Electrospun Na₃V₂(PO₄)₃/C nanofibers as self-standing cathode material for high performance sodium ion batteries

Abstract

This work focuses on the preparation of a 3D flexible Na 3 V 2 (PO 4 ) 3 /C fiber membrane, as selfstanding cathode for Na-ion batteries, via a facile and simple electrospinning method, is followed by a hot-pressing process. A series of heat treatment temperatures are studied in detail, it is found that the temperature of the thermal process is a key parameter for controlling the structural organization of the material, as well as the size and dispersion of Na 3 V 2 (PO 4 ) 3 nanoparticles on the carbon surface. Hence, Na 3 V 2 (PO 4 ) 3 nanoparticles, with a size of 40 nm and highly disperse on the carbon nanofibers, are obtained after calcination at 800°C. In addition, this sample (Na 3 V 2 (PO 4 ) 3 /C Nanofiber-800) exhibits the best electrochemical performances among all the samples. For instance, it displays a considerably high initial discharge capacity of 109, 84, 77, and 71 mA h g −1 at a current density of 0.1, 10, 20, and 30 C, respectively. Moreover, the Na 3 V 2 (PO 4 ) 3 /C Nanofiber-800 shows notable cycle stability with about 95.3% capacity retention of its initial capacity after 1000 cycles at 2 C, These high performances is attributed to the unique nanofiber structure and uniform distribution of Na 3 V 2 (PO 4 ) 3 nanoparticles in the highly conductive carbon matrix.

Mn-Doped Na4Fe3(PO4)2P2O7 as a Low-Cost and High-Performance Cathode Material for Sodium-Ion Batteries

“…Figure b shows the linear relationship between Z ’ and ω –1/2 , and the equation in the figure represents its linear relationship equation. In addition, D Na+ can be obtained by the following equation , D normalN normala + = R 2 T 2 2 A 2 n 4 F 4 C 2 σ 2 Z ′ = R normale + R ct + σ ω − 1 / 2 where D Na+ represents the sodium-ion diffusion coefficient, R represents the gas constant, T is the room temperature Kelvin temperature, A represents the area of the pole piece (15 mm diameter), n represents the number of electrons transferred during the reaction, F represents the Faraday constant, C represents the sodium-ion bulk phase concentration, and σ is the Warburg factor (slope of the curve in Figure b).…”

“…Figure 6b shows the linear relationship between Z' and ω −1/2 , and the equation in the figure represents its linear relationship equation. In addition, D Na+ can be obtained by the following equation 43,44 (3)…”

Unraveling the modified regulation of ternary substitution on Na3V2(PO4)3 for sodium ion batteries

“…It possesses a high energetic density of 400 W h kg À1 , and a long and stable voltage platform at 3.4 V. Most importantly, it dominates a controllable Na superionic conductor (NASICON)-type system to establish benecial channels for ionic transformation. [17][18][19][20][21][22][23][24] The NASICON-type structure contains V 2 (PO 4 ) 3 framework repeating units in which octahedral VO 6 interlinks via corners with tetrahedral PO 4 . In this unique construction, Na + locate at the 6b, M1 site and 18e, M2 site respectively.…”

N-Doped Carbon-Layer-Modified Na3V2(PO4)3 as a High-Performance Cathode Material for Sodium-Ion Batteries

“…The lower interface impedance of NVP/NC implies that the defect structure introduced by the N-doped carbon layer accelerates the electron transport. In addition, the Na + diffusion coefficient of NVP/C and NVP/NC electrodes can be calculated by the following equations: , wherein R stands for the ideal gas constant, T is the thermodynamic temperature, A represents the electrode area, n is the number of electrons transferred in the oxidation process, F means the Faraday constant, C denotes the bulk concentration of Na + , and σ is the Warburg impedance factor derived from eq . Figure b illustrates the linear relationship between Z re and ω –1/2 .…”

“…The lower interface impedance of NVP/NC implies that the defect structure introduced by the N-doped carbon layer accelerates the electron transport. In addition, the Na + diffusion coefficient of NVP/C and NVP/NC electrodes can be calculated by the following equations: 41,42…”