A tetraphenyl-p-phenylenediamine-and benzodithiophene-4,8-dione-based conjugated microporous polymer as a robust cathode for durable aqueous Zn batteries

Abstract

Redox-active conjugated microporous polymers (CMPs) are promising sustainable electrode materials; however, achieving high capacity, rapid charge-discharge kinetics, and long-term cycling stability simultaneously in aqueous Zn batteries remains a major challenge. Here, we report a tetraphenyl-p-phenylenediamine-and benzodithiophene-4,8-dione-linked CMP (TPDA-Ph-BDT) featuring a rigid π-conjugated skeleton, permanent porosity, and a high density of carbonyl/amine redox sites. When employed as a cathode in a mild aqueous ZnSO 4 electrolyte, TPDA-Ph-BDT CMP delivers a high reversible capacity of 154 mAh g⁻ 1 at 0.5 A g⁻ 1 and outstanding high-rate stability, retaining 85 mAh g⁻ 1 over 50,000 cycles at 20 A g⁻ 1 with 96% capacity retention. Mechanistic analyses (ex situ FTIR/XPS/solid-state NMR and in situ pH evolution) reveal that charge storage is dominated by reversible proton-coupled redox at the C=O and amine N centers, as well as Zn 2 ⁺ insertion, enabled by rapid proton transport through the porous conjugated network. Kinetic analyses reveal low apparent energy activation (315 meV) and predominantly capacitive charge storage, which together explain the outstanding rate performance. This work establishes CMP structural engineering as a powerful route to high-performance, metal-free cathodes and provides clear design principles for nextgeneration aqueous zinc-organic energy storage.