Ethylene glycol-regulated ammonium vanadate with stable layered structure and favorable interplanar spacing as high-performance cathode for aqueous zinc ion batteries

Ammonium vanadate compounds featuring large capacity, superior rate capability and light weight are regarded as promising cathode materials for aqueous zinc ion batteries (AZIBs). However, the controllable synthesis of desired ammonium vanadates remains a challenge. Herein, various ammonium vanadate compounds were successfully prepared by taking advantage of ethylene glycol (EG) regulated polyol-reduction strategy and solvent effect via hydrothermal reaction. The morphology and crystalline phase of resultant products show an evolution from dendritic (NH4)2V6O16 to rod-like NH4V4O10 and finally to lamellar (NH4)2V4O9 as increasing the amount of EG. Specifically, the NH4V4O10 product exhibits a high initial capacity of 427.5 mAh/g at 0.1 A/g and stable cycling with a capacity retention of 90.4% after 5000 cycles at 10 A/g. The relatively excellent electrochemical performances of NH4V4O10 can be ascribed to the stable open-framework layered structure, favorable (001) interplanar spacing, and peculiar rod-like morphology, which are beneficial to the highly reversible Zn2+ storage behaviors. This work offers a unique way for the rational design of high-performance cathode materials for AZIBs.