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

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.

Author:

Sunkyu Park (1,2,3), Ziliang Wang (4,5), Kriti Choudhary (1), Jean-Noel Chotard (1,6), Dany Carlier (2,6), Franois Fauth (7), Pieremanuele Canepa (4,8,9), Laurence Croguennec (2,6) & Christian Masquelier (1,6,10)

Affiiation

(1) Laboratoire de Réactivité et de Chimie des Solides, Université de Picardie Jules Verne, CNRS, Amiens, France.

(2) Institut de Chimie de la Mati.re Condens.e de Bordeaux (ICMCB), Universit. de Bordeaux, Bordeaux INP, CNRS, Pessac, France.

(3) TIAMAT, Amiens, France.

(4) Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore.

(5) Department of Materials Science and Engineering, North western University, Evanston, IL, USA.

(6) Réseau Français sur le Stockage Electrochimique de l’Energie (RS2E), CNRS, Amiens, France.

(7) ALBA Synchrotron, Consortium for the Exploitation of the Synchrotron Light Laboratory (CELLS), Cerdanyola del Vallès, Spain.

(8) Chemical and Biomolecular Engineering, National University of Singapore, Singapore, Singapore.

(9) Department of Electrical and Computer Engineering, University of Houston, Houston, TX, USA.

(10) Institut Universitaire de France, Paris, France.

External Link:

External Link

Source:

Nature Materials, volume 24, pages 234–242 (2025)

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