AALTO Zephyr Achieves World-Record 67-Day Flight Powered by Amprius Ultra-High-Energy Batteries
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AALTO Zephyr Achieves World-Record 67-Day Flight Powered by Amprius Ultra-High-Energy Batteries
Amprius shipped high-energy batteries to several drone customers, including powering AALTO’s Zephyr aircraft during a record-breaking 67-day stratospheric flight, demonstrating unmatched endurance for persistent high-altitude missions.
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Amprius Ships New High-Performance 6.3Ah Silicon Anode Cylindrical Cell to Fortune 500 Company
Amprius Technologies
Amprius Technologies, Inc. (“Amprius” or the “Company”) (NYSE: AMPX), a leader in next-generation lithium-ion batteries with its Silicon Anode Platform, today announced it has shipped its new 6.3Ah 21700 SiCore™ cell to a Fortune 500 company in the Light Electric Vehicle (LEV) sector for evaluation. The new cell sets a new standard in the industry for energy density in this widely used format.
With an energy density of 315 Wh/kg, the 6.3Ah SiCore™ cell builds on Amprius’ proven technology, delivering over 25% more capacity than a standard 5.0Ah 21700 cell while maintaining a high-power 3C discharge rate. It achieves 800 cycles at 80% depth of discharge (DOD), extending battery lifespan and lowering replacement costs. Designed for seamless integration, its drop-in compatibility allows manufacturers to boost performance without the need for costly system redesigns.
“Our new 6.3Ah 21700 SiCore™ cell has attracted strong interest from leading OEM manufacturers because it delivers a significant improvement in battery performance,” said Dr. Ionel Stefan, CTO of Amprius Technologies. “With commercialization of this cell set for this year, we are excited to offer a high-capacity, long-lasting solution that meets the growing demand for more efficient energy storage solutions across multiple industries.”
While the initial focus for this 6.3Ah SiCore™ cell is on the LEV market, the high energy density and extended cycle life make it well-suited for a range of applications, including fixed wing aviation and AI applications such as robotics.
Amprius has secured manufacturing partnerships to support large-scale production, ensuring GWh-scale capacity to meet growing demand. As the need for high-performance energy storage continues to rise, Amprius remains focused on delivering advanced battery technology to power the future of electrification.
With an energy density of 315 Wh/kg, the 6.3Ah SiCore™ cell builds on Amprius’ proven technology, delivering over 25% more capacity than a standard 5.0Ah 21700 cell while maintaining a high-power 3C discharge rate. It achieves 800 cycles at 80% depth of discharge (DOD), extending battery lifespan and lowering replacement costs. Designed for seamless integration, its drop-in compatibility allows manufacturers to boost performance without the need for costly system redesigns.
“Our new 6.3Ah 21700 SiCore™ cell has attracted strong interest from leading OEM manufacturers because it delivers a significant improvement in battery performance,” said Dr. Ionel Stefan, CTO of Amprius Technologies. “With commercialization of this cell set for this year, we are excited to offer a high-capacity, long-lasting solution that meets the growing demand for more efficient energy storage solutions across multiple industries.”
While the initial focus for this 6.3Ah SiCore™ cell is on the LEV market, the high energy density and extended cycle life make it well-suited for a range of applications, including fixed wing aviation and AI applications such as robotics.
Amprius has secured manufacturing partnerships to support large-scale production, ensuring GWh-scale capacity to meet growing demand. As the need for high-performance energy storage continues to rise, Amprius remains focused on delivering advanced battery technology to power the future of electrification.
Amprius Launches SiCore™ 450 Wh/kg High-Energy Cell, with Near-Term Mass Production Capability to Sc
Amprius Technologies
Amprius Technologies, Inc. (“Amprius” or the “Company”) (NYSE: AMPX), a leader in next-generation lithium-ion batteries with its Silicon Anode Platform, today announced the launch of its 450 Wh/kg SiCore™ lithium-ion battery. This is Amprius’ most energy-dense SiCore™ cell, offering 450 Wh/kg and 950 Wh/L, and is expected to move to mass production in the near term through its global manufacturing partners.
Built with Amprius’ proprietary silicon anode material system, this SiCore™ cell delivers up to 80% more energy than conventional lithium-ion cells with graphite anodes. This enhanced energy density translates to extended flight time, greater range, and improved system-level performance, all within a compact, lightweight design.
“We’ve demonstrated what’s possible at 450 Wh/kg with our SiMaxx platform years ago,” said Dr. Kang Sun, CEO of Amprius Technologies. “What makes this SiCore™ cell different and noteworthy is that it brings that level of extreme performance into a cell chemistry and format that are ready to scale with the existing lithium-ion battery manufacturing processes and equipment in the industry. It’s production-ready, commercially available, and already being qualified by customers today.”
Designed for extreme conditions to meet the demands of aviation and defense applications, the new SiCore™ cell delivers reliable performance across wide temperature ranges and mission-critical environments. It meets the demands of High-Altitude Platform Stations (HAPS), Medium-Altitude Platform Stations (MAPS), and unmanned aerial vehicles (UAVs), where energy density, weight, and endurance directly impact mission success. By providing longer range and greater payloads without increasing weight, this cell helps reduce total system cost. This allows operators to fly longer missions with fewer compromises, minimizing the need for additional batteries, fuel, or equipment.
This SiCore™ cell is being evaluated with plans to move into qualification with leading aviation and defense customers preparing for commercial deployment. To meet their demand, Amprius has built a global contract manufacturing network with gigawatt-hour-scale production capacity, ensuring the Company can deliver these high-performance cells at a competitive cost.
UN38.3 certification, which is required for the safe air transport of lithium-ion batteries, is expected in this quarter for this cell. This will allow Amprius to begin volume shipments shortly afterward and support broader commercial deployment worldwide.
The commercial launch of the 450 Wh/kg SiCore™ cell follows the broader introduction of Amprius’ SiCore™ platform in January 2024. That announcement marked the debut of a new generation of silicon anode cells engineered for both high energy and high power in a single format. With the latest 450 Wh/kg cell now entering production, SiCore™ is positioned to support a wide range of high-demand applications across electric aviation, defense, and mobility markets.
For more information, please visit the Amprius investor relations website at ir.amprius.com.
Built with Amprius’ proprietary silicon anode material system, this SiCore™ cell delivers up to 80% more energy than conventional lithium-ion cells with graphite anodes. This enhanced energy density translates to extended flight time, greater range, and improved system-level performance, all within a compact, lightweight design.
“We’ve demonstrated what’s possible at 450 Wh/kg with our SiMaxx platform years ago,” said Dr. Kang Sun, CEO of Amprius Technologies. “What makes this SiCore™ cell different and noteworthy is that it brings that level of extreme performance into a cell chemistry and format that are ready to scale with the existing lithium-ion battery manufacturing processes and equipment in the industry. It’s production-ready, commercially available, and already being qualified by customers today.”
Designed for extreme conditions to meet the demands of aviation and defense applications, the new SiCore™ cell delivers reliable performance across wide temperature ranges and mission-critical environments. It meets the demands of High-Altitude Platform Stations (HAPS), Medium-Altitude Platform Stations (MAPS), and unmanned aerial vehicles (UAVs), where energy density, weight, and endurance directly impact mission success. By providing longer range and greater payloads without increasing weight, this cell helps reduce total system cost. This allows operators to fly longer missions with fewer compromises, minimizing the need for additional batteries, fuel, or equipment.
This SiCore™ cell is being evaluated with plans to move into qualification with leading aviation and defense customers preparing for commercial deployment. To meet their demand, Amprius has built a global contract manufacturing network with gigawatt-hour-scale production capacity, ensuring the Company can deliver these high-performance cells at a competitive cost.
UN38.3 certification, which is required for the safe air transport of lithium-ion batteries, is expected in this quarter for this cell. This will allow Amprius to begin volume shipments shortly afterward and support broader commercial deployment worldwide.
The commercial launch of the 450 Wh/kg SiCore™ cell follows the broader introduction of Amprius’ SiCore™ platform in January 2024. That announcement marked the debut of a new generation of silicon anode cells engineered for both high energy and high power in a single format. With the latest 450 Wh/kg cell now entering production, SiCore™ is positioned to support a wide range of high-demand applications across electric aviation, defense, and mobility markets.
For more information, please visit the Amprius investor relations website at ir.amprius.com.
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Amprius Technologies, Inc. (“Amprius” or the “Company”) (NYSE: AMPX), a leader in next-generation lithium-ion battery technology, today announced that its silicon anode batteries powered AALTO’s Zephyr high-altitude pseudo-satellite (HAPS) aircraft during a world-record-setting 67-day flight in the stratosphere, which concluded on April 28, 2025. This uninterrupted flight, conducted at altitudes around 70,000 feet, surpassed Zephyr’s previous endurance record of 64 days and marks the longest continuous aircraft flight ever recorded.
The Zephyr is a solar-powered unmanned aerial vehicle that operates in the stratosphere, charging its batteries during the day via solar panels and relying on battery power overnight. Amprius’ ultra-high-energy-density lithium-ion cells provided the critical energy storage needed to keep the Zephyr flying through multi-night cycles in the thin air of the stratosphere. By enabling reliable overnight power, these silicon anode batteries were a key factor in the mission’s success, allowing the aircraft to maintain continuous operation for over two months. Amprius’ cells are among the only commercially available batteries known that are capable of delivering the required endurance for persistent HAPS missions, a capability that was essential for Zephyr’s day-and-night flight longevity.
This achievement was made possible through the close collaboration between Amprius and AALTO HAPS (“AALTO”), a U.K.-based Airbus subsidiary that designs, manufactures, and operates Zephyr. Amprius has been a key supplier of high-performance batteries to AALTO for several years, including for a 2022 Zephyr flight that lasted 64 days. The new 67-day flight builds on that milestone, further proving the reliability of Amprius’ technology and the Zephyr system’s ability to push the limits of aviation endurance.
“We are extremely proud to see our batteries enable this groundbreaking 67-day flight,” said Dr. Kang Sun, CEO of Amprius Technologies. “This accomplishment demonstrates the transformative impact of our silicon anode battery technology in aerospace. By providing the energy needed to keep Zephyr flying through the night, our silicon anode cells made it possible to achieve a new level of endurance for stratospheric aircraft. We are honored to partner with AALTO in pushing the boundaries of what high-altitude platforms can do for both commercial and defense applications.”
“Achieving this 67-day flight is a major milestone for Zephyr and HAPS technology more widely,” said Pierre-Antoine Aubourg, Chief Technical Officer at AALTO. “Amprius’ high-energy batteries provided the reliable power storage we needed to maintain Zephyr’s day and night operations. Their technology was instrumental in enabling us to break our own endurance record, demonstrating that persistent stratospheric missions and capabilities are now a reality. We look forward to continuing our collaboration with Amprius as we focus on our remaining flight program for 2025.”
The record-breaking flight underscores the potential of high-altitude pseudo-satellite platforms for both commercial and defense applications. Operating at roughly 70,000 feet, the Zephyr can fly for months at a time, effectively combining the persistence of a satellite with the flexibility of an unmanned aerial vehicle. This capability opens the door for missions such as continuous border surveillance, secure communications relay, and environmental monitoring that require long-term, persistent coverage. Such ultra-long endurance is especially valuable for defense, where HAPS vehicles like Zephyr can provide persistent ISR (intelligence, surveillance, and reconnaissance) and connectivity over critical areas without interruption.
For more information, please visit the Amprius investor relations website at ir.amprius.com.
The Zephyr is a solar-powered unmanned aerial vehicle that operates in the stratosphere, charging its batteries during the day via solar panels and relying on battery power overnight. Amprius’ ultra-high-energy-density lithium-ion cells provided the critical energy storage needed to keep the Zephyr flying through multi-night cycles in the thin air of the stratosphere. By enabling reliable overnight power, these silicon anode batteries were a key factor in the mission’s success, allowing the aircraft to maintain continuous operation for over two months. Amprius’ cells are among the only commercially available batteries known that are capable of delivering the required endurance for persistent HAPS missions, a capability that was essential for Zephyr’s day-and-night flight longevity.
This achievement was made possible through the close collaboration between Amprius and AALTO HAPS (“AALTO”), a U.K.-based Airbus subsidiary that designs, manufactures, and operates Zephyr. Amprius has been a key supplier of high-performance batteries to AALTO for several years, including for a 2022 Zephyr flight that lasted 64 days. The new 67-day flight builds on that milestone, further proving the reliability of Amprius’ technology and the Zephyr system’s ability to push the limits of aviation endurance.
“We are extremely proud to see our batteries enable this groundbreaking 67-day flight,” said Dr. Kang Sun, CEO of Amprius Technologies. “This accomplishment demonstrates the transformative impact of our silicon anode battery technology in aerospace. By providing the energy needed to keep Zephyr flying through the night, our silicon anode cells made it possible to achieve a new level of endurance for stratospheric aircraft. We are honored to partner with AALTO in pushing the boundaries of what high-altitude platforms can do for both commercial and defense applications.”
“Achieving this 67-day flight is a major milestone for Zephyr and HAPS technology more widely,” said Pierre-Antoine Aubourg, Chief Technical Officer at AALTO. “Amprius’ high-energy batteries provided the reliable power storage we needed to maintain Zephyr’s day and night operations. Their technology was instrumental in enabling us to break our own endurance record, demonstrating that persistent stratospheric missions and capabilities are now a reality. We look forward to continuing our collaboration with Amprius as we focus on our remaining flight program for 2025.”
The record-breaking flight underscores the potential of high-altitude pseudo-satellite platforms for both commercial and defense applications. Operating at roughly 70,000 feet, the Zephyr can fly for months at a time, effectively combining the persistence of a satellite with the flexibility of an unmanned aerial vehicle. This capability opens the door for missions such as continuous border surveillance, secure communications relay, and environmental monitoring that require long-term, persistent coverage. Such ultra-long endurance is especially valuable for defense, where HAPS vehicles like Zephyr can provide persistent ISR (intelligence, surveillance, and reconnaissance) and connectivity over critical areas without interruption.
For more information, please visit the Amprius investor relations website at ir.amprius.com.
