Core/shell nanostructured Na3V2(PO4)3/C/TiO2 composite nanofibers as a stable anode for sodium-ion batteries

Abstract Na 3 V 2 (PO 4 ) 3 /C/TiO 2 (NVP/C/TiO 2 ) composite nanofibers with core/shell nanostructure are prepared by coaxial electrospinning plus heat treatment method. The physical and electrochemical performances of NVP/C/TiO 2 nanofibers are investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and electrochemical tests. The results show that the composite nanofibers are made of TiO 2 /C nanoparticles shell and Na 3 V 2 (PO 4 ) 3 /C nanofibers core with embedded TiO 2 /C nanoparticles. NVP/C/TiO 2 nanofibers exhibite much better electrochemical performance than both TiO 2 /C and Na 3 V 2 (PO 4 ) 3 /C nanofibers prepared by coaxial electrospinning method. The core-shelled NVP/C/TiO 2 nanofibers delivere a reversible capacity of 196.1 mAh g −1 at 0.2C (35.6 mA g −1 ) in the voltage of 0.01–3.0 V ( vs .Na + /Na), which is higher than the theoretical capacity of 178 mAh g −1 for Na 3 V 2 (PO 4 ) 3 and that of TiO 2 /C composite. NVP/C/TiO 2 also displays excellent cycle stability and rate capability. Even at a high rate of 20C, it can still release a high reversible charge capacity of 109 mAh g −1 and retain a capacity of more than 70 mAh g −1 after 1500 cycles. The special microstructure and synergetic effects of Na 3 V 2 (PO 4 ) 3 , conductive carbon and ultrafine TiO 2 are responsible for the excellent electrochemical performance. This facile strategy exhibits superiority in fabricating core-shell nanostructured composite nanofibers as promising electrode materials for energy storage devices.