Electrochemical Reduction of Li[sub 2]FeS[sub 2] in Solid Electrolyte

Abstract

The nature of the product of the electrochemical reduction of Li2FeS2Li2FeS2 has been investigated. This product was completely reoxidized in intimate contact with a lithium ion-conducting solid electrolyte. The product is regarded as α-Fe, although usually, Fe is electrochemically inactive in contact with a solid electrolyte. In order to understand the reason for this discrepancy, the product was investigated by X-ray diffraction and Mössbauer spectroscopy. Its diffraction pattern did not show clear peaks and its Mössbauer spectrum was attributed to superparamagnetic Fe0.Fe0. These results suggest that the reduction product consists of noncrystalline, small particles of Fe dispersed in Li2S.Li2S. Because of the small particle size, most of the Fe atoms are in contact with Li2S.Li2S. This environment is considered to permit the continuous reoxidation to Li2FeS2,Li2FeS2, resulting in its electrochemical activity. © 2001 The Electrochemical Society. All rights reserved.