Tuning [VO6] Octahedron of Ammonium Vanadates via F Incorporation for High‐Performance Aqueous Zinc Ion Batteries

Abstract

AbstractThe electrochemical properties of vanadium‐based materials as cathode materials for aqueous zinc ion batteries are still restricted by low conductivity, sluggish reaction kinetics, and poor structural stability. Herein, the [VO6] octahedron, as the basic unit of vanadium‐oxide layer of ammonium vanadates (NH4V4O10, denoted as NVO), is incorporated by F atoms to regulate the coordinated environment of vanadium. Density functional theory (DFT) calculations and experimental results show that both physicochemical and electrochemical properties of NVO are improved by F‐doping. The enhanced electronic conductivity accelerates the electron transfer and the expanded interlayer spacing expedites the diffusion kinetics of zinc ions. As a result, the F‐doped NVO (F‐NVO) electrode shows a high discharge capacity (465 mAh g−1 at 0.1 A g−1), good rate capability (260 mAh g−1 at 5 A g−1), and long‐term cycling stability (88% capacity retention over 2000 cycles at 4 A g−1). The reaction kinetics and energy storage mechanism of F‐NVO are further validated by in situ and ex situ characterizations.