An iron-57 Moessbauer study of the intermediates formed in the reduction of iron disulfide in the lithium/iron disulfide battery system

Abstract

{sup 57}Fe Moessbauer spectroscopy has been used to study the intermediates formed at the FeS{sub 2} cathode during room-temperature discharge in the Li{vert bar}LiClO{sub 4}-propylene carbonate {vert bar}FeS{sub 2} cell. Moessbauer spectra recorded at 4.2 K provided evidence for the formation of Li{sub 3}Fe{sub 2}S{sub 4} and another lithiated phase, similar to but not exactly the same as Li{sub 2}FeS{sub 2}. Small particles of superparamagnetic iron were also formed early in the discharge. When LiAsF{sub 6} was the electrolyte, no intermediates were detectable and rapid reduction to small particles of iron occurred. Chemical lithiation of FeS{sub 2} with n-Buli in hexane produced a mixture of reduction products similar to that observed for the Li{vert bar}LiClO{sub 4}-propylene carbonate{vert bar}FeS{sub 2} cell.