Amorphous MoS3 and WS3

Abstract MoS 3 and WS 3 are examples of a group of transition metal chalcogenides which have only been prepared in amorphous form. Recently these compounds have been found to show interesting properties as cathode materials in ambient temperature alkali metal batteries. In particular, MoS 3 reacts readily and reversibly with lithium, giving a battery system with a high theoretical energy density. In this paper, we report results of structural studies of amorphous MoS 3 and WS 3 using X-ray radial distribution analysis, EXAFS, X-ray photoelectron spectroscopy, magnetic susceptibility measurements and vibrational spectroscopies. The results reveal that these amorphous compounds have a chain-like structure similar to that of the crystalline trichalcogenides of the neighboring IVB and VB elements. However, the combined formations of the metal dimers and polysulfide bonds along the chains are structural features unique to these amorphous compounds. The possible implications of this structure to the observed electrochemical behavior will be discussed.