Grain of Salt Iron-Air
The $20/kWh number comes from Form Energy, an iron-air battery startup, and they are indeed claiming that their current (not future!) commercial product is “less than 1/10 the cost of lithium-ion”.
It’s a press release from a startup, so it’s worth taking with a grain of salt, but that’s what they say.
They have a pilot project with Minnesota-based Great River Energy, planned to open in 2023 and providing 1 MW/150 MWh of power. The price of the facility is undisclosed, however.
What is public information, however, is the raw materials cost of different battery chemistries, which allows us to make apples-to-apples comparisons.