CTAB-Assisted Synthesis of C@Na3V2(PO4)2F3 With Optimized Morphology for Application as Cathode Material for Na-Ion Batteries

Abstract

C@Na3V2(PO4)2F3 samples were obtained by using Cetyl Trimethyl Ammonium Bromide (CTAB) as a surfactant. The optimization of the added amount allowed controlling the eventual nanometric morphology of the particles. The morphological and structural properties of these samples were discussed in the light of solid-state techniques as X-ray diffraction, Raman and XPS spectroscopies, and electron microscopy. Galvanostatic test in sodium half-cells revealed that the nanometric spherical and porous particles provided by the addition of intermediate amounts of CTAB showed excellent cycling stability and superior high rate capability reflected in the minimization of the cell polarization and the determination of a high apparent diffusion coefficient.

Delicately Tailored Ternary Phosphate Electrolyte Promotes Ultrastable Cycling of Na3V2(PO4)2F3-Based Sodium Metal Batteries

“…Strikingly, the cell using the 1 M NaTFSI-TEP/FEC (3:1) electrolyte demonstrates an extremely stable cycling performance at 0.5 C, achieving a remarkably high capacity retention of 97.9% over 300 cycles (117.1 mA h g –1 for the highest value in this course and 114.6 mA h g –1 for the 300th cycle) and a high ACE of 99.4% (Figure b), which are among the best ever reported for high-voltage Na 3 V 2 (PO 4 ) 2 F 3 cathode-based cells (Table S2). ,,,− In comparison, the cells can only operate for ∼150 cycles in the 1 M NaTFSI-FEC electrolyte with a capacity retention of 88.5% and an ACE of 95.5% (Figure c). Moreover, the Coulombic efficiency started to decrease after 60 cycles due to the ever-increasing charge capacity in the high-voltage region (see the marked region in Figures f and S10).…”

“…However, developing a high-performance electrolyte, compatible with both high-voltage cathodes and highly reactive sodium metal anodes, is extremely challenging. For example, an NASICON-structured Na 3 V 2 (PO 4 ) 2 F 3 cathode has drawn tremendous attention in recent years due to its high working potential (∼4 V vs Na + /Na) and high energy density (∼500 W h kg –1 ). − However, reports on the stable cycling of Na 3 V 2 (PO 4 ) 2 F 3 cathodes in traditional carbonate electrolytes are still challenging and rare. ,− As for sodium metal anodes, their utilization in traditional carbonate electrolytes is also largely restricted due to the poor round-trip Coulombic efficiency and the growth of dendrites during cell operation, which will lead to rapid electrolyte consumption and, eventually, the cell’s internal short circuit. − Alternatively, although ether electrolytes are known to be more compatible with sodium metal anodes, − they suffer from poor anodic stability, making them irrelevant for high-voltage batteries. , Moreover, both carbonate and ether electrolytes are highly flammable, which may cause a severe safety hazard.…”

Defective Titanium Dioxide-supported Ultrasmall Au Clusters for Photocatalytic Hydrogen Production

“…Figure 3C were not obvious differences. The Au 4f of Au/D-TiO 2 (treated at 150°C) core-level XPS spectrum displayed one special peak at 83.9 eV in Figure 3D, and this peak could be attributed to Au clusters [26,27]. The measurements of UV-visible diffuse-reflectance spectrum (UV-vis DRS) were carried out to investigate the light absorption intensity.…”

Dually Decorated Na3V2(PO4)2F3 by Carbon and 3D Graphene as Cathode Material for Sodium‐Ion Batteries with High Energy and Power Densities

“…However, the rate capability and cyclability of Na 3 V 2 (PO 4 ) 2 F 3 are significantly restricted by its low electronic conductivity. The previous reports proved that electrochemical performance of Na 3 V 2 (PO 4 ) 2 F 3 was substantially enhanced by synthesis of composites of Na 3 V 2 (PO 4 ) 2 F 3 and carbonaceous materials, and this improvement is mainly ascribed to the introduction of carbonaceous substances with high electronic conductivity and hence the increase of electronic conductivity of composites. Within these composites, the dually modified composites such as Na 3 V 2 (PO 4 ) 2 F 3 @C/CNTs, double‐shelled carbon coated Na 3 V 2 (PO 4 ) 2 F 3 @C, Na 3 V 2 (PO 4 ) 2 F 3 @C/mesoporous carbon matrix and Na 3 V 2 (PO 4 ) 2 F 3 /C@rGO have much better electrochemical performance, especially rate performance, suggesting that electronic conductivity and microstructure of surface modifiers are important factors to influence the electrochemical performance of electroactive Na 3 V 2 (PO 4 ) 2 F 3 .…”