A new energy storage material: Organosulfur compounds based on multiple sulfur-sulfur bonds

A new class of organic sulfur-based energy storage material, polysulfides, has been proposed in the present communication. Polysulfides contain multiple sulfur atoms {-(S)(n)-} in their molecules, the energy density of which are even higher than those of disulfides. Polysulfuric compounds, viz., dimers of disulfide, trisulfide, tetrasulfide of 5-methyl-1,3,4-thiadiazole-2-thiol (MTT) and polymers of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) were synthesized and electrochemically studied. Theoretical energy densities of MTT dimers range between 1500 and 3500 Wh/kg. The values increase with an increase in the number of sulfur atoms in the moiety. Cyclic voltammograms for the trisulfide and tetrasulfide of MTT dimers have more reduction peaks compared with that of the corresponding disulfide. The specific energies (per cathode) for Li/DMcT-disulfide, Li/DMcT-trisulfide, and Li/DMcT-tetrasulfide were 385, 590, and 700 Wh/kg, respectively.