Integrated insights into Na+ storage mechanism and electrochemical kinetics of ultrafine V2O3/S and N co-doped rGO composites as anodes for sodium ion batteries

Abstract

Sodium ion (Na⁺) storage and kinetics are of great importance for the development of high-performance sodium ion batteries. Herein, we report a composite of ultrafine V₂O₃ nanoparticles evenly anchored into three-dimensional S,N co-doped rGO conductive networks as a promising anode material for sodium ion batteries. Such a subtle architecture effectively connects isolated V₂O₃ nanoparticles into a structure with integrity, suppresses their aggregation and introduces more active sites, which significantly facilitates Na⁺ storage and the kinetics. Electrochemical analysis, in situ X-ray diffraction and density functional theory computations verified the Na⁺ storage mechanism, where one Na⁺ inserts into per V₂O₃ formula unit without crystallographic phase transition, coupling with small variations in the unit cell volume. In addition, V₂O₃ has preferable ability for interfacial Na⁺ storage, which was validated by strong Na⁺ adsorption on the (113) crystal plane. When used as an anode material for sodium ion batteries, this composite exhibited admirable rate capability and ultralong cycle durability. Furthermore, full cells of V₂O₃/S,N co-doped rGO//Na₃V₂(PO₄)₃@rGO also showed excellent electrochemical performance, demonstrating prospective applications to sodium ion batteries.