Summary
NASA reports that prototype solid-state cells for its SPEARS project operated down to −80°C in thermal-vacuum tests and survived exposure to colder conditions. They must be warmed before use after extreme cold, so the results represent an early step towards batteries for lunar operations.
NASA’s SPEARS project has tested small solid-state battery cells in conditions intended to help prepare them for space use. In thermal-vacuum tests at NASA’s Langley Research Center, the prototypes operated down to −80°C, with reduced performance at that temperature. They also survived exposure to temperatures from 100°C to −170°C without sustaining damage—but survival at those extremes is different from operating there.
That distinction matters for the Moon, where nighttime temperatures at the South Pole can reach −200°C. NASA says the cells need to be warmed to their operating temperature before they can work after extreme cold.
Replacing the liquid electrolyte
Conventional lithium-ion batteries use a liquid electrolyte, which helps move charged particles between the electrodes during charging and discharging. NASA says extreme cold can freeze that liquid and potentially damage a battery. At high temperatures, a conventional battery may stop working until it cools; in a vacuum, liquid electrolyte can evaporate.
SPEARS—Solid Power for Extreme Environment Adaptability and Resilience in Space—replaces the liquid with a solid ceramic- or polymer-based electrolyte. A solid electrolyte does not freeze like a liquid, allowing a cell to withstand temperatures that would damage a conventional battery. It does not, however, make the battery able to produce power at every temperature it can survive.
The test results illustrate that difference. NASA reports operation up to 80°C and down to −60°C, with slightly reduced performance at −80°C. The separate exposure test took cells as low as −170°C and as high as 100°C; NASA says the cells were not damaged, but would need small heaters to return to operating temperature. The prototypes are therefore being developed to tolerate severe temperature swings and be warmed when needed, rather than to operate at the coldest lunar-night temperatures.
From prototype cells towards space testing
NASA says SPEARS could eventually support equipment ranging from astronaut emergency power packs and drills to rovers and long-duration scientific instruments. The battery chemistry can be adapted for different priorities, such as energy, power or durability, according to the project’s testing lead. NASA also says that warming cells only when required could reduce the need for heavy thermal-management systems in spacecraft or lunar habitats, potentially allowing lighter designs and longer missions.
The project began in 2026 and is still focused on technology development. NASA’s Ames Research Center is developing flight hardware, including test boards and electronics, to prepare the batteries for spaceflight and testing in space environments. The thermal-vacuum results are an early technical milestone; the next step described by NASA is preparing hardware for that further testing.