Extended π-Conjugated System in Organic Cathode with Active C═N Bonds for Driving Aqueous Zinc-Ion Batteries
Hong Zhang, Si‐Jun Xie, Ziyi Cao, Dongxiao Xu, Lipeng Wang, Huayi Fang, Jianfeng Shen, Mingxin Ye
Abstract
Organic compounds have recently been demonstrated to be alternative cathodes to inorganic ones for aqueous zinc-ion batteries (ZIBs), while the limited electrochemical performance greatly restricts their applications, which is partly attributable to their small π-conjugated systems. Here, to extend the π-conjugated system, diquinoxalino[2,3-a:2′,3′-c]phenazine (DQP) was designed and prepared, intriguingly exhibiting an ultrahigh capacity of 413 mA h g–1 at 50 mA g–1 for ZIBs. In addition, the combination of detailed density functional theory calculations and ex situ characterization techniques, such as IR and X-ray photoelectron spectroscopy spectra, clearly reveals the electrochemically active C═N bonds transformation in charging and discharging circulation. Moreover, the results also demonstrate that the extended π-conjugated system with active C═N bonds is associated with enhanced electrochemical stability, conductivity, and reversible capacity. Besides, owing to its excellent insolubility in water, DQP also delivers high capacity retention of 86% after 1000 cycles at 5 A g–1. Thus, this work provides a reasonable strategy for organic cathodes applied in aqueous ZIBs.