Bilayered VOPO4.2H2O Nanosheets with High-Concentration Oxygen Vacancies for High-Performance Aqueous Zinc-Ion Batteries

2D materials with atomically precise thickness and tunable chemical composition hold promise for potential applications in nanoenergy. Herein, a bilayer-structured VOPO4.2H(2)O (bilayer-VOP) nanosheet is developed with high-concentration oxygen vacancies ([Vo]) via a facile liquid-exfoliation strategy. Galvanostatic intermittent titration technique study indicates a 6 orders of magnitude higher zinc-ion coefficient in bilayer-VOP nanosheets (4.6 x 10(-7) cm(-2) s(-1)) compared to the bulk counterpart. Assistant density functional theory (DFT) simulation indicates a remarkably enhanced electron conductivity with a reduced bandgap of approximate to 0.2 eV (bulk sample: 1.5 eV) along with an ultralow diffusion barrier of approximate to 0.08 eV (bulk sample: 0.13 eV) in bilayer-VOP nanosheets, thus leading to superior diffusion kinetics and electrochemical performance. Mott-Schottky (impedance potential) measurement also demonstrates a great increase in electronic conductivity with approximate to 57-fold increased carrier concentration owing to its high concentration [Vo]. Benefited by these unique features, the rechargeable zinc-ion battery composed of bilayer-VOP nanosheets cathode exhibits a remarkable capacity of 313.6 mAh g(-1) (0.1 A g(-1)), an energy density of 301.4 Wh kg(-1), and a prominent rate capability (168.7 mAh g(-1) at 10 A g(-1)).

Automated summary

A bilayer-structured VOPO4.2H(2)O (bilayer-VOP) nanosheet with high-concentration oxygen vacancies was developed through a facile liquid-exfoliation strategy. The nanosheets showed superior properties in zinc-ion transport coefficient and electron conductivity, leading to outstanding performance in rechargeable zinc-ion batteries.