Heterocyclic conjugated planar polymers with strong π-electron delocalization as high-capacity cathodes for superior quasi-solid-state zinc-organic batteries

Abstract

Aqueous zinc-organic batteries (AZOBs) are emerging energy storage devices that maximized the realization of renewable resources, environmental benignity, and system inherent safety. However, the organic electrode materials still encounter the challenge of sluggish reaction kinetics and poor reversibility. Herein, two heterocyclic conjugated planar polymers (TA-PTO and TAB-PTO) were facilely synthesized and then applied as the cathode materials for AZOBs. The planar conjugated structure with strongly intermolecular interactions endows them with limited solubility and robust structural stability, while the heterocyclic conjugated structure with strong π-electron delocalization shows superior electron affinity and higher redox activity. Encouragingly, benefitting from robust synergistic multi C = O and C = N active centers, the well-designed TA-PTO cathode delivers ultrahigh specific capacity (469 mAh g^-1 at 0.2 A g^-1) and long-term cycling stability (87.78 % capacity retention after 5000 cycles at 10 A g⁻¹) according to proton-insertion dominated H⁺/Zn²⁺ co-storage mechanism. Most importantly, the pouch-type quasi-solid-state AZOBs based on TA-PTO cathode display impressive electrochemical performance under different bending states, further highlighting the promising application prospect.