Mastering the synergy between Na3V2(PO4)2F3 electrode and electrolyte: A must for Na-ion cells

Desai, Parth Rakesh; Forero-Saboya, Juan; Meunier, Valentin; Rousse, Gwenaëlle; Deschamps, Michaël; Abakumov, Artem M.; Tarascon, Jean‐Marie; Mariyappan, Sathiya

doi:10.1016/j.ensm.2023.02.004

Cited by 28 publications

(28 citation statements)

References 42 publications

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“…This latter extra phase, present in very small amount, could be obtained as a byproduct due to a reaction between NVPF and the electrolyte. This observation is in rather good agreement with the recent work of Mariyappan et al, which demonstrates that vanadium dissolution in Na + deintercalated NVPF is favored in a NaPF 6 based electrolyte containing controlled traces of H 2 O and at moderated temperature . The cell parameters of both pristine and discharged NVPF/C materials remain unchanged after DSC suggesting that the main phase is rather thermally stable, and most probably, only the surface reacts with the electrolyte/binder to form byproducts.…”

Section: Resultssupporting

confidence: 91%

“…This observation is in rather good agreement with the recent work of Mariyappan et al, which demonstrates that vanadium dissolution in Na + deintercalated NVPF is favored in a NaPF 6 based electrolyte containing controlled traces of H 2 O and at moderated temperature. 47 The cell parameters of both pristine and discharged NVPF/C materials remain unchanged after DSC suggesting that the main phase is rather thermally stable, and most probably, only the surface reacts with the electrolyte/ binder to form byproducts. 31 P NMR and 23 Na NMR spectra confirm that both phosphorus and sodium environments within the NVPF-type phase barely evolved: a single 31 P signal is observed at 6000 ppm, and the 23 Na signal evolves from 138 Na2-Charged NVPF/C.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

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Thermal Stability of Na_3–xV₂(PO₄)₂F_3–yO_y: Influence of F^– for O^2– Substitution and Degradation Mechanisms

et al. 2023

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The Na-ion battery technology appears as a reliable, sustainable, and environmentally friendly alternative to the Li-ion one, especially for stationary energy storage. As for the Li-ion technology, the safety aspect is of high importance to ensure largescale development. In this work, we studied the thermal stability and decomposition mechanisms of carbon-coated Na 3 V 2 (PO 4 ) 2 F 3 and two fluorine-rich phases belonging to the solid-solution Na 3 V 3+ 2−y V 4+ y (PO 4 ) 2 F 3−y O y (y = 0.07 and y = 0.12), that family of compounds being often considered among the most promising positive electrode materials for Na-ion batteries. This study shows the good thermal stability of these polyanionic materials and reveals that a low O 2− for F − substitution has a very limited effect on the thermal stability of fully reintercalated materials recovered in the discharged state of the battery, whereas it has a beneficial impact for highly deintercalated ones, obtained by in-depth charges. Furthermore, whatever the state of charge and the oxygen content in Na x V 2 (PO 4 ) 2 F 3−y O y (1 ≤ x ≤ 3 and y = 0, 0.07 and 0.12), the thermal degradation leads, quite unexpectedly, to the formation of crystalline Na 3 V 3+ 2 (PO 4 ) 2 F 3 in addition to an amorphous phase. The fluorination of the partial oxygen for fluorine substituted material was clearly demonstrated by X-ray diffraction (XRD) and solid state nuclear magnetic resonance spectroscopy (NMR) on materials recovered after differential scanning calorimetry (DSC) analyses. The formation of a fully sodiated crystalline phase from the thermal degradation of the material obtained in charged states of the battery, with or without the presence of electrolyte, was never reported before.

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Section: Resultssupporting

confidence: 91%

Section: ■ Results and Discussionmentioning

confidence: 98%

Thermal Stability of Na_3–xV₂(PO₄)₂F_3–yO_y: Influence of F^– for O^2– Substitution and Degradation Mechanisms

et al. 2023

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“…This observation is in rather good agreement with the recent work of Mariyappan et al, which demonstrates that vanadium dissolution in Na + de-intercalated NVPF is favoured in NaPF6 based electrolyte containing controlled traces of H2O and at moderated temperature. 46 The cells parameters of both pristine and discharged NVPF/C materials remain unchanged after DSC suggesting that the main phase is rather thermally stable and, most probably, only the surface reacts with the electrolyte/binder to form by-products. 31 P NMR and 23 Na NMR spectra confirm that both phosphorus and sodium environments within the NVPF-type phase barely evolved: a single 31 P signal is observed at 6000 ppm, and the 23 Na signal evolves from 138 ppm for the pristine material to 127 ppm for the discharged one (figures 5b and 5c).…”

Section: Variations In the Degradation Mechanisms For Nvpf/cmentioning

confidence: 97%

Thermal stability of Na3-xV2(PO4)2F3-yOy: influence of F- for O2- substitution and degradation mechanisms

Pablos

Olchowka

Petit

et al. 2023

Preprint

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The Na-ion battery technology appears as a reliable, sustainable and environmentally friendly alternative to the Li-ion one, especially for stationary energy storage. As for the Li-ion technology, safety aspect is of high importance to ensure large-scale development. In this work, we studied the thermal stability and decomposition mechanisms of carbon-coated Na3V2(PO4)2F3 and two fluorine-rich phases belonging to the solid-solution Na3V3+2-yV4+y(PO4)2F3-yOy (y = 0.07 and y = 0.12), that family of compounds being often considered among the most promising positive electrode materials for Na-ion batteries. This study shows the good thermal stability of these polyanionic materials and reveals that a low O2- for F- substitution has a very limited effect on the thermal stability of fully re-intercalated materials recovered in the discharged state of the battery, whereas it has a beneficial impact for highly de-intercalated ones, obtained by in-depth charges. Furthermore, whatever the state of charge and the oxygen content in NaxV2(PO4)2F3-yOy (1<=x<=3 and y = 0, 0.07 and 0.12), the thermal degradation leads, quite unexpectedly, to the formation of crystalline Na3V3+2(PO4)2F3 in addition to an amorphous phase. The fluorination of the partially oxygen for fluorine substituted material was clearly demonstrated by X-ray diffraction (XRD) and solid state nuclear magnetic resonance spectroscopy (NMR) on materials recovered after differential scanning calorimetry (DSC) analyses. The formation of a fully sodiated crystalline phase from the thermal degradation of the material obtained in charged states of the battery, with or without presence of electrolyte, was never reported before.

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“…For instance, "soft-solvating" electrolytes, as proposed by Wang et al, [34] could be considered to overcome the rate-limiting desolvation process in NVP's case and lower the concentration-driven polarization. On the other hand, NVPF would benefit from a more stable CEI to prevent capacity fade related to vanadium dissolution [35] issues by incorporating electrolytes that would favor the formation of an inorganic CEI such as Localized High Concentration Electrolytes (LHCE). [36,37] In conclusion, the desolvation process during the insertion of Na + in the NVP framework was captured thanks to EQCM and operando IR-FEWS measurements and confirmed by MD simulations.…”

Section: Discussionmentioning

confidence: 99%

Spotting Interface Structuring during Na‐Insertion into the NaSICON Na₃V₂(PO₄)₃ by EQCM and Operando Fiber Optic Infrared Spectroscopy

Bendadesse

Gervillié-Mouravieff

Leau

et al. 2023

Advanced Energy Materials

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Reliable operation of Na-ion batteries requires a mastering of the interfacial processes governing intercalation kinetics. Ion desolvation, amongst others, is a crucial phenomenon as far as power applications are envisioned. Studying the intricacies of interfacial processes faces experimental challenges. Here the complementary use of electrochemical quartz crystal microbalance (EQCM) and operando infrared fiber evanescent wave spectroscopy (IR-FEWS) combined with molecular dynamics (MD) simulations is reported to investigate the electrode/electrolyte interface of polyanionic Na-insertion compounds Na 3 V 2 (PO 4 ) 3 (NVP) and Na 3 V 2 (PO 4 ) 2 F 3 (NVPF). Through screening of various electrolytes that differ in their solvation energy and viscosity, the existence of an unusual mass uptake/depletion signal is demonstrated at the NVP interfaces only, indicative of a dissimilarity in migration kinetics of solvent molecules between NVP and NVPF interfaces as supported by IR-FEWS. This finding is rationalized by positing that sodium depletion is caused by the unusually rapid ion diffusion within NVP mediated by an intermediate metastable phase, which leads to opposite Na + concentration and free solvent molecule gradients at the interface that causes the unusual and anomalous feature observed on EQCM frequency profiles. This feature does not appear with NVPF showing lower ionic diffusion. Altogether, this fundamental study provides valuable fundamental insights into the interface structuring of insertion compounds depending upon their Na + mobility.

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Mastering the synergy between Na3V2(PO4)2F3 electrode and electrolyte: A must for Na-ion cells

Cited by 28 publications

References 42 publications

Thermal Stability of Na_3–xV₂(PO₄)₂F_3–yO_y: Influence of F^– for O^2– Substitution and Degradation Mechanisms

Thermal Stability of Na_3–xV₂(PO₄)₂F_3–yO_y: Influence of F^– for O^2– Substitution and Degradation Mechanisms

Thermal stability of Na3-xV2(PO4)2F3-yOy: influence of F- for O2- substitution and degradation mechanisms

Spotting Interface Structuring during Na‐Insertion into the NaSICON Na₃V₂(PO₄)₃ by EQCM and Operando Fiber Optic Infrared Spectroscopy

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Mastering the synergy between Na3V2(PO4)2F3 electrode and electrolyte: A must for Na-ion cells

Cited by 28 publications

References 42 publications

Thermal Stability of Na3–xV2(PO4)2F3–yOy: Influence of F– for O2– Substitution and Degradation Mechanisms

Thermal Stability of Na3–xV2(PO4)2F3–yOy: Influence of F– for O2– Substitution and Degradation Mechanisms

Thermal stability of Na3-xV2(PO4)2F3-yOy: influence of F- for O2- substitution and degradation mechanisms

Spotting Interface Structuring during Na‐Insertion into the NaSICON Na3V2(PO4)3 by EQCM and Operando Fiber Optic Infrared Spectroscopy

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Product

Resources

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Thermal Stability of Na_3–xV₂(PO₄)₂F_3–yO_y: Influence of F^– for O^2– Substitution and Degradation Mechanisms

Thermal Stability of Na_3–xV₂(PO₄)₂F_3–yO_y: Influence of F^– for O^2– Substitution and Degradation Mechanisms

Spotting Interface Structuring during Na‐Insertion into the NaSICON Na₃V₂(PO₄)₃ by EQCM and Operando Fiber Optic Infrared Spectroscopy