MORTEMARD DE BOISSE, Benoit; CARLIER, Dany; GUIGNARD, Marie; GUÉRIN, Elodie; DUTTINE, Mathieu; WATTIAUX, Alain; DELMAS, Claude

doi:10.1021/acs.chemmater.8b02953

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MORTEMARD DE BOISSE, Benoit
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

CARLIER, Dany
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

GUIGNARD, Marie
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

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Chemistry of Materials. 2018, vol. 30, n° 21, p. 7672-7681

American Chemical Society

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The comparative structural, Mössbauer, and electrochemical studies of the NaxMn2/3Fe1/3O2 and NaxMn1/2Fe1/2O2 systems show that the change in the Mn/Fe ratio has a significant influence on the overlap between the Mn3+/4+ and Fe3+/4+ redox couples. The P2-type structure is maintained in the 0.3 < x < 0.8 domain. For the highest intercalation amount, structural distortions occur due to the Jahn–Teller effect of the Mn3+ ions. The macroscopic distortion results from a competition between the opposite effects of Mn3+ and Fe3+: the isotropic character of Fe3+ tends to prevent the macroscopic distortion. For the lower sodium amounts, the instability of the interstitial trigonal prismatic space leads to the formation, by slab gliding, of a very disordered structure. Even if this structural transition is reversible, a strong capacity fading is observed if the cell is charged above 4 V verus Na/Na+.< Réduire

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Influence of Mn/Fe ratio on electrochemical and structural properties of P2-NaxMn1–yFeyO2 phases as positive electrode material for Na-Ion batteries

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