Today’s Tesla Model 3’s lithium-ion battery pack has an estimated 168 Wh/kg. And important as this energy-per-weight ratio is for electric cars, it’s more important still for electric aircraft.
Now comes Oxis Energy, of Abingdon, UK, with a battery based on lithium-sulfur chemistry that it says can greatly increase the ratio, and do so in a product that’s safe enough for use even in an electric airplane. Specifically, a plane built by Bye Aerospace, in Englewood, Colo., whose founder, George Bye, described the project in this 2017 article for IEEE Spectrum.
The two companies said in a statement that they were beginning a one-year joint project to demonstrate feasibility. They said the Oxis battery would provide “in excess” of 500 Wh/kg, a number which appears to apply to the individual cells, rather than the battery pack, with all its packaging, power electronics, and other paraphernalia. That per-cell figure may be compared directly to the “record-breaking energy density of 260 watt-hours per kilogram” that Bye cited for the batteries his planes were using in 2017.
One reason why lithium-sulfur batteries have been on the sidelines for so long is their short life, due to degradation of the cathode during the charge-discharge cycle. Oxis expects its batteries will be able to last for 500 such cycles within the next two years. That’s about par for the course for today’s lithium-ion batteries.
Another reason is safety: Lithium-sulfur batteries have been prone to overheating. Oxis says its design incorporates a ceramic lithium sulfide as a “passivation layer,” which blocks the flow of electricity—both to prevent sudden discharge and the more insidious leakage that can cause a lithium-ion battery to slowly lose capacity even while just sitting on a shelf. Oxis also uses a non-flammable electrolyte.
Presumably there is more to Oxis’s secret sauce than these two elements: The company says it has 186 patents, with 87 more pending.
But is it recyclable? See: non toxic recyclable Aluminium Air battery with nine times more density than li-ion batteries finally entering production. Tech has been around since around 1999, Navy veteran refused to accept a ‘no’ to his battery invention
Which is also clean, green technology.