Form Energy raises $750M for rust-powered grid batteries

What's the deal? Form Energy, a US energy storage startup, has raised $750 million to scale its iron-air batteries — a technology that stores electricity using a reaction between iron and oxygen, essentially controlled rusting.

What's the endgame? The company is building long-duration batteries designed to discharge power for up to 100 hours. That far exceeds the roughly four hours typical of lithium-ion systems, positioning the technology to back up the grid through multi-day gaps in wind and solar output.

Why now? Demand for electricity is climbing as data centres, electrification, and renewables reshape the grid. Iron is cheap and abundant, offering a lower-cost path to storing energy at scale than lithium-ion alternatives.

The signal: The size of the round underlines investor conviction that the grid needs storage measured in days, not hours. If iron-air batteries deliver on cost and duration, they could become a core piece of infrastructure for a renewable-heavy power system.

Read more: The Wall Street Journal

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