News
Tesla battery researchers open path to all-electric range extender concept
Tesla has solidified itself as an industry leader when it comes to electric vehicles and their range. However, an EV’s range could always be improved, and the company has taken great efforts to make this possible. One of these was outlined by Tesla’s battery researchers, who recently published the results of a test that cycles lithium metal on graphite to form hybrid lithium-ion/lithium metal cells. This particular innovation could open the door to an all-electric range extender.
Other automakers have used range extenders in the past, but they’ve been comprised of small petrol-powered engines that are used as a generator to recharge the vehicle’s battery pack when it is low on range. The process of cycling lithium metal on graphite, on the other hand, could lead to a 20% higher energy density than the traditional lithium-ion cells that power the Tesla’s vehicles.
Tesla’s battery research team, led by Jeff Dahn of Dalhousie University, has found a way to create a range extender of sorts without having to keep a small gas engine in the vehicle. Tesla detailed its findings in a research paper that was published to ScienceDirect on April 30. Titled “Cycling Lithium Metal on Graphite to Form Hybrid Lithium-Ion/Lithium Metal Cells,” Dahn and his researchers outlined the testing process.
The findings proved a possible 20% increase in range when using the range extender, which is comprised of “hybrid cells” that use Lithium-Ion and Lithium Metal. The cells also used an optimized electrolyte, and pressure enabled reversible plating on graphite.
The paper states:
“A hybrid anode cell design is proposed involving lithium metal plating on top of graphite that provides a 20% increase in energy density over conventional lithium-ion cells. Pouch cells with hybrid graphite-lithium metal anodes cycled with conventional electrolytes fell below 80% capacity in under 15 cycles. However, with a dual-salt electrolyte and applied mechanical pressure optimized for lithium metal cycling, hybrid cells achieved over 150 full (100% utilization) cycles before falling below 80% capacity with a CE of 99.6% for lithium metal plating on graphite.
“We also found that intermittent high energy (100% utilization) cycles utilizing lithium metal can be dispersed among hundreds of conventional lithium-ion cycles where only the graphite is utilized. Operating the cell with this intermittent protocol shows minimal impact to the underlying graphite capacity. Therefore, these hybrid cells can operate well in “lithium-ion mode” with periodic high energy full cycles accessing the lithium metal capacity.”
Tesla’s new findings show that increased energy density is made possible with the hybrid concept. When combining lithium-ion cells with lithium metal, energy density improves as the graphite anode utilized in traditional lithium-ion cells is not capable of handling the increased energy. The utilization of a dual-salt electrolyte also increases density and decreases battery cell degradation.
Tesla’s battery researchers described the advantages of the hybrid lithium-ion/lithium metal cells in the discussion below.
“If an electric vehicle with a conventional lithium-ion battery can deliver a range of 400 km, then hybrid cells could enable a range of 480 km. By capping the upper cut-off voltage of hybrid cells to operate in lithium-ion mode, the average cell voltage and delivered capacity will decrease. As a result, operating a hybrid cell in lithium-ion mode delivers an energy density of 530Wh/L, about 25% less than a conventional lithium-ion cell.
“This would result in a range of 300 km. In a study of driving behavior for EVs, Smart et al.34 showed that only 1% of daily trips are longer than 325 km on average. Therefore, operating hybrid cells most of the time in lithium-ion mode enabling a range of 300 km, while periodically using the lithium metal portion for long > 400 km trips, as mimicked by this testing protocol, should be viable for most drivers.”
It should be noted that the Tesla battery researchers’ study is only in their initial stages. Thus, it may take some time before the technology gets rolled out to Tesla’s fleet. The wait would likely be worth it though, as the hybrid cells could open the door to all-electric vehicles with range extender features. This would be incredibly useful for electric vehicle owners who take long road trips with family, and it could also be a notable step towards EVs gaining range parity with their petrol-powered counterparts.
News
Tesla lands approval for Robotaxi operation in third U.S. state
On Tuesday, Tesla officially received regulatory approval from the State of Arizona, making it the third state for the company to receive approval in.
Tesla has officially landed approval to operate its Robotaxi ride-hailing service in its third U.S. state, as it has landed a regulatory green light from the State of Arizona’s Department of Transportation.
Tesla has been working to expand to new U.S. states after launching in Texas and California earlier this year. Recently, it said it was hoping to land in Nevada, Arizona, and Florida, expanding to five new cities in those three states.
On Tuesday, Tesla officially received regulatory approval from the State of Arizona, making it the third state for the company to receive approval in:
BREAKING: Tesla has officially received approval from the Arizona Department of Transportation to launch its Robotaxi service on public roads in the state!
I just confirmed directly with the Arizona DOT that @Tesla applied for a Transportation Network Company permit on Nov 13th.… pic.twitter.com/iKbwfGfiju
— Sawyer Merritt (@SawyerMerritt) November 18, 2025
Tesla has also been working on approvals in Nevada and Florida, and it has also had Robotaxi test mules spotted in Pennsylvania.
The interesting thing about the Arizona approval is the fact that Tesla has not received an approval for any specific city; it appears that it can operate statewide. However, early on, Tesla will likely confine its operation to just one or two cities to keep things safe and controlled.
Over the past few months, Robotaxi mules have been spotted in portions of Phoenix and surrounding cities, such as Scottsdale, as the company has been attempting to cross off all the regulatory Ts that it is confronted with as it attempts to expand the ride-hailing service.
It appears the company will be operating it similarly to how it does in Texas, which differs from its California program. In Austin, there is no Safety Monitor in the driver’s seat, unless the route requires freeway travel. In California, there is always a Safety Monitor in the driver’s seat. However, this is unconfirmed.
Earlier today, Tesla enabled its Robotaxi app to be utilized for ride-hailing for anyone using the iOS platform.
News
Tesla ride-hailing Safety Monitor dozes off during Bay Area ride
We won’t try to blame the camera person for the incident, because it clearly is not their fault. But it seems somewhat interesting that they did not try to wake the driver up and potentially contact Tesla immediately to alert them of the situation.
A Tesla Robotaxi Safety Monitor appeared to doze off during a ride in the California Bay Area, almost ironically proving the need for autonomous vehicles.
The instance was captured on camera and posted to Reddit in the r/sanfrancisco subreddit by u/ohmichael. They wrote that they have used Tesla’s ride-hailing service in the Bay Area in the past and had pleasant experiences.
However, this one was slightly different. They wrote:
“I took a Tesla Robotaxi in SF just over a week ago. I have used the service a few times before and it has always been great. I actually felt safer than in a regular rideshare.
This time was different. The safety driver literally fell asleep at least three times during the ride. Each time the car’s pay attention safety alert went off and the beeping is what woke him back up.
I reported it through the app to the Robotaxi support team and told them I had videos, but I never got a response.
I held off on posting anything because I wanted to give Tesla a chance to respond privately. It has been more than a week now and this feels like a serious issue for other riders too.
Has anyone else seen this happen?”
My Tesla Robotaxi “safety” driver fell asleep
byu/ohmichael insanfrancisco
The driver eventually woke up after prompts from the vehicle, but it is pretty alarming to see someone like this while they’re ultimately responsible for what happens with the ride.
We won’t try to blame the camera person for the incident, because it clearly is not their fault. But it seems somewhat interesting that they did not try to wake the driver up and potentially contact Tesla immediately to alert them of the situation.
They should have probably left the vehicle immediately.
Tesla’s ride-hailing service in the Bay Area differs from the one that is currently active in Austin, Texas, due to local regulations. In Austin, there is no Safety Monitor in the driver’s seat unless the route requires the highway.
Tesla plans to remove the Safety Monitors in Austin by the end of the year.
Tesla has officially opened Robotaxi access to everyone and everyone, but there is one catch: you have to have an iPhone.
Tesla’s Robotaxi service in Austin and its ride-hailing service in the Bay Area were both officially launched to the public today, giving anyone using the iOS platform the ability to simply download the app and utilize it for a ride in either of those locations.
It has been in operation for several months: it launched in Austin in late June and in the Bay Area about a month later. In Austin, there is nobody in the driver’s seat unless the route takes you on the freeway.
In the Bay Area, there is someone in the driver’s seat at all times.
The platform was initially launched to those who were specifically invited to Austin to try it out.
Tesla confirms Robotaxi is heading to five new cities in the U.S.
Slowly, Tesla launched the platform to more people, hoping to expand the number of rides and get more valuable data on its performance in both regions to help local regulatory agencies relax some of the constraints that were placed on it.
Additionally, Tesla had its own in-house restrictions, like the presence of Safety Monitors in the vehicles. However, CEO Elon Musk has maintained that these monitors were present for safety reasons specifically, but revealed the plan was to remove them by the end of the year.
Now, Tesla is opening up Robotaxi to anyone who wants to try it, as many people reported today that they were able to access the app and immediately fetch a ride if they were in the area.
We also confirmed it ourselves, as it was shown that we could grab a ride in the Bay Area if we wanted to:
🚨 Tesla Robotaxi ride-hailing Service in Austin and the Bay Area has opened up for anyone on iOS
Go download the app and, if you’re in the area, hail a ride from Robotaxi pic.twitter.com/1CgzG0xk1J
— TESLARATI (@Teslarati) November 18, 2025
The launch of a more public Robotaxi network that allows anyone to access it seems to be a serious move of confidence by Tesla, as it is no longer confining the service to influencers who are handpicked by the company.
In the coming weeks, we expect Tesla to then rid these vehicles of the Safety Monitors as Musk predicted. If it can come through on that by the end of the year, the six-month period where Tesla went from launching Robotaxi to enabling driverless rides is incredibly impressive.
Tesla lands approval for Robotaxi operation in third U.S. state
Tesla ride-hailing Safety Monitor dozes off during Bay Area ride
