Bilayered VOPO<sub>4</sub>⋅2H<sub>2</sub>O Nanosheets with High‐Concentration Oxygen Vacancies for High‐Performance Aqueous Zinc‐Ion Batteries
Zeyi Wu, Chengjie Lu, Fei Ye, Lin Zhang, Le Jiang, Qiang Liu, Hongliang Dong, ZhengMing Sun, Linfeng Hu
Abstract
Abstract 2D materials with atomically precise thickness and tunable chemical composition hold promise for potential applications in nanoenergy. Herein, a bilayer‐structured VOPO 4 ⋅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 × 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 ).