FE-57 MOSSBAUER-SPECTROSCOPY OF REDUCED CATHODES IN THE LI/FES2 BATTERY SYSTEM - EVIDENCE FOR SUPERPARAMAGNETISM

Cathodes removed from fully discharged Li|LiClO4-propylene carbonate|FeS2 cells have been studied by 57Fe Mössbauer spectroscopy. Experiments carried out at 295, 77, and 4.2 K indicated that the major phase present was a mixture of superparamagnetic iron particles and bulklike α-iron. Chemical reduction of FeS2 with n-BuLi in hexane also yielded a similar mixture. Measurements in external magnetic fields of up to 1.5 T confirmed the presence of superparamagnetic iron, and these data led to an estimate of the average particle diameter of 3.6 ± 0.1 nm. An analysis of the data in terms of superferromagnetism was inconsistent with the variable-temperature measurements. © 1990 American Chemical Society.