New Iron Sulfur Cathodes for Nonaqueous Lithium Batteries

The compounds KFeS2 and M0.~FeS2 (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 rear-rangement and reduction of Fe 3+ to Fe e+. Cathodes containing iron compounds are of consider-able interest for application in ambient temperature lithium nonaqueous battery systems because of their low cost. Several such materials have been previously studied including the layered compounds FePS3 (1, 2), FeOC1 (3, 5) and Vx-xFe~S2 (x ~ 0.5) (6), and pyrite FeS2 (5, 7). In addition both FeS and FeS2 have been