β-NaVO3 as a pseudocapacitive anode material for sodium-ion batteries

Abstract

High-performance anode materials are essential for the realization of sodium-ion batteries. In this work, nanostructured orthorhombic β-NaVO₃ was prepared by a simple solution method and investigated as an anode material for sodium-ion batteries. β-NaVO₃ exhibits an initial discharge capacity of 356 mA h g⁻¹ at a low current density. Enhanced performance was realized with the β-NaVO₃/Gr composite with an initial discharge capacity of 576 mA h g⁻¹ at a low current density and an excellent cycle stability of 83% capacity retention after 400 cycles at a current density of 500 mA g⁻¹. The sodium diffusion coefficients of β-NaVO₃/Gr and β-NaVO₃ calculated by the galvanostatic intermittent titration technique vary from 10⁻¹³ to 10⁻¹⁰ cm² s⁻¹. Ex situ XRD, TEM and Raman results reveal that the orthorhombic crystal structure of β-NaVO₃ transforms into an amorphous phase after the initial charging–discharging process. The detailed pseudocapacitive behavior in β-NaVO₃ was investigated by cyclic voltammetry.