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

摘要

Sodium vanadium phosphate Na_3V_2(PO_4)_3 coated with uniform and continuous carbon film is synthesized by heat treatment of the precursors under C_2H_2-pyrolysis reducing atmosphere, in which Na_3V_2(PO_4)_3 is formed synchronously with carbon coating. As a cathode material for Na-ion batteries, Na_3V_2(PO_4)_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 Na_3V_2(PO_4)_3.