Electron-Withdrawing Group Functionalized Anthraquinone Polymers for High-Performance Organic Zinc-Ion Batteries

Aqueous zinc ion batteries (AZIBs) stand out among various battery technologies for their advantages, including low cost, high safety, and green credentials. We chemically polymerized anthraquinone and triphenylamine derivatives to prepare the π-conjugated polymers poly 2-((4-(diphenylamine)benzylidene)amino)anthracene-9,10-dione (PDAH) and poly 2-((4-((4-bromophenyl)(phenyl)amino)benzylidene)amino)anthracene-9,10-dione (PDABr), as cathode materials for AZIBs. The anthraquinone-based structure's high charge storage capacity, coupled with the π-conjugated structure's strong charge transfer capability, enabled these electrode materials to exhibit excellent electrochemical performance. Among them, the electron-withdrawing group -introduced in PDABr induces a p-π interaction with the adjacent benzene ring, optimizing electron and ion migration within the battery. This enhancement improves the electrode material's stability and electrochemical activity, leading to superior battery performance, especially in rate performance, cycle life, and stability. Comparative experiments revealed that PDABr//Zn exhibited a higher specific capacity (0.1 A g^-1, 210.57 mA h g^-1) than PDAH//Zn (0.1 A g^-1, 145.7 mA h g^-1). At the same current density, PDABr//Zn also showed better cycling stability with a (capacity retention of 93% after 6000 cycles at 5 A g^-1). Additionally, PDABr//Zn exhibited exceptional rate capability, maintaining its specific capacity upon returning to the initial current density. By comparing the physical and electrochemical properties of PDAH//Zn and PDABr//Zn, the relationship between the p-π conjugation effect and electrochemical performance is elucidated. This study provides a strategy for the fine-tuned, molecular design of organic electrode materials, specifically aimed at enhancing high-energy organic zinc-ion batteries.