New Iron Sulfur Cathodes for Nonaqueous Lithium Batteries

The compounds KFeS 2 and M 0.5 FeS 2 ( M = Sr , Ba ) are shown to behave as electrochemically active, reversible cathode materials in nonaqueous lithium electrochemical cells. The compounds are characterized by infinite chains of edge‐shared tetrahedra supported by the alkali or alkaline earth metal. All the iron is in the 3+ oxidation state. Cell data and reactions with n‐butyl lithium show that one lithium per iron may be incorporated with a structural rearrangement and reduction of Fe 3+ to Fe 2+ .