Amprius Secures Multiple Purchase Orders from AALTO for SiMaxx™ 450 Wh/kg High-Energy Cells to Continue Record-Breaking Flights

Custom Battery Cells Provide Unparalleled Energy Density for Stratospheric HAPS Applications

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 signed purchase orders from AALTO HAPS (“AALTO”) for the Company’s 450 Wh/kg ultra-high-energy density SiMaxxTM cells.

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Amprius Secures Multiple Purchase Orders from AALTO for SiMaxx™ 450 Wh/kg High-Energy Cells to Continue Record-Breaking Flights (Photo: Business Wire)

Amprius Secures Multiple Purchase Orders from AALTO for SiMaxx™ 450 Wh/kg High-Energy Cells to Continue Record-Breaking Flights (Photo: Business Wire)

Amprius’ 450 Wh/kg SiMaxx cells are designed to operate in some of the most extreme flight conditions while maximizing flight range and payload capacity. These attributes make SiMaxx cells the only known commercially available batteries capable of supplying enough endurance for persistent HAPS (High-Altitude Platform Stations) overnight stratospheric flight operations in all seasons or at higher latitudes. This is a key consideration for AALTO, with Zephyr the only fixed-wing HAPS to have demonstrated day and night longevity in the stratosphere.

“Amprius is at the forefront of enabling electric flight with our high-energy density cells designed to improve aircraft range while reducing weight,” said Dr. Kang Sun, CEO of Amprius Technologies. “AALTO is one of Amprius’ long-standing customers, and we look forward to continuing to support its world record high-altitude pseudo satellite missions with our high-energy density cells.”

The collaborative efforts between AALTO and Amprius reached a milestone in 2022 with a record-breaking 64-day cross-continental test flight of a Zephyr 8/S, a monumental achievement for both companies. During the event, Amprius’ 400 Wh/kg high-energy cells powered the flight without descending from the stratosphere, allowing AALTO to break its own previous record of more than 25 days.

Pierre-Antoine Aubourg, Chief Technical Officer at AALTO, said: “Zephyr relies on the most cutting-edge sustainable technology and design to push the boundaries of solar-powered, stratospheric flight. In Amprius, AALTO has a highly valued partner that continues to produce ultra-high-energy density batteries that are critical to our success, enabling improvements in nighttime operations as well as the extent of coverage latitude. It is a partnership that will remain highly strategic for both companies over the coming years.”

Amprius’ SiMaxx cells are equipped to operate in challenging environments and are, therefore, ideally suited for aviation and military applications. Amprius began fulfilling shipments against the new AALTO purchase orders in Q1 of 2024 and expects to continue fulfilling shipments in the coming months as the Company advances its efforts to increase its SiMaxx production capacity in Fremont, CA.

For more information on Amprius, please visit the Company’s investor relations website at

About Amprius Technologies, Inc.

Amprius Technologies, Inc. is a leading manufacturer of high-energy and high-power lithium-ion batteries producing the industry’s highest known energy density cells. The company’s commercially available SiMaxx™ batteries deliver up to 450 Wh/kg and 1,150 Wh/L, with third-party validation of 500Wh/kg and 1,300 Wh/L. The company’s corporate headquarters is in Fremont, California, where it maintains an R&D lab and a MWh scale manufacturing facility for the fabrication of silicon anodes and cells. To serve customer demand, Amprius entered into a lease agreement for an approximately 774,000 square foot facility in Brighton, Colorado and expanded its product portfolio to include the SiCore™ platform. For additional information, please visit Also, see the company’s LinkedIn and Twitter pages.


AALTO is a 100%-owned spin-off of Airbus that is a global leader in the stratosphere. Based in Farnborough, UK, the Company designs, manufactures and offers services using its record-breaking Zephyr high altitude platform station. Powered entirely by solar energy and operating above 60,000+ feet, Zephyr’s persistence enables continuous flight for months at a time. Its current flight-time record is over 64 days in the stratosphere. As a payload agnostic platform, Zephyr can deliver several applications, including high-quality earth observation or direct-to-device connectivity services. For further information, please visit

Forward Looking Statements

This press release includes “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, each as amended. Forward-looking statements may be identified by the use of words such as “estimate,” “plan,” “project,” “forecast,” “intend,” “expect,” “anticipate,” “believe,” “seek” or other similar expressions that predict or indicate future events or trends or that are not statements of historical matters. These forward-looking statements include, but are not limited to, statements regarding the performance, potential applications and addressable market of Amprius’ batteries, and the ability of Amprius to increase its manufacturing capacity and fulfill customers’ orders. These statements are based on various assumptions, whether or not identified in this press release, and on the current expectations of Amprius’ management and are not predictions of actual performance. Actual results could differ materially from these forward-looking statements as a result of certain risks and uncertainties. These forward-looking statements are subject to a number of risks and uncertainties, including delays in permitting, construction and operation of production facilities; Amprius’ liquidity position; risks related to the rollout of Amprius’ business and the timing of expected business milestones; Amprius’ ability to commercially produce high performing batteries; the effects of competition on Amprius’ business; supply shortages in the materials necessary for the production of Amprius batteries; and changes in domestic and foreign business, market, financial, political and legal conditions. For more information on these risks and uncertainties that may impact the operations and projections discussed herein can be found in the documents we filed from time to time with the Securities and Exchange Commission (the “SEC”), all of which are available on the SEC’s website at There may be additional risks that Amprius does not presently know or that Amprius currently believes are immaterial that could also cause actual results to differ from those contained in the forward-looking statements. In addition, forward-looking statements reflect Amprius’ expectations, plans or forecasts of future events and views as of the date of this press release. These forward-looking statements should not be relied upon as representing Amprius’ assessments as of any date subsequent to the date of this press release. Accordingly, undue reliance should not be placed upon the forward-looking statements. Except as required by law, Amprius specifically disclaims any obligation to update any forward-looking statements.


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