Form Energy has raised $750 million to expand iron-air battery manufacturing in West Virginia, aiming to supply grid-scale storage capable of delivering electricity for up to 100 hours. The funding reflects growing demand for long-duration storage as renewable generation expands and AI data centres increase US electricity consumption.

Unlike conventional lithium-ion systems that typically operate for only a few hours, Form’s batteries use iron that rusts during discharge and is converted back during charging, reducing reliance on costly minerals. The company has secured customers including Google, which plans a 30-gigawatt-hour battery project in Minnesota costing about $1 billion, and Crusoe, which intends to buy 12 gigawatt-hours; Form reportedly has an 80-gigawatt-hour commercial backlog, four times larger than earlier this year. Its supply chain is about 80% US-based, helping it benefit from efforts to reduce dependence on Chinese battery manufacturing.