Molten sodium batteries have been used for many years to store energy from renewable sources, such as solar panels and wind turbines. However, commercially available molten sodium batteries, called sodium-sulfur batteries, typically operate at 520-660 degrees Fahrenheit. Sandia’s new molten sodium-iodide battery operates at a much cooler 230 degrees Fahrenheit instead.
“We’ve been working to bring the operating temperature of molten sodium batteries down as low as physically possible,” said Leo Small, the lead researcher on the project. “There’s a whole cascading cost savings that comes along with lowering the battery temperature. You can use less expensive materials. The batteries need less insulation and the wiring that connects all the batteries can be a lot thinner.”
However, the battery chemistry that works at 550 degrees doesn’t work at 230 degrees, he added. Among the major innovations that allowed this lower operating temperature was the development of what he calls a catholyte. A catholyte is a liquid mixture of two salts, in this case, sodium iodide and gallium chloride.