Synthesis and evaluation of polythiocyanogen (SCN)x as a rechargeable lithium-ion battery electrode material

Polythiocyanogen, (SCN)x, is a promising lithium-ion battery electrode material due to its high theoretical capacity (462 mAh g−1), safe operation, inexpensive raw materials, and a simple and less energy-intensive manufacturing process. The (SCN)x was prepared from the solution of trithiocyanate (SCN)3− in methylene dichloride (MDC), which was prepared by electrochemical oxidation of ammonium thiocyanate (NH4SCN) in a two-phase electrolysis medium of 1.0 M NH4SCN in 0.50 M H2SO4 + MDC. The (SCN)3− underwent auto catalytic polymerization to (SCN)x during MDC removal. Battery electrodes with (SCN)x as the active material were prepared, and tested in Swagelok cells using lithium foil as the counter and reference electrode. The cells delivered capacities in the range of 200–275 mAh g−1 at the discharge–charge rate of 0.2 C. The cells were tested up to 20 cycles and showed repeatable performance with a coulombic efficiency of 97% at the 20th cycle. The results presented here indicate that (SCN)x is a promising lithium-ion battery electrode-material candidate for further studies.

► Polythiocyanogen, (SCN)x an inorganic polymer as lithium ion battery electrode.
► Redox reactions of –S–S– bonds occur in the 0–2.0 V range vs. Li/Li+.
► Charge–discharge capacities in the range of 200–275 mAh g−1 were obtained.
► Coulombic efficiency of 97% after 20 cycles.