Enhanced electrochemical performance of Na3V2(PO4)2F3 for Na-ion batteries with nanostructure and carbon coating

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.