Electrochemical reduction of Li2FeS2 in solid electrolyte

The nature of the product of the electrochemical reduction of Li2FeS2 has b een investigated. This product was completely reoxidized in intimate contac t with a lithium ion-conducting solid electrolyte. The product is regarded as alpha -Fe, although usually, Fe is electrochemically inactive in contact with a solid electrolyte. In order to understand the reason for this discr epancy, the product was investigated by X-ray diffraction and Mossbauer spe ctroscopy. Its diffraction pattern did not show clear peaks and its Mossbau er spectrum was attributed to superparamagnetic Fe-0. These results suggest that the reduction product consists of non-crystalline, small particles of Fe dispersed in Li2S. Because of the small particle size, most of the Fe a toms are in contact with US. This environment is considered to permit the c ontinuous reoxidation to Li2FeS2, resulting in its electrochemical activity . (C) 2001 The Electrochemical Society.