What is Form Energy Iron-Air Battery?

The Form Energy iron-air battery stores electricity by using electric current to convert iron oxide into metallic iron, then reverses the reaction on discharge by letting the iron oxidize back into rust in a controlled electrochemical cell, releasing electricity as it does. Because iron and air are abundant and inexpensive, the battery is built for long-duration storage measured in days rather than hours, discharging steadily over multi-day stretches instead of delivering a short, high-power burst.