Abstract

Organic cathode materials (OCMs) are widely regarded as promising candidates for sustainable rechargeable batteries; however, their practical application is hindered by insufficient electrochemical performance and a lack of scalable synthesis methods. Building on our previous study of poly(o-phenylenediamine) (PoPDA), we herein present a single-precursor, solid-phase synthesis of poly(o-phenylenediamine) sulfide derivatives (PoPDAS). Using o-phenylenediamine sulfide (oPDAS) as the sole precursor, thermal treatment at 300–350 °C triggers H2SO4 and its decomposition products to simultaneously drive oxidative polymerization forming a conjugated PoPDA backbone, and in situ sulfurization introducing polysulfide (–Sn–) linkages. The dual redox activity of C=N bonds in phenazine repeating units and S–S bonds in –Sn– linkages enables a high theoretical capacity, while the robust polymer matrix effectively confines soluble sulfur species during cycling. To optimize the trade-off between reversible capacity and long-term stability, a secondary sulfurization step has been implemented. Among fourteen samples prepared via varied synthetic routes and conditions, PoPDAS-B-350-0.5 with a moderate sulfur content of 27 wt% exhibits the best performance, delivering a reversible capacity of 358 mAh g−1 and 88% capacity retention after 800 cycles. Electrochemical analysis and ex situ characterization confirm the redox mechanism involving both C=N and S–S groups, and reveal the excellent cycling stability attributed to the robust polymer backbone that confines dissociated sulfur species. These results highlight the potential of integrating multiple redox-active moieties into a polymer architecture via a scalable solid-phase synthesis to afford practical OCMs.

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