Solid-state battery shows 2% loss after 434 days

NASA said on May 21 that a battery pack built from all-solid-state lithium-ion cells kept operating after 434 days in space, part of a set of International Space Station research results the agency highlighted this week. NASA’s annual ISS research roundup said the pack was assembled in orbit and exposed to space to measure performance, degradation and radiation response. The agency said the test was aimed at future long-duration exploration missions, including the Moon and Mars. A peer-reviewed paper published in the journal *Aerospace* on June 6, 2025 described the same experiment in more technical detail. The paper, led by Yu Miyazawa of the Japan Aerospace Exploration Agency, said the battery was mounted in the ISS exposed section for 434 days and underwent 562 charge-discharge cycles, with no significant degradation in charge-discharge characteristics or visible battery appearance. (nasa.gov) ### Where did the “2% loss” figure come from? NASA’s May 21 highlights page said the battery pack showed only about 2% capacity loss after 434 days in space. The agency included that result in a section titled “Power that endures,” alongside other ISS research findings from 2025. The *Aerospace* paper’s abstract did not state the 2% figure in the excerpt available through search results, but it did say researchers saw no significant degradation after the 434-day exposure and 562 test cycles. (mdpi.com) That means the 2% figure appears to come from NASA’s summary of the underlying results rather than from the short abstract text surfaced in search. (nasa.gov) ### Who ran the experiment? The June 2025 paper listed authors from the Japan Aerospace Exploration Agency and Kanadevia Corporation, formerly known as Hitachi Zosen. Yu Miyazawa and Hitoshi Naito were listed as corresponding authors. NASA’s role in the current news item was to feature the result in its ISS annual highlights page rather than to claim authorship of the battery study itself. The study focused on all-solid-state lithium-ion batteries, often shortened to ASSBs. (nasa.gov) The paper said those batteries have a wide operating temperature range of minus 40 degrees Celsius to plus 120 degrees Celsius and are being considered for lunar exploration and, in longer-term planning, Mars missions. ### Why test this kind of battery outside the station? The June 2025 paper said ground testing had already suggested the batteries could tolerate the space environment, and the ISS experiment was designed as a space demonstration. (mdpi.com) Researchers placed the hardware in the station’s exposed section, where it could face the combined effects of vacuum, temperature swings and radiation over an extended period. NASA’s May 21 summary said the test tracked performance, degradation and radiation response. The agency said the result supports the use of durable power systems for long-duration missions, while the paper said the findings encouraged possible use of the batteries in space exploration. ### What does the result add to space-mission planning? (mdpi.com) The paper said one conclusion was that lifetime characteristics for these batteries could be estimated from ground-based charge-discharge testing. That matters for mission planners because hardware qualification on Earth is cheaper and faster than waiting for multi-year orbital demonstrations. NASA’s own framing tied the battery result to exploration beyond low Earth orbit. (nasa.gov) The agency’s May 21 page said the 2025 ISS research portfolio was meant to support future missions to the Moon and Mars, and it pointed readers to the 2025 Annual Highlights of Results for fuller documentation of the station’s research output. May 21, 2026 is the date NASA published the highlights page that brought the battery result back into public view. (mdpi.com) June 6, 2025 is the publication date of the underlying *Aerospace* paper by JAXA and Kanadevia researchers, which remains the primary technical record for the 434-day ISS test. (nasa.gov)