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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 China delivery centers look packed as 2025 comes to a close
Needless to say, it appears that Tesla China seems intent on ending 2025 on a strong note.
Tesla’s delivery centers in China seem to be absolutely packed as the final days of 2025 wind down, with photos on social media showing delivery locations being filled wall-to-wall with vehicles waiting for their new owners.
Needless to say, it appears that Tesla China seems intent on ending 2025 on a strong note.
Full delivery center hints at year-end demand surge
A recent image from a Chinese delivery center posted by industry watcher @Tslachan on X revealed rows upon rows of freshly prepared Model Y and Model 3 units, some of which were adorned with red bows and teddy bears. Some customers also seem to be looking over their vehicles with Tesla delivery staff.
The images hint at a strong year-end push to clear inventory and deliver as many vehicles as possible. Interestingly enough, several Model Y L vehicles could be seen in the photos, hinting at the demand for the extended wheelbase-six seat variant of the best-selling all-electric crossover.
Strong demand in China
Consumer demand for the Model Y and Model 3 in China seems to be quite notable. This could be inferred from the estimated delivery dates for the Model 3 and Model Y, which have been extended to February 2026 for several variants. Apart from this, the Model Y and Model 3 also continue to rank well in China’s premium EV segment.
From January to November alone, the Model Y took China’s number one spot in the RMB 200,000-RMB 300,000 segment for electric vehicles, selling 359,463 units. The Model 3 sedan took third place, selling 172,392. This is quite impressive considering that both the Model Y and Model 3 are still priced at a premium compared to some of their rivals, such as the Xiaomi SU7 and YU7.
With delivery centers in December being quite busy, it does seem like Tesla China will end the year on a strong note once more.
News
Tesla Giga Berlin draws “red line” over IG Metall union’s 35-hour week demands
Factory manager André Thierig has drawn a “red line” against reducing Giga Berlin’s workweek to 35 hours, while highlighting that Tesla has actually increased its workers’ salaries more substantially than other carmakers in the country.
Tesla Giga Berlin has found itself in a new labor dispute in Germany, where union IG Metall is pushing for adoption of a collective agreement to boost wages and implement changes, such as a 35-hour workweek.
In a comment, Giga Berlin manager André Thierig drew a “red line” against reducing Giga Berlin’s workweek to 35 hours, while highlighting that Tesla has actually increased its workers’ salaries more substantially than other carmakers in the country.
Tesla factory manager’s “red line”
Tesla Germany is expected to hold a works council election in 2026, which André Thierig considers very important. As per the Giga Berlin plant manager, Giga Berlin’s plant expansion plans might be put on hold if the election favors the union. He also spoke against some of the changes that IG Metall is seeking to implement in the factory, like a 35-hour week, as noted in an rbb24 report.
“The discussion about a 35-hour week is a red line for me. We will not cross it,” Theirig said.
“(The election) will determine whether we can continue our successful path in the future in an independent, flexible, and unbureaucratic manner. Personally, I cannot imagine that the decision-makers in the USA will continue to push ahead with the factory expansion if the election results favor IG Metall.”
Giga Berlin’s wage increase
IG Metall district manager Jan Otto told the German news agency DPA that without a collective agreement, Tesla’s wages remain significantly below levels at other German car factories. He noted the company excuses this by referencing its lowest pay grade, but added: “The two lowest pay grades are not even used in car factories.”
In response, Tesla noted that it has raised the wages of Gigafactory Berlin’s workers more than their German competitors. Thierig noted that with a collective agreement, Giga Berlin’s workers would have seen a 2% wage increase this year. But thanks to Tesla not being unionized, Gigafactory Berlin workers were able to receive a 4% increase, as noted in a CarUp report.
“There was a wage increase of 2% this year in the current collective agreement. Because we are in a different economic situation than the industry as a whole, we were able to double the wages – by 4%. Since production started, this corresponds to a wage increase of more than 25% in less than four years,” Thierig stated.
News
Tesla is seeing a lot of momentum from young Koreans in their 20s-30s: report
From January to November, young buyers purchased over 21,000 Teslas, putting it far ahead of fellow imported rivals like BMW and Mercedes-Benz.
Tesla has captured the hearts of South Korea’s 20s-30s demographic, emerging as the group’s top-selling imported car brand in 2025. From January to November, young buyers purchased over 21,000 Teslas, putting it far ahead of fellow imported rivals like BMW and Mercedes-Benz.
Industry experts cited by The Economist attributed this “Tesla frenzy” to fandom culture, where buyers prioritize the brand over traditional car attributes, similar to snapping up the latest iPhone.
Model Y dominates among young buyers
Data from the Korea Imported Automobile Association showed that Tesla sold 21,757 vehicles to the 20s-30s demographic through November, compared to BMW’s 13,666 and Mercedes-Benz’s 6,983. The Model Y led the list overwhelmingly, with variants like the standard and Long Range models topping purchases for both young men and women.
Young men bought around 16,000 Teslas, mostly Model Y (over 15,000 units), followed by Model 3. Young women followed a similar pattern, favoring Model Y (3,888 units) and Model 3 (1,083 units). The Cybertruck saw minimal sales in this group.
The Model Y’s appeal lies in its family-friendly SUV design, 400-500 km range, quick acceleration, and spacious cargo, which is ideal for commuting and leisure. The Model 3, on the other hand, serves as an accessible entry point with lower pricing, which is valuable considering the country’s EV subsidies.
The Tesla boom
Experts described Tesla’s popularity as “fandom culture,” where young buyers embrace the brand despite criticisms from skeptics. Professor Lee Ho-geun called Tesla a “typical early adopter brand,” comparing purchases to iPhones.
Professor Kim Pil-soo noted that young people view Tesla more as a gadget than a car, and they are likely drawn by marketing, subsidies, and perceived value. They also tend to overlook news of numerous recalls, which are mostly over-the-air software updates, and controversies tied to the company.
Tesla’s position as Korea’s top import for 2025 seems secured. As noted by the publication, Tesla’s December sales figures have not been reported yet, but market analysts have suggested that Tesla has all but secured the top spot among the country’s imported cars this year.
Tesla China delivery centers look packed as 2025 comes to a close
Tesla Giga Berlin draws “red line” over IG Metall union’s 35-hour week demands
