Solid–gas synthesis of stable V3S4 nanoflakes: electrochemical characterization as a Li-ion battery anode

Abstract

Vanadium sulfides with lower oxidation states are expected to be an interesting choice for metal-ion batteries due to their high theoretical capacity and lower redox potential. Among these vanadium sulfides, V₃S₄ having oxidation states of +2 and +3 has rarely been explored as an electrochemical energy storage material. Herein, we demonstrate a unique synthesis strategy of obtaining V₃S₄ nanoflakes from bulk V₂O₅via a two-step synthesis route where the hydrothermal treatment in the presence of ammonium sulfide modifies the bulk V₂O₅ into a VO₂ nanosheet and the solid–gas reaction completely sulfurizes the chemically modified compound at 500 °C resulting in the formation of V₃S₄ nanoflakes. The solid–gas reaction synthesis strategy under controlled pressure–temperature conditions using a chemically modified precursor results in the formation of V₃S₄ at a relatively low temperature. Detailed physicochemical characterization indicates the phase purity and high air stability of the material. The electrochemical characterization indicates the anodic behavior of the as-prepared material as a Li-ion battery anode having a high reversible capacity of 781 mA h g⁻¹ at 25 mA g⁻¹.