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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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Elon Musk

Elon Musk reveals date of Tesla Robotaxi’s first rides open to public

Tesla CEO Elon Musk continues to roll out new details regarding the Robotaxi launch that is expected to happen soon.

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1 hour ago

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June 10, 2025

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Credit: Tesla

Tesla Robotaxi is set to launch in the coming days, but the first rides will be confined to those who receive invitations that the company sends out. However, CEO Elon Musk revealed the date that Tesla is aiming for when anyone in the general public will be able to call for a Robotaxi.

There has been quite a bit of information today about what appears to be an imminent launch of the Robotaxi platform. The first video of a Robotaxi was captured on a public road in Austin today, just one day after Tesla was added to the City of Austin’s list of licensed autonomous vehicle operators.

First Tesla driverless robotaxi spotted in the wild in Austin, TX

In the coming days, it is expected that Tesla will launch the Robotaxi platform in Austin to a select few. For now, Tesla is taking this ultra-conservative approach as it pertains to the rollout, citing safety precautions. It will be the first time Tesla has done this in public and offered it to people outside of the company.

It did launch a small, limited version of it to employees last month in Austin and the San Francisco Bay Area, but there was someone in the driver’s seat. Today’s video only had an occupant in the passenger seat.

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People are eager to know: when will they be able to fetch a driverless Tesla Model Y Robotaxi in Austin for themselves? Musk finally answered the long-awaited question with a tentative date of June 22:

Musk cited that Tesla’s utmost priority is still safety and not necessarily the speed of rollout. The current plan seems to be to deploy it in a controlled and slow fashion until confidence is at an extremely high level. Musk seems to believe the rollout will go smoothly, as the date comes less than two weeks after the initial launch.

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Anyone who has experienced Full Self-Driving for themselves knows what the cars are capable of. However, Tesla, at this point in time, still requires drivers to pay attention and remain ready to take over the wheel in case of an emergency. This will be a major step in the right direction for Tesla as it prepares to launch Robotaxi in Austin and slowly expand to surrounding areas.

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Elon Musk

Elon Musk says Tesla Robotaxi launch will force companies to license Full Self-Driving

“The automakers keep being told that this isn’t real or that just buying some hardware from Nvidia will solve it. As Tesla robotaxis become widespread and their other solutions don’t work, they will naturally turn to us.”

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5 hours ago

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June 10, 2025

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Tesla CEO Elon Musk says the automaker’s Robotaxi platform launch later this month will essentially force other companies to license Full Self-Driving to achieve their own goals of achieving autonomy.

Musk’s statement comes as a video captured today showed the first Tesla Robotaxi test mules on public streets in Austin, Texas, just one day after the City officially listed the company as an autonomous vehicle operator.

A prediction by investing YouTube and Tesla community member Dave Lee stated that “at least one automaker by end of year” will license Full Self-Driving from the Musk-led company, as it will give rivals the confidence to use the software to run their own self-driving operations.

Lee detailed his theory by stating that the company that chooses to commit to FSD licensing will not be able to integrate the hardware and sell those units immediately. Instead, it will take two years or so to solve the engineering and design applications.

First Tesla driverless robotaxi spotted in the wild in Austin, TX

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Musk revealed his true thoughts on other automakers’ attempts at vehicle autonomy, and said many are being told that Robotaxi is not real or that they can solve their problems with hardware orders to Nvidia.

He went on to say that companies will be forced to turn to Tesla at some point or another, because Robotaxi will be widespread and their solutions to figuring out an effective deployment will prove to be failures:

“The automakers keep being told that this isn’t real or that just buying some hardware from Nvidia will solve it. As Tesla robotaxis become widespread and their other solutions don’t work, they will naturally turn to us.”

Musk has not been shy to respond to speculation regarding the video of the Robotaxi, which was shared on X earlier today. This is perhaps one of the more fiery things he revealed. He seems ultra-confident in what Tesla will prove and achieve in the near future with the launch of the Robotaxi platform.

Many believe it will be rolled out this month. Bloomberg reported recently that Tesla was internally aiming for June 12. The company has not directly responded to these rumors.

Tesla has discussed on several occasions that it is in talks with an automaker about licensing Full Self-Driving, but it has never revealed who. The company first revealed discussions with another automaker in early 2024 when Elon Musk said:

“We’re in conversations with one major automaker regarding licensing FSD. It really just becomes a case of having them use the same cameras and inference computer and licensing our software. Once it becomes obvious that if you don’t have this (FSD) in a car, nobody wants your car. It’s a smart car… The people don’t understand all cars will need to be smart cars, or you will not sell, or nobody would buy it. Once that becomes obvious, I think licensing becomes not optional.”

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Tesla confirms it is in talks with major automaker for potential FSD licensing

Many, including us, suspected that Ford was the company that Tesla was speaking of due to Musk’s relationship with Jim Farley, which resulted in the legacy automaker being the first major car company to adopt Tesla’s North American Charging Standard (NACS), which gave them access to the Supercharging Network.

This catalyzed an onslaught of companies choosing to make the same move as Tesla had truly set itself apart in terms of charging infrastructure.

Companies may be forced to make a similar decision if it can make the same type of statement with the rollout of Robotaxi.

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Elon Musk

Tesla CEO Elon Musk reveals new details about Robotaxi rollout

The first Tesla Robotaxi unit was spotted in Austin earlier today, and CEO Elon Musk is revealing some cool new details.

Published

7 hours ago

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June 10, 2025

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Tesla CEO Elon Musk has revealed new details about the company’s relatively imminent rollout of the Robotaxi platform as the suspected launch date of June 12 continues to near.

Earlier today, the first video showing the first driverless Tesla Robotaxi in Austin was shared on X, just a day after the City officially listed the company as an autonomous vehicle operator on its website. Tesla is listed as a company in the “Testing” phase.

The initial details of the Robotaxi are being revealed by Musk, who is carefully releasing small tidbits that seem to show the capabilities of the entire Tesla fleet, and not necessarily just the vehicles that will be involved in the initial rollout in Austin.

First Tesla driverless robotaxi spotted in the wild in Austin, TX

His first tidbit is one that many Tesla owners and fans will already know: many Teslas are capable of this driveless performance, but Full Self-Driving is not yet refined to the point where the software is quite ready to handle it. Current versions are robust, but not prepared for driverless navigation. The hardware, however, will enable Teslas to be Robotaxis, even if they’re already purchased by owners:

This is one of the biggest advantages Tesla has over other vehicle makers. Simply put, the Over-the-Air software updates that will roll out to FSD users will eventually make their cars into Robotaxis as well.

However, Musk shed some details on the version of FSD that is being run in these new Robotaxis that were spotted. Musk said that the version these Robotaxis are running is a new version, but will soon “merge to main branch.”

There is also an even newer version that has four times the parameters as this newer version that the test-stage Robotaxis are using, but Musk admits that this needs significant refinement before it is released to the public.

As of now, Tesla is simply teasing the actual launch date of the Robotaxi program, but Bloomberg reported earlier this month that it will occur on June 12.

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