HAMPTON, Oct. 15 -- NASA says small prototype batteries have worked down to minus 80 degrees Celsius in a vacuum chamber, which is still 120 degrees warmer than the night at the Moon's South Pole.

The cells belong to a project called SPEARS, short for Solid Power for Extreme Environment Adaptability and Resilience in Space, led by NASA's Glenn Research Center in Cleveland. Their difference from a phone or laptop battery is the electrolyte. A conventional lithium-ion cell uses a liquid that would freeze in lunar cold, stop working in 100-degree lunar day and boil away in vacuum; SPEARS replaces it with a solid ceramic or polymer, NASA said in a release published Wednesday.

At NASA's Langley Research Center in Hampton, thermal vacuum test...