Aluminum substitution for vanadium in the Na₃V₂(PO₄)₂F₃ and Na₃V₂(PO₄)₂FO₂ type materials

Abstract

Investigation of the effects of Al substitution for V on the structural properties and electrochemical performances for two of the most promising positive electrode materials for Na-ion batteries, Na3V2(PO4)2F3 and Na3V2(PO4)2FO2.

Density Functional Theory-Assisted 31P and 23Na Magic-Angle Spinning Nuclear Magnetic Resonance Study of the Na3V2(PO4)2F3–Na3V2(PO4)2FO2 Solid Solution: Unraveling Its Local and Electronic Structures

“…2-y'V 4+ y'(PO4)2F3-y'Oy' (0 ≤ y' ≤ 2.0) compositions are given in Figure S1. An Al-substituted phase, Na3V1.5Al0.5(PO4)2F3, was obtained by a sol-gel synthesis method as reported in 32 . Density Functional Theory Calculations.…”

“…14 In order to further confirm the absence of spin transfer from V 4+ ions to the phosphorus nuclei in the Na3V2(PO4)2F3 -Na3V2(PO4)2FO2 system, we chose to compare these results with those obtained for the partially aluminum-substituted composition Na3V1.5Al0.5(PO4)2F3, recently reported by our group. 32 Al 3+ ions are diamagnetic, which are not able to cause any Fermi contact with the neighboring P nuclei in the structure. In Na3V1.5Al0.5(PO4)2F3…”

Ionothermal Synthesis of Polyanionic Electrode Material Na3V2(PO4)2FO2 through a Topotactic Reaction

“…9 Furthermore, oxygen substitution also enhances the Na + diffusivity within the diffusion channels and stabilizes the structure, especially at the overcharged states, [9][10][11] making these oxygen-substituted compositions interesting for practical applications. 4,8 In recent years, several synthetic approaches such as sol-gel, 12,13 solvothermal, [14][15][16][17][18] ball-milling, 19,20 spark plasma sintering, 21 and spray drying 22 have been developed to optimize the carbon-coating layer, the morphology, and the particle size of Na 3 V 3+ 2-y V 4+ y (PO 4 ) 2 F 3-y O y . The as-obtained materials crystallize in the form of hollow microspheres, nano or microcubes, spherical nanoparticles, 3D array, or nano-flower morphologies, which often exhibit outstanding performance at high cycling rates due to an enhanced electrode-electrolyte interface allowing a better ionic diffusion process.…”

Monitoring the Crystal Structure and the Electrochemical Properties of Na3(VO)2(PO4)2F through Fe3+ Substitution

“…21 Furthermore, the capacity loss observed in these compounds was considered as a detrimental effect of Al-substitution for V since only the V 4+ /V 3+ redox couple can be activated in the electrochemical window of all the currently available electrolytes. 25,26 A decrease in the charge transfer resistance and an improvement in the capacity retention were reported when Na3V2(PO4)2F3 was doped with yttrium or manganese ions. 27,28 Nonetheless, there is no report on the effects of cationic substitution on the electrochemical performance of Na3(VO)2(PO4)2F that can be found in the literature.…”