Superior performance of carbon modified Na3V2(PO4)2F3 cathode material for sodium-ion batteries

Abstract Na3V2(PO4)2F3 is a prospective candidate cathode for sodium ion batteries because of its high theoretical energy density, large channels and excellent structural stability. However, it suffers from its low electronic conductivity. In this work, carbon-coated Na3V2(PO4)2F3 nanospheres have been successfully fabricated by a one-step solvothermal method followed with heat treatment. The uniform carbon layer can effectively protect Na3V2(PO4)2F3 from direct contact with electrolyte and form effectively electron/ion conductive network. As a cathode material for sodium-ion batteries, the Na3V2(PO4)2F3/C delivers a high discharge capacity of 100.6 mAh g-1 at 1 C after 500 cycles with a high capacity retention ratio of 92.4%. Even at a high current density of 5 C, the capacity retention is 94.2% after 1000 cycles.