Ethylene Glycol Intercalation Engineered Interplanar Spacing and Redox Activity of Ammonium Vanadate Nanoflowers as a High-Performance Cathode for Aqueous Zinc–Ion Batteries

Ammonium vanadate (NH4V4O10) has attracted considerable focus as a cathode material with great potential for aqueous zinc ion batteries due to its multielectron redox reaction of V and low cost; however, problems such as structural instability and slow reaction kinetics during cycling hinder its widespread application. Herein, ethylene glycol is intercalated into the interlayer of NH4V4O10 to develop high-performance cathodes for aqueous zinc ion batteries. The layer spacing of the material is expanded by ∼23% after the intercalation of ethylene glycol, providing a large interlaminar channel for Zn2+ diffusion, while the addition of ethylene glycol leads to the micromorphology of nanoflowers self-assembled by ultrathin nanosheets, exposing more active sites for ion and electron transport. Moreover, the successful partial substitution of ethylene glycol for NH4+ in the NH4V4O10-based material results in an increase in the level of V5+ and alleviates irreversible deamination, promoting efficient redox reactions. In addition, the introduction of ethylene glycol efficiently decreases the band gap of NH4V4O10 and, thus, improves the conductivity. As a result, the ethylene glycol-intercalated NH4V4O10 cathode provides a high reversible capacity of 516 mAh g–1 at 0.5 A g–1 and achieves an excellent cycling performance with a capacity retention rate of 91% after 1000 cycles at 10 A g–1. This work provides a feasible strategy to develop high-performance layered V-based cathodes for AZIBs by the coregulation of crystal structure, micromorphology, and redox chemistry.