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University of Michigan uses recycled Kevlar fiber to solve lithium-sulfur battery life cycle issues

(Credit: University of Michigan)

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3 years ago

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The University of Michigan Chemical Sciences and Engineering team, led by Professor Nicholas Kotov, has developed a “new biologically inspired battery membrane” with recycled Kevlar fibers that could quintuple electric vehicle ranges and have a lifespan of 1,000 cycles.

The Ann Arbor, Michigan research facility is one of the best in the world, and Kotov, whose research focuses on the development of biomimetic nanocomposites, the self-assembly of nanoparticles, and chiral nanostructures, has worked to change the narrative on lithium-sulfur cells. “There are a number of reports claiming several hundred cycles for lithium-sulfur batteries, but it is achieved at the expense of other parameters—capacity, charging rate, resilience, and safety,” Kotov said in a press release from the University. “The challenge nowadays is to make a battery that increases the cycling rate from the former 10 cycles to hundreds of cycles and satisfies multiple other requirements including cost.”

Lithium-sulfur batteries can enable five times the capacity of standard lithium-ion cells, which are used in electric vehicles. However, as Professor Kotov mentioned in his quote, the lifespan is significantly decreased due to chemical reactions between molecules. The most common reason for reduced life cycles in lithium-sulfur batteries is dendrites, which are appendages that are designed to receive communications from other cells. These can pierce the membrane of cells, reducing the life span and thus the life cycle of a battery cell.

Another problem is polysulfides, or small molecules of lithium and sulfur, can form and flow to the lithium. They bond and cause blockages, reducing the effectiveness of the membrane. “The membrane is needed to allow lithium ions to flow from the lithium to the sulfur and back—and to block the lithium and sulfur particles, known as lithium polysulfides.”

However, Kevlar, the same material used in bulletproof vests, can stop dendrites from penetrating the membrane using dense aramid fibers found in the material. The cells that Kotov and his team developed use recycled Kevlar fibers. The Kevlar “can enable lithium-sulfur batteries to overcome their Achilles heel of cycle life,” caused by the two previously mentioned reactions between molecules.

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An example of the Kevlar system is shown in the images below, as the typical Celgard membrane on the left allows lithium polysulfides to flow through. The Kevlar membrane (right) blocked the polysulfides from traveling through.

“Just half an hour on, the Celgard membrane (left) leaks lithium polysulfides. However, the U-M membrane (right) completely blocks the lithium polysulfides 96 hours later. Image credit: Ahmet Emre, Kotov Lab.” Credit: University of Michigan

“Achieving record levels for multiple parameters for multiple materials properties is what is needed now for car batteries,” Kotov stated. Kotov added that the design of the lithium-sulfur batteries is “nearly perfect” due to its capacity and efficiency reaching theoretical limits. It can also behave more resiliently than lithium-ion cells in warm and cold weather climates, which both have effects on range and efficiency. However, fast charging could reduce the number of lifespans, Kotov added.

Lithium-sulfur batteries could be a good alternative as sulfur is more readily available and abundant than cobalt, which is controversial due to its mining practices. However, automakers like Tesla are reducing cobalt in their batteries vying for other metals, like nickel, instead. Sulfur’s low lifespan and instability, as it changes in size by 78 percent during charging, reduced the possibility of automakers using it in the past, The Independent reported.

The research was funded by the National Science Foundation and the Department of Defense.

I’d love to hear from you! If you have any comments, concerns, or questions, please email me at joey@teslarati.com. You can also reach me on Twitter @KlenderJoey, or if you have news tips, you can email us at tips@teslarati.com.

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Joey has been a journalist covering electric mobility at TESLARATI since August 2019. In his spare time, Joey is playing golf, watching MMA, or cheering on any of his favorite sports teams, including the Baltimore Ravens and Orioles, Miami Heat, Washington Capitals, and Penn State Nittany Lions. You can get in touch with joey at joey@teslarati.com. He is also on X @KlenderJoey. If you're looking for great Tesla accessories, check out shop.teslarati.com

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Tesla’s Robotaxi expansion wasn’t a joke, it was a warning to competitors

Tesla might have made a joke with its first Robotaxi service area expansion, but it was truly a serious warning to its competitors.

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2 hours ago

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July 14, 2025

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Tesla’s Robotaxi expansion occurred for the first time on Monday, and while the shape of its new service area might be “cocky,” it surely is not a joke. It’s a warning to competitors.

Robotaxi skeptics and Tesla opponents are sitting around throwing hate toward the company’s expansion appearance. Some called it “unserious,” and others say it’s “immature.” The reality is that it has a real meaning that goes much further than the company’s lighthearted and comical attitude toward things.

For context, Tesla has routinely used the number 69 as a way to price things it sells. 420 is another, an ode to cannabis culture. A few years back, it actually priced its Model S flagship sedan at $69,420. The first rides of the Robotaxi fleet were priced at $4.20. They are now being increased to $6.90.

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Some call it childish. Others call it fun. The truth is, nobody is doing it this way.

Tesla updates Robotaxi app with several big changes, including wider service area

But today’s expansion of the Robotaxi service area in Austin is different. Tesla did not expand its shape to different neighborhoods or areas of the City of Austin. It did not expand it by broadening the rectangle that was initially available. Instead, it chose a different strategy, simply because it could:

Tesla could have done anything. It could have expanded in any direction, in any way, but it chose this simply because it has gotten Robotaxi to the point that it can broaden its service area in any direction. It chose this shape because it could.

Other companies might not have the same ability. Of course, many companies probably would not do this even if it could, simply because of the optics. Tesla doesn’t have those concerns; it has been open about its ability to be funny, and yes, immature, at times.

But in reality, it was a stark warning to competitors. “We can go anywhere in Austin, at any time, and we’re confident enough to make a joke about it.”

Tesla’s Robotaxi geofence in Austin grows, and its shape is hard to ignore

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As Tesla is already aiming to expand to new states and high-population areas, and with applications filed in Arizona and California, Robotaxi will be in new regions in the coming weeks or months.

For now, it remains in Austin, and Tesla is sending a message to other companies that it is ready to go in any direction. The driverless Robotaxi fleet, bolstered by billions of miles of data, is ready to roam without anyone at the wheel.

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Tesla Robotaxi has already surpassed Waymo in this key metric

Tesla Robotaxi has already overtaken Waymo in Austin in one key metric, but there’s still more work to do.

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7 hours ago

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July 14, 2025

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Credit: @HanChulYong/X

Tesla Robotaxi has already surpassed Waymo in one extremely important key metric: size of service area.

Tesla just expanded its service area in Austin on Monday morning, pushing the boundaries of its Robotaxi fleet in an interesting fashion with new capabilities to the north. Yes, we know what it looks like:

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The expansion doubled Tesla Robotaxi’s potential travel locations, which now include the University of Texas at Austin, a school with over 53,000 students.

The doubling of the service area by Tesla has already made its travel area larger than Waymo’s, which launched driverless rides in October 2024. It became available to the public in March 2025.

According to Grok, the AI agent on X, Tesla Robotaxi’s current service area spans 42 square miles, which is five square miles larger than Waymo’s service area of 37 square miles.

The service area is one of the most important metrics in determining how much progress a self-driving ride-hailing service is making. Safety is the priority of any company operating a ride-hailing network, especially ones that are making it a point to use autonomy to deploy it.

However, these companies are essentially racing for a larger piece of the city or cities they are in. Waymo has expanded to several different regions around the United States, including Arizona and Los Angeles.

Tesla is attempting to do the same in the coming months as it has already filed paperwork in both California and Arizona to deploy its Robotaxi fleet in states across the U.S.

As the platform continues to show more prowess and accuracy in its operation, Tesla will begin to expand to new areas, eventually aiming for a global rollout of its self-driving service.

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Tesla Megapacks arrive for massive battery replacing coal plant

Tesla Megapacks have started arriving on-site to the Stanwell Battery Project, just as Queensland prepares to wind down the Stanwell coal plant.

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8 hours ago

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July 14, 2025

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Tesla-megapack-pilot-project-willowbrook-mall
Credit: Tesla

The first of over 300 Tesla Megapacks have arrived to the site of a massive battery energy storage system (BESS) being built in Australia, dubbed the Stanwell Battery Project after a coal plant it’s set to replace.

In a press release last week, the Stanwell Battery Project announced that the first Tesla Megapack 2XL units had arrived to the site, which is located outside of Rockhampton in Queensland, Australia. The project will eventually feature 324 Megapack units, set to arrive in the coming months, in order to support the 300MW/1,200MWh battery project.

“The Stanwell Battery is part of the diversification of our portfolio, to include cleaner and more flexible energy solutions,” said Angie Zahra, Stanwell Central Generation General Manager. “It is just one part of the 800 MW of battery energy storage capacity we have in our pipeline.

“Capable of discharging 300 MW of energy for up to four hours (1,200 MWh), our mega battery will be one of the largest in Queensland.”

Credit: Stanwell

READ MORE ON TESLA MEGAPACKS: Tesla Lathrop Megafactory celebrates massive Megapack battery milestone

The state is working with government-owned company Yurika to facilitate construction, and the process is expected to create roughly 80 jobs. The project is expected to come fully online in May 2027, with initial commissioning of the Megapacks aiming for November 2025.

The Stanwell Battery is set to replace the nearby Stanwell coal generation plant, which the government is planning to wind down starting in 2026 as part of efforts to reach an 80 percent renewable energy generation ratio by 2035. Meanwhile, the government is also set to begin winding down the Tarong and Callide coal plants, while several other Megapack projects are being built or coming online. o ya

Tesla currently has two Megapack production facilities, located in Lathrop, California, in the U.S. and another that came online earlier this year in Shanghai, China. The Shanghai Megafactory shipped its first units to Australia in March, while both factories are expected to be capable of producing 10,000 Megapack units per year upon reaching volume production.

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xAI receives more Tesla Megapacks for Colossus 2

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