▎ 摘　　要

NOVELTY - A positive electrode active material comprises sodium vanadyl fluorophosphate/reduced graphene oxide obtained by compounding sodium vanadyl fluorophosphate with reduced graphene and electrochemically removing sodium. USE - Active material used in positive electrode material for calcium-ion battery (all claimed). ADVANTAGE - The active material can improve the working voltage and cycle life of the existing calcium ion battery. DETAILED DESCRIPTION - A positive electrode active material comprises sodium vanadyl fluorophosphate (NaV2O2(PO4)2F)/reduced graphene oxide (rGO) obtained by compounding sodium vanadyl fluorophosphate with reduced graphene and electrochemically removing sodium. INDEPENDENT CLAIMS are included for the following: (1) preparation of positive electrode active material, which involves dissolving and mixing sodium salt, phosphorus source, fluorine source and vanadium source to obtain a mixed solution, adding a graphene dispersion to the mixed solution for ultrasonication, transferring the ultrasonically mixed solution to a reactor for hydrothermal reaction, naturally cooling to room temperature after the reaction to obtain a black product, centrifuging and washing the black product, freeze-drying to obtain hollow nano-spherical sodium vanadyl fluorophosphate compounded with reduced graphene (Na3V2O2(PO4)2F/rGO), and removing two sodium ions in sodium vanadyl fluorophosphate by topological substitution to obtain NaV2O2(PO4)2F/rGO; and (2) usage method of positive electrode active material in positive electrode material of calcium-ion battery.