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

Abstract

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.

Optimizing Interplanar Spacing, Oxygen Vacancies and Micromorphology via Lithium‐Ion Pre‐Insertion into Ammonium Vanadate Nanosheets for Advanced Cathodes in Aqueous Zinc‐Ion Batteries

“…+ ion and oxygen atom between V─O layers, multivalent states of vanadium, and extensive pathways facilitating Zn 2+ ion transport. [31,33] Besides, NH 4…”

“…[ 16,31,32 ] Its broad appeal stems from the robust interaction between NH 4 + ion and oxygen atom between V─O layers, multivalent states of vanadium, and extensive pathways facilitating Zn 2+ ion transport. [ 31,33 ] Besides, NH 4 + has a large ionic radius (1.43 Å) and a low molar mass (18 g mol −1 ), which could provide high mass and volume specific capacities when acting as a pre‐inserted layer ion. [ 34 ] However, the strong electrostatic attraction between the small‐radius Zn 2+ (0.76 Å) and the highly electronegative oxygen atoms poses a challenge Zn 2+ ions readily associate with these highly electronegative oxygen atoms within the V─O layers.…”