Three dimensional architecture of carbon wrapped multilayer Na₃V₂O₂(PO₄)₂F nanocubes embedded in graphene for improved sodium ion batteries

Abstract

A novel Na3V2O2(PO4)2F@carbon/graphene three dimensional (3D)architecture (NVPF@C/G) is developed through a simple approach for the first time, which demonstrates superior sodiation properties for Na-ion batteries.

Rapid microwave-assisted refluxing synthesis of hierarchical mulberry-shaped Na3V2(PO4)2O2F@C as high performance cathode for sodium & lithium-ion batteries

“…3f) shows two characteristic peaks with binding energy of 516.7 eV (V 2p 3/2 ) and 523.8 eV (V 2p 1/2 ), indicating the existence of V 4+ species in NVPF@C samples. This is consistent with previous reports [21,33]. Moreover, the highresolution of C 1s spectrum in Fig.…”

The rapid microwave-assisted hydrothermal synthesis of NASICON-structured Na3V2O2x(PO4)2F3−2x(0 <x≤ 1) cathode materials for Na-ion batteries

“…These unit cell parameters were typical of Na 3 V 2 O 2 (PO 4 ) 2 F with the NASICON-type structure. 6,13,16,26,27 Nevertheless, other studies have reported the primitive a P ¼ a I O2, c P ¼ c I tetragonal supercell for Na 3 5,12,15 and a more systematic crystallographic investigation revealed that the primitive supercell was indeed stable at room temperature, while the smaller I-centered tetragonal subcell was characteristic of the high-temperature polymorph of Na 3 V 2 O 2 (PO 4 ) 2 F (stable above $500 K). 28 To verify the unit cell of the Na 3 V 2 O 2 (PO 4 ) 2 F phase prepared by the MW-HT method, we performed electron diffraction analysis.…”

“…For example, using Na 2 HPO 4 as a phosphorus source results in the formation of nanoowers with a diameter of 8 mm and thickness of 4 mm, while using NH 4 H 2 PO 4 leads to a cube-like morphology and particles with sizes less than 1 mm. 14,27 However, treatment time is a limiting parameter of hydrothermal synthesis, with up to 60 h perhaps required to afford the nal product. 13 The long synthesis duration is closely related with the requirement to heat the solution homogeneously, while heating occurs from the "outside" to "inside".…”

Ultra‐long cycle life and high rate performance subglobose Na 3 V 2 ( PO 4 ) 2 F 3 @C cathode and its regulation

“…As can be seen from Figure 3A, peaks at 517.5 eV and 524.6 eV are attributed to the V 2p 3/2 and V 2p 1/2 , indicating trivalent vanadium in NVPF@C‐4 is successfully reduced from V 2 O 5 . Also, the C 1s peak at 284.5 eV in NVPF@C‐4 (Figure 3B) are fitted to four peaks at 284.6 eV, 285.5 eV, 286.6 eV and 288.9 eV, which are assigned to the C=C, C−C, C−N and O−C=O bonds, respectively 18,23 . The absorption peak at 400.9 eV is belonging to N 1s, which is originated from the decomposition of CTAB.…”

“…Like most polyanion cathode materials, Na 3 V 2 (PO 4 ) 2 F 3 also suffers from poor electronic conductivity (10 −12 S·cm −1 ) because tetrahedron [PO 4 ] separates vanadium atoms. In order to improve the electrochemical performance of Na 3 V 2 (PO 4 ) 2 F 3 , controlling the particle size, carbon coating, and metallic ion doping are three major means 16‐18 …”