Why iron-sodium batteries matter for the long-duration grid

The U.S. electrical grid is facing increasing stress due to aging infrastructure and rising demand driven by data centers, electric vehicles, and industrial electrification. While lithium-ion batteries currently dominate short-duration energy storage, they become economically unfeasible beyond about four hours of storage. To address the need for long-duration storage—ranging from 8 to 24 hours—to manage multi-day weather variability and seasonal demand swings, a San Francisco startup, Inlyte Energy, is commercializing iron-sodium “salt batteries.” These batteries leverage a decades-old sodium–metal chloride chemistry redesigned for stationary grid storage, using abundant and low-cost materials like iron and table salt instead of lithium, cobalt, or nickel. The design features a ceramic membrane that conducts sodium ions, enhancing durability and stability. Unlike lithium-ion batteries, which prioritize energy and power density for applications like electric vehicles, iron-sodium batteries emphasize long duration, low cost per kilowatt-hour, and intrinsic safety. Although they operate at higher temperatures and have