500 Wh/kg silicon battery packs extreme energy density for longer aircraft missions

Amprius Technologies has developed a lithium-ion battery cell that reaches 500 Wh/kg at a continuous 1C discharge rate. The company says the new SiCore cell can reach that figure using conventional battery manufacturing equipment. That combination could matter for aircraft where battery mass directly limits endurance. The cell uses a silicon anode to store more energy within the same battery weight. Amprius previously demonstrated cells above 500 Wh/kg, but those designs relied on specialized production methods. The new generation instead focuses on making that performance compatible with established lithium-ion manufacturing infrastructure. That could make the technology easier for aviation customers to qualify and scale. 500 Wh/kg production push Specific energy measures how much energy a battery stores relative to its mass. At 500 Wh/kg (about 227 Wh/lb), the new cell can store 500 watt-hours for every kilogram of battery weight. That figure becomes particularly useful aboard aircraft that must remain airborne for extended periods. High-altitude platform stations can spend days or even weeks operating far above conventional aircraft. Solar-powered HAPS aircraft face a particularly difficult energy problem. Their solar arrays generate power during daylight, but the aircraft still needs stored energy after sunset. A higher-energy battery can store more power without adding the same amount of mass. That could extend flight time or leave more weight available for payloads. The same advantage applies to fixed-wing drones and other long-endurance aircraft. Communications equipment, sensors, and observation systems all compete for limited payload capacity. The 1C rating also provides important context around the headline figure. It indicates the cell can continuously discharge at a rate equal to its rated capacity. Silicon anodes for aviation The technology has already found a place in high-altitude aviation through AALTO HAPS and its Zephyr aircraft. Amprius has supplied cells for the platform since 2018. A Zephyr aircraft reportedly remained airborne for 67 days in 2025, setting a world endurance record. AALTO is developing solar-electric HAPS aircraft for connectivity and Earth-observation missions. “Energy density is fundamental to Zephyr’s endurance,” said Pierre-Antoine Aubourg, AALTO HAPS chief operating officer. He also mentioned further improvements in specific energy could extend flight duration and expand mission capabilities. That makes the 500 Wh/kg milestone more significant than a laboratory specification alone. Aircraft designers can potentially use higher energy density without completely redesigning their battery production process. Volume production starts later Amprius expects commercial availability during the fourth quarter of 2026. Customers will receive cells in application-specific formats. The company also plans a standard pouch configuration for small uncrewed aircraft systems. That format follows SAE JA1016 specifications. Initial production will take place at Amprius’ Fremont, California, facility. Existing contract manufacturers could later support larger production volumes. The manufacturing strategy addresses one of the biggest hurdles for advanced battery technology. A cell can demonstrate exceptional performance in development, yet scaling that performance can require entirely different equipment.Second-generation SiCore aims to avoid that gap. Its 500 Wh/kg performance could therefore give long-endurance aircraft more stored energy without demanding a completely new manufacturing ecosystem.Get the latest in engineering, tech, space & science - delivered daily to your inbox.Aamir is a seasoned tech journalist with experience at Exhibit Magazine, Republic World, and PR Newswire. With a deep love for all things tech and science, he has spent years decoding the latest innovations and exploring how they shape industries, lifestyles, and the future of humanity.