Thiadiazole Disulfide Cross-Linked Poly(3,4-ethylenedioxythiophene)\nNanoparticles: A Dual Redox Approach for Organic Cathode Batteries

This\nstudy focuses on the synthesis and electrochemical characterization\nof nanoscale particles of semiconducting poly-3,4-ethylenedioxythiophene\n(PEDOT) functionalized with a disulfide/thiolate redox couple, specifically\n2,5-dimercapto-1,3,4-thiadiazole (DMcT), allowing for dual redox particles\ndesigned for use as an organic cathode electrode. The nanoscale PEDOT-DMcT-Li\ndual redox particles have specific discharge capacities in a lithium\nhalf-cell of 91.9 mAh/g (85% of the maximum theoretical specific capacity,\nassuming both disulfide and polaron access on PEDOT) at low C-rates.\nThis accessible capacity is attributed to the nanoscale particle size\nand the integration of a semiconducting conjugated backbone, which\nreduces internal resistance during oxidation. Comprehensive analyses,\nincluding cyclic voltammetry and galvanostatic cycling, reveal the\ncontribution of the two individual redox components, namely, disulfide/thiolate\nand PEDOT, in this redox active material. Long-term cycling stability\ntests further suggest minimal degradation over 400 cycles with the\nobserved capacity decay primarily attributed to charge trapping. Using\nan asymmetric charge/discharge rate cycling method to mitigate charge\ntrapping results in an increase in Coulombic efficiency as well as\ncapacity. Moreover, asymmetric cycling improved discharge capacity\nretention to 69% compared with 52% under symmetric rate cycling conditions\nafter 400 cycles, without additional chemical modifications. These\nfindings outline the redox behavior of the PEDOT-DMcT-Li system with\ndual-redox properties and point to their potential use as a cathode\nin organic batteries.