Graphical abstract

Obtaining V2(PO4)3 by sodium extraction from single-phase NaxV2(PO4)3 (1 < x < 3) positive electrode materials

S. Park, Z. Wang, K. Choudhary, J.-N. Chotard, D. Carlier, F. Fauth, P. Canepa, L. Croguennec, and C. Masquelier; Nat. Mater. 24, 234 (2025).

BibTeX 
@article{Park2025obtaining,
  author  = {Park, S. and Wang, Z. and Choudhary, K. and Chotard, J.-N. and Carlier, D. and Fauth, F. and Canepa, P. and Croguennec, L. and Masquelier, C.},
  title   = {{Obtaining V$_{2}$(PO$_{4}$)$_{3}$ by sodium extraction from single-phase Na$_{x}$V$_{2}$(PO$_{4}$)$_{3}$ (1 < x < 3) positive electrode materials}},
  journal = {Nature Materials},
  volume  = {24},
  pages   = {234},
  year    = {2025},
  doi     = {10.1038/s41563-024-02023-7}
}
PDF
2025-01-30-park-nat-mater-2025.pdf
DOI
10.1038/s41563-024-02023-7

Abstract

We report on single-phase NaxV2(PO4)3 compositions (1.5 ⋜ x ⋜ 2.5) of the Na super ionic conductor type, obtained from a straightforward synthesis route. Typically, chemically prepared c-Na2V2(PO4)3, obtained by annealing an equimolar mixture of Na3V2(PO4)3 and NaV2(PO4)3, exhibits a specific sodium-ion distribution (occupancy of the Na(1) site of only 0.66(4)), whereas that of the electrochemically obtained e-Na2V2(PO4)3 (from Na3V2(PO4)3) is close to 1. Unlike conventional Na3V2(PO4)3, when used as positive electrode materials in Na-ion batteries, the NaxV2(PO4)3 compositions lead to unusual single-phase Na+ extraction/insertion mechanisms with continuous voltage changes upon Na+ extraction/insertion. We demonstrate that the average equilibrium operating voltage observed upon Na+ deintercalation from single-phase Na2V2(PO4)3 is increased up to an average value of ~3.70 V versus Na+/Na (thanks to the activation of the V4+/V5+ redox couple) compared to 3.37 V versus Na+/Na in conventional Na3V2(PO4)3, thus leading to an increase in the theoretical energy density from 396.3 Wh kg−1 to 458.1 Wh kg−1. Electrochemical and chemical Na+ deintercalation from c-Na2V2(PO4)3 enables complete Na-ion extraction, increasing energy density.