US battery developer Amprius Technologies has introduced a second-generation SiCore lithium-ion cell claimed to deliver a specific energy of 500Wh/kg at a continuous discharge rate of 1C.
The silicon-anode cell has been designed for long-endurance aviation applications, including high-altitude platform stations (HAPS), fixed-wing drones and other uncrewed aircraft.
Amprius said the cell could be manufactured using conventional lithium-ion equipment, processes and cell formats. Its previous cells exceeding 500Wh/kg required specialised production processes and were not manufactured commercially at volume.
Initial production is planned at the company’s pilot facility in Fremont, California. Volume manufacturing is expected to be handled by Amprius’s existing network of contract manufacturing partners.
Commercial availability is scheduled for the fourth quarter of 2026. Cells will be offered in customer-specific formats and in the standard pouch format covered by SAE JA1016, a recommended practice establishing dimensions, test procedures and reporting requirements for rechargeable pouch cells used in Group 1 small uncrewed aerial vehicles.
Amprius chief technology officer Ionel Stefan said: “Reaching 500Wh/kg is a significant technical milestone, but how we reached it matters as much as the number.
“By achieving that performance level on conventional manufacturing equipment, our aviation customers can qualify this cell knowing that we have designed a cost-effective, scalable path to volume behind it.”
The company said the SiCore500 had been optimised for sustained, relatively low-rate discharge. In solar-powered HAPS aircraft, batteries store energy collected during daylight for propulsion and other loads overnight, making specific energy an important determinant of endurance and payload capacity.
Amprius has supplied cells to Airbus subsidiary AALTO HAPS since 2018 for successive generations of its solar-electric Zephyr aircraft. Zephyr completed a flight lasting 67 days, six hours and 52 minutes in April 2025, which AALTO described as a world endurance record.
AALTO chief operating officer Pierre-Antoine Aubourg said: “Energy density is fundamental to Zephyr’s endurance. Our longstanding relationship with Amprius has focused on advancing the energy storage required for persistent stratospheric flight. Continued gains in specific energy can meaningfully extend flight duration and expand mission capability.”
Amprius has not disclosed the new cell’s capacity, volumetric energy density, cycle life, charging rate or dimensions. Its existing commercially available SiCore range reaches up to 450Wh/kg, according to the company.
