Phase-pure Na3V2(PO4)2F3 embedded in carbon matrix through a facile polyol synthesis as a potential cathode for high performance sodium-ion batteries
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In this study, a pseudo-layered Na super-ionic conductor of Na3V2(PO4)2F3 (NVPF)/C cathode for sodium-ion batteries is prepared successfully using a facile polyol refluxing process without any impurity phases. The X-ray diffraction and Rietveld refinement results confirm that NVPF possesses tetragonal NASICON-type lattice with a space group of P42/mnm. In this preparative method, polyol is utilized as a solvent as well as a carbon source. The presence of nanosized NVPF particles in the carbon network is confirmed by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The existence of carbon is analyzed by Raman scattering and elemental analysis. When applied as a Na-storage material in a potential window of 2.0–4.3 V, the electrode exhibits two flat voltage plateaus at 3.7 and 4.2 V with an electrochemically active V3+/V4+ redox couple. In addition, Na3V2(PO4)2F3/C composite achieved a retention capacity of ~ 88% even after 1,500 cycles at 15 C. Moreover, at high current densities of 30 and 50 C, Na3V2(PO4)2F3/C cathode retains the specific discharge capacities of 108.4 and 105.9 mAh·g–1, respectively, revealing the structural stability of the material prepared through a facile polyol refluxing method.
Keywordsfluorophosphate Na3V2(PO4)2F3 polyol process sodium ion batteries long life stability
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This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2017R1A2A1A17069397). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2018R1A5A1025224).
- Liu, Q.; Wang, D. X.; Yang, X.; Chen, N.; Wang, C. Z.; Bie, X. F.; Wei, Y. J.; Chen, G.; Du, F. Carbon-coated Na3V2(PO4)2F3 nanoparticles embedded in a mesoporous carbon matrix as a potential cathode material for sodium-ion batteries with superior rate capability and long-term cycle life. J. Mater. Chem. A 2015, 3, 21478–21485.CrossRefGoogle Scholar