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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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In a major development that will inevitably strengthen Tesla’s dominant position in the American EV market, Polestar has been effectively banned from selling new vehicles in the United States, starting with the 2027 model year.
The U.S. Department of Commerce denied Polestar authorization under the Connected Vehicle Rule, which prohibits vehicles containing certain connected technologies (Cellular, Wi-Fi, Bluetooth, etc.) linked to China or Russia due to national security risks, including potential data collection on American drivers.
🚨 A Tesla competitor goes down
Polestar will no longer sell new vehicles in the United States starting with the 2027 model year.
The U.S. Department of Commerce denied the brand authorization under the Connected Vehicle Rule, which restricts the sale of cars with software and… pic.twitter.com/TrwnQeoiES
— TESLARATI (@Teslarati) June 25, 2026
Polestar, which is majority-owned by China’s Geely Holding, could not obtain the required exemption despite producing some models domestically.
Polestar confirmed it will sell off any remaining inventory of the Polestar 3 and Polestar 4 models, while continuing service and warranty support for existing customers. No new models or major refreshes will reach U.S. buyers, and the company is pivoting its growth strategy to Europe, where it already generates the vast majority of its sales.
The outcome removes a direct premium EV competitor that had positioned itself as a stylish, performance-oriented alternative to Tesla’s lineup. The Polestar 2 challenged the Model 3, while the Polestar 3 and 4 targeted segments overlapping with the Model Y and upcoming Tesla offerings. Polestar’s U.S. sales had already been sluggish amid intense competition and slower demand, representing just 6 percent of its global volume in the first quarter of 2026.
While Polestar was not on Tesla’s level in the U.S., it still places a dent in the evergrowing field of Tesla competitors in the country, where it has long dominated EV sales.
Tesla faces none of these hurdles. As a U.S.-founded and U.S.-headquartered company with major manufacturing in Fremont, Austin, and Nevada, Tesla’s vehicles are built with compliant domestic and allied supply chains. Its Full Self-Driving technology, over-the-air software updates, and vertically integrated ecosystem were developed entirely in-house without foreign ownership entanglements that trigger national security reviews, at least in the U.S.
Of course, it did face a similar threat in China a few years back:
Elon Musk responds to reports of Tesla ban among China’s military over security concerns
The Connected Vehicle Rule, first advanced under the prior administration and upheld under the current one, is part of a broader U.S. effort to protect the domestic auto industry and critical technology from Chinese influence. High tariffs on Chinese-made EVs and related restrictions have already reshaped the market. Tesla benefits directly: it avoids these barriers while continuing to lead in U.S. EV sales volume, Supercharger network expansion, and energy storage integration.
By clearing Polestar from the new-vehicle playing field, the policy reduces competitive pressure in the premium and performance EV segments where Tesla has invested billions. American consumers seeking cutting-edge electric vehicles now have one fewer option tied to foreign adversaries — and one clearer path to the market leader that has driven the EV transition from the start.
For Tesla, this is more than regulatory relief. It is a strategic tailwind that reinforces its position as America’s premier EV innovator at a time when domestic manufacturing and technological independence matter most.
Tesla Cybercab stands to gain from new rules that the Trump Administration is aiming to enforce on autonomous vehicles. On Thursday, NHTSA, under the Trump Administration’s U.S. Department of Transportation, commenced rulemaking on the Federal Motor Vehicle Safety Standards (FMVSS).
This effort aims to eliminate the mandate for manual brake pedals in vehicles that are designed to be driven exclusively by automated driving systems. This would impact the Tesla Cybercab, which the company has stated would operate without a steering wheel or pedals.
Tesla Cybercab launch is imminent after latest sighting at Giga Texas
The Trump Administration is looking to revise FMVSS No. 135, which requires standard braking systems on light-duty vehicles.
Currently, the regulation requires light-duty cars to use traditional manual braking systems that allow operators to slow the vehicle. With the advent of self-driving in the U.S., these regulations need updating, and these are the changes that could come to FMVSS No. 135:
- Removes requirements for hand- or foot-operated brake controls for vehicles designed never to be operated by a human. Existing rules still apply to AVs that retain manual controls.
- All subject vehicles must still meet the same stopping distance performance criteria via alternative testing procedures.
- While this update ensures AVs can physically stop when commanded, NHTSA is separately developing safety performance requirements for AVs in real-world driving scenarios.
- NHTSA will continue to use its broad defect enforcement authority to investigate unsafe ADS behavior and oversee recalls.
As autonomy becomes a greater part of passenger travel, these types of rule adjustments will be more than reasonable. It will give manufacturers the ability to self-certify their vehicles and avoid any red tape that could ultimately delay the deployment of these vehicles.
Administrators are also incredibly excited about the opportunity to play a role in the advancement of self-driving vehicles.
“We are at the cusp of the greatest technological revolution in vehicle technology since the innovation of the Model T,” NHTSA Administrator Jonathan Morrison said. “If we want America to lead the way, we have to reimagine our regulatory framework. That’s why under Secretary Sean Duffy’s AV Framework, NHTSA is tearing down pointless barriers to innovative designs while strengthening the fundamental safety requirements that matter and holding AV developers accountable for safe performance.”
The Cybercab entered mass production at Gigafactory Texas in April. Tesla ultimately plans to push the vehicle into its Robotaxi fleet, potentially when frameworks like these are established.
Tesla plans to boost production at its Gigafactory Berlin plant in Germany following a sharp rebound in sales and demand in Europe after a softer 2025.
The plans put Tesla in a better position to compete with strengthening companies in Europe and potentially other markets; demand indicators show Tesla is much better off than in 2025.
Last year was a tough year for Tesla in terms of overall demand in Europe. The company produced over 200,000 vehicles at the German plant last year, a soft figure compared to the 375,000 vehicles Tesla lists as its current capacity at the factory.
🚨 Tesla said this morning it will ramp up production at Gigafactory Berlin to a volume of 7,500 vehicles per week.
This is a 20 percent boost in production. Tesla will hire 1,000 new employees to help with the increase.$TSLA pic.twitter.com/kravKfRO5n
— TESLARATI (@Teslarati) June 25, 2026
Tesla’s overall European sales dropped significantly last year due to a variety of factors. However, sales are rebounding, and demand is strong once again, and only getting stronger. Tesla is now planning to bump production of Model Y vehicles at Giga Berlin upward by about 20 percent. It will also bring 1,000 new jobs to the plant.
Tesla confirmed the details of its planned production expansion in Germany this morning. It is a strategy to keep up with strengthening demand.
In Q1, Tesla saw a record 61,000 vehicles produced at Giga Berlin. European registrations rebounded sharply, with Model Y seeing 117 percent increases in March 2026 compared to last year. Germany alone saw stark increases, with a quadrupling in registrations to 9,252 units.
This trend continued in other key European markets, including France, Denmark and Sweden. Tesla registrations were up over 46 percent in some of these markets, and Model Y continued its trend as a top BEV in the market.
Demand has been recovering strongly in 2026, giving Tesla a reason to expand production efforts at the factory. These increases signal management’s confidence in sustained or growing European pull for Berlin-built vehicles.
One of Tesla’s biggest threats just got banned in the U.S.
Tesla Cybercab stands to gain from new Trump autonomy rules
