Solubility, Stability, and Electrochemical Studies of Sulfur-Sulfide Solutions in Organic Solvents

摘要

A preliminary study of the sulfur electrode in organic solvents suggests that the system warrants further investigation for use in a low-temperature (100° to 120° C) Na-S secondary battery. A qualitative screening was undertaken at 120° C to determine the solubilities and stabilities of Na2S and Na2S2 in representatives of many classes of organic solvents. From this screening and further quantitative studies, two classes of solvents were selected for further work: amides and cyclic polyalcohols. Voltammetric and Na-S cell charge-discharge studies of sulfide solutions in organic solvents (e.g., N, N-dimethylformamide) at 120° C suggested that the reversibilities of the reactions on Pt or high-density graphite were moderately poor. However, the sulfur elec¬trode was indeed reducible (and oxidizable) through the range of elemental sulfur to Na2S. Reac-tions and mechanisms are proposed for the oxidation-reduction processes occurring at the sulfur electrode.