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

Abstract

Abstract2D materials with atomically precise thickness and tunable chemical composition hold promise for potential applications in nanoenergy. Herein, a bilayer‐structured VOPO4⋅2H2O (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 × 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 ≈0.2 eV (bulk sample: 1.5 eV) along with an ultralow diffusion barrier of ≈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 ≈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).