

The researchers used their observations to adjust the material processing conditions of the LLZO electrolyte material and minimize the negative charges at the boundaries, finding they could ease the movement of lithium ions and reduce the leakage of electrons.

The modifications allowed them to create an electrolyte that had a critical current density more than 300 percent higher than a baseline sample. Higher current density allows for faster charging and discharging. It should also delay short circuiting to extend the life of batteries.

“Fires are currently a huge issue in the battery industry,” Rupp says. “By showing how to engineer these space charges in a controlled way, which is new in the field, we can have a strong impact on safety. It’s a new way to turn up the notch and get these batteries to charge faster and last longer before they break.”

The findings, along with the researchers’ engineering work, present a roadmap for battery researchers to accelerate the development of high-performance, longer lasting solid-state batteries.

“We showed we can control the initiation of these dendrites to maximize solid state batteries’ high performance,” Chu says. “In this paper, we started with a theory for how these dendrites form, then we did the material characterization to support that theory, then we did the engineering to apply the findings and actually improve battery performance.”

The work was supported, in part, by the National Science Foundation and the U.S. Department of Homeland Security.

Lerna Ekmekcioglu, the McMillan-Stewart Professor of History, has been named head of the History Section, effective July 1. 

“Lerna is an exceptional scholar and a proven leader. I am confident that she will guide the unit with thoughtfulness, wisdom, and a deep commitment to its continued success. I very much look forward to working with her in the years ahead,” says Agustín Rayo, the Kenan Sahin Dean of the School of Humanities, Arts, and Social Sciences.

Ekmekcioglu, who joined the MIT faculty in 2011, is a historian of the modern Middle East, the Ottoman Empire, and Turkey, Armenian history, gender, feminism, genocide, and minority politics. She served as director of the Program in Women’s and Gender Studies from 2022 to 2025, where she remains an affiliated faculty member.

Ekmekciouglu succeeds Malick Ghachem, who was named head of the History Section on July 1, 2023. 

“As I begin this new role, my first priority is to sustain and expand the remarkable momentum already underway in the unit. It is truly an exciting moment to be head of History,” says Ekmekciouglu. “We have ambitious new initiatives, extraordinary faculty work, and — this is not a small thing — a group of colleagues who actually like and trust one another.”

She cites the History of Now, launched in 2025, as one of several exciting initiatives underway, adding that her role will be ensuring the section’s projects are sustainable, visible, and intellectually fruitful.

“The work ahead is both practical and intellectual: supporting faculty research and teaching, sustaining new initiatives, expanding public engagement, and demonstrating why historical inquiry is indispensable to MIT’s mission,” she says.

Ekmekcioglu’s first monograph, “Recovering Armenia: The Limits of Belonging in Post-Genocide Turkey” (Stanford University Press, 2016), explored the Armenian community in Turkey after the Armenian Genocide and the limits of minority belonging in the early Turkish Republic.

It won the Der Mugrdechian Society for Armenian Studies Outstanding Book Award.

Her forthcoming book, “Feminism in Armenian: Lives and Texts Through Empire, Genocide, and Diaspora,” co-authored with Melissa Bilal of the University of California at Los Angeles, continues her long-standing work on Armenian feminist thought, activism, and archives across empire, violence, and dispersion.

Ekmekcioglu is a 2016 recipient of the the James A. and Ruth Levitan Award for excellence in teaching. She also organizes the biannual McMillan-Stewart Lecture Series on women, gender, religion, politics, and law across the Middle East and North Africa.

Ekmekcioglu earned a BA from Boğaziçi University in Istanbul 2002 and a PhD from New York University in 2010.

On a Wednesday afternoon in April, a cohort of scholars from the School of Humanities, Arts, and Social Sciences (SHASS) gathered in MIT’s Lewis Music Library. 

This group of seven professors are the inaugural SHASS Faculty Fellows, a semester-long program launched this past spring. The faculty represent a variety of disciplines across the school. They met biweekly through the spring to connect over lunch and present updates on their respective research projects. 

At this particular meeting, associate professor of music Emily Richmond Pollock presented some of her work — a chapter about an opera festival in Sarasota, Florida — which, she says, started from “my own curiosity about how American institutions relate to opera’s traditions and practices.” 

After Pollock’s presentation, the group discussed and provided a sounding board for her work. It’s precisely the type of scholarly environment the SHASS Faculty Fellows program was designed to foster.

“The fellows program is a recognition of the fact that not only do we benefit from being in conversation with other scholars, but even more so when in conversation with scholars who do things differently than we do, who approach problems with different opening questions and methodologies,” says Anne McCants, the Ann F. Friedlaender Professor of History and Faculty Fellows Program Committee chair.

Along with committee member and literature professor Arthur Bahr, McCants serves as a kind of moderator during the discussions, asking pointed questions and interrogating participants’ assumptions.

“A small group of people coming from diverse scholarly backgrounds meeting regularly to share a meal and sustained conversation can have a truly outsized impact on their scholarship,” McCants adds.

Time to focus and connect

Faculty must apply to take part in the program, and are selected by the program committee. The program is administered by the MIT Human Insight Collaborative (MITHIC). 

Participants take advantage of opportunities to share and discuss ideas with students, too. Volha Charnysh, a Faculty Fellow and the Ford Career Development Associate Professor of Political Science in the Department of Political Science, presented research on the effects of large-scale humanitarian aid to the Burchard Scholars. The Burchard Scholars program connects faculty and promising MIT sophomores and juniors who have demonstrated excellence in some aspect of the humanities, arts, or social sciences.  

Projects can run the gamut. Participants might develop scholarly articles, develop book manuscripts, or dig deeper into existing research. 

“The Faculty Fellows Program has two primary aims: to enrich faculty members’ scholarly programs, and to foster collegial community within the school,” says Heather Paxson, associate dean for faculty in SHASS, the William R. Kenan, Jr. Professor of Anthropology, and MITHIC faculty co-lead. “Participants in the program gain a better sense of the breadth and depth of our school’s scholarly contributions, and some may forge lasting connections with colleagues they might not otherwise have gotten to know.” 

For Pollock, the fellows program this past spring was an opportunity to focus on her current research.

“I’m working on a book about a set of five opera festivals in the United States,” Pollock says of the project, “Opera on Uncommon Ground: Five American Festivals.” 

“These are annual, seasonal opera companies where rare repertoire is often performed alongside canonical works, in places that are outside of major cities, and performed in unusual spaces.” 

“I hope that anyone who loves opera will be able to read and enjoy my book,” she says, including “opera ‘superfans’” Pollock says she has in mind while writing.

Pollock says the program gave her the space she needed to continue her project. “This semester [in the program] has been wonderful so I could get back to drafting and really concentrate on a book I am excited to write.”

“I am so inspired each week when we meet”

Faculty Fellow Richard Nielsen, associate professor of political science, faculty director of the MIT-MENA Program, and a Security Studies Program affiliate, is hard at work on his project, “Fighting War with Divine Intervention,” a book about how combatants’ beliefs affect wars. Using material from a diverse set of cases — the Islamic State, the Confederate States of America, and the current U.S. engagement with Iran — he wants to understand when claims about divine intervention motivate fighters and citizens to fight harder and longer for victory, even when the state of the battlefield strongly suggests they have lost already. 

“We understand a lot about how religion might shape the conditions for war and peace, but religion matters during wars, too, and we understand surprisingly little about how religious claims affect leaders and fighters in combat,” he says. 

Nielsen lauds the collegial atmosphere available in the fellows program, citing the importance of engagement with scholars outside his research area as a significant draw. “The best part has actually been the engagement with a diverse set of fellows,” he notes, “pursuing a dizzying variety of humanist and social science projects. I am so inspired each week we meet, and every single project has me exclaiming ‘I wish I was writing this!’”

“It adds a regular ongoing conversation with scholars not like yourself who will push you, likely accidentally, in unexpected directions,” McCants says of the fellows’ meetings. Conferring with other participants about their projects, meanwhile, helps Nielsen “return to my research with fresh eyes and enthusiasm,” he says.

Pollock appreciates the camaraderie available as a program participant. “I value my colleagues so highly — the other fellows and mentors are people I really admire and respect — and it’s been fun to trade work and get to read work in progress far outside my field,” she says. 

Twelve professors have been named SHASS Faculty Fellows for the 2026-27 academic year, with six taking part in the fall and another six in the spring. 

The inaugural group of fellows included: 

• Héctor Beltrán, the Class of 1957 Career Development Associate Professor of Anthropology; 
• Volha Charnysh, the Ford Career Development Associate Professor of Political Science; 
• Kevin Dorst, associate professor of philosophy;
• Richard Nielsen, associate professor of political science;
• Emily Richmond Pollock, associate professor of music; 
• Jessica Ruffin, assistant professor of literature; and 
• Robin Scheffler, associate professor of science, technology, and society.

Applications for the next cohort of fellows will open this fall.

In the study of bacteria, a longstanding dogma held that two molecular machines — RNA polymerase, which leads the way in transcribing DNA into RNA, and ribosomes, which bring up the rear translating RNA into proteins — worked so closely in tandem that they were effectively attached. 

This close coupling of transcription and translation in bacteria was thought to be fundamental to gene expression in part because the trailing ribosome could shield nascent gene products from an effective and omnipresent quality-control protein called Rho. 

In bacteria that exhibit something called runaway transcription, however, the polymerase instead speeds ahead, unhitched from its protective ribosome. Inexplicably, however, in bacteria that exhibit this runaway transcription, such as Bacillus subtilis, Rho targeted primarily noncoding, useless RNA products. 

New research from the Department of Biology reveals that the secret to Rho’s quality-control specificity lies in the sequence composition of nucleotide bases that make up coding strands of DNA. 

“We started with a hypothesis that Rho was regulated by sequence, but the fact that the sequence alone was enough to protect any gene in the entire B. subtilis genome from Rho was really surprising,” says Julia Dierksheide PhD ’26, a graduate student in the Li Lab and first author of a paper recently published in Nature Microbiology. “That’s a really diverse range of sequences — what sequence feature is shared by every single gene in the genome?” 

Barricading with bias

Rho serves as a termination factor, meaning that it is a crucial mechanism for preventing bacteria from wasting precious resources by making RNA transcripts that serve no purpose. 

All the information a bacterial cell needs is encoded in its DNA, which is made up of two strands of nucleic acids. These strands twist together to form a double helix, with genetic information codified in pairs of bases: purines guanine and adenine are matched with pyrimidines cytosine and thymine, respectively. Any sequence that gives rise to RNA transcripts is stored in complement to a parallel, noncoding strand, meaning that a large portion of genetic material is transcriptionally useless. 

Coding DNA strands in certain bacteria were known to be significantly higher in purines guanine and adenine compared to the rest of the bacterial genome. The researchers found that this purine bias alone shields productive mRNA transcripts from Rho-mediated termination.

“I love having a big, complicated dataset and trying to reduce that to biological meaning,” Dierksheide says. “It seems like Rho itself has been broadly shaping the evolution of the B. subtilis genome to create these sequence composition biases.” 

Bacterial species that, over generations, have lost Rho no longer exhibit this strong purine bias. 

Rho also serves as a regulatory factor in bacteria becoming motile, forming biofilms, or sporulating, all of which are critical for biology and survival. The purine bias could also provide a layer of protection against the insertion of foreign DNA, for example, when a viral bacteriophage infects bacteria.

“Bacteria exist as single cells, so everything that they do, they have to do through gene expression,” Dierksheide says. “Understanding the fundamental details about how gene expression works, how a cell encodes all the information it needs to survive in the nucleotide sequence of the genome, is really exciting.”

Future directions

Although the exact mechanism underlying Rho’s specificity remains unclear, these results crack an underlying code in the composition of bacterial genomes. 

Dierksheide said she hoped to perform a similar screen to characterize Rho’s specificity in Escherichia coli, which diverged from B. subtilis on the evolutionary tree an estimated 2 billion years ago and still exhibits coupled transcription-translation, where the transcribing RNA polymerase is closely followed by a translating ribosome.

The high sequence specificity of B. subtilis Rho is crucial for the protection of its runaway RNA polymerase, in which that molecular machine speeds ahead of the ribosome. A systematic comparison to E. coli Rho could help reveal how this heightened stringency arose. 

This information will be critical for engineering diverse bacterial species for applications including the production of therapeutic agents. Other bacterial species, such as B. subtilis, may be better models for this process because they have abundant secretion pathways, according to Dierksheide, making it much easier to produce and isolate proteins in large quantities. 

“Our findings reveal an important criterion for successful sequence design that must be considered in expression engineering,” says associate department head, associate professor of biology, and Howard Hughes Medical Institute investigator Gene-Wei Li, the lead author of the study. “There are so many cryptic messages in the genome, like the purine bias, and we are just beginning to be able to decipher what they mean.”