December 5, 2018 — Using Amprius’ cells, which contain a 100% silicon anode, the Zephyr S flew more than 25 days, setting a new endurance and altitude record for stratospheric flight.

January 6, 2014 — Since 2008, Silicon Valley startup Amprius has been working on a multi-pronged effort in next-generation energy storage technology — using silicon, rather than carbon, as a material for the electrodes within lithium-ion batteries.