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University of Michigan uses recycled Kevlar fiber to solve lithium-sulfur battery life cycle issues
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.
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.
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Tesla FSD (Supervised) fleet passes 8.4 billion cumulative miles
Tesla’s Full Self-Driving (Supervised) system has now surpassed 8.4 billion cumulative miles.
The figure appears on Tesla’s official safety page, which tracks performance data for FSD (Supervised) and other safety technologies.
Tesla has long emphasized that large-scale real-world data is central to improving its neural network-based approach to autonomy. Each mile driven with FSD (Supervised) engaged contributes additional edge cases and scenario training for the system.
The milestone also brings Tesla closer to a benchmark previously outlined by CEO Elon Musk. Musk has stated that roughly 10 billion miles of training data may be needed to achieve safe unsupervised self-driving at scale, citing the “long tail” of rare but complex driving situations that must be learned through experience.
The growth curve of FSD Supervised’s cumulative miles over the past five years has been notable.
As noted in data shared by Tesla watcher Sawyer Merritt, annual FSD (Supervised) miles have increased from roughly 6 million in 2021 to 80 million in 2022, 670 million in 2023, 2.25 billion in 2024, and 4.25 billion in 2025. In just the first 50 days of 2026, Tesla owners logged another 1 billion miles.
At the current pace, the fleet is trending towards hitting about 10 billion FSD Supervised miles this year. The increase has been driven by Tesla’s growing vehicle fleet, periodic free trials, and expanding Robotaxi operations, among others.
With the fleet now past 8.4 billion cumulative miles, Tesla’s supervised system is approaching that threshold, even as regulatory approval for fully unsupervised deployment remains subject to further validation and oversight.
Tesla’s Full Self-Driving (Supervised) system has now surpassed 8.4 billion cumulative miles.
The figure appears on Tesla’s official safety page, which tracks performance data for FSD (Supervised) and other safety technologies.
Tesla has long emphasized that large-scale real-world data is central to improving its neural network-based approach to autonomy. Each mile driven with FSD (Supervised) engaged contributes additional edge cases and scenario training for the system.
The milestone also brings Tesla closer to a benchmark previously outlined by CEO Elon Musk. Musk has stated that roughly 10 billion miles of training data may be needed to achieve safe unsupervised self-driving at scale, citing the “long tail” of rare but complex driving situations that must be learned through experience.
The growth curve of FSD Supervised’s cumulative miles over the past five years has been notable.
As noted in data shared by Tesla watcher Sawyer Merritt, annual FSD (Supervised) miles have increased from roughly 6 million in 2021 to 80 million in 2022, 670 million in 2023, 2.25 billion in 2024, and 4.25 billion in 2025. In just the first 50 days of 2026, Tesla owners logged another 1 billion miles.
At the current pace, the fleet is trending towards hitting about 10 billion FSD Supervised miles this year. The increase has been driven by Tesla’s growing vehicle fleet, periodic free trials, and expanding Robotaxi operations, among others.
With the fleet now past 8.4 billion cumulative miles, Tesla’s supervised system is approaching that threshold, even as regulatory approval for fully unsupervised deployment remains subject to further validation and oversight.
Elon Musk
Elon Musk fires back after Wikipedia co-founder claims neutrality and dubs Grokipedia “ridiculous”
Musk’s response to Wales’ comments, which were posted on social media platform X, was short and direct: “Famous last words.”
Elon Musk fired back at Wikipedia co-founder Jimmy Wales after the longtime online encyclopedia leader dismissed xAI’s new AI-powered alternative, Grokipedia, as a “ridiculous” idea that is bound to fail.
Musk’s response to Wales’ comments, which were posted on social media platform X, was short and direct: “Famous last words.”
Wales made the comments while answering questions about Wikipedia’s neutrality. According to Wales, Wikipedia prides itself on neutrality.
“One of our core values at Wikipedia is neutrality. A neutral point of view is non-negotiable. It’s in the community, unquestioned… The idea that we’ve become somehow ‘Wokepidea’ is just not true,” Wales said.
When asked about potential competition from Grokipedia, Wales downplayed the situation. “There is no competition. I don’t know if anyone uses Grokipedia. I think it is a ridiculous idea that will never work,” Wales wrote.
After Grokipedia went live, Larry Sanger, also a co-founder of Wikipedia, wrote on X that his initial impression of the AI-powered Wikipedia alternative was “very OK.”
“My initial impression, looking at my own article and poking around here and there, is that Grokipedia is very OK. The jury’s still out as to whether it’s actually better than Wikipedia. But at this point I would have to say ‘maybe!’” Sanger stated.
Musk responded to Sanger’s assessment by saying it was “accurate.” In a separate post, he added that even in its V0.1 form, Grokipedia was already better than Wikipedia.
During a past appearance on the Tucker Carlson Show, Sanger argued that Wikipedia has drifted from its original vision, citing concerns about how its “Reliable sources/Perennial sources” framework categorizes publications by perceived credibility. As per Sanger, Wikipedia’s “Reliable sources/Perennial sources” list leans heavily left, with conservative publications getting effectively blacklisted in favor of their more liberal counterparts.
As of writing, Grokipedia has reportedly surpassed 80% of English Wikipedia’s article count.
News
Tesla Sweden appeals after grid company refuses to restore existing Supercharger due to union strike
The charging site was previously functioning before it was temporarily disconnected in April last year for electrical safety reasons.
Tesla Sweden is seeking regulatory intervention after a Swedish power grid company refused to reconnect an already operational Supercharger station in Åre due to ongoing union sympathy actions.
The charging site was previously functioning before it was temporarily disconnected in April last year for electrical safety reasons. A temporary construction power cabinet supplying the station had fallen over, described by Tesla as occurring “under unclear circumstances.” The power was then cut at the request of Tesla’s installation contractor to allow safe repair work.
While the safety issue was resolved, the station has not been brought back online. Stefan Sedin, CEO of Jämtkraft elnät, told Dagens Arbete (DA) that power will not be restored to the existing Supercharger station as long as the electric vehicle maker’s union issues are ongoing.
“One of our installers noticed that the construction power had been backed up and was on the ground. We asked Tesla to fix the system, and their installation company in turn asked us to cut the power so that they could do the work safely.
“When everything was restored, the question arose: ‘Wait a minute, can we reconnect the station to the electricity grid? Or what does the notice actually say?’ We consulted with our employer organization, who were clear that as long as sympathy measures are in place, we cannot reconnect this facility,” Sedin said.
The union’s sympathy actions, which began in March 2024, apply to work involving “planning, preparation, new connections, grid expansion, service, maintenance and repairs” of Tesla’s charging infrastructure in Sweden.
Tesla Sweden has argued that reconnecting an existing facility is not equivalent to establishing a new grid connection. In a filing to the Swedish Energy Market Inspectorate, the company stated that reconnecting the installation “is therefore not covered by the sympathy measures and cannot therefore constitute a reason for not reconnecting the facility to the electricity grid.”
Sedin, for his part, noted that Tesla’s issue with the Supercharger is quite unique. And while Jämtkraft elnät itself has no issue with Tesla, its actions are based on the unions’ sympathy measures against the electric vehicle maker.
“This is absolutely the first time that I have been involved in matters relating to union conflicts or sympathy measures. That is why we have relied entirely on the assessment of our employer organization. This is not something that we have made any decisions about ourselves at all.
“It is not that Jämtkraft elnät has a conflict with Tesla, but our actions are based on these sympathy measures. Should it turn out that we have made an incorrect assessment, we will correct ourselves. It is no more difficult than that for us,” the executive said.
Tesla FSD (Supervised) fleet passes 8.4 billion cumulative miles
Elon Musk fires back after Wikipedia co-founder claims neutrality and dubs Grokipedia “ridiculous”
