In winter a car battery can fail even in a slight frost. On the Moon the cold is far more severe: at the South Pole the temperature at night drops to minus 200 degrees Celsius. For future expeditions NASA needs batteries that can withstand such conditions and at the same time are not a fire hazard.
This is the focus of the SPEARS project (Solid Power for Extreme Environment Adaptability and Resilience in Space). It is led by Donald Dornbash of the Glenn Research Center in Cleveland. According to him, batteries are important on Earth too - in laptops, phones, tools and cars - but on the Moon they must work reliably and safely in a harsh environment.
Conventional lithium-ion batteries use a liquid electrolyte - a substance through which charged particles move inside the battery. In the lunar cold the liquid freezes and can damage the battery. In daytime heat of up to plus 100 degrees it, on the contrary, does not work until it cools down, and in the vacuum of space the electrolyte evaporates.
SPEARS replaces the liquid with a solid ceramic or polymer material. During recent thermal-vacuum tests at the Langley Research Center in Virginia, small cell prototypes operated at temperatures of up to plus 80 degrees, and also at minus 60 degrees. At minus 80 degrees performance declined slightly, but operability was preserved.
"We have proven for the first time that these cells can operate at minus 80 degrees Celsius," said test lead Yi Lin. He is confident that in the coming years the range can be extended.
The tests also showed that after exposure to temperatures from plus 100 to minus 170 degrees the batteries are not damaged. At minus 170 degrees they do not function, but the solid electrolyte does not freeze like a liquid and therefore survives. To bring the battery back into operation, a small amount of heating is enough. This could reduce the need for heavy thermal control systems, make spacecraft lighter and cheaper, and make missions longer.
The project began in 2026. First the team will focus on developing the technology, and then may move on to cooperation with industry. The Ames Center in Silicon Valley is preparing flight components to test the batteries in space.
According to Lin, the chemistry can be tuned to the task: using different electrode materials for more energy, power or durability. Although the project is being created for space, the technology may also find application on Earth - in cars, phones, drones and other devices that need a portable power source.