News
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.
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.
News
Tesla removes Model S and X custom orders as sunset officially begins
In a significant development that marks the beginning of the end for two of its longest-running models, Tesla has removed the custom order configurator for the Model S sedan and Model X SUV from its website.
Tesla has officially started the “honorable discharge” of the Model S and Model X with a massive move, removing the two vehicles from Custom Orders and only offering inventory options.
It is the latest move Tesla has made to pull the Model S and Model X from its lineup, a decision CEO Elon Musk announced during its last quarterly earnings call.
Tesla brings closure to flagship ‘sentimental’ models, Musk confirms
In a significant development that marks the beginning of the end for two of its longest-running models, Tesla has removed the custom order configurator for the Model S sedan and Model X SUV from its website.
As of April 1, visitors to tesla.com/model-s and tesla.com/modelx are now redirected exclusively to limited inventory listings rather than a design studio, allowing buyers to select paint, wheels, interior options, or performance upgrades. Only pre-built vehicles currently in stock are available for purchase or lease.
Tesla CEO Elon Musk confirmed the change directly on X, posting: “Custom orders of the Tesla Model S & X have come to an end. All that’s left are some in inventory.”
Custom orders of the Tesla Model S & X have come to an end. All that’s left are some in inventory.
We will have an official ceremony to mark the ending of an era. I love those cars.
This was me at production launch 14 years ago: pic.twitter.com/6kvCf9HTHc
— Elon Musk (@elonmusk) April 1, 2026
We will have an official ceremony to mark the end of an era.” Accompanying the statement was a throwback photo from the Model S production launch in 2012, underscoring the emotional weight of the decision.
Musk had first signaled the phase-out during the company’s Q4 2025 earnings call in January, describing it as time for an “honorable discharge” of the programs to free up resources at the Fremont factory for Optimus humanoid robot production and autonomous vehicle initiatives.
The Model S, introduced in 2012, and the Model X, which followed in 2015, were instrumental in establishing Tesla as a premium electric vehicle leader.
The sedan offered class-leading range and acceleration, while the SUV’s signature falcon-wing doors became an iconic feature. Together, they proved EVs could compete in the luxury segment. Yet sales volumes have dwindled in recent years as Tesla prioritized higher-volume Model 3 and Model Y vehicles.
The flagships now represent a tiny fraction of overall deliveries, making continued custom production inefficient as the company accelerates toward robotaxis and next-generation platforms.
Prospective buyers are urged to act quickly. Remaining U.S. inventory vehicles—some nearly new—may include incentives such as lifetime free Supercharging, Full Self-Driving (Supervised) capability, and premium connectivity, depending on configuration.
Leasing options start around $1,699 per month for select Model X units, though exact pricing and availability fluctuate. International markets, including Europe and China, have already seen similar restrictions in recent months.
The move aligns with Tesla’s broader strategy to streamline its lineup and redirect manufacturing capacity toward autonomy and AI-driven products. While some enthusiasts lament the loss of personalization, the company views the transition as necessary progress.
Tesla has indicated that once the current inventory sells out, new Model S and Model X vehicles will no longer be offered.
For loyal owners and fans, the promised “official ceremony” may provide a fitting send-off. In the meantime, the website change serves as a clear signal: the era of bespoke flagship Teslas has quietly concluded, and the focus has fully shifted to the future.
Elon Musk
SpaceX files confidentially for IPO that will rewrite the record books
SpaceX files confidentially for a record-breaking IPO targeting a $1.75T valuation and $80B raise, driven by Starlink growth and its xAI merger.
Elon Musk’s rocket and satellite company submitted its draft registration to the U.S. Securities and Exchange Commission today for an initial public offering, targeting June at a $1.75 trillion valuation. This would be the largest in history.
SpaceX has filed confidentially with the SEC, first reported by Bloomberg. SpaceX would be valued above every S&P 500 company except Nvidia, Apple, Alphabet, Microsoft, and Amazon.
The filing uses a confidential process that allows companies to work through SEC disclosures privately before initiating a public roadshow. With a June target, official details through a formal prospectus is expected to go public in April or early May, after which SpaceX must wait at least 15 days before beginning investor marketing.
While SpaceX is best known for its Falcon 9 and Starship rockets, the $1.75 trillion valuation is anchored by Starlink, its satellite internet service. Starlink ended 2025 with 9.2 million subscribers and over $10 billion in revenue, which is a figure analysts project could reach a staggering $24 billion by the end of 2026. A February all-stock merger with xAI, Musk’s artificial intelligence venture, further boosted the valuation.
SpaceX officially acquires xAI, merging rockets with AI expertise
Bank of America, Goldman Sachs, JPMorgan Chase, and Morgan Stanley are lined up as senior underwriters. SpaceX is also considering a dual-class share structure to preserve insider voting control, and plans to allocate up to 30% of shares to retail investors, which is roughly three times the typical norm.
Elon Musk
Elon Musk hints at “official ceremony” with throwback photo to close Tesla Model S, Model X chapter
Elon Musk promises an official ceremony to mark the end of Tesla Model S and Model X production.
Tesla has officially begun winding down production of the Model S and Model X, sending farewell emails to U.S. customers on March 27 and updating the website to reflect the end of the line. Shoppers visiting Tesla.com now find only a limited set of Model S and Model X inventory units available for purchase, with no option to configure a new factory build. The move formalizes what CEO Elon Musk announced on the company’s Q4 2025 earnings call in January, when he said it was “time to basically bring the Model S and X programs to an end with an honorable discharge.”
Musk posted on X a throwback photo of himself speaking at the Model S production launch in 2012, and noting “We will have an official ceremony to mark the ending of an era. I love those cars.”
The mention of an official ceremony is notable. Tesla has not held a formal farewell event for a vehicle before, and Musk’s wording suggests this will be something deliberate rather than a quiet line shutdown. Given that Musk’s X post shows a photo of him on stage with a microphone in front of an audience at the Fremont factory, it wouldn’t be too far-fetched to expect a closing ceremony to take place at the same location. Perhaps? Whether it becomes a public event, a private gathering for employees, or a livestreamed moment on X remains to be seen.
Custom orders of the Tesla Model S & X have come to an end. All that’s left are some in inventory.
We will have an official ceremony to mark the ending of an era. I love those cars.
This was me at production launch 14 years ago: pic.twitter.com/6kvCf9HTHc
— Elon Musk (@elonmusk) April 1, 2026
The Model S first went on sale nearly fifteen years ago and was Tesla’s first fully in-house designed vehicle, proving that an electric car could be fast, desirable, and capable of long distance on a single charge. The Model X followed in 2015, turning heads with its unmistakable and distinctive falcon-wing doors, while becoming one of the first all-electric SUVs on the market. Tesla’s two flagship vehicles would ultimately push legacy automakers to take all-electric transportation seriously and help fund development of the more affordable Model 3 and Model Y.
By 2025, however, both models had been reduced to a rounding error in Tesla’s sales figures. Musk was direct about what comes next, stating “We are going to convert that production space to an Optimus factory. It’s part of our overall shift to an autonomous future.”
Elon Musk’s $10 Trillion robot: Inside Tesla’s push to mass produce Optimus
That shift is already underway. Tesla officially started Optimus Gen 3 production at its Fremont factory in January 2026, with the line targeting a run rate of one million units per year. The Gen 3 robot features 22 degrees of freedom per hand, runs on Tesla’s AI5 chip, and shares the same neural network architecture as Full Self-Driving. A dedicated Optimus factory at Gigafactory Texas is also under construction, with a planned annual capacity of 10 million units. The production lines that once built the Model S and Model X are being converted to support that ramp.
Tesla confirmed it will continue to support existing owners with service, software updates, and parts for as long as people own the vehicles. For buyers still interested in a new example, remaining U.S. inventory is discounted and the window is closing fast.
Tesla removes Model S and X custom orders as sunset officially begins
SpaceX files confidentially for IPO that will rewrite the record books
Elon Musk hints at “official ceremony” with throwback photo to close Tesla Model S, Model X chapter
Elon Musk says Tesla is developing a new vehicle: ‘Way cooler than a minivan’
Elon Musk launches TERAFAB: The $25B Tesla-SpaceXAI chip factory that will rewire the AI industry
