The Super-iron battery is a moniker for a proposed class of rechargeable electric battery. Such batteries feature cathodes composed of ferrate salts, commonly potassium ferrate (K
2FeO
4) or barium ferrate (BaFeO
4). [1] [2] [3] One attraction to the proposed device is that the spent cathode would consist of a rust-like material, which is preferable to batteries based on toxic cadmium, manganese and nickel. [1] [2] [3] Another attraction is potentially higher energy capacity. [1]