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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) could be approved in the Netherlands next month: Musk
Musk shared the update during a recent interview at Giga Berlin.
Tesla CEO Elon Musk shared that Full Self-Driving (FSD) could receive regulatory approval in the Netherlands as soon as March 20, potentially marking a major step forward for Tesla’s advanced driver-assistance rollout in Europe.
Musk shared the update during a recent interview at Giga Berlin, noting that the date was provided by local authorities.
“Tesla has the most advanced real-world AI, and hopefully, it will be approved soon in Europe. We’re told by the authorities that March 20th, it’ll be approved in the Netherlands,’ what I was told,” Musk stated.
“Hopefully, that date remains the same. But I think people in Europe are going to be pretty blown away by how good the Tesla car AI is in being able to drive.”
Tesla’s FSD system relies on vision-based neural networks trained on real-world driving data, allowing vehicles to navigate using cameras and AI rather than traditional sensor-heavy solutions.
The performance of FSD Supervised has so far been impressive. As per Tesla’s safety report, Full Self-Driving Supervised has already traveled 8.3 billion miles. So far, vehicles operating with FSD Supervised engaged recorded one major collision every 5,300,676 miles.
In comparison, Teslas driven manually with Active Safety systems recorded one major collision every 2,175,763 miles, while Teslas driven manually without Active Safety recorded one major collision every 855,132 miles. The U.S. average during the same period was one major collision every 660,164 miles.
If approval is granted on March 20, the Netherlands could become the first European market to greenlight Tesla’s latest supervised FSD (Supervised) software under updated regulatory frameworks. Tesla has been working to secure expanded FSD access across Europe, where regulatory standards differ significantly from those in the United States. Approval in the Netherlands would likely serve as a foundation for broader EU adoption, though additional country-level clearances may still be required.
Elon Musk
Elon Musk estimates Tesla Semi could reach Europe next year
“We’ve got the Tesla Semi coming out, the heavy truck, and that’ll be going to Europe hopefully next year,” Musk said.
Tesla is preparing to expand its all-electric Semi truck program to Europe, with CEO Elon Musk indicating that the Class 8 vehicle could arrive in the region 2027.
Musk shared his update during an interview about Giga Berlin with plant manager André Thierig, which was posted on X by the official Tesla Manufacturing account.
“We’ve got the Tesla Semi coming out, the heavy truck, and that’ll be going to Europe hopefully next year,” he said.
Tesla has already begun limited production and customer deployments of the Tesla Semi in the United States, with the company working to scale output through the Semi factory near Giga Nevada. Considering Musk’s comments, it appears that a European rollout would be the next phase of the vehicle’s expansion beyond North America.
Musk’s use of the word “hopefully” leaves room for flexibility, but the remark signals that Europe is next in Tesla’s commercial expansion plans.
Musk has consistently argued that electrification should extend beyond passenger vehicles. During the same interview, he reiterated his view that “all ground transport should be electric,” adding that ships, and eventually aircraft, would follow.
The Semi plays a central role in that strategy. Heavy-duty freight remains one of the most emissions-intensive segments of road transport, and European regulators have increasingly pushed for lower-emission commercial fleets.
Tesla recently refreshed the Semi lineup on its official website, listing two variants: Standard and Long Range. The Standard trim offers up to 325 miles of range with an energy consumption rating of 1.7 kWh per mile, while the Long Range version provides up to 500 miles, which should be more than ample for European routes.
Elon Musk
Tesla Cybercab coming next to Giga Berlin, Optimus possibly after
“From a next major product standpoint, I think most likely is the Tesla Cybercab,” Musk said.
Tesla could add the Cybercab and Optimus humanoid robot to the production lineup at Giga Berlin, as per recent comments from CEO Elon Musk.
During a recent interview with Giga Berlin plant manager André Thierig, Musk identified the Cybercab as the most likely next major product for the German factory, with Optimus potentially following after.
“From a next major product standpoint, I think most likely is the Tesla Cybercab,” Musk said. He added that there are also “possibilities of Tesla Optimus” being produced in the facility.
Tesla has already begun production of the Cybercab in Giga Texas, with volume production expected to ramp this year. Based on Musk’s comments, it appears that if conditions align in Europe, Giga Berlin could eventually join that effort.
The CEO’s comments about Optimus coming to Gigafactory Berlin are quite unsurprising too considering that Musk has mentioned in the past that the humanoid robot will likely be Tesla’s highest volume product in the long run.
Giga Berlin will likely be able to produce mass volumes of Optimus, as the Model S and Model X lines being converted to an Optimus line in the Fremont Factory are already expected to produce 1 million units of the humanoid robot annually.
Apart from his comments about the Cybercab and Optimus, Elon Musk also confirmed that Giga Berlin has started ramping battery cell production and will continue expanding Model Y output, particularly as supervised Full Self-Driving (FSD) gains regulatory approvals in Europe.
Taken together, the remarks suggest Berlin’s role could evolve beyond vehicle assembly into a broader multi-product manufacturing hub, not just a regional Model Y plant.
Tesla FSD (Supervised) could be approved in the Netherlands next month: Musk
Elon Musk estimates Tesla Semi could reach Europe next year
