Aircraft

Purpose-built eVTOL battery promises 50-mile trips on a 10-minute charge

Purpose-built eVTOL battery pr...
An artist's impression of an eVTOL aircraft preparing for takeoff
An artist's impression of an eVTOL aircraft preparing for takeoff
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An artist's impression of an eVTOL aircraft preparing for takeoff
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An artist's impression of an eVTOL aircraft preparing for takeoff

Lithium-ion batteries do a great job of powering smartphones, laptops and even cars, but electric flight presents some unique challenges for this go-to solution for energy storage. Scientists have now demonstrated a new type of lithium-battery that leverages an innovative high-temperature charging technology to give it enough juice for meaningful aerial trips in just five to 10 minutes.

The reason using electrical powertrains and batteries for flight is so difficult as opposed to, say, powering a car down a highway, is because all of that heavy gear needs to be hauled into the air. There are limitations to how much energy a battery can store and still be light enough for the aircraft to take off, which pales in comparison to the energy density offered by traditional, kerosene-based jet fuel.

Making these batteries able to carry more energy per kilogram is one of the key challenges facing the electric aviation industry, though there are other factors to consider, too. These include fast charging times to keep the vehicles on the move and avoid inefficient battery swaps, and equipping those batteries with the ability to deliver the required amounts of power.

"Batteries for flying cars need very high energy density so that you can stay in the air," says Chao-Yang Wang, a mechanical engineer at Pennsylvania State University and author of the study. "And they also need very high power during take-off and landing. It requires a lot of power to go vertically up and down."

The new technology demonstrated by Wang and his colleagues actually builds on an experimental battery they developed a couple of years ago. Traditionally, lithium batteries can only operate safely within a certain temperature range. Too cold, and spikes will form on the anode in a process known as lithium plating, while too hot and the battery will quickly degrade.

The researchers were able to find a way around this with a unique design that uses a thin nickel foil attached to the negative terminal, which can rapidly heat up the battery to 60 °C (140 °F) in 30 seconds. The battery only remains at this temperature for 10 minutes, before being quickly cooled again.

This is enough to take advantage of the higher charging efficiencies offered by higher operating temperatures, but avoids degradation and lithium plating. In 2019, the scientists demonstrated this by building a prototype battery that could charge an electric car in 10 minutes to offer a range of up to 300 miles (480 km), and they've now tailored the technology for eVTOL (electric vertical takeoff and landing) aircraft.

The team says the new experimental batteries have the required density to power an eVTOL aircraft over a 50-mile (80-km) journey, but can be recharged in five to 10 minutes thanks to the high-temperature charging technology. Demonstrating the longevity of the design, the team also showed that this performance can be sustained over 2,000 fast-charging cycles.

"Under normal circumstances, the three attributes necessary for an eVTOL battery work against each other," says Wang. "High energy density reduces fast charging and fast charging usually reduces the number of possible recharge cycles. But we are able to do all three in a single battery."

The battery built by the team is not about to be dropped into a flying taxi ready for take-off. Rather, its development was a way of gauging the unique battery requirements for this type of transport, which will involve frequent take-offs and landings and a whole lot of recharging, and lay the groundwork for technologies that combine them in a feasible way.

"I hope that the work we have done in this paper will give people a solid idea that we don't need another 20 years to finally get these vehicles," says Wang. "I believe we have demonstrated that the eVTOL is commercially viable."

The research was published in the journal Joule.

Source: Pennsylvania State University

7 comments
7 comments
Arcticshade
The Evtol market is screaming to explode into everyday life, a step forward for this to becoming a reality, well done to Wang and his colleagues!
DaveWesely
I don't understand this fascination with flying cars. It makes good copy, but there isn't much reality involved. If they were that much in demand, many more people would be piloting traditional small aircraft. They don't because of the expense and training to alleviate the safety issues involved.
Towerman
I'm sure Wang meant flying EVTOL's. Flying cars will never really be a serious contender. There is always a compromise of weight vs aerodynamics on a flying car.

EVTOL's on the other hand has got the edge in the aviation industry and the demand for these vehicles are high and will skyrocket once regulations catch up with it.
jerryd
I own 7 yr old battery modules/ Volt EV, that can easily charge in 10 minutes without making much heat.
The big problem is the craft they are putting the batteries in. It seems like they are trying to find every way they can that won't be viable, especially multicopters, other complicated systems.
Simple 2 rotors like the Mars Helicopter is dead simple, cheap and wilding more efficient and dynamically stable, no computers needed. Other STOL that can take off, land in 100' is another viable simple low cost way. Mostly a regular plane with 3x the power to leap in the air and low aspect ratio to float into for a landing. A Parasol or Gyro wings style works nicely.
The key to this future is lightness, simplicity, efficiency. KISS
Karmudjun
Oh yes, there are more reasons against this use for a rapidly charging battery that has resulted in a "Proof of concept" publication than reasons for it. While EVTOL is an exciting use for these batteries - there is one very significant concern that requires another paper with "Proof of Concept". Say a company is providing EVTOL transport for corporate executives from their corporate offices to an airport (10 minute flight?) with response time like taxi service (15-20 minutes from booking), how can the batteries get charged? How much power will need to be diverted to complete a 10 minute charge in one small location? 10KW? 50KW for 10 minutes? 100KW for 10 minutes?

Bill Gates had better get that small nuclear reactor technology off the ground pretty quick as it will take that kind of generating power in the basement to charge such a vehicle on the roof!
Towerman
@jerryd

Except for that a counter rotator that you imply is not simple at all, EVTOLs is the revolution/next stage of the helicopter and works with a seamlessly integrated system to provide superior flight characteristics where the system reacts in less than miliseconds.

And its reliable technology is KISS at its best, a complicated system which is mechanically superior in simplicity, the perfect power package.

Your 7 year old battery is outdated sorry, update yourself or get lost in your cave EVTOLS have got the edge and are here to stay and revolutionize flight.
Towerman
@Karmudjun

Its already been done, and you ask the same lame beaten down questions more to the tune of right wing politics than revolutionized technology.

There will be enough power, gradually the world will be updated to support the EVTOL system via integrated infrastructure one step at a time.