X-ray absorption near edge structure analysis of the charge-discharge mechanisms of dithiobiuret polymer used as a high-capacity cathode material for lithium-ion batteries

We investigated the electronic structures of low-molecular-weight dithiobiuret (DTB) compounds in both reduced and oxidized states along with those of a DTB polymer in the discharged and charged states using X-ray absorption near edge structure (XANES) measurements. DTB is a simple and lightweight organosulfur molecule with two neighboring tautomeric thiol/thione groups (-SH/>CS) that can form disulfide (S-S) bonds by reversible oxidative cyclization. The DTB polymer, composed of alternating DTB and phenylene (Ph) units, exhibited a high capacity (about 260 mA h g−1) without any significant degradation in the charge and discharge cycle characteristics. Based on XANES measurements, charge-discharge experiments, and quantum chemical calculations, we propose that the reactions of two types of redox couples contribute the redox reaction of the DTB polymer.