In-situ synthesis of reduced graphene oxide modified lithium vanadium phosphate for high-rate lithium-ion batteries via microwave irradiation

Highlights: • Graphene-decorated Li₃V₂(PO₄)₃ is synthesized via microwave irradiation. • Both Li₃V₂(PO₄)₃ and RGO can be simultaneously achieved through this route. • The GO is reduced by microwave irradiation not the carbon. • Li₃V₂(PO₄)₃/RGO displays excellent high-rate ability and cyclic stability. - Abstract: We report a simple and rapid method to synthesize graphene-modified Li₃V₂(PO₄)₃ as cathode material for lithium-ion batteries via microwave irradiation. By treating graphene oxide and the precursor of Li₃V₂(PO₄)₃ in a commercial microwave oven, both reduced graphene oxide and Li₃V₂(PO₄)₃ could be simultaneously synthesized within 5 min. The structure, morphology and electrochemical performances of as-synthesized graphene-modified Li₃V₂(PO₄)₃ are investigated systematically by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, charge/discharge tests, electrochemical impedance spectra (EIS) and cyclic voltammetry (CV). The XRD result indicates that single-phase graphene-modified Li₃V₂(PO₄)₃ with monoclinic structure can be obtained. Both SEM and TEM images show that Li₃V₂(PO₄)₃ nanocrystals are embedded in the reduced graphene oxide sheets which could provide an easy path for the electrons and Li-ions during the cycling process. Compared with the pristine Li₃V₂(PO₄)₃ electrode, graphene-modified Li₃V₂(PO₄)₃ exhibits a better high-rate ability and cyclic stability. These superior electrochemical performances are attributed to the good conductivity of reduced graphene oxide which enhances the electrons and Li-ions transport on the surface of Li₃V₂(PO₄)₃. Thus, this simple and rapid method could be promising to synthesize graphene-modified electrode materials