Effects of Adding Copper(II) Salt to Organosulfur Cathodes for Rechargeable Lithium Batteries

We report the preliminary analysis of a new cathode material and the performance of secondary lithium cells which contain it. The material is comprised of an organosulfur compound, 2,5‐dimercapto‐1,3,4‐thiadiazole (DMcT), doped with a copper(II) salt in a poly(aniline) matrix. Secondary lithium cells which use this material as cathodes can be discharged at 300 Ah per kg‐cathode for ca. 10 cycles, 260 Ah per kg‐cathode for at least 80 cycles, or 170 Ah per kg‐cathode for ca. 130 cycles. Further, after failure of these cells, replacement of the lithium anode restores the original capacity. Vibrational and electronic spectroscopy of the copper(II)/DMcT system agree with previous reports on the redox chemistry which occurs between Cu(II) and thioamide groups. A preliminary cyclic voltammetric study of this system indicates that the electroactive compound is probably a Cu(I)/DMcT complex which does not exhibit traditional electrocatalytic behavior, most likely due to the effects of proton‐coupling in the redox processes of DMcT.