Tech
Simple formula could guide the design of faster-charging, longer-lasting batteries
At the heart of all lithium-ion batteries is a simple reaction: Lithium ions dissolved in an electrolyte solution “intercalate” or insert themselves into a solid electrode during battery discharge. When they de-intercalate and return to the electrolyte, the battery charges.
This process happens thousands of times throughout the life of a battery. The amount of power that the battery can generate, and how quickly it can charge, depend on how fast this reaction happens. However, little is known about the exact mechanism of this reaction, or the factors that control its rate.
In a study appearing in Science, MIT researchers have measured lithium intercalation rates in a variety of different battery materials and used that data to develop a new model of how the reaction is controlled. Their model suggests that lithium intercalation is governed by a process known as coupled ion-electron transfer, in which an electron is transferred to the electrode along with a lithium ion.
Insights gleaned from this model could guide the design of more powerful and faster charging lithium-ion batteries, the researchers say.
“What we hope is enabled by this work is to get the reactions to be faster and more controlled, which can speed up charging and discharging,” says Martin Bazant, the Chevron Professor of Chemical Engineering and a professor of mathematics at MIT.
The new model may also help scientists understand why tweaking electrodes and electrolytes in certain ways leads to increased energy, power, and battery life—a process that has mainly been done by trial and error.
“This is one of these papers where now we began to unify the observations of reaction rates that we see with different materials and interfaces, in one theory of coupled electron and ion transfer for intercalation, building up previous work on reaction rates,” says Yang Shao-Horn, the J.R. East Professor of Engineering at MIT and a professor of mechanical engineering, materials science and engineering, and chemistry.
Shao-Horn and Bazant are the senior authors of the paper. The paper’s lead authors are Yirui Zhang Ph.D., who is now an assistant professor at Rice University; Dimitrios Fraggedakis Ph.D., who is now an assistant professor at Princeton University; Tao Gao, a former MIT postdoc who is now an assistant professor at the University of Utah; and MIT graduate student Shakul Pathak.
Modeling lithium flow
For many decades, scientists have hypothesized that the rate of lithium intercalation at a lithium-ion battery electrode is determined by how quickly lithium ions can diffuse from the electrolyte into the electrode. This reaction, they believed, was governed by a model known as the Butler-Volmer equation, originally developed almost a century ago to describe the rate of charge transfer during an electrochemical reaction.
However, when researchers have tried to measure lithium intercalation rates, the measurements they obtained were not always consistent with the rates predicted by the Butler-Volmer equation.
Furthermore, obtaining consistent measurements across labs has been difficult, with different research teams reporting measurements for the same reaction that varied by a factor of up to 1 billion.
In the new study, the MIT team measured lithium intercalation rates using an electrochemical technique that involves applying repeated, short bursts of voltage to an electrode.
They generated these measurements for more than 50 combinations of electrolytes and electrodes, including lithium nickel manganese cobalt oxide, which is commonly used in electric vehicle batteries, and lithium cobalt oxide, which is found in the batteries that power most cell phones, laptops, and other portable electronics.
For these materials, the measured rates are much lower than has previously been reported, and they do not correspond to what would be predicted by the traditional Butler-Volmer model.
The researchers used the data to come up with an alternative theory of how lithium intercalation occurs at the surface of an electrode. This theory is based on the assumption that in order for a lithium ion to enter an electrode, an electron from the electrolyte solution must be transferred to the electrode at the same time.
“The electrochemical step is not lithium insertion, which you might think is the main thing, but it’s actually electron transfer to reduce the solid material that is hosting the lithium,” Bazant says. “Lithium is intercalated at the same time that the electron is transferred, and they facilitate one another.”
This coupled-electron ion transfer (CIET) lowers the energy barrier that must be overcome for the intercalation reaction to occur, making it more likely to happen. The mathematical framework of CIET allowed the researchers to make reaction rate predictions, which were validated by their experiments and substantially different from those made by the Butler-Volmer model.
Faster charging
In this study, the researchers also showed that they could tune intercalation rates by changing the composition of the electrolyte. For example, swapping in different anions can lower the amount of energy needed to transfer the lithium and electron, making the process more efficient.
“Tuning the intercalation kinetics by changing electrolytes offers great opportunities to enhance the reaction rates, alter electrode designs, and therefore enhance the battery power and energy,” Shao-Horn says.
Shao-Horn’s lab and their collaborators have been using automated experiments to make and test thousands of different electrolytes, which are used to develop machine-learning models to predict electrolytes with enhanced functions.
The findings could also help researchers to design batteries that would charge faster, by speeding up the lithium intercalation reaction. Another goal is reducing the side reactions that can cause battery degradation when electrons are picked off the electrode and dissolve into the electrolyte.
“If you want to do that rationally, not just by trial and error, you need some kind of theoretical framework to know what are the important material parameters that you can play with,” Bazant says. “That’s what this paper tries to provide.”
More information:
Yirui Zhang et al, Lithium-ion intercalation by coupled ion-electron transfer, Science (2025). DOI: 10.1126/science.adq2541. www.science.org/doi/10.1126/science.adq2541
This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.
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April might be springtime in the northern hemisphere, but some of the best streaming services seem to think it’s the perfect time for a dry run of spooky season. How else to explain the arrival of some exquisitely dark slices of horror, like 28 Days Later: The Bone Temple arriving on Netflix, Weapons coming to Prime Video, or Shelby Oaks landing on Hulu? If you prefer your off-season Halloween viewing to be in the vein of campy B movies rather than serious scares though, horror specialist Shudder has you covered with Deathstalker, a gloriously cheesy reboot of a near-forgotten ’80s series.
Reality is often scarier than fiction though, as shown by Louis Theroux’s Inside the Manosphere—his first documentary film with Netflix, exploring the dark side of social media and the world of toxic male influencers. (Be sure to read our interview with the filmmaker.) And if the thought of that leaves you wanting something a bit more wholesome to watch, thankfully Zootopia 2 has popped up on Disney+—and there’s even a rabbit in that, for some appropriately springtime imagery.
Here are WIRED’s picks of the best movies to watch right now.
28 Years Later: The Bone Temple
The fourth film in the long-running postapocalyptic horror series switches focus from rampaging rage zombies to a more dangerous threat: humans. OK, OK, “people are the real monsters” isn’t a hot take for the genre, but The Bone Temple offers a unique twist, with 28 Years Later survivor Spike (Alfie Williams) trapped in the company of a murderous gang led by deranged satanist “Sir Lord” Jimmy Crystal (Sinners’ Jack O’Connell). The villain is modeled on disgraced British TV presenter Jimmy Savile, whose sexual abuse crimes hadn’t been revealed by the time of the initial outbreak in 28 Days Later, adding a dash of real-world terror.
As the group stalks what remains of the English countryside, Spike’s only hope might be Dr. Ian Kelson (Ralph Fiennes), whose experiments on curing alpha zombie Samson (Chi Lewis-Parry) might hold humanity’s last hope. Although best watched back to back with its predecessor for the full, horrifying picture, director Nia DaCosta’s chapter stands on its own—and earns bonus points for one of the best uses of Iron Maiden’s “Number of the Beast” in film history.
Louis Theroux: Inside the Manosphere
It’s the silence that does the trick; British documentarian Louis Theroux always knows when not to speak and instead let his subject expose themselves for the world to see. It’s a masterful technique whether Theroux is investigating the Westboro Baptist Church or UFO conspiracy theorists, but it is rarely put to better use than in his latest outing: exploring the online “manosphere” subculture of self-appointed “alphas” offering toxic advice on how to be a “real man.” Speaking with key figures in the loosely defined movement, Theroux’s mild-mannered approach often leaves them to do most of the talking, exposing shockingly misogynistic and extremist views. Even more distressing? The quiet revelation that for many of them their performative masculinity is all just one big grift, and how they rationalize the harm they cause in pursuit of a payout. Depressing but compelling viewing—not all men, but definitely all of these men.
Crime 101
Jewel thief Mike (Chris Hemsworth) is the best in the business, a meticulous planner who pulls off his heists without leaving a shred of evidence—much to the consternation of LAPD detective Lou Lubesnick (Mark Ruffalo), who doesn’t even know exactly who he’s hunting for a string of thefts. Elsewhere in the City of Angels, Sharon (Halle Berry) is an underappreciated VP at an insurance firm, frustrated at being passed over for promotion for years. She’s the perfect insider to help Mike orchestrate an elaborate $11 million diamond heist. But as Lou uncovers evidence connecting to Mike’s past, and the chaotic, violent biker Ormon (Barry Keoghan) aims to take the score for himself, even the most masterful planning can’t prevent everything spiraling dangerously out of control.
Kevin Weil, OpenAI’s former chief product officer who was recently tapped to build a new AI workspace for scientists, Prism, is leaving the company, WIRED has confirmed. Weil was previously an early executive leading product at Instagram.
OpenAI is also sunsetting Prism, which the company launched as a web app in January this year to give scientists a better way to work with AI. The company is folding the roughly 10-person team behind it into Thibault Sottiaux’s Codex team. An OpenAI spokesperson confirmed the changes, and tells WIRED this is part of the company’s effort to unify its business and product strategy. OpenAI has broader ambitions to turn Codex, its AI coding application, into an “everything app.”
Weil, who joined OpenAI in June 2024, announced last September that he would be starting a new initiative inside of the company called “OpenAI for Science.” Now, OpenAI is dispersing those employees throughout the company’s product, research, and infrastructure teams. An OpenAI spokesperson reiterated the company’s commitment to accelerating scientific discovery, and says it’s one of the clearest ways AI can benefit humanity.
OpenAI is currently trying to refocus the company around a few key areas, such as enterprise offerings and coding. Last month, OpenAI’s CEO of AGI deployment Fidji Simo told staff that the company needs to simplify its product offerings. The push to divert resources to more consequential efforts resulted in OpenAI discontinuing its Sora video-generation app.
This is a developing story. Please check back for updates.
Sam Altman’s iris-scanning, humanity-verifying World project announced at an event in San Francisco on Friday that Tinder users around the globe can now put a digital badge on their profiles signaling to potential suitors that they’re a real human, provided they’ve already stared into one of World’s glossy white Orbs and allowed their eyes to be scanned. The announcement follows a pilot project for Tinder verification that World previously conducted in Japan.
The global Tinder expansion is one of the biggest tests yet for World, and the company’s bet that everyday consumers will be willing to sign up for biometric verification services to use internet applications. Founded in 2019 by Altman and Alex Blania, the World project was designed for a future where the internet is overrun with highly capable AI agents that make it incredibly difficult, if not impossible, to tell who is really human. As companies like OpenAI—where Altman is CEO—and Anthropic push AI agents into the mainstream, the problem World was built to solve feels increasingly urgent.
But World has struggled to achieve mainstream adoption, and it has encountered resistance from governments around the globe that have probed the company over suspected violations of data protection laws. The company says 18 million people have now been verified with an Orb, up from 12 million last year.
In addition to the Tinder global expansion, Tools for Humanity, the company behind World, announced a number of other consumer and enterprise partnerships on Friday at its Lift Off event in San Francisco. The startup says Tinder users who verify with their World ID will receive five free “boosts,” typically a paid feature that increases the number of users who see a profile by up to 10 times for 30 minutes. The videoconferencing platform Zoom also says that users can now require other participants to verify their identity with World before joining a call. Docusign, the contract signing software, will allow users to require World’s identity verification technology.
Tiago Sada, Tools for Humanity’s chief product officer, tells WIRED the company sees major platform partnerships as key to helping World become a mainstream identity-verification technology. Sada said he’s especially interested in working with social media companies in the future, and was encouraged to see that Reddit has started testing World as a solution to help users distinguish bots from real people.
World is also launching a tool called Concert Kit, which lets artists reserve concert tickets for verified humans, a pitch aimed squarely at the bot-driven scalping problem that critics say has plagued sites like TicketMaster. World will test the feature on the upcoming Bruno Mars World Tour featuring Anderson .Paak, who is scheduled to play a verified-humans-only show under his alias DJ Pee .Wee in San Francisco on Friday night.
No new hardware announcements or updates were made at Friday’s event. World first launched the iris-scanning Orb back in 2023, alongside a mobile app that contains “mini apps” for different verification and blockchain-related programs. After a person scans their eyeball with one of World’s Orbs, the startup creates a unique cryptographic key for each person—their World ID. This creates a private, decentralized way to verify people online, without requiring them to upload their government ID all over the internet.
The project was initially called Worldcoin, and in the early days the startup offered people free cryptocurrency to scan their irises. World still offers a cryptocurrency token and a wallet for digital currencies, but dropped the “coin” from its name in 2024 and has since shifted its focus to identity verification for the AI era. Jess Montejano, a spokesperson for Tools for Humanity, says the company still offers crypto as an incentive when new users sign up, but has also expanded its offerings to include Netflix and Apple TV subscription trials.
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