Amprius, the provider of the batteries for Airbus’ record-breaking Zephyr solar-powered stratospheric unmanned aircraft says it is working with electric vertical-takeoff-and-landing (eVTOL) developers on applications for its high energy-density lithium-ion cells. Where conventional lithium-ion batteries have graphite anodes and an energy density of 300-320 Wh/kg at best, Amprius’ cells use a silicon nanowire anode and have a specific energy of 435 Wh/kg. And according to Jon Bornstein, company president and COO, the difference is “enormous.” Such cells could enable Uber to meet its battery energy-density target, making its Elevate vision for eVTOL urban air taxis commercially feasible provided other key requirements such as adequate life and high charging and discharging rates can be met.

 
 
 
 
 
 
The Amprius cells helped enable the first production Zephyr S stratospheric UAV to stay aloft for almost 26 days in its first flight in July-August. This smashed the record of 14 days set in 2010 by the Zephyr 7 prototype, which used lithium-sulfur batteries.
Contracts to supply cells to Airbus for Zephyr will drive the production ramp-up this year. Amprius is focusing on the aerospace market and high-performance UAVs as it works to build up volume. “We are near to flying on something else, but Airbus is the furthest along with the Zephyr,” Bornstein says.
He admits that initial cells are “very expensive,” but as production volume grows he expects them to be close to cost parity with conventional lithium-ion cells by mid-2020s, when some believe the urban air mobility market will take off.