Study of the insertion/deinsertion mechanism of sodium into Na0.44MnO2.
Pure Na0.44MnO2 samples were prepared via a solid-state route by carefully tuning the synthesis conditions. Insertion/deinsertion of sodium into the well-crystallized particles leads to capacities as high as 140 mA.h/g. A potentiostatic intermittent titration technic, together with in situ X-ray diffraction measurements, enabled us to evidence the presence of six biphasic transitions within a potential range of 2-3.8 V (vs Na+/Na). The insertion process within the NaxMnO2 system is fully reversible over the 0.25 < x < 0.65 composition range and presents some degree of irreversibility as values of x below 0.25 are reached. Furthermore, we similarly showed that HCl treatment has a detrimental effect on these electrochemical properties because of structural and textural evolutions.
Sauvage
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Laboratoire de Réactivité et Chimie des Solides, UMR CNRS 6007, Université de Picardie Jules Verne, 33 rue St. Leu, 80039 Amiens CEDEX France.
Laffont
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Tarascon
J-M
JM
Baudrin
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