Uniform and continuous carbon coated sodium vanadium phosphate cathode materials for sodium-ion battery

Abstract

Sodium vanadium phosphate Na3V2(PO4)3 coated with uniform and continuous carbon film is synthesized by heat treatment of the precursors under C2H2-pyrolysis reducing atmosphere, in which Na3V2(PO4)3 is formed synchronously with carbon coating. As a cathode material for Na-ion batteries, Na3V2(PO4)3/C shows a flat charge plateau at about 3.39 V in the potential window of 2.5–4.0 V versus Na+/Na. The charge capacity of 83.7 mAh g−1 and discharge capacity of 82.1 mAh g−1 can be obtained at a current rate of 1C after 300 cycles and the coulombic efficiency averages 98% throughout. The enhanced electrochemical performance can be contributed to the uniform and continuous carbon layer, which greatly improves the electric conductivity of Na3V2(PO4)3.