Redox Activity of an Organosulfur Compound and Its Application to Polymer Lithium Batteries

Abstract

Redox activity of an organosulfur compound with multiple thiol groups and its application to a cathode active material of lithium batteries are described. To accelerate a slow redox reaction of organosulfur compounds such as 2,5-dimercapto-1,3,4-thiadiazole (DMcT), conducting polymer polyaniline (PAn) is mixed with organosulfur compounds, yielding a composite material. Within the composite, DMcT and PAn interact at molecular-level and the redox reaction of DMcT is successfully accelerated by PAn. The DMcT /PAn composite shows a promise as a high energy cathode active material with the discharge capacity of 185 Ah/kg-cathode and the average discharge voltage at 3.4 V. Furthermore, using a copper foil as a cathode current collector, battery performances of the composite cathode are significantly improved. The observed improvement is attributed to a formation of a complex between a copper ion and DMcT, which accelerates the redox reaction of DMcT. The discharge capacity of the composite cathode on a copper current collector is 225 Ah/kg-cathode. The discharge capacity is further increased to 500 Ah/kg-cathode by adding elemental sulfur to the composite.