Equilibrium Phases in the Lithium-Sulfur System

Equilibrium phases in the lithium‐sulfur system on the sulfur side of (the only compound observed in this system) were determined using an unusual vapor transport technique. In this method, equilibrium compositions of the melts at various temperatures can be obtained by utilizing the transport of sulfur vapor from one melt to a second one. The lithium‐sulfur phase diagram exhibits a large miscibility gap which extends from the monotectic composition, 65.5 mole per cent (m/o) sulfur, to almost pure sulfur (0.035 m/o lithium) at the monotectic temperature, . The melting point of lithium sulflde was found to be . The results are also presented as the lithium sulfide‐sulfur phase diagram, in which the miscibility gap extends from the monotectic composition, 73.7 m/o sulfur, to nearly pure sulfur (0.0175 m/o lithium sulfide). A comparison of the liquidus at the region of the system with those constructed using Temkin's model indicates the probable existence in these melts of sulfide species such as , , and , in addition to S 2− .