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# First 18650-format Na-ion cells aging investigation: A degradation mechanism study

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Abstract : Several Hard carbon||Na$_3$V$_2$(PO$_4$)$_2$F$_3$ full-cells in 18650-format are assembled to demonstrate the possible use of SIBs in stationary applications. The cell aging process is investigated in two different conditions: (i) continuous cycling at different current rates, and (ii) storage at different states-of-charge at various temperatures. The obtained results reveal that the cell degradation depends strongly on the temperature, current rates applied in cycling conditions, or state-of-charge of the storage test. Under cycling conditions, the continuous sodiation/desodiation may induce significant mechanical deformation, leading to the detachment of active materials from the current collector. Furthermore, the post-mortem analysis shows that reaction rate and aging process are not homogeneous along the electrode roll. The XRD analysis shows that Na$_3$V$_2$(PO$_4$)$_2$F$_3$ structure is robust; nevertheless, the material cannot recover the initial Na$^+$ content as the cycling progresses, which is the main cause for capacity loss in the positive electrode. The solid-electrolyte interphase present on the hard carbon surface was characterised using XPS. The hard carbon electrode cannot be detected during this study, evidencing the formation of a relatively thick (>5 nm) passivating layer composed of carbonate salts and NaF, which are the main products of electrolyte decomposition.
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Journal articles
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https://hal-univ-pau.archives-ouvertes.fr/hal-03607692
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Submitted on : Thursday, March 17, 2022 - 11:21:05 AM
Last modification on : Wednesday, April 27, 2022 - 4:59:51 AM

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### Citation

Long H. B. Nguyen, Paula Sanz Camacho, Jérémie Fondard, Dany Carlier, Laurence Croguennec, et al.. First 18650-format Na-ion cells aging investigation: A degradation mechanism study. Journal of Power Sources, Elsevier, 2022, 529, pp.231253. ⟨10.1016/j.jpowsour.2022.231253⟩. ⟨hal-03607692⟩

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