Leveraging rust
Energy density is especially important when it comes to portable electronics, but not all batteries serve such systems. Grid storage, which is useful for storing energy from less reliable sources such as wind and solar, doesn’t need to be portable once it’s in place. Size and weight then become less important, but costs rise. Sodium provides one opportunity, but other chemistries can, as well.
One example is the iron-air battery. It features an iron anode and an air cathode that contributes oxygen. Effectively, iron moves back and forth between its metallic state and its oxidized state, i.e., rust. When it rusts, iron gives up an electron. It takes it back when discharging. Form Energy is one company developing this technology, and the company says that iron-air batteries cost around $20/kWh. That compares with $200 to $300/kWh for lithium-ion.
Zinc is another metal already present in everyday alkaline batteries. ReVolt is developing zinc-air batteries for vehicles and grid storage. Eos is working on a zinc hybrid battery with a conductive plastic anode and a carbon-felt cathode, with bipolar electrodes. The company intends it for grid storage.
November 13, 2024