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Aircraft

Ultra-dense lithium-sulfur battery doubles range of electric planes

By Loz Blain
November 12, 2019
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Bye Aerospace will be using high-density lithium-sulfur batteries from Oxis
Bye Aerospace
Bye Aerospace will be using high-density lithium-sulfur batteries from Oxis
Bye Aerospace

British company Oxis Energy believes its high capacity lithium-sulfur batteries, which hold up to five times more energy per weight than lithium-ion cells, are ready to vastly increase the range of electric aircraft.

The world is crying out for real electric aviation options, but as yet, existing lithium-ion cells are so heavy that they're not practical for much more than short journeys. Density is the key, and with leading commercial Li-ion cells still only storing around 250 Wh/kg (in Tesla's 2170 cells, used in the Model 3), everyone's waiting on new cell chemistries that offer higher densities while still remaining reliable and safe.

Or perhaps, in this case, something older. Lithium-sulfur batteries have been around since the 1960s, and have long been known for their relatively high energy density and low cost. The letdown has been cycle life; lithium polysulfides are quite soluble in the electrolytes used in batteries, meaning that the cathode eventually melts away over time.

Oxis says it's developed a "safe," non-flammable electrolyte that preserves the lithium metal for longer. Its ultra-light pouch cells are already delivering energy densities over 500 Wh/kg, proving safe despite punctures and bullet holes, and lasting some 250 charge cycles. The company believes it can extend this past 500 cycles within a couple of years' development, which is ballpark for what a lot of current Li-ion cells are good for, and representative of an electric car battery that might last 300-500,000 miles. Tesla, meanwhile, is pushing for million-mile cells.

Still, at 500 Wh/kg, the Oxis gear offers genuine utility in electric aviation, and Oxis has started a collaborative deal with Bye Aerospace, a Colorado-based company specializing in electric and solar aircraft. Bye says that the Oxis tech will improve the flight times on its future aircraft between 50 and 100 percent. A successful implementation here could see larger aircraft companies getting interested, although with all battery advances there's always the fear that some new technology will come down the tube and blitz it within five years.

Oxis is preparing to build manufacturing plants in Brazil and Wales, and is hoping its cells might make a good match for electric buses in Brazil's bus-heavy public transport mix.

Source: Oxis Energy via IEEE Spectrum

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Loz Blain
Loz leads the New Atlas team as Editorial Director, after nearly two decades as one of our most versatile writers. He's also proven himself as a photographer, videographer, presenter, producer and podcast engineer. A graduate in Psychology, former business analyst and touring musician, he's covered just about everything for New Atlas, concentrating lately on clean energy, AI, humanoid robotics, next-gen aircraft, and the odd bit of music, motorcycles and automotive.
10 comments
clay
It is exciting to consider legitimate electric aircraft. That said, I cannot help to be skeptical of this report because it uses advertiser-esc terms like "up to five times more energy", referencing Tesla's 250Wh/kg and then follows shortly with a figure of 500Wh/kg.. this is clearly 2x (when not using my doublespeak translator) :-)

The other concern that jumps out is that *VERY LOW* 250 cycle-life rating. That number is arguably more significant than the energy density number. Sure, density determines range, but here's the thing: cycle life is going to drive the operating cost of this kind of aircraft.

I wish them luck, after all, you gotta walk before ya run.. And these guys seem to be walking at a brisk pace! :-)
paul314
So what's the replacement/recycling situation on those batteries? If the material could be reclaimed and remanufactured, it could be a maintenance issue lie any other. That sounds like about a year between replacements, and if you think about some of the things jet aircraft go through in terms of maintenance/replacement on an annual basis, new battery packs might not be such a dealbreaker.
eMacPaul
I agree with clay, 500 charge cycles doesn't seem like that much, unless the battery is very inexpensive and easy to replace. For a car, if you get 300 miles per full charge, that gives you 150,000 miles, which isn't too bad. But for an airplane, particularly at a flight school (which is where electric airplanes are currently mainly targeted), you'd be looking at replacing the batteries every couple years. Although, again, if it's not too expensive or hard to replace, the cost savings over av gas could mean it's still a good deal.
christopher
Sounds like a perfect fit for recreational aircraft. Most of those probably never do 250 flights in their life anyhow.
Tord Eriksson
The problem with electric power is two-fold: Battery energy density and cycle length. These promising batteries are abysmal when it comes to the number of cycles before they need replacing, but they are promising when it comes to energy density.

The great question is which airline company wants to change their batteries after 250 cycles, something that surely will mean a loss in revenue?! Possibly a great battery for business aircraft, as then the shedule isn't as hectic as for a revenue-earning airliner.
GD
Interesting. How do the batteries degrade with use? Hopefully in a predictable linear way, so that the aircraft's logbook can be updated with the latest maximum range or endurance.
Mzungu_Mkubwa
There are so many recent "breakthroughs" being reported in battery tech, its hard to know which might be legit and which are propaganda. For example this quote from phys.org: "In their third study, the scientists used a similar potassium-sodium alloy applied on carbon paper as an anode and the redox-active polymers obtained earlier as cathodes. Such batteries can be charged-discharged in less than 10 seconds. Interestingly, one of the polymer cathodes exhibited the highest energy capacity for potassium batteries, while the other showed excellent stability, with only 11 percent of capacity lost after 10,000 charge/discharge cycles. Also, the batteries based on these two materials displayed unrivaled power characteristics of nearly 100,000 W/kg, a level typical for supercapacitors." Just sounds too good to be true, to me. (reference link: https://phys.org/news/2019-11-scientists-superfast-charging-high-capacity-potassium-batteries.html ) So much of this is extremely complex, so is "dumbed-down" to convey to us laymen readers.
Towerman
@Mzungu_Mkubwa


I agree there are 100s if not 1000s of "breakthroughs" but nothing gets to be a solid product, it's quite the circus.

On the other hand why not ditch lithium or any battery for that matter for good and go supercap ! Lamborhini has a record of consistency when it comes to make difficult engineering possible, and this time they are utilizing supercapacitors in the most powerful supercar ever: https://www.greencarreports.com/news/1124923_lamborghini-uses-supercapacitors-in-its-most-powerful-car-ever

Supercaps IS the FUTURE !
michael_dowling
Towerman: Supercaps will never replace Li-ion batteries,as their storage capacity is very small,but combining supercaps with Li-ion is a marriage made in heaven. The supercaps can dump huge amounts of power into the motor(s) for quick acceleration while the batteries job is made easier by being available mainly for cruising. That is probably what is behind Tesla's purchase of Maxwell Technologies.
Towerman
@michael_dowling: That is only true for the current supercaps in existence. Like i said, Lamborghini has a habit of making impossible engineering possible because they are persistent and demanding, have a look at their engineering history and you will see what i am talking about. They don't stop until it works and work extremely well. So Supercaps will replace lithium if a company such as Lambo is making fire under those developing it, its not going to be here tomorrow but i truly believe in a few years time it would be possible, and that would be revolutionary. Currently its doing a great job of providing bursts to extremely power hungry situations, gradually capacity will increase to replace lithium.
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