Amprius Batteries Boost Energy for Long-endurance Drones

Amprius Technologies plans to begin selling a 500 Wh/kg silicon-anode battery cell in the fourth quarter of this year, the first time the company has offered its highest energy density on a cell that outside factories can build with standard lithium-ion equipment.

The second-generation SiCore cell delivers 500 Wh/kg at a 1C continuous discharge rate, Fremont, California-based Amprius said on September 2. That rate suits the slow, sustained draw of high-altitude pseudo-satellites (HAPS) and fixed-wing drones rather than the power-intensive takeoff and climb profiles of larger eVTOL aircraft.

Amprius already makes 500 Wh/kg cells under its SiMaxx line, but those depend on specialized processes the company runs in-house at Fremont in limited volume. SiCore, which launched in 2024 at 370 Wh/kg and reached 450 Wh/kg in April 2025, costs less because contract manufacturers can produce it on existing lines. Pushing that platform to 500 Wh/kg closes the gap between the two families.

Since 2018, Amprius has supplied cells to Airbus subsidiary Aalto for its solar-powered Zephyr aircraft, which flew for 67 days in 2025. “Continued gains in specific energy can meaningfully extend flight duration and expand mission capability,” said Aalto chief operating officer Pierre-Antoine Aubourg.

Other drone makers have signed on as well. Empirical Systems Aerospace of San Luis Obispo, California, qualified the SiCore SA08 cell for its Group 1 and Group 2 drones last October, and Nokia picked SiCore in December for its 5G-connected “drone-in-a-box” platform for industrial inspection and public safety. Matternet’s type-certified M2 delivery drone already uses Amprius cells, and in May the two companies agreed to develop a battery for Matternet’s next aircraft, targeting volume production in early 2027.

Military demand is fueling the company’s growth. Amprius counts AeroVironment, BAE Systems, L3Harris, Teledyne FLIR, and the U.S. Army among its customers, and shipments to Ukraine accounted for $10.4 million of second-quarter sales. Revenue for the quarter reached $34 million, more than double the $15.1 million Amprius posted a year earlier, against a net loss of $3.2 million. An unnamed drone manufacturer that placed a $15 million order for SiCore cells in February 2025 came back in September with a $35 million follow-on order.

Most of Amprius’ battery cells come from contract manufacturers in China and South Korea, where the company recently launched the Amprius Korea Battery Alliance. That network gives Amprius access to more than 2 GWh of annual capacity. To serve customers that require domestic sourcing, Amprius named Nanotech Energy its first U.S. contract manufacturer in February.

In August, U.S. President Donald Trump announced tariffs of up to 100% on Chinese drones and components. However, the White House did not specify whether the new import charges would apply to batteries made in China.