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University of Michigan uses recycled Kevlar fiber to solve lithium-sulfur battery life cycle issues

(Credit: University of Michigan)

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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.

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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.

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Joey has been a journalist covering electric mobility at TESLARATI since August 2019. In his spare time, Joey is playing golf, watching MMA, or cheering on any of his favorite sports teams, including the Baltimore Ravens and Orioles, Miami Heat, Washington Capitals, and Penn State Nittany Lions. You can get in touch with joey at joey@teslarati.com. He is also on X @KlenderJoey. If you're looking for great Tesla accessories, check out shop.teslarati.com

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Tesla kicks Robotaxi geofence expansion into high gear in Austin

Tesla has nearly doubled its Robotaxi geofence in Austin for the second time less than two months after it initially launched.

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Credit: @AdanGuajardo/X

Tesla has kicked the expansion of its Robotaxi geofence in Austin, Texas, into high gear, as it grew the service area once again early Sunday morning.

Tesla launched its Robotaxi platform in Austin on June 22, and less than a month later, it was able to expand it. After its first expansion, Tesla had a larger geofence than Waymo, which launched its driverless ride-hailing service to the public in Austin in March. Waymo expanded the week after Tesla’s first augmentation.

Waymo responds to Tesla’s Robotaxi expansion in Austin with bold statement

Now, Tesla has answered Waymo once again by developing its service area in Austin to an even larger size. We expected it, as just two weeks ago, CEO Elon Musk said that the company would be growing the Austin geofence, but did not give an indication by how much.

The first geofence in Austin was roughly 20 square miles. On July 14, when the first expansion took place, Tesla Robotaxi riders had roughly 42 square miles of downtown Austin available for travel.

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On the morning of August 3, Tesla nearly doubled the geofence by growing it to roughly 80 square miles, according to Grok. For reference, Waymo’s current service area in Austin is about 90 square miles:

The expansion further extends the Southern portion of the geofence, going into suburban zones such as Barton Creek.

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The continuous growth shows Tesla is prepared to extend its geofence in basically any direction. Now that it is going into suburban areas, we may get to see more Austin residents experience Robotaxi for an entire evening of activities, including pickup and dropoff at home.

The only question that remains is how much Tesla can expand at one time. The company seems to have the ability to push the geofence to a majority of Austin, but it maintains that safety is its biggest priority.

The company was spotted testing vehicles in the West Austin suburbs in areas like Marble Falls recently, indicating that Tesla could be expanding its service area to hundreds of square miles in the coming months.

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Tesla to appeal jury verdict that held it partially liable for fatal crash

Tesla will appeal the decision from the eight-person jury.

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tesla showroom
(Credit: Tesla)

Tesla will appeal a recent jury verdict that held it partially liable for a fatal crash that occurred in Key Largo, Florida, in 2019.

An eight-person jury ruled that Tesla’s driver assistance technology was at least partially to blame for a crash when a vehicle driven by George McGee went off the road and hit a couple, killing a 22-year-old and injuring the other.

The jury found that Tesla’s tech was found to enable McGee to take his eyes off the road, despite the company warning drivers and vehicle operators that its systems are not a replacement for a human driver.

The company states on its website and Owner’s Manual that Autopilot and Full Self-Driving are not fully autonomous, and that drivers must be ready to take over in case of an emergency. Its website says:

“Autopilot is a driver assistance system that is intended to be used only with a fully attentive driver. It does not turn a Tesla into a fully autonomous vehicle.

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Before enabling Autopilot, you must agree to ‘keep your hands on the steering wheel at all times’ and to always ‘maintain control and responsibility for your vehicle.’ Once engaged, Autopilot will also deliver an escalating series of visual and audio warnings, reminding you to place your hands on the wheel if insufficient torque is applied or your vehicle otherwise detects you may not be attentive enough to the road ahead. If you repeatedly ignore these warnings, you will be locked out from using Autopilot during that trip.

You can override any of Autopilot’s features at any time by steering or applying the accelerator at any time.”

Despite this, and the fact that McGee admitted to “fishing for his phone” after it fell, Tesla was ordered to pay hundreds of millions in damages.

Tesla attorney Joel Smith said in court (via Washington Post):

“He said he was fishing for his phone. It’s a fact. That happens in any car. That isolates the cause. The cause is he dropped his cell phone.”

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In total, Tesla is responsible for $324 million in payouts: $200 million in punitive damages, $35 million to the deceased’s mother, $24 million to their father, and $70 million to their boyfriend, who was also struck but was injured and not killed.

The family of the deceased, Naibel Benavides Leon, also sued the driver and reached a settlement out of court. The family opened the federal suit against Tesla in 2024, alleging that Tesla was to blame because it operated its technology on a road “it was not designed for,” the report states.

Despite the disclosures and warnings Tesla lists in numerous places to its drivers and users of both Autopilot and Full Self-Driving, as well as all of its active safety features, the operator remains responsible for paying attention.

CEO Elon Musk confirmed it would appeal the jury’s decision:

The driver being distracted is a big part of this case that seemed to be forgotten as the jury came to its decision. Tesla’s disclosures and warnings, as well as McGee’s admission of being distracted, seem to be enough to take any responsibility off the company.

The appeal process will potentially shed more light on this, especially as this will be a main point of emphasis for Tesla’s defense team.

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Elon Musk echoes worries over Tesla control against activist shareholders

Elon Musk has spoken on several occasions of the “activist shareholders” who threaten his role at Tesla.

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Credit: xAI | X

Elon Musk continues to raise concerns over his control of Tesla as its CEO and one of its founders, as activist shareholders seem to be a viable threat to the company in his eyes.

Musk has voiced concerns over voting control of Tesla and the possibility of him being ousted by shareholders who do not necessarily have the company’s future in mind. Instead, they could be looking to oust Musk because of his political beliefs or because of his vast wealth.

We saw an example of that as shareholders voted on two separate occasions to award Musk a 2018 compensation package that was earned as Tesla met various growth goals through the CEO’s leadership.

Despite shareholders voting to award Musk with the compensation package on two separate occasions, once in 2018 and again in 2024, Delaware Chancery Court Judge Kathaleen McCormick denied the CEO the money both times. At one time, she called it an “unfathomable sum.”

Musk’s current stake in Tesla stands at 12.8 percent, but he has an option to purchase 304 million shares, which, if exercised, after taxes, he says, would bump his voting control up about 4 percent.

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However, this is not enough of a stake in the company, as he believes a roughly 25 percent ownership stake would be enough “to be influential, but not so much that I can’t be overturned,” he said in January 2024.

Musk’s concerns were echoed in another X post from Thursday, where he confirmed he has no current personal loans against Tesla stock, and he reiterated his concerns of being ousted from the company by those he has referred to in the past as “activist shareholders.”

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Elon Musk explains why he wants 25% voting share at Tesla: “I just want to be an effective steward of very powerful technology”

The CEO said during the company’s earnings call in late July:

“That is a major concern for me, as I’ve mentioned in the past. I hope that is addressed at the upcoming shareholders’ meeting. But, yeah, it is a big deal. I want to find that I’ve got so little control that I can easily be ousted by activist shareholders after having built this army of humanoid robots. I think my control over Tesla, Inc. should be enough to ensure that it goes in a good direction, but not so much control that I can’t be thrown out if I go crazy.”

The X post from Thursday said:

There is a concern that Musk could eventually put his money where his mouth is, and if politicians and judges are able to limit his ownership stake as they’ve been able to do with his pay package, he could eventually leave the company.

The company’s shareholders voted overwhelmingly to approve Musk’s pay package. A vast majority of those who voted to get Musk paid still want him to be running Tesla’s day-to-day operations. Without his guidance, the company could face a major restructuring and would have a vastly new look and thesis.

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