Enhanced electrochemical performance of Na_3V_2(PO_4)_2F_3 for Na-ion batteries with nanostructure and carbon coating

摘要

Carbon-coating Na~(3)V~(2)(PO~(4))~(2)F~(3)nanoparticles (NVPF@C NP) were prepared by a hydrothermal assisted sol–gel method and applied as cathode materials for Na-ion batteries. The as-prepared nanocomposites were composed of Na~(3)V~(2)(PO~(4))~(2)F~(3)nanoparticles with a typical size of ~ 100 nm and an amorphous carbon layer with the thickness of ~ 5 nm. Cyclic voltammetry, rate and cycling, and electrochemical impedance spectroscopy tests were used to discuss the effect of carbon coating and nanostructure. Results display that the as-prepared NVPF@C NP demonstrates a higher rate capability and better long cycling performance compared with bare Na~(3)V~(2)(PO~(4))~(2)F~(3)bulk (72 mA h g_(−1)at 10 C vs 39 mA h g_(−1)at 10 and 1 C capacity retention of 95% vs 88% after 50 cycles). The remarking electrode performance was attributed to the combination of nanostructure and carbon coating, which can provide short Na-ion diffusion distance and rapid electron migration.